[Bug tree-optimization/65930] Reduction with sign-change not handled

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65930

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
Another case

unsigned bar (unsigned int *x)
{
  int sum = 0;
  for (int i = 0; i < 16; ++i)
    sum += x[i];
  return sum;
}

where an intermeditate result of the reduction chain is live.