for  gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* tree-ssa.c (find_released_ssa_name): Handle NULL wi.
	(insert_debug_temp_for_var_def): Handle degenerate PHI nodes.
	Fix handling of released SSA names.
	(insert_debug_temps_for_defs): Handle PHI nodes.

Index: gcc/tree-ssa.c
===================================================================
--- gcc/tree-ssa.c.orig	2009-11-08 05:09:36.000000000 -0200
+++ gcc/tree-ssa.c	2009-11-08 05:34:12.000000000 -0200
@@ -279,7 +279,7 @@ find_released_ssa_name (tree *tp, int *w
 {
   struct walk_stmt_info *wi = (struct walk_stmt_info *) data_;
 
-  if (wi->is_lhs)
+  if (wi && wi->is_lhs)
     return NULL_TREE;
 
   if (TREE_CODE (*tp) == SSA_NAME)
@@ -346,11 +346,30 @@ insert_debug_temp_for_var_def (gimple_st
   /* If we didn't get an insertion point, and the stmt has already
      been removed, we won't be able to insert the debug bind stmt, so
      we'll have to drop debug information.  */
-  if (is_gimple_assign (def_stmt))
+  if (gimple_code (def_stmt) == GIMPLE_PHI || is_gimple_assign (def_stmt))
     {
       bool no_value = false;
 
-      if (!dom_info_available_p (CDI_DOMINATORS))
+      if (gimple_code (def_stmt) == GIMPLE_PHI)
+	{
+	  struct walk_stmt_info wi;
+	  size_t i;
+
+	  memset (&wi, 0, sizeof (wi));
+
+	  for (i = 0; i < gimple_phi_num_args (def_stmt); i++)
+	    {
+	      tree *argp = gimple_phi_arg_def_ptr (def_stmt, i);
+
+	      if (!*argp
+		  || walk_tree (argp, find_released_ssa_name, NULL, NULL))
+		{
+		  no_value = true;
+		  break;
+		}
+	    }
+	}
+      else if (!dom_info_available_p (CDI_DOMINATORS))
 	{
 	  struct walk_stmt_info wi;
 
@@ -383,13 +402,22 @@ insert_debug_temp_for_var_def (gimple_st
 	     dead SSA NAMEs.  SSA verification shall catch any
 	     errors.  */
 	  if ((!gsi && !gimple_bb (def_stmt))
-	      || !walk_gimple_op (def_stmt, find_released_ssa_name,
-				  &wi))
+	      || walk_gimple_op (def_stmt, find_released_ssa_name, &wi))
 	    no_value = true;
 	}
 
       if (!no_value)
-	value = gimple_assign_rhs_to_tree (def_stmt);
+	{
+	  if (gimple_code (def_stmt) == GIMPLE_PHI)
+	    /* ??? We could handle at least some non-generate PHI
+	       nodes by inserting debug temps on every edge.  It's
+	       not clear how much this would improve debug info.  */
+	    value = degenerate_phi_result (def_stmt);
+	  else if (is_gimple_assign (def_stmt))
+	    value = gimple_assign_rhs_to_tree (def_stmt);
+	  else
+	    gcc_unreachable ();
+	}
     }
 
   if (value)
@@ -409,6 +437,7 @@ insert_debug_temp_for_var_def (gimple_st
 	 at the expense of duplication of expressions.  */
 
       if (CONSTANT_CLASS_P (value)
+	  || gimple_code (def_stmt) == GIMPLE_PHI
 	  || (usecount == 1
 	      && (!gimple_assign_single_p (def_stmt)
 		  || is_gimple_min_invariant (value)))
@@ -479,6 +508,13 @@ insert_debug_temps_for_defs (gimple_stmt
 
   stmt = gsi_stmt (*gsi);
 
+  if (gimple_code (stmt) == GIMPLE_PHI)
+    {
+      tree var = gimple_phi_result (stmt);
+      insert_debug_temp_for_var_def (gsi, var);
+      return;
+    }
+
   FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, op_iter, SSA_OP_DEF)
     {
       tree var = DEF_FROM_PTR (def_p);