diff -r c036b84c6bbf -r 758deedaae84 src/hotspot/share/gc/g1/g1CollectedHeap.cpp
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Wed May 09 11:24:12 2018 +0200
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Wed May 09 13:37:05 2018 +0200
@@ -3791,7 +3791,6 @@
 
   // Executes the given task using concurrent marking worker threads.
   virtual void execute(ProcessTask& task);
-  virtual void execute(EnqueueTask& task);
 };
 
 // Gang task for possibly parallel reference processing
@@ -3856,35 +3855,6 @@
   _workers->run_task(&proc_task_proxy);
 }
 
-// Gang task for parallel reference enqueueing.
-
-class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
-  typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
-  EnqueueTask& _enq_task;
-
-public:
-  G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
-    AbstractGangTask("Enqueue reference objects in parallel"),
-    _enq_task(enq_task)
-  { }
-
-  virtual void work(uint worker_id) {
-    _enq_task.work(worker_id);
-  }
-};
-
-// Driver routine for parallel reference enqueueing.
-// Creates an instance of the ref enqueueing gang
-// task and has the worker threads execute it.
-
-void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
-  assert(_workers != NULL, "Need parallel worker threads.");
-
-  G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
-
-  _workers->run_task(&enq_task_proxy);
-}
-
 // End of weak reference support closures
 
 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {