[Bug target/58493] loop is not correctly optimized with O3 and AVX

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58493

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
C testcase

void omb(int n, double *points, double *weights)
{
  int i;
  for(i=0;i<n/2;i++)
    {
      points[2*i] = .7;
      weights[2*i]= 5.;

      points[2*i+1] = -.7;
      weights[2*i+1]=weights[2*i]; // mis-comiled
    }
}

int main()
{
  double p[18], w[18];
  int i;
  omb(18, p, w);
  for(i=0; i<18; ++i)
    __builtin_printf ("i=%d p=%f w=%f\n", i, p[i], w[i]);
  return 0;
}