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On Wednesday 27 September 2006 07:50, Daniel Iliev wrote: |
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> |
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> 1) I use CFLAGS="-march=athlon64 -mfpmath=sse -msse -msse2 -msse3 |
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> -m3dnow -mmmx -O3 -fomit-frame-pointer -pipe -fpic". P |
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-mfpmath=sse not needed. amd64 uses sse for math by default. remove that flag |
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-msse not needed, see above |
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-msse2 not needed, see above |
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-msse3 can be set, but only if your CPU supports it. Not all CPUs do. |
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Check /proc/cpuinfo for 'pni' |
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-m3dnow just no. sse supersedes it. Also it is a '32bit flag' |
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-mmmx see above |
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-O3 don't do it. O2 is much, much safer and not really slower. It will prevent |
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a lot of breakage. |
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-fomit-frame-pointer not needed |
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-pipe a good flag |
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-fpic NO! Really, really really no! Don't do it! It is just wrong. Stop it |
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now! This flag is not needed! Even for prelink on 32bit it was never needed |
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(because everything that could compiled with that flag set it anyway). |
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Please, read the documentation and remove that flag ASAP. |
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so, march=k8 -O2 -pipe |
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would be the result, if you remove all superflous and dangerous flags. |
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> |
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> 2) I see too many flags that are disabled by the profile - the kind with |
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> the parenthesis around them, like "(-3dnow)". Why? As I mentioned above |
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> I enable some of these through my CFLAGS - e.g. (-mmx), (-mmxext), |
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> (-sse) and (-sse2) and everything works perfect. |
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because 3dnow, mmx&co are useflags for 32bit code that was optimized for that |
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extensions. If you use that code in 64bit apps, certain breakage is the |
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result. And if something does not break, it will be A LOT slower. |
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Don't use that flags. They are bad for amd64. Trust the devs, they know better |
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than you or me. |
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-- |
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gentoo-amd64@g.o mailing list |
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