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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95852] New: Failure to optimize
 __builtin_mul_overflow pattern
Date: Tue, 23 Jun 2020 21:50:31 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95852

            Bug ID: 95852
           Summary: Failure to optimize __builtin_mul_overflow pattern
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

bool f(unsigned x, unsigned y, unsigned* res)
{
    *res =3D x * y;
    return x && ((*res / x) !=3D y);
}

This can be optimized to `return __builtin_mul_overflow(x, y, res);`. This
transformation is done by LLVM, but not by GCC.=