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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109885] gcc does not generate movmskps and
 testps instructions  (clang does)
Date: Sat, 10 Feb 2024 09:53:23 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia at gcc dot gnu.org
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Message-ID: <bug-109885-4-CQN7vBTEfM@http.gcc.gnu.org/bugzilla/>
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109885

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |tree-optimization
                 CC|                            |pinskia at gcc dot gnu.org
             Blocks|                            |53947

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What is even funnier on the LLVM side is if we have:
```
void f(unsigned int * __restrict a, unsigned int * __restrict b)
{
  unsigned int t =3D 0;
  t +=3D (a[0] =3D=3D b[0]);
  t +=3D (a[1] =3D=3D b[1])<<1;
  t +=3D (a[2] =3D=3D b[2])<<2;
  t +=3D (a[3] =3D=3D b[3])<<3;
  *a =3D t;
}
```
LLVM can produce movmskps for x86_64 but then does do a similar trick that =
it
did for the sum for aarch64.

Note GCC does not handle reductions that well for SLP either.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations=