2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	PR middle-end/62103
	* gimple-fold.c (fold_ctor_reference): Don't fold in presence of
	bitfields, that is when size doesn't match the size of type or the
	size of the constructor.

	* gcc.c-torture/execute/bitfld-6.c: New test.

--- gcc/gimple-fold.c	(revision 213845)
+++ gcc/gimple-fold.c	(revision 213846)
@@ -4355,8 +4355,10 @@ fold_ctor_reference (tree type, tree cto
      result.  */
   if (!AGGREGATE_TYPE_P (TREE_TYPE (ctor)) && !offset
       /* VIEW_CONVERT_EXPR is defined only for matching sizes.  */
-      && operand_equal_p (TYPE_SIZE (type),
-			  TYPE_SIZE (TREE_TYPE (ctor)), 0))
+      && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
+      && TREE_CODE (TYPE_SIZE (TREE_TYPE (ctor))) == INTEGER_CST
+      && !compare_tree_int (TYPE_SIZE (type), size)
+      && !compare_tree_int (TYPE_SIZE (TREE_TYPE (ctor)), size))
     {
       ret = canonicalize_constructor_val (unshare_expr (ctor), from_decl);
       ret = fold_unary (VIEW_CONVERT_EXPR, type, ret);
--- gcc/testsuite/gcc.c-torture/execute/bitfld-6.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/execute/bitfld-6.c	(revision 213846)
@@ -0,0 +1,23 @@
+union U
+{
+  const int a;
+  unsigned b : 20;
+};
+
+static union U u = { 0x12345678 };
+
+/* Constant folding used to fail to account for endianness when folding a
+   union.  */
+
+int
+main (void)
+{
+#ifdef __BYTE_ORDER__
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  return u.b - 0x45678;
+#else
+  return u.b - 0x12345;
+#endif
+#endif
+  return 0;
+}