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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/100798] New: a?~t:t and (-(!!a))^t don't produce the
 same assembly code
Date: Thu, 27 May 2021 10:39:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100798

            Bug ID: 100798
           Summary: a?~t:t and (-(!!a))^t don't produce the same assembly
                    code
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

While working on non GCC code, I notice these two functions don't produce t=
he
assembly code:
int f(int a, int t)
{
  return (a=3D=3D's' ? ~t : t);
}

int f1(int a, int t)
{
  int t1 =3D -(a=3D=3D's');
  return (t1 ^ t);
}

For aarch64, the first case produce the best, while on x86_64, I don't know
which is better, sete or cmov.

Note LLVM produces the same code for both, for aarch64, the csinv and
sete/neg/xor for x86_64.=