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GCC(1)                                GNU                               GCC(1)



NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-pedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the remainder.  g++
       accepts mostly the same options as gcc.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation, assembly and
       linking.  The "overall options" allow you to stop this process at an intermediate
       stage.  For example, the -c option says not to run the linker.  Then the output
       consists of object files output by the assembler.

       Other options are passed on to one stage of processing.  Some options control the
       preprocessor and others the compiler itself.  Yet other options control the
       assembler and linker; most of these are not documented here, since you rarely need
       to use any of them.

       Most of the command line options that you can use with GCC are useful for C
       programs; when an option is only useful with another language (usually C++), the
       explanation says so explicitly.  If the description for a particular option does
       not mention a source language, you can use that option with all supported
       languages.

       The gcc program accepts options and file names as operands.  Many options have
       multi-letter names; therefore multiple single-letter options may not be grouped:
       -dv is very different from -d -v.

       You can mix options and other arguments.  For the most part, the order you use
       doesn't matter.  Order does matter when you use several options of the same kind;
       for example, if you specify -L more than once, the directories are searched in the
       order specified.  Also, the placement of the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both positive and
       negative forms; the negative form of -ffoo would be -fno-foo.  This manual
       documents only one of these two forms, whichever one is not the default.

OPTIONS
   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations are in the
       following sections.

       Overall Options
           -c  -S  -E  -o file  -combine  -pipe  -pass-exit-codes -x language  -v  -###
           --help[=class[,...]]  --target-help --version -wrapper@file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline -aux-info filename -fno-asm  -fno-builtin
           -fno-builtin-function -fhosted  -ffreestanding -fopenmp -fms-extensions
           -trigraphs  -no-integrated-cpp  -traditional  -traditional-cpp
           -fallow-single-precision  -fcond-mismatch -flax-vector-conversions
           -fsigned-bitfields  -fsigned-char -funsigned-bitfields  -funsigned-char

       C++ Language Options
           -fabi-version=n  -fno-access-control  -fcheck-new -fconserve-space
           -ffriend-injection -fno-elide-constructors -fno-enforce-eh-specs -ffor-scope
           -fno-for-scope  -fno-gnu-keywords -fno-implicit-templates
           -fno-implicit-inline-templates -fno-implement-inlines  -fms-extensions
           -fno-nonansi-builtins  -fno-operator-names -fno-optional-diags  -fpermissive
           -frepo  -fno-rtti  -fstats  -ftemplate-depth-n -fno-threadsafe-statics
           -fuse-cxa-atexit  -fno-weak  -nostdinc++ -fno-default-inline
           -fvisibility-inlines-hidden -fvisibility-ms-compat -Wabi  -Wctor-dtor-privacy
           -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wstrict-null-sentinel
           -Wno-non-template-friend  -Wold-style-cast -Woverloaded-virtual
           -Wno-pmf-conversions -Wsign-promo

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
           -fno-nil-receivers -fobjc-call-cxx-cdtors -fobjc-direct-dispatch
           -fobjc-exceptions -fobjc-gc -freplace-objc-classes -fzero-link -gen-decls
           -Wassign-intercept -Wno-protocol  -Wselector -Wstrict-selector-match
           -Wundeclared-selector

       Language Independent Options
           -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
           -fdiagnostics-show-option

       Warning Options
           -fsyntax-only  -pedantic  -pedantic-errors -w  -Wextra  -Wall  -Waddress
           -Waggregate-return  -Warray-bounds -Wno-attributes -Wno-builtin-macro-redefined
           -Wc++-compat -Wc++0x-compat -Wcast-align  -Wcast-qual -Wchar-subscripts
           -Wclobbered  -Wcomment -Wconversion  -Wcoverage-mismatch  -Wno-deprecated
           -Wno-deprecated-declarations -Wdisabled-optimization -Wno-div-by-zero
           -Wempty-body  -Wenum-compare -Wno-endif-labels -Werror  -Werror=*
           -Wfatal-errors  -Wfloat-equal  -Wformat  -Wformat=2 -Wno-format-contains-nul
           -Wno-format-extra-args -Wformat-nonliteral -Wformat-security  -Wformat-y2k
           -Wframe-larger-than=len -Wignored-qualifiers -Wimplicit
           -Wimplicit-function-declaration  -Wimplicit-int -Winit-self  -Winline
           -Wno-int-to-pointer-cast -Wno-invalid-offsetof -Winvalid-pch -Wlarger-than=len
           -Wunsafe-loop-optimizations -Wlogical-op -Wlong-long -Wmain  -Wmissing-braces
           -Wmissing-field-initializers -Wmissing-format-attribute  -Wmissing-include-dirs
           -Wmissing-noreturn  -Wno-mudflap -Wno-multichar  -Wnonnull  -Wno-overflow
           -Woverlength-strings  -Wpacked  -Wpacked-bitfield-compat  -Wpadded
           -Wparentheses  -Wpedantic-ms-format -Wno-pedantic-ms-format -Wpointer-arith
           -Wno-pointer-to-int-cast -Wredundant-decls -Wreturn-type  -Wsequence-point
           -Wshadow -Wsign-compare  -Wsign-conversion  -Wstack-protector -Wstrict-aliasing
           -Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=n -Wswitch
           -Wswitch-default  -Wswitch-enum -Wsync-nand -Wsystem-headers  -Wtrigraphs
           -Wtype-limits  -Wundef  -Wuninitialized -Wunknown-pragmas  -Wno-pragmas
           -Wunreachable-code -Wunused  -Wunused-function  -Wunused-label
           -Wunused-parameter -Wunused-value  -Wunused-variable -Wunused-but-set-parameter
           -Wunused-but-set-variable -Wvariadic-macros -Wvla -Wvolatile-register-var
           -Wwrite-strings

       C and Objective-C-only Warning Options
           -Wbad-function-cast  -Wmissing-declarations -Wmissing-parameter-type
           -Wmissing-prototypes  -Wnested-externs -Wold-style-declaration
           -Wold-style-definition -Wstrict-prototypes  -Wtraditional
           -Wtraditional-conversion -Wdeclaration-after-statement -Wpointer-sign

       Debugging Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -fdbg-cnt-list
           -fdbg-cnt=counter-value-list -fdump-noaddr -fdump-unnumbered
           -fdump-unnumbered-links -fdump-translation-unit[-n] -fdump-class-hierarchy[-n]
           -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-statistics
           -fdump-tree-all -fdump-tree-original[-n] -fdump-tree-optimized[-n]
           -fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias -fdump-tree-ch
           -fdump-tree-ssa[-n] -fdump-tree-pre[-n] -fdump-tree-ccp[-n] -fdump-tree-dce[-n]
           -fdump-tree-gimple[-raw] -fdump-tree-mudflap[-n] -fdump-tree-dom[-n]
           -fdump-tree-dse[-n] -fdump-tree-phiopt[-n] -fdump-tree-forwprop[-n]
           -fdump-tree-copyrename[-n] -fdump-tree-nrv -fdump-tree-vect -fdump-tree-sink
           -fdump-tree-sra[-n] -fdump-tree-fre[-n] -fdump-tree-vrp[-n]
           -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n] -fdump-final-insns=file
           -fcompare-debug[=opts]  -fcompare-debug-second -feliminate-dwarf2-dups
           -feliminate-unused-debug-types -feliminate-unused-debug-symbols
           -femit-class-debug-always -fmem-report -fpre-ipa-mem-report
           -fpost-ipa-mem-report -fprofile-arcs -frandom-seed=string -fsched-verbose=n
           -fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose
           -ftest-coverage  -ftime-report -fvar-tracking -fvar-tracking-assignments
           -fvar-tracking-assignments-toggle -g  -glevel  -gtoggle  -gcoff -gdwarf-version
           -ggdb  -gstabs  -gstabs+  -gstrict-dwarf  -gno-strict-dwarf -gvms  -gxcoff
           -gxcoff+ -fno-merge-debug-strings -fno-dwarf2-cfi-asm
           -fdebug-prefix-map=old=new -femit-struct-debug-baseonly
           -femit-struct-debug-reduced -femit-struct-debug-detailed[=spec-list] -p  -pg
           -print-file-name=library  -print-libgcc-file-name -print-multi-directory
           -print-multi-lib  -print-multi-os-directory -print-prog-name=program
           -print-search-dirs  -Q -print-sysroot -print-sysroot-headers-suffix -save-temps
           -time[=file]

       Optimization Options
           -falign-functions[=n] -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
           -fassociative-math -fauto-inc-dec -fbranch-probabilities
           -fbranch-target-load-optimize -fbranch-target-load-optimize2 -fbtr-bb-exclusive
           -fcaller-saves -fcheck-data-deps -fconserve-stack -fcprop-registers
           -fcrossjumping -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules
           -fcx-limited-range -fdata-sections -fdce -fdce -fdelayed-branch
           -fdelete-null-pointer-checks -fdse -fdse -fearly-inlining
           -fexpensive-optimizations -ffast-math -ffinite-math-only -ffloat-store
           -fforward-propagate -ffunction-sections -fgcse -fgcse-after-reload -fgcse-las
           -fgcse-lm -fgcse-sm -fif-conversion -fif-conversion2 -findirect-inlining
           -finline-functions -finline-functions-called-once -finline-limit=n
           -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-matrix-reorg -fipa-pta
           -fipa-pure-const -fipa-reference -fipa-struct-reorg -fipa-type-escape
           -fira-algorithm=algorithm -fira-region=region -fira-coalesce
           -fno-ira-share-save-slots -fno-ira-share-spill-slots -fira-verbose=n -fivopts
           -fkeep-inline-functions -fkeep-static-consts -floop-block -floop-interchange
           -floop-strip-mine -fmerge-all-constants -fmerge-constants -fmodulo-sched
           -fmodulo-sched-allow-regmoves -fmove-loop-invariants -fmudflap -fmudflapir
           -fmudflapth -fno-branch-count-reg -fno-default-inline -fno-defer-pop
           -fno-function-cse -fno-guess-branch-probability -fno-inline -fno-math-errno
           -fno-peephole -fno-peephole2 -fno-sched-interblock -fno-sched-spec
           -fno-signed-zeros -fno-toplevel-reorder -fno-trapping-math
           -fno-zero-initialized-in-bss -fomit-frame-pointer -foptimize-register-move
           -foptimize-sibling-calls -fpeel-loops -fpredictive-commoning
           -fprefetch-loop-arrays -fprofile-correction -fprofile-dir=path
           -fprofile-generate -fprofile-generate=path -fprofile-use -fprofile-use=path
           -fprofile-values -freciprocal-math -fregmove -frename-registers
           -freorder-blocks -freorder-blocks-and-partition -freorder-functions
           -frerun-cse-after-loop -freschedule-modulo-scheduled-loops -frounding-math
           -frtl-abstract-sequences -fsched2-use-superblocks -fsched2-use-traces
           -fsched-spec-load -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n]
           -fsched-stalled-insns[=n] -fschedule-insns -fschedule-insns2 -fsection-anchors
           -fsee -fselective-scheduling -fselective-scheduling2 -fsel-sched-pipelining
           -fsel-sched-pipelining-outer-loops -fsignaling-nans -fsingle-precision-constant
           -fsplit-ivs-in-unroller -fsplit-wide-types -fstack-protector
           -fstack-protector-all -fstrict-aliasing -fstrict-overflow -fthread-jumps
           -ftracer -ftree-builtin-call-dce -ftree-ccp -ftree-ch
           -ftree-coalesce-inline-vars -ftree-coalesce-vars -ftree-copy-prop
           -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-fre
           -ftree-loop-im -ftree-loop-distribution -ftree-loop-ivcanon -ftree-loop-linear
           -ftree-loop-optimize -ftree-parallelize-loops=n -ftree-pre -ftree-reassoc
           -ftree-sink -ftree-sra -ftree-switch-conversion -ftree-ter
           -ftree-vect-loop-version -ftree-vectorize -ftree-vrp -funit-at-a-time
           -funroll-all-loops -funroll-loops -funsafe-loop-optimizations
           -funsafe-math-optimizations -funswitch-loops -fvariable-expansion-in-unroller
           -fvect-cost-model -fvpt -fweb -fwhole-program --param name=value -O  -O0  -O1
           -O2  -O3  -Os

       Preprocessor Options
           -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM  -dN -Dmacro[=defn]
           -E  -H -idirafter dir -include file  -imacros file -iprefix file  -iwithprefix
           dir -iwithprefixbefore dir  -isystem dir -imultilib dir -isysroot dir -M  -MM
           -MF  -MG  -MP  -MQ  -MT  -nostdinc -P  -fworking-directory  -remap -trigraphs
           -undef  -Umacro  -Wp,option -Xpreprocessor option

       Assembler Option
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -llibrary -nostartfiles  -nodefaultlibs  -nostdlib -pie
           -rdynamic -s  -static  -static-libgcc  -shared  -shared-libgcc  -symbolic -T
           script  -Wl,option  -Xlinker option -u symbol

       Directory Options
           -Bprefix  -Idir  -iquotedir  -Ldir -specs=file  -I- --sysroot=dir

       Target Options
           -V version  -b machine

       Machine Dependent Options
           ARC Options -EB  -EL -mmangle-cpu  -mcpu=cpu  -mtext=text-section -mdata=data-
           section  -mrodata=readonly-data-section

           ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name -mapcs-stack-check
           -mno-apcs-stack-check -mapcs-float  -mno-apcs-float -mapcs-reentrant
           -mno-apcs-reentrant -msched-prolog  -mno-sched-prolog -mlittle-endian
           -mbig-endian  -mwords-little-endian -mfloat-abi=name  -msoft-float
           -mhard-float  -mfpe -mthumb-interwork  -mno-thumb-interwork -mcpu=name
           -march=name  -mfpu=name -mstructure-size-boundary=n -mabort-on-noreturn
           -mlong-calls  -mno-long-calls -msingle-pic-base  -mno-single-pic-base
           -mpic-register=reg -mnop-fun-dllimport -mcirrus-fix-invalid-insns
           -mno-cirrus-fix-invalid-insns -mpoke-function-name -mthumb  -marm -mtpcs-frame
           -mtpcs-leaf-frame -mcaller-super-interworking  -mcallee-super-interworking
           -mtp=name -mword-relocations -mfix-cortex-m3-ldrd

           AVR Options -mmcu=mcu  -msize  -mno-interrupts -mcall-prologues  -mno-tablejump
           -mtiny-stack  -mint8

           Blackfin Options -mcpu=cpu[-sirevision] -msim -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer -mspecld-anomaly  -mno-specld-anomaly
           -mcsync-anomaly  -mno-csync-anomaly -mlow-64k -mno-low64k  -mstack-check-l1
           -mid-shared-library -mno-id-shared-library  -mshared-library-id=n
           -mleaf-id-shared-library  -mno-leaf-id-shared-library -msep-data  -mno-sep-data
           -mlong-calls  -mno-long-calls -mfast-fp -minline-plt -mmulticore  -mcorea
           -mcoreb  -msdram -micplb

           CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
           -melinux-stacksize=n -metrax4  -metrax100  -mpdebug  -mcc-init
           -mno-side-effects -mstack-align  -mdata-align  -mconst-align -m32-bit  -m16-bit
           -m8-bit  -mno-prologue-epilogue  -mno-gotplt -melf  -maout  -melinux  -mlinux
           -sim  -sim2 -mmul-bug-workaround  -mno-mul-bug-workaround

           CRX Options -mmac -mpush-args

           Darwin Options -all_load  -allowable_client  -arch  -arch_errors_fatal
           -arch_only  -bind_at_load  -bundle  -bundle_loader -client_name
           -compatibility_version  -current_version -dead_strip -dependency-file
           -dylib_file  -dylinker_install_name -dynamic  -dynamiclib
           -exported_symbols_list -filelist  -flat_namespace  -force_cpusubtype_ALL
           -force_flat_namespace  -headerpad_max_install_names -iframework -image_base
           -init  -install_name  -keep_private_externs -multi_module  -multiply_defined
           -multiply_defined_unused -noall_load   -no_dead_strip_inits_and_terms
           -nofixprebinding -nomultidefs  -noprebind  -noseglinkedit -pagezero_size
           -prebind  -prebind_all_twolevel_modules -private_bundle  -read_only_relocs
           -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
           -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr
           -segs_read_write_addr -seg_addr_table  -seg_addr_table_filename  -seglinkedit
           -segprot  -segs_read_only_addr  -segs_read_write_addr -single_module  -static
           -sub_library  -sub_umbrella -twolevel_namespace  -umbrella  -undefined
           -unexported_symbols_list  -weak_reference_mismatches -whatsloaded -F -gused
           -gfull -mmacosx-version-min=version -mkernel -mone-byte-bool

           DEC Alpha Options -mno-fp-regs  -msoft-float  -malpha-as  -mgas -mieee
           -mieee-with-inexact  -mieee-conformant -mfp-trap-mode=mode
           -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants -mcpu=cpu-type
           -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix -mfloat-vax  -mfloat-ieee
           -mexplicit-relocs  -msmall-data  -mlarge-data -msmall-text  -mlarge-text
           -mmemory-latency=time

           DEC Alpha/VMS Options -mvms-return-codes

           FR30 Options -msmall-model -mno-lsim

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float  -msoft-float
           -malloc-cc  -mfixed-cc  -mdword  -mno-dword -mdouble  -mno-double -mmedia
           -mno-media  -mmuladd  -mno-muladd -mfdpic  -minline-plt -mgprel-ro
           -multilib-library-pic -mlinked-fp  -mlong-calls  -malign-labels -mlibrary-pic
           -macc-4  -macc-8 -mpack  -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move
           -moptimize-membar -mno-optimize-membar -mscc  -mno-scc  -mcond-exec
           -mno-cond-exec -mvliw-branch  -mno-vliw-branch -mmulti-cond-exec
           -mno-multi-cond-exec  -mnested-cond-exec -mno-nested-cond-exec  -mtomcat-stats
           -mTLS -mtls -mcpu=cpu

           GNU/Linux Options -muclibc

           H8/300 Options -mrelax  -mh  -ms  -mn  -mint32  -malign-300

           HPPA Options -march=architecture-type -mbig-switch  -mdisable-fpregs
           -mdisable-indexing -mfast-indirect-calls  -mgas  -mgnu-ld   -mhp-ld
           -mfixed-range=register-range -mjump-in-delay -mlinker-opt -mlong-calls
           -mlong-load-store  -mno-big-switch  -mno-disable-fpregs -mno-disable-indexing
           -mno-fast-indirect-calls  -mno-gas -mno-jump-in-delay  -mno-long-load-store
           -mno-portable-runtime  -mno-soft-float -mno-space-regs  -msoft-float
           -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0  -mportable-runtime -mschedule=cpu-
           type  -mspace-regs  -msio  -mwsio -munix=unix-std  -nolibdld  -static  -threads

           i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type -mfpmath=unit
           -masm=dialect  -mno-fancy-math-387 -mno-fp-ret-in-387  -msoft-float
           -mno-wide-multiply  -mrtd  -malign-double -mpreferred-stack-boundary=num
           -mincoming-stack-boundary=num -mcld -mcx16 -msahf -mmovbe -mcrc32 -mrecip -mmmx
           -msse  -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx -maes -mpclmul
           -mfsgsbase -mrdrnd -mf16c -mfused-madd -msse4a -m3dnow -mpopcnt -mabm -mbmi
           -mtbm -mfma4 -mxop -mlwp -mthreads  -mno-align-stringops
           -minline-all-stringops -minline-stringops-dynamically -mstringop-strategy=alg
           -mpush-args  -maccumulate-outgoing-args  -m128bit-long-double
           -m96bit-long-double  -mregparm=num  -msseregparm -mveclibabi=type -mpc32 -mpc64
           -mpc80 -mstackrealign -momit-leaf-frame-pointer  -mno-red-zone
           -mno-tls-direct-seg-refs -mcmodel=code-model -m32  -m64
           -mlarge-data-threshold=num -msse2avx

           i386 and x86-64 Windows Options -mconsole -mcygwin -mno-cygwin -mdll
           -mnop-fun-dllimport -mthread -mwin32 -mwindows

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld  -mno-pic
           -mvolatile-asm-stop  -mregister-names  -mno-sdata -mconstant-gp  -mauto-pic
           -minline-float-divide-min-latency -minline-float-divide-max-throughput
           -minline-int-divide-min-latency -minline-int-divide-max-throughput
           -minline-sqrt-min-latency -minline-sqrt-max-throughput -mno-dwarf2-asm
           -mearly-stop-bits -mfixed-range=register-range -mtls-size=tls-size -mtune=cpu-
           type -mt -pthread -milp32 -mlp64 -mno-sched-br-data-spec -msched-ar-data-spec
           -mno-sched-control-spec -msched-br-in-data-spec -msched-ar-in-data-spec
           -msched-in-control-spec -msched-ldc -mno-sched-control-ldc
           -mno-sched-spec-verbose -mno-sched-prefer-non-data-spec-insns
           -mno-sched-prefer-non-control-spec-insns -mno-sched-count-spec-in-critical-path

           M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops -mno-align-loops
           -missue-rate=number -mbranch-cost=number -mmodel=code-size-model-type
           -msdata=sdata-type -mno-flush-func -mflush-func=name -mno-flush-trap
           -mflush-trap=number -G num

           M32C Options -mcpu=cpu -msim -memregs=number

           M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020  -m68020-40
           -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200  -m5206e  -m528x  -m5307
           -m5407 -mcfv4e  -mbitfield  -mno-bitfield  -mc68000  -mc68020 -mnobitfield
           -mrtd  -mno-rtd  -mdiv  -mno-div  -mshort -mno-short  -mhard-float  -m68881
           -msoft-float  -mpcrel -malign-int  -mstrict-align  -msep-data  -mno-sep-data
           -mshared-library-id=n  -mid-shared-library  -mno-id-shared-library -mxgot
           -mno-xgot

           M68hc1x Options -m6811  -m6812  -m68hc11  -m68hc12   -m68hcs12 -mauto-incdec
           -minmax  -mlong-calls  -mshort -msoft-reg-count=count

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div  -mrelax-immediates
           -mno-relax-immediates  -mwide-bitfields  -mno-wide-bitfields -m4byte-functions
           -mno-4byte-functions  -mcallgraph-data -mno-callgraph-data  -mslow-bytes
           -mno-slow-bytes  -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
           -mstack-increment

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2  -mips3  -mips4
           -mips32  -mips32r2 -mips64  -mips64r2 -mips16  -mno-mips16  -mflip-mips16
           -minterlink-mips16  -mno-interlink-mips16 -mabi=abi  -mabicalls  -mno-abicalls
           -mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64
           -mfp32  -mfp64  -mhard-float  -msoft-float -msingle-float  -mdouble-float
           -mdsp  -mno-dsp  -mdspr2  -mno-dspr2 -mfpu=fpu-type -msmartmips  -mno-smartmips
           -mpaired-single  -mno-paired-single  -mdmx  -mno-mdmx -mips3d  -mno-mips3d
           -mmt  -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32  -msym32  -mno-sym32 -Gnum
           -mlocal-sdata  -mno-local-sdata -mextern-sdata  -mno-extern-sdata  -mgpopt
           -mno-gopt -membedded-data  -mno-embedded-data -muninit-const-in-rodata
           -mno-uninit-const-in-rodata -mcode-readable=setting -msplit-addresses
           -mno-split-addresses -mexplicit-relocs  -mno-explicit-relocs
           -mcheck-zero-division  -mno-check-zero-division -mdivide-traps  -mdivide-breaks
           -mmemcpy  -mno-memcpy  -mlong-calls  -mno-long-calls -mmad  -mno-mad
           -mfused-madd  -mno-fused-madd  -nocpp -mfix-r4000  -mno-fix-r4000  -mfix-r4400
           -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000  -mfix-vr4120  -mno-fix-vr4120
           -mfix-vr4130  -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1 -mflush-func=func
           -mno-flush-func -mbranch-cost=num  -mbranch-likely  -mno-branch-likely
           -mfp-exceptions -mno-fp-exceptions -mvr4130-align -mno-vr4130-align

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon  -mabi=gnu
           -mabi=mmixware  -mzero-extend  -mknuthdiv  -mtoplevel-symbols -melf
           -mbranch-predict  -mno-branch-predict  -mbase-addresses -mno-base-addresses
           -msingle-exit  -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mam33  -mno-am33 -mam33-2
           -mno-am33-2 -mreturn-pointer-on-d0 -mno-crt0  -mrelax

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10 -mbcopy
           -mbcopy-builtin  -mint32  -mno-int16 -mint16  -mno-int32  -mfloat32
           -mno-float64 -mfloat64  -mno-float32  -mabshi  -mno-abshi -mbranch-expensive
           -mbranch-cheap -msplit  -mno-split  -munix-asm  -mdec-asm

           picoChip Options -mae=ae_type -mvliw-lookahead=N -msymbol-as-address
           -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -mpower  -mno-power  -mpower2  -mno-power2 -mpowerpc  -mpowerpc64  -mno-powerpc
           -maltivec  -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
           -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb -mpopcntd
           -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb -mmfpgpr -mno-mfpgpr
           -mhard-dfp -mno-hard-dfp -mnew-mnemonics  -mold-mnemonics -mfull-toc
           -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64  -m32  -mxl-compat
           -mno-xl-compat  -mpe -malign-power  -malign-natural -msoft-float  -mhard-float
           -mmultiple  -mno-multiple -msingle-float -mdouble-float -msimple-fpu -mstring
           -mno-string  -mupdate  -mno-update -mavoid-indexed-addresses
           -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd  -mbit-align
           -mno-bit-align -mstrict-align  -mno-strict-align  -mrelocatable
           -mno-relocatable  -mrelocatable-lib  -mno-relocatable-lib -mtoc  -mno-toc
           -mlittle  -mlittle-endian  -mbig  -mbig-endian -mdynamic-no-pic  -maltivec
           -mswdiv -mprioritize-restricted-insns=priority
           -msched-costly-dep=dependence_type -minsert-sched-nops=scheme -mcall-sysv
           -mcall-netbsd -maix-struct-return  -msvr4-struct-return -mabi=abi-type
           -msecure-plt -mbss-plt -misel -mno-isel -misel=yes  -misel=no -mspe -mno-spe
           -mspe=yes  -mspe=no -mpaired -mgen-cell-microcode -mwarn-cell-microcode
           -mvrsave -mno-vrsave -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes
           -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double -mprototype
           -mno-prototype -msim  -mmvme  -mads  -myellowknife  -memb  -msdata -msdata=opt
           -mvxworks  -G num  -pthread

           S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type -mhard-float
           -msoft-float  -mhard-dfp -mno-hard-dfp -mlong-double-64 -mlong-double-128
           -mbackchain  -mno-backchain -mpacked-stack  -mno-packed-stack -msmall-exec
           -mno-small-exec  -mmvcle -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa
           -mzarch -mtpf-trace -mno-tpf-trace  -mfused-madd  -mno-fused-madd
           -mwarn-framesize  -mwarn-dynamicstack  -mstack-size -mstack-guard
           -mhotpatch=halfwords,halfwords

           Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u -mscore7
           -mscore7d

           SH Options -m1  -m2  -m2e  -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single
           -m4 -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -m5-64media
           -m5-64media-nofpu -m5-32media  -m5-32media-nofpu -m5-compact  -m5-compact-nofpu
           -mb  -ml  -mdalign  -mrelax -mbigtable  -mfmovd  -mhitachi -mrenesas
           -mno-renesas -mnomacsave -mieee  -mbitops  -misize  -minline-ic_invalidate
           -mpadstruct  -mspace -mprefergot  -musermode -multcost=number -mdiv=strategy
           -mdivsi3_libfunc=name -mfixed-range=register-range -madjust-unroll
           -mindexed-addressing -mgettrcost=number -mpt-fixed -minvalid-symbols

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -m32  -m64
           -mapp-regs  -mno-app-regs -mfaster-structs  -mno-faster-structs -mfpu  -mno-fpu
           -mhard-float  -msoft-float -mhard-quad-float  -msoft-quad-float -mimpure-text
           -mno-impure-text  -mlittle-endian -mstack-bias  -mno-stack-bias
           -munaligned-doubles  -mno-unaligned-doubles -mv8plus  -mno-v8plus  -mvis
           -mno-vis -threads -pthreads -pthread

           SPU Options -mwarn-reloc -merror-reloc -msafe-dma -munsafe-dma -mbranch-hints
           -msmall-mem -mlarge-mem -mstdmain -mfixed-range=register-range

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep -mprolog-function
           -mno-prolog-function  -mspace -mtda=n  -msda=n  -mzda=n -mapp-regs
           -mno-app-regs -mdisable-callt  -mno-disable-callt -mv850e1 -mv850e -mv850
           -mbig-switch

           VAX Options -mg  -mgnu  -munix

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy  -Xbind-now

           x86-64 Options See i386 and x86-64 Options.

           Xstormy16 Options -msim

           Xtensa Options -mconst16 -mno-const16 -mfused-madd  -mno-fused-madd
           -mserialize-volatile  -mno-serialize-volatile -mtext-section-literals
           -mno-text-section-literals -mtarget-align  -mno-target-align -mlongcalls
           -mno-longcalls

           zSeries Options See S/390 and zSeries Options.

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
           -fnon-call-exceptions  -funwind-tables -fasynchronous-unwind-tables
           -finhibit-size-directive  -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...  -fno-common  -fno-ident
           -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE -fno-jump-tables
           -frecord-gcc-switches -freg-struct-return  -fshort-enums -fshort-double
           -fshort-wchar -fverbose-asm  -fpack-struct[=n]  -fstack-check
           -fstack-limit-register=reg  -fstack-limit-symbol=sym -fno-stack-limit
           -fargument-alias  -fargument-noalias -fargument-noalias-global
           -fargument-noalias-anything -fleading-underscore  -ftls-model=model -ftrapv
           -fwrapv  -fbounds-check -fvisibility

   Options Controlling the Kind of Output
       Compilation can involve up to four stages: preprocessing, compilation proper,
       assembly and linking, always in that order.  GCC is capable of preprocessing and
       compiling several files either into several assembler input files, or into one
       assembler input file; then each assembler input file produces an object file, and
       linking combines all the object files (those newly compiled, and those specified as
       input) into an executable file.

       For any given input file, the file name suffix determines what kind of compilation
       is done:

       file.c
           C source code which must be preprocessed.

       file.i
           C source code which should not be preprocessed.

       file.ii
           C++ source code which should not be preprocessed.

       file.m
           Objective-C source code.  Note that you must link with the libobjc library to
           make an Objective-C program work.

       file.mi
           Objective-C source code which should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the libobjc library to
           make an Objective-C++ program work.  Note that .M refers to a literal capital
           M.

       file.mii
           Objective-C++ source code which should not be preprocessed.

       file.h
           C, C++, Objective-C or Objective-C++ header file to be turned into a
           precompiled header.

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++ source code which must be preprocessed.  Note that in .cxx, the last two
           letters must both be literally x.  Likewise, .C refers to a literal capital C.

       file.mm
       file.M
           Objective-C++ source code which must be preprocessed.

       file.mii
           Objective-C++ source code which should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code which should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed form Fortran source code which must be preprocessed (with the traditional
           preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code which should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free form Fortran source code which must be preprocessed (with the traditional
           preprocessor).

       file.ads
           Ada source code file which contains a library unit declaration (a declaration
           of a package, subprogram, or generic, or a generic instantiation), or a library
           unit renaming declaration (a package, generic, or subprogram renaming
           declaration).  Such files are also called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram or package
           body).  Such files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code which must be preprocessed.

       other
           An object file to be fed straight into linking.  Any file name with no
           recognized suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather than
           letting the compiler choose a default based on the file name suffix).  This
           option applies to all following input files until the next -x option.  Possible
           values for language are:

                   c  c-header  c-cpp-output
                   c++  c++-header  c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   f77  f77-cpp-input f95  f95-cpp-input
                   java

       -x none
           Turn off any specification of a language, so that subsequent files are handled
           according to their file name suffixes (as they are if -x has not been used at
           all).

       -pass-exit-codes
           Normally the gcc program will exit with the code of 1 if any phase of the
           compiler returns a non-success return code.  If you specify -pass-exit-codes,
           the gcc program will instead return with numerically highest error produced by
           any phase that returned an error indication.  The C, C++, and Fortran frontends
           return 4, if an internal compiler error is encountered.

       If you only want some of the stages of compilation, you can use -x (or filename
       suffixes) to tell gcc where to start, and one of the options -c, -S, or -E to say
       where gcc is to stop.  Note that some combinations (for example, -x cpp-output -E)
       instruct gcc to do nothing at all.

       -c  Compile or assemble the source files, but do not link.  The linking stage
           simply is not done.  The ultimate output is in the form of an object file for
           each source file.

           By default, the object file name for a source file is made by replacing the
           suffix .c, .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly, are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The output is in
           the form of an assembler code file for each non-assembler input file specified.

           By default, the assembler file name for a source file is made by replacing the
           suffix .c, .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.  The output
           is in the form of preprocessed source code, which is sent to the standard
           output.

           Input files which don't require preprocessing are ignored.

       -o file
           Place output in file file.  This applies regardless to whatever sort of output
           is being produced, whether it be an executable file, an object file, an
           assembler file or preprocessed C code.

           If -o is not specified, the default is to put an executable file in a.out, the
           object file for source.suffix in source.o, its assembler file in source.s, a
           precompiled header file in source.suffix.gch, and all preprocessed C source on
           standard output.

       -v  Print (on standard error output) the commands executed to run the stages of
           compilation.  Also print the version number of the compiler driver program and
           of the preprocessor and the compiler proper.

       -###
           Like -v except the commands are not executed and all command arguments are
           quoted.  This is useful for shell scripts to capture the driver-generated
           command lines.

       -pipe
           Use pipes rather than temporary files for communication between the various
           stages of compilation.  This fails to work on some systems where the assembler
           is unable to read from a pipe; but the GNU assembler has no trouble.

       -combine
           If you are compiling multiple source files, this option tells the driver to
           pass all the source files to the compiler at once (for those languages for
           which the compiler can handle this).  This will allow intermodule analysis
           (IMA) to be performed by the compiler.  Currently the only language for which
           this is supported is C.  If you pass source files for multiple languages to the
           driver, using this option, the driver will invoke the compiler(s) that support
           IMA once each, passing each compiler all the source files appropriate for it.
           For those languages that do not support IMA this option will be ignored, and
           the compiler will be invoked once for each source file in that language.  If
           you use this option in conjunction with -save-temps, the compiler will generate
           multiple pre-processed files (one for each source file), but only one
           (combined) .o or .s file.

       --help
           Print (on the standard output) a description of the command line options
           understood by gcc.  If the -v option is also specified then --help will also be
           passed on to the various processes invoked by gcc, so that they can display the
           command line options they accept.  If the -Wextra option has also been
           specified (prior to the --help option), then command line options which have no
           documentation associated with them will also be displayed.

       --target-help
           Print (on the standard output) a description of target-specific command line
           options for each tool.  For some targets extra target-specific information may
           also be printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command line options
           understood by the compiler that fit into all specified classes and qualifiers.
           These are the supported classes:

           optimizers
               This will display all of the optimization options supported by the
               compiler.

           warnings
               This will display all of the options controlling warning messages produced
               by the compiler.

           target
               This will display target-specific options.  Unlike the --target-help option
               however, target-specific options of the linker and assembler will not be
               displayed.  This is because those tools do not currently support the
               extended --help= syntax.

           params
               This will display the values recognized by the --param option.

           language
               This will display the options supported for language, where language is the
               name of one of the languages supported in this version of GCC.

           common
               This will display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options which are undocumented.

           joined
               Display options which take an argument that appears after an equal sign in
               the same continuous piece of text, such as: --help=target.

           separate
               Display options which take an argument that appears as a separate word
               following the original option, such as: -o output-file.

           Thus for example to display all the undocumented target-specific switches
           supported by the compiler the following can be used:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the ^ character,
           so for example to display all binary warning options (i.e., ones that are
           either on or off and that do not take an argument), which have a description
           the following can be used:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted qualifiers.

           Combining several classes is possible, although this usually restricts the
           output by so much that there is nothing to display.  One case where it does
           work however is when one of the classes is target.  So for example to display
           all the target-specific optimization options the following can be used:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each successive use
           will display its requested class of options, skipping those that have already
           been displayed.

           If the -Q option appears on the command line before the --help= option, then
           the descriptive text displayed by --help= is changed.  Instead of describing
           the displayed options, an indication is given as to whether the option is
           enabled, disabled or set to a specific value (assuming that the compiler knows
           this at the point where the --help= option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The output is sensitive to the effects of previous command line options, so for
           example it is possible to find out which optimizations are enabled at -O2 by
           using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are enabled by -O3 by
           using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
           Display the version number and copyrights of the invoked GCC.

       -wrapper
           Invoke all subcommands under a wrapper program. It takes a single comma
           separated list as an argument, which will be used to invoke the wrapper:

                   gcc -c t.c -wrapper gdb,--args

           This will invoke all subprograms of gcc under "gdb --args", thus cc1 invocation
           will be "gdb --args cc1 ...".

       @file
           Read command-line options from file.  The options read are inserted in place of
           the original @file option.  If file does not exist, or cannot be read, then the
           option will be treated literally, and not removed.

           Options in file are separated by whitespace.  A whitespace character may be
           included in an option by surrounding the entire option in either single or
           double quotes.  Any character (including a backslash) may be included by
           prefixing the character to be included with a backslash.  The file may itself
           contain additional @file options; any such options will be processed
           recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP, .c++,
       .cp, or .cxx; C++ header files often use .hh, .hpp, .H, or (for shared template
       code) .tcc; and preprocessed C++ files use the suffix .ii.  GCC recognizes files
       with these names and compiles them as C++ programs even if you call the compiler
       the same way as for compiling C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program that calls
       GCC and treats .c, .h and .i files as C++ source files instead of C source files
       unless -x is used, and automatically specifies linking against the C++ library.
       This program is also useful when precompiling a C header file with a .h extension
       for use in C++ compilations.  On many systems, g++ is also installed with the name
       c++.

       When you compile C++ programs, you may specify many of the same command-line
       options that you use for compiling programs in any language; or command-line
       options meaningful for C and related languages; or options that are meaningful only
       for C++ programs.

   Options Controlling C Dialect
       The following options control the dialect of C (or languages derived from C, such
       as C++, Objective-C and Objective-C++) that the compiler accepts:

       -ansi
           In C mode, this is equivalent to -std=c89. In C++ mode, it is equivalent to
           -std=c++98.

           This turns off certain features of GCC that are incompatible with ISO C90 (when
           compiling C code), or of standard C++ (when compiling C++ code), such as the
           "asm" and "typeof" keywords, and predefined macros such as "unix" and "vax"
           that identify the type of system you are using.  It also enables the
           undesirable and rarely used ISO trigraph feature.  For the C compiler, it
           disables recognition of C++ style // comments as well as the "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__" and
           "__typeof__" continue to work despite -ansi.  You would not want to use them in
           an ISO C program, of course, but it is useful to put them in header files that
           might be included in compilations done with -ansi.  Alternate predefined macros
           such as "__unix__" and "__vax__" are also available, with or without -ansi.

           The -ansi option does not cause non-ISO programs to be rejected gratuitously.
           For that, -pedantic is required in addition to -ansi.

           The macro "__STRICT_ANSI__" is predefined when the -ansi option is used.  Some
           header files may notice this macro and refrain from declaring certain functions
           or defining certain macros that the ISO standard doesn't call for; this is to
           avoid interfering with any programs that might use these names for other
           things.

           Functions that would normally be built in but do not have semantics defined by
           ISO C (such as "alloca" and "ffs") are not built-in functions when -ansi is
           used.

       -std=
           Determine the language standard.   This option is currently only supported when
           compiling C or C++.

           The compiler can accept several base standards, such as c89 or c++98, and GNU
           dialects of those standards, such as gnu89 or gnu++98.  By specifying a base
           standard, the compiler will accept all programs following that standard and
           those using GNU extensions that do not contradict it.  For example, -std=c89
           turns off certain features of GCC that are incompatible with ISO C90, such as
           the "asm" and "typeof" keywords, but not other GNU extensions that do not have
           a meaning in ISO C90, such as omitting the middle term of a "?:" expression. On
           the other hand, by specifying a GNU dialect of a standard, all features the
           compiler support are enabled, even when those features change the meaning of
           the base standard and some strict-conforming programs may be rejected.  The
           particular standard is used by -pedantic to identify which features are GNU
           extensions given that version of the standard. For example -std=gnu89 -pedantic
           would warn about C++ style // comments, while -std=gnu99 -pedantic would not.

           A value for this option must be provided; possible values are

           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that conflict with ISO
               C90 are disabled). Same as -ansi for C code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO C99.  Note that this standard is not yet fully supported; see
               <http://gcc.gnu.org/gcc-4.4/c99status.html> for more information.  The
               names c9x and iso9899:199x are deprecated.

           gnu89
               GNU dialect of ISO C90 (including some C99 features). This is the default
               for C code.

           gnu99
           gnu9x
               GNU dialect of ISO C99.  When ISO C99 is fully implemented in GCC, this
               will become the default.  The name gnu9x is deprecated.

           c++98
               The 1998 ISO C++ standard plus amendments. Same as -ansi for C++ code.

           gnu++98
               GNU dialect of -std=c++98.  This is the default for C++ code.

           c++0x
               The working draft of the upcoming ISO C++0x standard. This option enables
               experimental features that are likely to be included in C++0x. The working
               draft is constantly changing, and any feature that is enabled by this flag
               may be removed from future versions of GCC if it is not part of the C++0x
               standard.

           gnu++0x
               GNU dialect of -std=c++0x. This option enables experimental features that
               may be removed in future versions of GCC.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU semantics for
           "inline" functions when in C99 mode.
             This option is accepted and ignored by GCC versions 4.1.3 up to but not
           including 4.3.  In GCC versions 4.3 and later it changes the behavior of GCC in
           C99 mode.  Using this option is roughly equivalent to adding the "gnu_inline"
           function attribute to all inline functions.

           The option -fno-gnu89-inline explicitly tells GCC to use the C99 semantics for
           "inline" when in C99 or gnu99 mode (i.e., it specifies the default behavior).
           This option was first supported in GCC 4.3.  This option is not supported in
           C89 or gnu89 mode.

           The preprocessor macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be
           used to check which semantics are in effect for "inline" functions.

       -aux-info filename
           Output to the given filename prototyped declarations for all functions declared
           and/or defined in a translation unit, including those in header files.  This
           option is silently ignored in any language other than C.

           Besides declarations, the file indicates, in comments, the origin of each
           declaration (source file and line), whether the declaration was implicit,
           prototyped or unprototyped (I, N for new or O for old, respectively, in the
           first character after the line number and the colon), and whether it came from
           a declaration or a definition (C or F, respectively, in the following
           character).  In the case of function definitions, a K&R-style list of arguments
           followed by their declarations is also provided, inside comments, after the
           declaration.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so that code can use
           these words as identifiers.  You can use the keywords "__asm__", "__inline__"
           and "__typeof__" instead.  -ansi implies -fno-asm.

           In C++, this switch only affects the "typeof" keyword, since "asm" and "inline"
           are standard keywords.  You may want to use the -fno-gnu-keywords flag instead,
           which has the same effect.  In C99 mode (-std=c99 or -std=gnu99), this switch
           only affects the "asm" and "typeof" keywords, since "inline" is a standard
           keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with __builtin_ as prefix.

           GCC normally generates special code to handle certain built-in functions more
           efficiently; for instance, calls to "alloca" may become single instructions
           that adjust the stack directly, and calls to "memcpy" may become inline copy
           loops.  The resulting code is often both smaller and faster, but since the
           function calls no longer appear as such, you cannot set a breakpoint on those
           calls, nor can you change the behavior of the functions by linking with a
           different library.  In addition, when a function is recognized as a built-in
           function, GCC may use information about that function to warn about problems
           with calls to that function, or to generate more efficient code, even if the
           resulting code still contains calls to that function.  For example, warnings
           are given with -Wformat for bad calls to "printf", when "printf" is built in,
           and "strlen" is known not to modify global memory.

           With the -fno-builtin-function option only the built-in function function is
           disabled.  function must not begin with __builtin_.  If a function is named
           that is not built-in in this version of GCC, this option is ignored.  There is
           no corresponding -fbuiltin-function option; if you wish to enable built-in
           functions selectively when using -fno-builtin or -ffreestanding, you may define
           macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fhosted
           Assert that compilation takes place in a hosted environment.  This implies
           -fbuiltin.  A hosted environment is one in which the entire standard library is
           available, and in which "main" has a return type of "int".  Examples are nearly
           everything except a kernel.  This is equivalent to -fno-freestanding.

       -ffreestanding
           Assert that compilation takes place in a freestanding environment.  This
           implies -fno-builtin.  A freestanding environment is one in which the standard
           library may not exist, and program startup may not necessarily be at "main".
           The most obvious example is an OS kernel.  This is equivalent to -fno-hosted.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in
           Fortran.  When -fopenmp is specified, the compiler generates parallel code
           according to the OpenMP Application Program Interface v2.5
           <http://www.openmp.org/>.  This option implies -pthread, and thus is only
           supported on targets that have support for -pthread.

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header files.

           Some cases of unnamed fields in structures and unions are only accepted with
           this option.

       -trigraphs
           Support ISO C trigraphs.  The -ansi option (and -std options for strict ISO C
           conformance) implies -trigraphs.

       -no-integrated-cpp
           Performs a compilation in two passes: preprocessing and compiling.  This option
           allows a user supplied "cc1", "cc1plus", or "cc1obj" via the -B option.  The
           user supplied compilation step can then add in an additional preprocessing step
           after normal preprocessing but before compiling.  The default is to use the
           integrated cpp (internal cpp)

           The semantics of this option will change if "cc1", "cc1plus", and "cc1obj" are
           merged.

       -traditional
       -traditional-cpp
           Formerly, these options caused GCC to attempt to emulate a pre-standard C
           compiler.  They are now only supported with the -E switch.  The preprocessor
           continues to support a pre-standard mode.  See the GNU CPP manual for details.

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second and third
           arguments.  The value of such an expression is void.  This option is not
           supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with differing numbers of elements
           and/or incompatible element types.  This option should not be used for new
           code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each kind of machine has a default for what "char" should be.  It is either
           like "unsigned char" by default or like "signed char" by default.

           Ideally, a portable program should always use "signed char" or "unsigned char"
           when it depends on the signedness of an object.  But many programs have been
           written to use plain "char" and expect it to be signed, or expect it to be
           unsigned, depending on the machines they were written for.  This option, and
           its inverse, let you make such a program work with the opposite default.

           The type "char" is always a distinct type from each of "signed char" or
           "unsigned char", even though its behavior is always just like one of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note that this is equivalent to -fno-unsigned-char, which is the negative form
           of -funsigned-char.  Likewise, the option -fno-signed-char is equivalent to
           -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or unsigned, when the
           declaration does not use either "signed" or "unsigned".  By default, such a
           bit-field is signed, because this is consistent: the basic integer types such
           as "int" are signed types.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only meaningful for C++
       programs; but you can also use most of the GNU compiler options regardless of what
       language your program is in.  For example, you might compile a file "firstClass.C"
       like this:

               g++ -g -frepo -O -c firstClass.C

       In this example, only -frepo is an option meant only for C++ programs; you can use
       the other options with any language supported by GCC.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  Version 2 is the version of the C++ ABI that
           first appeared in G++ 3.4.  Version 1 is the version of the C++ ABI that first
           appeared in G++ 3.2.  Version 0 will always be the version that conforms most
           closely to the C++ ABI specification.  Therefore, the ABI obtained using
           version 0 will change as ABI bugs are fixed.

           The default is version 2.

       -fno-access-control
           Turn off all access checking.  This switch is mainly useful for working around
           bugs in the access control code.

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null before attempting
           to modify the storage allocated.  This check is normally unnecessary because
           the C++ standard specifies that "operator new" will only return 0 if it is
           declared throw(), in which case the compiler will always check the return value
           even without this option.  In all other cases, when "operator new" has a non-
           empty exception specification, memory exhaustion is signalled by throwing
           "std::bad_alloc".  See also new (nothrow).

       -fconserve-space
           Put uninitialized or runtime-initialized global variables into the common
           segment, as C does.  This saves space in the executable at the cost of not
           diagnosing duplicate definitions.  If you compile with this flag and your
           program mysteriously crashes after "main()" has completed, you may have an
           object that is being destroyed twice because two definitions were merged.

           This option is no longer useful on most targets, now that support has been
           added for putting variables into BSS without making them common.

       -fno-deduce-init-list
           Disable deduction of a template type parameter as std::initializer_list from a
           brace-enclosed initializer list, i.e.

                   template <class T> auto forward(T t) -> decltype (realfn (t))
                   {
                     return realfn (t);
                   }

                   void f()
                   {
                     forward({1,2}); // call forward<std::initializer_list<int>>
                   }

           This option is present because this deduction is an extension to the current
           specification in the C++0x working draft, and there was some concern about
           potential overload resolution problems.

       -ffriend-injection
           Inject friend functions into the enclosing namespace, so that they are visible
           outside the scope of the class in which they are declared.  Friend functions
           were documented to work this way in the old Annotated C++ Reference Manual, and
           versions of G++ before 4.1 always worked that way.  However, in ISO C++ a
           friend function which is not declared in an enclosing scope can only be found
           using argument dependent lookup.  This option causes friends to be injected as
           they were in earlier releases.

           This option is for compatibility, and may be removed in a future release of
           G++.

       -fno-elide-constructors
           The C++ standard allows an implementation to omit creating a temporary which is
           only used to initialize another object of the same type.  Specifying this
           option disables that optimization, and forces G++ to call the copy constructor
           in all cases.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception specifications at
           runtime.  This option violates the C++ standard, but may be useful for reducing
           code size in production builds, much like defining NDEBUG.  This does not give
           user code permission to throw exceptions in violation of the exception
           specifications; the compiler will still optimize based on the specifications,
           so throwing an unexpected exception will result in undefined behavior.

       -ffor-scope
       -fno-for-scope
           If -ffor-scope is specified, the scope of variables declared in a for-init-
           statement is limited to the for loop itself, as specified by the C++ standard.
           If -fno-for-scope is specified, the scope of variables declared in a for-init-
           statement extends to the end of the enclosing scope, as was the case in old
           versions of G++, and other (traditional) implementations of C++.

           The default if neither flag is given to follow the standard, but to allow and
           give a warning for old-style code that would otherwise be invalid, or have
           different behavior.

       -fno-gnu-keywords
           Do not recognize "typeof" as a keyword, so that code can use this word as an
           identifier.  You can use the keyword "__typeof__" instead.  -ansi implies
           -fno-gnu-keywords.

       -fno-implicit-templates
           Never emit code for non-inline templates which are instantiated implicitly
           (i.e. by use); only emit code for explicit instantiations.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates, either.  The
           default is to handle inlines differently so that compiles with and without
           optimization will need the same set of explicit instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions controlled by
           #pragma implementation.  This will cause linker errors if these functions are
           not inlined everywhere they are called.

