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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/113186] New: [13/14 Regression] `(a^c) &
 (a^!c)` is not optimized to 0 for bool
Date: Sun, 31 Dec 2023 21:07:06 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
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=3D113186

            Bug ID: 113186
           Summary: [13/14 Regression] `(a^c) & (a^!c)` is not optimized
                    to 0 for bool
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
bool f(bool a, bool c)
{
  bool b =3D (a^c);
  bool d =3D (a^!c);
  return b & d;
}
```
This should optimize to 0 but does not since GCC 13. With the C++ front-end=
, I
suspect since r13-1779-g375668e0508fbe . With the C front-end, it started on
the trunk.

For C have in forwprop1:
  b_7 =3D a_5(D) ^ c_6(D);
  _11 =3D a_5(D) ^ c_6(D);
  _12 =3D a_5(D) =3D=3D c_6(D);
  _13 =3D b_7 & _12;

For C++ we have (at -O1):
  b_7 =3D a_5(D) !=3D c_6(D);
  _1 =3D ~c_6(D);
  d_8 =3D _1 !=3D a_5(D);
  _11 =3D b_7 & d_8;

For C++ at -O2 in forwprop2, we have similar as what with the C front-end.=