[Bug tree-optimization/40321] [4.4/4.5 Regression] internal compiler error: in compute_antic, at tree-ssa-pre.c:2501

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2009-06-03 14:00 -------
The problem seems to be the asymmetry wrt handling of NAMEs vs. SSA_NAME
operands
in NARYs and REFERENCEs.  We happily translate NAMEs and do not clean them
if they are in AVAIL_OUT, but we only can translate SSA_NAME operands if they
have a leader in the set we are currently translating (wtf?) and we clean
the NARYs and REFERENCEs that do not have their SSA_NAME operands in ANTIC_IN
itself.

Huh.  Fixing both "fixes" the problem, but obviously results in larger ANTIC_IN
sets.

@@ -1466,13 +1499,15 @@ phi_translate_1 (pre_expr expr, bitmap_s
              {
                unsigned int op_val_id = VN_INFO (newnary.op[i])->value_id;
                pre_expr leader = find_leader_in_sets (op_val_id, set1, set2);
-               pre_expr result = phi_translate_1 (leader, set1, set2,
+               pre_expr result;
+               if (!leader)
+                 leader = get_or_alloc_expr_for_name (newnary.op[i]);
+               result = phi_translate_1 (leader, set1, set2,
                                                   pred, phiblock, seen);
                if (result && result != leader)
                  {
                    tree name = get_representative_for (result);
-                   if (!name)
-                     return NULL;
+                   gcc_assert (name != NULL_TREE);
                    newnary.op[i] = name;
                  }
                else if (!result)
@@ -1569,13 +1604,14 @@ phi_translate_1 (pre_expr expr, bitmap_s
              {
                unsigned int op_val_id = VN_INFO (op0)->value_id;
                leader = find_leader_in_sets (op_val_id, set1, set2);
+               if (!leader)
+                 leader = get_or_alloc_expr_for_name (op0);
                opresult = phi_translate_1 (leader, set1, set2,
                                            pred, phiblock, seen);
                if (opresult && opresult != leader)
                  {
                    tree name = get_representative_for (opresult);
-                   if (!name)
-                     break;
+                   gcc_assert (name != NULL_TREE);
                    op0 = name;
                  }
                else if (!opresult)
@@ -1587,13 +1623,14 @@ phi_translate_1 (pre_expr expr, bitmap_s
              {
                unsigned int op_val_id = VN_INFO (op1)->value_id;
                leader = find_leader_in_sets (op_val_id, set1, set2);
+               if (!leader)
+                 leader = get_or_alloc_expr_for_name (op1);
                opresult = phi_translate_1 (leader, set1, set2,
                                            pred, phiblock, seen);
                if (opresult && opresult != leader)
                  {
                    tree name = get_representative_for (opresult);
-                   if (!name)
-                     break;
+                   gcc_assert (name != NULL_TREE);
                    op1 = name;
                  }
                else if (!opresult)
@@ -1604,13 +1641,14 @@ phi_translate_1 (pre_expr expr, bitmap_s
              {
                unsigned int op_val_id = VN_INFO (op2)->value_id;
                leader = find_leader_in_sets (op_val_id, set1, set2);
+               if (!leader)
+                 leader = get_or_alloc_expr_for_name (op2);
                opresult = phi_translate_1 (leader, set1, set2,
                                            pred, phiblock, seen);
                if (opresult && opresult != leader)
                  {
                    tree name = get_representative_for (opresult);
-                   if (!name)
-                     break;
+                   gcc_assert (name != NULL_TREE);
                    op2 = name;
                  }
                else if (!opresult)
@@ -2091,7 +2129,7 @@ clean (bitmap_set_t set, basic_block blo

   for (i = 0; VEC_iterate (pre_expr, exprs, i, expr); i++)
     {
-      if (!valid_in_sets (set, NULL, expr, block))
+      if (!valid_in_sets (set, AVAIL_OUT (block), expr, block))
        bitmap_remove_from_set (set, expr);
     }
   VEC_free (pre_expr, heap, exprs);


the fix results in some ICEs because we cannot insert though.

A fix the other way around is be possible as well, but it doesn't fix the
problem:

Index: tree-ssa-pre.c
===================================================================
--- tree-ssa-pre.c      (revision 148119)
+++ tree-ssa-pre.c      (working copy)
@@ -1717,6 +1717,10 @@ phi_translate_1 (pre_expr expr, bitmap_s
        edge e;
        gimple def_stmt;
        tree name = PRE_EXPR_NAME (expr);
+       unsigned int name_val_id = VN_INFO (name)->value_id;
+       pre_expr leader = find_leader_in_sets (name_val_id, set1, set2);
+       if (!leader)
+         return NULL;

        def_stmt = SSA_NAME_DEF_STMT (name);
        if (gimple_code (def_stmt) == GIMPLE_PHI
@@ -2006,7 +2010,7 @@ valid_in_sets (bitmap_set_t set1, bitmap
   switch (expr->kind)
     {
     case NAME:
-      return bitmap_set_contains_expr (AVAIL_OUT (block), expr);
+      return union_contains_value (set1, set2, get_expr_value_id (expr));
     case NARY:
       {
        unsigned int i;


Note that what is odd is that during clean () we use ANTIC_IN to clean
expressions but we change it at the same time.  How are we sure that
clean (); clean () is a no-op?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40321