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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/101097] Vectorizer is too eager to use
 vec_unpack
Date: Thu, 17 Jun 2021 07:29:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101097

--- Comment #6 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Richard Biener from comment #5)
> (In reply to Uro=C5=A1 Bizjak from comment #3)
> > Created attachment 51031 [details]
> > Pack/unpack patterns for 8-byte vectors
> >=20
> > FYI, this patch adds pack/unpack patterns for 8-byte vectors. It will f=
ail:
> >=20
> > FAIL: gcc.target/i386/pr97249-1.c scan-assembler-times (?n)vpmovzxbw[
> > \\\\t]+\\\\(.*%xmm[0-9] 2
> > FAIL: gcc.target/i386/pr97249-1.c scan-assembler-times (?n)vpmovzxwd[
> > \\\\t]+\\\\(.*%xmm[0-9] 2
> >=20
> > due to the mentioned issue.
>=20
> You can add #pragma GCC unroll 8/4 to "fix" that and add a comment this t=
est
> tests BB vectorization.  Loop vectorization would have failed even before
> the patch (and now succeeds, but with less optimal code).

I just to want to classify the test is used to test another optimization wh=
ich
rely on either loop vectorization or slp. it means it's ok to add unroll pr=
agma
here.=