[Bug tree-optimization/104917] No runtime alias test required for dependent reductions

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104917

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #1)
> What if x = y + 1 or y = x + 1 ?

We then do

  (y+1)[i] += a[i];
  (y+1)[i+1] += a[i+1];
  y[i] += a[i];
  y[i+1] += a[i+1];

instead of

  (y+1)[i] += a[i];
  y[i] += a[i];
  (y+1)[i+1] += a[i+1];
  y[i+1] += a[i+1];

which should be OK if re-associating the adds to y[i+1] is OK.