[Bug tree-optimization/61383] [4.8/4.9/4.10 Regression] wrong code at -O2 and -O3 on x86_64-linux-gnu

["glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61383

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
This very minor variant also misbehaves with 4.7 and 4.6, so before my patch.
An unsafe instruction (1%f) is taken out of a branch in ifcombine.

int a, b = 1, c, d, e, f, g;

int
fn1 ()
{
  int h;
  for (;;)
    {
      g = b;
      g = g ? 0 : 1 % g;
      e = a + 1;
      for (; d < 1; d = e)
        {
          if (f == 0)
            h = 0;
          else
            h = 1 % f;
          if (f < 1)
            c = 0;
          else if (h)
            break;
        }
      if (b)
        return 0;
    }
}

int
main ()
{
  fn1 ();
  return 0;
}