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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/97770] [ICELAKE]suboptimal vectorization for
 vpopcntw/b/q
Date: Fri, 11 Jun 2021 07:25:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97770

--- Comment #20 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to H.J. Lu from comment #19)
> (In reply to rguenther@suse.de from comment #18)
> >=20
> > That's going to work I guess but it will pessimize general optimization
> > which no longer know this is computing popcount (not sure if the old
> > version exposed that fact).
>=20
> Do we have testcase for that?

Sth like

int
foo  (unsigned long long a)
{
  return _mm_popcnt_u64 (a) =3D=3D 0;
}

basically anything that triggers a simplification of POPCOUNT as implemented
in match.pd (there are quite some).  But no, I don't think we have any
of those using the x86 intrinsics in the testsuite.=