--- old/src/share/vm/oops/constMethod.hpp	2016-12-02 14:22:06.091886122 +0100
+++ new/src/share/vm/oops/constMethod.hpp	2016-12-02 14:22:05.619886107 +0100
@@ -129,10 +129,10 @@
 class ValueFactoryParameterMappingElement VALUE_OBJ_CLASS_SPEC{
 public:
   union data_t {
-    u4 field_index;
+    u4 field_index;   // VM-internal field index as returned by fieldDescriptor::index()
     struct temp_t {
-      u2 arg_index;
-      u2 field_index;
+      u2 arg_index;   // Index of argument in the attached factory method
+      u2 field_index; // Index in the class file's constant pool
     } temp;
   } data;
 };