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Re: [PATCH] Compile AVX libm functions with -mavx -mprefer-avx128
- From: Andreas Jaeger <aj at suse dot com>
- To: libc-alpha at sourceware dot org
- Cc: "H.J. Lu" <hjl dot tools at gmail dot com>,OndÅej BÃlka <neleai at seznam dot cz>,Mike Frysinger <vapier at gentoo dot org>
- Date: Thu, 04 Oct 2012 15:08:56 +0200
- Subject: Re: [PATCH] Compile AVX libm functions with -mavx -mprefer-avx128
- References: <CAMe9rOrnn9r3viYefdNb_dbx25Lp9HqXXEK9tj23NsyDE+41aQ@mail.gmail.com>
On Tuesday, October 02, 2012 13:54:11 H.J. Lu wrote:
> On Tue, Oct 2, 2012 at 12:47 PM, OndÅej BÃlka <neleai@seznam.cz>
wrote:
> > On Tue, Oct 02, 2012 at 03:31:50PM -0400, Mike Frysinger wrote:
> >> On Tuesday 02 October 2012 15:20:54 H.J. Lu wrote:
> >> > On Tue, Oct 2, 2012 at 12:02 PM, Mike Frysinger
<vapier@gentoo.org> wrote:
> >> > > On Tuesday 02 October 2012 09:53:25 H.J. Lu wrote:
> >> > >> This patch compiles AVX libm functions with -mavx. It reduces
> >> > >> text size>> > >
> >> > >> of libm.so by about 1%:
> >> > > looks like you're reverting
> >> > > 56f6f6a2403cfa7267cad722597113be35ecf70d.
> >> > > shouldn't you revert all of it and not just change the CFLAGS
> >> > > back ?
> >> >
> >> > Doesn't this patch:
> >> >
> >> > http://sourceware.org/ml/libc-alpha/2012-10/msg00055.html
> >> >
> >> > do that?
> >>
> >> yes, i missed the follow up
> >>
> >> > > it'd be useful to know *why* Ulrich moved away from -mavx, but
> >> > > unfortunately his commit message is useless.
> >> >
> >> > I can only guess:
> >> might be useful to put some notes (like referring to the older
> >> commit) into the commit message when you do commit things
> >> -mike
> >
> > could it be a 60 cycle penalty when switching between legagy sse and
> > avx state?
>
> Here is a patch to compile AVX libm functions with -mavx
> -mprefer-avx128.
Let's first get some benchmarks for these changes, please,
Andreas
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Andreas Jaeger aj@{suse.com,opensuse.org} Twitter/Identica: jaegerandi
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