[Bug tree-optimization/77362] [6/7 Regression] [graphite] ICE in sese_build_liveouts_use w/ -O2 -floop-nest-optimize

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77362

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Problem is that original PHI node that we want to copy lives in a single loop:

  <bb 12>:
  _13 = f2_lsm.11_24 + 2;
  _59 = (unsigned short) f2_lsm.11_24;
  _20 = _59 + 2;
  _58 = (unsigned short) _20;
  _21 = (short int) _58;
  if (_21 >= 0)
    goto <bb 7>;
  else
    goto <bb 8>;

  <bb 7>:
  hm.8_8 = (unsigned short) _21;
  _9 = hm.8_8 + 1;
  _10 = (short int) _9;

  <bb 8>:
  # hm_lsm.13_12 = PHI <_21(12), _10(7)>
  k1_22 = k1_28 + 1;
  if (k1_22 != 2)
    goto <bb 9>;
  else
    goto <bb 10>;

So applying following patch would trigger that earlier:
diff --git a/gcc/graphite-isl-ast-to-gimple.c
b/gcc/graphite-isl-ast-to-gimple.c
index fb9c8468ebc..b3f72010507 100644
--- a/gcc/graphite-isl-ast-to-gimple.c
+++ b/gcc/graphite-isl-ast-to-gimple.c
@@ -1826,7 +1826,7 @@ get_loc (tree op)
 std::pair<edge, edge>
 get_edges (basic_block bb)
 {
-  std::pair<edge, edge> edges;
+  std::pair<edge, edge> edges (NULL, NULL);
   edge e;
   edge_iterator ei;
   FOR_EACH_EDGE (e, ei, bb->preds)
@@ -1834,14 +1834,17 @@ get_edges (basic_block bb)
       edges.first = e;
     else
       edges.second = e;
+
+  gcc_checking_assert (edges.first != NULL);
+  gcc_checking_assert (edges.second != NULL);
+
   return edges;
 }

As I've been reading the transformed loop nest, I don't know how to fix that
copied PHI.