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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/98891] [10/11 regression] Neon logical operations not
 vectorized in DImode since g:cdfc0e863a03698a80c74896cbdc9f5c8c652e64
Date: Wed, 17 Mar 2021 09:37:17 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98891

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |wilco at gcc dot gnu.org
   Last reconfirmed|                            |2021-03-17

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Reduced testcase:
extern unsigned long long a, b, c;

void
foo (void)
{
  a =3D b | ~c;
}

Seems this is the usual dilemma between split double-word operations early =
vs.
split it late, each has its advantages and serious disadvantages.
By splitting early, combiner can't really do much with it, it is split into
loads, not, or and store of the halves separately and combiner doesn't see =
the
two halves together, one would need essentially vectorization on RTL to mat=
ch
that.=