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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/109638] New: unsigned > 1 ? 0 : n is not
 optimized to n == 1
Date: Wed, 26 Apr 2023 21:00:31 +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: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
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=3D109638

            Bug ID: 109638
           Summary: unsigned > 1 ? 0 : n is not optimized to n =3D=3D 1
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
unsigned test_cst (unsigned n)
{
  if (n > 1)
    n =3D 0;
  return n;
}
unsigned test_cst1 (unsigned n)
{
  return (n =3D=3D 1);
}
```
For gimple at least the second one is smaller. I suspect for x86 the second
version is also faster because it uses sete rather than cmov.
But these 2 functions should produce the same code.

I found this on accident while looking at gcc.dg/tree-ssa/builtin-snprintf-=
2.c=20
testcase.

This can only be done for 1 too.=