Brian Dessent <brian@xxxxxxxxxxx> writes: > PRC wrote: > >> How about performance of the program compiled by -O2 other than -Os? >> I think -O2 will be better than -Os? But I am not sure how better. > > It's impossible to answer such a vague question, as it depends on the > target architecture, the version of gcc, and most significantly the > nature of the code. You can only answer these kinds of questions with a > testcase, but I would not rule out -Os being faster in some > circumstances and on some architectures due to more code fitting in the > cache or better locality. This is correct. I'll just add that -Os is the same as -O2, except that when there is a tradeoff between space and time -Os prefers space and -O2 prefers time. As these are heuristic tradeoffs, it is entirely possible that -Os will generate faster code in some cases. Ian
