tree-ssa-dom.c (thread_across_edge): Do not thread jumps if a PHI argument is…

tree-ssa-dom.c (thread_across_edge): Do not thread jumps if a PHI argument is set from a PHI_RESULT in the same...


	* tree-ssa-dom.c (thread_across_edge): Do not thread jumps if a
	PHI argument is set from a PHI_RESULT in the same block and the
	PHI argument is not the same as the PHI result.

Co-Authored-By: Kazu Hirata <kazu@cs.umass.edu>

From-SVN: r92102

gcc/ChangeLog

+2004-12-13  Jeff Law  <law@redhat.com>
+            Kazu Hirata  <kazu@cs.umass.edu>
+
+	* tree-ssa-dom.c (thread_across_edge): Do not thread jumps if a
+	PHI argument is set from a PHI_RESULT in the same block and the
+	PHI argument is not the same as the PHI result.
+
 2004-12-13  David Edelsohn  <edelsohn@gnu.org>
 
 	* xcoffout.c (xcoffout_declare_function): Always strip storage

gcc/tree-ssa-dom.c

@@ -550,6 +550,16 @@ thread_across_edge (struct dom_walk_data *walk_data, edge e)
     {
       tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
       tree dst = PHI_RESULT (phi);
+
+      /* If the desired argument is not the same as this PHI's result 
+	 and it is set by a PHI in this block, then we can not thread
+	 through this block.  */
+      if (src != dst
+	  && TREE_CODE (src) == SSA_NAME
+	  && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
+	  && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
+	return;
+
       record_const_or_copy (dst, src);
       register_new_def (dst, &block_defs_stack);
     }