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Use of a specific gcc O3 flag on AMD64 architecture
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rapunzelcardoso
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Joined: 26 May 2010
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PostPosted: Tue Feb 08, 2011 5:05 am    Post subject: Use of a specific gcc O3 flag on AMD64 architecture Reply with quote

Hello, followers of the cow. I've read that the -O3 gcc flag enables optimizations that basically fuck up. Now, i've saw exactly what those optimizations are and one is to do crazy inlining and other one is to use more registers on architectures with many registers (-frename-registers). So, since -03 by itself is said to be evil but -frename-registers should be advantageous on amd64 since it has some registers (at least more than x86 so I'm thinking it qualifies as good for the flag), anyone knows if 02 + -frename-registers is safe? I know that safe is a poorly defined word so let's say "safe so that it doesn't fuck up more than 1 application in 100". Hugs to everybody that follows Larry the cow.
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salahx
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PostPosted: Tue Feb 08, 2011 5:30 am    Post subject: Reply with quote

On amd64 -frename-registers is already enabled.

You can see exactly what optimization are included in -O2 with
Code:

gcc -O2 -Q --help=optimizers
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rapunzelcardoso
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PostPosted: Tue Feb 08, 2011 5:44 am    Post subject: Reply with quote

salahx wrote:
On amd64 -frename-registers is already enabled.

You can see exactly what optimization are included in -O2 with
Code:

gcc -O2 -Q --help=optimizers


Thank you salahx
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pilla
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PostPosted: Fri Mar 11, 2011 1:46 pm    Post subject: Reply with quote

Moved from Gentoo Chat to Gentoo on AMD64.
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