From: Richard Guenther <richard.guenther@gmail.com>
To: Vladimir Makarov <vmakarov@redhat.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Comparison of GCC-4.6.1 and LLVM-2.9 on x86/x86-64 targets
Date: Thu, 08 Sep 2011 08:23:00 -0000 [thread overview]
Message-ID: <CAFiYyc29nUcPvC0fk7B1d7J-gP-7S9q8KYBnL9q3T0tCq9YBuw@mail.gmail.com> (raw)
In-Reply-To: <4E679A9A.1070408@redhat.com>
On Wed, Sep 7, 2011 at 6:23 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
> On 09/07/2011 11:55 AM, Xinliang David Li wrote:
>>
>> Why is lto/whole program mode not used in LLVM for peak performance
>> comparison? (of course, peak performance should really use FDO..)
>>
> Thanks for the feedback. I did not manage to use LTO for LLVM as it
> described on
>
> http://llvm.org/docs/LinkTimeOptimization.html#lto
>
> I am getting 'file not recognized: File format not recognized' during the
> linkage pass.
>
> You probably right that I should use -Ofast without -flto for gcc then.
> Although I don't think that it significantly change GCC peak performance.
> Still I am going to run SPEC2000 without -flto and post the data (probably
> on the next week).
Note that due to a bug in 4.6.x -Ofast is not equivalent to -O3 -ffast-math
(it doesn't use crtfastmath.o). I'll backport the fix.
> As for FDO, unfortunately for some tests SPEC uses different training sets
> and it gives sometimes wrong info for the further optimizations.
>
> I do not look at this comparison as finished work and am going to run more
> SPEC2000 tests and change the results if I have serious reasonable
> objections for the current comparison.
>
next prev parent reply other threads:[~2011-09-08 8:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-07 15:16 Vladimir Makarov
2011-09-07 15:29 ` Duncan Sands
2011-09-07 16:59 ` Vladimir Makarov
2011-09-07 15:55 ` Xinliang David Li
2011-09-07 16:24 ` Vladimir Makarov
2011-09-08 8:23 ` Richard Guenther [this message]
2011-09-08 9:22 ` Duncan Sands
2011-09-09 14:02 ` Vladimir Makarov
2011-09-07 17:01 ` Duncan Sands
2011-09-08 8:47 ` Jakub Jelinek
2011-09-09 14:26 ` Vladimir Makarov
2011-09-09 14:36 ` Jakub Jelinek
2011-09-09 23:30 ` Lawrence Crowl
2011-09-10 13:22 ` Gabriel Dos Reis
2011-09-12 16:40 ` Vladimir Makarov
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