[Bug tree-optimization/109869] New: comparing SCHAR_MIN and SCHAR_MAX but with widden type could be optimized better

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109869

            Bug ID: 109869
           Summary: comparing SCHAR_MIN and SCHAR_MAX but with widden type
                    could be optimized better
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take (for most targets):
```
bool f1 (signed char i)
{
  unsigned long long _1 = i;
  bool _5 = _1 == 127;
  bool _6 = _1 == 18446744073709551488ull;
  return _5 | _6;
}
bool f2 (signed char i)
{
  return i == -128 || i == 127;
  __SIZE_TYPE__ _1 = i;
}
```

These two functions should produce the same code.

I noticed this while looking at PR 77899 .