[Bug tree-optimization/70138] [6 Regression] wrong code at -O3 on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70138

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Simpler testcase not requiring strided stores:

double u[33];

__attribute__((noinline, noclone)) static void
foo (int *x)
{
  double c = 0.0;
  int a, b;
  for (a = 0; a < 33; a++)
    {
      for (b = 0; b < 33; b++)
        c = c + u[a];
      u[a] *= 2.0;
    }
  *x = c;
}

int
main ()
{
  int d, e;
  for (d = 0; d < 33; d++)
    {
      u[d] = (d + 2);
      __asm__ volatile ("" : : : "memory");
    }
  foo (&e);
  if (e != 33 * (2 + 34) / 2 * 33)
    __builtin_abort ();
  return 0;
}


fails to vectorize on the gcc-5-branch because it can't create an epilogue
there.