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Re: [PATCH] Detect i586 and i686 features at run-time

From: Mike Frysinger <vapier at gentoo dot org>
To: "H.J. Lu" <hjl dot tools at gmail dot com>
Cc: Joseph Myers <joseph at codesourcery dot com>, GNU C Library <libc-alpha at sourceware dot org>
Date: Wed, 19 Aug 2015 09:18:11 -0400
Subject: Re: [PATCH] Detect i586 and i686 features at run-time
Authentication-results: sourceware.org; auth=none
References: <CAMe9rOqG_SVzgUrO2DjkRZWKJfFFGE6rYqCsmUxb3dPPti=8uw at mail dot gmail dot com> <20150819042011 dot GW1584 at vapier> <CAMe9rOqVSjoBnnweK0NYHf1RwjGq-sYRBT9cG_ZNkY6eUq8-hw at mail dot gmail dot com>

On 19 Aug 2015 04:19, H.J. Lu wrote:
> On Tue, Aug 18, 2015 at 9:20 PM, Mike Frysinger wrote:
> > On 18 Aug 2015 11:25, H.J. Lu wrote:
> >> We detect i586 and i686 features at run-time by checking CX8 and CMOV
> >> CPUID features bits.  We can use these information to select the best
> >> implementation in ix86 multiarch.
> >
> > there are i686's w/out cmov.  shouldn't multiarch implementations that use
> > certain insns be tied to those rather than a big knob like "i686" ?
> 
> For purpose glibc build, i686 has cmov:
> 
> [hjl@gnu-tools-1 glibc]$ grep cmov sysdeps/i386/i686/*.S
> sysdeps/i386/i686/strcmp.S: cmovbl %ecx, %eax
> sysdeps/i386/i686/strtok.S: cmove %eax, %edx
> sysdeps/i386/i686/strtok.S: cmovne %ecx, %edx

i think that deserves a comment in the source
-mike

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References:
- [PATCH] Detect i586 and i686 features at run-time
  - From: H.J. Lu
- Re: [PATCH] Detect i586 and i686 features at run-time
  - From: Mike Frysinger
- Re: [PATCH] Detect i586 and i686 features at run-time
  - From: H.J. Lu

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