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From: "aurelien at aurel32 dot net" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug string/29611] Optimized AVX2 string functions unconditionally
 use BMI2 instructions
Date: Mon, 26 Sep 2022 05:19:48 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29611

--- Comment #5 from Aurelien Jarno <aurelien at aurel32 dot net> ---
(In reply to Noah Goldstein from comment #3)
> (In reply to Noah Goldstein from comment #2)
> > This was fixed by:
> >=20
> > commit 83c5b368226c34a2f0a5287df40fc290b2b34359
> > Author: H.J. Lu <hjl.tools@gmail.com>
> > Date:   Mon Apr 19 10:45:07 2021 -0700
> >=20
> >     x86-64: Require BMI2 for strchr-avx2.S
> >=20
> > Which we can probably backport easily. The issue is that some avx2 chan=
ges
> > where backported without the surrounding ifunc code.
> >
>=20
> I think this needs to be backported to:
> 2.28-2.32=20
>=20
> I applies cleanly on 2.32
>=20
> but for 2.28 - 2.31 it depends on:
>=20
> commit 107e6a3c2212ba7a3a4ec7cae8d82d73f7c95d0b (HEAD)
> Author: H.J. Lu <hjl.tools@gmail.com>
> Date:   Mon Jun 29 16:36:08 2020 -0700
>=20
>     x86: Support usable check for all CPU features
>=20

If that one is too complicated to backport to 2.31, maybe it's easier to re=
vert
the optimization in 2.31?

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