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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/108997] New: GCC prediction on bool
 comparisons seems wrong
Date: Thu, 02 Mar 2023 22:51:37 +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: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108997

            Bug ID: 108997
           Summary: GCC prediction on bool comparisons seems wrong
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

I noticed this while looking into 108992.
I suspect we look into this but I am not 100% sure this is a bug.
Testcase:
void use(int *);
void use2(int *);

void foo(bool cond, int * p)
{
    if (cond) {
        use(p);
    }
    use2(p);
}

GCC predicts the branch to be taken 66% of the time, but I would have assum=
e it
should be 50% as it is a bool and there is no other information. I suspect =
this
is due to prediction when comparing against 0.=