Don't use a separate CLASSTYPE_AS_BASE if it's the same size.

	* class.c (layout_class_type): Don't use a separate
	CLASSTYPE_AS_BASE if it's the same size.

From-SVN: r272618

gcc/cp/ChangeLog

+2019-06-24  Jason Merrill  <jason@redhat.com>
+
+	* class.c (layout_class_type): Don't use a separate
+	CLASSTYPE_AS_BASE if it's the same size.
+
 2019-06-23  Marek Polacek  <polacek@redhat.com>
 
 	* call.c (convert_default_arg): Use DEFERRED_PARSE instead of

gcc/cp/class.c

@@ -6453,6 +6453,12 @@ layout_class_type (tree t, tree *virtuals_p)
   /* Let the back end lay out the type.  */
   finish_record_layout (rli, /*free_p=*/true);
 
+  /* If we didn't end up needing an as-base type, don't use it.  */
+  if (CLASSTYPE_AS_BASE (t) != t
+      && tree_int_cst_equal (TYPE_SIZE (t),
+			     TYPE_SIZE (CLASSTYPE_AS_BASE (t))))
+    CLASSTYPE_AS_BASE (t) = t;
+
   if (TYPE_SIZE_UNIT (t)
       && TREE_CODE (TYPE_SIZE_UNIT (t)) == INTEGER_CST
       && !TREE_OVERFLOW (TYPE_SIZE_UNIT (t))