[Bug tree-optimization/122186] single_use is too much on some match patterns

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122186

--- Comment #5 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Another testcase for a different pattern:
```
void link_error();
int f0(int a, int b, int c)
{
  int t = b - a;
  if (t == 0)
  {
    if (a + 0 != b)
      link_error();
  }
  return t;
}
```