       -fms-extensions
           Disable pedantic warnings about constructs used in MFC, such as implicit int
           and getting a pointer to member function via non-standard syntax.

       -fno-nonansi-builtins
           Disable built-in declarations of functions that are not mandated by ANSI/ISO C.
           These include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other
           related functions.

       -fno-operator-names
           Do not treat the operator name keywords "and", "bitand", "bitor", "compl",
           "not", "or" and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not need to issue.
           Currently, the only such diagnostic issued by G++ is the one for a name having
           multiple meanings within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors to warnings.
           Thus, using -fpermissive will allow some nonconforming code to compile.

       -frepo
           Enable automatic template instantiation at link time.  This option also implies
           -fno-implicit-templates.

       -fno-rtti
           Disable generation of information about every class with virtual functions for
           use by the C++ runtime type identification features (dynamic_cast and typeid).
           If you don't use those parts of the language, you can save some space by using
           this flag.  Note that exception handling uses the same information, but it will
           generate it as needed. The dynamic_cast operator can still be used for casts
           that do not require runtime type information, i.e. casts to "void *" or to
           unambiguous base classes.

       -fstats
           Emit statistics about front-end processing at the end of the compilation.  This
           information is generally only useful to the G++ development team.

       -fstrict-enums
           Allow the compiler to optimize using the assumption that a value of enumeration
           type can only be one of the values of the enumeration (as defined in the C++
           standard; basically, a value which can be represented in the minimum number of
           bits needed to represent all the enumerators).  This assumption may not be
           valid if the program uses a cast to convert an arbitrary integer value to the
           enumeration type.

       -ftemplate-depth-n
           Set the maximum instantiation depth for template classes to n.  A limit on the
           template instantiation depth is needed to detect endless recursions during
           template class instantiation.  ANSI/ISO C++ conforming programs must not rely
           on a maximum depth greater than 17.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the C++ ABI for
           thread-safe initialization of local statics.  You can use this option to reduce
           code size slightly in code that doesn't need to be thread-safe.

       -fuse-cxa-atexit
           Register destructors for objects with static storage duration with the
           "__cxa_atexit" function rather than the "atexit" function.  This option is
           required for fully standards-compliant handling of static destructors, but will
           only work if your C library supports "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This will cause
           "std::uncaught_exception" to be incorrect, but is necessary if the runtime
           routine is not available.

       -fvisibility-inlines-hidden
           This switch declares that the user does not attempt to compare pointers to
           inline methods where the addresses of the two functions were taken in different
           shared objects.

           The effect of this is that GCC may, effectively, mark inline methods with
           "__attribute__ ((visibility ("hidden")))" so that they do not appear in the
           export table of a DSO and do not require a PLT indirection when used within the
           DSO.  Enabling this option can have a dramatic effect on load and link times of
           a DSO as it massively reduces the size of the dynamic export table when the
           library makes heavy use of templates.

           The behavior of this switch is not quite the same as marking the methods as
           hidden directly, because it does not affect static variables local to the
           function or cause the compiler to deduce that the function is defined in only
           one shared object.

           You may mark a method as having a visibility explicitly to negate the effect of
           the switch for that method.  For example, if you do want to compare pointers to
           a particular inline method, you might mark it as having default visibility.
           Marking the enclosing class with explicit visibility will have no effect.

           Explicitly instantiated inline methods are unaffected by this option as their
           linkage might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
           This flag attempts to use visibility settings to make GCC's C++ linkage model
           compatible with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The One Definition Rule is relaxed for types without explicit visibility
               specifications which are defined in more than one different shared object:
               those declarations are permitted if they would have been permitted when
               this option was not used.

           In new code it is better to use -fvisibility=hidden and export those classes
           which are intended to be externally visible.  Unfortunately it is possible for
           code to rely, perhaps accidentally, on the Visual Studio behavior.

           Among the consequences of these changes are that static data members of the
           same type with the same name but defined in different shared objects will be
           different, so changing one will not change the other; and that pointers to
           function members defined in different shared objects may not compare equal.
           When this flag is given, it is a violation of the ODR to define types with the
           same name differently.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the linker.  By
           default, G++ will use weak symbols if they are available.  This option exists
           only for testing, and should not be used by end-users; it will result in
           inferior code and has no benefits.  This option may be removed in a future
           release of G++.

       -nostdinc++
           Do not search for header files in the standard directories specific to C++, but
           do still search the other standard directories.  (This option is used when
           building the C++ library.)

       In addition, these optimization, warning, and code generation options have meanings
       only for C++ programs:

       -fno-default-inline
           Do not assume inline for functions defined inside a class scope.
             Note that these functions will have linkage like inline functions; they just
           won't be inlined by default.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn when G++ generates code that is probably not compatible with the vendor-
           neutral C++ ABI.  Although an effort has been made to warn about all such
           cases, there are probably some cases that are not warned about, even though G++
           is generating incompatible code.  There may also be cases where warnings are
           emitted even though the code that is generated will be compatible.

           You should rewrite your code to avoid these warnings if you are concerned about
           the fact that code generated by G++ may not be binary compatible with code
           generated by other compilers.

           The known incompatibilities at this point include:

           ?   Incorrect handling of tail-padding for bit-fields.  G++ may attempt to pack
               data into the same byte as a base class.  For example:

                       struct A { virtual void f(); int f1 : 1; };
                       struct B : public A { int f2 : 1; };

               In this case, G++ will place "B::f2" into the same byte as"A::f1"; other
               compilers will not.  You can avoid this problem by explicitly padding "A"
               so that its size is a multiple of the byte size on your platform; that will
               cause G++ and other compilers to layout "B" identically.

           ?   Incorrect handling of tail-padding for virtual bases.  G++ does not use
               tail padding when laying out virtual bases.  For example:

                       struct A { virtual void f(); char c1; };
                       struct B { B(); char c2; };
                       struct C : public A, public virtual B {};

               In this case, G++ will not place "B" into the tail-padding for "A"; other
               compilers will.  You can avoid this problem by explicitly padding "A" so
               that its size is a multiple of its alignment (ignoring virtual base
               classes); that will cause G++ and other compilers to layout "C"
               identically.

           ?   Incorrect handling of bit-fields with declared widths greater than that of
               their underlying types, when the bit-fields appear in a union.  For
               example:

                       union U { int i : 4096; };

               Assuming that an "int" does not have 4096 bits, G++ will make the union too
               small by the number of bits in an "int".

           ?   Empty classes can be placed at incorrect offsets.  For example:

                       struct A {};

                       struct B {
                         A a;
                         virtual void f ();
                       };

                       struct C : public B, public A {};

               G++ will place the "A" base class of "C" at a nonzero offset; it should be
               placed at offset zero.  G++ mistakenly believes that the "A" data member of
               "B" is already at offset zero.

           ?   Names of template functions whose types involve "typename" or template
               template parameters can be mangled incorrectly.

                       template <typename Q>
                       void f(typename Q::X) {}

                       template <template <typename> class Q>
                       void f(typename Q<int>::X) {}

               Instantiations of these templates may be mangled incorrectly.

           It also warns psABI related changes.  The known psABI changes at this point
           include:

           ?   For SYSV/x86-64, when passing union with long double, it is changed to pass
               in memory as specified in psABI.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" will always be passed in memory.

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn when a class seems unusable because all the constructors or destructors in
           that class are private, and it has neither friends nor public static member
           functions.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn when a class has virtual functions and accessible non-virtual destructor,
           in which case it would be possible but unsafe to delete an instance of a
           derived class through a pointer to the base class.  This warning is also
           enabled if -Weffc++ is specified.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does not match the
           order in which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler will rearrange the member initializers for i and j to match the
           declaration order of the members, emitting a warning to that effect.  This
           warning is enabled by -Wall.

       The following -W... options are not affected by -Wall.

       -Weffc++ (C++ and Objective-C++ only)
           Warn about violations of the following style guidelines from Scott Meyers'
           Effective C++ book:

           ?   Item 11:  Define a copy constructor and an assignment operator for classes
               with dynamically allocated memory.

           ?   Item 12:  Prefer initialization to assignment in constructors.

           ?   Item 14:  Make destructors virtual in base classes.

           ?   Item 15:  Have "operator=" return a reference to *this.

           ?   Item 23:  Don't try to return a reference when you must return an object.

           Also warn about violations of the following style guidelines from Scott Meyers'
           More Effective C++ book:

           ?   Item 6:  Distinguish between prefix and postfix forms of increment and
               decrement operators.

           ?   Item 7:  Never overload "&&", "||", or ",".

           When selecting this option, be aware that the standard library headers do not
           obey all of these guidelines; use grep -v to filter out those warnings.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn also about the use of an uncasted "NULL" as sentinel.  When compiling only
           with GCC this is a valid sentinel, as "NULL" is defined to "__null".  Although
           it is a null pointer constant not a null pointer, it is guaranteed to be of the
           same size as a pointer.  But this use is not portable across different
           compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable warnings when non-templatized friend functions are declared within a
           template.  Since the advent of explicit template specification support in G++,
           if the name of the friend is an unqualified-id (i.e., friend foo(int)), the C++
           language specification demands that the friend declare or define an ordinary,
           nontemplate function.  (Section 14.5.3).  Before G++ implemented explicit
           specification, unqualified-ids could be interpreted as a particular
           specialization of a templatized function.  Because this non-conforming behavior
           is no longer the default behavior for G++, -Wnon-template-friend allows the
           compiler to check existing code for potential trouble spots and is on by
           default.  This new compiler behavior can be turned off with
           -Wno-non-template-friend which keeps the conformant compiler code but disables
           the helpful warning.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used within a C++
           program.  The new-style casts (dynamic_cast, static_cast, reinterpret_cast, and
           const_cast) are less vulnerable to unintended effects and much easier to search
           for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a base class.
           For example, in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           will fail to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable the diagnostic for converting a bound pointer to member function to a
           plain pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned or enumerated
           type to a signed type, over a conversion to an unsigned type of the same size.
           Previous versions of G++ would try to preserve unsignedness, but the standard
           mandates the current behavior.

                   struct A {
                     operator int ();
                     A& operator = (int);
                   };

                   main ()
                   {
                     A a,b;
                     a = b;
                   }

           In this example, G++ will synthesize a default A& operator = (const A&);, while
           cfront will use the user-defined operator =.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++ languages
       themselves.  See

       This section describes the command-line options that are only meaningful for
       Objective-C and Objective-C++ programs, but you can also use most of the language-
       independent GNU compiler options.  For example, you might compile a file
       "some_class.m" like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C and
       Objective-C++ programs; you can use the other options with any language supported
       by GCC.

       Note that since Objective-C is an extension of the C language, Objective-C
       compilations may also use options specific to the C front-end (e.g.,
       -Wtraditional).  Similarly, Objective-C++ compilations may use C++-specific options
       (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and Objective-C++
       programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each literal string
           specified with the syntax "@"..."".  The default class name is
           "NXConstantString" if the GNU runtime is being used, and "NSConstantString" if
           the NeXT runtime is being used (see below).  The -fconstant-cfstrings option,
           if also present, will override the -fconstant-string-class setting and cause
           "@"..."" literals to be laid out as constant CoreFoundation strings.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C runtime.
           This is the default for most types of systems.

       -fnext-runtime
           Generate output compatible with the NeXT runtime.  This is the default for
           NeXT-based systems, including Darwin and Mac OS X.  The macro
           "__NEXT_RUNTIME__" is predefined if (and only if) this option is used.

       -fno-nil-receivers
           Assume that all Objective-C message dispatches (e.g., "[receiver message:arg]")
           in this translation unit ensure that the receiver is not "nil".  This allows
           for more efficient entry points in the runtime to be used.  Currently, this
           option is only available in conjunction with the NeXT runtime on Mac OS X 10.3
           and later.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance variables is a C++
           object with a non-trivial default constructor.  If so, synthesize a special "-
           (id) .cxx_construct" instance method that will run non-trivial default
           constructors on any such instance variables, in order, and then return "self".
           Similarly, check if any instance variable is a C++ object with a non-trivial
           destructor, and if so, synthesize a special "- (void) .cxx_destruct" method
           that will run all such default destructors, in reverse order.

           The "- (id) .cxx_construct" and/or "- (void) .cxx_destruct" methods thusly
           generated will only operate on instance variables declared in the current
           Objective-C class, and not those inherited from superclasses.  It is the
           responsibility of the Objective-C runtime to invoke all such methods in an
           object's inheritance hierarchy.  The "- (id) .cxx_construct" methods will be
           invoked by the runtime immediately after a new object instance is allocated;
           the "- (void) .cxx_destruct" methods will be invoked immediately before the
           runtime deallocates an object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
           support for invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct"
           methods.

       -fobjc-direct-dispatch
           Allow fast jumps to the message dispatcher.  On Darwin this is accomplished via
           the comm page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling in Objective-C,
           similar to what is offered by C++ and Java.  This option is unavailable in
           conjunction with the NeXT runtime on Mac OS X 10.2 and earlier.

                     @try {
                       ...
                          @throw expr;
                       ...
                     }
                     @catch (AnObjCClass *exc) {
                       ...
                         @throw expr;
                       ...
                         @throw;
                       ...
                     }
                     @catch (AnotherClass *exc) {
                       ...
                     }
                     @catch (id allOthers) {
                       ...
                     }
                     @finally {
                       ...
                         @throw expr;
                       ...
                     }

           The @throw statement may appear anywhere in an Objective-C or Objective-C++
           program; when used inside of a @catch block, the @throw may appear without an
           argument (as shown above), in which case the object caught by the @catch will
           be rethrown.

           Note that only (pointers to) Objective-C objects may be thrown and caught using
           this scheme.  When an object is thrown, it will be caught by the nearest @catch
           clause capable of handling objects of that type, analogously to how "catch"
           blocks work in C++ and Java.  A "@catch(id ...)" clause (as shown above) may
           also be provided to catch any and all Objective-C exceptions not caught by
           previous @catch clauses (if any).

           The @finally clause, if present, will be executed upon exit from the
           immediately preceding "@try ... @catch" section.  This will happen regardless
           of whether any exceptions are thrown, caught or rethrown inside the "@try ...
           @catch" section, analogously to the behavior of the "finally" clause in Java.

           There are several caveats to using the new exception mechanism:

           ?   Although currently designed to be binary compatible with "NS_HANDLER"-style
               idioms provided by the "NSException" class, the new exceptions can only be
               used on Mac OS X 10.3 (Panther) and later systems, due to additional
               functionality needed in the (NeXT) Objective-C runtime.

           ?   As mentioned above, the new exceptions do not support handling types other
               than Objective-C objects.   Furthermore, when used from Objective-C++, the
               Objective-C exception model does not interoperate with C++ exceptions at
               this time.  This means you cannot @throw an exception from Objective-C and
               "catch" it in C++, or vice versa (i.e., "throw ... @catch").

           The -fobjc-exceptions switch also enables the use of synchronization blocks for
           thread-safe execution:

                     @synchronized (ObjCClass *guard) {
                       ...
                     }

           Upon entering the @synchronized block, a thread of execution shall first check
           whether a lock has been placed on the corresponding "guard" object by another
           thread.  If it has, the current thread shall wait until the other thread
           relinquishes its lock.  Once "guard" becomes available, the current thread will
           place its own lock on it, execute the code contained in the @synchronized
           block, and finally relinquish the lock (thereby making "guard" available to
           other threads).

           Unlike Java, Objective-C does not allow for entire methods to be marked
           @synchronized.  Note that throwing exceptions out of @synchronized blocks is
           allowed, and will cause the guarding object to be unlocked properly.

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++ programs.

       -freplace-objc-classes
           Emit a special marker instructing ld(1) not to statically link in the resulting
           object file, and allow dyld(1) to load it in at run time instead.  This is used
           in conjunction with the Fix-and-Continue debugging mode, where the object file
           in question may be recompiled and dynamically reloaded in the course of program
           execution, without the need to restart the program itself.  Currently, Fix-and-
           Continue functionality is only available in conjunction with the NeXT runtime
           on Mac OS X 10.3 and later.

       -fzero-link
           When compiling for the NeXT runtime, the compiler ordinarily replaces calls to
           "objc_getClass("...")" (when the name of the class is known at compile time)
           with static class references that get initialized at load time, which improves
           run-time performance.  Specifying the -fzero-link flag suppresses this behavior
           and causes calls to "objc_getClass("...")"  to be retained.  This is useful in
           Zero-Link debugging mode, since it allows for individual class implementations
           to be modified during program execution.

       -gen-decls
           Dump interface declarations for all classes seen in the source file to a file
           named sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by the garbage
           collector.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If a class is declared to implement a protocol, a warning is issued for every
           method in the protocol that is not implemented by the class.  The default
           behavior is to issue a warning for every method not explicitly implemented in
           the class, even if a method implementation is inherited from the superclass.
           If you use the -Wno-protocol option, then methods inherited from the superclass
           are considered to be implemented, and no warning is issued for them.

       -Wselector (Objective-C and Objective-C++ only)
           Warn if multiple methods of different types for the same selector are found
           during compilation.  The check is performed on the list of methods in the final
           stage of compilation.  Additionally, a check is performed for each selector
           appearing in a "@selector(...)"  expression, and a corresponding method for
           that selector has been found during compilation.  Because these checks scan the
           method table only at the end of compilation, these warnings are not produced if
           the final stage of compilation is not reached, for example because an error is
           found during compilation, or because the -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return types are found
           for a given selector when attempting to send a message using this selector to a
           receiver of type "id" or "Class".  When this flag is off (which is the default
           behavior), the compiler will omit such warnings if any differences found are
           confined to types which share the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a "@selector(...)" expression referring to an undeclared selector is
           found.  A selector is considered undeclared if no method with that name has
           been declared before the "@selector(...)" expression, either explicitly in an
           @interface or @protocol declaration, or implicitly in an @implementation
           section.  This option always performs its checks as soon as a "@selector(...)"
           expression is found, while -Wselector only performs its checks in the final
           stage of compilation.  This also enforces the coding style convention that
           methods and selectors must be declared before being used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed by value, if
           any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of the output
       device's aspect (e.g. its width, ...).  The options described below can be used to
       control the diagnostic messages formatting algorithm, e.g. how many characters per
       line, how often source location information should be reported.  Right now, only
       the C++ front end can honor these options.  However it is expected, in the near
       future, that the remaining front ends would be able to digest them correctly.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n characters.
           The default is 72 characters for g++ and 0 for the rest of the front ends
           supported by GCC.  If n is zero, then no line-wrapping will be done; each error
           message will appear on a single line.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages
           reporter to emit once source location information; that is, in case the message
           is too long to fit on a single physical line and has to be wrapped, the source
           location won't be emitted (as prefix) again, over and over, in subsequent
           continuation lines.  This is the default behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages
           reporter to emit the same source location information (as prefix) for physical
           lines that result from the process of breaking a message which is too long to
           fit on a single line.

       -fdiagnostics-show-option
           This option instructs the diagnostic machinery to add text to each diagnostic
           emitted, which indicates which command line option directly controls that
           diagnostic, when such an option is known to the diagnostic machinery.

       -Wcoverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use option.  If
           a source file was changed between -fprofile-gen and -fprofile-use, the files
           with the profile feedback can fail to match the source file and GCC can not use
           the profile feedback information.  By default, GCC emits an error message in
           this case.  The option -Wcoverage-mismatch emits a warning instead of an error.
           GCC does not use appropriate feedback profiles, so using this option can result
           in poorly optimized code.  This option is useful only in the case of very minor
           changes such as bug fixes to an existing code-base.

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions which are not inherently
       erroneous but which are risky or suggest there may have been an error.

       The following language-independent options do not enable specific warnings but
       control the kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond that.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a warning is
           appended, for example -Werror=switch turns the warnings controlled by -Wswitch
           into errors.  This switch takes a negative form, to be used to negate -Werror
           for specific warnings, for example -Wno-error=switch makes -Wswitch warnings
           not be errors, even when -Werror is in effect.  You can use the
           -fdiagnostics-show-option option to have each controllable warning amended with
           the option which controls it, to determine what to use with this option.

           Note that specifying -Werror=foo automatically implies -Wfoo.  However,
           -Wno-error=foo does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first error
           occurred rather than trying to keep going and printing further error messages.

       You can request many specific warnings with options beginning -W, for example
       -Wimplicit to request warnings on implicit declarations.  Each of these specific
       warning options also has a negative form beginning -Wno- to turn off warnings; for
       example, -Wno-implicit.  This manual lists only one of the two forms, whichever is
       not the default.  For further, language-specific options also refer to C++ Dialect
       Options and Objective-C and Objective-C++ Dialect Options.

       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++; reject all
           programs that use forbidden extensions, and some other programs that do not
           follow ISO C and ISO C++.  For ISO C, follows the version of the ISO C standard
           specified by any -std option used.

           Valid ISO C and ISO C++ programs should compile properly with or without this
           option (though a rare few will require -ansi or a -std option specifying the
           required version of ISO C).  However, without this option, certain GNU
           extensions and traditional C and C++ features are supported as well.  With this
           option, they are rejected.

           -pedantic does not cause warning messages for use of the alternate keywords
           whose names begin and end with __.  Pedantic warnings are also disabled in the
           expression that follows "__extension__".  However, only system header files
           should use these escape routes; application programs should avoid them.

           Some users try to use -pedantic to check programs for strict ISO C conformance.
           They soon find that it does not do quite what they want: it finds some non-ISO
           practices, but not all---only those for which ISO C requires a diagnostic, and
           some others for which diagnostics have been added.

           A feature to report any failure to conform to ISO C might be useful in some
           instances, but would require considerable additional work and would be quite
           different from -pedantic.  We don't have plans to support such a feature in the
           near future.

           Where the standard specified with -std represents a GNU extended dialect of C,
           such as gnu89 or gnu99, there is a corresponding base standard, the version of
           ISO C on which the GNU extended dialect is based.  Warnings from -pedantic are
           given where they are required by the base standard.  (It would not make sense
           for such warnings to be given only for features not in the specified GNU C
           dialect, since by definition the GNU dialects of C include all features the
           compiler supports with the given option, and there would be nothing to warn
           about.)

       -pedantic-errors
           Like -pedantic, except that errors are produced rather than warnings.

       -Wall
           This enables all the warnings about constructions that some users consider
           questionable, and that are easy to avoid (or modify to prevent the warning),
           even in conjunction with macros.  This also enables some language-specific
           warnings described in C++ Dialect Options and Objective-C and Objective-C++
           Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds (only with -O2) -Wc++0x-compat -Wchar-subscripts
           -Wimplicit-int -Wimplicit-function-declaration -Wcomment -Wformat -Wmain (only
           for C/ObjC and unless -ffreestanding) -Wmissing-braces -Wnonnull -Wparentheses
           -Wpointer-sign -Wreorder -Wreturn-type -Wsequence-point -Wsign-compare (only in
           C++) -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized
           -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value
           -Wunused-variable -Wvolatile-register-var

           Note that some warning flags are not implied by -Wall.  Some of them warn about
           constructions that users generally do not consider questionable, but which
           occasionally you might wish to check for; others warn about constructions that
           are necessary or hard to avoid in some cases, and there is no simple way to
           modify the code to suppress the warning. Some of them are enabled by -Wextra
           but many of them must be enabled individually.

       -Wextra
           This enables some extra warning flags that are not enabled by -Wall. (This
           option used to be called -W.  The older name is still supported, but the newer
           name is more descriptive.)

           -Wclobbered -Wempty-body -Wignored-qualifiers -Wmissing-field-initializers
           -Wmissing-parameter-type (C only) -Wold-style-declaration (C only)
           -Woverride-init -Wsign-compare -Wtype-limits -Wuninitialized -Wunused-parameter
           (only with -Wunused or -Wall)

           The option -Wextra also prints warning messages for the following cases:

           ?   A pointer is compared against integer zero with <, <=, >, or >=.

           ?   (C++ only) An enumerator and a non-enumerator both appear in a conditional
               expression.

           ?   (C++ only) Ambiguous virtual bases.

           ?   (C++ only) Subscripting an array which has been declared register.

           ?   (C++ only) Taking the address of a variable which has been declared
               register.

           ?   (C++ only) A base class is not initialized in a derived class' copy
               constructor.

       -Wchar-subscripts
           Warn if an array subscript has type "char".  This is a common cause of error,
           as programmers often forget that this type is signed on some machines.  This
           warning is enabled by -Wall.

       -Wcomment
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever
           a Backslash-Newline appears in a // comment.  This warning is enabled by -Wall.

       -Wformat
           Check calls to "printf" and "scanf", etc., to make sure that the arguments
           supplied have types appropriate to the format string specified, and that the
           conversions specified in the format string make sense.  This includes standard
           functions, and others specified by format attributes, in the "printf", "scanf",
           "strftime" and "strfmon" (an X/Open extension, not in the C standard) families
           (or other target-specific families).  Which functions are checked without
           format attributes having been specified depends on the standard version
           selected, and such checks of functions without the attribute specified are
           disabled by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by GNU libc
           version 2.2.  These include all ISO C90 and C99 features, as well as features
           from the Single Unix Specification and some BSD and GNU extensions.  Other
           library implementations may not support all these features; GCC does not
           support warning about features that go beyond a particular library's
           limitations.  However, if -pedantic is used with -Wformat, warnings will be
           given about format features not in the selected standard version (but not for
           "strfmon" formats, since those are not in any version of the C standard).

           Since -Wformat also checks for null format arguments for several functions,
           -Wformat also implies -Wnonnull.

           -Wformat is included in -Wall.  For more control over some aspects of format
           checking, the options -Wformat-y2k, -Wno-format-extra-args,
           -Wno-format-zero-length, -Wformat-nonliteral, -Wformat-security, and -Wformat=2
           are available, but are not included in -Wall.

       -Wformat-y2k
           If -Wformat is specified, also warn about "strftime" formats which may yield
           only a two-digit year.

       -Wno-format-contains-nul
           If -Wformat is specified, do not warn about format strings that contain NUL
           bytes.

       -Wno-format-extra-args
           If -Wformat is specified, do not warn about excess arguments to a "printf" or
           "scanf" format function.  The C standard specifies that such arguments are
           ignored.

           Where the unused arguments lie between used arguments that are specified with $
           operand number specifications, normally warnings are still given, since the
           implementation could not know what type to pass to "va_arg" to skip the unused
           arguments.  However, in the case of "scanf" formats, this option will suppress
           the warning if the unused arguments are all pointers, since the Single Unix
           Specification says that such unused arguments are allowed.

       -Wno-format-zero-length (C and Objective-C only)
           If -Wformat is specified, do not warn about zero-length formats.  The C
           standard specifies that zero-length formats are allowed.

       -Wformat-nonliteral
           If -Wformat is specified, also warn if the format string is not a string
           literal and so cannot be checked, unless the format function takes its format
           arguments as a "va_list".

       -Wformat-security
           If -Wformat is specified, also warn about uses of format functions that
           represent possible security problems.  At present, this warns about calls to
           "printf" and "scanf" functions where the format string is not a string literal
           and there are no format arguments, as in "printf (foo);".  This may be a
           security hole if the format string came from untrusted input and contains %n.
           (This is currently a subset of what -Wformat-nonliteral warns about, but in
           future warnings may be added to -Wformat-security that are not included in
           -Wformat-nonliteral.)

       -Wformat=2
           Enable -Wformat plus format checks not included in -Wformat.  Currently
           equivalent to -Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k.

       -Wnonnull (C and Objective-C only)
           Warn about passing a null pointer for arguments marked as requiring a non-null
           value by the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled with the
           -Wno-nonnull option.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables which are initialized with themselves.  Note
           this option can only be used with the -Wuninitialized option.

           For example, GCC will warn about "i" being uninitialized in the following
           snippet only when -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

       -Wimplicit-int (C and Objective-C only)
           Warn when a declaration does not specify a type.  This warning is enabled by
           -Wall.

       -Wimplicit-function-declaration (C and Objective-C only)
           Give a warning whenever a function is used before being declared. In C99 mode
           (-std=c99 or -std=gnu99), this warning is enabled by default and it is made
           into an error by -pedantic-errors. This warning is also enabled by -Wall.

       -Wimplicit
           Same as -Wimplicit-int and -Wimplicit-function-declaration.  This warning is
           enabled by -Wall.

       -Wignored-qualifiers (C and C++ only)
           Warn if the return type of a function has a type qualifier such as "const".
           For ISO C such a type qualifier has no effect, since the value returned by a
           function is not an lvalue.  For C++, the warning is only emitted for scalar
           types or "void".  ISO C prohibits qualified "void" return types on function
           definitions, so such return types always receive a warning even without this
           option.

           This warning is also enabled by -Wextra.

       -Wmain
           Warn if the type of main is suspicious.  main should be a function with
           external linkage, returning int, taking either zero arguments, two, or three
           arguments of appropriate types.  This warning is enabled by default in C++ and
           is enabled by either -Wall or -pedantic.

       -Wmissing-braces
           Warn if an aggregate or union initializer is not fully bracketed.  In the
           following example, the initializer for a is not fully bracketed, but that for b
           is fully bracketed.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wparentheses
           Warn if parentheses are omitted in certain contexts, such as when there is an
           assignment in a context where a truth value is expected, or when operators are
           nested whose precedence people often get confused about.

           Also warn if a comparison like x<=y<=z appears; this is equivalent to (x<=y ? 1
           : 0) <= z, which is a different interpretation from that of ordinary
           mathematical notation.

           Also warn about constructions where there may be confusion to which "if"
           statement an "else" branch belongs.  Here is an example of such a case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible "if" statement,
           which in this example is "if (b)".  This is often not what the programmer
           expected, as illustrated in the above example by indentation the programmer
           chose.  When there is the potential for this confusion, GCC will issue a
           warning when this flag is specified.  To eliminate the warning, add explicit
           braces around the innermost "if" statement so there is no way the "else" could
           belong to the enclosing "if".  The resulting code would look like this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of violations of
           sequence point rules in the C and C++ standards.

           The C and C++ standards defines the order in which expressions in a C/C++
           program are evaluated in terms of sequence points, which represent a partial
           ordering between the execution of parts of the program: those executed before
           the sequence point, and those executed after it.  These occur after the
           evaluation of a full expression (one which is not part of a larger expression),
           after the evaluation of the first operand of a "&&", "||", "? :" or "," (comma)
           operator, before a function is called (but after the evaluation of its
           arguments and the expression denoting the called function), and in certain
           other places.  Other than as expressed by the sequence point rules, the order
           of evaluation of subexpressions of an expression is not specified.  All these
           rules describe only a partial order rather than a total order, since, for
           example, if two functions are called within one expression with no sequence
           point between them, the order in which the functions are called is not
           specified.  However, the standards committee have ruled that function calls do
           not overlap.

           It is not specified when between sequence points modifications to the values of
           objects take effect.  Programs whose behavior depends on this have undefined
           behavior; the C and C++ standards specify that "Between the previous and next
           sequence point an object shall have its stored value modified at most once by
           the evaluation of an expression.  Furthermore, the prior value shall be read
           only to determine the value to be stored.".  If a program breaks these rules,
           the results on any particular implementation are entirely unpredictable.

           Examples of code with undefined behavior are "a = a++;", "a[n] = b[n++]" and
           "a[i++] = i;".  Some more complicated cases are not diagnosed by this option,
           and it may give an occasional false positive result, but in general it has been
           found fairly effective at detecting this sort of problem in programs.

           The standard is worded confusingly, therefore there is some debate over the
           precise meaning of the sequence point rules in subtle cases.  Links to
           discussions of the problem, including proposed formal definitions, may be found
           on the GCC readings page, at <http://gcc.gnu.org/readings.html>.

           This warning is enabled by -Wall for C and C++.

       -Wreturn-type
           Warn whenever a function is defined with a return-type that defaults to "int".
           Also warn about any "return" statement with no return-value in a function whose
           return-type is not "void" (falling off the end of the function body is
           considered returning without a value), and about a "return" statement with a
           expression in a function whose return-type is "void".

           For C++, a function without return type always produces a diagnostic message,
           even when -Wno-return-type is specified.  The only exceptions are main and
           functions defined in system headers.

           This warning is enabled by -Wall.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated type and lacks a
           "case" for one or more of the named codes of that enumeration.  (The presence
           of a "default" label prevents this warning.)  "case" labels outside the
           enumeration range also provoke warnings when this option is used.  This warning
           is enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated type and lacks a
           "case" for one or more of the named codes of that enumeration.  "case" labels
           outside the enumeration range also provoke warnings when this option is used.

       -Wsync-nand (C and C++ only)
           Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch" built-in
           functions are used.  These functions changed semantics in GCC 4.4.

       -Wtrigraphs
           Warn if any trigraphs are encountered that might change the meaning of the
           program (trigraphs within comments are not warned about).  This warning is
           enabled by -Wall.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise unused (aside
           from its declaration).

           To suppress this warning use the unused attribute.

       -Wunused-but-set-variable
           Warn whenever a local variable is assigned to, but otherwise unused (aside from
           its declaration).

           To suppress this warning use the unused attribute.

       -Wunused-function
           Warn whenever a static function is declared but not defined or a non-inline
           static function is unused.  This warning is enabled by -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is enabled by
           -Wall.

           To suppress this warning use the unused attribute.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its declaration.

           To suppress this warning use the unused attribute.

       -Wunused-variable
           Warn whenever a local variable or non-constant static variable is unused aside
           from its declaration.  This warning is enabled by -Wall.

           To suppress this warning use the unused attribute.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly not used. To
           suppress this warning cast the unused expression to void. This includes an
           expression-statement or the left-hand side of a comma expression that contains
           no side effects. For example, an expression such as x[i,j] will cause a
           warning, while x[(void)i,j] will not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In order to get a warning about an unused function parameter, you must either
           specify -Wextra -Wunused (note that -Wall implies -Wunused), or separately
           specify -Wunused-parameter.

       -Wuninitialized
           Warn if an automatic variable is used without first being initialized or if a
           variable may be clobbered by a "setjmp" call. In C++, warn if a non-static
           reference or non-static const member appears in a class without constructors.

           If you want to warn about code which uses the uninitialized value of the
           variable in its own initializer, use the -Winit-self option.

           These warnings occur for individual uninitialized or clobbered elements of
           structure, union or array variables as well as for variables which are
           uninitialized or clobbered as a whole.  They do not occur for variables or
           elements declared "volatile".  Because these warnings depend on optimization,
           the exact variables or elements for which there are warnings will depend on the
           precise optimization options and version of GCC used.

           Note that there may be no warning about a variable that is used only to compute
           a value that itself is never used, because such computations may be deleted by
           data flow analysis before the warnings are printed.

           These warnings are made optional because GCC is not smart enough to see all the
           reasons why the code might be correct despite appearing to have an error.  Here
           is one example of how this can happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If the value of "y" is always 1, 2 or 3, then "x" is always initialized, but
           GCC doesn't know this.  Here is another common case:

                   {
                     int save_y;
                     if (change_y) save_y = y, y = new_y;
                     ...
                     if (change_y) y = save_y;
                   }

           This has no bug because "save_y" is used only if it is set.

           This option also warns when a non-volatile automatic variable might be changed
           by a call to "longjmp".  These warnings as well are possible only in optimizing
           compilation.

           The compiler sees only the calls to "setjmp".  It cannot know where "longjmp"
           will be called; in fact, a signal handler could call it at any point in the
           code.  As a result, you may get a warning even when there is in fact no problem
           because "longjmp" cannot in fact be called at the place which would cause a
           problem.

           Some spurious warnings can be avoided if you declare all the functions you use
           that never return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn when a #pragma directive is encountered which is not understood by GCC.
           If this command line option is used, warnings will even be issued for unknown
           pragmas in system header files.  This is not the case if the warnings were only
           enabled by the -Wall command line option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect parameters, invalid
           syntax, or conflicts between pragmas.  See also -Wunknown-pragmas.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It warns about
           code which might break the strict aliasing rules that the compiler is using for
           optimization.  The warning does not catch all cases, but does attempt to catch
           the more common pitfalls.  It is included in -Wall.  It is equivalent to
           -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It warns about
           code which might break the strict aliasing rules that the compiler is using for
           optimization.  Higher levels correspond to higher accuracy (fewer false
           positives).  Higher levels also correspond to more effort, similar to the way
           -O works.  -Wstrict-aliasing is equivalent to -Wstrict-aliasing=n, with n=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful when higher
           levels do not warn but -fstrict-aliasing still breaks the code, as it has very
           few false negatives.  However, it has many false positives.  Warns for all
           pointer conversions between possibly incompatible types, even if never
           dereferenced.  Runs in the frontend only.

           Level 2: Aggressive, quick, not too precise.  May still have many false
           positives (not as many as level 1 though), and few false negatives (but
           possibly more than level 1).  Unlike level 1, it only warns when an address is
           taken.  Warns about incomplete types.  Runs in the frontend only.

           Level 3 (default for -Wstrict-aliasing): Should have very few false positives
           and few false negatives.  Slightly slower than levels 1 or 2 when optimization
           is enabled.  Takes care of the common punn+dereference pattern in the frontend:
           "*(int*)&some_float".  If optimization is enabled, it also runs in the backend,
           where it deals with multiple statement cases using flow-sensitive points-to
           information.  Only warns when the converted pointer is dereferenced.  Does not
           warn about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when -fstrict-overflow is active.  It warns about
           cases where the compiler optimizes based on the assumption that signed overflow
           does not occur.  Note that it does not warn about all cases where the code
           might overflow: it only warns about cases where the compiler implements some
           optimization.  Thus this warning depends on the optimization level.

           An optimization which assumes that signed overflow does not occur is perfectly
           safe if the values of the variables involved are such that overflow never does,
           in fact, occur.  Therefore this warning can easily give a false positive: a
           warning about code which is not actually a problem.  To help focus on important
           issues, several warning levels are defined.  No warnings are issued for the use
           of undefined signed overflow when estimating how many iterations a loop will
           require, in particular when determining whether a loop will be executed at all.

           -Wstrict-overflow=1
               Warn about cases which are both questionable and easy to avoid.  For
               example: "x + 1 > x"; with -fstrict-overflow, the compiler will simplify
               this to 1.  This level of -Wstrict-overflow is enabled by -Wall; higher
               levels are not, and must be explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is simplified to a constant.
               For example: "abs (x) >= 0".  This can only be simplified when
               -fstrict-overflow is in effect, because "abs (INT_MIN)" overflows to
               "INT_MIN", which is less than zero.  -Wstrict-overflow (with no level) is
               the same as -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.  For example:
               "x + 1 > 1" will be simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the above cases.  For
               example: "(x * 10) / 5" will be simplified to "x * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the magnitude of a
               constant involved in a comparison.  For example: "x + 2 > y" will be
               simplified to "x + 1 >= y".  This is reported only at the highest warning
               level because this simplification applies to many comparisons, so this
               warning level will give a very large number of false positives.

       -Warray-bounds
           This option is only active when -ftree-vrp is active (default for -O2 and
           above). It warns about subscripts to arrays that are always out of bounds. This
           warning is enabled by -Wall.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.  Floating point
           division by zero is not warned about, as it can be a legitimate way of
           obtaining infinities and NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header files.  Warnings
           from system headers are normally suppressed, on the assumption that they
           usually do not indicate real problems and would only make the compiler output
           harder to read.  Using this command line option tells GCC to emit warnings from
           system headers as if they occurred in user code.  However, note that using
           -Wall in conjunction with this option will not warn about unknown pragmas in
           system headers---for that, -Wunknown-pragmas must also be used.

       -Wfloat-equal
           Warn if floating point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the programmer) to
           consider floating-point values as approximations to infinitely precise real
           numbers.  If you are doing this, then you need to compute (by analyzing the
           code, or in some other way) the maximum or likely maximum error that the
           computation introduces, and allow for it when performing comparisons (and when
           producing output, but that's a different problem).  In particular, instead of
           testing for equality, you would check to see whether the two values have ranges
           that overlap; and this is done with the relational operators, so equality
           comparisons are probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn about certain constructs that behave differently in traditional and ISO C.
           Also warn about ISO C constructs that have no traditional C equivalent, and/or
           problematic constructs which should be avoided.

           ?   Macro parameters that appear within string literals in the macro body.  In
               traditional C macro replacement takes place within string literals, but
               does not in ISO C.

           ?   In traditional C, some preprocessor directives did not exist.  Traditional
               preprocessors would only consider a line to be a directive if the #
               appeared in column 1 on the line.  Therefore -Wtraditional warns about
               directives that traditional C understands but would ignore because the #
               does not appear as the first character on the line.  It also suggests you
               hide directives like #pragma not understood by traditional C by indenting
               them.  Some traditional implementations would not recognize #elif, so it
               suggests avoiding it altogether.

           ?   A function-like macro that appears without arguments.

           ?   The unary plus operator.

           ?   The U integer constant suffix, or the F or L floating point constant
               suffixes.  (Traditional C does support the L suffix on integer constants.)
               Note, these suffixes appear in macros defined in the system headers of most
               modern systems, e.g. the _MIN/_MAX macros in "<limits.h>".  Use of these
               macros in user code might normally lead to spurious warnings, however GCC's
               integrated preprocessor has enough context to avoid warning in these cases.

           ?   A function declared external in one block and then used after the end of
               the block.

           ?   A "switch" statement has an operand of type "long".

           ?   A non-"static" function declaration follows a "static" one.  This construct
               is not accepted by some traditional C compilers.

           ?   The ISO type of an integer constant has a different width or signedness
               from its traditional type.  This warning is only issued if the base of the
               constant is ten.  I.e. hexadecimal or octal values, which typically
               represent bit patterns, are not warned about.

           ?   Usage of ISO string concatenation is detected.

           ?   Initialization of automatic aggregates.

           ?   Identifier conflicts with labels.  Traditional C lacks a separate namespace
               for labels.

           ?   Initialization of unions.  If the initializer is zero, the warning is
               omitted.  This is done under the assumption that the zero initializer in
               user code appears conditioned on e.g. "__STDC__" to avoid missing
               initializer warnings and relies on default initialization to zero in the
               traditional C case.

           ?   Conversions by prototypes between fixed/floating point values and vice
               versa.  The absence of these prototypes when compiling with traditional C
               would cause serious problems.  This is a subset of the possible conversion
               warnings, for the full set use -Wtraditional-conversion.

           ?   Use of ISO C style function definitions.  This warning intentionally is not
               issued for prototype declarations or variadic functions because these ISO C
               features will appear in your code when using libiberty's traditional C
               compatibility macros, "PARAMS" and "VPARAMS".  This warning is also
               bypassed for nested functions because that feature is already a GCC
               extension and thus not relevant to traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn if a prototype causes a type conversion that is different from what would
           happen to the same argument in the absence of a prototype.  This includes
           conversions of fixed point to floating and vice versa, and conversions changing
           the width or signedness of a fixed point argument except when the same as the
           default promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a block.  This construct,
           known from C++, was introduced with ISO C99 and is by default allowed in GCC.
           It is not supported by ISO C90 and was not supported by GCC versions before GCC
           3.0.

       -Wundef
           Warn if an undefined identifier is evaluated in an #if directive.

       -Wno-endif-labels
           Do not warn whenever an #else or an #endif are followed by text.

       -Wshadow
           Warn whenever a local variable shadows another local variable, parameter or
           global variable or whenever a built-in function is shadowed.

       -Wlarger-than=len
           Warn whenever an object of larger than len bytes is defined.

       -Wframe-larger-than=len
           Warn if the size of a function frame is larger than len bytes.  The computation
           done to determine the stack frame size is approximate and not conservative.
           The actual requirements may be somewhat greater than len even if you do not get
           a warning.  In addition, any space allocated via "alloca", variable-length
           arrays, or related constructs is not included by the compiler when determining
           whether or not to issue a warning.

       -Wunsafe-loop-optimizations
           Warn if the loop cannot be optimized because the compiler could not assume
           anything on the bounds of the loop indices.  With -funsafe-loop-optimizations
           warn if the compiler made such assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           Disables the warnings about non-ISO "printf" / "scanf" format width specifiers
           "I32", "I64", and "I" used on Windows targets depending on the MS runtime, when
           you are using the options -Wformat and -pedantic without gnu-extensions.

       -Wpointer-arith
           Warn about anything that depends on the "size of" a function type or of "void".
           GNU C assigns these types a size of 1, for convenience in calculations with
           "void *" pointers and pointers to functions.  In C++, warn also when an
           arithmetic operation involves "NULL".  This warning is also enabled by
           -pedantic.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the limited range of
           the data type, but do not warn for constant expressions.  For example, warn if
           an unsigned variable is compared against zero with < or >=.  This warning is
           also enabled by -Wextra.

       -Wbad-function-cast (C and Objective-C only)
           Warn whenever a function call is cast to a non-matching type.  For example,
           warn if "int malloc()" is cast to "anything *".

       -Wc++-compat (C and Objective-C only)
           Warn about ISO C constructs that are outside of the common subset of ISO C and
           ISO C++, e.g. request for implicit conversion from "void *" to a pointer to
           non-"void" type.

       -Wc++0x-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO
           C++ 200x, e.g., identifiers in ISO C++ 1998 that will become keywords in ISO
           C++ 200x.  This warning is enabled by -Wall.

       -Wcast-qual
           Warn whenever a pointer is cast so as to remove a type qualifier from the
           target type.  For example, warn if a "const char *" is cast to an ordinary
           "char *".

       -Wcast-align
           Warn whenever a pointer is cast such that the required alignment of the target
           is increased.  For example, warn if a "char *" is cast to an "int *" on
           machines where integers can only be accessed at two- or four-byte boundaries.

       -Wwrite-strings
           When compiling C, give string constants the type "const char[length]" so that
           copying the address of one into a non-"const" "char *" pointer will get a
           warning.  These warnings will help you find at compile time code that can try
           to write into a string constant, but only if you have been very careful about
           using "const" in declarations and prototypes.  Otherwise, it will just be a
           nuisance. This is why we did not make -Wall request these warnings.

           When compiling C++, warn about the deprecated conversion from string literals
           to "char *".  This warning is enabled by default for C++ programs.

       -Wclobbered
           Warn for variables that might be changed by longjmp or vfork.  This warning is
           also enabled by -Wextra.

       -Wconversion
           Warn for implicit conversions that may alter a value. This includes conversions
           between real and integer, like "abs (x)" when "x" is "double"; conversions
           between signed and unsigned, like "unsigned ui = -1"; and conversions to
           smaller types, like "sqrtf (M_PI)". Do not warn for explicit casts like "abs
           ((int) x)" and "ui = (unsigned) -1", or if the value is not changed by the
           conversion like in "abs (2.0)".  Warnings about conversions between signed and
           unsigned integers can be disabled by using -Wno-sign-conversion.

           For C++, also warn for conversions between "NULL" and non-pointer types;
           confusing overload resolution for user-defined conversions; and conversions
           that will never use a type conversion operator: conversions to "void", the same
           type, a base class or a reference to them. Warnings about conversions between
           signed and unsigned integers are disabled by default in C++ unless
           -Wsign-conversion is explicitly enabled.

       -Wempty-body
           Warn if an empty body occurs in an if, else or do while statement.  This
           warning is also enabled by -Wextra.

       -Wenum-compare (C++ and Objective-C++ only)
           Warn about a comparison between values of different enum types. This warning is
           enabled by default.

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could produce an
           incorrect result when the signed value is converted to unsigned.  This warning
           is also enabled by -Wextra; to get the other warnings of -Wextra without this
           warning, use -Wextra -Wno-sign-compare.

       -Wsign-conversion
           Warn for implicit conversions that may change the sign of an integer value,
           like assigning a signed integer expression to an unsigned integer variable. An
           explicit cast silences the warning. In C, this option is enabled also by
           -Wconversion.

       -Waddress
           Warn about suspicious uses of memory addresses. These include using the address
           of a function in a conditional expression, such as "void func(void); if
           (func)", and comparisons against the memory address of a string literal, such
           as "if (x == "abc")".  Such uses typically indicate a programmer error: the
           address of a function always evaluates to true, so their use in a conditional
           usually indicate that the programmer forgot the parentheses in a function call;
           and comparisons against string literals result in unspecified behavior and are
           not portable in C, so they usually indicate that the programmer intended to use
           "strcmp".  This warning is enabled by -Wall.

       -Wlogical-op
           Warn about suspicious uses of logical operators in expressions.  This includes
           using logical operators in contexts where a bit-wise operator is likely to be
           expected.

       -Waggregate-return
           Warn if any functions that return structures or unions are defined or called.
           (In languages where you can return an array, this also elicits a warning.)

       -Wno-attributes
           Do not warn if an unexpected "__attribute__" is used, such as unrecognized
           attributes, function attributes applied to variables, etc.  This will not stop
           errors for incorrect use of supported attributes.

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros are redefined.  This suppresses warnings
           for redefinition of "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and
           "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn if a function is declared or defined without specifying the argument
           types.  (An old-style function definition is permitted without a warning if
           preceded by a declaration which specifies the argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a declaration. For
           example, warn if storage-class specifiers like "static" are not the first
           things in a declaration.  This warning is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn if an old-style function definition is used.  A warning is given even if
           there is a previous prototype.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in K&R-style
           functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn if a global function is defined without a previous prototype declaration.
           This warning is issued even if the definition itself provides a prototype.  The
           aim is to detect global functions that fail to be declared in header files.

       -Wmissing-declarations
           Warn if a global function is defined without a previous declaration.  Do so
           even if the definition itself provides a prototype.  Use this option to detect
           global functions that are not declared in header files.  In C++, no warnings
           are issued for function templates, or for inline functions, or for functions in
           anonymous namespaces.

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For example, the
           following code would cause such a warning, because "x.h" is implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so the following
           modification would not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           This warning is included in -Wextra.  To get other -Wextra warnings without
           this one, use -Wextra -Wno-missing-field-initializers.

       -Wmissing-noreturn
           Warn about functions which might be candidates for attribute "noreturn".  Note
           these are only possible candidates, not absolute ones.  Care should be taken to
           manually verify functions actually do not ever return before adding the
           "noreturn" attribute, otherwise subtle code generation bugs could be
           introduced.  You will not get a warning for "main" in hosted C environments.

       -Wmissing-format-attribute
           Warn about function pointers which might be candidates for "format" attributes.
           Note these are only possible candidates, not absolute ones.  GCC will guess
           that function pointers with "format" attributes that are used in assignment,
           initialization, parameter passing or return statements should have a
           corresponding "format" attribute in the resulting type.  I.e. the left-hand
           side of the assignment or initialization, the type of the parameter variable,
           or the return type of the containing function respectively should also have a
           "format" attribute to avoid the warning.

           GCC will also warn about function definitions which might be candidates for
           "format" attributes.  Again, these are only possible candidates.  GCC will
           guess that "format" attributes might be appropriate for any function that calls
           a function like "vprintf" or "vscanf", but this might not always be the case,
           and some functions for which "format" attributes are appropriate may not be
           detected.

       -Wno-multichar
           Do not warn if a multicharacter constant ('FOOF') is used.  Usually they
           indicate a typo in the user's code, as they have implementation-defined values,
           and should not be used in portable code.

