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From: "lh_mouse at 126 dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108847] New: unnecessary bitwise AND on boolean
 types
Date: Sun, 19 Feb 2023 13:37:50 +0000
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X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108847

            Bug ID: 108847
           Summary: unnecessary bitwise AND on boolean types
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lh_mouse at 126 dot com
  Target Milestone: ---

Godbolt: https://gcc.godbolt.org/z/fsavMzMo7

```
void
set_bool(bool& fl, __UINT32_TYPE__ value)
  {
    fl |=3D value >> 31;
  }
```

This code shifts a `uint32` to the right by 31 bits, so the result will onl=
y be
0 or 1.

Clang outputs:

```
set_bool(bool&, unsigned int):                         # @set_bool(bool&,
unsigned int)
        shr     esi, 31
        or      byte ptr [rdi], sil
        ret
```

but GCC emits an additional unnecessary bitwise AND operation on the
destination operand:

```
set_bool(bool&, unsigned int):
        shr     esi, 31
        or      BYTE PTR [rdi], sil
        and     BYTE PTR [rdi], 1
        ret
```=