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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/113176] New: `(n / 4) ? n / 4 : 0` is not
 optimized to just `n /4`
Date: Sat, 30 Dec 2023 04:29:37 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
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=3D113176

            Bug ID: 113176
           Summary: `(n / 4) ? n / 4 : 0` is not optimized to just `n /4`
           Product: gcc
           Version: 14.0
            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:
```
int unopt(int n) {
    if (n / 4)
        return n / 4;
    else
        return 0;
}

int unopt1(int n) {
    return (n / 4) ? n / 4 : 0;
}

int opt(int n) {
    return n / 4;
}
```

I would have expected unopt be transformed into opt but currently it is not.

This is because GCC decides to transform `(n / 4) !=3D 0` into `(unsigned i=
nt) n
+ 3 > 6`.=