       -Wnormalized=<none|id|nfc|nfkc>
           In ISO C and ISO C++, two identifiers are different if they are different
           sequences of characters.  However, sometimes when characters outside the basic
           ASCII character set are used, you can have two different character sequences
           that look the same.  To avoid confusion, the ISO 10646 standard sets out some
           normalization rules which when applied ensure that two sequences that look the
           same are turned into the same sequence.  GCC can warn you if you are using
           identifiers which have not been normalized; this option controls that warning.

           There are four levels of warning that GCC supports.  The default is
           -Wnormalized=nfc, which warns about any identifier which is not in the ISO
           10646 "C" normalized form, NFC.  NFC is the recommended form for most uses.

           Unfortunately, there are some characters which ISO C and ISO C++ allow in
           identifiers that when turned into NFC aren't allowable as identifiers.  That
           is, there's no way to use these symbols in portable ISO C or C++ and have all
           your identifiers in NFC.  -Wnormalized=id suppresses the warning for these
           characters.  It is hoped that future versions of the standards involved will
           correct this, which is why this option is not the default.

           You can switch the warning off for all characters by writing -Wnormalized=none.
           You would only want to do this if you were using some other normalization
           scheme (like "D"), because otherwise you can easily create bugs that are
           literally impossible to see.

           Some characters in ISO 10646 have distinct meanings but look identical in some
           fonts or display methodologies, especially once formatting has been applied.
           For instance "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N", will display just
           like a regular "n" which has been placed in a superscript.  ISO 10646 defines
           the NFKC normalization scheme to convert all these into a standard form as
           well, and GCC will warn if your code is not in NFKC if you use
           -Wnormalized=nfkc.  This warning is comparable to warning about every
           identifier that contains the letter O because it might be confused with the
           digit 0, and so is not the default, but may be useful as a local coding
           convention if the programming environment is unable to be fixed to display
           these characters distinctly.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do not warn about uses of functions, variables, and types marked as deprecated
           by using the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is overridden when using
           designated initializers.

           This warning is included in -Wextra.  To get other -Wextra warnings without
           this one, use -Wextra -Wno-override-init.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed attribute has
           no effect on the layout or size of the structure.  Such structures may be mis-
           aligned for little benefit.  For instance, in this code, the variable "f.x" in
           "struct bar" will be misaligned even though "struct bar" does not itself have
           the packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wpacked-bitfield-compat
           The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on bit-fields
           of type "char".  This has been fixed in GCC 4.4 but the change can lead to
           differences in the structure layout.  GCC informs you when the offset of such a
           field has changed in GCC 4.4.  For example there is no longer a 4-bit padding
           between field "a" and "b" in this structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This warning is enabled by default.  Use -Wno-packed-bitfield-compat to disable
           this warning.

       -Wpadded
           Warn if padding is included in a structure, either to align an element of the
           structure or to align the whole structure.  Sometimes when this happens it is
           possible to rearrange the fields of the structure to reduce the padding and so
           make the structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in the same scope, even in cases
           where multiple declaration is valid and changes nothing.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Wunreachable-code
           Warn if the compiler detects that code will never be executed.

           This option is intended to warn when the compiler detects that at least a whole
           line of source code will never be executed, because some condition is never
           satisfied or because it is after a procedure that never returns.

           It is possible for this option to produce a warning even though there are
           circumstances under which part of the affected line can be executed, so care
           should be taken when removing apparently-unreachable code.

           For instance, when a function is inlined, a warning may mean that the line is
           unreachable in only one inlined copy of the function.

           This option is not made part of -Wall because in a debugging version of a
           program there is often substantial code which checks correct functioning of the
           program and is, hopefully, unreachable because the program does work.  Another
           common use of unreachable code is to provide behavior which is selectable at
           compile-time.

       -Winline
           Warn if a function can not be inlined and it was declared as inline.  Even with
           this option, the compiler will not warn about failures to inline functions
           declared in system headers.

           The compiler uses a variety of heuristics to determine whether or not to inline
           a function.  For example, the compiler takes into account the size of the
           function being inlined and the amount of inlining that has already been done in
           the current function.  Therefore, seemingly insignificant changes in the source
           program can cause the warnings produced by -Winline to appear or disappear.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the offsetof macro to a non-POD type.
           According to the 1998 ISO C++ standard, applying offsetof to a non-POD type is
           undefined.  In existing C++ implementations, however, offsetof typically gives
           meaningful results even when applied to certain kinds of non-POD types. (Such
           as a simple struct that fails to be a POD type only by virtue of having a
           constructor.)  This flag is for users who are aware that they are writing
           nonportable code and who have deliberately chosen to ignore the warning about
           it.

           The restrictions on offsetof may be relaxed in a future version of the C++
           standard.

       -Wno-int-to-pointer-cast (C and Objective-C only)
           Suppress warnings from casts to pointer type of an integer of a different size.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of a different
           size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but can't be used.

       -Wlong-long
           Warn if long long type is used.  This is default.  To inhibit the warning
           messages, use -Wno-long-long.  Flags -Wlong-long and -Wno-long-long are taken
           into account only when -pedantic flag is used.

       -Wvariadic-macros
           Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU alternate
           syntax when in pedantic ISO C99 mode.  This is default.  To inhibit the warning
           messages, use -Wno-variadic-macros.

       -Wvla
           Warn if variable length array is used in the code.  -Wno-vla will prevent the
           -pedantic warning of the variable length array.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile modifier does
           not inhibit all optimizations that may eliminate reads and/or writes to
           register variables.  This warning is enabled by -Wall.

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning does not
           generally indicate that there is anything wrong with your code; it merely
           indicates that GCC's optimizers were unable to handle the code effectively.
           Often, the problem is that your code is too big or too complex; GCC will refuse
           to optimize programs when the optimization itself is likely to take inordinate
           amounts of time.

       -Wpointer-sign (C and Objective-C only)
           Warn for pointer argument passing or assignment with different signedness.
           This option is only supported for C and Objective-C.  It is implied by -Wall
           and by -pedantic, which can be disabled with -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It warns about
           functions that will not be protected against stack smashing.

       -Wno-mudflap
           Suppress warnings about constructs that cannot be instrumented by -fmudflap.

       -Woverlength-strings
           Warn about string constants which are longer than the "minimum maximum" length
           specified in the C standard.  Modern compilers generally allow string constants
           which are much longer than the standard's minimum limit, but very portable
           programs should avoid using longer strings.

           The limit applies after string constant concatenation, and does not count the
           trailing NUL.  In C89, the limit was 509 characters; in C99, it was raised to
           4095.  C++98 does not specify a normative minimum maximum, so we do not
           diagnose overlength strings in C++.

           This option is implied by -pedantic, and can be disabled with
           -Wno-overlength-strings.

   Options for Debugging Your Program or GCC
       GCC has various special options that are used for debugging either your program or
       GCC:

       -g  Produce debugging information in the operating system's native format (stabs,
           COFF, XCOFF, or DWARF 2).  GDB can work with this debugging information.

           On most systems that use stabs format, -g enables use of extra debugging
           information that only GDB can use; this extra information makes debugging work
           better in GDB but will probably make other debuggers crash or refuse to read
           the program.  If you want to control for certain whether to generate the extra
           information, use -gstabs+, -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

           GCC allows you to use -g with -O.  The shortcuts taken by optimized code may
           occasionally produce surprising results: some variables you declared may not
           exist at all; flow of control may briefly move where you did not expect it;
           some statements may not be executed because they compute constant results or
           their values were already at hand; some statements may execute in different
           places because they were moved out of loops.

           Nevertheless it proves possible to debug optimized output.  This makes it
           reasonable to use the optimizer for programs that might have bugs.

           The following options are useful when GCC is generated with the capability for
           more than one debugging format.

       -ggdb
           Produce debugging information for use by GDB.  This means to use the most
           expressive format available (DWARF 2, stabs, or the native format if neither of
           those are supported), including GDB extensions if at all possible.

       -gstabs
           Produce debugging information in stabs format (if that is supported), without
           GDB extensions.  This is the format used by DBX on most BSD systems.  On MIPS,
           Alpha and System V Release 4 systems this option produces stabs debugging
           output which is not understood by DBX or SDB.  On System V Release 4 systems
           this option requires the GNU assembler.

       -feliminate-unused-debug-symbols
           Produce debugging information in stabs format (if that is supported), for only
           symbols that are actually used.

       -femit-class-debug-always
           Instead of emitting debugging information for a C++ class in only one object
           file, emit it in all object files using the class.  This option should be used
           only with debuggers that are unable to handle the way GCC normally emits
           debugging information for classes because using this option will increase the
           size of debugging information by as much as a factor of two.

       -gstabs+
           Produce debugging information in stabs format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these
           extensions is likely to make other debuggers crash or refuse to read the
           program.

       -gcoff
           Produce debugging information in COFF format (if that is supported).  This is
           the format used by SDB on most System V systems prior to System V Release 4.

       -gxcoff
           Produce debugging information in XCOFF format (if that is supported).  This is
           the format used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
           Produce debugging information in XCOFF format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these
           extensions is likely to make other debuggers crash or refuse to read the
           program, and may cause assemblers other than the GNU assembler (GAS) to fail
           with an error.

       -gdwarf-version
           Produce debugging information in DWARF format (if that is supported).  This is
           the format used by DBX on IRIX 6.  The value of version may be either 2 or 3;
           the default version is 3.

           Note that with DWARF version 2 some ports require, and will always use, some
           non-conflicting DWARF 3 extensions in the unwind tables.

       -gstrict-dwarf
           Disallow using extensions of later DWARF standard version than selected with
           -gdwarf-version.  On most targets using non-conflicting DWARF extensions from
           later standard versions is allowed.

       -gno-strict-dwarf
           Allow using extensions of later DWARF standard version than selected with
           -gdwarf-version.

       -gvms
           Produce debugging information in VMS debug format (if that is supported).  This
           is the format used by DEBUG on VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel
       -gxcofflevel
       -gvmslevel
           Request debugging information and also use level to specify how much
           information.  The default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates -g.

           Level 1 produces minimal information, enough for making backtraces in parts of
           the program that you don't plan to debug.  This includes descriptions of
           functions and external variables, but no information about local variables and
           no line numbers.

           Level 3 includes extra information, such as all the macro definitions present
           in the program.  Some debuggers support macro expansion when you use -g3.

           -gdwarf-2 does not accept a concatenated debug level, because GCC used to
           support an option -gdwarf that meant to generate debug information in version 1
           of the DWARF format (which is very different from version 2), and it would have
           been too confusing.  That debug format is long obsolete, but the option cannot
           be changed now.  Instead use an additional -glevel option to change the debug
           level for DWARF.

       -gtoggle
           Turn off generation of debug info, if leaving out this option would have
           generated it, or turn it on at level 2 otherwise.  The position of this
           argument in the command line does not matter, it takes effect after all other
           options are processed, and it does so only once, no matter how many times it is
           given.  This is mainly intended to be used with -fcompare-debug.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL) to file.  If the optional argument
           is omitted (or if file is "."), the name of the dump file will be determined by
           appending ".gkd" to the compilation output file name.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second time, adding
           opts and -fcompare-debug-second to the arguments passed to the second
           compilation.  Dump the final internal representation in both compilations, and
           print an error if they differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and nonzero,
           implicitly enables -fcompare-debug.  If GCC_COMPARE_DEBUG is defined to a
           string starting with a dash, then it is used for opts, otherwise the default
           -gtoggle is used.

           -fcompare-debug=, with the equal sign but without opts, is equivalent to
           -fno-compare-debug, which disables the dumping of the final representation and
           the second compilation, preventing even GCC_COMPARE_DEBUG from taking effect.

           To verify full coverage during -fcompare-debug testing, set GCC_COMPARE_DEBUG
           to say -fcompare-debug-not-overridden, which GCC will reject as an invalid
           option in any actual compilation (rather than preprocessing, assembly or
           linking).  To get just a warning, setting GCC_COMPARE_DEBUG to
           -w%n-fcompare-debug not overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second compilation
           requested by -fcompare-debug, along with options to silence warnings, and
           omitting other options that would cause side-effect compiler outputs to files
           or to the standard output.  Dump files and preserved temporary files are
           renamed so as to contain the ".gk" additional extension during the second
           compilation, to avoid overwriting those generated by the first.

           When this option is passed to the compiler driver, it causes the first
           compilation to be skipped, which makes it useful for little other than
           debugging the compiler proper.

       -feliminate-dwarf2-dups
           Compress DWARF2 debugging information by eliminating duplicated information
           about each symbol.  This option only makes sense when generating DWARF2
           debugging information with -gdwarf-2.

       -femit-struct-debug-baseonly
           Emit debug information for struct-like types only when the base name of the
           compilation source file matches the base name of file in which the struct was
           defined.

           This option substantially reduces the size of debugging information, but at
           significant potential loss in type information to the debugger.  See
           -femit-struct-debug-reduced for a less aggressive option.  See
           -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF 2.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base name of the
           compilation source file matches the base name of file in which the type was
           defined, unless the struct is a template or defined in a system header.

           This option significantly reduces the size of debugging information, with some
           potential loss in type information to the debugger.  See
           -femit-struct-debug-baseonly for a more aggressive option.  See
           -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF 2.

       -femit-struct-debug-detailed[=spec-list]
           Specify the struct-like types for which the compiler will generate debug
           information.  The intent is to reduce duplicate struct debug information
           between different object files within the same program.

           This option is a detailed version of -femit-struct-debug-reduced and
           -femit-struct-debug-baseonly, which will serve for most needs.

           A specification has the syntax [dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that are used
           directly (dir:) or used indirectly (ind:).  A struct type is used directly when
           it is the type of a variable, member.  Indirect uses arise through pointers to
           structs.  That is, when use of an incomplete struct would be legal, the use is
           indirect.  An example is struct one direct; struct two * indirect;.

           The optional second word limits the specification to ordinary structs (ord:) or
           generic structs (gen:).  Generic structs are a bit complicated to explain.  For
           C++, these are non-explicit specializations of template classes, or non-
           template classes within the above.  Other programming languages have generics,
           but -femit-struct-debug-detailed does not yet implement them.

           The third word specifies the source files for those structs for which the
           compiler will emit debug information.  The values none and any have the normal
           meaning.  The value base means that the base of name of the file in which the
           type declaration appears must match the base of the name of the main
           compilation file.  In practice, this means that types declared in foo.c and
           foo.h will have debug information, but types declared in other header will not.
           The value sys means those types satisfying base or declared in system or
           compiler headers.

           You may need to experiment to determine the best settings for your application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF 2.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging information
           which are identical in different object files.  Merging is not supported by all
           assemblers or linkers.  Merging decreases the size of the debug information in
           the output file at the cost of increasing link processing time.  Merging is
           enabled by default.

       -fdebug-prefix-map=old=new
           When compiling files in directory old, record debugging information describing
           them as in new instead.

       -fno-dwarf2-cfi-asm
           Emit DWARF 2 unwind info as compiler generated ".eh_frame" section instead of
           using GAS ".cfi_*" directives.

       -p  Generate extra code to write profile information suitable for the analysis
           program prof.  You must use this option when compiling the source files you
           want data about, and you must also use it when linking.

       -pg Generate extra code to write profile information suitable for the analysis
           program gprof.  You must use this option when compiling the source files you
           want data about, and you must also use it when linking.

       -Q  Makes the compiler print out each function name as it is compiled, and print
           some statistics about each pass when it finishes.

       -ftime-report
           Makes the compiler print some statistics about the time consumed by each pass
           when it finishes.

       -fmem-report
           Makes the compiler print some statistics about permanent memory allocation when
           it finishes.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes the compiler print some statistics about permanent memory allocation
           before or after interprocedural optimization.

       -fprofile-arcs
           Add code so that program flow arcs are instrumented.  During execution the
           program records how many times each branch and call is executed and how many
           times it is taken or returns.  When the compiled program exits it saves this
           data to a file called auxname.gcda for each source file.  The data may be used
           for profile-directed optimizations (-fbranch-probabilities), or for test
           coverage analysis (-ftest-coverage).  Each object file's auxname is generated
           from the name of the output file, if explicitly specified and it is not the
           final executable, otherwise it is the basename of the source file.  In both
           cases any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or
           dir/foo.gcda for output file specified as -o dir/foo.o).

       --coverage
           This option is used to compile and link code instrumented for coverage
           analysis.  The option is a synonym for -fprofile-arcs -ftest-coverage (when
           compiling) and -lgcov (when linking).  See the documentation for those options
           for more details.

           ?   Compile the source files with -fprofile-arcs plus optimization and code
               generation options.  For test coverage analysis, use the additional
               -ftest-coverage option.  You do not need to profile every source file in a
               program.

           ?   Link your object files with -lgcov or -fprofile-arcs (the latter implies
               the former).

           ?   Run the program on a representative workload to generate the arc profile
               information.  This may be repeated any number of times.  You can run
               concurrent instances of your program, and provided that the file system
               supports locking, the data files will be correctly updated.  Also "fork"
               calls are detected and correctly handled (double counting will not happen).

           ?   For profile-directed optimizations, compile the source files again with the
               same optimization and code generation options plus -fbranch-probabilities.

           ?   For test coverage analysis, use gcov to produce human readable information
               from the .gcno and .gcda files.  Refer to the gcov documentation for
               further information.

           With -fprofile-arcs, for each function of your program GCC creates a program
           flow graph, then finds a spanning tree for the graph.  Only arcs that are not
           on the spanning tree have to be instrumented: the compiler adds code to count
           the number of times that these arcs are executed.  When an arc is the only exit
           or only entrance to a block, the instrumentation code can be added to the
           block; otherwise, a new basic block must be created to hold the instrumentation
           code.

       -ftest-coverage
           Produce a notes file that the gcov code-coverage utility can use to show
           program coverage.  Each source file's note file is called auxname.gcno.  Refer
           to the -fprofile-arcs option above for a description of auxname and
           instructions on how to generate test coverage data.  Coverage data will match
           the source files more closely, if you do not optimize.

       -fdbg-cnt-list
           Print the name and the counter upperbound for all debug counters.

       -fdbg-cnt=counter-value-list
           Set the internal debug counter upperbound. counter-value-list is a comma-
           separated list of name:value pairs which sets the upperbound of each debug
           counter name to value.  All debug counters have the initial upperbound of
           UINT_MAX, thus dbg_cnt() returns true always unless the upperbound is set by
           this option.  e.g. With -fdbg-cnt=dce:10,tail_call:0 dbg_cnt(dce) will return
           true only for first 10 invocations and dbg_cnt(tail_call) will return false
           always.

       -dletters
       -fdump-rtl-pass
           Says to make debugging dumps during compilation at times specified by letters.
           This is used for debugging the RTL-based passes of the compiler.  The file
           names for most of the dumps are made by appending a pass number and a word to
           the dumpname.  dumpname is generated from the name of the output file, if
           explicitly specified and it is not an executable, otherwise it is the basename
           of the source file. These switches may have different effects when -E is used
           for preprocessing.

           Debug dumps can be enabled with a -fdump-rtl switch or some -d option letters.
           Here are the possible letters for use in pass and letters, and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on architectures
               that have auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the two branch
               target load optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping after the
               three if conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two common
               sub-expression elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the two dead store
               elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after the two
               forward propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after global common
               subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop optimization passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization pass, if that
               pass exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function pro and epilogues.

           -fdump-rtl-regmove
               Dump after the register move pass.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the basic
               block scheduling passes.

           -fdump-rtl-see
               Dump after sign extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               -fdump-rtl-split1, -fdump-rtl-split2, -fdump-rtl-split3, -fdump-rtl-split4
               and -fdump-rtl-split5 enable dumping after five rounds of instruction
               splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some architectures.

           -fdump-rtl-stack
               Dump after conversion from GCC's "flat register file" registers to the
               x87's stack-like registers.  This pass is only run on x86 variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after the two
               subreg expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging information.

           -dD Dump all macro definitions, at the end of preprocessing, in addition to
               normal output.

           -dH Produce a core dump whenever an error occurs.

           -dm Print statistics on memory usage, at the end of the run, to standard error.

           -dp Annotate the assembler output with a comment indicating which pattern and
               alternative was used.  The length of each instruction is also printed.

           -dP Dump the RTL in the assembler output as a comment before each instruction.
               Also turns on -dp annotation.

           -dv For each of the other indicated dump files (-fdump-rtl-pass), dump a
               representation of the control flow graph suitable for viewing with VCG to
               file.pass.vcg.

           -dx Just generate RTL for a function instead of compiling it.  Usually used
               with -fdump-rtl-expand.

           -dy Dump debugging information during parsing, to standard error.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes it more
           feasible to use diff on debugging dumps for compiler invocations with different
           compiler binaries and/or different text / bss / data / heap / stack / dso start
           locations.

       -fdump-unnumbered
           When doing debugging dumps, suppress instruction numbers and address output.
           This makes it more feasible to use diff on debugging dumps for compiler
           invocations with different options, in particular with and without -g.

       -fdump-unnumbered-links
           When doing debugging dumps (see -d option above), suppress instruction numbers
           for the links to the previous and next instructions in a sequence.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
           Dump a representation of the tree structure for the entire translation unit to
           a file.  The file name is made by appending .tu to the source file name.  If
           the -options form is used, options controls the details of the dump as
           described for the -fdump-tree options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
           Dump a representation of each class's hierarchy and virtual function table
           layout to a file.  The file name is made by appending .class to the source file
           name.  If the -options form is used, options controls the details of the dump
           as described for the -fdump-tree options.

       -fdump-ipa-switch
           Control the dumping at various stages of inter-procedural analysis language
           tree to a file.  The file name is generated by appending a switch specific
           suffix to the source file name.  The following dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps information about call-graph optimization, unused function removal,
               and inlining decisions.

           inline
               Dump after function inlining.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a separate file.  The file
           name is generated by appending a suffix ending in .statistics to the source
           file name.  If the -option form is used, -stats will cause counters to be
           summed over the whole compilation unit while -details will dump every event as
           the passes generate them.  The default with no option is to sum counters for
           each function compiled.

       -fdump-tree-switch
       -fdump-tree-switch-options
           Control the dumping at various stages of processing the intermediate language
           tree to a file.  The file name is generated by appending a switch specific
           suffix to the source file name.  If the -options form is used, options is a
           list of - separated options that control the details of the dump.  Not all
           options are applicable to all dumps, those which are not meaningful will be
           ignored.  The following options are available

           address
               Print the address of each node.  Usually this is not meaningful as it
               changes according to the environment and source file.  Its primary use is
               for tying up a dump file with a debug environment.

           slim
               Inhibit dumping of members of a scope or body of a function merely because
               that scope has been reached.  Only dump such items when they are directly
               reachable by some other path.  When dumping pretty-printed trees, this
               option inhibits dumping the bodies of control structures.

           raw Print a raw representation of the tree.  By default, trees are pretty-
               printed into a C-like representation.

           details
               Enable more detailed dumps (not honored by every dump option).

           stats
               Enable dumping various statistics about the pass (not honored by every dump
               option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           all Turn on all options, except raw, slim, verbose and lineno.

           The following tree dumps are possible:

           original
               Dump before any tree based optimization, to file.original.

           optimized
               Dump after all tree based optimization, to file.optimized.

           gimple
               Dump each function before and after the gimplification pass to a file.  The
               file name is made by appending .gimple to the source file name.

           cfg Dump the control flow graph of each function to a file.  The file name is
               made by appending .cfg to the source file name.

           vcg Dump the control flow graph of each function to a file in VCG format.  The
               file name is made by appending .vcg to the source file name.  Note that if
               the file contains more than one function, the generated file cannot be used
               directly by VCG.  You will need to cut and paste each function's graph into
               its own separate file first.

           ch  Dump each function after copying loop headers.  The file name is made by
               appending .ch to the source file name.

           ssa Dump SSA related information to a file.  The file name is made by appending
               .ssa to the source file name.

           alias
               Dump aliasing information for each function.  The file name is made by
               appending .alias to the source file name.

           ccp Dump each function after CCP.  The file name is made by appending .ccp to
               the source file name.

           storeccp
               Dump each function after STORE-CCP.  The file name is made by appending
               .storeccp to the source file name.

           pre Dump trees after partial redundancy elimination.  The file name is made by
               appending .pre to the source file name.

           fre Dump trees after full redundancy elimination.  The file name is made by
               appending .fre to the source file name.

           copyprop
               Dump trees after copy propagation.  The file name is made by appending
               .copyprop to the source file name.

           store_copyprop
               Dump trees after store copy-propagation.  The file name is made by
               appending .store_copyprop to the source file name.

           dce Dump each function after dead code elimination.  The file name is made by
               appending .dce to the source file name.

           mudflap
               Dump each function after adding mudflap instrumentation.  The file name is
               made by appending .mudflap to the source file name.

           sra Dump each function after performing scalar replacement of aggregates.  The
               file name is made by appending .sra to the source file name.

           sink
               Dump each function after performing code sinking.  The file name is made by
               appending .sink to the source file name.

           dom Dump each function after applying dominator tree optimizations.  The file
               name is made by appending .dom to the source file name.

           dse Dump each function after applying dead store elimination.  The file name is
               made by appending .dse to the source file name.

           phiopt
               Dump each function after optimizing PHI nodes into straightline code.  The
               file name is made by appending .phiopt to the source file name.

           forwprop
               Dump each function after forward propagating single use variables.  The
               file name is made by appending .forwprop to the source file name.

           copyrename
               Dump each function after applying the copy rename optimization.  The file
               name is made by appending .copyrename to the source file name.

           nrv Dump each function after applying the named return value optimization on
               generic trees.  The file name is made by appending .nrv to the source file
               name.

           vect
               Dump each function after applying vectorization of loops.  The file name is
               made by appending .vect to the source file name.

           vrp Dump each function after Value Range Propagation (VRP).  The file name is
               made by appending .vrp to the source file name.

           all Enable all the available tree dumps with the flags provided in this option.

       -ftree-vectorizer-verbose=n
           This option controls the amount of debugging output the vectorizer prints.
           This information is written to standard error, unless -fdump-tree-all or
           -fdump-tree-vect is specified, in which case it is output to the usual dump
           listing file, .vect.  For n=0 no diagnostic information is reported.  If n=1
           the vectorizer reports each loop that got vectorized, and the total number of
           loops that got vectorized.  If n=2 the vectorizer also reports non-vectorized
           loops that passed the first analysis phase (vect_analyze_loop_form) - i.e.
           countable, inner-most, single-bb, single-entry/exit loops.  This is the same
           verbosity level that -fdump-tree-vect-stats uses.  Higher verbosity levels mean
           either more information dumped for each reported loop, or same amount of
           information reported for more loops: If n=3, alignment related information is
           added to the reports.  If n=4, data-references related information (e.g. memory
           dependences, memory access-patterns) is added to the reports.  If n=5, the
           vectorizer reports also non-vectorized inner-most loops that did not pass the
           first analysis phase (i.e., may not be countable, or may have complicated
           control-flow).  If n=6, the vectorizer reports also non-vectorized nested
           loops.  For n=7, all the information the vectorizer generates during its
           analysis and transformation is reported.  This is the same verbosity level that
           -fdump-tree-vect-details uses.

       -frandom-seed=string
           This option provides a seed that GCC uses when it would otherwise use random
           numbers.  It is used to generate certain symbol names that have to be different
           in every compiled file.  It is also used to place unique stamps in coverage
           data files and the object files that produce them.  You can use the
           -frandom-seed option to produce reproducibly identical object files.

           The string should be different for every file you compile.

       -fsched-verbose=n
           On targets that use instruction scheduling, this option controls the amount of
           debugging output the scheduler prints.  This information is written to standard
           error, unless -fdump-rtl-sched1 or -fdump-rtl-sched2 is specified, in which
           case it is output to the usual dump listing file, .sched or .sched2
           respectively.  However for n greater than nine, the output is always printed to
           standard error.

           For n greater than zero, -fsched-verbose outputs the same information as
           -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n greater than one, it also
           output basic block probabilities, detailed ready list information and unit/insn
           info.  For n greater than two, it includes RTL at abort point, control-flow and
           regions info.  And for n over four, -fsched-verbose also includes dependence
           info.

       -save-temps
           Store the usual "temporary" intermediate files permanently; place them in the
           current directory and name them based on the source file.  Thus, compiling
           foo.c with -c -save-temps would produce files foo.i and foo.s, as well as
           foo.o.  This creates a preprocessed foo.i output file even though the compiler
           now normally uses an integrated preprocessor.

           When used in combination with the -x command line option, -save-temps is
           sensible enough to avoid over writing an input source file with the same
           extension as an intermediate file.  The corresponding intermediate file may be
           obtained by renaming the source file before using -save-temps.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation sequence.  For
           C source files, this is the compiler proper and assembler (plus the linker if
           linking is done).

           Without the specification of an output file, the output looks like this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The first number on each line is the "user time", that is time spent executing
           the program itself.  The second number is "system time", time spent executing
           operating system routines on behalf of the program.  Both numbers are in
           seconds.

           With the specification of an output file, the output is appended to the named
           file, and it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the program name, and
           the options passed to the program are displayed, so that one can later tell
           what file was being compiled, and with which options.

       -fvar-tracking
           Run variable tracking pass.  It computes where variables are stored at each
           position in code.  Better debugging information is then generated (if the
           debugging information format supports this information).

           It is enabled by default when compiling with optimization (-Os, -O, -O2, ...),
           debugging information (-g) and the debug info format supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation and attempt to
           carry the annotations over throughout the compilation all the way to the end,
           in an attempt to improve debug information while optimizing.

           It can be enabled even if var-tracking is disabled, in which case annotations
           will be created and maintained, but discarded at the end.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle toggles -g.

       -print-file-name=library
           Print the full absolute name of the library file library that would be used
           when linking---and don't do anything else.  With this option, GCC does not
           compile or link anything; it just prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected by any other
           switches present in the command line.  This directory is supposed to exist in
           GCC_EXEC_PREFIX.

       -print-multi-lib
           Print the mapping from multilib directory names to compiler switches that
           enable them.  The directory name is separated from the switches by ;, and each
           switch starts with an @} instead of the @samp{-, without spaces between
           multiple switches.  This is supposed to ease shell-processing.

       -print-multi-os-directory
           Print the path to OS libraries for the selected multilib, relative to some lib
           subdirectory.  If OS libraries are present in the lib subdirectory and no
           multilibs are used, this is usually just ., if OS libraries are present in
           libsuffix sibling directories this prints e.g. ../lib64, ../lib or ../lib32, or
           if OS libraries are present in lib/subdir subdirectories it prints e.g. amd64,
           sparcv9 or ev6.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you do want to link
           with libgcc.a.  You can do

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a list of program
           and library directories gcc will search---and don't do anything else.

           This is useful when gcc prints the error message installation problem, cannot
           exec cpp0: No such file or directory.  To resolve this you either need to put
           cpp0 and the other compiler components where gcc expects to find them, or you
           can set the environment variable GCC_EXEC_PREFIX to the directory where you
           installed them.  Don't forget the trailing /.

       -print-sysroot
           Print the target sysroot directory that will be used during compilation.  This
           is the target sysroot specified either at configure time or using the --sysroot
           option, possibly with an extra suffix that depends on compilation options.  If
           no target sysroot is specified, the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for headers, or
           give an error if the compiler is not configured with such a suffix---and don't
           do anything else.

       -dumpmachine
           Print the compiler's target machine (for example, i686-pc-linux-gnu)---and
           don't do anything else.

       -dumpversion
           Print the compiler version (for example, 3.0)---and don't do anything else.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.  (This is
           used when GCC itself is being built.)

       -feliminate-unused-debug-types
           Normally, when producing DWARF2 output, GCC will emit debugging information for
           all types declared in a compilation unit, regardless of whether or not they are
           actually used in that compilation unit.  Sometimes this is useful, such as if,
           in the debugger, you want to cast a value to a type that is not actually used
           in your program (but is declared).  More often, however, this results in a
           significant amount of wasted space.  With this option, GCC will avoid producing
           debug symbol output for types that are nowhere used in the source file being
           compiled.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the cost of
       compilation and to make debugging produce the expected results.  Statements are
       independent: if you stop the program with a breakpoint between statements, you can
       then assign a new value to any variable or change the program counter to any other
       statement in the function and get exactly the results you would expect from the
       source code.

       Turning on optimization flags makes the compiler attempt to improve the performance
       and/or code size at the expense of compilation time and possibly the ability to
       debug the program.

       The compiler performs optimization based on the knowledge it has of the program.
       Compiling multiple files at once to a single output file mode allows the compiler
       to use information gained from all of the files when compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only optimizations that
       have a flag are listed.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot more
           memory for a large function.

           With -O, the compiler tries to reduce code size and execution time, without
           performing any optimizations that take a great deal of compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse
           -fguess-branch-probability -fif-conversion2 -fif-conversion
           -finline-small-functions -fipa-pure-const -fipa-reference -fmerge-constants
           -fsplit-wide-types -ftree-builtin-call-dce -ftree-ccp -ftree-ch
           -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-fre
           -ftree-sra -ftree-ter -funit-at-a-time

           -O also turns on -fomit-frame-pointer on machines where doing so does not
           interfere with debugging.

       -O2 Optimize even more.  GCC performs nearly all supported optimizations that do
           not involve a space-speed tradeoff.  As compared to -O, this option increases
           both compilation time and the performance of the generated code.

           -O2 turns on all optimization flags specified by -O.  It also turns on the
           following optimization flags: -fthread-jumps -falign-functions  -falign-jumps
           -falign-loops  -falign-labels -fcaller-saves -fcrossjumping -fcse-follow-jumps
           -fcse-skip-blocks -fdelete-null-pointer-checks -fexpensive-optimizations -fgcse
           -fgcse-lm -findirect-inlining -foptimize-sibling-calls -fpeephole2 -fregmove
           -freorder-blocks  -freorder-functions -frerun-cse-after-loop -fsched-interblock
           -fsched-spec -fschedule-insns  -fschedule-insns2 -fstrict-aliasing
           -fstrict-overflow -ftree-switch-conversion -ftree-pre -ftree-vrp

           Please note the warning under -fgcse about invoking -O2 on programs that use
           computed gotos.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also
           turns on the -finline-functions, -funswitch-loops, -fpredictive-commoning,
           -fgcse-after-reload, -ftree-vectorize and -fipa-cp-clone options.

       -O0 Reduce compilation time and make debugging produce the expected results.  This
           is the default.

       -Os Optimize for size.  -Os enables all -O2 optimizations that do not typically
           increase code size.  It also performs further optimizations designed to reduce
           code size.

           -Os disables the following optimization flags: -falign-functions  -falign-jumps
           -falign-loops -falign-labels  -freorder-blocks  -freorder-blocks-and-partition
           -fprefetch-loop-arrays  -ftree-vect-loop-version

           If you use multiple -O options, with or without level numbers, the last such
           option is the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags have both
       positive and negative forms; the negative form of -ffoo would be -fno-foo.  In the
       table below, only one of the forms is listed---the one you typically will use.  You
       can figure out the other form by either removing no- or adding it.

       The following options control specific optimizations.  They are either activated by
       -O options or are related to ones that are.  You can use the following flags in the
       rare cases when "fine-tuning" of optimizations to be performed is desired.

       -fno-default-inline
           Do not make member functions inline by default merely because they are defined
           inside the class scope (C++ only).  Otherwise, when you specify -O, member
           functions defined inside class scope are compiled inline by default; i.e., you
           don't need to add inline in front of the member function name.

       -fno-defer-pop
           Always pop the arguments to each function call as soon as that function
           returns.  For machines which must pop arguments after a function call, the
           compiler normally lets arguments accumulate on the stack for several function
           calls and pops them all at once.

           Disabled at levels -O, -O2, -O3, -Os.

       -fforward-propagate
           Perform a forward propagation pass on RTL.  The pass tries to combine two
           instructions and checks if the result can be simplified.  If loop unrolling is
           active, two passes are performed and the second is scheduled after loop
           unrolling.

           This option is enabled by default at optimization levels -O2, -O3, -Os.

       -fomit-frame-pointer
           Don't keep the frame pointer in a register for functions that don't need one.
           This avoids the instructions to save, set up and restore frame pointers; it
           also makes an extra register available in many functions.  It also makes
           debugging impossible on some machines.

           On some machines, such as the VAX, this flag has no effect, because the
           standard calling sequence automatically handles the frame pointer and nothing
           is saved by pretending it doesn't exist.  The machine-description macro
           "FRAME_POINTER_REQUIRED" controls whether a target machine supports this flag.

           Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -fno-inline
           Don't pay attention to the "inline" keyword.  Normally this option is used to
           keep the compiler from expanding any functions inline.  Note that if you are
           not optimizing, no functions can be expanded inline.

       -finline-small-functions
           Integrate functions into their callers when their body is smaller than expected
           function call code (so overall size of program gets smaller).  The compiler
           heuristically decides which functions are simple enough to be worth integrating
           in this way.

           Enabled at level -O2.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known at compile time
           thanks to previous inlining.  This option has any effect only when inlining
           itself is turned on by the -finline-functions or -finline-small-functions
           options.

           Enabled at level -O2.

       -finline-functions
           Integrate all simple functions into their callers.  The compiler heuristically
           decides which functions are simple enough to be worth integrating in this way.

           If all calls to a given function are integrated, and the function is declared
           "static", then the function is normally not output as assembler code in its own
           right.

           Enabled at level -O3.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into their caller even
           if they are not marked "inline".  If a call to a given function is integrated,
           then the function is not output as assembler code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose body seems
           smaller than the function call overhead early before doing -fprofile-generate
           instrumentation and real inlining pass.  Doing so makes profiling significantly
           cheaper and usually inlining faster on programs having large chains of nested
           wrapper functions.

           Enabled by default.

       -finline-limit=n
           By default, GCC limits the size of functions that can be inlined.  This flag
           allows coarse control of this limit.  n is the size of functions that can be
           inlined in number of pseudo instructions.

           Inlining is actually controlled by a number of parameters, which may be
           specified individually by using --param name=value.  The -finline-limit=n
           option sets some of these parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters controlling inlining
           and for the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in default behavior.

           Note: pseudo instruction represents, in this particular context, an abstract
           measurement of function's size.  In no way does it represent a count of
           assembly instructions and as such its exact meaning might change from one
           release to an another.

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the object file,
           even if the function has been inlined into all of its callers.  This switch
           does not affect functions using the "extern inline" extension in GNU C89.  In
           C++, emit any and all inline functions into the object file.

       -fkeep-static-consts
           Emit variables declared "static const" when optimization isn't turned on, even
           if the variables aren't referenced.

           GCC enables this option by default.  If you want to force the compiler to check
           if the variable was referenced, regardless of whether or not optimization is
           turned on, use the -fno-keep-static-consts option.

       -fmerge-constants
           Attempt to merge identical constants (string constants and floating point
           constants) across compilation units.

           This option is the default for optimized compilation if the assembler and
           linker support it.  Use -fno-merge-constants to inhibit this behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to -fmerge-constants this
           considers e.g. even constant initialized arrays or initialized constant
           variables with integral or floating point types.  Languages like C or C++
           require each variable, including multiple instances of the same variable in
           recursive calls, to have distinct locations, so using this option will result
           in non-conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first scheduling pass.
           This pass looks at innermost loops and reorders their instructions by
           overlapping different iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS based modulo scheduling with register moves
           allowed.  By setting this flag certain anti-dependences edges will be deleted
           which will trigger the generation of reg-moves based on the life-range
           analysis.  This option is effective only with -fmodulo-sched enabled.

       -fno-branch-count-reg
           Do not use "decrement and branch" instructions on a count register, but instead
           generate a sequence of instructions that decrement a register, compare it
           against zero, then branch based upon the result.  This option is only
           meaningful on architectures that support such instructions, which include x86,
           PowerPC, IA-64 and S/390.

           The default is -fbranch-count-reg.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction that calls a
           constant function contain the function's address explicitly.

           This option results in less efficient code, but some strange hacks that alter
           the assembler output may be confused by the optimizations performed when this
           option is not used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If the target supports a BSS section, GCC by default puts variables that are
           initialized to zero into BSS.  This can save space in the resulting code.

           This option turns off this behavior because some programs explicitly rely on
           variables going to the data section.  E.g., so that the resulting executable
           can find the beginning of that section and/or make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fmudflap -fmudflapth -fmudflapir
           For front-ends that support it (C and C++), instrument all risky pointer/array
           dereferencing operations, some standard library string/heap functions, and some
           other associated constructs with range/validity tests.  Modules so instrumented
           should be immune to buffer overflows, invalid heap use, and some other classes
           of C/C++ programming errors.  The instrumentation relies on a separate runtime
           library (libmudflap), which will be linked into a program if -fmudflap is given
           at link time.  Run-time behavior of the instrumented program is controlled by
           the MUDFLAP_OPTIONS environment variable.  See "env MUDFLAP_OPTIONS=-help
           a.out" for its options.

           Use -fmudflapth instead of -fmudflap to compile and to link if your program is
           multi-threaded.  Use -fmudflapir, in addition to -fmudflap or -fmudflapth, if
           instrumentation should ignore pointer reads.  This produces less
           instrumentation (and therefore faster execution) and still provides some
           protection against outright memory corrupting writes, but allows erroneously
           read data to propagate within a program.

       -fthread-jumps
           Perform optimizations where we check to see if a jump branches to a location
           where another comparison subsumed by the first is found.  If so, the first
           branch is redirected to either the destination of the second branch or a point
           immediately following it, depending on whether the condition is known to be
           true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such as "long long" on a
           32-bit system, split the registers apart and allocate them independently.  This
           normally generates better code for those types, but may make debugging more
           difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump instructions when
           the target of the jump is not reached by any other path.  For example, when CSE
           encounters an "if" statement with an "else" clause, CSE will follow the jump
           when the condition tested is false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow jumps which
           conditionally skip over blocks.  When CSE encounters a simple "if" statement
           with no else clause, -fcse-skip-blocks causes CSE to follow the jump around the
           body of the "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations has been
           performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This pass also
           performs global constant and copy propagation.

           Note: When compiling a program using computed gotos, a GCC extension, you may
           get better runtime performance if you disable the global common subexpression
           elimination pass by adding -fno-gcse to the command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression elimination will attempt
           to move loads which are only killed by stores into themselves.  This allows a
           loop containing a load/store sequence to be changed to a load outside the loop,
           and a copy/store within the loop.

           Enabled by default when gcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global common
           subexpression elimination.  This pass will attempt to move stores out of loops.
           When used in conjunction with -fgcse-lm, loops containing a load/store sequence
           can be changed to a load before the loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When -fgcse-las is enabled, the global common subexpression elimination pass
           eliminates redundant loads that come after stores to the same memory location
           (both partial and full redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination pass is
           performed after reload.  The purpose of this pass is to cleanup redundant
           spilling.

       -funsafe-loop-optimizations
           If given, the loop optimizer will assume that loop indices do not overflow, and
           that the loops with nontrivial exit condition are not infinite.  This enables a
           wider range of loop optimizations even if the loop optimizer itself cannot
           prove that these assumptions are valid.  Using -Wunsafe-loop-optimizations, the
           compiler will warn you if it finds this kind of loop.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation unifies equivalent
           code and save code size.  The resulting code may or may not perform better than
           without cross-jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine increments or decrements of addresses with memory accesses.  This pass
           is always skipped on architectures that do not have instructions to support
           this.  Enabled by default at -O and higher on architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default at -O and
           higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default at -O and
           higher.

       -fif-conversion
           Attempt to transform conditional jumps into branch-less equivalents.  This
           include use of conditional moves, min, max, set flags and abs instructions, and
           some tricks doable by standard arithmetics.  The use of conditional execution
           on chips where it is available is controlled by "if-conversion2".

           Enabled at levels -O, -O2, -O3, -Os.

       -fif-conversion2
           Use conditional execution (where available) to transform conditional jumps into
           branch-less equivalents.

           Enabled at levels -O, -O2, -O3, -Os.

       -fdelete-null-pointer-checks
           Use global dataflow analysis to identify and eliminate useless checks for null
           pointers.  The compiler assumes that dereferencing a null pointer would have
           halted the program.  If a pointer is checked after it has already been
           dereferenced, it cannot be null.

           In some environments, this assumption is not true, and programs can safely
           dereference null pointers.  Use -fno-delete-null-pointer-checks to disable this
           optimization for programs which depend on that behavior.

           Enabled at levels -O2, -O3, -Os.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively expensive.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-register-move
       -fregmove
           Attempt to reassign register numbers in move instructions and as operands of
           other simple instructions in order to maximize the amount of register tying.
           This is especially helpful on machines with two-operand instructions.

           Note -fregmove and -foptimize-register-move are the same optimization.

           Enabled at levels -O2, -O3, -Os.

       -fira-algorithm=algorithm
           Use specified coloring algorithm for the integrated register allocator.  The
           algorithm argument should be "priority" or "CB".  The first algorithm specifies
           Chow's priority coloring, the second one specifies Chaitin-Briggs coloring.
           The second algorithm can be unimplemented for some architectures.  If it is
           implemented, it is the default because Chaitin-Briggs coloring as a rule
           generates a better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The region
           argument should be one of "all", "mixed", or "one".  The first value means
           using all loops as register allocation regions, the second value which is the
           default means using all loops except for loops with small register pressure as
           the regions, and third one means using all function as a single region.  The
           first value can give best result for machines with small size and irregular
           register set, the third one results in faster and generates decent code and the
           smallest size code, and the default value usually give the best results in most
           cases and for most architectures.

       -fira-coalesce
           Do optimistic register coalescing.  This option might be profitable for
           architectures with big regular register files.

       -fno-ira-share-save-slots
           Switch off sharing stack slots used for saving call used hard registers living
           through a call.  Each hard register will get a separate stack slot and as a
           result function stack frame will be bigger.

       -fno-ira-share-spill-slots
           Switch off sharing stack slots allocated for pseudo-registers.  Each pseudo-
           register which did not get a hard register will get a separate stack slot and
           as a result function stack frame will be bigger.

       -fira-verbose=n
           Set up how verbose dump file for the integrated register allocator will be.
           Default value is 5.  If the value is greater or equal to 10, the dump file will
           be stderr as if the value were n minus 10.

       -fdelayed-branch
           If supported for the target machine, attempt to reorder instructions to exploit
           instruction slots available after delayed branch instructions.

           Enabled at levels -O, -O2, -O3, -Os.

       -fschedule-insns
           If supported for the target machine, attempt to reorder instructions to
           eliminate execution stalls due to required data being unavailable.  This helps
           machines that have slow floating point or memory load instructions by allowing
           other instructions to be issued until the result of the load or floating point
           instruction is required.

           Enabled at levels -O2, -O3, -Os.

       -fschedule-insns2
           Similar to -fschedule-insns, but requests an additional pass of instruction
           scheduling after register allocation has been done.  This is especially useful
           on machines with a relatively small number of registers and where memory load
           instructions take more than one cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Don't schedule instructions across basic blocks.  This is normally enabled by
           default when scheduling before register allocation, i.e.  with -fschedule-insns
           or at -O2 or higher.

       -fno-sched-spec
           Don't allow speculative motion of non-load instructions.  This is normally
           enabled by default when scheduling before register allocation, i.e.  with
           -fschedule-insns or at -O2 or higher.

       -fsched-spec-load
           Allow speculative motion of some load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or
           higher.

       -fsched-spec-load-dangerous
           Allow speculative motion of more load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or
           higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define how many insns (if any) can be moved prematurely from the queue of
           stalled insns into the ready list, during the second scheduling pass.
           -fno-sched-stalled-insns means that no insns will be moved prematurely,
           -fsched-stalled-insns=0 means there is no limit on how many queued insns can be
           moved prematurely.  -fsched-stalled-insns without a value is equivalent to
           -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) will be examined for a dependency on a
           stalled insn that is candidate for premature removal from the queue of stalled
           insns.  This has an effect only during the second scheduling pass, and only if
           -fsched-stalled-insns is used.  -fno-sched-stalled-insns-dep is equivalent to
           -fsched-stalled-insns-dep=0.  -fsched-stalled-insns-dep without a value is
           equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, do use superblock scheduling
           algorithm.  Superblock scheduling allows motion across basic block boundaries
           resulting on faster schedules.  This option is experimental, as not all machine
           descriptions used by GCC model the CPU closely enough to avoid unreliable
           results from the algorithm.

           This only makes sense when scheduling after register allocation, i.e. with
           -fschedule-insns2 or at -O2 or higher.

       -fsched2-use-traces
           Use -fsched2-use-superblocks algorithm when scheduling after register
           allocation and additionally perform code duplication in order to increase the
           size of superblocks using tracer pass.  See -ftracer for details on trace
           formation.

           This mode should produce faster but significantly longer programs.  Also
           without -fbranch-probabilities the traces constructed may not match the reality
           and hurt the performance.  This only makes sense when scheduling after register
           allocation, i.e. with -fschedule-insns2 or at -O2 or higher.

       -fsee
           Eliminate redundant sign extension instructions and move the non-redundant ones
           to optimal placement using lazy code motion (LCM).

       -freschedule-modulo-scheduled-loops
           The modulo scheduling comes before the traditional scheduling, if a loop was
           modulo scheduled we may want to prevent the later scheduling passes from
           changing its schedule, we use this option to control that.

       -fselective-scheduling
           Schedule instructions using selective scheduling algorithm.  Selective
           scheduling runs instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.  Selective
           scheduling runs instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable software pipelining of innermost loops during selective scheduling.
           This option has no effect until one of -fselective-scheduling or
           -fselective-scheduling2 is turned on.

       -fsel-sched-pipelining-outer-loops
           When pipelining loops during selective scheduling, also pipeline outer loops.
           This option has no effect until -fsel-sched-pipelining is turned on.

       -fcaller-saves
           Enable values to be allocated in registers that will be clobbered by function
           calls, by emitting extra instructions to save and restore the registers around
           such calls.  Such allocation is done only when it seems to result in better
           code than would otherwise be produced.

           This option is always enabled by default on certain machines, usually those
           which have no call-preserved registers to use instead.

           Enabled at levels -O2, -O3, -Os.

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler will attempt to use less stack
           space, even if that makes the program slower.  This option implies setting the
           large-stack-frame parameter to 100 and the large-stack-frame-growth parameter
           to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag is enabled by
           default at -O2 and -O3.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The difference between FRE
           and PRE is that FRE only considers expressions that are computed on all paths
           leading to the redundant computation.  This analysis is faster than PRE, though
           it exposes fewer redundancies.  This flag is enabled by default at -O and
           higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass eliminates unnecessary copy
           operations.  This flag is enabled by default at -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by default at -O and
           higher.

       -fipa-reference
           Discover which static variables do not escape cannot escape the compilation
           unit.  Enabled by default at -O and higher.

       -fipa-struct-reorg
           Perform structure reorganization optimization, that change C-like structures
           layout in order to better utilize spatial locality.  This transformation is
           effective for programs containing arrays of structures.  Available in two
           compilation modes: profile-based (enabled with -fprofile-generate) or static
           (which uses built-in heuristics).  Require -fipa-type-escape to provide the
           safety of this transformation.  It works only in whole program mode, so it
           requires -fwhole-program and -combine to be enabled.  Structures considered
           cold by this transformation are not affected (see --param
           struct-reorg-cold-struct-ratio=value).

