GCC 4.7の最適化オプション比較表

GCCの各オプティマイズレベルで有効になる最適化を調べる - Life is very short

の GCC 4.7版。"-Ofast"を追加しました。"-Ofast"は規約を一部
無視した最適化を行うようです。"-O3"より高速になるよう意図
されています。

なお GCC 4.8では "-Og"という最適化とデバッグ機能を兼ね備えた
オプションが追加されるそうです。需要がわかりづらいですが・・・。

表生成スクリプト

#!/usr/bin/env perl
use strict;
use warnings;

$ENV{LANG} = 'C';

my @levels = qw(-O0 -O1 -O2 -O3 -Os -Ofast);

my @base = qw(gcc -- -Q --help=optimizers);

my %optimize;
for my $level (@levels) {
    my @cmd = @base;
    $cmd[1] = $level;

    open my $fh, "-|", @cmd or die "Can't exec @cmd";

    while (my $line = <$fh>) {
        chomp $line;

        next unless $line =~ m{(?:enabled|disabled)};

        if ($line =~ m{(\S+) \s+ \[ ([^\]]+) \]}xms) {
            my ($option, $flag) = ($1, $2);

            if ($flag eq 'enabled') {
                $optimize{$level}->{$option} = 1;
            } else {
                $optimize{$level}->{$option} = 0;
            }
        }
    }
    close $fh;
}

print "|*|";
print "*$_|" for @levels;
print "\n";

for my $key (sort keys %{$optimize{'-O0'}}) {
    print "|$key|";
    for my $level (@levels) {
        printf "%s|",  $optimize{$level}->{$key} == 1 ? "o" : 'x';
    }
    print "\n";
}

