re PR tree-optimization/56854 (error: non-decl/MEM_REF LHS in clobber statement)

	PR tree-optimization/56854
	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Don't
	forward into clobber stmts if it would change MEM_REF lhs into
	non-MEM_REF.

	* g++.dg/torture/pr56854.C: New test.

From-SVN: r197625

gcc/ChangeLog

+2013-04-09  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/56854
+	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Don't
+	forward into clobber stmts if it would change MEM_REF lhs into
+	non-MEM_REF.
+
 2013-04-09  Maxim Kuvyrkov  <maxim@kugelworks.com>
 
 	* tree.c (type_hash_lookup, type_hash_add): Make static.

gcc/testsuite/ChangeLog

+2013-04-09  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/56854
+	* g++.dg/torture/pr56854.C: New test.
+
 2013-04-08  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/56782

gcc/testsuite/g++.dg/torture/pr56854.C

+// PR tree-optimization/56854
+// { dg-do compile }
+
+inline void *
+operator new (__SIZE_TYPE__, void *p) throw ()
+{
+  return p;
+}
+
+struct A
+{
+  int a;
+  A () : a (0) {}
+  ~A () {}
+  A &operator= (const A &v) { this->~A (); new (this) A (v); return *this; }
+};
+A b[4], c[4];
+
+void
+foo ()
+{
+  for (int i = 0; i < 4; ++i)
+    c[i] = b[i];
+}

gcc/tree-ssa-forwprop.c

@@ -826,7 +826,11 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
 	       && integer_zerop (TREE_OPERAND (lhs, 1))
 	       && useless_type_conversion_p
 	            (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
-		     TREE_TYPE (gimple_assign_rhs1 (use_stmt))))
+		     TREE_TYPE (gimple_assign_rhs1 (use_stmt)))
+	       /* Don't forward anything into clobber stmts if it would result
+		  in the lhs no longer being a MEM_REF.  */
+	       && (!gimple_clobber_p (use_stmt)
+		   || TREE_CODE (TREE_OPERAND (def_rhs, 0)) == MEM_REF))
 	{
 	  tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
 	  tree new_offset, new_base, saved, new_lhs;