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From: "zhiwuyazhe154 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/115474] New: Missed optimization: fold
 `std::max(a > b, a)` to `a` (bool a, bool b)
Date: Thu, 13 Jun 2024 10:47:31 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 15.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115474

            Bug ID: 115474
           Summary: Missed optimization: fold `std::max(a > b, a)` to `a`
                    (bool a, bool b)
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhiwuyazhe154 at gmail dot com
  Target Milestone: ---

godbolt example: https://godbolt.org/z/KG1fhaPvM

Code Example:
```
int func(bool a, bool b) {
    return std::max(a > b, a); // equals to a
}
```

In this case, when a =3D=3D 0, a > b =3D=3D 0(a); when a =3D=3D 1, a > b <=
=3D 1(a). So it can
be folded to a.

GCC -O3:
func(bool, bool):
        cmp     sil, dil
        setb    dl
        cmp     dl, dil
        setb    al
        or      eax, edx
        movzx   eax, al
        ret

Expected code(CLANG -O3):
func(bool, bool):=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20
        mov     eax, edi
        ret=