re PR tree-optimization/43213 (Worse code generated with -O2)

2010-03-01  Richard Guenther  <rguenther@suse.de>

	PR middle-end/43213
	* expr.c (expand_assignment): Use the alias-oracle to tell
	if the rhs aliases the result decl.

	* gcc.dg/pr43213.c: New testcase.

From-SVN: r157142

gcc/ChangeLog

+2010-03-01  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/43213
+	* expr.c (expand_assignment): Use the alias-oracle to tell
+	if the rhs aliases the result decl.
+
 2010-03-01  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	PR pch/14940

gcc/expr.c

@@ -4432,9 +4432,11 @@ expand_assignment (tree to, tree from, bool nontemporal)
   /* In case we are returning the contents of an object which overlaps
      the place the value is being stored, use a safe function when copying
      a value through a pointer into a structure value return block.  */
-  if (TREE_CODE (to) == RESULT_DECL && TREE_CODE (from) == INDIRECT_REF
+  if (TREE_CODE (to) == RESULT_DECL
+      && TREE_CODE (from) == INDIRECT_REF
       && ADDR_SPACE_GENERIC_P
-	  (TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (TREE_OPERAND (from, 0)))))
+	   (TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (TREE_OPERAND (from, 0)))))
+      && refs_may_alias_p (to, from)
       && cfun->returns_struct
       && !cfun->returns_pcc_struct)
     {

gcc/testsuite/ChangeLog

+2010-03-01  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/43213
+	* gcc.dg/pr43213.c: New testcase.
+
 2010-03-01  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* lib/target-supports.exp (check_effective_target_ucn_nocache):

gcc/testsuite/gcc.dg/pr43213.c

+/* { dg-do compile } */
+
+struct S {
+  int i;
+};
+
+struct S f(int i)
+{
+  return *(struct S *)&i;
+}
+
+/* { dg-final { scan-assembler-not "memmove" } } */