* tree-ssa-dom.c (record_equivalences_from_incoming_edge):

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-dom.c

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index c74dd5d..0ca36b0 100644 (file)
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -1450,9 +1450,12 @@ record_equivalences_from_incoming_edge (struct dom_walk_data *walk_data,
                                       &bd->avail_exprs,
                                       bb,
                                       &bd->vrp_variables);
-  /* Similarly when the parent block ended in a SWITCH_EXPR.  */
+  /* Similarly when the parent block ended in a SWITCH_EXPR.
+     We can only know the value of the switch's condition if the dominator
+     parent is also the only predecessor of this block.  */
   else if (parent_block_last_stmt
           && bb->pred->pred_next == NULL
+          && bb->pred->src == parent
           && TREE_CODE (parent_block_last_stmt) == SWITCH_EXPR)
     {
       tree switch_cond = SWITCH_COND (parent_block_last_stmt);
@@ -1473,7 +1476,7 @@ record_equivalences_from_incoming_edge (struct dom_walk_data *walk_data,
              tree elt = TREE_VEC_ELT (switch_vec, i);
              if (label_to_block (CASE_LABEL (elt)) == bb)
                {
-                 if (++case_count > 1)
+                 if (++case_count > 1 || CASE_HIGH (elt))
                    break;
                  match_case = elt;
                }
@@ -1484,6 +1487,7 @@ record_equivalences_from_incoming_edge (struct dom_walk_data *walk_data,
             the exact value of SWITCH_COND which caused us to get to
             this block.  Record that equivalence in EQ_EXPR_VALUE.  */
          if (case_count == 1
+             && match_case
              && CASE_LOW (match_case)
              && !CASE_HIGH (match_case))
            {