tree-ssa-operands.c (swap_tree_operands): Always adjust existing operand positions.

2011-09-09  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-operands.c (swap_tree_operands): Always adjust
	existing operand positions.

From-SVN: r178723

gcc/ChangeLog

 2011-09-09  Richard Guenther  <rguenther@suse.de>
 
+	* tree-ssa-operands.c (swap_tree_operands): Always adjust
+	existing operand positions.
+
+2011-09-09  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/50333
 	* tree-data-ref.c (split_constant_offset): Do not try to handle
 	ternary ops.

gcc/tree-ssa-operands.c

@@ -1149,7 +1149,8 @@ swap_tree_operands (gimple stmt, tree *exp0, tree *exp1)
 
   /* If the operand cache is active, attempt to preserve the relative
      positions of these two operands in their respective immediate use
-     lists.  */
+     lists by adjusting their use pointer to point to the new
+     operand position.  */
   if (ssa_operands_active () && op0 != op1)
     {
       use_optype_p use0, use1, ptr;
@@ -1170,14 +1171,12 @@ swap_tree_operands (gimple stmt, tree *exp0, tree *exp1)
 	    break;
 	  }
 
-      /* If both uses don't have operand entries, there isn't much we can do
-         at this point.  Presumably we don't need to worry about it.  */
-      if (use0 && use1)
-        {
-	  tree *tmp = USE_OP_PTR (use1)->use;
-	  USE_OP_PTR (use1)->use = USE_OP_PTR (use0)->use;
-	  USE_OP_PTR (use0)->use = tmp;
-	}
+      /* And adjust their location to point to the new position of the
+         operand.  */
+      if (use0)
+	USE_OP_PTR (use0)->use = exp1;
+      if (use1)
+	USE_OP_PTR (use1)->use = exp0;
     }
 
   /* Now swap the data.  */