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From: "xxs_chy at outlook dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114702] New: Missed optimization: fail to
 infer c - b != if a + b != c
Date: Fri, 12 Apr 2024 13:50:52 +0000
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X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114702

            Bug ID: 114702
           Summary: Missed optimization: fail to infer c - b !=3D if a + b
                    !=3D c
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xxs_chy at outlook dot com
  Target Milestone: ---

Godbolt link: https://godbolt.org/z/58rxGaabW

```
void src(int a, int b){
    if(b + a =3D=3D 32){
        return;
    }else{
        if(32 - b =3D=3D a)
            dummy();
        else
            dummy1();
    }
}
```

Obviously, "32 - b =3D=3D a" is false. We can get:

```
void tgt(int a, int b){
    if(b + a =3D=3D 32){
        return;
    }else{
        dummy1();
    }
}
```


This is a real-world dead code after inlining functions in QEMU.=