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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug testsuite/102861] [12 regression] gcc.dg/vect/bb-slp-16.c fails
 after r12-4526
Date: Thu, 21 Oct 2021 07:53:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102861

--- Comment #6 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
> > Is there something else we could do?
>=20
> Look what exactly is missing and restore that - testcases are written
> from real-world code that we expect to optimize, adjusting them to
> hide the fact that we don't any longer is not good.
>=20
> Even XFAIL would have been better.

Heh.  That was my original suggestion, but I was vetoed :).

>=20
> That said, loop header copying is supposed to do the rotation.
>=20
> Note what I see on the unchanged testcase is that we now loop vectorize
> which is great (and obviously no BB vectorization opportunity remains).
> So a different fix would be to simply add
>=20
> /* Avoid loop vectorization.  */
> /* { dg-additional-options "-fno-tree-loop-vectorize" } */
>=20
> which makes the testcase PASS again (bonus for adding a variant
> of the testcase that verifies we loop vectorize this).
>=20
> Let me do all this for you.

Thanks so much!=