           With this flag, the program debug info reflects a new structure layout.

       -fipa-pta
           Perform interprocedural pointer analysis.  This option is experimental and does
           not affect generated code.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization analyzes the
           program to determine when values passed to functions are constants and then
           optimizes accordingly.  This optimization can substantially increase
           performance if the application has constants passed to functions.  This flag is
           enabled by default at -O2, -Os and -O3.

       -fipa-cp-clone
           Perform function cloning to make interprocedural constant propagation stronger.
           When enabled, interprocedural constant propagation will perform function
           cloning when externally visible function can be called with constant arguments.
           Because this optimization can create multiple copies of functions, it may
           significantly increase code size (see --param ipcp-unit-growth=value).  This
           flag is enabled by default at -O3.

       -fipa-matrix-reorg
           Perform matrix flattening and transposing.  Matrix flattening tries to replace
           a m-dimensional matrix with its equivalent n-dimensional matrix, where n < m.
           This reduces the level of indirection needed for accessing the elements of the
           matrix. The second optimization is matrix transposing that attempts to change
           the order of the matrix's dimensions in order to improve cache locality.  Both
           optimizations need the -fwhole-program flag.  Transposing is enabled only if
           profiling information is available.

       -ftree-sink
           Perform forward store motion  on trees.  This flag is enabled by default at -O
           and higher.

       -ftree-ccp
           Perform sparse conditional constant propagation (CCP) on trees.  This pass only
           operates on local scalar variables and is enabled by default at -O and higher.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to initializations
           from a scalar array.  This flag is enabled by default at -O2 and higher.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is enabled by default
           at -O and higher.

       -ftree-builtin-call-dce
           Perform conditional dead code elimination (DCE) for calls to builtin functions
           that may set "errno" but are otherwise side-effect free.  This flag is enabled
           by default at -O2 and higher if -Os is not also specified.

       -ftree-dominator-opts
           Perform a variety of simple scalar cleanups (constant/copy propagation,
           redundancy elimination, range propagation and expression simplification) based
           on a dominator tree traversal.  This also performs jump threading (to reduce
           jumps to jumps). This flag is enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a store into a
           memory location which will later be overwritten by another store without any
           intervening loads.  In this case the earlier store can be deleted.  This flag
           is enabled by default at -O and higher.

       -ftree-ch
           Perform loop header copying on trees.  This is beneficial since it increases
           effectiveness of code motion optimizations.  It also saves one jump.  This flag
           is enabled by default at -O and higher.  It is not enabled for -Os, since it
           usually increases code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-loop-linear
           Perform linear loop transformations on tree.  This flag can improve cache
           performance and allow further loop optimizations to take place.

       -floop-interchange
           Perform loop interchange transformations on loops.  Interchanging two nested
           loops switches the inner and outer loops.  For example, given a loop like:

                   DO J = 1, M
                     DO I = 1, N
                       A(J, I) = A(J, I) * C
                     ENDDO
                   ENDDO

           loop interchange will transform the loop as if the user had written:

                   DO I = 1, N
                     DO J = 1, M
                       A(J, I) = A(J, I) * C
                     ENDDO
                   ENDDO

           which can be beneficial when "N" is larger than the caches, because in Fortran,
           the elements of an array are stored in memory contiguously by column, and the
           original loop iterates over rows, potentially creating at each access a cache
           miss.  This optimization applies to all the languages supported by GCC and is
           not limited to Fortran.  To use this code transformation, GCC has to be
           configured with --with-ppl and --with-cloog to enable the Graphite loop
           transformation infrastructure.

       -floop-strip-mine
           Perform loop strip mining transformations on loops.  Strip mining splits a loop
           into two nested loops.  The outer loop has strides equal to the strip size and
           the inner loop has strides of the original loop within a strip.  For example,
           given a loop like:

                   DO I = 1, N
                     A(I) = A(I) + C
                   ENDDO

           loop strip mining will transform the loop as if the user had written:

                   DO II = 1, N, 4
                     DO I = II, min (II + 3, N)
                       A(I) = A(I) + C
                     ENDDO
                   ENDDO

           This optimization applies to all the languages supported by GCC and is not
           limited to Fortran.  To use this code transformation, GCC has to be configured
           with --with-ppl and --with-cloog to enable the Graphite loop transformation
           infrastructure.

       -floop-block
           Perform loop blocking transformations on loops.  Blocking strip mines each loop
           in the loop nest such that the memory accesses of the element loops fit inside
           caches.  For example, given a loop like:

                   DO I = 1, N
                     DO J = 1, M
                       A(J, I) = B(I) + C(J)
                     ENDDO
                   ENDDO

           loop blocking will transform the loop as if the user had written:

                   DO II = 1, N, 64
                     DO JJ = 1, M, 64
                       DO I = II, min (II + 63, N)
                         DO J = JJ, min (JJ + 63, M)
                           A(J, I) = B(I) + C(J)
                         ENDDO
                       ENDDO
                     ENDDO
                   ENDDO

           which can be beneficial when "M" is larger than the caches, because the
           innermost loop will iterate over a smaller amount of data that can be kept in
           the caches.  This optimization applies to all the languages supported by GCC
           and is not limited to Fortran.  To use this code transformation, GCC has to be
           configured with --with-ppl and --with-cloog to enable the Graphite loop
           transformation infrastructure.

       -fcheck-data-deps
           Compare the results of several data dependence analyzers.  This option is used
           for debugging the data dependence analyzers.

       -ftree-loop-distribution
           Perform loop distribution.  This flag can improve cache performance on big loop
           bodies and allow further loop optimizations, like parallelization or
           vectorization, to take place.  For example, the loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only invariants that
           would be hard to handle at RTL level (function calls, operations that expand to
           nontrivial sequences of insns).  With -funswitch-loops it also moves operands
           of conditions that are invariant out of the loop, so that we can use just
           trivial invariantness analysis in loop unswitching.  The pass also includes
           store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in the loop for that
           determining number of iterations requires complicated analysis.  Later
           optimizations then may determine the number easily.  Useful especially in
           connection with unrolling.

       -fivopts
           Perform induction variable optimizations (strength reduction, induction
           variable merging and induction variable elimination) on trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n threads.  This
           is only possible for loops whose iterations are independent and can be
           arbitrarily reordered.  The optimization is only profitable on multiprocessor
           machines, for loops that are CPU-intensive, rather than constrained e.g. by
           memory bandwidth.  This option implies -pthread, and thus is only supported on
           targets that have support for -pthread.

       -ftree-sra
           Perform scalar replacement of aggregates.  This pass replaces structure
           references with scalars to prevent committing structures to memory too early.
           This flag is enabled by default at -O and higher.

       -ftree-copyrename
           Perform copy renaming on trees.  This pass attempts to rename compiler
           temporaries to other variables at copy locations, usually resulting in variable
           names which more closely resemble the original variables.  This flag is enabled
           by default at -O and higher.

       -ftree-coalesce-inlined-vars
           Permit the copyrename pass to subject inlined variables to coalescing into
           other variables.  This may harm debug information of such inlined variables,
           but it will keep variables of the main function apart from each other, such
           that they are more likely to contain the expected values in a debugging
           session.

       -ftree-coalesce-vars
           Permit the copyrename pass to subject all variables to SSA coalescing.  This
           may severely limit the ability to debug an optimized program compiled without
           -fvar-tracking-assignments.  In the negated form, this flag prevents SSA
           coalescing of user variables, including inlined ones.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal phase.  Single
           use/single def temporaries are replaced at their use location with their
           defining expression.  This results in non-GIMPLE code, but gives the expanders
           much more complex trees to work on resulting in better RTL generation.  This is
           enabled by default at -O and higher.

       -ftree-vectorize
           Perform loop vectorization on trees. This flag is enabled by default at -O3.

       -ftree-vect-loop-version
           Perform loop versioning when doing loop vectorization on trees.  When a loop
           appears to be vectorizable except that data alignment or data dependence cannot
           be determined at compile time then vectorized and non-vectorized versions of
           the loop are generated along with runtime checks for alignment or dependence to
           control which version is executed.  This option is enabled by default except at
           level -Os where it is disabled.

       -fvect-cost-model
           Enable cost model for vectorization.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to the constant
           propagation pass, but instead of values, ranges of values are propagated.  This
           allows the optimizers to remove unnecessary range checks like array bound
           checks and null pointer checks.  This is enabled by default at -O2 and higher.
           Null pointer check elimination is only done if -fdelete-null-pointer-checks is
           enabled.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation
           simplifies the control flow of the function allowing other optimizations to do
           better job.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile time or
           upon entry to the loop.  -funroll-loops implies -frerun-cse-after-loop.  This
           option makes code larger, and may or may not make it run faster.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain when the loop
           is entered.  This usually makes programs run more slowly.  -funroll-all-loops
           implies the same options as -funroll-loops,

       -fsplit-ivs-in-unroller
           Enables expressing of values of induction variables in later iterations of the
           unrolled loop using the value in the first iteration.  This breaks long
           dependency chains, thus improving efficiency of the scheduling passes.

           Combination of -fweb and CSE is often sufficient to obtain the same effect.
           However in cases the loop body is more complicated than a single basic block,
           this is not reliable.  It also does not work at all on some of the
           architectures due to restrictions in the CSE pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler will create multiple copies of some local
           variables when unrolling a loop which can result in superior code.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing computations
           (especially memory loads and stores) performed in previous iterations of loops.

           This option is enabled at level -O3.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to prefetch memory to
           improve the performance of loops that access large arrays.

           This option may generate better or worse code; results are highly dependent on
           the structure of loops within the source code.

           Disabled at level -Os.

       -fno-peephole
       -fno-peephole2
           Disable any machine-specific peephole optimizations.  The difference between
           -fno-peephole and -fno-peephole2 is in how they are implemented in the
           compiler; some targets use one, some use the other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2, -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC will use heuristics to guess branch probabilities if they are not provided
           by profiling feedback (-fprofile-arcs).  These heuristics are based on the
           control flow graph.  If some branch probabilities are specified by
           __builtin_expect, then the heuristics will be used to guess branch
           probabilities for the rest of the control flow graph, taking the
           __builtin_expect info into account.  The interactions between the heuristics
           and __builtin_expect can be complex, and in some cases, it may be useful to
           disable the heuristics so that the effects of __builtin_expect are easier to
           understand.

           The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce number of
           taken branches and improve code locality.

           Enabled at levels -O2, -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the compiled function, in order to
           reduce number of taken branches, partitions hot and cold basic blocks into
           separate sections of the assembly and .o files, to improve paging and cache
           locality performance.

           This optimization is automatically turned off in the presence of exception
           handling, for linkonce sections, for functions with a user-defined section
           attribute and on any architecture that does not support named sections.

       -freorder-functions
           Reorder functions in the object file in order to improve code locality.  This
           is implemented by using special subsections ".text.hot" for most frequently
           executed functions and ".text.unlikely" for unlikely executed functions.
           Reordering is done by the linker so object file format must support named
           sections and linker must place them in a reasonable way.

           Also profile feedback must be available in to make this option effective.  See
           -fprofile-arcs for details.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing rules applicable to the
           language being compiled.  For C (and C++), this activates optimizations based
           on the type of expressions.  In particular, an object of one type is assumed
           never to reside at the same address as an object of a different type, unless
           the types are almost the same.  For example, an "unsigned int" can alias an
           "int", but not a "void*" or a "double".  A character type may alias any other
           type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the one most
           recently written to (called "type-punning") is common.  Even with
           -fstrict-aliasing, type-punning is allowed, provided the memory is accessed
           through the union type.  So, the code above will work as expected.    However,
           this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly, access by taking the address, casting the resulting pointer and
           dereferencing the result has undefined behavior, even if the cast uses a union
           type, e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -fstrict-overflow
           Allow the compiler to assume strict signed overflow rules, depending on the
           language being compiled.  For C (and C++) this means that overflow when doing
           arithmetic with signed numbers is undefined, which means that the compiler may
           assume that it will not happen.  This permits various optimizations.  For
           example, the compiler will assume that an expression like "i + 10 > i" will
           always be true for signed "i".  This assumption is only valid if signed
           overflow is undefined, as the expression is false if "i + 10" overflows when
           using twos complement arithmetic.  When this option is in effect any attempt to
           determine whether an operation on signed numbers will overflow must be written
           carefully to not actually involve overflow.

           This option also allows the compiler to assume strict pointer semantics: given
           a pointer to an object, if adding an offset to that pointer does not produce a
           pointer to the same object, the addition is undefined.  This permits the
           compiler to conclude that "p + u > p" is always true for a pointer "p" and
           unsigned integer "u".  This assumption is only valid because pointer wraparound
           is undefined, as the expression is false if "p + u" overflows using twos
           complement arithmetic.

           See also the -fwrapv option.  Using -fwrapv means that integer signed overflow
           is fully defined: it wraps.  When -fwrapv is used, there is no difference
           between -fstrict-overflow and -fno-strict-overflow for integers.  With -fwrapv
           certain types of overflow are permitted.  For example, if the compiler gets an
           overflow when doing arithmetic on constants, the overflowed value can still be
           used with -fwrapv, but not otherwise.

           The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
           Align the start of functions to the next power-of-two greater than n, skipping
           up to n bytes.  For instance, -falign-functions=32 aligns functions to the next
           32-byte boundary, but -falign-functions=24 would align to the next 32-byte
           boundary only if this can be done by skipping 23 bytes or less.

           -fno-align-functions and -falign-functions=1 are equivalent and mean that
           functions will not be aligned.

           Some assemblers only support this flag when n is a power of two; in that case,
           it is rounded up.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
           Align all branch targets to a power-of-two boundary, skipping up to n bytes
           like -falign-functions.  This option can easily make code slower, because it
           must insert dummy operations for when the branch target is reached in the usual
           flow of the code.

           -fno-align-labels and -falign-labels=1 are equivalent and mean that labels will
           not be aligned.

           If -falign-loops or -falign-jumps are applicable and are greater than this
           value, then their values are used instead.

           If n is not specified or is zero, use a machine-dependent default which is very
           likely to be 1, meaning no alignment.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
           Align loops to a power-of-two boundary, skipping up to n bytes like
           -falign-functions.  The hope is that the loop will be executed many times,
           which will make up for any execution of the dummy operations.

           -fno-align-loops and -falign-loops=1 are equivalent and mean that loops will
           not be aligned.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
           Align branch targets to a power-of-two boundary, for branch targets where the
           targets can only be reached by jumping, skipping up to n bytes like
           -falign-functions.  In this case, no dummy operations need be executed.

           -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops will
           not be aligned.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -funit-at-a-time
           This option is left for compatibility reasons. -funit-at-a-time has no effect,
           while -fno-unit-at-a-time implies -fno-toplevel-reorder and
           -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm" statements.  Output
           them in the same order that they appear in the input file.  When this option is
           used, unreferenced static variables will not be removed.  This option is
           intended to support existing code which relies on a particular ordering.  For
           new code, it is better to use attributes.

           Enabled at level -O0.  When disabled explicitly, it also imply
           -fno-section-anchors that is otherwise enabled at -O0 on some targets.

       -fweb
           Constructs webs as commonly used for register allocation purposes and assign
           each web individual pseudo register.  This allows the register allocation pass
           to operate on pseudos directly, but also strengthens several other optimization
           passes, such as CSE, loop optimizer and trivial dead code remover.  It can,
           however, make debugging impossible, since variables will no longer stay in a
           "home register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume that the current compilation unit represents whole program being
           compiled.  All public functions and variables with the exception of "main" and
           those merged by attribute "externally_visible" become static functions and in a
           affect gets more aggressively optimized by interprocedural optimizers.  While
           this option is equivalent to proper use of "static" keyword for programs
           consisting of single file, in combination with option --combine this flag can
           be used to compile most of smaller scale C programs since the functions and
           variables become local for the whole combined compilation unit, not for the
           single source file itself.

           This option is not supported for Fortran programs.

       -fcprop-registers
           After register allocation and post-register allocation instruction splitting,
           we perform a copy-propagation pass to try to reduce scheduling dependencies and
           occasionally eliminate the copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an instrumented binary for multi-threaded programs may
           be inconsistent due to missed counter updates. When this option is specified,
           GCC will use heuristics to correct or smooth out such inconsistencies. By
           default, GCC will emit an error message when an inconsistent profile is
           detected.

       -fprofile-dir=path
           Set the directory to search the profile data files in to path.  This option
           affects only the profile data generated by -fprofile-generate, -ftest-coverage,
           -fprofile-arcs and used by -fprofile-use and -fbranch-probabilities and its
           related options.  By default, GCC will use the current directory as path thus
           the profile data file will appear in the same directory as the object file.

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to produce profile
           useful for later recompilation with profile feedback based optimization.  You
           must use -fprofile-generate both when compiling and when linking your program.

           The following options are enabled: "-fprofile-arcs", "-fprofile-values",
           "-fvpt".

           If path is specified, GCC will look at the path to find the profile feedback
           data files. See -fprofile-dir.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback directed optimizations, and optimizations generally
           profitable only with profile feedback available.

           The following options are enabled: "-fbranch-probabilities", "-fvpt",
           "-funroll-loops", "-fpeel-loops", "-ftracer"

           By default, GCC emits an error message if the feedback profiles do not match
           the source code.  This error can be turned into a warning by using
           -Wcoverage-mismatch.  Note this may result in poorly optimized code.

           If path is specified, GCC will look at the path to find the profile feedback
           data files. See -fprofile-dir.

       The following options control compiler behavior regarding floating point
       arithmetic.  These options trade off between speed and correctness.  All must be
       specifically enabled.

       -ffloat-store
           Do not store floating point variables in registers, and inhibit other options
           that might change whether a floating point value is taken from a register or
           memory.

           This option prevents undesirable excess precision on machines such as the 68000
           where the floating registers (of the 68881) keep more precision than a "double"
           is supposed to have.  Similarly for the x86 architecture.  For most programs,
           the excess precision does only good, but a few programs rely on the precise
           definition of IEEE floating point.  Use -ffloat-store for such programs, after
           modifying them to store all pertinent intermediate computations into variables.

       -ffast-math
           Sets -fno-math-errno, -funsafe-math-optimizations, -ffinite-math-only,
           -fno-rounding-math, -fno-signaling-nans and -fcx-limited-range.

           This option causes the preprocessor macro "__FAST_MATH__" to be defined.

           This option is not turned on by any -O option since it can result in incorrect
           output for programs which depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

       -fno-math-errno
           Do not set ERRNO after calling math functions that are executed with a single
           instruction, e.g., sqrt.  A program that relies on IEEE exceptions for math
           error handling may want to use this flag for speed while maintaining IEEE
           arithmetic compatibility.

           This option is not turned on by any -O option since it can result in incorrect
           output for programs which depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is therefore no
           reason for the compiler to consider the possibility that it might, and
           -fno-math-errno is the default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that (a) assume that
           arguments and results are valid and (b) may violate IEEE or ANSI standards.
           When used at link-time, it may include libraries or startup files that change
           the default FPU control word or other similar optimizations.

           This option is not turned on by any -O option since it can result in incorrect
           output for programs which depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.  Enables
           -fno-signed-zeros, -fno-trapping-math, -fassociative-math and
           -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow re-association of operands in series of floating-point operations.  This
           violates the ISO C and C++ language standard by possibly changing computation
           result.  NOTE: re-ordering may change the sign of zero as well as ignore NaNs
           and inhibit or create underflow or overflow (and thus cannot be used on a code
           which relies on rounding behavior like "(x + 2**52) - 2**52)".  May also
           reorder floating-point comparisons and thus may not be used when ordered
           comparisons are required.  This option requires that both -fno-signed-zeros and
           -fno-trapping-math be in effect.  Moreover, it doesn't make much sense with
           -frounding-math.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of dividing by the value if
           this enables optimizations.  For example "x / y" can be replaced with "x *
           (1/y)" which is useful if "(1/y)" is subject to common subexpression
           elimination.  Note that this loses precision and increases the number of flops
           operating on the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow optimizations for floating-point arithmetic that assume that arguments
           and results are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result in incorrect
           output for programs which depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating point arithmetic that ignore the signedness of
           zero.  IEEE arithmetic specifies the behavior of distinct +0.0 and -0.0 values,
           which then prohibits simplification of expressions such as x+0.0 or 0.0*x (even
           with -ffinite-math-only).  This option implies that the sign of a zero result
           isn't significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot generate user-
           visible traps.  These traps include division by zero, overflow, underflow,
           inexact result and invalid operation.  This option requires that
           -fno-signaling-nans be in effect.  Setting this option may allow faster code if
           one relies on "non-stop" IEEE arithmetic, for example.

           This option should never be turned on by any -O option since it can result in
           incorrect output for programs which depend on an exact implementation of IEEE
           or ISO rules/specifications for math functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable transformations and optimizations that assume default floating point
           rounding behavior.  This is round-to-zero for all floating point to integer
           conversions, and round-to-nearest for all other arithmetic truncations.  This
           option should be specified for programs that change the FP rounding mode
           dynamically, or that may be executed with a non-default rounding mode.  This
           option disables constant folding of floating point expressions at compile-time
           (which may be affected by rounding mode) and arithmetic transformations that
           are unsafe in the presence of sign-dependent rounding modes.

           The default is -fno-rounding-math.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that are affected by rounding mode.  Future versions of GCC may
           provide finer control of this setting using C99's "FENV_ACCESS" pragma.  This
           command line option will be used to specify the default state for
           "FENV_ACCESS".

       -frtl-abstract-sequences
           It is a size optimization method. This option is to find identical sequences of
           code, which can be turned into pseudo-procedures  and then  replace  all
           occurrences with  calls to  the  newly created subroutine. It is kind of an
           opposite of -finline-functions.  This optimization runs at RTL level.

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may generate user-visible traps
           during floating-point operations.  Setting this option disables optimizations
           that may change the number of exceptions visible with signaling NaNs.  This
           option implies -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
           Treat floating point constant as single precision constant instead of
           implicitly converting it to double precision constant.

       -fcx-limited-range
           When enabled, this option states that a range reduction step is not needed when
           performing complex division.  Also, there is no checking whether the result of
           a complex multiplication or division is "NaN + I*NaN", with an attempt to
           rescue the situation in that case.  The default is -fno-cx-limited-range, but
           is enabled by -ffast-math.

           This option controls the default setting of the ISO C99 "CX_LIMITED_RANGE"
           pragma.  Nevertheless, the option applies to all languages.

       -fcx-fortran-rules
           Complex multiplication and division follow Fortran rules.  Range reduction is
           done as part of complex division, but there is no checking whether the result
           of a complex multiplication or division is "NaN + I*NaN", with an attempt to
           rescue the situation in that case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve performance, but are
       not enabled by any -O options.  This section includes experimental options that may
       produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can compile it a
           second time using -fbranch-probabilities, to improve optimizations based on the
           number of times each branch was taken.  When the program compiled with
           -fprofile-arcs exits it saves arc execution counts to a file called
           sourcename.gcda for each source file.  The information in this data file is
           very dependent on the structure of the generated code, so you must use the same
           source code and the same optimization options for both compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and
           CALL_INSN.  These can be used to improve optimization.  Currently, they are
           only used in one place: in reorg.c, instead of guessing which path a branch is
           mostly to take, the REG_BR_PROB values are used to exactly determine which path
           is taken more often.

       -fprofile-values
           If combined with -fprofile-arcs, it adds code so that some data about values of
           expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered from profiling
           values of expressions and adds REG_VALUE_PROFILE notes to instructions for
           their later usage in optimizations.

           Enabled with -fprofile-generate and -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, it instructs the compiler to add a code to
           gather information about values of expressions.

           With -fbranch-probabilities, it reads back the data gathered and actually
           performs the optimizations based on them.  Currently the optimizations include
           specialization of division operation using the knowledge about the value of the
           denominator.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making use of
           registers left over after register allocation.  This optimization will most
           benefit processors with lots of registers.  Depending on the debug information
           format adopted by the target, however, it can make debugging impossible, since
           variables will no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation
           simplifies the control flow of the function allowing other optimizations to do
           better job.

           Enabled with -fprofile-use.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile time or
           upon entry to the loop.  -funroll-loops implies -frerun-cse-after-loop, -fweb
           and -frename-registers.  It also turns on complete loop peeling (i.e. complete
           removal of loops with small constant number of iterations).  This option makes
           code larger, and may or may not make it run faster.

           Enabled with -fprofile-use.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain when the loop
           is entered.  This usually makes programs run more slowly.  -funroll-all-loops
           implies the same options as -funroll-loops.

       -fpeel-loops
           Peels the loops for that there is enough information that they do not roll much
           (from profile feedback).  It also turns on complete loop peeling (i.e. complete
           removal of loops with small constant number of iterations).

           Enabled with -fprofile-use.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.  Enabled at
           level -O1

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop, with duplicates
           of the loop on both branches (modified according to result of the condition).

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section in the output file if the
           target supports arbitrary sections.  The name of the function or the name of
           the data item determines the section's name in the output file.

           Use these options on systems where the linker can perform optimizations to
           improve locality of reference in the instruction space.  Most systems using the
           ELF object format and SPARC processors running Solaris 2 have linkers with such
           optimizations.  AIX may have these optimizations in the future.

           Only use these options when there are significant benefits from doing so.  When
           you specify these options, the assembler and linker will create larger object
           and executable files and will also be slower.  You will not be able to use
           "gprof" on all systems if you specify this option and you may have problems
           with debugging if you specify both this option and -g.

       -fbranch-target-load-optimize
           Perform branch target register load optimization before prologue / epilogue
           threading.  The use of target registers can typically be exposed only during
           reload, thus hoisting loads out of loops and doing inter-block scheduling needs
           a separate optimization pass.

       -fbranch-target-load-optimize2
           Perform branch target register load optimization after prologue / epilogue
           threading.

       -fbtr-bb-exclusive
           When performing branch target register load optimization, don't reuse branch
           target registers in within any basic block.

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smashing attacks.
           This is done by adding a guard variable to functions with vulnerable objects.
           This includes functions that call alloca, and functions with buffers larger
           than 8 bytes.  The guards are initialized when a function is entered and then
           checked when the function exits.  If a guard check fails, an error message is
           printed and the program exits.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fsection-anchors
           Try to reduce the number of symbolic address calculations by using shared
           "anchor" symbols to address nearby objects.  This transformation can help to
           reduce the number of GOT entries and GOT accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           would usually calculate the addresses of all three variables, but if you
           compile it with -fsection-anchors, it will access the variables from a common
           anchor point instead.  The effect is similar to the following pseudocode (which
           isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       --param name=value
           In some places, GCC uses various constants to control the amount of
           optimization that is done.  For example, GCC will not inline functions that
           contain more that a certain number of instructions.  You can control some of
           these constants on the command-line using the --param option.

           The names of specific parameters, and the meaning of the values, are tied to
           the internals of the compiler, and are subject to change without notice in
           future releases.

           In each case, the value is an integer.  The allowable choices for name are
           given in the following table:

           sra-max-structure-size
               The maximum structure size, in bytes, at which the scalar replacement of
               aggregates (SRA) optimization will perform block copies.  The default
               value, 0, implies that GCC will select the most appropriate size itself.

           sra-field-structure-ratio
               The threshold ratio (as a percentage) between instantiated fields and the
               complete structure size.  We say that if the ratio of the number of bytes
               in instantiated fields to the number of bytes in the complete structure
               exceeds this parameter, then block copies are not used.  The default is 75.

           struct-reorg-cold-struct-ratio
               The threshold ratio (as a percentage) between a structure frequency and the
               frequency of the hottest structure in the program.  This parameter is used
               by struct-reorg optimization enabled by -fipa-struct-reorg.  We say that if
               the ratio of a structure frequency, calculated by profiling, to the hottest
               structure frequency in the program is less than this parameter, then
               structure reorganization is not applied to this structure.  The default is
               10.

           predictable-branch-cost-outcome
               When branch is predicted to be taken with probability lower than this
               threshold (in percent), then it is considered well predictable. The default
               is 10.

           max-crossjump-edges
               The maximum number of incoming edges to consider for crossjumping.  The
               algorithm used by -fcrossjumping is O(N^2) in the number of edges incoming
               to each block.  Increasing values mean more aggressive optimization, making
               the compile time increase with probably small improvement in executable
               size.

           min-crossjump-insns
               The minimum number of instructions which must be matched at the end of two
               blocks before crossjumping will be performed on them.  This value is
               ignored in the case where all instructions in the block being crossjumped
               from are matched.  The default value is 5.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic blocks instead of
               jumping.  The expansion is relative to a jump instruction.  The default
               value is 8.

           max-goto-duplication-insns
               The maximum number of instructions to duplicate to a block that jumps to a
               computed goto.  To avoid O(N^2) behavior in a number of passes, GCC factors
               computed gotos early in the compilation process, and unfactors them as late
               as possible.  Only computed jumps at the end of a basic blocks with no more
               than max-goto-duplication-insns are unfactored.  The default value is 8.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking for an
               instruction to fill a delay slot.  If more than this arbitrary number of
               instructions is searched, the time savings from filling the delay slot will
               be minimal so stop searching.  Increasing values mean more aggressive
               optimization, making the compile time increase with probably small
               improvement in executable run time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of instructions to
               consider when searching for a block with valid live register information.
               Increasing this arbitrarily chosen value means more aggressive
               optimization, increasing the compile time.  This parameter should be
               removed when the delay slot code is rewritten to maintain the control-flow
               graph.

           max-gcse-memory
               The approximate maximum amount of memory that will be allocated in order to
               perform the global common subexpression elimination optimization.  If more
               memory than specified is required, the optimization will not be done.

           max-gcse-passes
               The maximum number of passes of GCSE to run.  The default is 1.

           max-pending-list-length
               The maximum number of pending dependencies scheduling will allow before
               flushing the current state and starting over.  Large functions with few
               branches or calls can create excessively large lists which needlessly
               consume memory and resources.

           max-inline-insns-single
               Several parameters control the tree inliner used in gcc.  This number sets
               the maximum number of instructions (counted in GCC's internal
               representation) in a single function that the tree inliner will consider
               for inlining.  This only affects functions declared inline and methods
               implemented in a class declaration (C++).  The default value is 450.

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of functions that
               would otherwise not be considered for inlining by the compiler will be
               investigated.  To those functions, a different (more restrictive) limit
               compared to functions declared inline can be applied.  The default value is
               90.

           large-function-insns
               The limit specifying really large functions.  For functions larger than
               this limit after inlining, inlining is constrained by --param large-
               function-growth.  This parameter is useful primarily to avoid extreme
               compilation time caused by non-linear algorithms used by the backend.  The
               default value is 2700.

           large-function-growth
               Specifies maximal growth of large function caused by inlining in percents.
               The default value is 100 which limits large function growth to 2.0 times
               the original size.

           large-unit-insns
               The limit specifying large translation unit.  Growth caused by inlining of
               units larger than this limit is limited by --param inline-unit-growth.  For
               small units this might be too tight (consider unit consisting of function A
               that is inline and B that just calls A three time.  If B is small relative
               to A, the growth of unit is 300\% and yet such inlining is very sane.  For
               very large units consisting of small inlineable functions however the
               overall unit growth limit is needed to avoid exponential explosion of code
               size.  Thus for smaller units, the size is increased to --param large-unit-
               insns before applying --param inline-unit-growth.  The default is 10000

           inline-unit-growth
               Specifies maximal overall growth of the compilation unit caused by
               inlining.  The default value is 30 which limits unit growth to 1.3 times
               the original size.

           ipcp-unit-growth
               Specifies maximal overall growth of the compilation unit caused by
               interprocedural constant propagation.  The default value is 10 which limits
               unit growth to 1.1 times the original size.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the algorithm is
               trying to not grow past this limit too much.  Default value is 256 bytes.

           large-stack-frame-growth
               Specifies maximal growth of large stack frames caused by inlining in
               percents.  The default value is 1000 which limits large stack frame growth
               to 11 times the original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies maximum number of instructions out-of-line copy of self recursive
               inline function can grow into by performing recursive inlining.

               For functions declared inline --param max-inline-insns-recursive is taken
               into account.  For function not declared inline, recursive inlining happens
               only when -finline-functions (included in -O3) is enabled and --param max-
               inline-insns-recursive-auto is used.  The default value is 450.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies maximum recursion depth used by the recursive inlining.

               For functions declared inline --param max-inline-recursive-depth is taken
               into account.  For function not declared inline, recursive inlining happens
               only when -finline-functions (included in -O3) is enabled and --param max-
               inline-recursive-depth-auto is used.  The default value is 8.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having deep recursion in
               average and can hurt for function having little recursion depth by
               increasing the prologue size or complexity of function body to other
               optimizers.

               When profile feedback is available (see -fprofile-generate) the actual
               recursion depth can be guessed from probability that function will recurse
               via given call expression.  This parameter limits inlining only to call
               expression whose probability exceeds given threshold (in percents).  The
               default value is 10.

           inline-call-cost
               Specify cost of call instruction relative to simple arithmetics operations
               (having cost of 1).  Increasing this cost disqualifies inlining of non-leaf
               functions and at the same time increases size of leaf function that is
               believed to reduce function size by being inlined.  In effect it increases
               amount of inlining for code having large abstraction penalty (many
               functions that just pass the arguments to other functions) and decrease
               inlining for code with low abstraction penalty.  The default value is 12.

           min-vect-loop-bound
               The minimum number of iterations under which a loop will not get vectorized
               when -ftree-vectorize is used.  The number of iterations after
               vectorization needs to be greater than the value specified by this option
               to allow vectorization.  The default value is 0.

           max-unrolled-insns
               The maximum number of instructions that a loop should have if that loop is
               unrolled, and if the loop is unrolled, it determines how many times the
               loop code is unrolled.

           max-average-unrolled-insns
               The maximum number of instructions biased by probabilities of their
               execution that a loop should have if that loop is unrolled, and if the loop
               is unrolled, it determines how many times the loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The maximum number of instructions that a loop should have if that loop is
               peeled, and if the loop is peeled, it determines how many times the loop
               code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for complete
               peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop invariant motion.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables below that all
               candidates are considered for each use in induction variable optimizations.
               Only the most relevant candidates are considered if there are more
               candidates, to avoid quadratic time complexity.

           iv-max-considered-uses
               The induction variable optimizations give up on loops that contain more
               induction variable uses.

           iv-always-prune-cand-set-bound
               If number of candidates in the set is smaller than this value, we always
               try to remove unnecessary ivs from the set during its optimization when a
               new iv is added to the set.

           scev-max-expr-size
               Bound on size of expressions used in the scalar evolutions analyzer.  Large
               expressions slow the analyzer.

           omega-max-vars
               The maximum number of variables in an Omega constraint system.  The default
               value is 128.

           omega-max-geqs
               The maximum number of inequalities in an Omega constraint system.  The
               default value is 256.

           omega-max-eqs
               The maximum number of equalities in an Omega constraint system.  The
               default value is 128.

           omega-max-wild-cards
               The maximum number of wildcard variables that the Omega solver will be able
               to insert.  The default value is 18.

           omega-hash-table-size
               The size of the hash table in the Omega solver.  The default value is 550.

           omega-max-keys
               The maximal number of keys used by the Omega solver.  The default value is
               500.

           omega-eliminate-redundant-constraints
               When set to 1, use expensive methods to eliminate all redundant
               constraints.  The default value is 0.

           vect-max-version-for-alignment-checks
               The maximum number of runtime checks that can be performed when doing loop
               versioning for alignment in the vectorizer.  See option ftree-vect-loop-
               version for more information.

           vect-max-version-for-alias-checks
               The maximum number of runtime checks that can be performed when doing loop
               versioning for alias in the vectorizer.  See option ftree-vect-loop-version
               for more information.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute force algorithm for
               analysis of # of iterations of the loop tries to evaluate.

           hot-bb-count-fraction
               Select fraction of the maximal count of repetitions of basic block in
               program given basic block needs to have to be considered hot.

           hot-bb-frequency-fraction
               Select fraction of the maximal frequency of executions of basic block in
               function given basic block needs to have to be considered hot

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.  This is
               useful in cases where function contain single loop with known bound and
               other loop with unknown.  We predict the known number of iterations
               correctly, while the unknown number of iterations average to roughly 10.
               This means that the loop without bounds would appear artificially cold
               relative to the other one.

           align-threshold
               Select fraction of the maximal frequency of executions of basic block in
               function given basic block will get aligned.

           align-loop-iterations
               A loop expected to iterate at lest the selected number of iterations will
               get aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This value is used to limit superblock formation once the given percentage
               of executed instructions is covered.  This limits unnecessary code size
               expansion.

               The tracer-dynamic-coverage-feedback is used only when profile feedback is
               available.  The real profiles (as opposed to statically estimated ones) are
               much less balanced allowing the threshold to be larger value.

           tracer-max-code-growth
               Stop tail duplication once code growth has reached given percentage.  This
               is rather hokey argument, as most of the duplicates will be eliminated
               later in cross jumping, so it may be set to much higher values than is the
               desired code growth.

           tracer-min-branch-ratio
               Stop reverse growth when the reverse probability of best edge is less than
               this threshold (in percent).

           tracer-min-branch-ratio
           tracer-min-branch-ratio-feedback
               Stop forward growth if the best edge do have probability lower than this
               threshold.

               Similarly to tracer-dynamic-coverage two values are present, one for
               compilation for profile feedback and one for compilation without.  The
               value for compilation with profile feedback needs to be more conservative
               (higher) in order to make tracer effective.

           max-cse-path-length
               Maximum number of basic blocks on path that cse considers.  The default is
               10.

           max-cse-insns
               The maximum instructions CSE process before flushing. The default is 1000.

           max-aliased-vops
               Maximum number of virtual operands per function allowed to represent
               aliases before triggering the alias partitioning heuristic.  Alias
               partitioning reduces compile times and memory consumption needed for
               aliasing at the expense of precision loss in alias information.  The
               default value for this parameter is 100 for -O1, 500 for -O2 and 1000 for
               -O3.

               Notice that if a function contains more memory statements than the value of
               this parameter, it is not really possible to achieve this reduction.  In
               this case, the compiler will use the number of memory statements as the
               value for max-aliased-vops.

           avg-aliased-vops
               Average number of virtual operands per statement allowed to represent
               aliases before triggering the alias partitioning heuristic.  This works in
               conjunction with max-aliased-vops.  If a function contains more than max-
               aliased-vops virtual operators, then memory symbols will be grouped into
               memory partitions until either the total number of virtual operators is
               below max-aliased-vops or the average number of virtual operators per
               memory statement is below avg-aliased-vops.  The default value for this
               parameter is 1 for -O1 and -O2, and 3 for -O3.

           ggc-min-expand
               GCC uses a garbage collector to manage its own memory allocation.  This
               parameter specifies the minimum percentage by which the garbage collector's
               heap should be allowed to expand between collections.  Tuning this may
               improve compilation speed; it has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM
               >= 1GB.  If "getrlimit" is available, the notion of "RAM" is the smallest
               of actual RAM and "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to
               calculate RAM on a particular platform, the lower bound of 30% is used.
               Setting this parameter and ggc-min-heapsize to zero causes a full
               collection to occur at every opportunity.  This is extremely slow, but can
               be useful for debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins bothering to
               collect garbage.  The first collection occurs after the heap expands by
               ggc-min-expand% beyond ggc-min-heapsize.  Again, tuning this may improve
               compilation speed, and has no effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which tries to
               ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but with a lower
               bound of 4096 (four megabytes) and an upper bound of 131072 (128
               megabytes).  If GCC is not able to calculate RAM on a particular platform,
               the lower bound is used.  Setting this parameter very large effectively
               disables garbage collection.  Setting this parameter and ggc-min-expand to
               zero causes a full collection to occur at every opportunity.

           max-reload-search-insns
               The maximum number of instruction reload should look backward for
               equivalent register.  Increasing values mean more aggressive optimization,
               making the compile time increase with probably slightly better performance.
               The default value is 100.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take into account.
               Increasing values mean more aggressive optimization, making the compile
               time increase with probably slightly better performance.  The default value
               is 500.

           reorder-blocks-duplicate
           reorder-blocks-duplicate-feedback
               Used by basic block reordering pass to decide whether to use unconditional
               branch or duplicate the code on its destination.  Code is duplicated when
               its estimated size is smaller than this value multiplied by the estimated
               size of unconditional jump in the hot spots of the program.

               The reorder-block-duplicate-feedback is used only when profile feedback is
               available and may be set to higher values than reorder-block-duplicate
               since information about the hot spots is more accurate.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the scheduler should
               consider at any given time during the first scheduling pass.  Increasing
               values mean more thorough searches, making the compilation time increase
               with probably little benefit.  The default value is 100.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for interblock
               scheduling.  The default value is 10.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to be considered for pipelining in
               the selective scheduler.  The default value is 15.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for interblock
               scheduling.  The default value is 100.

           max-pipeline-region-insns
               The maximum number of insns in a region to be considered for pipelining in
               the selective scheduler.  The default value is 200.

           min-spec-prob
               The minimum probability (in percents) of reaching a source block for
               interblock speculative scheduling.  The default value is 40.

           max-sched-extend-regions-iters
               The maximum number of iterations through CFG to extend regions.  0 -
               disable region extension, N - do at most N iterations.  The default value
               is 0.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for speculative
               motion.  The default value is 3.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in percents), so that
               speculative insn will be scheduled.  The default value is 40.

           sched-mem-true-dep-cost
               Minimal distance (in CPU cycles) between store and load targeting same
               memory locations.  The default value is 1.

           selsched-max-lookahead
               The maximum size of the lookahead window of selective scheduling.  It is a
               depth of search for available instructions.  The default value is 50.

           selsched-max-sched-times
               The maximum number of times that an instruction will be scheduled during
               selective scheduling.  This is the limit on the number of iterations
               through which the instruction may be pipelined.  The default value is 2.

           selsched-max-insns-to-rename
               The maximum number of best instructions in the ready list that are
               considered for renaming in the selective scheduler.  The default value is
               2.

           max-last-value-rtl
               The maximum size measured as number of RTLs that can be recorded in an
               expression in combiner for a pseudo register as last known value of that
               register.  The default is 10000.

           integer-share-limit
               Small integer constants can use a shared data structure, reducing the
               compiler's memory usage and increasing its speed.  This sets the maximum
               value of a shared integer constant.  The default value is 256.

           min-virtual-mappings
               Specifies the minimum number of virtual mappings in the incremental SSA
               updater that should be registered to trigger the virtual mappings heuristic
               defined by virtual-mappings-ratio.  The default value is 100.

           virtual-mappings-ratio
               If the number of virtual mappings is virtual-mappings-ratio bigger than the
               number of virtual symbols to be updated, then the incremental SSA updater
               switches to a full update for those symbols.  The default ratio is 3.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that will receive stack smashing
               protection when -fstack-protection is used.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that needs to be duplicated
               when threading jumps.

           max-fields-for-field-sensitive
               Maximum number of fields in a structure we will treat in a field sensitive
               manner during pointer analysis.  The default is zero for -O0, and -O1 and
               100 for -Os, -O2, and -O3.

           prefetch-latency
               Estimate on average number of instructions that are executed before
               prefetch finishes.  The distance we prefetch ahead is proportional to this
               constant.  Increasing this number may also lead to less streams being
               prefetched (see simultaneous-prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 cache, in bytes.

           l1-cache-size
               The size of L1 cache, in kilobytes.

           l2-cache-size
               The size of L2 cache, in kilobytes.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.  By default,
               this should always be 1, which uses a more efficient internal mechanism for
               comparing types in C++ and Objective-C++.  However, if bugs in the
               canonical type system are causing compilation failures, set this value to 0
               to disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion will refuse to create arrays that are
               bigger than switch-conversion-max-branch-ratio times the number of branches
               in the switch.

           max-partial-antic-length
               Maximum length of the partial antic set computed during the tree partial
               redundancy elimination optimization (-ftree-pre) when optimizing at -O3 and
               above.  For some sorts of source code the enhanced partial redundancy
               elimination optimization can run away, consuming all of the memory
               available on the host machine.  This parameter sets a limit on the length
               of the sets that are computed, which prevents the runaway behavior.
               Setting a value of 0 for this parameter will allow an unlimited set length.

           sccvn-max-scc-size
               Maximum size of a strongly connected component (SCC) during SCCVN
               processing.  If this limit is hit, SCCVN processing for the whole function
               will not be done and optimizations depending on it will be disabled.  The
               default maximum SCC size is 10000.

           ira-max-loops-num
               IRA uses a regional register allocation by default.  If a function contains
               loops more than number given by the parameter, only at most given number of
               the most frequently executed loops will form regions for the regional
               register allocation.  The default value of the parameter is 100.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm of compression conflict table,
               the table can be still big for huge functions.  If the conflict table for a
               function could be more than size in MB given by the parameter, the conflict
               table is not built and faster, simpler, and lower quality register
               allocation algorithm will be used.  The algorithm do not use pseudo-
               register conflicts.  The default value of the parameter is 2000.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in compile time and in
               amount of needed compile time memory, with very large loops.  Loops with
               more basic blocks than this parameter won't have loop invariant motion
               optimization performed on them.  The default value of the parameter is 1000
               for -O1 and 10000 for -O2 and above.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during variable tracking
               dataflow analysis of any function.  If this limit is exceeded with variable
               tracking at assignments enabled, analysis for that function is retried
               without it, after removing all debug insns from the function.  If the limit
               is exceeded even without debug insns, var tracking analysis is completely
               disabled for the function.  Setting the parameter to zero makes it
               unlimited.

           min-nondebug-insn-uid
               Use uids starting at this parameter for nondebug insns.  The range below
               the parameter is reserved exclusively for debug insns created by
               -fvar-tracking-assignments, but debug insns may get (non-overlapping) uids
               above it if the reserved range is exhausted.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source file before
       actual compilation.

       If you use the -E option, nothing is done except preprocessing.  Some of these
       options make sense only together with -E because they cause the preprocessor output
       to be unsuitable for actual compilation.

       -Wp,option
           You can use -Wp,option to bypass the compiler driver and pass option directly
           through to the preprocessor.  If option contains commas, it is split into
           multiple options at the commas.  However, many options are modified, translated
           or interpreted by the compiler driver before being passed to the preprocessor,
           and -Wp forcibly bypasses this phase.  The preprocessor's direct interface is
           undocumented and subject to change, so whenever possible you should avoid using
           -Wp and let the driver handle the options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this to supply
           system-specific preprocessor options which GCC does not know how to recognize.

           If you want to pass an option that takes an argument, you must use
           -Xpreprocessor twice, once for the option and once for the argument.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they appeared
           during translation phase three in a #define directive.  In particular, the
           definition will be truncated by embedded newline characters.

           If you are invoking the preprocessor from a shell or shell-like program you may
           need to use the shell's quoting syntax to protect characters such as spaces
           that have a meaning in the shell syntax.

           If you wish to define a function-like macro on the command line, write its
           argument list with surrounding parentheses before the equals sign (if any).
           Parentheses are meaningful to most shells, so you will need to quote the
           option.  With sh and csh, -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on the command
           line.  All -imacros file and -include file options are processed after all -D
           and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided with a -D
           option.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The standard
           predefined macros remain defined.

       -I dir
           Add the directory dir to the list of directories to be searched for header
           files.  Directories named by -I are searched before the standard system include
           directories.  If the directory dir is a standard system include directory, the
           option is ignored to ensure that the default search order for system
           directories and the special treatment of system headers are not defeated .  If
           dir begins with "=", then the "=" will be replaced by the sysroot prefix; see
           --sysroot and -isysroot.

       -o file
           Write output to file.  This is the same as specifying file as the second non-
           option argument to cpp.  gcc has a different interpretation of a second non-
           option argument, so you must use -o to specify the output file.

       -Wall
           Turns on all optional warnings which are desirable for normal code.  At present
           this is -Wcomment, -Wtrigraphs, -Wmultichar and a warning about integer
           promotion causing a change of sign in "#if" expressions.  Note that many of the
           preprocessor's warnings are on by default and have no options to control them.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever
           a backslash-newline appears in a // comment.  (Both forms have the same
           effect.)

       -Wtrigraphs
           Most trigraphs in comments cannot affect the meaning of the program.  However,
           a trigraph that would form an escaped newline (??/ at the end of a line) can,
           by changing where the comment begins or ends.  Therefore, only trigraphs that
           would form escaped newlines produce warnings inside a comment.

           This option is implied by -Wall.  If -Wall is not given, this option is still
           enabled unless trigraphs are enabled.  To get trigraph conversion without
           warnings, but get the other -Wall warnings, use -trigraphs -Wall
           -Wno-trigraphs.

       -Wtraditional
           Warn about certain constructs that behave differently in traditional and ISO C.
           Also warn about ISO C constructs that have no traditional C equivalent, and
           problematic constructs which should be avoided.

       -Wundef
           Warn whenever an identifier which is not a macro is encountered in an #if
           directive, outside of defined.  Such identifiers are replaced with zero.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A macro is used if
           it is expanded or tested for existence at least once.  The preprocessor will
           also warn if the macro has not been used at the time it is redefined or
           undefined.

           Built-in macros, macros defined on the command line, and macros defined in
           include files are not warned about.

           Note: If a macro is actually used, but only used in skipped conditional blocks,
           then CPP will report it as unused.  To avoid the warning in such a case, you
           might improve the scope of the macro's definition by, for example, moving it
           into the first skipped block.  Alternatively, you could provide a dummy use
           with something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wendif-labels
           Warn whenever an #else or an #endif are followed by text.  This usually happens
           in code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments, but often are not in older
           programs.  This warning is on by default.

       -Werror
           Make all warnings into hard errors.  Source code which triggers warnings will
           be rejected.

       -Wsystem-headers
           Issue warnings for code in system headers.  These are normally unhelpful in
           finding bugs in your own code, therefore suppressed.  If you are responsible
           for the system library, you may want to see them.

       -w  Suppress all warnings, including those which GNU CPP issues by default.

       -pedantic
           Issue all the mandatory diagnostics listed in the C standard.  Some of them are
           left out by default, since they trigger frequently on harmless code.

       -pedantic-errors
           Issue all the mandatory diagnostics, and make all mandatory diagnostics into
           errors.  This includes mandatory diagnostics that GCC issues without -pedantic
           but treats as warnings.

       -M  Instead of outputting the result of preprocessing, output a rule suitable for
           make describing the dependencies of the main source file.  The preprocessor
           outputs one make rule containing the object file name for that source file, a
           colon, and the names of all the included files, including those coming from
           -include or -imacros command line options.

           Unless specified explicitly (with -MT or -MQ), the object file name consists of
           the name of the source file with any suffix replaced with object file suffix
           and with any leading directory parts removed.  If there are many included files
           then the rule is split into several lines using \-newline.  The rule has no
           commands.

