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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/107880] New: bool tautology missed
 optimisation
Date: Sat, 26 Nov 2022 18:03:24 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia at gcc dot gnu.org
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107880

            Bug ID: 107880
           Summary: bool tautology missed optimisation
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

>From bug 91882 comment #1 (since the testcase in that was in bug 91882 comm=
ent
#0 is now fixed):

bool impl(bool a, bool b)
{
    return (!a || b);
}

// bad optimisation
bool always_true(bool a, bool b)
{
    return (impl(a,b) =3D=3D impl(b,a)) =3D=3D (a =3D=3D b);
           // ( (a -> b) =3D (b -> a) ) =3D (a =3D b) tautology
}=