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List:       gcc-bugs
Subject:    [Bug tree-optimization/94893] New: Sign function not getting optimized to simple compare
From:       "gabravier at gmail dot com" <gcc-bugzilla () gcc ! gnu ! org>
Date:       2020-04-30 17:31:16
Message-ID: bug-94893-4 () http ! gcc ! gnu ! org/bugzilla/
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94893

            Bug ID: 94893
           Summary: Sign function not getting optimized to simple compare
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

inline int sign(int x)
{
    return (x >> 31) | ((unsigned)-x >> 31);
}

bool f(int x)
{
    return sign(x) < 1;
}

With -O3, LLVM outputs :

f(int):
  test edi, edi
  setle al
  ret

GCC outputs :

f(int):
  mov eax, edi
  sar edi, 31
  neg eax
  shr eax, 31
  or eax, edi
  setle al
  ret=
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