比較表

	-O0	-O1	-O2	-O3	-Os	-Ofast
-falign-functions	x	x	o	o	o	o
-falign-jumps	x	x	o	o	o	o
-falign-labels	x	x	o	o	o	o
-falign-loops	x	x	o	o	o	o
-fasynchronous-unwind-tables	o	o	o	o	o	o
-fbranch-count-reg	o	o	o	o	o	o
-fbranch-probabilities	x	x	x	x	x	x
-fbranch-target-load-optimize	x	x	x	x	x	x
-fbranch-target-load-optimize2	x	x	x	x	x	x
-fbtr-bb-exclusive	x	x	x	x	x	x
-fcaller-saves	x	x	o	o	o	o
-fcombine-stack-adjustments	x	o	o	o	o	o
-fcommon	o	o	o	o	o	o
-fcompare-elim	x	o	o	o	o	o
-fconserve-stack	x	x	x	x	x	x
-fcprop-registers	x	o	o	o	o	o
-fcrossjumping	x	x	o	o	o	o
-fcse-follow-jumps	x	x	o	o	o	o
-fcx-fortran-rules	x	x	x	x	x	x
-fcx-limited-range	x	x	x	x	x	o
-fdata-sections	x	x	x	x	x	x
-fdce	o	o	o	o	o	o
-fdefer-pop	x	o	o	o	o	o
-fdelayed-branch	x	x	x	x	x	x
-fdelete-null-pointer-checks	o	o	o	o	o	o
-fdevirtualize	x	x	o	o	o	o
-fdse	o	o	o	o	o	o
-fearly-inlining	o	o	o	o	o	o
-fexceptions	x	x	x	x	x	x
-fexpensive-optimizations	x	x	o	o	o	o
-ffinite-math-only	x	x	x	x	x	o
-ffloat-store	x	x	x	x	x	x
-fforward-propagate	x	o	o	o	o	o
-fgcse	x	x	o	o	o	o
-fgcse-after-reload	x	x	x	o	x	o
-fgcse-las	x	x	x	x	x	x
-fgcse-lm	o	o	o	o	o	o
-fgcse-sm	x	x	x	x	x	x
-fgraphite-identity	x	x	x	x	x	x
-fguess-branch-probability	x	o	o	o	o	o
-fif-conversion	x	o	o	o	o	o
-fif-conversion2	x	o	o	o	o	o
-finline-atomics	o	o	o	o	o	o
-finline-functions	x	x	x	o	o	o
-finline-functions-called-once	x	o	o	o	o	o
-finline-small-functions	x	x	o	o	o	o
-fipa-cp	x	x	o	o	o	o
-fipa-cp-clone	x	x	x	o	x	o
-fipa-matrix-reorg	x	x	x	x	x	x
-fipa-profile	x	o	o	o	o	o
-fipa-pta	x	x	x	x	x	x
-fipa-pure-const	x	o	o	o	o	o
-fipa-reference	x	o	o	o	o	o
-fipa-sra	x	x	o	o	o	o
-fivopts	o	o	o	o	o	o
-fjump-tables	o	o	o	o	o	o
-floop-block	x	x	x	x	x	x
-floop-flatten	x	x	x	x	x	x
-floop-interchange	x	x	x	x	x	x
-floop-parallelize-all	x	x	x	x	x	x
-floop-strip-mine	x	x	x	x	x	x
-fmath-errno	o	o	o	o	o	x
-fmerge-all-constants	x	x	x	x	x	x
-fmerge-constants	x	o	o	o	o	o
-fmodulo-sched	x	x	x	x	x	x
-fmove-loop-invariants	o	o	o	o	o	o
-fno-threadsafe-statics	o	o	o	o	o	o
-fnon-call-exceptions	x	x	x	x	x	x
-fnothrow-opt	x	x	x	x	x	x
-fomit-frame-pointer	x	x	x	x	x	x
-foptimize-register-move	x	x	o	o	o	o
-foptimize-sibling-calls	x	x	o	o	o	o
-foptimize-strlen	x	x	o	o	x	o
-fpack-struct	x	x	x	x	x	x
-fpeel-loops	x	x	x	x	x	x
-fpeephole	o	o	o	o	o	o
-fpeephole2	x	x	o	o	o	o
-fpredictive-commoning	x	x	x	o	x	o
-fprefetch-loop-arrays	o	o	o	o	o	o
-freg-struct-return	x	x	x	x	x	x
-fregmove	x	x	o	o	o	o
-frename-registers	o	o	o	o	o	o
-freorder-blocks	x	x	o	o	o	o
-freorder-blocks-and-partition	x	x	x	x	x	x
-freorder-functions	x	x	o	o	o	o
-frerun-cse-after-loop	x	x	o	o	o	o
-freschedule-modulo-scheduled-loops	x	x	x	x	x	x
-frounding-math	x	x	x	x	x	x
-frtti	o	o	o	o	o	o
-fsched-critical-path-heuristic	o	o	o	o	o	o
