[Bug tree-optimization/83255] [8 Regression] [graphite] Wrong code w/ -O1 -floop-nest-optimize

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83255

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, finally a testcase for a fix I have in my tree ;)

It would probably help if we'd emit the loop niters as SSA names instead of
creating weird constraints from them like

[sese-to-poly] adding one extra dimension to the domain for loop_1.
[sese-to-poly] adding constraint to the domain: [P_25] -> { [i1] : i1 >= 0 }
[sese-to-poly] adding constraint to the domain: [P_25] -> { [i1] :
4294967296*floor((-P_25)/4294967296) <= -P_25 - i1 }
Analyzing # of iterations of loop 1
  exit condition [l4.8_25 + 1, + , 1](no_overflow) <= 0
  bounds on difference of bases: -1 ... 2147483647
  result:
    # of iterations -(unsigned int) l4.8_25, bounded by 2147483648

...

[scheduler] original ast:
for (int c0 = 0; c0 <= -P_25; c0 += 1)
  for (int c1 = 0; c1 <= 2; c1 += 1) {
    for (int c2 = 0; c2 <= 2; c2 += 1)
      S_5(c0, c1, c2);
    S_25(c0, c1);
  }