--- a/src/hotspot/share/gc/g1/g1OopClosures.hpp	Wed Sep 12 09:12:42 2018 +0100
+++ b/src/hotspot/share/gc/g1/g1OopClosures.hpp	Wed Sep 12 11:08:42 2018 +0200
@@ -54,8 +54,8 @@
   template <class T>
   inline void handle_non_cset_obj_common(InCSetState const state, T* p, oop const obj);
 public:
-  // This closure needs special handling for InstanceRefKlass.
-  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERED_AND_DISCOVERY; }
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
+
   void set_region(HeapRegion* from) { _from = from; }
 
   inline void trim_queue_partially();
@@ -98,6 +98,9 @@
   virtual void do_oop(oop* p)          { do_oop_work(p); }
   virtual void do_oop(narrowOop* p)    { do_oop_work(p); }
 
+  // We need to do reference discovery while processing evacuated objects.
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERED_AND_DISCOVERY; }
+
   void set_ref_discoverer(ReferenceDiscoverer* rd) {
     set_ref_discoverer_internal(rd);
   }
@@ -201,8 +204,7 @@
     _worker_i(worker_i) {
   }
 
-  // This closure needs special handling for InstanceRefKlass.
-  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERED_AND_DISCOVERY; }
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
 
   template <class T> void do_oop_work(T* p);
   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
@@ -219,8 +221,8 @@
   template <class T> void do_oop_work(T* p);
   virtual void do_oop(oop* p)       { do_oop_work(p); }
   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
-  // This closure needs special handling for InstanceRefKlass.
-  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERED_AND_DISCOVERY; }
+
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
 };
 
 #endif // SHARE_VM_GC_G1_G1OOPCLOSURES_HPP

--- a/src/hotspot/share/oops/instanceRefKlass.inline.hpp	Wed Sep 12 09:12:42 2018 +0100
+++ b/src/hotspot/share/oops/instanceRefKlass.inline.hpp	Wed Sep 12 11:08:42 2018 +0200
@@ -98,12 +98,14 @@
 
 template <typename T, class OopClosureType, class Contains>
 void InstanceRefKlass::oop_oop_iterate_fields(oop obj, OopClosureType* closure, Contains& contains) {
+  assert(closure->ref_discoverer() == NULL, "ReferenceDiscoverer should not be set");
   do_referent<T>(obj, closure, contains);
   do_discovered<T>(obj, closure, contains);
 }
 
 template <typename T, class OopClosureType, class Contains>
 void InstanceRefKlass::oop_oop_iterate_fields_except_referent(oop obj, OopClosureType* closure, Contains& contains) {
+  assert(closure->ref_discoverer() == NULL, "ReferenceDiscoverer should not be set");
   do_discovered<T>(obj, closure, contains);
 }