[Bug tree-optimization/62217] Extra iteration peeled during cunroll. Makes VRP warn.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62217

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually it is a bad interaction between DOM and complete unrolling.
  <bb 20>:
  # i_14 = PHI <i_36(19)>
  if (i_14 == b_6(D))
    goto <bb 21>;
  else
    goto <bb 22>;

  <bb 21>:
  g_x[b_6(D)] = *x1_7(D);
  i_11 = i_14 + 1;
  goto <bb 3>;

  <bb 22>:
  __builtin_unreachable ();

--- CUT ---
Basic Block 21 should have been a __builtin_unreachable (); also.
BB21 was bb5 after dom.

BB5  was changed all the way back in dom to:
  <bb 5>:
  g_x[b_6(D)] = *x1_7(D);
  goto <bb 7>;


It was before DOM:
  <bb 5>:
  g_x[i_14] = *x2_9(D);