[Bug tree-optimization/128516] New: `x unorder CST` should be optimized to `x unorder x`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128516

            Bug ID: 128516
           Summary: `x unorder CST` should be optimized to `x unorder x`
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int f(double x)
{
  return __builtin_isunordered(x, 1.0);
}
```

This should be simplified into:
```
int f(double x)
{
  return __builtin_isunordered(x, x);
}
```

At least for the non-trapping math case; I think for the trapping case too.