[Bug tree-optimization/110335] int converted to double should be considered non-nan and non-nan*non-nan is still non-nan

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110335

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another testcase:
```
  void
  h3(int to)
  {
    double dto = to;
    double damt = dto +2;
    if (damt != damt)
     __builtin_trap();
  }
```


Note we do optimize:
```
  void
  done(int to)
  {
    double dto = to;
    double damt = -dto;
    if (damt != damt)
     __builtin_trap();
  }
```
But via match and simplify.

Note there is tree_expr_maybe_nan_p and tree_expr_finite_p in fold-const.cc
Which can be used as a model for some frange related things too.