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From: "haochen.jiang at intel dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/115069] [14/15 regression] 8 bit integer vector
 performance regression, x86, between gcc-14 and gcc-13 using avx2 target
 clones on skylake platform
Date: Mon, 20 May 2024 05:50:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115069

--- Comment #12 from Haochen Jiang <haochen.jiang at intel dot com> ---
(In reply to Hongtao Liu from comment #11)
> (In reply to Haochen Jiang from comment #10)
> > A patch like Comment 8 could definitely solve the problem. But I need to
> > test more benchmarks to see if there is surprise.
> >=20
> > But, yes, as Uros said in Comment 9, maybe there is a chance we could d=
o it
> > better.
>=20
> Could you add "arch=3Dskylake-avx512" to target_clones and try disable wh=
ole
> ix86_expand_vecop_qihi2 to see if there's any performance improvement?
> For x86, cross-lane permutation(truncation) is not very efficient(3-4 cyc=
les
> for both vpermq and vpmovwb).

When I disable/enable ix86_expand_vecop_qihi2 with arch=3Dskylake-avx512 on
trunk, there is no performance regression comparing to GCC13 + avx2.

It seems that the regression only happens when GCC14 + avx2.=