[Bug rtl-optimization/123312] New: [16 Regression] `c ? a & b : a` has extra instructions after ifcvt changes

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123312

            Bug ID: 123312
           Summary: [16 Regression] `c ? a & b : a` has extra instructions
                    after ifcvt changes
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64 x86_64

For:
```
int f(int a, int b, int c)
{
  if (c) a &= b;
  return a;
}
```

We now get:
```
f:
        xorl    %eax, %eax
        testl   %edx, %edx
        cmove   %edi, %eax
        andl    %esi, %edi
        orl     %edi, %eax
        ret
```

While we used to get:
```
f:
        andl    %edi, %esi
        movl    %edi, %eax
        testl   %edx, %edx
        cmovne  %esi, %eax
        ret
```

Notice how there is and andl and orl while before we just had an andl.

Though maybe we should get:
```
        testl   %edx, %edx
        movl    $-1, %eax
        cmovne  %esi, %eax
        andl    %edi, %eax
        ret
```

That is:
b = c ? b : -1;
return a & b;