           This option does not suppress the preprocessor's debug output, such as -dM.  To
           avoid mixing such debug output with the dependency rules you should explicitly
           specify the dependency output file with -MF, or use an environment variable
           like DEPENDENCIES_OUTPUT.  Debug output will still be sent to the regular
           output stream as normal.

           Passing -M to the driver implies -E, and suppresses warnings with an implicit
           -w.

       -MM Like -M but do not mention header files that are found in system header
           directories, nor header files that are included, directly or indirectly, from
           such a header.

           This implies that the choice of angle brackets or double quotes in an #include
           directive does not in itself determine whether that header will appear in -MM
           dependency output.  This is a slight change in semantics from GCC versions 3.0
           and earlier.

       -MF file
           When used with -M or -MM, specifies a file to write the dependencies to.  If no
           -MF switch is given the preprocessor sends the rules to the same place it would
           have sent preprocessed output.

           When used with the driver options -MD or -MMD, -MF overrides the default
           dependency output file.

       -MG In conjunction with an option such as -M requesting dependency generation, -MG
           assumes missing header files are generated files and adds them to the
           dependency list without raising an error.  The dependency filename is taken
           directly from the "#include" directive without prepending any path.  -MG also
           suppresses preprocessed output, as a missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency other than
           the main file, causing each to depend on nothing.  These dummy rules work
           around errors make gives if you remove header files without updating the
           Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By default CPP
           takes the name of the main input file, deletes any directory components and any
           file suffix such as .c, and appends the platform's usual object suffix.  The
           result is the target.

           An -MT option will set the target to be exactly the string you specify.  If you
           want multiple targets, you can specify them as a single argument to -MT, or use
           multiple -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The driver
           determines file based on whether an -o option is given.  If it is, the driver
           uses its argument but with a suffix of .d, otherwise it takes the name of the
           input file, removes any directory components and suffix, and applies a .d
           suffix.

           If -MD is used in conjunction with -E, any -o switch is understood to specify
           the dependency output file, but if used without -E, each -o is understood to
           specify a target object file.

           Since -E is not implied, -MD can be used to generate a dependency output file
           as a side-effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header files.

       -fpch-deps
           When using precompiled headers, this flag will cause the dependency-output
           flags to also list the files from the precompiled header's dependencies.  If
           not specified only the precompiled header would be listed and not the files
           that were used to create it because those files are not consulted when a
           precompiled header is used.

       -fpch-preprocess
           This option allows use of a precompiled header together with -E.  It inserts a
           special "#pragma", "#pragma GCC pch_preprocess "<filename>"" in the output to
           mark the place where the precompiled header was found, and its filename.  When
           -fpreprocessed is in use, GCC recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed output is
           only really suitable as input to GCC.  It is switched on by -save-temps.

           You should not write this "#pragma" in your own code, but it is safe to edit
           the filename if the PCH file is available in a different location.  The
           filename may be absolute or it may be relative to GCC's current directory.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
           Specify the source language: C, C++, Objective-C, or assembly.  This has
           nothing to do with standards conformance or extensions; it merely selects which
           base syntax to expect.  If you give none of these options, cpp will deduce the
           language from the extension of the source file: .c, .cc, .m, or .S.  Some other
           common extensions for C++ and assembly are also recognized.  If cpp does not
           recognize the extension, it will treat the file as C; this is the most generic
           mode.

           Note: Previous versions of cpp accepted a -lang option which selected both the
           language and the standards conformance level.  This option has been removed,
           because it conflicts with the -l option.

       -std=standard
       -ansi
           Specify the standard to which the code should conform.  Currently CPP knows
           about C and C++ standards; others may be added in the future.

           standard may be one of:

           "iso9899:1990"
           "c89"
               The ISO C standard from 1990.  c89 is the customary shorthand for this
               version of the standard.

               The -ansi option is equivalent to -std=c89.

           "iso9899:199409"
               The 1990 C standard, as amended in 1994.

           "iso9899:1999"
           "c99"
           "iso9899:199x"
           "c9x"
               The revised ISO C standard, published in December 1999.  Before
               publication, this was known as C9X.

           "gnu89"
               The 1990 C standard plus GNU extensions.  This is the default.

           "gnu99"
           "gnu9x"
               The 1999 C standard plus GNU extensions.

           "c++98"
               The 1998 ISO C++ standard plus amendments.

           "gnu++98"
               The same as -std=c++98 plus GNU extensions.  This is the default for C++
               code.

       -I- Split the include path.  Any directories specified with -I options before -I-
           are searched only for headers requested with "#include "file""; they are not
           searched for "#include <file>".  If additional directories are specified with
           -I options after the -I-, those directories are searched for all #include
           directives.

           In addition, -I- inhibits the use of the directory of the current file
           directory as the first search directory for "#include "file"".  This option has
           been deprecated.

       -nostdinc
           Do not search the standard system directories for header files.  Only the
           directories you have specified with -I options (and the directory of the
           current file, if appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard directories, but do
           still search the other standard directories.  (This option is used when
           building the C++ library.)

       -include file
           Process file as if "#include "file"" appeared as the first line of the primary
           source file.  However, the first directory searched for file is the
           preprocessor's working directory instead of the directory containing the main
           source file.  If not found there, it is searched for in the remainder of the
           "#include "..."" search chain as normal.

           If multiple -include options are given, the files are included in the order
           they appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced by scanning file is
           thrown away.  Macros it defines remain defined.  This allows you to acquire all
           the macros from a header without also processing its declarations.

           All files specified by -imacros are processed before all files specified by
           -include.

       -idirafter dir
           Search dir for header files, but do it after all directories specified with -I
           and the standard system directories have been exhausted.  dir is treated as a
           system include directory.  If dir begins with "=", then the "=" will be
           replaced by the sysroot prefix; see --sysroot and -isysroot.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.  If the
           prefix represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and add the
           resulting directory to the include search path.  -iwithprefixbefore puts it in
           the same place -I would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to header files.
           See the --sysroot option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific C++
           headers.

       -isystem dir
           Search dir for header files, after all directories specified by -I but before
           the standard system directories.  Mark it as a system directory, so that it
           gets the same special treatment as is applied to the standard system
           directories.  If dir begins with "=", then the "=" will be replaced by the
           sysroot prefix; see --sysroot and -isysroot.

       -iquote dir
           Search dir only for header files requested with "#include "file""; they are not
           searched for "#include <file>", before all directories specified by -I and
           before the standard system directories.  If dir begins with "=", then the "="
           will be replaced by the sysroot prefix; see --sysroot and -isysroot.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to the handling of directives such as
           "#define", "#ifdef", and "#error".  Other preprocessor operations, such as
           macro expansion and trigraph conversion are not performed.  In addition, the
           -dD option is implicitly enabled.

           With -fpreprocessed, predefinition of command line and most builtin macros is
           disabled.  Macros such as "__LINE__", which are contextually dependent, are
           handled normally.  This enables compilation of files previously preprocessed
           with "-E -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed take precedence.
           This enables full preprocessing of files previously preprocessed with "-E
           -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names in identifiers.  This option is experimental;
           in a future version of GCC, it will be enabled by default for C99 and C++.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been preprocessed.
           This suppresses things like macro expansion, trigraph conversion, escaped
           newline splicing, and processing of most directives.  The preprocessor still
           recognizes and removes comments, so that you can pass a file preprocessed with
           -C to the compiler without problems.  In this mode the integrated preprocessor
           is little more than a tokenizer for the front ends.

           -fpreprocessed is implicit if the input file has one of the extensions .i, .ii
           or .mi.  These are the extensions that GCC uses for preprocessed files created
           by -save-temps.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor report correct
           column numbers in warnings or errors, even if tabs appear on the line.  If the
           value is less than 1 or greater than 100, the option is ignored.  The default
           is 8.

       -fexec-charset=charset
           Set the execution character set, used for string and character constants.  The
           default is UTF-8.  charset can be any encoding supported by the system's
           "iconv" library routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and character
           constants.  The default is UTF-32 or UTF-16, whichever corresponds to the width
           of "wchar_t".  As with -fexec-charset, charset can be any encoding supported by
           the system's "iconv" library routine; however, you will have problems with
           encodings that do not fit exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character set of the
           input file to the source character set used by GCC.  If the locale does not
           specify, or GCC cannot get this information from the locale, the default is
           UTF-8.  This can be overridden by either the locale or this command line
           option.  Currently the command line option takes precedence if there's a
           conflict.  charset can be any encoding supported by the system's "iconv"
           library routine.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that will let the
           compiler know the current working directory at the time of preprocessing.  When
           this option is enabled, the preprocessor will emit, after the initial
           linemarker, a second linemarker with the current working directory followed by
           two slashes.  GCC will use this directory, when it's present in the
           preprocessed input, as the directory emitted as the current working directory
           in some debugging information formats.  This option is implicitly enabled if
           debugging information is enabled, but this can be inhibited with the negated
           form -fno-working-directory.  If the -P flag is present in the command line,
           this option has no effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be necessary if
           diagnostics are being scanned by a program that does not understand the column
           numbers, such as dejagnu.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.  This form is
           preferred to the older form -A predicate(answer), which is still supported,
           because it does not use shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -dCHARS
           CHARS is a sequence of one or more of the following characters, and must not be
           preceded by a space.  Other characters are interpreted by the compiler proper,
           or reserved for future versions of GCC, and so are silently ignored.  If you
           specify characters whose behavior conflicts, the result is undefined.

           M   Instead of the normal output, generate a list of #define directives for all
               the macros defined during the execution of the preprocessor, including
               predefined macros.  This gives you a way of finding out what is predefined
               in your version of the preprocessor.  Assuming you have no file foo.h, the
               command

                       touch foo.h; cpp -dM foo.h

               will show all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a synonym for
               -fdump-rtl-mach.

           D   Like M except in two respects: it does not include the predefined macros,
               and it outputs both the #define directives and the result of preprocessing.
               Both kinds of output go to the standard output file.

           N   Like D, but emit only the macro names, not their expansions.

           I   Output #include directives in addition to the result of preprocessing.

           U   Like D except that only macros that are expanded, or whose definedness is
               tested in preprocessor directives, are output; the output is delayed until
               the use or test of the macro; and #undef directives are also output for
               macros tested but undefined at the time.

       -P  Inhibit generation of linemarkers in the output from the preprocessor.  This
           might be useful when running the preprocessor on something that is not C code,
           and will be sent to a program which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the output file,
           except for comments in processed directives, which are deleted along with the
           directive.

           You should be prepared for side effects when using -C; it causes the
           preprocessor to treat comments as tokens in their own right.  For example,
           comments appearing at the start of what would be a directive line have the
           effect of turning that line into an ordinary source line, since the first token
           on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C,
           except that comments contained within macros are also passed through to the
           output file where the macro is expanded.

           In addition to the side-effects of the -C option, the -CC option causes all
           C++-style comments inside a macro to be converted to C-style comments.  This is
           to prevent later use of that macro from inadvertently commenting out the
           remainder of the source line.

           The -CC option is generally used to support lint comments.

       -traditional-cpp
           Try to imitate the behavior of old-fashioned C preprocessors, as opposed to ISO
           C preprocessors.

       -trigraphs
           Process trigraph sequences.  These are three-character sequences, all starting
           with ??, that are defined by ISO C to stand for single characters.  For
           example, ??/ stands for \, so '??/n' is a character constant for a newline.  By
           default, GCC ignores trigraphs, but in standard-conforming modes it converts
           them.  See the -std and -ansi options.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

       -remap
           Enable special code to work around file systems which only permit very short
           file names, such as MS-DOS.

       --help
       --target-help
           Print text describing all the command line options instead of preprocessing
           anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the beginning of
           execution, and report the final form of the include path.

       -H  Print the name of each header file used, in addition to other normal
           activities.  Each name is indented to show how deep in the #include stack it
           is.  Precompiled header files are also printed, even if they are found to be
           invalid; an invalid precompiled header file is printed with ...x and a valid
           one with ...! .

       -version
       --version
           Print out GNU CPP's version number.  With one dash, proceed to preprocess as
           normal.  With two dashes, exit immediately.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option contains commas, it is
           split into multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this to supply system-
           specific assembler options which GCC does not know how to recognize.

           If you want to pass an option that takes an argument, you must use -Xassembler
           twice, once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into an
       executable output file.  They are meaningless if the compiler is not doing a link
       step.

       object-file-name
           A file name that does not end in a special recognized suffix is considered to
           name an object file or library.  (Object files are distinguished from libraries
           by the linker according to the file contents.)  If linking is done, these
           object files are used as input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and object file
           names should not be used as arguments.

       -llibrary
       -l library
           Search the library named library when linking.  (The second alternative with
           the library as a separate argument is only for POSIX compliance and is not
           recommended.)

           It makes a difference where in the command you write this option; the linker
           searches and processes libraries and object files in the order they are
           specified.  Thus, foo.o -lz bar.o searches library z after file foo.o but
           before bar.o.  If bar.o refers to functions in z, those functions may not be
           loaded.

           The linker searches a standard list of directories for the library, which is
           actually a file named liblibrary.a.  The linker then uses this file as if it
           had been specified precisely by name.

           The directories searched include several standard system directories plus any
           that you specify with -L.

           Normally the files found this way are library files---archive files whose
           members are object files.  The linker handles an archive file by scanning
           through it for members which define symbols that have so far been referenced
           but not defined.  But if the file that is found is an ordinary object file, it
           is linked in the usual fashion.  The only difference between using an -l option
           and specifying a file name is that -l surrounds library with lib and .a and
           searches several directories.

       -lobjc
           You need this special case of the -l option in order to link an Objective-C or
           Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The standard system
           libraries are used normally, unless -nostdlib or -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the libraries you
           specify will be passed to the linker.  The standard startup files are used
           normally, unless -nostartfiles is used.  The compiler may generate calls to
           "memcmp", "memset", "memcpy" and "memmove".  These entries are usually resolved
           by entries in libc.  These entry points should be supplied through some other
           mechanism when this option is specified.

       -nostdlib
           Do not use the standard system startup files or libraries when linking.  No
           startup files and only the libraries you specify will be passed to the linker.
           The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove".
           These entries are usually resolved by entries in libc.  These entry points
           should be supplied through some other mechanism when this option is specified.

           One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is
           libgcc.a, a library of internal subroutines that GCC uses to overcome
           shortcomings of particular machines, or special needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid other standard
           libraries.  In other words, when you specify -nostdlib or -nodefaultlibs you
           should usually specify -lgcc as well.  This ensures that you have no unresolved
           references to internal GCC library subroutines.  (For example, __main, used to
           ensure C++ constructors will be called.)

       -pie
           Produce a position independent executable on targets which support it.  For
           predictable results, you must also specify the same set of options that were
           used to generate code (-fpie, -fPIE, or model suboptions) when you specify this
           option.

       -rdynamic
           Pass the flag -export-dynamic to the ELF linker, on targets that support it.
           This instructs the linker to add all symbols, not only used ones, to the
           dynamic symbol table. This option is needed for some uses of "dlopen" or to
           allow obtaining backtraces from within a program.

       -s  Remove all symbol table and relocation information from the executable.

       -static
           On systems that support dynamic linking, this prevents linking with the shared
           libraries.  On other systems, this option has no effect.

       -shared
           Produce a shared object which can then be linked with other objects to form an
           executable.  Not all systems support this option.  For predictable results, you
           must also specify the same set of options that were used to generate code
           (-fpic, -fPIC, or model suboptions) when you specify this option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options force the use
           of either the shared or static version respectively.  If no shared version of
           libgcc was built when the compiler was configured, these options have no
           effect.

           There are several situations in which an application should use the shared
           libgcc instead of the static version.  The most common of these is when the
           application wishes to throw and catch exceptions across different shared
           libraries.  In that case, each of the libraries as well as the application
           itself should use the shared libgcc.

           Therefore, the G++ and GCJ drivers automatically add -shared-libgcc whenever
           you build a shared library or a main executable, because C++ and Java programs
           typically use exceptions, so this is the right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you may find
           that they will not always be linked with the shared libgcc.  If GCC finds, at
           its configuration time, that you have a non-GNU linker or a GNU linker that
           does not support option --eh-frame-hdr, it will link the shared version of
           libgcc into shared libraries by default.  Otherwise, it will take advantage of
           the linker and optimize away the linking with the shared version of libgcc,
           linking with the static version of libgcc by default.  This allows exceptions
           to propagate through such shared libraries, without incurring relocation costs
           at library load time.

           However, if a library or main executable is supposed to throw or catch
           exceptions, you must link it using the G++ or GCJ driver, as appropriate for
           the languages used in the program, or using the option -shared-libgcc, such
           that it is linked with the shared libgcc.

       -symbolic
           Bind references to global symbols when building a shared object.  Warn about
           any unresolved references (unless overridden by the link editor option -Xlinker
           -z -Xlinker defs).  Only a few systems support this option.

       -T script
           Use script as the linker script.  This option is supported by most systems
           using the GNU linker.  On some targets, such as bare-board targets without an
           operating system, the -T option may be required when linking to avoid
           references to undefined symbols.

       -Xlinker option
           Pass option as an option to the linker.  You can use this to supply system-
           specific linker options which GCC does not know how to recognize.

           If you want to pass an option that takes a separate argument, you must use
           -Xlinker twice, once for the option and once for the argument.  For example, to
           pass -assert definitions, you must write -Xlinker -assert -Xlinker definitions.
           It does not work to write -Xlinker "-assert definitions", because this passes
           the entire string as a single argument, which is not what the linker expects.

           When using the GNU linker, it is usually more convenient to pass arguments to
           linker options using the option=value syntax than as separate arguments.  For
           example, you can specify -Xlinker -Map=output.map rather than -Xlinker -Map
           -Xlinker output.map.  Other linkers may not support this syntax for command-
           line options.

       -Wl,option
           Pass option as an option to the linker.  If option contains commas, it is split
           into multiple options at the commas.  You can use this syntax to pass an
           argument to the option.  For example, -Wl,-Map,output.map passes -Map
           output.map to the linker.  When using the GNU linker, you can also get the same
           effect with -Wl,-Map=output.map.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of library modules to
           define it.  You can use -u multiple times with different symbols to force
           loading of additional library modules.

   Options for Directory Search
       These options specify directories to search for header files, for libraries and for
       parts of the compiler:

       -Idir
           Add the directory dir to the head of the list of directories to be searched for
           header files.  This can be used to override a system header file, substituting
           your own version, since these directories are searched before the system header
           file directories.  However, you should not use this option to add directories
           that contain vendor-supplied system header files (use -isystem for that).  If
           you use more than one -I option, the directories are scanned in left-to-right
           order; the standard system directories come after.

           If a standard system include directory, or a directory specified with -isystem,
           is also specified with -I, the -I option will be ignored.  The directory will
           still be searched but as a system directory at its normal position in the
           system include chain.  This is to ensure that GCC's procedure to fix buggy
           system headers and the ordering for the include_next directive are not
           inadvertently changed.  If you really need to change the search order for
           system directories, use the -nostdinc and/or -isystem options.

       -iquotedir
           Add the directory dir to the head of the list of directories to be searched for
           header files only for the case of #include "file"; they are not searched for
           #include <file>, otherwise just like -I.

       -Ldir
           Add directory dir to the list of directories to be searched for -l.

       -Bprefix
           This option specifies where to find the executables, libraries, include files,
           and data files of the compiler itself.

           The compiler driver program runs one or more of the subprograms cpp, cc1, as
           and ld.  It tries prefix as a prefix for each program it tries to run, both
           with and without machine/version/.

           For each subprogram to be run, the compiler driver first tries the -B prefix,
           if any.  If that name is not found, or if -B was not specified, the driver
           tries two standard prefixes, which are /usr/lib/gcc/ and /usr/local/lib/gcc/.
           If neither of those results in a file name that is found, the unmodified
           program name is searched for using the directories specified in your PATH
           environment variable.

           The compiler will check to see if the path provided by the -B refers to a
           directory, and if necessary it will add a directory separator character at the
           end of the path.

           -B prefixes that effectively specify directory names also apply to libraries in
           the linker, because the compiler translates these options into -L options for
           the linker.  They also apply to includes files in the preprocessor, because the
           compiler translates these options into -isystem options for the preprocessor.
           In this case, the compiler appends include to the prefix.

           The run-time support file libgcc.a can also be searched for using the -B
           prefix, if needed.  If it is not found there, the two standard prefixes above
           are tried, and that is all.  The file is left out of the link if it is not
           found by those means.

           Another way to specify a prefix much like the -B prefix is to use the
           environment variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a
           number in the range 0 to 9, then it will be replaced by [dir/]include.  This is
           to help with boot-strapping the compiler.

       -specs=file
           Process file after the compiler reads in the standard specs file, in order to
           override the defaults that the gcc driver program uses when determining what
           switches to pass to cc1, cc1plus, as, ld, etc.  More than one -specs=file can
           be specified on the command line, and they are processed in order, from left to
           right.

       --sysroot=dir
           Use dir as the logical root directory for headers and libraries.  For example,
           if the compiler would normally search for headers in /usr/include and libraries
           in /usr/lib, it will instead search dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the --sysroot option
           will apply to libraries, but the -isysroot option will apply to header files.

           The GNU linker (beginning with version 2.16) has the necessary support for this
           option.  If your linker does not support this option, the header file aspect of
           --sysroot will still work, but the library aspect will not.

       -I- This option has been deprecated.  Please use -iquote instead for -I directories
           before the -I- and remove the -I-.  Any directories you specify with -I options
           before the -I- option are searched only for the case of #include "file"; they
           are not searched for #include <file>.

           If additional directories are specified with -I options after the -I-, these
           directories are searched for all #include directives.  (Ordinarily all -I
           directories are used this way.)

           In addition, the -I- option inhibits the use of the current directory (where
           the current input file came from) as the first search directory for #include
           "file".  There is no way to override this effect of -I-.  With -I. you can
           specify searching the directory which was current when the compiler was
           invoked.  That is not exactly the same as what the preprocessor does by
           default, but it is often satisfactory.

           -I- does not inhibit the use of the standard system directories for header
           files.  Thus, -I- and -nostdinc are independent.

   Specifying Target Machine and Compiler Version
       The usual way to run GCC is to run the executable called gcc, or <machine>-gcc when
       cross-compiling, or <machine>-gcc-<version> to run a version other than the one
       that was installed last.  Sometimes this is inconvenient, so GCC provides options
       that will switch to another cross-compiler or version.

       -b machine
           The argument machine specifies the target machine for compilation.

           The value to use for machine is the same as was specified as the machine type
           when configuring GCC as a cross-compiler.  For example, if a cross-compiler was
           configured with configure arm-elf, meaning to compile for an arm processor with
           elf binaries, then you would specify -b arm-elf to run that cross compiler.
           Because there are other options beginning with -b, the configuration must
           contain a hyphen, or -b alone should be one argument followed by the
           configuration in the next argument.

       -V version
           The argument version specifies which version of GCC to run.  This is useful
           when multiple versions are installed.  For example, version might be 4.0,
           meaning to run GCC version 4.0.

       The -V and -b options work by running the <machine>-gcc-<version> executable, so
       there's no real reason to use them if you can just run that directly.

   Hardware Models and Configurations
       Earlier we discussed the standard option -b which chooses among different installed
       compilers for completely different target machines, such as VAX vs. 68000 vs.
       80386.

       In addition, each of these target machine types can have its own special options,
       starting with -m, to choose among various hardware models or configurations---for
       example, 68010 vs 68020, floating coprocessor or none.  A single installed version
       of the compiler can compile for any model or configuration, according to the
       options specified.

       Some configurations of the compiler also support additional special options,
       usually for compatibility with other compilers on the same platform.

   ARC Options
       These options are defined for ARC implementations:

       -EL Compile code for little endian mode.  This is the default.

       -EB Compile code for big endian mode.

       -mmangle-cpu
           Prepend the name of the cpu to all public symbol names.  In multiple-processor
           systems, there are many ARC variants with different instruction and register
           set characteristics.  This flag prevents code compiled for one cpu to be linked
           with code compiled for another.  No facility exists for handling variants that
           are "almost identical".  This is an all or nothing option.

       -mcpu=cpu
           Compile code for ARC variant cpu.  Which variants are supported depend on the
           configuration.  All variants support -mcpu=base, this is the default.

       -mtext=text-section
       -mdata=data-section
       -mrodata=readonly-data-section
           Put functions, data, and readonly data in text-section, data-section, and
           readonly-data-section respectively by default.  This can be overridden with the
           "section" attribute.

       -mfix-cortex-m3-ldrd
           Some Cortex-M3 cores can cause data corruption when "ldrd" instructions with
           overlapping destination and base registers are used.  This option avoids
           generating these instructions.  This option is enabled by default when
           -mcpu=cortex-m3 is specified.

   ARM Options
       These -m options are defined for Advanced RISC Machines (ARM) architectures:

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: apcs-gnu, atpcs,
           aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure Call Standard
           for all functions, even if this is not strictly necessary for correct execution
           of the code.  Specifying -fomit-frame-pointer with this option will cause the
           stack frames not to be generated for leaf functions.  The default is
           -mno-apcs-frame.

       -mapcs
           This is a synonym for -mapcs-frame.

       -mthumb-interwork
           Generate code which supports calling between the ARM and Thumb instruction
           sets.  Without this option the two instruction sets cannot be reliably used
           inside one program.  The default is -mno-thumb-interwork, since slightly larger
           code is generated when -mthumb-interwork is specified.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prolog, or the merging
           of those instruction with the instructions in the function's body.  This means
           that all functions will start with a recognizable set of instructions (or in
           fact one of a choice from a small set of different function prologues), and
           this information can be used to locate the start if functions inside an
           executable piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are: soft,
           softfp and hard.

           Specifying soft causes GCC to generate output containing library calls for
           floating-point operations.  softfp allows the generation of code using hardware
           floating-point instructions, but still uses the soft-float calling conventions.
           hard allows generation of floating-point instructions and uses FPU-specific
           calling conventions.

           Using -mfloat-abi=hard with VFP coprocessors is not supported.  Use
           -mfloat-abi=softfp with the appropriate -mfpu option to allow the compiler to
           generate code that makes use of the hardware floating-point capabilities for
           these CPUs.

           The default depends on the specific target configuration.  Note that the hard-
           float and soft-float ABIs are not link-compatible; you must compile your entire
           program with the same ABI, and link with a compatible set of libraries.

       -mhard-float
           Equivalent to -mfloat-abi=hard.

       -msoft-float
           Equivalent to -mfloat-abi=soft.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This is the
           default for all standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the default is to
           compile code for a little-endian processor.

       -mwords-little-endian
           This option only applies when generating code for big-endian processors.
           Generate code for a little-endian word order but a big-endian byte order.  That
           is, a byte order of the form 32107654.  Note: this option should only be used
           if you require compatibility with code for big-endian ARM processors generated
           by versions of the compiler prior to 2.8.

       -mcpu=name
           This specifies the name of the target ARM processor.  GCC uses this name to
           determine what kind of instructions it can emit when generating assembly code.
           Permissible names are: arm2, arm250, arm3, arm6, arm60, arm600, arm610, arm620,
           arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710,
           arm710c, arm7100, arm720, arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm710t,
           arm720t, arm740t, strongarm, strongarm110, strongarm1100, strongarm1110, arm8,
           arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s, arm966e-s, arm968e-s,
           arm926ej-s, arm940t, arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s, arm10e,
           arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s,
           arm1176jz-s, arm1176jzf-s, cortex-a8, cortex-a9, cortex-r4, cortex-r4f,
           cortex-m3, cortex-m1, xscale, iwmmxt, iwmmxt2, ep9312.

       -mtune=name
           This option is very similar to the -mcpu= option, except that instead of
           specifying the actual target processor type, and hence restricting which
           instructions can be used, it specifies that GCC should tune the performance of
           the code as if the target were of the type specified in this option, but still
           choosing the instructions that it will generate based on the cpu specified by a
           -mcpu= option.  For some ARM implementations better performance can be obtained
           by using this option.

       -march=name
           This specifies the name of the target ARM architecture.  GCC uses this name to
           determine what kind of instructions it can emit when generating assembly code.
           This option can be used in conjunction with or instead of the -mcpu= option.
           Permissible names are: armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5,
           armv5t, armv5e, armv5te, armv6, armv6j, armv6t2, armv6z, armv6zk, armv6-m,
           armv7, armv7-a, armv7-r, armv7-m, iwmmxt, iwmmxt2, ep9312.

       -mfpu=name
       -mfpe=number
       -mfp=number
           This specifies what floating point hardware (or hardware emulation) is
           available on the target.  Permissible names are: fpa, fpe2, fpe3, maverick,
           vfp, vfpv3, vfpv3-d16 and neon.  -mfp and -mfpe are synonyms for
           -mfpu=fpenumber, for compatibility with older versions of GCC.

           If -msoft-float is specified this specifies the format of floating point
           values.

       -mstructure-size-boundary=n
           The size of all structures and unions will be rounded up to a multiple of the
           number of bits set by this option.  Permissible values are 8, 32 and 64.  The
           default value varies for different toolchains.  For the COFF targeted toolchain
           the default value is 8.  A value of 64 is only allowed if the underlying ABI
           supports it.

           Specifying the larger number can produce faster, more efficient code, but can
           also increase the size of the program.  Different values are potentially
           incompatible.  Code compiled with one value cannot necessarily expect to work
           with code or libraries compiled with another value, if they exchange
           information using structures or unions.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a "noreturn" function.
           It will be executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of
           the function into a register and then performing a subroutine call on this
           register.  This switch is needed if the target function will lie outside of the
           64 megabyte addressing range of the offset based version of subroutine call
           instruction.

           Even if this switch is enabled, not all function calls will be turned into long
           calls.  The heuristic is that static functions, functions which have the short-
           call attribute, functions that are inside the scope of a #pragma no_long_calls
           directive and functions whose definitions have already been compiled within the
           current compilation unit, will not be turned into long calls.  The exception to
           this rule is that weak function definitions, functions with the long-call
           attribute or the section attribute, and functions that are within the scope of
           a #pragma long_calls directive, will always be turned into long calls.

           This feature is not enabled by default.  Specifying -mno-long-calls will
           restore the default behavior, as will placing the function calls within the
           scope of a #pragma long_calls_off directive.  Note these switches have no
           effect on how the compiler generates code to handle function calls via function
           pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading it
           in the prologue for each function.  The run-time system is responsible for
           initializing this register with an appropriate value before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  The default is R10 unless
           stack-checking is enabled, when R9 is used.

       -mcirrus-fix-invalid-insns
           Insert NOPs into the instruction stream to in order to work around problems
           with invalid Maverick instruction combinations.  This option is only valid if
           the -mcpu=ep9312 option has been used to enable generation of instructions for
           the Cirrus Maverick floating point co-processor.  This option is not enabled by
           default, since the problem is only present in older Maverick implementations.
           The default can be re-enabled by use of the -mno-cirrus-fix-invalid-insns
           switch.

       -mpoke-function-name
           Write the name of each function into the text section, directly preceding the
           function prologue.  The generated code is similar to this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of "pc" stored at
           "fp + 0".  If the trace function then looks at location "pc - 12" and the top 8
           bits are set, then we know that there is a function name embedded immediately
           preceding this location and has length "((pc[-3]) & 0xff000000)".

       -mthumb
           Generate code for the Thumb instruction set.  The default is to use the 32-bit
           ARM instruction set.  This option automatically enables either 16-bit Thumb-1
           or mixed 16/32-bit Thumb-2 instructions based on the -mcpu=name and -march=name
           options.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard
           for all non-leaf functions.  (A leaf function is one that does not call any
           other functions.)  The default is -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard
           for all leaf functions.  (A leaf function is one that does not call any other
           functions.)  The default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled an ARM
           instruction set header which switches to Thumb mode before executing the rest
           of the function.  This allows these functions to be called from non-
           interworking code.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual functions) to execute
           correctly regardless of whether the target code has been compiled for
           interworking or not.  There is a small overhead in the cost of executing a
           function pointer if this option is enabled.

       -mtp=name
           Specify the access model for the thread local storage pointer.  The valid
           models are soft, which generates calls to "__aeabi_read_tp", cp15, which
           fetches the thread pointer from "cp15" directly (supported in the arm6k
           architecture), and auto, which uses the best available method for the selected
           processor.  The default setting is auto.

       -mword-relocations
           Only generate absolute relocations on word sized values (i.e. R_ARM_ABS32).
           This is enabled by default on targets (uClinux, SymbianOS) where the runtime
           loader imposes this restriction, and when -fpic or -fPIC is specified.

   AVR Options
       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify ATMEL AVR instruction set or MCU type.

           Instruction set avr1 is for the minimal AVR core, not supported by the C
           compiler, only for assembler programs (MCU types: at90s1200, attiny10,
           attiny11, attiny12, attiny15, attiny28).

           Instruction set avr2 (default) is for the classic AVR core with up to 8K
           program memory space (MCU types: at90s2313, at90s2323, attiny22, at90s2333,
           at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, at90c8534, at90s8535).

           Instruction set avr3 is for the classic AVR core with up to 128K program memory
           space (MCU types: atmega103, atmega603, at43usb320, at76c711).

           Instruction set avr4 is for the enhanced AVR core with up to 8K program memory
           space (MCU types: atmega8, atmega83, atmega85).

           Instruction set avr5 is for the enhanced AVR core with up to 128K program
           memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323,
           atmega64, atmega128, at43usb355, at94k).

       -msize
           Output instruction sizes to the asm file.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size will be
           smaller.

       -mcall-prologues
           Functions prologues/epilogues expanded as call to appropriate subroutines.
           Code size will be smaller.

       -mno-tablejump
           Do not generate tablejump insns which sometimes increase code size.  The option
           is now deprecated in favor of the equivalent -fno-jump-tables

       -mtiny-stack
           Change only the low 8 bits of the stack pointer.

       -mint8
           Assume int to be 8 bit integer.  This affects the sizes of all types: A char
           will be 1 byte, an int will be 1 byte, an long will be 2 bytes and long long
           will be 4 bytes.  Please note that this option does not comply to the C
           standards, but it will provide you with smaller code size.

   Blackfin Options
       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently, cpu can be one
           of bf512, bf514, bf516, bf518, bf522, bf523, bf524, bf525, bf526, bf527, bf531,
           bf532, bf533, bf534, bf536, bf537, bf538, bf539, bf542, bf544, bf547, bf548,
           bf549, bf561.  The optional sirevision specifies the silicon revision of the
           target Blackfin processor.  Any workarounds available for the targeted silicon
           revision will be enabled.  If sirevision is none, no workarounds are enabled.
           If sirevision is any, all workarounds for the targeted processor will be
           enabled.  The "__SILICON_REVISION__" macro is defined to two hexadecimal digits
           representing the major and minor numbers in the silicon revision.  If
           sirevision is none, the "__SILICON_REVISION__" is not defined.  If sirevision
           is any, the "__SILICON_REVISION__" is defined to be 0xffff.  If this optional
           sirevision is not used, GCC assumes the latest known silicon revision of the
           targeted Blackfin processor.

           Support for bf561 is incomplete.  For bf561, Only the processor macro is
           defined.  Without this option, bf532 is used as the processor by default.  The
           corresponding predefined processor macros for cpu is to be defined.  And for
           bfin-elf toolchain, this causes the hardware BSP provided by libgloss to be
           linked in if -msim is not given.

       -msim
           Specifies that the program will be run on the simulator.  This causes the
           simulator BSP provided by libgloss to be linked in.  This option has effect
           only for bfin-elf toolchain.  Certain other options, such as
           -mid-shared-library and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up and restore frame pointers and makes an extra
           register available in leaf functions.  The option -fomit-frame-pointer removes
           the frame pointer for all functions which might make debugging harder.

       -mspecld-anomaly
           When enabled, the compiler will ensure that the generated code does not contain
           speculative loads after jump instructions. If this option is used,
           "__WORKAROUND_SPECULATIVE_LOADS" is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from occurring.

       -mcsync-anomaly
           When enabled, the compiler will ensure that the generated code does not contain
           CSYNC or SSYNC instructions too soon after conditional branches.  If this
           option is used, "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions from occurring
           too soon after a conditional branch.

       -mlow-64k
           When enabled, the compiler is free to take advantage of the knowledge that the
           entire program fits into the low 64k of memory.

       -mno-low-64k
           Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
           Do stack checking using information placed into L1 scratchpad memory by the
           uClinux kernel.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This
           allows for execute in place and shared libraries in an environment without
           virtual memory management.  This option implies -fPIC.  With a bfin-elf target,
           this option implies -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID based shared libraries are being used.
           This is the default.

       -mleaf-id-shared-library
           Generate code that supports shared libraries via the library ID method, but
           assumes that this library or executable won't link against any other ID shared
           libraries.  That allows the compiler to use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any ID shared
           libraries.  Slower code will be generated for jump and call insns.

       -mshared-library-id=n
           Specified the identification number of the ID based shared library being
           compiled.  Specifying a value of 0 will generate more compact code, specifying
           other values will force the allocation of that number to the current library
           but is no more space or time efficient than omitting this option.

       -msep-data
           Generate code that allows the data segment to be located in a different area of
           memory from the text segment.  This allows for execute in place in an
           environment without virtual memory management by eliminating relocations
           against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.
           This is the default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of
           the function into a register and then performing a subroutine call on this
           register.  This switch is needed if the target function will lie outside of the
           24 bit addressing range of the offset based version of subroutine call
           instruction.

           This feature is not enabled by default.  Specifying -mno-long-calls will
           restore the default behavior.  Note these switches have no effect on how the
           compiler generates code to handle function calls via function pointers.

       -mfast-fp
           Link with the fast floating-point library. This library relaxes some of the
           IEEE floating-point standard's rules for checking inputs against Not-a-Number
           (NAN), in the interest of performance.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not
           known to bind locally.  It has no effect without -mfdpic.

       -mmulticore
           Build standalone application for multicore Blackfin processor. Proper start
           files and link scripts will be used to support multicore.  This option defines
           "__BFIN_MULTICORE". It can only be used with -mcpu=bf561[-sirevision]. It can
           be used with -mcorea or -mcoreb. If it's used without -mcorea or -mcoreb,
           single application/dual core programming model is used. In this model, the main
           function of Core B should be named as coreb_main. If it's used with -mcorea or
           -mcoreb, one application per core programming model is used.  If this option is
           not used, single core application programming model is used.

       -mcorea
           Build standalone application for Core A of BF561 when using one application per
           core programming model. Proper start files and link scripts will be used to
           support Core A. This option defines "__BFIN_COREA". It must be used with
           -mmulticore.

       -mcoreb
           Build standalone application for Core B of BF561 when using one application per
           core programming model. Proper start files and link scripts will be used to
           support Core B. This option defines "__BFIN_COREB". When this option is used,
           coreb_main should be used instead of main. It must be used with -mmulticore.

       -msdram
           Build standalone application for SDRAM. Proper start files and link scripts
           will be used to put the application into SDRAM.  Loader should initialize SDRAM
           before loading the application into SDRAM. This option defines "__BFIN_SDRAM".

       -micplb
           Assume that ICPLBs are enabled at runtime.  This has an effect on certain
           anomaly workarounds.  For Linux targets, the default is to assume ICPLBs are
           enabled; for standalone applications the default is off.

   CRIS Options
       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate code for the specified architecture.  The choices for architecture-
           type are v3, v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.
           Default is v0 except for cris-axis-linux-gnu, where the default is v10.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated code,
           except for the ABI and the set of available instructions.  The choices for
           architecture-type are the same as for -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The options -metrax4 and -metrax100 are synonyms for -march=v3 and -march=v8
           respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work around a bug in the "muls" and "mulu" instructions for CPU models where it
           applies.  This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the assembly code.
           This option also has the effect to turn off the #NO_APP formatted-code
           indicator to the assembler at the beginning of the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction; always emit
           compare and test instructions before use of condition codes.

       -mno-side-effects
           Do not emit instructions with side-effects in addressing modes other than post-
           increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These options (no-options) arranges (eliminate arrangements) for the stack-
           frame, individual data and constants to be aligned for the maximum single data
           access size for the chosen CPU model.  The default is to arrange for 32-bit
           alignment.  ABI details such as structure layout are not affected by these
           options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options above, these options
           arrange for stack-frame, writable data and constants to all be 32-bit, 16-bit
           or 8-bit aligned.  The default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and epilogue that
           sets up the stack-frame are omitted and no return instructions or return
           sequences are generated in the code.  Use this option only together with visual
           inspection of the compiled code: no warnings or errors are generated when call-
           saved registers must be saved, or storage for local variable needs to be
           allocated.

       -mno-gotplt
       -mgotplt
           With -fpic and -fPIC, don't generate (do generate) instruction sequences that
           load addresses for functions from the PLT part of the GOT rather than
           (traditional on other architectures) calls to the PLT.  The default is
           -mgotplt.

       -melf
           Legacy no-op option only recognized with the cris-axis-elf and cris-axis-linux-
           gnu targets.

       -mlinux
           Legacy no-op option only recognized with the cris-axis-linux-gnu target.

       -sim
           This option, recognized for the cris-axis-elf arranges to link with input-
           output functions from a simulator library.  Code, initialized data and zero-
           initialized data are allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at 0x40000000 and
           zero-initialized data at 0x80000000.

   CRX Options
       These options are defined specifically for the CRX ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mpush-args
           Push instructions will be used to pass outgoing arguments when functions are
           called. Enabled by default.

   Darwin Options
       These options are defined for all architectures running the Darwin operating
       system.

       FSF GCC on Darwin does not create "fat" object files; it will create an object file
       for the single architecture that it was built to target.  Apple's GCC on Darwin
       does create "fat" files if multiple -arch options are used; it does so by running
       the compiler or linker multiple times and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is determined by
       the flags that specify the ISA that GCC is targetting, like -mcpu or -march.  The
       -force_cpusubtype_ALL option can be used to override this.

       The Darwin tools vary in their behavior when presented with an ISA mismatch.  The
       assembler, as, will only permit instructions to be used that are valid for the
       subtype of the file it is generating, so you cannot put 64-bit instructions in an
       ppc750 object file.  The linker for shared libraries, /usr/bin/libtool, will fail
       and print an error if asked to create a shared library with a less restrictive
       subtype than its input files (for instance, trying to put a ppc970 object file in a
       ppc7400 library).  The linker for executables, ld, will quietly give the executable
       the most restrictive subtype of any of its input files.

       -Fdir
           Add the framework directory dir to the head of the list of directories to be
           searched for header files.  These directories are interleaved with those
           specified by -I options and are scanned in a left-to-right order.

           A framework directory is a directory with frameworks in it.  A framework is a
           directory with a "Headers" and/or "PrivateHeaders" directory contained directly
           in it that ends in ".framework".  The name of a framework is the name of this
           directory excluding the ".framework".  Headers associated with the framework
           are found in one of those two directories, with "Headers" being searched first.
           A subframework is a framework directory that is in a framework's "Frameworks"
           directory.  Includes of subframework headers can only appear in a header of a
           framework that contains the subframework, or in a sibling subframework header.
           Two subframeworks are siblings if they occur in the same framework.  A
           subframework should not have the same name as a framework, a warning will be
           issued if this is violated.  Currently a subframework cannot have
           subframeworks, in the future, the mechanism may be extended to support this.
           The standard frameworks can be found in "/System/Library/Frameworks" and
           "/Library/Frameworks".  An example include looks like "#include
           <Framework/header.h>", where Framework denotes the name of the framework and
           header.h is found in the "PrivateHeaders" or "Headers" directory.

       -iframeworkdir
           Like -F except the directory is a treated as a system directory.  The main
           difference between this -iframework and -F is that with -iframework the
           compiler does not warn about constructs contained within header files found via
           dir.  This option is valid only for the C family of languages.

       -gused
           Emit debugging information for symbols that are used.  For STABS debugging
           format, this enables -feliminate-unused-debug-symbols.  This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run on is version.
           Typical values of version include 10.1, 10.2, and 10.3.9.

           If the compiler was built to use the system's headers by default, then the
           default for this option is the system version on which the compiler is running,
           otherwise the default is to make choices which are compatible with as many
           systems and code bases as possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets -static, -fno-common,
           -fno-cxa-atexit, -fno-exceptions, -fno-non-call-exceptions, -fapple-kext,
           -fno-weak and -fno-rtti where applicable.  This mode also sets -mno-altivec,
           -msoft-float, -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for bool so that sizeof(bool)==1.  By default
           sizeof(bool) is 4 when compiling for Darwin/PowerPC and 1 when compiling for
           Darwin/x86, so this option has no effect on x86.

           Warning: The -mone-byte-bool switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Using this switch
           may require recompiling all other modules in a program, including system
           libraries.  Use this switch to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable for fast turn around development.  Needed to enable gdb
           to dynamically load ".o" files into already running programs.  -findirect-data
           and -ffix-and-continue are provided for backwards compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for more
           information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong architecture to be
           fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker will bind all
           undefined references when the file is loaded or launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more information.

       -bundle_loader executable
           This option specifies the executable that will be loading the build output file
           being linked.  See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC will produce a dynamic library instead of an
           executable when linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This causes GCC's output file to have the ALL subtype, instead of one
           controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker man page
           describes them in detail.

   DEC Alpha Options
       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for floating-point
           operations.  When -msoft-float is specified, functions in libgcc.a will be used
           to perform floating-point operations.  Unless they are replaced by routines
           that emulate the floating-point operations, or compiled in such a way as to
           call such emulations routines, these routines will issue floating-point
           operations.   If you are compiling for an Alpha without floating-point
           operations, you must ensure that the library is built so as not to call them.

           Note that Alpha implementations without floating-point operations are required
           to have floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate code that uses (does not use) the floating-point register set.
           -mno-fp-regs implies -msoft-float.  If the floating-point register set is not
           used, floating point operands are passed in integer registers as if they were
           integers and floating-point results are passed in $0 instead of $f0.  This is a
           non-standard calling sequence, so any function with a floating-point argument
           or return value called by code compiled with -mno-fp-regs must also be compiled
           with that option.

           A typical use of this option is building a kernel that does not use, and hence
           need not save and restore, any floating-point registers.

       -mieee
           The Alpha architecture implements floating-point hardware optimized for maximum
           performance.  It is mostly compliant with the IEEE floating point standard.
           However, for full compliance, software assistance is required.  This option
           generates code fully IEEE compliant code except that the inexact-flag is not
           maintained (see below).  If this option is turned on, the preprocessor macro
           "_IEEE_FP" is defined during compilation.  The resulting code is less efficient
           but is able to correctly support denormalized numbers and exceptional IEEE
           values such as not-a-number and plus/minus infinity.  Other Alpha compilers
           call this option -ieee_with_no_inexact.

       -mieee-with-inexact
           This is like -mieee except the generated code also maintains the IEEE inexact-
           flag.  Turning on this option causes the generated code to implement fully-
           compliant IEEE math.  In addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as
           a preprocessor macro.  On some Alpha implementations the resulting code may
           execute significantly slower than the code generated by default.  Since there
           is very little code that depends on the inexact-flag, you should normally not
           specify this option.  Other Alpha compilers call this option
           -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This option controls what floating-point related traps are enabled.  Other
           Alpha compilers call this option -fptm trap-mode.  The trap mode can be set to
           one of four values:

           n   This is the default (normal) setting.  The only traps that are enabled are
               the ones that cannot be disabled in software (e.g., division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are enabled as well.

           su  Like u, but the instructions are marked to be safe for software completion
               (see Alpha architecture manual for details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this option -fprm
           rounding-mode.  The rounding-mode can be one of:

           n   Normal IEEE rounding mode.  Floating point numbers are rounded towards the
               nearest machine number or towards the even machine number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating point numbers are rounded towards zero.

           d   Dynamic rounding mode.  A field in the floating point control register
               (fpcr, see Alpha architecture reference manual) controls the rounding mode
               in effect.  The C library initializes this register for rounding towards
               plus infinity.  Thus, unless your program modifies the fpcr, d corresponds
               to round towards plus infinity.

       -mtrap-precision=trap-precision
           In the Alpha architecture, floating point traps are imprecise.  This means
           without software assistance it is impossible to recover from a floating trap
           and program execution normally needs to be terminated.  GCC can generate code
           that can assist operating system trap handlers in determining the exact
           location that caused a floating point trap.  Depending on the requirements of
           an application, different levels of precisions can be selected:

           p   Program precision.  This option is the default and means a trap handler can
               only identify which program caused a floating point exception.

           f   Function precision.  The trap handler can determine the function that
               caused a floating point exception.

           i   Instruction precision.  The trap handler can determine the exact
               instruction that caused a floating point exception.

           Other Alpha compilers provide the equivalent options called -scope_safe and
           -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You must not use this
           option unless you also specify -mtrap-precision=i and either -mfp-trap-mode=su
           or -mfp-trap-mode=sui.  Its only effect is to emit the line .eflag 48 in the
           function prologue of the generated assembly file.  Under DEC Unix, this has the
           effect that IEEE-conformant math library routines will be linked in.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if it can
           construct it from smaller constants in two or three instructions.  If it
           cannot, it will output the constant as a literal and generate code to load it
           from the data segment at runtime.

           Use this option to require GCC to construct all integer constants using code,
           even if it takes more instructions (the maximum is six).

           You would typically use this option to build a shared library dynamic loader.
           Itself a shared library, it must relocate itself in memory before it can find
           the variables and constants in its own data segment.

       -malpha-as
       -mgas
           Select whether to generate code to be assembled by the vendor-supplied
           assembler (-malpha-as) or by the GNU assembler -mgas.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate whether GCC should generate code to use the optional BWX, CIX, FIX and
           MAX instruction sets.  The default is to use the instruction sets supported by
           the CPU type specified via -mcpu= option or that of the CPU on which GCC was
           built if none was specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating point arithmetic
           instead of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate symbol relocations except
           via assembler macros.  Use of these macros does not allow optimal instruction
           scheduling.  GNU binutils as of version 2.12 supports a new syntax that allows
           the compiler to explicitly mark which relocations should apply to which
           instructions.  This option is mostly useful for debugging, as GCC detects the
           capabilities of the assembler when it is built and sets the default
           accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via gp-relative
           relocations.  When -msmall-data is used, objects 8 bytes long or smaller are
           placed in a small data area (the ".sdata" and ".sbss" sections) and are
           accessed via 16-bit relocations off of the $gp register.  This limits the size
           of the small data area to 64KB, but allows the variables to be directly
           accessed via a single instruction.

           The default is -mlarge-data.  With this option the data area is limited to just
           below 2GB.  Programs that require more than 2GB of data must use "malloc" or
           "mmap" to allocate the data in the heap instead of in the program's data
           segment.

           When generating code for shared libraries, -fpic implies -msmall-data and -fPIC
           implies -mlarge-data.

       -msmall-text
       -mlarge-text
           When -msmall-text is used, the compiler assumes that the code of the entire
           program (or shared library) fits in 4MB, and is thus reachable with a branch
           instruction.  When -msmall-data is used, the compiler can assume that all local
           symbols share the same $gp value, and thus reduce the number of instructions
           required for a function call from 4 to 1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for machine type
           cpu_type.  You can specify either the EV style name or the corresponding chip
           number.  GCC supports scheduling parameters for the EV4, EV5 and EV6 family of
           processors and will choose the default values for the instruction set from the
           processor you specify.  If you do not specify a processor type, GCC will
           default to the processor on which the compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.

