This question is not appropriate for the gcc@gcc.gnu.org mailing list. It would be appropriate on the [EMAIL PROTECTED] mailing list. Thanks.
[EMAIL PROTECTED] writes: > I am wondering if i have used -O, -O2 or -O3, do i still benifit from > flags such as -march -fmpmath -ffast-math -mmx -sse -sse2 -3dnow? Yes, although the effects will depend on your code. In particular those options will mainly affect floating point code. And you may want to use -mtune as well. > I am optimizing a video codec and i see barely any performance > difference whether i use just -O2 or "-ffast-math -march=athlon-xp > -mmmx -msse -msse2 -m3dnow -mfpmath=sse,387 -O3". I recommend approaching this as you would any performance problem: use a profiler to identify the slowest parts of your code, and see what you can do to make them faster. It may be helpful to look at the generated assembly code: compile with the --save-temps option and look at the .s file. Ian
