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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/112383] New: `a&=CST; (a&b) != a` and `((~b) & a) &
 CST != 0`
Date: Sat, 04 Nov 2023 21:43:48 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
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=3D112383

            Bug ID: 112383
           Summary: `a&=3DCST; (a&b) !=3D a` and `((~b) & a) & CST !=3D 0`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int f1(unsigned a, unsigned b)
{
        a &=3D 0x11;
        return (a&b) !=3D a;
}


int f2(unsigned a, unsigned b)
{
        int d =3D 0x11;
        int e =3D (~b) & a;
        return (e&d) !=3D 0;
}
```

These 2 should produce the same code.

Likewise for:
```

int fn1(unsigned a, unsigned b, unsigned c)
{
        a &=3D c;
        return (a&b) !=3D a;
}


int fn2(unsigned a, unsigned b, unsigned c)
{
        int d =3D c;
        int e =3D (~b) & a;
        return (e&d) !=3D 0;
}
```

Note clang (LLVM) only produces the same code for f1/f2 pair, it misses the
Canonicalization for fn1/fn2 too.

Note for gimple f1/fn1 is simplier and most likely should be canonical.=