-fsched-dep-count-heuristic	o	o	o	o	o	o
-fsched-group-heuristic	o	o	o	o	o	o
-fsched-interblock	o	o	o	o	o	o
-fsched-last-insn-heuristic	o	o	o	o	o	o
-fsched-pressure	x	x	x	x	x	x
-fsched-rank-heuristic	o	o	o	o	o	o
-fsched-spec	o	o	o	o	o	o
-fsched-spec-insn-heuristic	o	o	o	o	o	o
-fsched-spec-load	x	x	x	x	x	x
-fsched-spec-load-dangerous	x	x	x	x	x	x
-fsched-stalled-insns	x	x	x	x	x	x
-fsched-stalled-insns-dep	o	o	o	o	o	o
-fsched2-use-superblocks	x	x	x	x	x	x
-fschedule-insns	x	x	x	x	x	x
-fschedule-insns2	x	x	o	o	o	o
-fsection-anchors	x	x	x	x	x	x
-fsel-sched-pipelining	x	x	x	x	x	x
-fsel-sched-pipelining-outer-loops	x	x	x	x	x	x
-fsel-sched-reschedule-pipelined	x	x	x	x	x	x
-fselective-scheduling	x	x	x	x	x	x
-fselective-scheduling2	x	x	x	x	x	x
-fshort-double	x	x	x	x	x	x
-fshort-enums	o	o	o	o	o	o
-fshort-wchar	x	x	x	x	x	x
-fshrink-wrap	x	o	o	o	o	o
-fsignaling-nans	x	x	x	x	x	x
-fsigned-zeros	o	o	o	o	o	x
-fsingle-precision-constant	x	x	x	x	x	x
-fsplit-ivs-in-unroller	o	o	o	o	o	o
-fsplit-wide-types	x	o	o	o	o	o
-fstrict-aliasing	x	x	o	o	o	o
-fstrict-enums	x	x	x	x	x	x
-fthread-jumps	x	x	o	o	o	o
-ftoplevel-reorder	o	o	o	o	o	o
-ftrapping-math	o	o	o	o	o	x
-ftrapv	x	x	x	x	x	x
-ftree-bit-ccp	x	o	o	o	o	o
-ftree-builtin-call-dce	x	x	o	o	o	o
-ftree-ccp	x	o	o	o	o	o
-ftree-ch	x	o	o	o	o	o
-ftree-copy-prop	x	o	o	o	o	o
-ftree-copyrename	x	o	o	o	o	o
-ftree-cselim	o	o	o	o	o	o
-ftree-dce	x	o	o	o	o	o
-ftree-dominator-opts	x	o	o	o	o	o
-ftree-dse	x	o	o	o	o	o
-ftree-forwprop	o	o	o	o	o	o
-ftree-fre	x	o	o	o	o	o
-ftree-loop-distribute-patterns	x	x	x	o	x	o
-ftree-loop-distribution	x	x	x	x	x	x
-ftree-loop-if-convert	o	o	o	o	o	o
-ftree-loop-if-convert-stores	x	x	x	x	x	x
-ftree-loop-im	o	o	o	o	o	o
-ftree-loop-ivcanon	o	o	o	o	o	o
-ftree-loop-optimize	o	o	o	o	o	o
-ftree-lrs	x	x	x	x	x	x
-ftree-partial-pre	x	x	x	o	x	o
-ftree-phiprop	o	o	o	o	o	o
-ftree-pre	x	x	o	o	o	o
-ftree-pta	o	o	o	o	o	o
-ftree-reassoc	o	o	o	o	o	o
-ftree-scev-cprop	o	o	o	o	o	o
-ftree-sink	x	o	o	o	o	o
-ftree-slp-vectorize	o	o	o	o	o	o
-ftree-sra	x	o	o	o	o	o
-ftree-switch-conversion	x	x	o	o	o	o
-ftree-tail-merge	x	x	o	o	o	o
-ftree-ter	x	o	o	o	o	o
-ftree-vect-loop-version	o	o	o	o	o	o
-ftree-vectorize	x	x	x	o	x	o
-ftree-vrp	x	x	o	o	o	o
-funit-at-a-time	o	o	o	o	o	o
-funroll-all-loops	x	x	x	x	x	x
-funroll-loops	x	x	x	x	x	x
-funsafe-loop-optimizations	x	x	x	x	x	x
-funsafe-math-optimizations	x	x	x	x	x	o
-funswitch-loops	x	x	x	o	x	o
-funwind-tables	x	x	x	x	x	x
-fvar-tracking	o	o	o	o	o	o
-fvar-tracking-assignments	o	o	o	o	o	o
-fvar-tracking-assignments-toggle	x	x	x	x	x	x
-fvar-tracking-uninit	x	x	x	x	x	x
-fvariable-expansion-in-unroller	x	x	x	x	x	x
-fvect-cost-model	o	o	o	o	o	o
-fvpt	x	x	x	x	x	x
-fweb	o	o	o	o	o	o
-fwhole-program	x	x	x	x	x	x
-fwrapv	x	x	x	x	x	x