--- old/src/hotspot/share/runtime/thread.hpp	2019-03-11 14:27:22.878354094 +0100
+++ new/src/hotspot/share/runtime/thread.hpp	2019-03-11 14:27:22.666354097 +0100
@@ -443,6 +443,7 @@
     is_definitely_current_thread = true
   };
 
+ public:
   // Constructor
   Thread();
   virtual ~Thread() = 0;        // Thread is abstract.
@@ -981,6 +982,7 @@
   friend class VMStructs;
   friend class JVMCIVMStructs;
   friend class WhiteBox;
+  friend class VTBuffer;
  private:
   JavaThread*    _next;                          // The next thread in the Threads list
   bool           _on_thread_list;                // Is set when this JavaThread is added to the Threads list
@@ -1041,6 +1043,7 @@
   // Used to pass back results to the interpreter or generated code running Java code.
   oop           _vm_result;    // oop result is GC-preserved
   Metadata*     _vm_result_2;  // non-oop result
+  oop           _return_buffered_value; // buffered value being returned
 
   // See ReduceInitialCardMarks: this holds the precise space interval of
   // the most recent slow path allocation for which compiled code has
@@ -1529,6 +1532,9 @@
   Metadata*    vm_result_2() const               { return _vm_result_2; }
   void set_vm_result_2  (Metadata* x)          { _vm_result_2   = x; }
 
+  oop return_buffered_value() const              { return _return_buffered_value; }
+  void set_return_buffered_value(oop val)        { _return_buffered_value = val; }
+
   MemRegion deferred_card_mark() const           { return _deferred_card_mark; }
   void set_deferred_card_mark(MemRegion mr)      { _deferred_card_mark = mr;   }
 
@@ -1771,6 +1777,7 @@
   static ByteSize callee_target_offset()         { return byte_offset_of(JavaThread, _callee_target); }
   static ByteSize vm_result_offset()             { return byte_offset_of(JavaThread, _vm_result); }
   static ByteSize vm_result_2_offset()           { return byte_offset_of(JavaThread, _vm_result_2); }
+  static ByteSize return_buffered_value_offset() { return byte_offset_of(JavaThread, _return_buffered_value); }
   static ByteSize thread_state_offset()          { return byte_offset_of(JavaThread, _thread_state); }
   static ByteSize saved_exception_pc_offset()    { return byte_offset_of(JavaThread, _saved_exception_pc); }
   static ByteSize osthread_offset()              { return byte_offset_of(JavaThread, _osthread); }