$ gcc --help=optimizers サポートする最適化オプションを表示 The following options control optimizations: -O<number> Set optimization level to <number>. -Ofast Optimize for speed disregarding exact standards compliance. -Og Optimize for debugging experience rather than speed or size. -Os Optimize for space rather than speed. -faggressive-loop-optimizations Aggressively optimize loops using language constraints. -falign-functions Align the start of functions. ︙ -fvar-tracking-uninit Perform variable tracking and also tag variables that are uninitialized. -fvariable-expansion-in-unroller Apply variable expansion when loops are unrolled. Specifies the cost model for vectorization. -fvect-cost-model=[unlimited|dynamic|cheap] Specifies the cost model for vectorization. -fvpt Use expression value profiles in optimizations. -fweb Construct webs and split unrelated uses of single variable. -fwrapv Assume signed arithmetic overflow wraps around. -fwrapv-pointer Assume pointer overflow wraps around. $