[Bug target/111655] wrong code generated for __builtin_signbit and 0./0. on x86-64 -O2

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111655

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another testcase which shows a related issue:
```
double t = 0.0/0.0;


  int
  main ()
  {
    double x = 0.0/0.0;
    return __builtin_signbit (x) != __builtin_signbit (t);
  }
```

And another one:
```
double t = 0.0/0.0;


  int
  main ()
  {
  //  double x = 0.0/0.0;
    volatile double tt = 0.0;

    return __builtin_signbit (tt/tt) != __builtin_signbit (t);
  }

```

Note GCC and clang even disagree on the first testcase but agree with the
second one.

I am thinking this is all under specified really ...