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-O and other optimization flags

From: zhou13 at netscape dot net
To: gcc-help at gcc dot gnu dot org
Date: Tue, 04 Jul 2006 00:54:21 -0400
Subject: -O and other optimization flags

Hello GCC-Help list:

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?

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".

The codec is at http://www.sourceforge.net/projects/openavs/. Currently, it requires a 3Ghz or better CPU to get a resonable framerate. I would like the codec to be useful even on 586 ( 1Ghz or so ). Any ideas?

Regards
Lionel

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