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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/111431] New: a & (a == 0) is not optimized to
 0
Date: Sat, 16 Sep 2023 02:41:05 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization, xfail
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111431

            Bug ID: 111431
           Summary: a & (a =3D=3D 0) is not optimized to 0
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, xfail
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int
foo (int a)
{
  int b =3D !a;
  return (a & b);
}
```
The general rule is:
(a =3D=3D CST) & a
transform into:
(CST & 1) ? (a =3D=3D CST) : 0

So
(simplify
 (bit_and:c (convert@2 (eq @0 INTEGER_CST@1)) @0)
 (if ((wi::to_wide (@1) & 1) !=3D 0)
  @2
  { build_zero_cst (type); }))=