           Native Linux/GNU toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mcpu=native has no effect if
           GCC does not recognize the processor.

       -mtune=cpu_type
           Set only the instruction scheduling parameters for machine type cpu_type.  The
           instruction set is not changed.

           Native Linux/GNU toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mtune=native has no effect
           if GCC does not recognize the processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory references as
           seen by the application.  This number is highly dependent on the memory access
           patterns used by the application and the size of the external cache on the
           machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles for "typical"
               EV4 & EV5 hardware for the Level 1, 2 & 3 caches (also called Dcache,
               Scache, and Bcache), as well as to main memory.  Note that L3 is only valid
               for EV5.

   DEC Alpha/VMS Options
       These -m options are defined for the DEC Alpha/VMS implementations:

       -mvms-return-codes
           Return VMS condition codes from main.  The default is to return POSIX style
           condition (e.g. error) codes.

   FR30 Options
       These options are defined specifically for the FR30 port.

       -msmall-model
           Use the small address space model.  This can produce smaller code, but it does
           assume that all symbolic values and addresses will fit into a 20-bit range.

       -mno-lsim
           Assume that run-time support has been provided and so there is no need to
           include the simulator library (libsim.a) on the linker command line.

   FRV Options
       -mgpr-32
           Only use the first 32 general purpose registers.

       -mgpr-64
           Use all 64 general purpose registers.

       -mfpr-32
           Use only the first 32 floating point registers.

       -mfpr-64
           Use all 64 floating point registers

       -mhard-float
           Use hardware instructions for floating point operations.

       -msoft-float
           Use library routines for floating point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only use "icc0"
           and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating point double instructions.

       -mno-double
           Do not use floating point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, that uses function descriptors to represent pointers to
           functions.  Without any PIC/PIE-related options, it implies -fPIE.  With -fpic
           or -fpie, it assumes GOT entries and small data are within a 12-bit range from
           the GOT base address; with -fPIC or -fPIE, GOT offsets are computed with 32
           bits.  With a bfin-elf target, this option implies -msim.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not
           known to bind locally.  It has no effect without -mfdpic.  It's enabled by
           default if optimizing for speed and compiling for shared libraries (i.e., -fPIC
           or -fpic), or when an optimization option such as -O3 or above is present in
           the command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data that is known
           to be in read-only sections.  It's enabled by default, except for -fpic or
           -fpie: even though it may help make the global offset table smaller, it trades
           1 instruction for 4.  With -fPIC or -fPIE, it trades 3 instructions for 4, one
           of which may be shared by multiple symbols, and it avoids the need for a GOT
           entry for the referenced symbol, so it's more likely to be a win.  If it is
           not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by -mlibrary-pic,
           as well as by -fPIC and -fpic without -mfdpic.  You should never have to use it
           explicitly.

       -mlinked-fp
           Follow the EABI requirement of always creating a frame pointer whenever a stack
           frame is allocated.  This option is enabled by default and can be disabled with
           -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the current compilation unit.
           This allows the functions to be placed anywhere within the 32-bit address
           space.

       -malign-labels
           Try to align labels to an 8-byte boundary by inserting nops into the previous
           packet.  This option only has an effect when VLIW packing is enabled.  It
           doesn't create new packets; it merely adds nops to existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mscc
           Enable the use of conditional set instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely be removed in
           a future version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the compiler generated
           code.  It is enabled by default.

       -mno-optimize-membar
           This switch disables the automatic removal of redundant "membar" instructions
           from the generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible values are frv,
           fr550, tomcat, fr500, fr450, fr405, fr400, fr300 and simple.

   GNU/Linux Options
       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use the GNU C library instead of uClibc.  This is the default except on
           *-*-linux-*uclibc* targets.

       -muclibc
           Use uClibc instead of the GNU C library.  This is the default on
           *-*-linux-*uclibc* targets.

   H8/300 Options
       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten some address references at link time, when possible; uses the linker
           option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This switch must be
           used either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with -ms.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On the H8/300H and H8S, use the same alignment rules as for the H8/300.  The
           default for the H8/300H and H8S is to align longs and floats on 4 byte
           boundaries.  -malign-300 causes them to be aligned on 2 byte boundaries.  This
           option has no effect on the H8/300.

   HPPA Options
       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate code for the specified architecture.  The choices for architecture-
           type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA 2.0 processors.  Refer
           to /usr/lib/sched.models on an HP-UX system to determine the proper
           architecture option for your machine.  Code compiled for lower numbered
           architectures will run on higher numbered architectures, but not the other way
           around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mbig-switch
           Generate code suitable for big switch tables.  Use this option only if the
           assembler/linker complain about out of range branches within a switch table.

       -mjump-in-delay
           Fill delay slots of function calls with unconditional jump instructions by
           modifying the return pointer for the function call to be the target of the
           conditional jump.

       -mdisable-fpregs
           Prevent floating point registers from being used in any manner.  This is
           necessary for compiling kernels which perform lazy context switching of
           floating point registers.  If you use this option and attempt to perform
           floating point operations, the compiler will abort.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This avoids some
           rather obscure problems when compiling MIG generated code under MACH.

       -mno-space-regs
           Generate code that assumes the target has no space registers.  This allows GCC
           to generate faster indirect calls and use unscaled index address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.  This allows GCC
           to emit code which performs faster indirect calls.

           This option will not work in the presence of shared libraries or nested
           functions.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed
           register is one that the register allocator can not use.  This is useful when
           compiling kernel code.  A register range is specified as two registers
           separated by a dash.  Multiple register ranges can be specified separated by a
           comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes required by the
           HP-UX 10 linker.  This is equivalent to the +k option to the HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type cpu-type.  The
           choices for cpu-type are 700 7100, 7100LC, 7200, 7300 and 8000.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine the proper scheduling
           option for your machine.  The default scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note this makes symbolic
           debugging impossible.  It also triggers a bug in the HP-UX 8 and HP-UX 9
           linkers in which they give bogus error messages when linking some programs.

       -msoft-float
           Generate output containing library calls for floating point.  Warning: the
           requisite libraries are not available for all HPPA targets.  Normally the
           facilities of the machine's usual C compiler are used, but this cannot be done
           directly in cross-compilation.  You must make your own arrangements to provide
           suitable library functions for cross-compilation.

           -msoft-float changes the calling convention in the output file; therefore, it
           is only useful if you compile all of a program with this option.  In
           particular, you need to compile libgcc.a, the library that comes with GCC, with
           -msoft-float in order for this to work.

       -msio
           Generate the predefine, "_SIO", for server IO.  The default is -mwsio.  This
           generates the predefines, "__hp9000s700", "__hp9000s700__" and "_WSIO", for
           workstation IO.  These options are available under HP-UX and HI-UX.

       -mgnu-ld
           Use GNU ld specific options.  This passes -shared to ld when building a shared
           library.  It is the default when GCC is configured, explicitly or implicitly,
           with the GNU linker.  This option does not have any affect on which ld is
           called, it only changes what parameters are passed to that ld.  The ld that is
           called is determined by the --with-ld configure option, GCC's program search
           path, and finally by the user's PATH.  The linker used by GCC can be printed
           using which 'gcc -print-prog-name=ld'.  This option is only available on the 64
           bit HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mhp-ld
           Use HP ld specific options.  This passes -b to ld when building a shared
           library and passes +Accept TypeMismatch to ld on all links.  It is the default
           when GCC is configured, explicitly or implicitly, with the HP linker.  This
           option does not have any affect on which ld is called, it only changes what
           parameters are passed to that ld.  The ld that is called is determined by the
           --with-ld configure option, GCC's program search path, and finally by the
           user's PATH.  The linker used by GCC can be printed using which 'gcc
           -print-prog-name=ld'.  This option is only available on the 64 bit HP-UX GCC,
           i.e. configured with hppa*64*-*-hpux*.

       -mlong-calls
           Generate code that uses long call sequences.  This ensures that a call is
           always able to reach linker generated stubs.  The default is to generate long
           calls only when the distance from the call site to the beginning of the
           function or translation unit, as the case may be, exceeds a predefined limit
           set by the branch type being used.  The limits for normal calls are 7,600,000
           and 240,000 bytes, respectively for the PA 2.0 and PA 1.X architectures.
           Sibcalls are always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using the
           -ffunction-sections option, or when using the -mgas and -mno-portable-runtime
           options together under HP-UX with the SOM linker.

           It is normally not desirable to use this option as it will degrade performance.
           However, it may be useful in large applications, particularly when partial
           linking is used to build the application.

           The types of long calls used depends on the capabilities of the assembler and
           linker, and the type of code being generated.  The impact on systems that
           support long absolute calls, and long pic symbol-difference or pc-relative
           calls should be relatively small.  However, an indirect call is used on 32-bit
           ELF systems in pic code and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the specified UNIX
           standard.  The choices for unix-std are 93, 95 and 98.  93 is supported on all
           HP-UX versions.  95 is available on HP-UX 10.10 and later.  98 is available on
           HP-UX 11.11 and later.  The default values are 93 for HP-UX 10.00, 95 for HP-UX
           10.10 though to 11.00, and 98 for HP-UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.  -munix=95 provides
           additional predefines for "XOPEN_UNIX" and "_XOPEN_SOURCE_EXTENDED", and the
           startfile unix95.o.  -munix=98 provides additional predefines for
           "_XOPEN_UNIX", "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
           "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

           It is important to note that this option changes the interfaces for various
           library routines.  It also affects the operational behavior of the C library.
           Thus, extreme care is needed in using this option.

           Library code that is intended to operate with more than one UNIX standard must
           test, set and restore the variable __xpg4_extended_mask as appropriate.  Most
           GNU software doesn't provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when the -static
           option is specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on libdld.sl.
           There isn't an archive version of libdld.sl.  Thus, when the -static option is
           specified, special link options are needed to resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options to link with
           libdld.sl when the -static option is specified.  This causes the resulting
           binary to be dynamic.  On the 64-bit port, the linkers generate dynamic
           binaries by default in any case.  The -nolibdld option can be used to prevent
           the GCC driver from adding these link options.

       -threads
           Add support for multithreading with the dce thread library under HP-UX.  This
           option sets flags for both the preprocessor and linker.

   Intel 386 and AMD x86-64 Options
       These -m options are defined for the i386 and x86-64 family of computers:

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the
           ABI and the set of available instructions.  The choices for cpu-type are:

           generic
               Produce code optimized for the most common IA32/AMD64/EM64T processors.  If
               you know the CPU on which your code will run, then you should use the
               corresponding -mtune option instead of -mtune=generic.  But, if you do not
               know exactly what CPU users of your application will have, then you should
               use this option.

               As new processors are deployed in the marketplace, the behavior of this
               option will change.  Therefore, if you upgrade to a newer version of GCC,
               the code generated option will change to reflect the processors that were
               most common when that version of GCC was released.

               There is no -march=generic option because -march indicates the instruction
               set the compiler can use, and there is no generic instruction set
               applicable to all processors.  In contrast, -mtune indicates the processor
               (or, in this case, collection of processors) for which the code is
               optimized.

           native
               This selects the CPU to tune for at compilation time by determining the
               processor type of the compiling machine.  Using -mtune=native will produce
               code optimized for the local machine under the constraints of the selected
               instruction set.  Using -march=native will enable all instruction subsets
               supported by the local machine (hence the result might not run on different
               machines).

           i386
               Original Intel's i386 CPU.

           i486
               Intel's i486 CPU.  (No scheduling is implemented for this chip.)

           i586, pentium
               Intel Pentium CPU with no MMX support.

           pentium-mmx
               Intel PentiumMMX CPU based on Pentium core with MMX instruction set
               support.

           pentiumpro
               Intel PentiumPro CPU.

           i686
               Same as "generic", but when used as "march" option, PentiumPro instruction
               set will be used, so the code will run on all i686 family chips.

           pentium2
               Intel Pentium2 CPU based on PentiumPro core with MMX instruction set
               support.

           pentium3, pentium3m
               Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction
               set support.

           pentium-m
               Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction
               set support.  Used by Centrino notebooks.

           pentium4, pentium4m
               Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.

           prescott
               Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3
               instruction set support.

           nocona
               Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE,
               SSE2 and SSE3 instruction set support.

           core2
               Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3
               instruction set support.

           k6  AMD K6 CPU with MMX instruction set support.

           k6-2, k6-3
               Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set
               support.

           athlon, athlon-tbird
               AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch
               instructions support.

           athlon-4, athlon-xp, athlon-mp
               Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE
               instruction set support.

           k8, opteron, athlon64, athlon-fx
               AMD K8 core based CPUs with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction
               set extensions.)

           k8-sse3, opteron-sse3, athlon64-sse3
               Improved versions of k8, opteron and athlon64 with SSE3 instruction set
               support.

           amdfam10, barcelona
               AMD Family 10h core based CPUs with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSE4A, 3dNOW!, enhanced 3dNOW!, ABM and
               64-bit instruction set extensions.)

           winchip-c6
               IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX
               instruction set support.

           winchip2
               IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW!
               instruction set support.

           c3  Via C3 CPU with MMX and 3dNOW! instruction set support.  (No scheduling is
               implemented for this chip.)

           c3-2
               Via C3-2 CPU with MMX and SSE instruction set support.  (No scheduling is
               implemented for this chip.)

           geode
               Embedded AMD CPU with MMX and 3dNOW! instruction set support.

           While picking a specific cpu-type will schedule things appropriately for that
           particular chip, the compiler will not generate any code that does not run on
           the i386 without the -march=cpu-type option being used.

       -march=cpu-type
           Generate instructions for the machine type cpu-type.  The choices for cpu-type
           are the same as for -mtune.  Moreover, specifying -march=cpu-type implies
           -mtune=cpu-type.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating point arithmetics for selected unit unit.  The choices for
           unit are:

           387 Use the standard 387 floating point coprocessor present majority of chips
               and emulated otherwise.  Code compiled with this option will run almost
               everywhere.  The temporary results are computed in 80bit precision instead
               of precision specified by the type resulting in slightly different results
               compared to most of other chips.  See -ffloat-store for more detailed
               description.

               This is the default choice for i386 compiler.

           sse Use scalar floating point instructions present in the SSE instruction set.
               This instruction set is supported by Pentium3 and newer chips, in the AMD
               line by Athlon-4, Athlon-xp and Athlon-mp chips.  The earlier version of
               SSE instruction set supports only single precision arithmetics, thus the
               double and extended precision arithmetics is still done using 387.  Later
               version, present only in Pentium4 and the future AMD x86-64 chips supports
               double precision arithmetics too.

               For the i386 compiler, you need to use -march=cpu-type, -msse or -msse2
               switches to enable SSE extensions and make this option effective.  For the
               x86-64 compiler, these extensions are enabled by default.

               The resulting code should be considerably faster in the majority of cases
               and avoid the numerical instability problems of 387 code, but may break
               some existing code that expects temporaries to be 80bit.

               This is the default choice for the x86-64 compiler.

           sse,387
           sse+387
           both
               Attempt to utilize both instruction sets at once.  This effectively double
               the amount of available registers and on chips with separate execution
               units for 387 and SSE the execution resources too.  Use this option with
               care, as it is still experimental, because the GCC register allocator does
               not model separate functional units well resulting in instable performance.

       -masm=dialect
           Output asm instructions using selected dialect.  Supported choices are intel or
           att (the default one).  Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating point comparisons.
           These handle correctly the case where the result of a comparison is unordered.

       -msoft-float
           Generate output containing library calls for floating point.  Warning: the
           requisite libraries are not part of GCC.  Normally the facilities of the
           machine's usual C compiler are used, but this can't be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library
           functions for cross-compilation.

           On machines where a function returns floating point results in the 80387
           register stack, some floating point opcodes may be emitted even if -msoft-float
           is used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of functions.

           The usual calling convention has functions return values of types "float" and
           "double" in an FPU register, even if there is no FPU.  The idea is that the
           operating system should emulate an FPU.

           The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU
           registers instead.

       -mno-fancy-math-387
           Some 387 emulators do not support the "sin", "cos" and "sqrt" instructions for
           the 387.  Specify this option to avoid generating those instructions.  This
           option is the default on FreeBSD, OpenBSD and NetBSD.  This option is
           overridden when -march indicates that the target cpu will always have an FPU
           and so the instruction will not need emulation.  As of revision 2.6.1, these
           instructions are not generated unless you also use the
           -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
           Control whether GCC aligns "double", "long double", and "long long" variables
           on a two word boundary or a one word boundary.  Aligning "double" variables on
           a two word boundary will produce code that runs somewhat faster on a Pentium at
           the expense of more memory.

           On x86-64, -malign-double is enabled by default.

           Warning: if you use the -malign-double switch, structures containing the above
           types will be aligned differently than the published application binary
           interface specifications for the 386 and will not be binary compatible with
           structures in code compiled without that switch.

       -m96bit-long-double
       -m128bit-long-double
           These switches control the size of "long double" type.  The i386 application
           binary interface specifies the size to be 96 bits, so -m96bit-long-double is
           the default in 32 bit mode.

           Modern architectures (Pentium and newer) would prefer "long double" to be
           aligned to an 8 or 16 byte boundary.  In arrays or structures conforming to the
           ABI, this would not be possible.  So specifying a -m128bit-long-double will
           align "long double" to a 16 byte boundary by padding the "long double" with an
           additional 32 bit zero.

           In the x86-64 compiler, -m128bit-long-double is the default choice as its ABI
           specifies that "long double" is to be aligned on 16 byte boundary.

           Notice that neither of these options enable any extra precision over the x87
           standard of 80 bits for a "long double".

           Warning: if you override the default value for your target ABI, the structures
           and arrays containing "long double" variables will change their size as well as
           function calling convention for function taking "long double" will be modified.
           Hence they will not be binary compatible with arrays or structures in code
           compiled without that switch.

       -mlarge-data-threshold=number
           When -mcmodel=medium is specified, the data greater than threshold are placed
           in large data section.  This value must be the same across all object linked
           into the binary and defaults to 65535.

       -mrtd
           Use a different function-calling convention, in which functions that take a
           fixed number of arguments return with the "ret" num instruction, which pops
           their arguments while returning.  This saves one instruction in the caller
           since there is no need to pop the arguments there.

           You can specify that an individual function is called with this calling
           sequence with the function attribute stdcall.  You can also override the -mrtd
           option by using the function attribute cdecl.

           Warning: this calling convention is incompatible with the one normally used on
           Unix, so you cannot use it if you need to call libraries compiled with the Unix
           compiler.

           Also, you must provide function prototypes for all functions that take variable
           numbers of arguments (including "printf"); otherwise incorrect code will be
           generated for calls to those functions.

           In addition, seriously incorrect code will result if you call a function with
           too many arguments.  (Normally, extra arguments are harmlessly ignored.)

       -mregparm=num
           Control how many registers are used to pass integer arguments.  By default, no
           registers are used to pass arguments, and at most 3 registers can be used.  You
           can control this behavior for a specific function by using the function
           attribute regparm.

           Warning: if you use this switch, and num is nonzero, then you must build all
           modules with the same value, including any libraries.  This includes the system
           libraries and startup modules.

       -msseregparm
           Use SSE register passing conventions for float and double arguments and return
           values.  You can control this behavior for a specific function by using the
           function attribute sseregparm.

           Warning: if you use this switch then you must build all modules with the same
           value, including any libraries.  This includes the system libraries and startup
           modules.

       -mpc32
       -mpc64
       -mpc80
           Set 80387 floating-point precision to 32, 64 or 80 bits.  When -mpc32 is
           specified, the significands of results of floating-point operations are rounded
           to 24 bits (single precision); -mpc64 rounds the significands of results of
           floating-point operations to 53 bits (double precision) and -mpc80 rounds the
           significands of results of floating-point operations to 64 bits (extended
           double precision), which is the default.  When this option is used, floating-
           point operations in higher precisions are not available to the programmer
           without setting the FPU control word explicitly.

           Setting the rounding of floating-point operations to less than the default 80
           bits can speed some programs by 2% or more.  Note that some mathematical
           libraries assume that extended precision (80 bit) floating-point operations are
           enabled by default; routines in such libraries could suffer significant loss of
           accuracy, typically through so-called "catastrophic cancellation", when this
           option is used to set the precision to less than extended precision.

       -mstackrealign
           Realign the stack at entry.  On the Intel x86, the -mstackrealign option will
           generate an alternate prologue and epilogue that realigns the runtime stack if
           necessary.  This supports mixing legacy codes that keep a 4-byte aligned stack
           with modern codes that keep a 16-byte stack for SSE compatibility.  See also
           the attribute "force_align_arg_pointer", applicable to individual functions.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary.
           If -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or
           128 bits).

       -mincoming-stack-boundary=num
           Assume the incoming stack is aligned to a 2 raised to num byte boundary.  If
           -mincoming-stack-boundary is not specified, the one specified by
           -mpreferred-stack-boundary will be used.

           On Pentium and PentiumPro, "double" and "long double" values should be aligned
           to an 8 byte boundary (see -malign-double) or suffer significant run time
           performance penalties.  On Pentium III, the Streaming SIMD Extension (SSE) data
           type "__m128" may not work properly if it is not 16 byte aligned.

           To ensure proper alignment of this values on the stack, the stack boundary must
           be as aligned as that required by any value stored on the stack.  Further,
           every function must be generated such that it keeps the stack aligned.  Thus
           calling a function compiled with a higher preferred stack boundary from a
           function compiled with a lower preferred stack boundary will most likely
           misalign the stack.  It is recommended that libraries that use callbacks always
           use the default setting.

           This extra alignment does consume extra stack space, and generally increases
           code size.  Code that is sensitive to stack space usage, such as embedded
           systems and operating system kernels, may want to reduce the preferred
           alignment to -mpreferred-stack-boundary=2.

       -mmmx
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -msse3
       -mno-sse3
       -mssse3
       -mno-ssse3
       -msse4.1
       -mno-sse4.1
       -msse4.2
       -mno-sse4.2
       -msse4
       -mno-sse4
       -mavx
       -mno-avx
       -maes
       -mno-aes
       -mpclmul
       -mno-pclmul
       -mfsgsbase
       -mno-fsgsbase
       -mrdrnd
       -mno-rdrnd
       -mf16c
       -mno-f16c
       -msse4a
       -mno-sse4a
       -mfma4
       -mno-fma4
       -mxop
       -mno-xop
       -mlwp
       -mno-lwp
       -m3dnow
       -mno-3dnow
       -mpopcnt
       -mno-popcnt
       -mabm
       -mno-abm
       -mbmi
       -mno-bmi
       -mtbm
       -mno-tbm
           These switches enable or disable the use of instructions in the MMX, SSE, SSE2,
           SSE3, SSSE3, SSE4.1, AVX, AES, PCLMUL, FSGSBASE, RDRND, F16C, SSE4A, FMA4, XOP,
           LWP, ABM, BMI, or 3DNow! extended instruction sets.  These extensions are also
           available as built-in functions: see X86 Built-in Functions, for details of the
           functions enabled and disabled by these switches.

           To have SSE/SSE2 instructions generated automatically from floating-point code
           (as opposed to 387 instructions), see -mfpmath=sse.

           GCC depresses SSEx instructions when -mavx is used. Instead, it generates new
           AVX instructions or AVX equivalence for all SSEx instructions when needed.

           These options will enable GCC to use these extended instructions in generated
           code, even without -mfpmath=sse.  Applications which perform runtime CPU
           detection must compile separate files for each supported architecture, using
           the appropriate flags.  In particular, the file containing the CPU detection
           code should be compiled without these options.

       -mfused-madd
       -mno-fused-madd
           Do (don't) generate code that uses the fused multiply/add or multiply/subtract
           instructions.  The default is to use these instructions.

       -mcld
           This option instructs GCC to emit a "cld" instruction in the prologue of
           functions that use string instructions.  String instructions depend on the DF
           flag to select between autoincrement or autodecrement mode.  While the ABI
           specifies the DF flag to be cleared on function entry, some operating systems
           violate this specification by not clearing the DF flag in their exception
           dispatchers.  The exception handler can be invoked with the DF flag set which
           leads to wrong direction mode, when string instructions are used.  This option
           can be enabled by default on 32-bit x86 targets by configuring GCC with the
           --enable-cld configure option.  Generation of "cld" instructions can be
           suppressed with the -mno-cld compiler option in this case.

       -mcx16
           This option will enable GCC to use CMPXCHG16B instruction in generated code.
           CMPXCHG16B allows for atomic operations on 128-bit double quadword (or oword)
           data types.  This is useful for high resolution counters that could be updated
           by multiple processors (or cores).  This instruction is generated as part of
           atomic built-in functions: see Atomic Builtins for details.

       -msahf
           This option will enable GCC to use SAHF instruction in generated 64-bit code.
           Early Intel CPUs with Intel 64 lacked LAHF and SAHF instructions supported by
           AMD64 until introduction of Pentium 4 G1 step in December 2005.  LAHF and SAHF
           are load and store instructions, respectively, for certain status flags.  In
           64-bit mode, SAHF instruction is used to optimize "fmod", "drem" or "remainder"
           built-in functions: see Other Builtins for details.

       -mmovbe
           This option will enable GCC to use movbe instruction to implement
           "__builtin_bswap32" and "__builtin_bswap64".

       -mcrc32
           This option will enable built-in functions, "__builtin_ia32_crc32qi",
           "__builtin_ia32_crc32hi". "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di"
           to generate the crc32 machine instruction.

       -mrecip
           This option will enable GCC to use RCPSS and RSQRTSS instructions (and their
           vectorized variants RCPPS and RSQRTPS) with an additional Newton-Raphson step
           to increase precision instead of DIVSS and SQRTSS (and their vectorized
           variants) for single precision floating point arguments.  These instructions
           are generated only when -funsafe-math-optimizations is enabled together with
           -finite-math-only and -fno-trapping-math.  Note that while the throughput of
           the sequence is higher than the throughput of the non-reciprocal instruction,
           the precision of the sequence can be decreased by up to 2 ulp (i.e. the inverse
           of 1.0 equals 0.99999994).

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external
           library.  Supported types are "svml" for the Intel short vector math library
           and "acml" for the AMD math core library style of interfacing.  GCC will
           currently emit calls to "vmldExp2", "vmldLn2", "vmldLog102", "vmldLog102",
           "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2",
           "vmldSinh2", "vmldSin2", "vmldAsinh2", "vmldAsin2", "vmldCosh2", "vmldCos2",
           "vmldAcosh2", "vmldAcos2", "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104",
           "vmlsPow4", "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4",
           "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4", "vmlsCos4",
           "vmlsAcosh4" and "vmlsAcos4" for corresponding function type when
           -mveclibabi=svml is used and "__vrd2_sin", "__vrd2_cos", "__vrd2_exp",
           "__vrd2_log", "__vrd2_log2", "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf",
           "__vrs4_expf", "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf"
           for corresponding function type when -mveclibabi=acml is used. Both
           -ftree-vectorize and -funsafe-math-optimizations have to be enabled. A SVML or
           ACML ABI compatible library will have to be specified at link time.

       -mpush-args
       -mno-push-args
           Use PUSH operations to store outgoing parameters.  This method is shorter and
           usually equally fast as method using SUB/MOV operations and is enabled by
           default.  In some cases disabling it may improve performance because of
           improved scheduling and reduced dependencies.

       -maccumulate-outgoing-args
           If enabled, the maximum amount of space required for outgoing arguments will be
           computed in the function prologue.  This is faster on most modern CPUs because
           of reduced dependencies, improved scheduling and reduced stack usage when
           preferred stack boundary is not equal to 2.  The drawback is a notable increase
           in code size.  This switch implies -mno-push-args.

       -mthreads
           Support thread-safe exception handling on Mingw32.  Code that relies on thread-
           safe exception handling must compile and link all code with the -mthreads
           option.  When compiling, -mthreads defines -D_MT; when linking, it links in a
           special thread helper library -lmingwthrd which cleans up per thread exception
           handling data.

       -mno-align-stringops
           Do not align destination of inlined string operations.  This switch reduces
           code size and improves performance in case the destination is already aligned,
           but GCC doesn't know about it.

       -minline-all-stringops
           By default GCC inlines string operations only when destination is known to be
           aligned at least to 4 byte boundary.  This enables more inlining, increase code
           size, but may improve performance of code that depends on fast memcpy, strlen
           and memset for short lengths.

       -minline-stringops-dynamically
           For string operation of unknown size, inline runtime checks so for small blocks
           inline code is used, while for large blocks library call is used.

       -mstringop-strategy=alg
           Overwrite internal decision heuristic about particular algorithm to inline
           string operation with.  The allowed values are "rep_byte", "rep_4byte",
           "rep_8byte" for expanding using i386 "rep" prefix of specified size,
           "byte_loop", "loop", "unrolled_loop" for expanding inline loop, "libcall" for
           always expanding library call.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up and restore frame pointers and makes an extra
           register available in leaf functions.  The option -fomit-frame-pointer removes
           the frame pointer for all functions which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
           Controls whether TLS variables may be accessed with offsets from the TLS
           segment register (%gs for 32-bit, %fs for 64-bit), or whether the thread base
           pointer must be added.  Whether or not this is legal depends on the operating
           system, and whether it maps the segment to cover the entire TLS area.

           For systems that use GNU libc, the default is on.

       -msse2avx
       -mno-sse2avx
           Specify that the assembler should encode SSE instructions with VEX prefix.  The
           option -mavx turns this on by default.

       These -m switches are supported in addition to the above on AMD x86-64 processors
       in 64-bit environments.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets
           int, long and pointer to 32 bits and generates code that runs on any i386
           system.  The 64-bit environment sets int to 32 bits and long and pointer to 64
           bits and generates code for AMD's x86-64 architecture. For darwin only the -m64
           option turns off the -fno-pic and -mdynamic-no-pic options.

       -mno-red-zone
           Do not use a so called red zone for x86-64 code.  The red zone is mandated by
           the x86-64 ABI, it is a 128-byte area beyond the location of the stack pointer
           that will not be modified by signal or interrupt handlers and therefore can be
           used for temporary data without adjusting the stack pointer.  The flag
           -mno-red-zone disables this red zone.

       -mcmodel=small
           Generate code for the small code model: the program and its symbols must be
           linked in the lower 2 GB of the address space.  Pointers are 64 bits.  Programs
           can be statically or dynamically linked.  This is the default code model.

       -mcmodel=kernel
           Generate code for the kernel code model.  The kernel runs in the negative 2 GB
           of the address space.  This model has to be used for Linux kernel code.

       -mcmodel=medium
           Generate code for the medium model: The program is linked in the lower 2 GB of
           the address space.  Small symbols are also placed there.  Symbols with sizes
           larger than -mlarge-data-threshold are put into large data or bss sections and
           can be located above 2GB.  Programs can be statically or dynamically linked.

       -mcmodel=large
           Generate code for the large model: This model makes no assumptions about
           addresses and sizes of sections.

   i386 and x86-64 Windows Options
       These additional options are available for Windows targets:

       -mconsole
           This option is available for Cygwin and MinGW targets.  It specifies that a
           console application is to be generated, by instructing the linker to set the PE
           header subsystem type required for console applications.  This is the default
           behaviour for Cygwin and MinGW targets.

       -mcygwin
           This option is available for Cygwin targets.  It specifies that the Cygwin
           internal interface is to be used for predefined preprocessor macros, C runtime
           libraries and related linker paths and options.  For Cygwin targets this is the
           default behaviour.  This option is deprecated and will be removed in a future
           release.

       -mno-cygwin
           This option is available for Cygwin targets.  It specifies that the MinGW
           internal interface is to be used instead of Cygwin's, by setting MinGW-related
           predefined macros and linker paths and default library options.  This option is
           deprecated and will be removed in a future release.

       -mdll
           This option is available for Cygwin and MinGW targets.  It specifies that a DLL
           - a dynamic link library - is to be generated, enabling the selection of the
           required runtime startup object and entry point.

       -mnop-fun-dllimport
           This option is available for Cygwin and MinGW targets.  It specifies that the
           dllimport attribute should be ignored.

       -mthread
           This option is available for MinGW targets. It specifies that MinGW-specific
           thread support is to be used.

       -mwin32
           This option is available for Cygwin and MinGW targets.  It specifies that the
           typical Windows pre-defined macros are to be set in the pre-processor, but does
           not influence the choice of runtime library/startup code.

       -mwindows
           This option is available for Cygwin and MinGW targets.  It specifies that a GUI
           application is to be generated by instructing the linker to set the PE header
           subsystem type appropriately.

       See also under i386 and x86-64 Options for standard options.

   IA-64 Options
       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big endian target.  This is the default for HP-UX.

       -mlittle-endian
           Generate code for a little endian target.  This is the default for AIX5 and
           GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
           Generate code that does not use a global pointer register.  The result is not
           position independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after volatile asm
           statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the stacked registers.
           This may make assembler output more readable.

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data section.  This may be
           useful for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer value.  This is useful
           when compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies -mconstant-gp.  This is
           useful when compiling firmware code.

       -minline-float-divide-min-latency
           Generate code for inline divides of floating point values using the minimum
           latency algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating point values using the maximum
           throughput algorithm.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the minimum latency
           algorithm.

       -minline-int-divide-max-throughput
           Generate code for inline divides of integer values using the maximum throughput
           algorithm.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum throughput algorithm.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF2 line number debugging
           info.  This may be useful when not using the GNU assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow stop bits to be placed earlier than immediately preceding the instruction
           that triggered the stop bit.  This can improve instruction scheduling, but does
           not always do so.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed
           register is one that the register allocator can not use.  This is useful when
           compiling kernel code.  A register range is specified as two registers
           separated by a dash.  Multiple register ranges can be specified separated by a
           comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14, 22, and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid values are itanium,
           itanium1, merced, itanium2, and mckinley.

       -mt
       -pthread
           Add support for multithreading using the POSIX threads library.  This option
           sets flags for both the preprocessor and linker.  It does not affect the thread
           safety of object code produced by the compiler or that of libraries supplied
           with it.  These are HP-UX specific flags.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets
           int, long and pointer to 32 bits.  The 64-bit environment sets int to 32 bits
           and long and pointer to 64 bits.  These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This will result in
           generation of the ld.a instructions and the corresponding check instructions
           (ld.c / chk.a).  The default is 'disable'.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This will result in
           generation of the ld.a instructions and the corresponding check instructions
           (ld.c / chk.a).  The default is 'enable'.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.  This feature is available only
           during region scheduling (i.e. before reload).  This will result in generation
           of the ld.s instructions and the corresponding check instructions chk.s .  The
           default is 'disable'.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on
           the data speculative loads before reload.  This is effective only with
           -msched-br-data-spec enabled.  The default is 'enable'.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on
           the data speculative loads after reload.  This is effective only with
           -msched-ar-data-spec enabled.  The default is 'enable'.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on
           the control speculative loads.  This is effective only with
           -msched-control-spec enabled.  The default is 'enable'.

       -msched-ldc
       -mno-sched-ldc
           (En/Dis)able use of simple data speculation checks ld.c .  If disabled, only
           chk.a instructions will be emitted to check data speculative loads.  The
           default is 'enable'.

       -mno-sched-control-ldc
       -msched-control-ldc
           (Dis/En)able use of ld.c instructions to check control speculative loads.  If
           enabled, in case of control speculative load with no speculatively scheduled
           dependent instructions this load will be emitted as ld.sa and ld.c will be used
           to check it.  The default is 'disable'.

       -mno-sched-spec-verbose
       -msched-spec-verbose
           (Dis/En)able printing of the information about speculative motions.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data speculative instructions will be chosen for schedule only if
           there are no other choices at the moment.  This will make the use of the data
           speculation much more conservative.  The default is 'disable'.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control speculative instructions will be chosen for schedule only
           if there are no other choices at the moment.  This will make the use of the
           control speculation much more conservative.  The default is 'disable'.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If enabled, speculative dependencies will be considered during computation of
           the instructions priorities.  This will make the use of the speculation a bit
           more conservative.  The default is 'disable'.

   M32C Options
       -mcpu=name
           Select the CPU for which code is generated.  name may be one of r8c for the
           R8C/Tiny series, m16c for the M16C (up to /60) series, m32cm for the M16C/80
           series, or m32c for the M32C/80 series.

       -msim
           Specifies that the program will be run on the simulator.  This causes an
           alternate runtime library to be linked in which supports, for example, file
           I/O.  You must not use this option when generating programs that will run on
           real hardware; you must provide your own runtime library for whatever I/O
           functions are needed.

       -memregs=number
           Specifies the number of memory-based pseudo-registers GCC will use during code
           generation.  These pseudo-registers will be used like real registers, so there
           is a tradeoff between GCC's ability to fit the code into available registers,
           and the performance penalty of using memory instead of registers.  Note that
           all modules in a program must be compiled with the same value for this option.
           Because of that, you must not use this option with the default runtime
           libraries gcc builds.

   M32R/D Options
       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory (so that their addresses
           can be loaded with the "ld24" instruction), and assume all subroutines are
           reachable with the "bl" instruction.  This is the default.

           The addressability of a particular object can be set with the "model"
           attribute.

       -mmodel=medium
           Assume objects may be anywhere in the 32-bit address space (the compiler will
           generate "seth/add3" instructions to load their addresses), and assume all
           subroutines are reachable with the "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in the 32-bit address space (the compiler will
           generate "seth/add3" instructions to load their addresses), and assume
           subroutines may not be reachable with the "bl" instruction (the compiler will
           generate the much slower "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable use of the small data area.  Variables will be put into one of .data,
           bss, or .rodata (unless the "section" attribute has been specified).  This is
           the default.

           The small data area consists of sections .sdata and .sbss.  Objects may be
           explicitly put in the small data area with the "section" attribute using one of
           these sections.

       -msdata=sdata
           Put small global and static data in the small data area, but do not generate
           special code to reference them.

       -msdata=use
           Put small global and static data in the small data area, and generate special
           instructions to reference them.

       -G num
           Put global and static objects less than or equal to num bytes into the small
           data or bss sections instead of the normal data or bss sections.  The default
           value of num is 8.  The -msdata option must be set to one of sdata or use for
           this option to have any effect.

           All modules should be compiled with the same -G num value.  Compiling with
           different values of num may or may not work; if it doesn't the linker will give
           an error message---incorrect code will not be generated.

       -mdebug
           Makes the M32R specific code in the compiler display some statistics that might
           help in debugging programs.

       -malign-loops
           Align all loops to a 32-byte boundary.

       -mno-align-loops
           Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
           Issue number instructions per cycle.  number can only be 1 or 2.

       -mbranch-cost=number
           number can only be 1 or 2.  If it is 1 then branches will be preferred over
           conditional code, if it is 2, then the opposite will apply.

       -mflush-trap=number
           Specifies the trap number to use to flush the cache.  The default is 12.  Valid
           numbers are between 0 and 15 inclusive.

       -mno-flush-trap
           Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
           Specifies the name of the operating system function to call to flush the cache.
           The default is _flush_cache, but a function call will only be used if a trap is
           not available.

       -mno-flush-func
           Indicates that there is no OS function for flushing the cache.

   M680x0 Options
       These are the -m options defined for M680x0 and ColdFire processors.  The default
       settings depend on which architecture was selected when the compiler was
       configured; the defaults for the most common choices are given below.

       -march=arch
           Generate code for a specific M680x0 or ColdFire instruction set architecture.
           Permissible values of arch for M680x0 architectures are: 68000, 68010, 68020,
           68030, 68040, 68060 and cpu32.  ColdFire architectures are selected according
           to Freescale's ISA classification and the permissible values are: isaa,
           isaaplus, isab and isac.

           gcc defines a macro __mcfarch__ whenever it is generating code for a ColdFire
           target.  The arch in this macro is one of the -march arguments given above.

           When used together, -march and -mtune select code that runs on a family of
           similar processors but that is optimized for a particular microarchitecture.

       -mcpu=cpu
           Generate code for a specific M680x0 or ColdFire processor.  The M680x0 cpus
           are: 68000, 68010, 68020, 68030, 68040, 68060, 68302, 68332 and cpu32.  The
           ColdFire cpus are given by the table below, which also classifies the CPUs into
           families:

           Family : -mcpu arguments
           51qe : 51qe
           5206 : 5202 5204 5206
           5206e : 5206e
           5208 : 5207 5208
           5211a : 5210a 5211a
           5213 : 5211 5212 5213
           5216 : 5214 5216
           52235 : 52230 52231 52232 52233 52234 52235
           5225 : 5224 5225
           5235 : 5232 5233 5234 5235 523x
           5249 : 5249
           5250 : 5250
           5271 : 5270 5271
           5272 : 5272
           5275 : 5274 5275
           5282 : 5280 5281 5282 528x
           5307 : 5307
           5329 : 5327 5328 5329 532x
           5373 : 5372 5373 537x
           5407 : 5407
           5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484 5485

           -mcpu=cpu overrides -march=arch if arch is compatible with cpu.  Other
           combinations of -mcpu and -march are rejected.

           gcc defines the macro __mcf_cpu_cpu when ColdFire target cpu is selected.  It
           also defines __mcf_family_family, where the value of family is given by the
           table above.

       -mtune=tune
           Tune the code for a particular microarchitecture, within the constraints set by
           -march and -mcpu.  The M680x0 microarchitectures are: 68000, 68010, 68020,
           68030, 68040, 68060 and cpu32.  The ColdFire microarchitectures are: cfv1,
           cfv2, cfv3, cfv4 and cfv4e.

           You can also use -mtune=68020-40 for code that needs to run relatively well on
           68020, 68030 and 68040 targets.  -mtune=68020-60 is similar but includes 68060
           targets as well.  These two options select the same tuning decisions as
           -m68020-40 and -m68020-60 respectively.

           gcc defines the macros __mcarch and __mcarch__ when tuning for 680x0
           architecture arch.  It also defines mcarch unless either -ansi or a non-GNU
           -std option is used.  If gcc is tuning for a range of architectures, as
           selected by -mtune=68020-40 or -mtune=68020-60, it defines the macros for every
           architecture in the range.

           gcc also defines the macro __muarch__ when tuning for ColdFire
           microarchitecture uarch, where uarch is one of the arguments given above.

       -m68000
       -mc68000
           Generate output for a 68000.  This is the default when the compiler is
           configured for 68000-based systems.  It is equivalent to -march=68000.

           Use this option for microcontrollers with a 68000 or EC000 core, including the
           68008, 68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
           Generate output for a 68010.  This is the default when the compiler is
           configured for 68010-based systems.  It is equivalent to -march=68010.

       -m68020
       -mc68020
           Generate output for a 68020.  This is the default when the compiler is
           configured for 68020-based systems.  It is equivalent to -march=68020.

       -m68030
           Generate output for a 68030.  This is the default when the compiler is
           configured for 68030-based systems.  It is equivalent to -march=68030.

       -m68040
           Generate output for a 68040.  This is the default when the compiler is
           configured for 68040-based systems.  It is equivalent to -march=68040.

           This option inhibits the use of 68881/68882 instructions that have to be
           emulated by software on the 68040.  Use this option if your 68040 does not have
           code to emulate those instructions.

       -m68060
           Generate output for a 68060.  This is the default when the compiler is
           configured for 68060-based systems.  It is equivalent to -march=68060.

           This option inhibits the use of 68020 and 68881/68882 instructions that have to
           be emulated by software on the 68060.  Use this option if your 68060 does not
           have code to emulate those instructions.

       -mcpu32
           Generate output for a CPU32.  This is the default when the compiler is
           configured for CPU32-based systems.  It is equivalent to -march=cpu32.

           Use this option for microcontrollers with a CPU32 or CPU32+ core, including the
           68330, 68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360.

       -m5200
           Generate output for a 520X ColdFire CPU.  This is the default when the compiler
           is configured for 520X-based systems.  It is equivalent to -mcpu=5206, and is
           now deprecated in favor of that option.

           Use this option for microcontroller with a 5200 core, including the MCF5202,
           MCF5203, MCF5204 and MCF5206.

       -m5206e
           Generate output for a 5206e ColdFire CPU.  The option is now deprecated in
           favor of the equivalent -mcpu=5206e.

       -m528x
           Generate output for a member of the ColdFire 528X family.  The option is now
           deprecated in favor of the equivalent -mcpu=528x.

       -m5307
           Generate output for a ColdFire 5307 CPU.  The option is now deprecated in favor
           of the equivalent -mcpu=5307.

       -m5407
           Generate output for a ColdFire 5407 CPU.  The option is now deprecated in favor
           of the equivalent -mcpu=5407.

       -mcfv4e
           Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).  This includes
           use of hardware floating point instructions.  The option is equivalent to
           -mcpu=547x, and is now deprecated in favor of that option.

       -m68020-40
           Generate output for a 68040, without using any of the new instructions.  This
           results in code which can run relatively efficiently on either a 68020/68881 or
           a 68030 or a 68040.  The generated code does use the 68881 instructions that
           are emulated on the 68040.

           The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
           Generate output for a 68060, without using any of the new instructions.  This
           results in code which can run relatively efficiently on either a 68020/68881 or
           a 68030 or a 68040.  The generated code does use the 68881 instructions that
           are emulated on the 68060.

           The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
           Generate floating-point instructions.  This is the default for 68020 and above,
           and for ColdFire devices that have an FPU.  It defines the macro __HAVE_68881__
           on M680x0 targets and __mcffpu__ on ColdFire targets.

       -msoft-float
           Do not generate floating-point instructions; use library calls instead.  This
           is the default for 68000, 68010, and 68832 targets.  It is also the default for
           ColdFire devices that have no FPU.

       -mdiv
       -mno-div
           Generate (do not generate) ColdFire hardware divide and remainder instructions.
           If -march is used without -mcpu, the default is "on" for ColdFire architectures
           and "off" for M680x0 architectures.  Otherwise, the default is taken from the
           target CPU (either the default CPU, or the one specified by -mcpu).  For
           example, the default is "off" for -mcpu=5206 and "on" for -mcpu=5206e.

           gcc defines the macro __mcfhwdiv__ when this option is enabled.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".  Additionally,
           parameters passed on the stack are also aligned to a 16-bit boundary even on
           targets whose API mandates promotion to 32-bit.

       -mno-short
           Do not consider type "int" to be 16 bits wide.  This is the default.

       -mnobitfield
       -mno-bitfield
           Do not use the bit-field instructions.  The -m68000, -mcpu32 and -m5200 options
           imply -mnobitfield.

       -mbitfield
           Do use the bit-field instructions.  The -m68020 option implies -mbitfield.
           This is the default if you use a configuration designed for a 68020.

       -mrtd
           Use a different function-calling convention, in which functions that take a
           fixed number of arguments return with the "rtd" instruction, which pops their
           arguments while returning.  This saves one instruction in the caller since
           there is no need to pop the arguments there.

           This calling convention is incompatible with the one normally used on Unix, so
           you cannot use it if you need to call libraries compiled with the Unix
           compiler.

           Also, you must provide function prototypes for all functions that take variable
           numbers of arguments (including "printf"); otherwise incorrect code will be
           generated for calls to those functions.

           In addition, seriously incorrect code will result if you call a function with
           too many arguments.  (Normally, extra arguments are harmlessly ignored.)

           The "rtd" instruction is supported by the 68010, 68020, 68030, 68040, 68060 and
           CPU32 processors, but not by the 68000 or 5200.

       -mno-rtd
           Do not use the calling conventions selected by -mrtd.  This is the default.

       -malign-int
       -mno-align-int
           Control whether GCC aligns "int", "long", "long long", "float", "double", and
           "long double" variables on a 32-bit boundary (-malign-int) or a 16-bit boundary
           (-mno-align-int).  Aligning variables on 32-bit boundaries produces code that
           runs somewhat faster on processors with 32-bit busses at the expense of more
           memory.

           Warning: if you use the -malign-int switch, GCC will align structures
           containing the above types  differently than most published application binary
           interface specifications for the m68k.

       -mpcrel
           Use the pc-relative addressing mode of the 68000 directly, instead of using a
           global offset table.  At present, this option implies -fpic, allowing at most a
           16-bit offset for pc-relative addressing.  -fPIC is not presently supported
           with -mpcrel, though this could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
           Do not (do) assume that unaligned memory references will be handled by the
           system.

       -msep-data
           Generate code that allows the data segment to be located in a different area of
           memory from the text segment.  This allows for execute in place in an
           environment without virtual memory management.  This option implies -fPIC.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.
           This is the default.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This
           allows for execute in place and shared libraries in an environment without
           virtual memory management.  This option implies -fPIC.

       -mno-id-shared-library
           Generate code that doesn't assume ID based shared libraries are being used.
           This is the default.

       -mshared-library-id=n
           Specified the identification number of the ID based shared library being
           compiled.  Specifying a value of 0 will generate more compact code, specifying
           other values will force the allocation of that number to the current library
           but is no more space or time efficient than omitting this option.

       -mxgot
       -mno-xgot
           When generating position-independent code for ColdFire, generate code that
           works if the GOT has more than 8192 entries.  This code is larger and slower
           than code generated without this option.  On M680x0 processors, this option is
           not needed; -fPIC suffices.

           GCC normally uses a single instruction to load values from the GOT.  While this
           is relatively efficient, it only works if the GOT is smaller than about 64k.
           Anything larger causes the linker to report an error such as:

                   relocation truncated to fit: R_68K_GOT16O foobar

           If this happens, you should recompile your code with -mxgot.  It should then
           work with very large GOTs.  However, code generated with -mxgot is less
           efficient, since it takes 4 instructions to fetch the value of a global symbol.

           Note that some linkers, including newer versions of the GNU linker, can create
           multiple GOTs and sort GOT entries.  If you have such a linker, you should only
           need to use -mxgot when compiling a single object file that accesses more than
           8192 GOT entries.  Very few do.

           These options have no effect unless GCC is generating position-independent
           code.

   M68hc1x Options
       These are the -m options defined for the 68hc11 and 68hc12 microcontrollers.  The
       default values for these options depends on which style of microcontroller was
       selected when the compiler was configured; the defaults for the most common choices
       are given below.

       -m6811
       -m68hc11
           Generate output for a 68HC11.  This is the default when the compiler is
           configured for 68HC11-based systems.

       -m6812
       -m68hc12
           Generate output for a 68HC12.  This is the default when the compiler is
           configured for 68HC12-based systems.

       -m68S12
       -m68hcs12
           Generate output for a 68HCS12.

       -mauto-incdec
           Enable the use of 68HC12 pre and post auto-increment and auto-decrement
           addressing modes.

       -minmax
       -nominmax
           Enable the use of 68HC12 min and max instructions.

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed to be far away,
           the compiler will use the "call" instruction to call a function and the "rtc"
           instruction for returning.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".

       -msoft-reg-count=count
           Specify the number of pseudo-soft registers which are used for the code
           generation.  The maximum number is 32.  Using more pseudo-soft register may or
           may not result in better code depending on the program.  The default is 4 for
           68HC11 and 2 for 68HC12.

