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Re: Benchmark of gcc 4.0

From: Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>
To: GCC Development <gcc at gcc dot gnu dot org>
Date: Thu, 24 Feb 2005 16:52:51 +0100
Subject: Re: Benchmark of gcc 4.0
References: <200502241504.17936.lucini@phys.ethz.ch> <421DF24F.2060104@redhat.com>

For GCC, I used in both cases the flags
-march=pentium4 -mfpmath=sse -O3 -fomit-frame-pointer -ffast-math

>

As for gcc4 vs gcc3.4, degradataion on x86 architecture is most probably because of higher register pressure created with more aggressive SSA optimizations in gcc4.

Try these five combinations:

-O2 -fomit-frame-pointer -ffast-math
-O2 -fomit-frame-pointer -ffast-math -fno-tree-pre
-O2 -fomit-frame-pointer -ffast-math -fno-tree-pre -fno-gcse

-O3 -fomit-frame-pointer -ffast-math -fno-tree-pre
-O3 -fomit-frame-pointer -ffast-math -fno-tree-pre -fno-gcse

You may also want to try -mfpmath=sse,387 in case your benchmarks use sin, cos and other trascendental functions that GCC knows about when using 387 instructions.

Paolo

Follow-Ups:
- Re: Benchmark of gcc 4.0
  - From: Biagio Lucini

References:
- Benchmark of gcc 4.0
  - From: Biagio Lucini
- Re: Benchmark of gcc 4.0
  - From: Vladimir Makarov

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