[backport from gcc-4.7/trunk <mikpe@it.uu.se>]

gcc/

2011-03-17  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48134
	* tree-ssa.c (insert_debug_temp_for_var_def): If we propagated
	a value make sure to fold the statement.

gcc/testsuite/

2011-03-17  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48134
	* gcc.dg/pr48134.c: New testcase.

--- gcc-4.6-20110318/gcc/testsuite/gcc.dg/pr48134.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6-20110318/gcc/testsuite/gcc.dg/pr48134.c	2011-03-21 15:33:36.000000000 +0100
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-check=specific -fno-tree-dse -fno-tree-fre -fno-tree-loop-optimize -g" } */
+
+struct S
+{
+  int w, z;
+};
+struct T
+{
+  struct S s;
+};
+
+int i;
+
+static inline struct S
+bar (struct S x)
+{
+  i++;
+  return x;
+}
+
+int
+foo (struct T t, struct S s)
+{
+  struct S *c = &s;
+  if (i)
+    c = &t.s;
+  t.s.w = 3;
+  s = bar (*c);
+  return t.s.w;
+}
--- gcc-4.6-20110318/gcc/tree-ssa.c.~1~	2011-02-15 19:36:31.000000000 +0100
+++ gcc-4.6-20110318/gcc/tree-ssa.c	2011-03-21 15:33:36.000000000 +0100
@@ -455,13 +455,19 @@ insert_debug_temp_for_var_def (gimple_st
 	continue;
 
       if (value)
-	FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
-	  /* unshare_expr is not needed here.  vexpr is either a
-	     SINGLE_RHS, that can be safely shared, some other RHS
-	     that was unshared when we found it had a single debug
-	     use, or a DEBUG_EXPR_DECL, that can be safely
-	     shared.  */
-	  SET_USE (use_p, value);
+	{
+	  FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
+	    /* unshare_expr is not needed here.  vexpr is either a
+	       SINGLE_RHS, that can be safely shared, some other RHS
+	       that was unshared when we found it had a single debug
+	       use, or a DEBUG_EXPR_DECL, that can be safely
+	       shared.  */
+	    SET_USE (use_p, value);
+	  /* If we didn't replace uses with a debug decl fold the
+	     resulting expression.  Otherwise we end up with invalid IL.  */
+	  if (TREE_CODE (value) != DEBUG_EXPR_DECL)
+	    fold_stmt_inplace (stmt);
+	}
       else
 	gimple_debug_bind_reset_value (stmt);