   MCore Options
       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
           Inline constants into the code stream if it can be done in two instructions or
           less.

       -mdiv
       -mno-div
           Use the divide instruction.  (Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
           Allow arbitrary sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
           Always treat bit-fields as int-sized.

       -m4byte-functions
       -mno-4byte-functions
           Force all functions to be aligned to a four byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
           Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
           Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
           Generate code for a little endian target.

       -m210
       -m340
           Generate code for the 210 processor.

       -mno-lsim
           Assume that run-time support has been provided and so omit the simulator
           library (libsim.a) from the linker command line.

       -mstack-increment=size
           Set the maximum amount for a single stack increment operation.  Large values
           can increase the speed of programs which contain functions that need a large
           amount of stack space, but they can also trigger a segmentation fault if the
           stack is extended too much.  The default value is 0x1000.

   MIPS Options
       -EB Generate big-endian code.

       -EL Generate little-endian code.  This is the default for mips*el-*-*
           configurations.

       -march=arch
           Generate code that will run on arch, which can be the name of a generic MIPS
           ISA, or the name of a particular processor.  The ISA names are: mips1, mips2,
           mips3, mips4, mips32, mips32r2, mips64 and mips64r2.  The processor names are:
           4kc, 4km, 4kp, 4ksc, 4kec, 4kem, 4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1,
           24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 74kc, 74kf2_1,
           74kf1_1, 74kf3_2, loongson2e, loongson2f, m4k, octeon, orion, r2000, r3000,
           r3900, r4000, r4400, r4600, r4650, r6000, r8000, rm7000, rm9000, r10000,
           r12000, r14000, r16000, sb1, sr71000, vr4100, vr4111, vr4120, vr4130, vr4300,
           vr5000, vr5400, vr5500 and xlr.  The special value from-abi selects the most
           compatible architecture for the selected ABI (that is, mips1 for 32-bit ABIs
           and mips3 for 64-bit ABIs).

           Native Linux/GNU toolchains also support the value native, which selects the
           best architecture option for the host processor.  -march=native has no effect
           if GCC does not recognize the processor.

           In processor names, a final 000 can be abbreviated as k (for example,
           -march=r2k).  Prefixes are optional, and vr may be written r.

           Names of the form nf2_1 refer to processors with FPUs clocked at half the rate
           of the core, names of the form nf1_1 refer to processors with FPUs clocked at
           the same rate as the core, and names of the form nf3_2 refer to processors with
           FPUs clocked a ratio of 3:2 with respect to the core.  For compatibility
           reasons, nf is accepted as a synonym for nf2_1 while nx and bfx are accepted as
           synonyms for nf1_1.

           GCC defines two macros based on the value of this option.  The first is
           _MIPS_ARCH, which gives the name of target architecture, as a string.  The
           second has the form _MIPS_ARCH_foo, where foo is the capitalized value of
           _MIPS_ARCH.  For example, -march=r2000 will set _MIPS_ARCH to "r2000" and
           define the macro _MIPS_ARCH_R2000.

           Note that the _MIPS_ARCH macro uses the processor names given above.  In other
           words, it will have the full prefix and will not abbreviate 000 as k.  In the
           case of from-abi, the macro names the resolved architecture (either "mips1" or
           "mips3").  It names the default architecture when no -march option is given.

       -mtune=arch
           Optimize for arch.  Among other things, this option controls the way
           instructions are scheduled, and the perceived cost of arithmetic operations.
           The list of arch values is the same as for -march.

           When this option is not used, GCC will optimize for the processor specified by
           -march.  By using -march and -mtune together, it is possible to generate code
           that will run on a family of processors, but optimize the code for one
           particular member of that family.

           -mtune defines the macros _MIPS_TUNE and _MIPS_TUNE_foo, which work in the same
           way as the -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -mips32r2
           Equivalent to -march=mips32r2.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips16
       -mno-mips16
           Generate (do not generate) MIPS16 code.  If GCC is targetting a MIPS32 or
           MIPS64 architecture, it will make use of the MIPS16e ASE.

           MIPS16 code generation can also be controlled on a per-function basis by means
           of "mips16" and "nomips16" attributes.

       -mflip-mips16
           Generate MIPS16 code on alternating functions.  This option is provided for
           regression testing of mixed MIPS16/non-MIPS16 code generation, and is not
           intended for ordinary use in compiling user code.

       -minterlink-mips16
       -mno-interlink-mips16
           Require (do not require) that non-MIPS16 code be link-compatible with MIPS16
           code.

           For example, non-MIPS16 code cannot jump directly to MIPS16 code; it must
           either use a call or an indirect jump.  -minterlink-mips16 therefore disables
           direct jumps unless GCC knows that the target of the jump is not MIPS16.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
           Generate code for the given ABI.

           Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally generates
           64-bit code when you select a 64-bit architecture, but you can use -mgp32 to
           get 32-bit code instead.

           For information about the O64 ABI, see
           <http://gcc.gnu.org/projects/mipso64-abi.html>.

           GCC supports a variant of the o32 ABI in which floating-point registers are 64
           rather than 32 bits wide.  You can select this combination with -mabi=32
           -mfp64.  This ABI relies on the mthc1 and mfhc1 instructions and is therefore
           only supported for MIPS32R2 processors.

           The register assignments for arguments and return values remain the same, but
           each scalar value is passed in a single 64-bit register rather than a pair of
           32-bit registers.  For example, scalar floating-point values are returned in
           $f0 only, not a $f0/$f1 pair.  The set of call-saved registers also remains the
           same, but all 64 bits are saved.

       -mabicalls
       -mno-abicalls
           Generate (do not generate) code that is suitable for SVR4-style dynamic
           objects.  -mabicalls is the default for SVR4-based systems.

       -mshared
       -mno-shared
           Generate (do not generate) code that is fully position-independent, and that
           can therefore be linked into shared libraries.  This option only affects
           -mabicalls.

           All -mabicalls code has traditionally been position-independent, regardless of
           options like -fPIC and -fpic.  However, as an extension, the GNU toolchain
           allows executables to use absolute accesses for locally-binding symbols.  It
           can also use shorter GP initialization sequences and generate direct calls to
           locally-defined functions.  This mode is selected by -mno-shared.

           -mno-shared depends on binutils 2.16 or higher and generates objects that can
           only be linked by the GNU linker.  However, the option does not affect the ABI
           of the final executable; it only affects the ABI of relocatable objects.  Using
           -mno-shared will generally make executables both smaller and quicker.

           -mshared is the default.

       -mplt
       -mno-plt
           Assume (do not assume) that the static and dynamic linkers support PLTs and
           copy relocations.  This option only affects -mno-shared -mabicalls.  For the
           n64 ABI, this option has no effect without -msym32.

           You can make -mplt the default by configuring GCC with --with-mips-plt.  The
           default is -mno-plt otherwise.

       -mxgot
       -mno-xgot
           Lift (do not lift) the usual restrictions on the size of the global offset
           table.

           GCC normally uses a single instruction to load values from the GOT.  While this
           is relatively efficient, it will only work if the GOT is smaller than about
           64k.  Anything larger will cause the linker to report an error such as:

                   relocation truncated to fit: R_MIPS_GOT16 foobar

           If this happens, you should recompile your code with -mxgot.  It should then
           work with very large GOTs, although it will also be less efficient, since it
           will take three instructions to fetch the value of a global symbol.

           Note that some linkers can create multiple GOTs.  If you have such a linker,
           you should only need to use -mxgot when a single object file accesses more than
           64k's worth of GOT entries.  Very few do.

           These options have no effect unless GCC is generating position independent
           code.

       -mgp32
           Assume that general-purpose registers are 32 bits wide.

       -mgp64
           Assume that general-purpose registers are 64 bits wide.

       -mfp32
           Assume that floating-point registers are 32 bits wide.

       -mfp64
           Assume that floating-point registers are 64 bits wide.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do not use floating-point coprocessor instructions.  Implement floating-point
           calculations using library calls instead.

       -msingle-float
           Assume that the floating-point coprocessor only supports single-precision
           operations.

       -mdouble-float
           Assume that the floating-point coprocessor supports double-precision
           operations.  This is the default.

       -mllsc
       -mno-llsc
           Use (do not use) ll, sc, and sync instructions to implement atomic memory
           built-in functions.  When neither option is specified, GCC will use the
           instructions if the target architecture supports them.

           -mllsc is useful if the runtime environment can emulate the instructions and
           -mno-llsc can be useful when compiling for nonstandard ISAs.  You can make
           either option the default by configuring GCC with --with-llsc and
           --without-llsc respectively.  --with-llsc is the default for some
           configurations; see the installation documentation for details.

       -mdsp
       -mno-dsp
           Use (do not use) revision 1 of the MIPS DSP ASE.
             This option defines the preprocessor macro __mips_dsp.  It also defines
           __mips_dsp_rev to 1.

       -mdspr2
       -mno-dspr2
           Use (do not use) revision 2 of the MIPS DSP ASE.
             This option defines the preprocessor macros __mips_dsp and __mips_dspr2.  It
           also defines __mips_dsp_rev to 2.

       -msmartmips
       -mno-smartmips
           Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
           Use (do not use) paired-single floating-point instructions.
             This option requires hardware floating-point support to be enabled.

       -mdmx
       -mno-mdmx
           Use (do not use) MIPS Digital Media Extension instructions.  This option can
           only be used when generating 64-bit code and requires hardware floating-point
           support to be enabled.

       -mips3d
       -mno-mips3d
           Use (do not use) the MIPS-3D ASE.  The option -mips3d implies -mpaired-single.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading instructions.

       -mlong64
           Force "long" types to be 64 bits wide.  See -mlong32 for an explanation of the
           default and the way that the pointer size is determined.

       -mlong32
           Force "long", "int", and pointer types to be 32 bits wide.

           The default size of "int"s, "long"s and pointers depends on the ABI.  All the
           supported ABIs use 32-bit "int"s.  The n64 ABI uses 64-bit "long"s, as does the
           64-bit EABI; the others use 32-bit "long"s.  Pointers are the same size as
           "long"s, or the same size as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
           Assume (do not assume) that all symbols have 32-bit values, regardless of the
           selected ABI.  This option is useful in combination with -mabi=64 and
           -mno-abicalls because it allows GCC to generate shorter and faster references
           to symbolic addresses.

       -G num
           Put definitions of externally-visible data in a small data section if that data
           is no bigger than num bytes.  GCC can then access the data more efficiently;
           see -mgpopt for details.

           The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
           Extend (do not extend) the -G behavior to local data too, such as to static
           variables in C.  -mlocal-sdata is the default for all configurations.

           If the linker complains that an application is using too much small data, you
           might want to try rebuilding the less performance-critical parts with
           -mno-local-sdata.  You might also want to build large libraries with
           -mno-local-sdata, so that the libraries leave more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
           Assume (do not assume) that externally-defined data will be in a small data
           section if that data is within the -G limit.  -mextern-sdata is the default for
           all configurations.

           If you compile a module Mod with -mextern-sdata -G num -mgpopt, and Mod
           references a variable Var that is no bigger than num bytes, you must make sure
           that Var is placed in a small data section.  If Var is defined by another
           module, you must either compile that module with a high-enough -G setting or
           attach a "section" attribute to Var's definition.  If Var is common, you must
           link the application with a high-enough -G setting.

           The easiest way of satisfying these restrictions is to compile and link every
           module with the same -G option.  However, you may wish to build a library that
           supports several different small data limits.  You can do this by compiling the
           library with the highest supported -G setting and additionally using
           -mno-extern-sdata to stop the library from making assumptions about externally-
           defined data.

       -mgpopt
       -mno-gpopt
           Use (do not use) GP-relative accesses for symbols that are known to be in a
           small data section; see -G, -mlocal-sdata and -mextern-sdata.  -mgpopt is the
           default for all configurations.

           -mno-gpopt is useful for cases where the $gp register might not hold the value
           of "_gp".  For example, if the code is part of a library that might be used in
           a boot monitor, programs that call boot monitor routines will pass an unknown
           value in $gp.  (In such situations, the boot monitor itself would usually be
           compiled with -G0.)

           -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
           Allocate variables to the read-only data section first if possible, then next
           in the small data section if possible, otherwise in data.  This gives slightly
           slower code than the default, but reduces the amount of RAM required when
           executing, and thus may be preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
           Put uninitialized "const" variables in the read-only data section.  This option
           is only meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
           Specify whether GCC may generate code that reads from executable sections.
           There are three possible settings:

           -mcode-readable=yes
               Instructions may freely access executable sections.  This is the default
               setting.

           -mcode-readable=pcrel
               MIPS16 PC-relative load instructions can access executable sections, but
               other instructions must not do so.  This option is useful on 4KSc and 4KSd
               processors when the code TLBs have the Read Inhibit bit set.  It is also
               useful on processors that can be configured to have a dual instruction/data
               SRAM interface and that, like the M4K, automatically redirect PC-relative
               loads to the instruction RAM.

           -mcode-readable=no
               Instructions must not access executable sections.  This option can be
               useful on targets that are configured to have a dual instruction/data SRAM
               interface but that (unlike the M4K) do not automatically redirect PC-
               relative loads to the instruction RAM.

       -msplit-addresses
       -mno-split-addresses
           Enable (disable) use of the "%hi()" and "%lo()" assembler relocation operators.
           This option has been superseded by -mexplicit-relocs but is retained for
           backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
           Use (do not use) assembler relocation operators when dealing with symbolic
           addresses.  The alternative, selected by -mno-explicit-relocs, is to use
           assembler macros instead.

           -mexplicit-relocs is the default if GCC was configured to use an assembler that
           supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
           Trap (do not trap) on integer division by zero.

           The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
           MIPS systems check for division by zero by generating either a conditional trap
           or a break instruction.  Using traps results in smaller code, but is only
           supported on MIPS II and later.  Also, some versions of the Linux kernel have a
           bug that prevents trap from generating the proper signal ("SIGFPE").  Use
           -mdivide-traps to allow conditional traps on architectures that support them
           and -mdivide-breaks to force the use of breaks.

           The default is usually -mdivide-traps, but this can be overridden at configure
           time using --with-divide=breaks.  Divide-by-zero checks can be completely
           disabled using -mno-check-zero-division.

       -mmemcpy
       -mno-memcpy
           Force (do not force) the use of "memcpy()" for non-trivial block moves.  The
           default is -mno-memcpy, which allows GCC to inline most constant-sized copies.

       -mlong-calls
       -mno-long-calls
           Disable (do not disable) use of the "jal" instruction.  Calling functions using
           "jal" is more efficient but requires the caller and callee to be in the same
           256 megabyte segment.

           This option has no effect on abicalls code.  The default is -mno-long-calls.

       -mmad
       -mno-mad
           Enable (disable) use of the "mad", "madu" and "mul" instructions, as provided
           by the R4650 ISA.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating point multiply-accumulate instructions,
           when they are available.  The default is -mfused-madd.

           When multiply-accumulate instructions are used, the intermediate product is
           calculated to infinite precision and is not subject to the FCSR Flush to Zero
           bit.  This may be undesirable in some circumstances.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user assembler files
           (with a .s suffix) when assembling them.

       -mfix-r4000
       -mno-fix-r4000
           Work around certain R4000 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

           -   A double-word or a variable shift may give an incorrect result if executed
               while an integer multiplication is in progress.

           -   An integer division may give an incorrect result if started in a delay slot
               of a taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
           Work around certain R4400 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
           Work around certain R10000 errata:

           -   "ll"/"sc" sequences may not behave atomically on revisions prior to 3.0.
               They may deadlock on revisions 2.6 and earlier.

           This option can only be used if the target architecture supports branch-likely
           instructions.  -mfix-r10000 is the default when -march=r10000 is used;
           -mno-fix-r10000 is the default otherwise.

       -mfix-vr4120
       -mno-fix-vr4120
           Work around certain VR4120 errata:

           -   "dmultu" does not always produce the correct result.

           -   "div" and "ddiv" do not always produce the correct result if one of the
               operands is negative.

           The workarounds for the division errata rely on special functions in libgcc.a.
           At present, these functions are only provided by the "mips64vr*-elf"
           configurations.

           Other VR4120 errata require a nop to be inserted between certain pairs of
           instructions.  These errata are handled by the assembler, not by GCC itself.

       -mfix-vr4130
           Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are implemented
           by the assembler rather than by GCC, although GCC will avoid using "mflo" and
           "mfhi" if the VR4130 "macc", "macchi", "dmacc" and "dmacchi" instructions are
           available instead.

       -mfix-sb1
       -mno-fix-sb1
           Work around certain SB-1 CPU core errata.  (This flag currently works around
           the SB-1 revision 2 "F1" and "F2" floating point errata.)

       -mr10k-cache-barrier=setting
           Specify whether GCC should insert cache barriers to avoid the side-effects of
           speculation on R10K processors.

           In common with many processors, the R10K tries to predict the outcome of a
           conditional branch and speculatively executes instructions from the "taken"
           branch.  It later aborts these instructions if the predicted outcome was wrong.
           However, on the R10K, even aborted instructions can have side effects.

           This problem only affects kernel stores and, depending on the system, kernel
           loads.  As an example, a speculatively-executed store may load the target
           memory into cache and mark the cache line as dirty, even if the store itself is
           later aborted.  If a DMA operation writes to the same area of memory before the
           "dirty" line is flushed, the cached data will overwrite the DMA-ed data.  See
           the R10K processor manual for a full description, including other potential
           problems.

           One workaround is to insert cache barrier instructions before every memory
           access that might be speculatively executed and that might have side effects
           even if aborted.  -mr10k-cache-barrier=setting controls GCC's implementation of
           this workaround.  It assumes that aborted accesses to any byte in the following
           regions will not have side effects:

           1.  the memory occupied by the current function's stack frame;

           2.  the memory occupied by an incoming stack argument;

           3.  the memory occupied by an object with a link-time-constant address.

           It is the kernel's responsibility to ensure that speculative accesses to these
           regions are indeed safe.

           If the input program contains a function declaration such as:

                   void foo (void);

           then the implementation of "foo" must allow "j foo" and "jal foo" to be
           executed speculatively.  GCC honors this restriction for functions it compiles
           itself.  It expects non-GCC functions (such as hand-written assembly code) to
           do the same.

           The option has three forms:

           -mr10k-cache-barrier=load-store
               Insert a cache barrier before a load or store that might be speculatively
               executed and that might have side effects even if aborted.

           -mr10k-cache-barrier=store
               Insert a cache barrier before a store that might be speculatively executed
               and that might have side effects even if aborted.

           -mr10k-cache-barrier=none
               Disable the insertion of cache barriers.  This is the default setting.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D caches, or to not call any
           such function.  If called, the function must take the same arguments as the
           common "_flush_func()", that is, the address of the memory range for which the
           cache is being flushed, the size of the memory range, and the number 3 (to
           flush both caches).  The default depends on the target GCC was configured for,
           but commonly is either _flush_func or __cpu_flush.

       mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This cost is
           only a heuristic and is not guaranteed to produce consistent results across
           releases.  A zero cost redundantly selects the default, which is based on the
           -mtune setting.

       -mbranch-likely
       -mno-branch-likely
           Enable or disable use of Branch Likely instructions, regardless of the default
           for the selected architecture.  By default, Branch Likely instructions may be
           generated if they are supported by the selected architecture.  An exception is
           for the MIPS32 and MIPS64 architectures and processors which implement those
           architectures; for those, Branch Likely instructions will not be generated by
           default because the MIPS32 and MIPS64 architectures specifically deprecate
           their use.

       -mfp-exceptions
       -mno-fp-exceptions
           Specifies whether FP exceptions are enabled.  This affects how we schedule FP
           instructions for some processors.  The default is that FP exceptions are
           enabled.

           For instance, on the SB-1, if FP exceptions are disabled, and we are emitting
           64-bit code, then we can use both FP pipes.  Otherwise, we can only use one FP
           pipe.

       -mvr4130-align
       -mno-vr4130-align
           The VR4130 pipeline is two-way superscalar, but can only issue two instructions
           together if the first one is 8-byte aligned.  When this option is enabled, GCC
           will align pairs of instructions that it thinks should execute in parallel.

           This option only has an effect when optimizing for the VR4130.  It normally
           makes code faster, but at the expense of making it bigger.  It is enabled by
           default at optimization level -O3.

   MMIX Options
       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify that intrinsic library functions are being compiled, passing all values
           in registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with respect to
           the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate code that passes function parameters and return values that (in the
           called function) are seen as registers $0 and up, as opposed to the GNU ABI
           which uses global registers $231 and up.

       -mzero-extend
       -mno-zero-extend
           When reading data from memory in sizes shorter than 64 bits, use (do not use)
           zero-extending load instructions by default, rather than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same sign as the
           divisor.  With the default, -mno-knuthdiv, the sign of the remainder follows
           the sign of the dividend.  Both methods are arithmetically valid, the latter
           being almost exclusively used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the assembly code can be
           used with the "PREFIX" assembly directive.

       -melf
           Generate an executable in the ELF format, rather than the default mmo format
           used by the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
           Use (do not use) the probable-branch instructions, when static branch
           prediction indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
           Generate (do not generate) code that uses base addresses.  Using a base address
           automatically generates a request (handled by the assembler and the linker) for
           a constant to be set up in a global register.  The register is used for one or
           more base address requests within the range 0 to 255 from the value held in the
           register.  The generally leads to short and fast code, but the number of
           different data items that can be addressed is limited.  This means that a
           program that uses lots of static data may require -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
           Force (do not force) generated code to have a single exit point in each
           function.

   MN10300 Options
       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
           Generate code to avoid bugs in the multiply instructions for the MN10300
           processors.  This is the default.

       -mno-mult-bug
           Do not generate code to avoid bugs in the multiply instructions for the MN10300
           processors.

       -mam33
           Generate code which uses features specific to the AM33 processor.

       -mno-am33
           Do not generate code which uses features specific to the AM33 processor.  This
           is the default.

       -mreturn-pointer-on-d0
           When generating a function which returns a pointer, return the pointer in both
           "a0" and "d0".  Otherwise, the pointer is returned only in a0, and attempts to
           call such functions without a prototype would result in errors.  Note that this
           option is on by default; use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       -mrelax
           Indicate to the linker that it should perform a relaxation optimization pass to
           shorten branches, calls and absolute memory addresses.  This option only has an
           effect when used on the command line for the final link step.

           This option makes symbolic debugging impossible.

   PDP-11 Options
       These options are defined for the PDP-11:

       -mfpu
           Use hardware FPP floating point.  This is the default.  (FIS floating point on
           the PDP-11/40 is not supported.)

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler syntax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.

       -mbcopy-builtin
           Use inline "movmemhi" patterns for copying memory.  This is the default.

       -mbcopy
           Do not use inline "movmemhi" patterns for copying memory.

       -mint16
       -mno-int32
           Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
           Use 32-bit "int".

       -mfloat64
       -mno-float32
           Use 64-bit "float".  This is the default.

       -mfloat32
       -mno-float64
           Use 32-bit "float".

       -mabshi
           Use "abshi2" pattern.  This is the default.

       -mno-abshi
           Do not use "abshi2" pattern.

       -mbranch-expensive
           Pretend that branches are expensive.  This is for experimenting with code
           generation only.

       -mbranch-cheap
           Do not pretend that branches are expensive.  This is the default.

       -msplit
           Generate code for a system with split I&D.

       -mno-split
           Generate code for a system without split I&D.  This is the default.

       -munix-asm
           Use Unix assembler syntax.  This is the default when configured for
           pdp11-*-bsd.

       -mdec-asm
           Use DEC assembler syntax.  This is the default when configured for any PDP-11
           target other than pdp11-*-bsd.

   picoChip Options
       These -m options are defined for picoChip implementations:

       -mae=ae_type
           Set the instruction set, register set, and instruction scheduling parameters
           for array element type ae_type.  Supported values for ae_type are ANY, MUL, and
           MAC.

           -mae=ANY selects a completely generic AE type.  Code generated with this option
           will run on any of the other AE types.  The code will not be as efficient as it
           would be if compiled for a specific AE type, and some types of operation (e.g.,
           multiplication) will not work properly on all types of AE.

           -mae=MUL selects a MUL AE type.  This is the most useful AE type for compiled
           code, and is the default.

           -mae=MAC selects a DSP-style MAC AE.  Code compiled with this option may suffer
           from poor performance of byte (char) manipulation, since the DSP AE does not
           provide hardware support for byte load/stores.

       -msymbol-as-address
           Enable the compiler to directly use a symbol name as an address in a load/store
           instruction, without first loading it into a register.  Typically, the use of
           this option will generate larger programs, which run faster than when the
           option isn't used.  However, the results vary from program to program, so it is
           left as a user option, rather than being permanently enabled.

       -mno-inefficient-warnings
           Disables warnings about the generation of inefficient code.  These warnings can
           be generated, for example, when compiling code which performs byte-level memory
           operations on the MAC AE type.  The MAC AE has no hardware support for byte-
           level memory operations, so all byte load/stores must be synthesized from word
           load/store operations.  This is inefficient and a warning will be generated
           indicating to the programmer that they should rewrite the code to avoid byte
           operations, or to target an AE type which has the necessary hardware support.
           This option enables the warning to be turned off.

   PowerPC Options
       These are listed under

   IBM RS/6000 and PowerPC Options
       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-powerpc
       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mmfpgpr
       -mno-mfpgpr
       -mhard-dfp
       -mno-hard-dfp
           GCC supports two related instruction set architectures for the RS/6000 and
           PowerPC.  The POWER instruction set are those instructions supported by the
           rios chip set used in the original RS/6000 systems and the PowerPC instruction
           set is the architecture of the Freescale MPC5xx, MPC6xx, MPC8xx
           microprocessors, and the IBM 4xx, 6xx, and follow-on microprocessors.

           Neither architecture is a subset of the other.  However there is a large common
           subset of instructions supported by both.  An MQ register is included in
           processors supporting the POWER architecture.

           You use these options to specify which instructions are available on the
           processor you are using.  The default value of these options is determined when
           configuring GCC.  Specifying the -mcpu=cpu_type overrides the specification of
           these options.  We recommend you use the -mcpu=cpu_type option rather than the
           options listed above.

           The -mpower option allows GCC to generate instructions that are found only in
           the POWER architecture and to use the MQ register.  Specifying -mpower2 implies
           -power and also allows GCC to generate instructions that are present in the
           POWER2 architecture but not the original POWER architecture.

           The -mpowerpc option allows GCC to generate instructions that are found only in
           the 32-bit subset of the PowerPC architecture.  Specifying -mpowerpc-gpopt
           implies -mpowerpc and also allows GCC to use the optional PowerPC architecture
           instructions in the General Purpose group, including floating-point square
           root.  Specifying -mpowerpc-gfxopt implies -mpowerpc and also allows GCC to use
           the optional PowerPC architecture instructions in the Graphics group, including
           floating-point select.

           The -mmfcrf option allows GCC to generate the move from condition register
           field instruction implemented on the POWER4 processor and other processors that
           support the PowerPC V2.01 architecture.  The -mpopcntb option allows GCC to
           generate the popcount and double precision FP reciprocal estimate instruction
           implemented on the POWER5 processor and other processors that support the
           PowerPC V2.02 architecture.  The -mpopcntd option allows GCC to generate the
           popcount instruction implemented on the POWER7 processor and other processors
           that support the PowerPC V2.06 architecture.  The -mfprnd option allows GCC to
           generate the FP round to integer instructions implemented on the POWER5+
           processor and other processors that support the PowerPC V2.03 architecture.
           The -mcmpb option allows GCC to generate the compare bytes instruction
           implemented on the POWER6 processor and other processors that support the
           PowerPC V2.05 architecture.  The -mmfpgpr option allows GCC to generate the FP
           move to/from general purpose register instructions implemented on the POWER6X
           processor and other processors that support the extended PowerPC V2.05
           architecture.  The -mhard-dfp option allows GCC to generate the decimal
           floating point instructions implemented on some POWER processors.

           The -mpowerpc64 option allows GCC to generate the additional 64-bit
           instructions that are found in the full PowerPC64 architecture and to treat
           GPRs as 64-bit, doubleword quantities.  GCC defaults to -mno-powerpc64.

           If you specify both -mno-power and -mno-powerpc, GCC will use only the
           instructions in the common subset of both architectures plus some special AIX
           common-mode calls, and will not use the MQ register.  Specifying both -mpower
           and -mpowerpc permits GCC to use any instruction from either architecture and
           to allow use of the MQ register; specify this for the Motorola MPC601.

       -mnew-mnemonics
       -mold-mnemonics
           Select which mnemonics to use in the generated assembler code.  With
           -mnew-mnemonics, GCC uses the assembler mnemonics defined for the PowerPC
           architecture.  With -mold-mnemonics it uses the assembler mnemonics defined for
           the POWER architecture.  Instructions defined in only one architecture have
           only one mnemonic; GCC uses that mnemonic irrespective of which of these
           options is specified.

           GCC defaults to the mnemonics appropriate for the architecture in use.
           Specifying -mcpu=cpu_type sometimes overrides the value of these option.
           Unless you are building a cross-compiler, you should normally not specify
           either -mnew-mnemonics or -mold-mnemonics, but should instead accept the
           default.

       -mcpu=cpu_type
           Set architecture type, register usage, choice of mnemonics, and instruction
           scheduling parameters for machine type cpu_type.  Supported values for cpu_type
           are 401, 403, 405, 405fp, 440, 440fp, 464, 464fp, 505, 601, 602, 603, 603e,
           604, 604e, 620, 630, 740, 7400, 7450, 750, 801, 821, 823, 860, 970, 8540,
           e300c2, e300c3, e500mc, ec603e, G3, G4, G5, power, power2, power3, power4,
           power5, power5+, power6, power6x, power7, common, powerpc, powerpc64, rios,
           rios1, rios2, rsc, and rs64.

           -mcpu=common selects a completely generic processor.  Code generated under this
           option will run on any POWER or PowerPC processor.  GCC will use only the
           instructions in the common subset of both architectures, and will not use the
           MQ register.  GCC assumes a generic processor model for scheduling purposes.

           -mcpu=power, -mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64 specify generic
           POWER, POWER2, pure 32-bit PowerPC (i.e., not MPC601), and 64-bit PowerPC
           architecture machine types, with an appropriate, generic processor model
           assumed for scheduling purposes.

           The other options specify a specific processor.  Code generated under those
           options will run best on that processor, and may not run at all on others.

           The -mcpu options automatically enable or disable the following options:

           -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mnew-mnemonics
           -mpopcntb -mpopcntd  -mpower  -mpower2  -mpowerpc64 -mpowerpc-gpopt
           -mpowerpc-gfxopt  -msingle-float -mdouble-float -msimple-fpu -mstring  -mmulhw
           -mdlmzb  -mmfpgpr -mvsx

           The particular options set for any particular CPU will vary between compiler
           versions, depending on what setting seems to produce optimal code for that CPU;
           it doesn't necessarily reflect the actual hardware's capabilities.  If you wish
           to set an individual option to a particular value, you may specify it after the
           -mcpu option, like -mcpu=970 -mno-altivec.

           On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled by
           the -mcpu option at present because AIX does not have full support for these
           options.  You may still enable or disable them individually if you're sure
           it'll work in your environment.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not
           set the architecture type, register usage, or choice of mnemonics, as
           -mcpu=cpu_type would.  The same values for cpu_type are used for -mtune as for
           -mcpu.  If both are specified, the code generated will use the architecture,
           registers, and mnemonics set by -mcpu, but the scheduling parameters set by
           -mtune.

       -mcmodel=small
           Generate PowerPC64 code for the small model: The TOC is limited to 64k.

       -mcmodel=medium
           Generate PowerPC64 code for the medium model: The TOC and other static data may
           be up to a total of 4G in size.

       -mcmodel=large
           Generate PowerPC64 code for the large model: The TOC may be up to 4G in size.
           Other data and code is only limited by the 64-bit address space.

       -mswdiv
       -mno-swdiv
           Generate code to compute division as reciprocal estimate and iterative
           refinement, creating opportunities for increased throughput.  This feature
           requires: optional PowerPC Graphics instruction set for single precision and
           FRE instruction for double precision, assuming divides cannot generate user-
           visible traps, and the domain values not include Infinities, denormals or zero
           denominator.

       -maltivec
       -mno-altivec
           Generate code that uses (does not use) AltiVec instructions, and also enable
           the use of built-in functions that allow more direct access to the AltiVec
           instruction set.  You may also need to set -mabi=altivec to adjust the current
           ABI with AltiVec ABI enhancements.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -mgen-cell-microcode
           Generate Cell microcode instructions

       -mwarn-cell-microcode
           Warning when a Cell microcode instruction is going to emitted.  An example of a
           Cell microcode instruction is a variable shift.

       -msecure-plt
           Generate code that allows ld and ld.so to build executables and shared
           libraries with non-exec .plt and .got sections.  This is a PowerPC 32-bit SYSV
           ABI option.

       -mbss-plt
           Generate code that uses a BSS .plt section that ld.so fills in, and requires
           .plt and .got sections that are both writable and executable.  This is a
           PowerPC 32-bit SYSV ABI option.

       -misel
       -mno-isel
           This switch enables or disables the generation of ISEL instructions.

       -misel=yes/no
           This switch has been deprecated.  Use -misel and -mno-isel instead.

       -mspe
       -mno-spe
           This switch enables or disables the generation of SPE simd instructions.

       -mpaired
       -mno-paired
           This switch enables or disables the generation of PAIRED simd instructions.

       -mspe=yes/no
           This option has been deprecated.  Use -mspe and -mno-spe instead.

       -mvsx
       -mno-vsx
           Generate code that uses (does not use) vector/scalar (VSX) instructions, and
           also enable the use of built-in functions that allow more direct access to the
           VSX instruction set.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
           This switch enables or disables the generation of floating point operations on
           the general purpose registers for architectures that support it.

           The argument yes or single enables the use of single-precision floating point
           operations.

           The argument double enables the use of single and double-precision floating
           point operations.

           The argument no disables floating point operations on the general purpose
           registers.

           This option is currently only available on the MPC854x.

       -m32
       -m64
           Generate code for 32-bit or 64-bit environments of Darwin and SVR4 targets
           (including GNU/Linux).  The 32-bit environment sets int, long and pointer to 32
           bits and generates code that runs on any PowerPC variant.  The 64-bit
           environment sets int to 32 bits and long and pointer to 64 bits, and generates
           code for PowerPC64, as for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
           Modify generation of the TOC (Table Of Contents), which is created for every
           executable file.  The -mfull-toc option is selected by default.  In that case,
           GCC will allocate at least one TOC entry for each unique non-automatic variable
           reference in your program.  GCC will also place floating-point constants in the
           TOC.  However, only 16,384 entries are available in the TOC.

           If you receive a linker error message that saying you have overflowed the
           available TOC space, you can reduce the amount of TOC space used with the
           -mno-fp-in-toc and -mno-sum-in-toc options.  -mno-fp-in-toc prevents GCC from
           putting floating-point constants in the TOC and -mno-sum-in-toc forces GCC to
           generate code to calculate the sum of an address and a constant at run-time
           instead of putting that sum into the TOC.  You may specify one or both of these
           options.  Each causes GCC to produce very slightly slower and larger code at
           the expense of conserving TOC space.

           If you still run out of space in the TOC even when you specify both of these
           options, specify -mminimal-toc instead.  This option causes GCC to make only
           one TOC entry for every file.  When you specify this option, GCC will produce
           code that is slower and larger but which uses extremely little TOC space.  You
           may wish to use this option only on files that contain less frequently executed
           code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit "long"
           type, and the infrastructure needed to support them.  Specifying -maix64
           implies -mpowerpc64 and -mpowerpc, while -maix32 disables the 64-bit ABI and
           implies -mno-powerpc64.  GCC defaults to -maix32.

       -mxl-compat
       -mno-xl-compat
           Produce code that conforms more closely to IBM XL compiler semantics when using
           AIX-compatible ABI.  Pass floating-point arguments to prototyped functions
           beyond the register save area (RSA) on the stack in addition to argument FPRs.
           Do not assume that most significant double in 128-bit long double value is
           properly rounded when comparing values and converting to double.  Use XL symbol
           names for long double support routines.

           The AIX calling convention was extended but not initially documented to handle
           an obscure K&R C case of calling a function that takes the address of its
           arguments with fewer arguments than declared.  IBM XL compilers access floating
           point arguments which do not fit in the RSA from the stack when a subroutine is
           compiled without optimization.  Because always storing floating-point arguments
           on the stack is inefficient and rarely needed, this option is not enabled by
           default and only is necessary when calling subroutines compiled by IBM XL
           compilers without optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an application written
           to use message passing with special startup code to enable the application to
           run.  The system must have PE installed in the standard location
           (/usr/lpp/ppe.poe/), or the specs file must be overridden with the -specs=
           option to specify the appropriate directory location.  The Parallel Environment
           does not support threads, so the -mpe option and the -pthread option are
           incompatible.

       -malign-natural
       -malign-power
           On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural
           overrides the ABI-defined alignment of larger types, such as floating-point
           doubles, on their natural size-based boundary.  The option -malign-power
           instructs GCC to follow the ABI-specified alignment rules.  GCC defaults to the
           standard alignment defined in the ABI.

           On 64-bit Darwin, natural alignment is the default, and -malign-power is not
           supported.

       -msoft-float
       -mhard-float
           Generate code that does not use (uses) the floating-point register set.
           Software floating point emulation is provided if you use the -msoft-float
           option, and pass the option to GCC when linking.

       -msingle-float
       -mdouble-float
           Generate code for single or double-precision floating point operations.
           -mdouble-float implies -msingle-float.

       -msimple-fpu
           Do not generate sqrt and div instructions for hardware floating point unit.

       -mfpu
           Specify type of floating point unit.  Valid values are sp_lite (equivalent to
           -msingle-float -msimple-fpu), dp_lite (equivalent to -mdouble-float
           -msimple-fpu), sp_full (equivalent to -msingle-float), and dp_full (equivalent
           to -mdouble-float).

       -mxilinx-fpu
           Perform optimizations for floating point unit on Xilinx PPC 405/440.

       -mmultiple
       -mno-multiple
           Generate code that uses (does not use) the load multiple word instructions and
           the store multiple word instructions.  These instructions are generated by
           default on POWER systems, and not generated on PowerPC systems.  Do not use
           -mmultiple on little endian PowerPC systems, since those instructions do not
           work when the processor is in little endian mode.  The exceptions are PPC740
           and PPC750 which permit the instructions usage in little endian mode.

       -mstring
       -mno-string
           Generate code that uses (does not use) the load string instructions and the
           store string word instructions to save multiple registers and do small block
           moves.  These instructions are generated by default on POWER systems, and not
           generated on PowerPC systems.  Do not use -mstring on little endian PowerPC
           systems, since those instructions do not work when the processor is in little
           endian mode.  The exceptions are PPC740 and PPC750 which permit the
           instructions usage in little endian mode.

       -mupdate
       -mno-update
           Generate code that uses (does not use) the load or store instructions that
           update the base register to the address of the calculated memory location.
           These instructions are generated by default.  If you use -mno-update, there is
           a small window between the time that the stack pointer is updated and the
           address of the previous frame is stored, which means code that walks the stack
           frame across interrupts or signals may get corrupted data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
           Generate code that tries to avoid (not avoid) the use of indexed load or store
           instructions. These instructions can incur a performance penalty on Power6
           processors in certain situations, such as when stepping through large arrays
           that cross a 16M boundary.  This option is enabled by default when targetting
           Power6 and disabled otherwise.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating point multiply and
           accumulate instructions.  These instructions are generated by default if
           hardware floating is used.

       -mmulhw
       -mno-mulhw
           Generate code that uses (does not use) the half-word multiply and multiply-
           accumulate instructions on the IBM 405, 440 and 464 processors.  These
           instructions are generated by default when targetting those processors.

       -mdlmzb
       -mno-dlmzb
           Generate code that uses (does not use) the string-search dlmzb instruction on
           the IBM 405, 440 and 464 processors.  This instruction is generated by default
           when targetting those processors.

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force structures and
           unions that contain bit-fields to be aligned to the base type of the bit-field.

           For example, by default a structure containing nothing but 8 "unsigned" bit-
           fields of length 1 would be aligned to a 4 byte boundary and have a size of 4
           bytes.  By using -mno-bit-align, the structure would be aligned to a 1 byte
           boundary and be one byte in size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume that unaligned
           memory references will be handled by the system.

       -mrelocatable
       -mno-relocatable
           On embedded PowerPC systems generate code that allows (does not allow) the
           program to be relocated to a different address at runtime.  If you use
           -mrelocatable on any module, all objects linked together must be compiled with
           -mrelocatable or -mrelocatable-lib.

       -mrelocatable-lib
       -mno-relocatable-lib
           On embedded PowerPC systems generate code that allows (does not allow) the
           program to be relocated to a different address at runtime.  Modules compiled
           with -mrelocatable-lib can be linked with either modules compiled without
           -mrelocatable and -mrelocatable-lib or with modules compiled with the
           -mrelocatable options.

       -mno-toc
       -mtoc
           On System V.4 and embedded PowerPC systems do not (do) assume that register 2
           contains a pointer to a global area pointing to the addresses used in the
           program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in
           little endian mode.  The -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in
           big endian mode.  The -mbig-endian option is the same as -mbig.

       -mdynamic-no-pic
           On Darwin and Mac OS X systems, compile code so that it is not relocatable, but
           that its external references are relocatable.  The resulting code is suitable
           for applications, but not shared libraries.

       -mprioritize-restricted-insns=priority
           This option controls the priority that is assigned to dispatch-slot restricted
           instructions during the second scheduling pass.  The argument priority takes
           the value 0/1/2 to assign no/highest/second-highest priority to dispatch slot
           restricted instructions.

       -msched-costly-dep=dependence_type
           This option controls which dependences are considered costly by the target
           during instruction scheduling.  The argument dependence_type takes one of the
           following values: no: no dependence is costly, all: all dependences are costly,
           true_store_to_load: a true dependence from store to load is costly,
           store_to_load: any dependence from store to load is costly, number: any
           dependence which latency >= number is costly.

       -minsert-sched-nops=scheme
           This option controls which nop insertion scheme will be used during the second
           scheduling pass.  The argument scheme takes one of the following values: no:
           Don't insert nops.  pad: Pad with nops any dispatch group which has vacant
           issue slots, according to the scheduler's grouping.  regroup_exact: Insert nops
           to force costly dependent insns into separate groups.  Insert exactly as many
           nops as needed to force an insn to a new group, according to the estimated
           processor grouping.  number: Insert nops to force costly dependent insns into
           separate groups.  Insert number nops to force an insn to a new group.

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using calling
           conventions that adheres to the March 1995 draft of the System V Application
           Binary Interface, PowerPC processor supplement.  This is the default unless you
           configured GCC using powerpc-*-eabiaix.

       -mcall-sysv-eabi
           Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
           Specify both -mcall-sysv and -mno-eabi options.

       -mcall-solaris
           On System V.4 and embedded PowerPC systems compile code for the Solaris
           operating system.

       -mcall-linux
           On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU
           system.

       -mcall-gnu
           On System V.4 and embedded PowerPC systems compile code for the Hurd-based GNU
           system.

       -mcall-netbsd
           On System V.4 and embedded PowerPC systems compile code for the NetBSD
           operating system.

       -maix-struct-return
           Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers (as specified by the SVR4
           ABI).

       -mabi=abi-type
           Extend the current ABI with a particular extension, or remove such extension.
           Valid values are altivec, no-altivec, spe, no-spe, ibmlongdouble,
           ieeelongdouble.

       -mabi=spe
           Extend the current ABI with SPE ABI extensions.  This does not change the
           default ABI, instead it adds the SPE ABI extensions to the current ABI.

       -mabi=no-spe
           Disable Booke SPE ABI extensions for the current ABI.

       -mabi=ibmlongdouble
           Change the current ABI to use IBM extended precision long double.  This is a
           PowerPC 32-bit SYSV ABI option.

       -mabi=ieeelongdouble
           Change the current ABI to use IEEE extended precision long double.  This is a
           PowerPC 32-bit Linux ABI option.

       -mprototype
       -mno-prototype
           On System V.4 and embedded PowerPC systems assume that all calls to variable
           argument functions are properly prototyped.  Otherwise, the compiler must
           insert an instruction before every non prototyped call to set or clear bit 6 of
           the condition code register (CR) to indicate whether floating point values were
           passed in the floating point registers in case the function takes a variable
           arguments.  With -mprototype, only calls to prototyped variable argument
           functions will set or clear the bit.

       -msim
           On embedded PowerPC systems, assume that the startup module is called
           sim-crt0.o and that the standard C libraries are libsim.a and libc.a.  This is
           the default for powerpc-*-eabisim configurations.

       -mmvme
           On embedded PowerPC systems, assume that the startup module is called crt0.o
           and the standard C libraries are libmvme.a and libc.a.

       -mads
           On embedded PowerPC systems, assume that the startup module is called crt0.o
           and the standard C libraries are libads.a and libc.a.

       -myellowknife
           On embedded PowerPC systems, assume that the startup module is called crt0.o
           and the standard C libraries are libyk.a and libc.a.

       -mvxworks
           On System V.4 and embedded PowerPC systems, specify that you are compiling for
           a VxWorks system.

       -memb
           On embedded PowerPC systems, set the PPC_EMB bit in the ELF flags header to
           indicate that eabi extended relocations are used.

       -meabi
       -mno-eabi
           On System V.4 and embedded PowerPC systems do (do not) adhere to the Embedded
           Applications Binary Interface (eabi) which is a set of modifications to the
           System V.4 specifications.  Selecting -meabi means that the stack is aligned to
           an 8 byte boundary, a function "__eabi" is called to from "main" to set up the
           eabi environment, and the -msdata option can use both "r2" and "r13" to point
           to two separate small data areas.  Selecting -mno-eabi means that the stack is
           aligned to a 16 byte boundary, do not call an initialization function from
           "main", and the -msdata option will only use "r13" to point to a single small
           data area.  The -meabi option is on by default if you configured GCC using one
           of the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put small initialized "const"
           global and static data in the .sdata2 section, which is pointed to by register
           "r2".  Put small initialized non-"const" global and static data in the .sdata
           section, which is pointed to by register "r13".  Put small uninitialized global
           and static data in the .sbss section, which is adjacent to the .sdata section.
           The -msdata=eabi option is incompatible with the -mrelocatable option.  The
           -msdata=eabi option also sets the -memb option.

       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small global and static data in
           the .sdata section, which is pointed to by register "r13".  Put small
           uninitialized global and static data in the .sbss section, which is adjacent to
           the .sdata section.  The -msdata=sysv option is incompatible with the
           -mrelocatable option.

       -msdata=default
       -msdata
           On System V.4 and embedded PowerPC systems, if -meabi is used, compile code the
           same as -msdata=eabi, otherwise compile code the same as -msdata=sysv.

       -msdata=data
           On System V.4 and embedded PowerPC systems, put small global data in the .sdata
           section.  Put small uninitialized global data in the .sbss section.  Do not use
           register "r13" to address small data however.  This is the default behavior
           unless other -msdata options are used.

       -msdata=none
       -mno-sdata
           On embedded PowerPC systems, put all initialized global and static data in the
           .data section, and all uninitialized data in the .bss section.

       -G num
           On embedded PowerPC systems, put global and static items less than or equal to
           num bytes into the small data or bss sections instead of the normal data or bss
           section.  By default, num is 8.  The -G num switch is also passed to the
           linker.  All modules should be compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems do (do not) emit register names in
           the assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
           By default assume that all calls are far away so that a longer more expensive
           calling sequence is required.  This is required for calls further than 32
           megabytes (33,554,432 bytes) from the current location.  A short call will be
           generated if the compiler knows the call cannot be that far away.  This setting
           can be overridden by the "shortcall" function attribute, or by "#pragma
           longcall(0)".

           Some linkers are capable of detecting out-of-range calls and generating glue
           code on the fly.  On these systems, long calls are unnecessary and generate
           slower code.  As of this writing, the AIX linker can do this, as can the GNU
           linker for PowerPC/64.  It is planned to add this feature to the GNU linker for
           32-bit PowerPC systems as well.

           On Darwin/PPC systems, "#pragma longcall" will generate "jbsr callee, L42",
           plus a "branch island" (glue code).  The two target addresses represent the
           callee and the "branch island".  The Darwin/PPC linker will prefer the first
           address and generate a "bl callee" if the PPC "bl" instruction will reach the
           callee directly; otherwise, the linker will generate "bl L42" to call the
           "branch island".  The "branch island" is appended to the body of the calling
           function; it computes the full 32-bit address of the callee and jumps to it.

           On Mach-O (Darwin) systems, this option directs the compiler emit to the glue
           for every direct call, and the Darwin linker decides whether to use or discard
           it.

           In the future, we may cause GCC to ignore all longcall specifications when the
           linker is known to generate glue.

       -pthread
           Adds support for multithreading with the pthreads library.  This option sets
           flags for both the preprocessor and linker.

   S/390 and zSeries Options
       These are the -m options defined for the S/390 and zSeries architecture.

       -mhard-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions and registers for
           floating-point operations.  When -msoft-float is specified, functions in
           libgcc.a will be used to perform floating-point operations.  When -mhard-float
           is specified, the compiler generates IEEE floating-point instructions.  This is
           the default.

       -mhard-dfp
       -mno-hard-dfp
           Use (do not use) the hardware decimal-floating-point instructions for decimal-
           floating-point operations.  When -mno-hard-dfp is specified, functions in
           libgcc.a will be used to perform decimal-floating-point operations.  When
           -mhard-dfp is specified, the compiler generates decimal-floating-point hardware
           instructions.  This is the default for -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
           These switches control the size of "long double" type. A size of 64bit makes
           the "long double" type equivalent to the "double" type. This is the default.

       -mbackchain
       -mno-backchain
           Store (do not store) the address of the caller's frame as backchain pointer
           into the callee's stack frame.  A backchain may be needed to allow debugging
           using tools that do not understand DWARF-2 call frame information.  When
           -mno-packed-stack is in effect, the backchain pointer is stored at the bottom
           of the stack frame; when -mpacked-stack is in effect, the backchain is placed
           into the topmost word of the 96/160 byte register save area.

           In general, code compiled with -mbackchain is call-compatible with code
           compiled with -mmo-backchain; however, use of the backchain for debugging
           purposes usually requires that the whole binary is built with -mbackchain.
           Note that the combination of -mbackchain, -mpacked-stack and -mhard-float is
           not supported.  In order to build a linux kernel use -msoft-float.

           The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
           Use (do not use) the packed stack layout.  When -mno-packed-stack is specified,
           the compiler uses the all fields of the 96/160 byte register save area only for
           their default purpose; unused fields still take up stack space.  When
           -mpacked-stack is specified, register save slots are densely packed at the top
           of the register save area; unused space is reused for other purposes, allowing
           for more efficient use of the available stack space.  However, when -mbackchain
           is also in effect, the topmost word of the save area is always used to store
           the backchain, and the return address register is always saved two words below
           the backchain.

