-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 -fipa-pure-const -fipa-reference -fmerge-constants -fshrink-wrap
-fsplit-wide-types -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copyrename -ftree-dce
-ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-sra -ftree-pta
-ftree-ter -funit-at-a-time
-O also turns on -fomit-frame-pointer on machines where doing so does not interfere with debugging.
|