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Re: Compilation flags in libgfortran
- From: pinskia at gmail dot com
- To: Igor Zamyatin <izamyatin at gmail dot com>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, Yuri Rumyantsev <ysrumyan at gmail dot com>
- Date: Wed, 16 Oct 2013 02:37:59 -0700
- Subject: Re: Compilation flags in libgfortran
- Authentication-results: sourceware.org; auth=none
- References: <CAKdSQZk4gBwLOXPNL+Z+Nc8476S0acuFMKYS3QLG=hkzzLCqbQ at mail dot gmail dot com>
> On Oct 15, 2013, at 6:58 AM, Igor Zamyatin <izamyatin@gmail.com> wrote:
>
> Hi All!
>
> Is there any particular reason that matmul* modules from libgfortran
> are compiled with -O2 -ftree-vectorize?
>
> I see some regressions on Atom processor after r202980
> (http://gcc.gnu.org/ml/gcc-cvs/2013-09/msg00846.html)
>
> Why not just use O3 for those modules?
-O3 and -O2 -ftree-vectorize won't give much performance difference. What you are seeing is the cost model needs improvement; at least for atom.
>
>
> Thanks,
> Igor