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.
	(insert_debug_temps_for_defs): Handle PHI nodes.

Index: gcc/tree-ssa.c
===================================================================
--- gcc/tree-ssa.c.orig	2009-11-16 18:24:07.000000000 -0200
+++ gcc/tree-ssa.c	2009-11-16 18:41:04.000000000 -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)
@@ -346,7 +346,33 @@ 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)
+    {
+      bool no_value = false;
+      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;
+	    }
+	}
+
+      if (!no_value)
+	/* ??? 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))
     {
       bool no_value = false;
 
@@ -408,6 +434,7 @@ 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)))
@@ -478,6 +505,16 @@ insert_debug_temps_for_defs (gimple_stmt
 
   stmt = gsi_stmt (*gsi);
 
+  /* By the time we get here, the DEF in the PHI node seems to have
+     already been disconnected as an operand, so the FOR_EACH below
+     has no effect.  Handle it explicitly.  */
+  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);