[Bug tree-optimization/94675] [9/10 regression] -Warray-bounds false positive with -O2 since r9-1948

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94675

--- Comment #9 from Jeffrey A. Law <law at redhat dot com> ---
Yea, unrolling and the array-bounds warning do have bad interactions.

I suspect if we cleaned up this block that the backwards threader would likely
kick in:

  # iftmp.2_18 = PHI <1(3), 1(4), 0(5)>
  _19 = (_Bool) iftmp.2_18;
  _2 = ~_19;
  _3 = (long int) _2;
  _4 = __builtin_expect (_3, 0);
  if (_4 == 0)
    goto <bb 7>; [INV]
  else
    goto <bb 8>; [INV]

I'll play with that and see if there's something we can do cleanly early enough
to matter.