diff -r ef8a98bc71f8 -r c4d9d1b08e2e src/hotspot/share/memory/universe.hpp
--- a/src/hotspot/share/memory/universe.hpp	Wed Jan 31 10:55:49 2018 -0800
+++ b/src/hotspot/share/memory/universe.hpp	Fri Sep 08 10:46:46 2017 -0700
@@ -141,6 +141,7 @@
   static oop          _system_thread_group;           // Reference to the system thread group object
 
   static objArrayOop  _the_empty_class_klass_array;   // Canonicalized obj array of type java.lang.Class
+  static oop          _the_null_sentinel;             // A unique object pointer unused except as a sentinel for null.
   static oop          _the_null_string;               // A cache of "null" as a Java string
   static oop          _the_min_jint_string;          // A cache of "-2147483648" as a Java string
   static LatestMethodCache* _finalizer_register_cache; // static method for registering finalizable objects
@@ -322,6 +323,9 @@
 
   static Method*      do_stack_walk_method()          { return _do_stack_walk_cache->get_method(); }
 
+  static oop          the_null_sentinel()             { return _the_null_sentinel;             }
+  static address      the_null_sentinel_addr()        { return (address) &_the_null_sentinel;  }
+
   // Function to initialize these
   static void initialize_known_methods(TRAPS);