           As long as the stack frame backchain is not used, code generated with
           -mpacked-stack is call-compatible with code generated with -mno-packed-stack.
           Note that some non-FSF releases of GCC 2.95 for S/390 or zSeries generated code
           that uses the stack frame backchain at run time, not just for debugging
           purposes.  Such code is not call-compatible with code compiled with
           -mpacked-stack.  Also, note that the combination of -mbackchain, -mpacked-stack
           and -mhard-float is not supported.  In order to build a linux kernel use
           -msoft-float.

           The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
           Generate (or do not generate) code using the "bras" instruction to do
           subroutine calls.  This only works reliably if the total executable size does
           not exceed 64k.  The default is to use the "basr" instruction instead, which
           does not have this limitation.

       -m64
       -m31
           When -m31 is specified, generate code compliant to the GNU/Linux for S/390 ABI.
           When -m64 is specified, generate code compliant to the GNU/Linux for zSeries
           ABI.  This allows GCC in particular to generate 64-bit instructions.  For the
           s390 targets, the default is -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
           When -mzarch is specified, generate code using the instructions available on
           z/Architecture.  When -mesa is specified, generate code using the instructions
           available on ESA/390.  Note that -mesa is not possible with -m64.  When
           generating code compliant to the GNU/Linux for S/390 ABI, the default is -mesa.
           When generating code compliant to the GNU/Linux for zSeries ABI, the default is
           -mzarch.

       -mmvcle
       -mno-mvcle
           Generate (or do not generate) code using the "mvcle" instruction to perform
           block moves.  When -mno-mvcle is specified, use a "mvc" loop instead.  This is
           the default unless optimizing for size.

       -mdebug
       -mno-debug
           Print (or do not print) additional debug information when compiling.  The
           default is to not print debug information.

       -march=cpu-type
           Generate code that will run on cpu-type, which is the name of a system
           representing a certain processor type.  Possible values for cpu-type are g5,
           g6, z900, z990, z9-109, z9-ec and z10.  When generating code using the
           instructions available on z/Architecture, the default is -march=z900.
           Otherwise, the default is -march=g5.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the
           ABI and the set of available instructions.  The list of cpu-type values is the
           same as for -march.  The default is the value used for -march.

       -mtpf-trace
       -mno-tpf-trace
           Generate code that adds (does not add) in TPF OS specific branches to trace
           routines in the operating system.  This option is off by default, even when
           compiling for the TPF OS.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating point multiply and
           accumulate instructions.  These instructions are generated by default if
           hardware floating point is used.

       -mwarn-framesize=framesize
           Emit a warning if the current function exceeds the given frame size.  Because
           this is a compile time check it doesn't need to be a real problem when the
           program runs.  It is intended to identify functions which most probably cause a
           stack overflow.  It is useful to be used in an environment with limited stack
           size e.g. the linux kernel.

       -mwarn-dynamicstack
           Emit a warning if the function calls alloca or uses dynamically sized arrays.
           This is generally a bad idea with a limited stack size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
           If these options are provided the s390 back end emits additional instructions
           in the function prologue which trigger a trap if the stack size is stack-guard
           bytes above the stack-size (remember that the stack on s390 grows downward).
           If the stack-guard option is omitted the smallest power of 2 larger than the
           frame size of the compiled function is chosen.  These options are intended to
           be used to help debugging stack overflow problems.  The additionally emitted
           code causes only little overhead and hence can also be used in production like
           systems without greater performance degradation.  The given values have to be
           exact powers of 2 and stack-size has to be greater than stack-guard without
           exceeding 64k.  In order to be efficient the extra code makes the assumption
           that the stack starts at an address aligned to the value given by stack-size.
           The stack-guard option can only be used in conjunction with stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
           If the hotpatch option is enabled, a "hot-patching" function prologue is
           generated for all functions in the compilation unit.  The funtion label is
           prepended with the given number of two-byte NOP instructions (pre-halfwords,
           maximum 1000000).  After the label, 2 * post-halfwords bytes are appended,
           using the largest NOP like instructions the architecture allows (maximum
           1000000).

           If both arguments are zero, hotpatching is disabled.

           This option can be overridden for individual functions with the "hotpatch"
           attribute.

   Score Options
       These options are defined for Score implementations:

       -meb
           Compile code for big endian mode.  This is the default.

       -mel
           Compile code for little endian mode.

       -mnhwloop
           Disable generate bcnz instruction.

       -muls
           Enable generate unaligned load and store instruction.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mscore5
           Specify the SCORE5 as the target architecture.

       -mscore5u
           Specify the SCORE5U of the target architecture.

       -mscore7
           Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
           Specify the SCORE7D as the target architecture.

   SH Options
       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
           Generate code for the SH2e.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

       -m4-nofpu
           Generate code for the SH4 without a floating-point unit.

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only supports single-
           precision arithmetic.

       -m4-single
           Generate code for the SH4 assuming the floating-point unit is in single-
           precision mode by default.

       -m4 Generate code for the SH4.

       -m4a-nofpu
           Generate code for the SH4al-dsp, or for a SH4a in such a way that the floating-
           point unit is not used.

       -m4a-single-only
           Generate code for the SH4a, in such a way that no double-precision floating
           point operations are used.

       -m4a-single
           Generate code for the SH4a assuming the floating-point unit is in single-
           precision mode by default.

       -m4a
           Generate code for the SH4a.

       -m4al
           Same as -m4a-nofpu, except that it implicitly passes -dsp to the assembler.
           GCC doesn't generate any DSP instructions at the moment.

       -mb Compile code for the processor in big endian mode.

       -ml Compile code for the processor in little endian mode.

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this changes the calling
           conventions, and thus some functions from the standard C library will not work
           unless you recompile it first with -mdalign.

       -mrelax
           Shorten some address references at link time, when possible; uses the linker
           option -relax.

       -mbigtable
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       -mbitops
           Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
           Enable the use of the instruction "fmovd".

       -mhitachi
           Comply with the calling conventions defined by Renesas.

       -mrenesas
           Comply with the calling conventions defined by Renesas.

       -mno-renesas
           Comply with the calling conventions defined for GCC before the Renesas
           conventions were available.  This option is the default for all targets of the
           SH toolchain except for sh-symbianelf.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mhitachi is given.

       -mieee
           Increase IEEE-compliance of floating-point code.  At the moment, this is
           equivalent to -fno-finite-math-only.  When generating 16 bit SH opcodes,
           getting IEEE-conforming results for comparisons of NANs / infinities incurs
           extra overhead in every floating point comparison, therefore the default is set
           to -ffinite-math-only.

       -minline-ic_invalidate
           Inline code to invalidate instruction cache entries after setting up nested
           function trampolines.  This option has no effect if -musermode is in effect and
           the selected code generation option (e.g. -m4) does not allow the use of the
           icbi instruction.  If the selected code generation option does not allow the
           use of the icbi instruction, and -musermode is not in effect, the inlined code
           will manipulate the instruction cache address array directly with an
           associative write.  This not only requires privileged mode, but it will also
           fail if the cache line had been mapped via the TLB and has become unmapped.

       -misize
           Dump instruction size and location in the assembly code.

       -mpadstruct
           This option is deprecated.  It pads structures to multiple of 4 bytes, which is
           incompatible with the SH ABI.

       -mspace
           Optimize for space instead of speed.  Implied by -Os.

       -mprefergot
           When generating position-independent code, emit function calls using the Global
           Offset Table instead of the Procedure Linkage Table.

       -musermode
           Don't generate privileged mode only code; implies -mno-inline-ic_invalidate if
           the inlined code would not work in user mode.  This is the default when the
           target is "sh-*-linux*".

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set the division strategy to use for SHmedia code.  strategy must be one of:
           call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call, inv:call2, inv:fp .
           "fp" performs the operation in floating point.  This has a very high latency,
           but needs only a few instructions, so it might be a good choice if your code
           has enough easily exploitable ILP to allow the compiler to schedule the
           floating point instructions together with other instructions.  Division by zero
           causes a floating point exception.  "inv" uses integer operations to calculate
           the inverse of the divisor, and then multiplies the dividend with the inverse.
           This strategy allows cse and hoisting of the inverse calculation.  Division by
           zero calculates an unspecified result, but does not trap.  "inv:minlat" is a
           variant of "inv" where if no cse / hoisting opportunities have been found, or
           if the entire operation has been hoisted to the same place, the last stages of
           the inverse calculation are intertwined with the final multiply to reduce the
           overall latency, at the expense of using a few more instructions, and thus
           offering fewer scheduling opportunities with other code.  "call" calls a
           library function that usually implements the inv:minlat strategy.  This gives
           high code density for m5-*media-nofpu compilations.  "call2" uses a different
           entry point of the same library function, where it assumes that a pointer to a
           lookup table has already been set up, which exposes the pointer load to cse /
           code hoisting optimizations.  "inv:call", "inv:call2" and "inv:fp" all use the
           "inv" algorithm for initial code generation, but if the code stays unoptimized,
           revert to the "call", "call2", or "fp" strategies, respectively.  Note that the
           potentially-trapping side effect of division by zero is carried by a separate
           instruction, so it is possible that all the integer instructions are hoisted
           out, but the marker for the side effect stays where it is.  A recombination to
           fp operations or a call is not possible in that case.  "inv20u" and "inv20l"
           are variants of the "inv:minlat" strategy.  In the case that the inverse
           calculation was nor separated from the multiply, they speed up division where
           the dividend fits into 20 bits (plus sign where applicable), by inserting a
           test to skip a number of operations in this case; this test slows down the case
           of larger dividends.  inv20u assumes the case of a such a small dividend to be
           unlikely, and inv20l assumes it to be likely.

       -mdivsi3_libfunc=name
           Set the name of the library function used for 32 bit signed division to name.
           This only affect the name used in the call and inv:call division strategies,
           and the compiler will still expect the same sets of input/output/clobbered
           registers as if this option was not present.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed
           register is one that the register allocator can not use.  This is useful when
           compiling kernel code.  A register range is specified as two registers
           separated by a dash.  Multiple register ranges can be specified separated by a
           comma.

       -madjust-unroll
           Throttle unrolling to avoid thrashing target registers.  This option only has
           an effect if the gcc code base supports the TARGET_ADJUST_UNROLL_MAX target
           hook.

       -mindexed-addressing
           Enable the use of the indexed addressing mode for SHmedia32/SHcompact.  This is
           only safe if the hardware and/or OS implement 32 bit wrap-around semantics for
           the indexed addressing mode.  The architecture allows the implementation of
           processors with 64 bit MMU, which the OS could use to get 32 bit addressing,
           but since no current hardware implementation supports this or any other way to
           make the indexed addressing mode safe to use in the 32 bit ABI, the default is
           -mno-indexed-addressing.

       -mgettrcost=number
           Set the cost assumed for the gettr instruction to number.  The default is 2 if
           -mpt-fixed is in effect, 100 otherwise.

       -mpt-fixed
           Assume pt* instructions won't trap.  This will generally generate better
           scheduled code, but is unsafe on current hardware.  The current architecture
           definition says that ptabs and ptrel trap when the target anded with 3 is 3.
           This has the unintentional effect of making it unsafe to schedule ptabs / ptrel
           before a branch, or hoist it out of a loop.  For example, __do_global_ctors, a
           part of libgcc that runs constructors at program startup, calls functions in a
           list which is delimited by -1.  With the -mpt-fixed option, the ptabs will be
           done before testing against -1.  That means that all the constructors will be
           run a bit quicker, but when the loop comes to the end of the list, the program
           crashes because ptabs loads -1 into a target register.  Since this option is
           unsafe for any hardware implementing the current architecture specification,
           the default is -mno-pt-fixed.  Unless the user specifies a specific cost with
           -mgettrcost, -mno-pt-fixed also implies -mgettrcost=100; this deters register
           allocation using target registers for storing ordinary integers.

       -minvalid-symbols
           Assume symbols might be invalid.  Ordinary function symbols generated by the
           compiler will always be valid to load with movi/shori/ptabs or
           movi/shori/ptrel, but with assembler and/or linker tricks it is possible to
           generate symbols that will cause ptabs / ptrel to trap.  This option is only
           meaningful when -mno-pt-fixed is in effect.  It will then prevent cross-basic-
           block cse, hoisting and most scheduling of symbol loads.  The default is
           -mno-invalid-symbols.

   SPARC Options
       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
           Specify -mapp-regs to generate output using the global registers 2 through 4,
           which the SPARC SVR4 ABI reserves for applications.  This is the default.

           To be fully SVR4 ABI compliant at the cost of some performance loss, specify
           -mno-app-regs.  You should compile libraries and system software with this
           option.

       -mfpu
       -mhard-float
           Generate output containing floating point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate output containing library calls for floating point.  Warning: the
           requisite libraries are not available for all SPARC targets.  Normally the
           facilities of the machine's usual C compiler are used, but this cannot be done
           directly in cross-compilation.  You must make your own arrangements to provide
           suitable library functions for cross-compilation.  The embedded targets
           sparc-*-aout and sparclite-*-* do provide software floating point support.

           -msoft-float changes the calling convention in the output file; therefore, it
           is only useful if you compile all of a program with this option.  In
           particular, you need to compile libgcc.a, the library that comes with GCC, with
           -msoft-float in order for this to work.

       -mhard-quad-float
           Generate output containing quad-word (long double) floating point instructions.

       -msoft-quad-float
           Generate output containing library calls for quad-word (long double) floating
           point instructions.  The functions called are those specified in the SPARC ABI.
           This is the default.

           As of this writing, there are no SPARC implementations that have hardware
           support for the quad-word floating point instructions.  They all invoke a trap
           handler for one of these instructions, and then the trap handler emulates the
           effect of the instruction.  Because of the trap handler overhead, this is much
           slower than calling the ABI library routines.  Thus the -msoft-quad-float
           option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
           Assume that doubles have 8 byte alignment.  This is the default.

           With -munaligned-doubles, GCC assumes that doubles have 8 byte alignment only
           if they are contained in another type, or if they have an absolute address.
           Otherwise, it assumes they have 4 byte alignment.  Specifying this option
           avoids some rare compatibility problems with code generated by other compilers.
           It is not the default because it results in a performance loss, especially for
           floating point code.

       -mno-faster-structs
       -mfaster-structs
           With -mfaster-structs, the compiler assumes that structures should have 8 byte
           alignment.  This enables the use of pairs of "ldd" and "std" instructions for
           copies in structure assignment, in place of twice as many "ld" and "st" pairs.
           However, the use of this changed alignment directly violates the SPARC ABI.
           Thus, it's intended only for use on targets where the developer acknowledges
           that their resulting code will not be directly in line with the rules of the
           ABI.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the compiler to not pass -z
           text to the linker when linking a shared object.  Using this option, you can
           link position-dependent code into a shared object.

           -mimpure-text suppresses the "relocations remain against allocatable but non-
           writable sections" linker error message.  However, the necessary relocations
           will trigger copy-on-write, and the shared object is not actually shared across
           processes.  Instead of using -mimpure-text, you should compile all source code
           with -fpic or -fPIC.

           This option is only available on SunOS and Solaris.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters
           for machine type cpu_type.  Supported values for cpu_type are v7, cypress, v8,
           supersparc, sparclite, f930, f934, hypersparc, sparclite86x, sparclet, tsc701,
           v9, ultrasparc, ultrasparc3, niagara and niagara2.

           Default instruction scheduling parameters are used for values that select an
           architecture and not an implementation.  These are v7, v8, sparclite, sparclet,
           v9.

           Here is a list of each supported architecture and their supported
           implementations.

                       v7:             cypress
                       v8:             supersparc, hypersparc
                       sparclite:      f930, f934, sparclite86x
                       sparclet:       tsc701
                       v9:             ultrasparc, ultrasparc3, niagara, niagara2

           By default (unless configured otherwise), GCC generates code for the V7 variant
           of the SPARC architecture.  With -mcpu=cypress, the compiler additionally
           optimizes it for the Cypress CY7C602 chip, as used in the
           SPARCStation/SPARCServer 3xx series.  This is also appropriate for the older
           SPARCStation 1, 2, IPX etc.

           With -mcpu=v8, GCC generates code for the V8 variant of the SPARC architecture.
           The only difference from V7 code is that the compiler emits the integer
           multiply and integer divide instructions which exist in SPARC-V8 but not in
           SPARC-V7.  With -mcpu=supersparc, the compiler additionally optimizes it for
           the SuperSPARC chip, as used in the SPARCStation 10, 1000 and 2000 series.

           With -mcpu=sparclite, GCC generates code for the SPARClite variant of the SPARC
           architecture.  This adds the integer multiply, integer divide step and scan
           ("ffs") instructions which exist in SPARClite but not in SPARC-V7.  With
           -mcpu=f930, the compiler additionally optimizes it for the Fujitsu MB86930
           chip, which is the original SPARClite, with no FPU.  With -mcpu=f934, the
           compiler additionally optimizes it for the Fujitsu MB86934 chip, which is the
           more recent SPARClite with FPU.

           With -mcpu=sparclet, GCC generates code for the SPARClet variant of the SPARC
           architecture.  This adds the integer multiply, multiply/accumulate, integer
           divide step and scan ("ffs") instructions which exist in SPARClet but not in
           SPARC-V7.  With -mcpu=tsc701, the compiler additionally optimizes it for the
           TEMIC SPARClet chip.

           With -mcpu=v9, GCC generates code for the V9 variant of the SPARC architecture.
           This adds 64-bit integer and floating-point move instructions, 3 additional
           floating-point condition code registers and conditional move instructions.
           With -mcpu=ultrasparc, the compiler additionally optimizes it for the Sun
           UltraSPARC I/II/IIi chips.  With -mcpu=ultrasparc3, the compiler additionally
           optimizes it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips.  With
           -mcpu=niagara, the compiler additionally optimizes it for Sun UltraSPARC T1
           chips.  With -mcpu=niagara2, the compiler additionally optimizes it for Sun
           UltraSPARC T2 chips.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not
           set the instruction set or register set that the option -mcpu=cpu_type would.

           The same values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the
           only useful values are those that select a particular cpu implementation.
           Those are cypress, supersparc, hypersparc, f930, f934, sparclite86x, tsc701,
           ultrasparc, ultrasparc3, niagara, and niagara2.

       -mv8plus
       -mno-v8plus
           With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The difference from
           the V8 ABI is that the global and out registers are considered 64-bit wide.
           This is enabled by default on Solaris in 32-bit mode for all SPARC-V9
           processors.

       -mvis
       -mno-vis
           With -mvis, GCC generates code that takes advantage of the UltraSPARC Visual
           Instruction Set extensions.  The default is -mno-vis.

       These -m options are supported in addition to the above on SPARC-V9 processors in
       64-bit environments:

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  It is only
           available for a few configurations and most notably not on Solaris and Linux.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets
           int, long and pointer to 32 bits.  The 64-bit environment sets int to 32 bits
           and long and pointer to 64 bits.

       -mcmodel=medlow
           Generate code for the Medium/Low code model: 64-bit addresses, programs must be
           linked in the low 32 bits of memory.  Programs can be statically or dynamically
           linked.

       -mcmodel=medmid
           Generate code for the Medium/Middle code model: 64-bit addresses, programs must
           be linked in the low 44 bits of memory, the text and data segments must be less
           than 2GB in size and the data segment must be located within 2GB of the text
           segment.

       -mcmodel=medany
           Generate code for the Medium/Anywhere code model: 64-bit addresses, programs
           may be linked anywhere in memory, the text and data segments must be less than
           2GB in size and the data segment must be located within 2GB of the text
           segment.

       -mcmodel=embmedany
           Generate code for the Medium/Anywhere code model for embedded systems: 64-bit
           addresses, the text and data segments must be less than 2GB in size, both
           starting anywhere in memory (determined at link time).  The global register %g4
           points to the base of the data segment.  Programs are statically linked and PIC
           is not supported.

       -mstack-bias
       -mno-stack-bias
           With -mstack-bias, GCC assumes that the stack pointer, and frame pointer if
           present, are offset by -2047 which must be added back when making stack frame
           references.  This is the default in 64-bit mode.  Otherwise, assume no such
           offset is present.

       These switches are supported in addition to the above on Solaris:

       -threads
           Add support for multithreading using the Solaris threads library.  This option
           sets flags for both the preprocessor and linker.  This option does not affect
           the thread safety of object code produced by the compiler or that of libraries
           supplied with it.

       -pthreads
           Add support for multithreading using the POSIX threads library.  This option
           sets flags for both the preprocessor and linker.  This option does not affect
           the thread safety of object code produced  by the compiler or that of libraries
           supplied with it.

       -pthread
           This is a synonym for -pthreads.

   SPU Options
       These -m options are supported on the SPU:

       -mwarn-reloc
       -merror-reloc
           The loader for SPU does not handle dynamic relocations.  By default, GCC will
           give an error when it generates code that requires a dynamic relocation.
           -mno-error-reloc disables the error, -mwarn-reloc will generate a warning
           instead.

       -msafe-dma
       -munsafe-dma
           Instructions which initiate or test completion of DMA must not be reordered
           with respect to loads and stores of the memory which is being accessed.  Users
           typically address this problem using the volatile keyword, but that can lead to
           inefficient code in places where the memory is known to not change.  Rather
           than mark the memory as volatile we treat the DMA instructions as potentially
           effecting all memory.  With -munsafe-dma users must use the volatile keyword to
           protect memory accesses.

       -mbranch-hints
           By default, GCC will generate a branch hint instruction to avoid pipeline
           stalls for always taken or probably taken branches.  A hint will not be
           generated closer than 8 instructions away from its branch.  There is little
           reason to disable them, except for debugging purposes, or to make an object a
           little bit smaller.

       -msmall-mem
       -mlarge-mem
           By default, GCC generates code assuming that addresses are never larger than 18
           bits.  With -mlarge-mem code is generated that assumes a full 32 bit address.

       -mstdmain
           By default, GCC links against startup code that assumes the SPU-style main
           function interface (which has an unconventional parameter list).  With
           -mstdmain, GCC will link your program against startup code that assumes a
           C99-style interface to "main", including a local copy of "argv" strings.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed
           register is one that the register allocator can not use.  This is useful when
           compiling kernel code.  A register range is specified as two registers
           separated by a dash.  Multiple register ranges can be specified separated by a
           comma.

       -mdual-nops
       -mdual-nops=n
           By default, GCC will insert nops to increase dual issue when it expects it to
           increase performance.  n can be a value from 0 to 10.  A smaller n will insert
           fewer nops.  10 is the default, 0 is the same as -mno-dual-nops.  Disabled with
           -Os.

       -mhint-max-nops=n
           Maximum number of nops to insert for a branch hint.  A branch hint must be at
           least 8 instructions away from the branch it is effecting.  GCC will insert up
           to n nops to enforce this, otherwise it will not generate the branch hint.

       -mhint-max-distance=n
           The encoding of the branch hint instruction limits the hint to be within 256
           instructions of the branch it is effecting.  By default, GCC makes sure it is
           within 125.

       -msafe-hints
           Work around a hardware bug which causes the SPU to stall indefinitely.  By
           default, GCC will insert the "hbrp" instruction to make sure this stall won't
           happen.

   Options for System V
       These additional options are available on System V Release 4 for compatibility with
       other compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or -shared be used
           instead.

       -Qy Identify the versions of each tool used by the compiler, in a ".ident"
           assembler directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is the
           default).

       -YP,dirs
           Search the directories dirs, and no others, for libraries specified with -l.

       -Ym,dir
           Look in the directory dir to find the M4 preprocessor.  The assembler uses this
           option.

   V850 Options
       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed to be far away,
           the compiler will always load the functions address up into a register, and
           call indirect through the pointer.

       -mno-ep
       -mep
           Do not optimize (do optimize) basic blocks that use the same index pointer 4 or
           more times to copy pointer into the "ep" register, and use the shorter "sld"
           and "sst" instructions.  The -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
           Do not use (do use) external functions to save and restore registers at the
           prologue and epilogue of a function.  The external functions are slower, but
           use less code space if more than one function saves the same number of
           registers.  The -mprolog-function option is on by default if you optimize.

       -mspace
           Try to make the code as small as possible.  At present, this just turns on the
           -mep and -mprolog-function options.

       -mtda=n
           Put static or global variables whose size is n bytes or less into the tiny data
           area that register "ep" points to.  The tiny data area can hold up to 256 bytes
           in total (128 bytes for byte references).

       -msda=n
           Put static or global variables whose size is n bytes or less into the small
           data area that register "gp" points to.  The small data area can hold up to 64
           kilobytes.

       -mzda=n
           Put static or global variables whose size is n bytes or less into the first 32
           kilobytes of memory.

       -mv850
           Specify that the target processor is the V850.

       -mbig-switch
           Generate code suitable for big switch tables.  Use this option only if the
           assembler/linker complain about out of range branches within a switch table.

       -mapp-regs
           This option will cause r2 and r5 to be used in the code generated by the
           compiler.  This setting is the default.

       -mno-app-regs
           This option will cause r2 and r5 to be treated as fixed registers.

       -mv850e1
           Specify that the target processor is the V850E1.  The preprocessor constants
           __v850e1__ and __v850e__ will be defined if this option is used.

       -mv850e
           Specify that the target processor is the V850E.  The preprocessor constant
           __v850e__ will be defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 are defined then a default target
           processor will be chosen and the relevant __v850*__ preprocessor constant will
           be defined.

           The preprocessor constants __v850 and __v851__ are always defined, regardless
           of which processor variant is the target.

       -mdisable-callt
           This option will suppress generation of the CALLT instruction for the v850e and
           v850e1 flavors of the v850 architecture.  The default is -mno-disable-callt
           which allows the CALLT instruction to be used.

   VAX Options
       These -m options are defined for the VAX:

       -munix
           Do not output certain jump instructions ("aobleq" and so on) that the Unix
           assembler for the VAX cannot handle across long ranges.

       -mgnu
           Do output those jump instructions, on the assumption that you will assemble
           with the GNU assembler.

       -mg Output code for g-format floating point numbers instead of d-format.

   VxWorks Options
       The options in this section are defined for all VxWorks targets.  Options specific
       to the target hardware are listed with the other options for that target.

       -mrtp
           GCC can generate code for both VxWorks kernels and real time processes (RTPs).
           This option switches from the former to the latter.  It also defines the
           preprocessor macro "__RTP__".

       -non-static
           Link an RTP executable against shared libraries rather than static libraries.
           The options -static and -shared can also be used for RTPs; -static is the
           default.

       -Bstatic
       -Bdynamic
           These options are passed down to the linker.  They are defined for
           compatibility with Diab.

       -Xbind-lazy
           Enable lazy binding of function calls.  This option is equivalent to -Wl,-z,now
           and is defined for compatibility with Diab.

       -Xbind-now
           Disable lazy binding of function calls.  This option is the default and is
           defined for compatibility with Diab.

   x86-64 Options
       These are listed under

   Xstormy16 Options
       These options are defined for Xstormy16:

       -msim
           Choose startup files and linker script suitable for the simulator.

   Xtensa Options
       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
           Enable or disable use of "CONST16" instructions for loading constant values.
           The "CONST16" instruction is currently not a standard option from Tensilica.
           When enabled, "CONST16" instructions are always used in place of the standard
           "L32R" instructions.  The use of "CONST16" is enabled by default only if the
           "L32R" instruction is not available.

       -mfused-madd
       -mno-fused-madd
           Enable or disable use of fused multiply/add and multiply/subtract instructions
           in the floating-point option.  This has no effect if the floating-point option
           is not also enabled.  Disabling fused multiply/add and multiply/subtract
           instructions forces the compiler to use separate instructions for the multiply
           and add/subtract operations.  This may be desirable in some cases where strict
           IEEE 754-compliant results are required: the fused multiply add/subtract
           instructions do not round the intermediate result, thereby producing results
           with more bits of precision than specified by the IEEE standard.  Disabling
           fused multiply add/subtract instructions also ensures that the program output
           is not sensitive to the compiler's ability to combine multiply and add/subtract
           operations.

       -mserialize-volatile
       -mno-serialize-volatile
           When this option is enabled, GCC inserts "MEMW" instructions before "volatile"
           memory references to guarantee sequential consistency.  The default is
           -mserialize-volatile.  Use -mno-serialize-volatile to omit the "MEMW"
           instructions.

       -mtext-section-literals
       -mno-text-section-literals
           Control the treatment of literal pools.  The default is
           -mno-text-section-literals, which places literals in a separate section in the
           output file.  This allows the literal pool to be placed in a data RAM/ROM, and
           it also allows the linker to combine literal pools from separate object files
           to remove redundant literals and improve code size.  With
           -mtext-section-literals, the literals are interspersed in the text section in
           order to keep them as close as possible to their references.  This may be
           necessary for large assembly files.

       -mtarget-align
       -mno-target-align
           When this option is enabled, GCC instructs the assembler to automatically align
           instructions to reduce branch penalties at the expense of some code density.
           The assembler attempts to widen density instructions to align branch targets
           and the instructions following call instructions.  If there are not enough
           preceding safe density instructions to align a target, no widening will be
           performed.  The default is -mtarget-align.  These options do not affect the
           treatment of auto-aligned instructions like "LOOP", which the assembler will
           always align, either by widening density instructions or by inserting no-op
           instructions.

       -mlongcalls
       -mno-longcalls
           When this option is enabled, GCC instructs the assembler to translate direct
           calls to indirect calls unless it can determine that the target of a direct
           call is in the range allowed by the call instruction.  This translation
           typically occurs for calls to functions in other source files.  Specifically,
           the assembler translates a direct "CALL" instruction into an "L32R" followed by
           a "CALLX" instruction.  The default is -mno-longcalls.  This option should be
           used in programs where the call target can potentially be out of range.  This
           option is implemented in the assembler, not the compiler, so the assembly code
           generated by GCC will still show direct call instructions---look at the
           disassembled object code to see the actual instructions.  Note that the
           assembler will use an indirect call for every cross-file call, not just those
           that really will be out of range.

   zSeries Options
       These are listed under

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions used in code
       generation.

       Most of them have both positive and negative forms; the negative form of -ffoo
       would be -fno-foo.  In the table below, only one of the forms is listed---the one
       which is not the default.  You can figure out the other form by either removing no-
       or adding it.

       -fbounds-check
           For front-ends that support it, generate additional code to check that indices
           used to access arrays are within the declared range.  This is currently only
           supported by the Java and Fortran front-ends, where this option defaults to
           true and false respectively.

       -ftrapv
           This option generates traps for signed overflow on addition, subtraction,
           multiplication operations.

       -fwrapv
           This option instructs the compiler to assume that signed arithmetic overflow of
           addition, subtraction and multiplication wraps around using twos-complement
           representation.  This flag enables some optimizations and disables others.
           This option is enabled by default for the Java front-end, as required by the
           Java language specification.

       -fexceptions
           Enable exception handling.  Generates extra code needed to propagate
           exceptions.  For some targets, this implies GCC will generate frame unwind
           information for all functions, which can produce significant data size
           overhead, although it does not affect execution.  If you do not specify this
           option, GCC will enable it by default for languages like C++ which normally
           require exception handling, and disable it for languages like C that do not
           normally require it.  However, you may need to enable this option when
           compiling C code that needs to interoperate properly with exception handlers
           written in C++.  You may also wish to disable this option if you are compiling
           older C++ programs that don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw exceptions.  Note that
           this requires platform-specific runtime support that does not exist everywhere.
           Moreover, it only allows trapping instructions to throw exceptions, i.e. memory
           references or floating point instructions.  It does not allow exceptions to be
           thrown from arbitrary signal handlers such as "SIGALRM".

       -funwind-tables
           Similar to -fexceptions, except that it will just generate any needed static
           data, but will not affect the generated code in any other way.  You will
           normally not enable this option; instead, a language processor that needs this
           handling would enable it on your behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in dwarf2 format, if supported by target machine.  The
           table is exact at each instruction boundary, so it can be used for stack
           unwinding from asynchronous events (such as debugger or garbage collector).

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer ones, rather
           than in registers.  This convention is less efficient, but it has the advantage
           of allowing intercallability between GCC-compiled files and files compiled with
           other compilers, particularly the Portable C Compiler (pcc).

           The precise convention for returning structures in memory depends on the target
           configuration macros.

           Short structures and unions are those whose size and alignment match that of
           some integer type.

           Warning: code compiled with the -fpcc-struct-return switch is not binary
           compatible with code compiled with the -freg-struct-return switch.  Use it to
           conform to a non-default application binary interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.  This is more
           efficient for small structures than -fpcc-struct-return.

           If you specify neither -fpcc-struct-return nor -freg-struct-return, GCC
           defaults to whichever convention is standard for the target.  If there is no
           standard convention, GCC defaults to -fpcc-struct-return, except on targets
           where GCC is the principal compiler.  In those cases, we can choose the
           standard, and we chose the more efficient register return alternative.

           Warning: code compiled with the -freg-struct-return switch is not binary
           compatible with code compiled with the -fpcc-struct-return switch.  Use it to
           conform to a non-default application binary interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it needs for the declared
           range of possible values.  Specifically, the "enum" type will be equivalent to
           the smallest integer type which has enough room.

           Warning: the -fshort-enums switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Use it to conform
           to a non-default application binary interface.

       -fshort-double
           Use the same size for "double" as for "float".

           Warning: the -fshort-double switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Use it to conform
           to a non-default application binary interface.

       -fshort-wchar
           Override the underlying type for wchar_t to be short unsigned int instead of
           the default for the target.  This option is useful for building programs to run
           under WINE.

           Warning: the -fshort-wchar switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Use it to conform
           to a non-default application binary interface.

       -fno-common
           In C code, controls the placement of uninitialized global variables.  Unix C
           compilers have traditionally permitted multiple definitions of such variables
           in different compilation units by placing the variables in a common block.
           This is the behavior specified by -fcommon, and is the default for GCC on most
           targets.  On the other hand, this behavior is not required by ISO C, and on
           some targets may carry a speed or code size penalty on variable references.
           The -fno-common option specifies that the compiler should place uninitialized
           global variables in the data section of the object file, rather than generating
           them as common blocks.  This has the effect that if the same variable is
           declared (without "extern") in two different compilations, you will get a
           multiple-definition error when you link them.  In this case, you must compile
           with -fcommon instead.  Compiling with -fno-common is useful on targets for
           which it provides better performance, or if you wish to verify that the program
           will work on other systems which always treat uninitialized variable
           declarations this way.

       -fno-ident
           Ignore the #ident directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that would cause
           trouble if the function is split in the middle, and the two halves are placed
           at locations far apart in memory.  This option is used when compiling
           crtstuff.c; you should not need to use it for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to make it more
           readable.  This option is generally only of use to those who actually need to
           read the generated assembly code (perhaps while debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be omitted and
           is useful when comparing two assembler files.

       -frecord-gcc-switches
           This switch causes the command line that was used to invoke the compiler to be
           recorded into the object file that is being created.  This switch is only
           implemented on some targets and the exact format of the recording is target and
           binary file format dependent, but it usually takes the form of a section
           containing ASCII text.  This switch is related to the -fverbose-asm switch, but
           that switch only records information in the assembler output file as comments,
           so it never reaches the object file.

       -fpic
           Generate position-independent code (PIC) suitable for use in a shared library,
           if supported for the target machine.  Such code accesses all constant addresses
           through a global offset table (GOT).  The dynamic loader resolves the GOT
           entries when the program starts (the dynamic loader is not part of GCC; it is
           part of the operating system).  If the GOT size for the linked executable
           exceeds a machine-specific maximum size, you get an error message from the
           linker indicating that -fpic does not work; in that case, recompile with -fPIC
           instead.  (These maximums are 8k on the SPARC and 32k on the m68k and RS/6000.
           The 386 has no such limit.)

           Position-independent code requires special support, and therefore works only on
           certain machines.  For the 386, GCC supports PIC for System V but not for the
           Sun 386i.  Code generated for the IBM RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1.

       -fPIC
           If supported for the target machine, emit position-independent code, suitable
           for dynamic linking and avoiding any limit on the size of the global offset
           table.  This option makes a difference on the m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore works only on
           certain machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but generated position
           independent code can be only linked into executables.  Usually these options
           are used when -pie GCC option will be used during linking.

           -fpie and -fPIE both define the macros "__pie__" and "__PIE__".  The macros
           have the value 1 for -fpie and 2 for -fPIE.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would be more
           efficient than other code generation strategies.  This option is of use in
           conjunction with -fpic or -fPIC for building code which forms part of a dynamic
           linker and cannot reference the address of a jump table.  On some targets, jump
           tables do not require a GOT and this option is not needed.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code should never
           refer to it (except perhaps as a stack pointer, frame pointer or in some other
           fixed role).

           reg must be the name of a register.  The register names accepted are machine-
           specific and are defined in the "REGISTER_NAMES" macro in the machine
           description macro file.

           This flag does not have a negative form, because it specifies a three-way
           choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register that is clobbered by
           function calls.  It may be allocated for temporaries or variables that do not
           live across a call.  Functions compiled this way will not save and restore the
           register reg.

           It is an error to used this flag with the frame pointer or stack pointer.  Use
           of this flag for other registers that have fixed pervasive roles in the
           machine's execution model will produce disastrous results.

           This flag does not have a negative form, because it specifies a three-way
           choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by functions.  It
           may be allocated even for temporaries or variables that live across a call.
           Functions compiled this way will save and restore the register reg if they use
           it.

           It is an error to used this flag with the frame pointer or stack pointer.  Use
           of this flag for other registers that have fixed pervasive roles in the
           machine's execution model will produce disastrous results.

           A different sort of disaster will result from the use of this flag for a
           register in which function values may be returned.

           This flag does not have a negative form, because it specifies a three-way
           choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together without holes.
           When a value is specified (which must be a small power of two), pack structure
           members according to this value, representing the maximum alignment (that is,
           objects with default alignment requirements larger than this will be output
           potentially unaligned at the next fitting location.

           Warning: the -fpack-struct switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Additionally, it
           makes the code suboptimal.  Use it to conform to a non-default application
           binary interface.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.  Just after
           function entry and just before function exit, the following profiling functions
           will be called with the address of the current function and its call site.  (On
           some platforms, "__builtin_return_address" does not work beyond the current
           function, so the call site information may not be available to the profiling
           functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the current function, which
           may be looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline in other
           functions.  The profiling calls will indicate where, conceptually, the inline
           function is entered and exited.  This means that addressable versions of such
           functions must be available.  If all your uses of a function are expanded
           inline, this may mean an additional expansion of code size.  If you use extern
           inline in your C code, an addressable version of such functions must be
           provided.  (This is normally the case anyways, but if you get lucky and the
           optimizer always expands the functions inline, you might have gotten away
           without providing static copies.)

           A function may be given the attribute "no_instrument_function", in which case
           this instrumentation will not be done.  This can be used, for example, for the
           profiling functions listed above, high-priority interrupt routines, and any
           functions from which the profiling functions cannot safely be called (perhaps
           signal handlers, if the profiling routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set the list of functions that are excluded from instrumentation (see the
           description of "-finstrument-functions").  If the file that contains a function
           definition matches with one of file, then that function is not instrumented.
           The match is done on substrings: if the file parameter is a substring of the
           file name, it is considered to be a match.

           For example, "-finstrument-functions-exclude-file-list=/bits/stl,include/sys"
           will exclude any inline function defined in files whose pathnames contain
           "/bits/stl" or "include/sys".

           If, for some reason, you want to include letter ',' in one of sym, write ','.
           For example, "-finstrument-functions-exclude-file-list=',,tmp'" (note the
           single quote surrounding the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to "-finstrument-functions-exclude-file-list", but this option
           sets the list of function names to be excluded from instrumentation.  The
           function name to be matched is its user-visible name, such as "vector<int>
           blah(const vector<int> &)", not the internal mangled name (e.g.,
           "_Z4blahRSt6vectorIiSaIiEE").  The match is done on substrings: if the sym
           parameter is a substring of the function name, it is considered to be a match.

       -fstack-check
           Generate code to verify that you do not go beyond the boundary of the stack.
           You should specify this flag if you are running in an environment with multiple
           threads, but only rarely need to specify it in a single-threaded environment
           since stack overflow is automatically detected on nearly all systems if there
           is only one stack.

           Note that this switch does not actually cause checking to be done; the
           operating system or the language runtime must do that.  The switch causes
           generation of code to ensure that they see the stack being extended.

           You can additionally specify a string parameter: "no" means no checking,
           "generic" means force the use of old-style checking, "specific" means use the
           best checking method and is equivalent to bare -fstack-check.

           Old-style checking is a generic mechanism that requires no specific target
           support in the compiler but comes with the following drawbacks:

           1.  Modified allocation strategy for large objects: they will always be
               allocated dynamically if their size exceeds a fixed threshold.

           2.  Fixed limit on the size of the static frame of functions: when it is topped
               by a particular function, stack checking is not reliable and a warning is
               issued by the compiler.

           3.  Inefficiency: because of both the modified allocation strategy and the
               generic implementation, the performances of the code are hampered.

           Note that old-style stack checking is also the fallback method for "specific"
           if no target support has been added in the compiler.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate code to ensure that the stack does not grow beyond a certain value,
           either the value of a register or the address of a symbol.  If the stack would
           grow beyond the value, a signal is raised.  For most targets, the signal is
           raised before the stack overruns the boundary, so it is possible to catch the
           signal without taking special precautions.

           For instance, if the stack starts at absolute address 0x80000000 and grows
           downwards, you can use the flags -fstack-limit-symbol=__stack_limit and
           -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of 128KB.  Note
           that this may only work with the GNU linker.

       -fargument-alias
       -fargument-noalias
       -fargument-noalias-global
       -fargument-noalias-anything
           Specify the possible relationships among parameters and between parameters and
           global data.

           -fargument-alias specifies that arguments (parameters) may alias each other and
           may alias global storage.-fargument-noalias specifies that arguments do not
           alias each other, but may alias global storage.-fargument-noalias-global
           specifies that arguments do not alias each other and do not alias global
           storage.  -fargument-noalias-anything specifies that arguments do not alias any
           other storage.

           Each language will automatically use whatever option is required by the
           language standard.  You should not need to use these options yourself.

       -fleading-underscore
           This option and its counterpart, -fno-leading-underscore, forcibly change the
           way C symbols are represented in the object file.  One use is to help link with
           legacy assembly code.

           Warning: the -fleading-underscore switch causes GCC to generate code that is
           not binary compatible with code generated without that switch.  Use it to
           conform to a non-default application binary interface.  Not all targets provide
           complete support for this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model argument should be
           one of "global-dynamic", "local-dynamic", "initial-exec" or "local-exec".

           The default without -fpic is "initial-exec"; with -fpic the default is
           "global-dynamic".

       -fvisibility=default|internal|hidden|protected
           Set the default ELF image symbol visibility to the specified option---all
           symbols will be marked with this unless overridden within the code.  Using this
           feature can very substantially improve linking and load times of shared object
           libraries, produce more optimized code, provide near-perfect API export and
           prevent symbol clashes.  It is strongly recommended that you use this in any
           shared objects you distribute.

           Despite the nomenclature, "default" always means public ie; available to be
           linked against from outside the shared object.  "protected" and "internal" are
           pretty useless in real-world usage so the only other commonly used option will
           be "hidden".  The default if -fvisibility isn't specified is "default", i.e.,
           make every symbol public---this causes the same behavior as previous versions
           of GCC.

           A good explanation of the benefits offered by ensuring ELF symbols have the
           correct visibility is given by "How To Write Shared Libraries" by Ulrich
           Drepper (which can be found at <http://people.redhat.com/~drepper/>)---however
           a superior solution made possible by this option to marking things hidden when
           the default is public is to make the default hidden and mark things public.
           This is the norm with DLL's on Windows and with -fvisibility=hidden and
           "__attribute__ ((visibility("default")))" instead of "__declspec(dllexport)"
           you get almost identical semantics with identical syntax.  This is a great boon
           to those working with cross-platform projects.

           For those adding visibility support to existing code, you may find #pragma GCC
           visibility of use.  This works by you enclosing the declarations you wish to
           set visibility for with (for example) #pragma GCC visibility push(hidden) and
           #pragma GCC visibility pop.  Bear in mind that symbol visibility should be
           viewed as part of the API interface contract and thus all new code should
           always specify visibility when it is not the default ie; declarations only for
           use within the local DSO should always be marked explicitly as hidden as so to
           avoid PLT indirection overheads---making this abundantly clear also aids
           readability and self-documentation of the code.  Note that due to ISO C++
           specification requirements, operator new and operator delete must always be of
           default visibility.

           Be aware that headers from outside your project, in particular system headers
           and headers from any other library you use, may not be expecting to be compiled
           with visibility other than the default.  You may need to explicitly say #pragma
           GCC visibility push(default) before including any such headers.

           extern declarations are not affected by -fvisibility, so a lot of code can be
           recompiled with -fvisibility=hidden with no modifications.  However, this means
           that calls to extern functions with no explicit visibility will use the PLT, so
           it is more effective to use __attribute ((visibility)) and/or #pragma GCC
           visibility to tell the compiler which extern declarations should be treated as
           hidden.

           Note that -fvisibility does affect C++ vague linkage entities. This means that,
           for instance, an exception class that will be thrown between DSOs must be
           explicitly marked with default visibility so that the type_info nodes will be
           unified between the DSOs.

           An overview of these techniques, their benefits and how to use them is at
           <http://gcc.gnu.org/wiki/Visibility>.

ENVIRONMENT
       This section describes several environment variables that affect how GCC operates.
       Some of them work by specifying directories or prefixes to use when searching for
       various kinds of files.  Some are used to specify other aspects of the compilation
       environment.

       Note that you can also specify places to search using options such as -B, -I and
       -L.  These take precedence over places specified using environment variables, which
       in turn take precedence over those specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
           These environment variables control the way that GCC uses localization
           information that allow GCC to work with different national conventions.  GCC
           inspects the locale categories LC_CTYPE and LC_MESSAGES if it has been
           configured to do so.  These locale categories can be set to any value supported
           by your installation.  A typical value is en_GB.UTF-8 for English in the United
           Kingdom encoded in UTF-8.

           The LC_CTYPE environment variable specifies character classification.  GCC uses
           it to determine the character boundaries in a string; this is needed for some
           multibyte encodings that contain quote and escape characters that would
           otherwise be interpreted as a string end or escape.

           The LC_MESSAGES environment variable specifies the language to use in
           diagnostic messages.

           If the LC_ALL environment variable is set, it overrides the value of LC_CTYPE
           and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES default to the value of
           the LANG environment variable.  If none of these variables are set, GCC
           defaults to traditional C English behavior.

       TMPDIR
           If TMPDIR is set, it specifies the directory to use for temporary files.  GCC
           uses temporary files to hold the output of one stage of compilation which is to
           be used as input to the next stage: for example, the output of the
           preprocessor, which is the input to the compiler proper.

       GCC_EXEC_PREFIX
           If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of the
           subprograms executed by the compiler.  No slash is added when this prefix is
           combined with the name of a subprogram, but you can specify a prefix that ends
           with a slash if you wish.

           If GCC_EXEC_PREFIX is not set, GCC will attempt to figure out an appropriate
           prefix to use based on the pathname it was invoked with.

           If GCC cannot find the subprogram using the specified prefix, it tries looking
           in the usual places for the subprogram.

           The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the
           prefix to the installed compiler. In many cases prefix is the value of "prefix"
           when you ran the configure script.

           Other prefixes specified with -B take precedence over this prefix.

           This prefix is also used for finding files such as crt0.o that are used for
           linking.

           In addition, the prefix is used in an unusual way in finding the directories to
           search for header files.  For each of the standard directories whose name
           normally begins with /usr/local/lib/gcc (more precisely, with the value of
           GCC_INCLUDE_DIR), GCC tries replacing that beginning with the specified prefix
           to produce an alternate directory name.  Thus, with -Bfoo/, GCC will search
           foo/bar where it would normally search /usr/local/lib/bar.  These alternate
           directories are searched first; the standard directories come next. If a
           standard directory begins with the configured prefix then the value of prefix
           is replaced by GCC_EXEC_PREFIX when looking for header files.

       COMPILER_PATH
           The value of COMPILER_PATH is a colon-separated list of directories, much like
           PATH.  GCC tries the directories thus specified when searching for subprograms,
           if it can't find the subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
           The value of LIBRARY_PATH is a colon-separated list of directories, much like
           PATH.  When configured as a native compiler, GCC tries the directories thus
           specified when searching for special linker files, if it can't find them using
           GCC_EXEC_PREFIX.  Linking using GCC also uses these directories when searching
           for ordinary libraries for the -l option (but directories specified with -L
           come first).

       LANG
           This variable is used to pass locale information to the compiler.  One way in
           which this information is used is to determine the character set to be used
           when character literals, string literals and comments are parsed in C and C++.
           When the compiler is configured to allow multibyte characters, the following
           values for LANG are recognized:

           C-JIS
               Recognize JIS characters.

           C-SJIS
               Recognize SJIS characters.

           C-EUCJP
               Recognize EUCJP characters.

           If LANG is not defined, or if it has some other value, then the compiler will
           use mblen and mbtowc as defined by the default locale to recognize and
           translate multibyte characters.

       Some additional environments variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by a special
           character, much like PATH, in which to look for header files.  The special
           character, "PATH_SEPARATOR", is target-dependent and determined at GCC build
           time.  For Microsoft Windows-based targets it is a semicolon, and for almost
           all other targets it is a colon.

           CPATH specifies a list of directories to be searched as if specified with -I,
           but after any paths given with -I options on the command line.  This
           environment variable is used regardless of which language is being
           preprocessed.

           The remaining environment variables apply only when preprocessing the
           particular language indicated.  Each specifies a list of directories to be
           searched as if specified with -isystem, but after any paths given with -isystem
           options on the command line.

           In all these variables, an empty element instructs the compiler to search its
           current working directory.  Empty elements can appear at the beginning or end
           of a path.  For instance, if the value of CPATH is ":/special/include", that
           has the same effect as -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for
           Make based on the non-system header files processed by the compiler.  System
           header files are ignored in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the
           Make rules are written to that file, guessing the target name from the source
           file name.  Or the value can have the form file target, in which case the rules
           are written to file file using target as the target name.

           In other words, this environment variable is equivalent to combining the
           options -MM and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that
           system header files are not ignored, so it implies -M rather than -MM.
           However, the dependence on the main input file is omitted.

BUGS
       For instructions on reporting bugs, see <http://bugzilla.redhat.com/bugzilla>.

FOOTNOTES
       1.  On some systems, gcc -shared needs to build supplementary stub code for
           constructors to work.  On multi-libbed systems, gcc -shared must select the
           correct support libraries to link against.  Failing to supply the correct flags
           may lead to subtle defects.  Supplying them in cases where they are not
           necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1),
       dbx(1), sdb(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR
       See the Info entry for gcc, or
       <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for contributors to GCC.

COPYRIGHT
       Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
       2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the
       terms of the GNU Free Documentation License, Version 1.2 or any later version
       published by the Free Software Foundation; with the Invariant Sections being "GNU
       General Public License" and "Funding Free Software", the Front-Cover texts being
       (a) (see below), and with the Back-Cover Texts being (b) (see below).  A copy of
       the license is included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.



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