[Bug tree-optimization/69728] [6/7/8 Regression] internal compiler error: in outer_projection_mupa, at graphite-sese-to-poly.c:1175

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69728

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
A "simple" patch like the following seems to "work".

Index: gcc/graphite-sese-to-poly.c
===================================================================
--- gcc/graphite-sese-to-poly.c (revision 252920)
+++ gcc/graphite-sese-to-poly.c (working copy)
@@ -1043,6 +1043,13 @@ add_loop_schedule (__isl_take isl_schedu
   if (empty < 0 || empty)
     return empty < 0 ? isl_schedule_free (schedule) : schedule;

+  isl_union_set *domain = isl_schedule_get_domain (schedule);
+  if (isl_union_set_is_empty (domain))
+    {
+      isl_union_set_free (domain);
+      return schedule;
+    }
+
   isl_space *space = isl_set_get_space (iterators);
   int loop_index = isl_space_dim (space, isl_dim_set) - 1;

@@ -1063,7 +1070,6 @@ add_loop_schedule (__isl_take isl_schedu
   prefix = isl_multi_aff_set_tuple_id (prefix, isl_dim_out, label);

   int n = isl_multi_aff_dim (prefix, isl_dim_in);
-  isl_union_set *domain = isl_schedule_get_domain (schedule);
   isl_multi_union_pw_aff *mupa = outer_projection_mupa (domain, n);
   mupa = isl_multi_union_pw_aff_apply_multi_aff (mupa, prefix);
   return isl_schedule_insert_partial_schedule (schedule, mupa);


but it results in a bougs initial schedule:

[scheduler] original ast:
{
  for (int c0 = 0; c0 < -P_21; c0 += 1) {
    S_9(c0);
    if (P_21 + c0 <= -2)
      S_8(c0);
  }
  S_10();
}

so the conditional loop ended up not being a loop.  I believe in this
case we are somehow confused by 'c' wrapping?  niter is computed
as -(unsigned int) (c.7_21 + 1).  Can we really "handle" negating
an unsigned value?

static isl_pw_aff *
extract_affine (scop_p s, tree e, __isl_take isl_space *space)
{
..
    case NEGATE_EXPR:
    case BIT_NOT_EXPR:
      lhs = extract_affine (s, TREE_OPERAND (e, 0), isl_space_copy (space));
      rhs = extract_affine (s, integer_minus_one_node, space);
      res = isl_pw_aff_mul (lhs, rhs);
      break;

so we do x * -1 for negate -- that looks ok.  At least bogus for
BIT_NOT_EXPR which is really -1 - x, not x * -1.

Doesn't seem to handle any conversion to signed correctly either as it
misses an appropriate 'wrap' operation (the existing one only works
for unsigned).  The offset argument in POINTER_PLUS_EXPR handling needs
to be interpreted as signed.

So for the ICE I now have the hackish

Index: gcc/graphite-sese-to-poly.c
===================================================================
--- gcc/graphite-sese-to-poly.c (revision 252920)
+++ gcc/graphite-sese-to-poly.c (working copy)
@@ -1030,6 +1035,8 @@ outer_projection_mupa (__isl_take isl_un
   return isl_multi_union_pw_aff_from_union_pw_multi_aff (data.res);
 }

+static bool schedule_error;
+
 /* Embed SCHEDULE in the constraints of the LOOP domain.  */

 static isl_schedule *
@@ -1043,6 +1050,14 @@ add_loop_schedule (__isl_take isl_schedu
   if (empty < 0 || empty)
     return empty < 0 ? isl_schedule_free (schedule) : schedule;

+  isl_union_set *domain = isl_schedule_get_domain (schedule);
+  if (isl_union_set_is_empty (domain))
+    {
+      schedule_error = true;
+      isl_union_set_free (domain);
+      return schedule;
+    }
+
   isl_space *space = isl_set_get_space (iterators);
   int loop_index = isl_space_dim (space, isl_dim_set) - 1;

@@ -1169,6 +1183,8 @@ build_schedule_loop_nest (scop_p scop, i
 static bool
 build_original_schedule (scop_p scop)
 {
+  schedule_error = false;
+
   int i = 0;
   int n = scop->pbbs.length ();
   while (i < n)
@@ -1183,6 +1199,14 @@ build_original_schedule (scop_p scop)
       scop->original_schedule = add_in_sequence (scop->original_schedule, s);
     }

+  if (schedule_error)
+    {
+      if (dump_file)
+       fprintf (dump_file, "[sese-to-poly] failed to build "
+                "original schedule\n");
+      return false;
+    }
+
   if (dump_file)
     {
       fprintf (dump_file, "[sese-to-poly] original schedule:\n");