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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/95408] New: Failure to optimize bitwise and
 with negated conditional using the same operand to conditional with
 decremented operand
Date: Fri, 29 May 2020 09:40:02 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: gabravier at gmail dot com
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95408

            Bug ID: 95408
           Summary: Failure to optimize bitwise and with negated
                    conditional using the same operand to conditional with
                    decremented operand
           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(int x)
{
    return x & -((unsigned)x < some_constant);
}

This can be optimized to `return (unsigned)(x - 1) < (some_constant - 1);`.
This transformation is done by LLVM, but not by GCC.=