[Bug tree-optimization/121710] `a - b == nonzero` implies that `a != b` (a > b if nonzero was positive and signed type [also for pointers])

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121710

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|`a - b == nonzero` implies  |`a - b == nonzero` implies
                   |that `a != b`               |that `a != b` (a > b if
                   |                            |nonzero was positive and
                   |                            |signed type [also for
                   |                            |pointers])

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Even:
```
void link_error();
void f0(int a, int b, int *c)
{
  int t = b - a;
  if (t == 16)
  {
    if (b <= a)
    {
      link_error();
    }
  }
}
```

Should be optimized.