diff -r 338a117fb65c -r e8414c8ead61 src/hotspot/share/gc/shared/collectedHeap.hpp
--- a/src/hotspot/share/gc/shared/collectedHeap.hpp	Sun May 20 22:03:10 2018 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.hpp	Sun May 20 22:18:11 2018 +0200
@@ -598,6 +598,9 @@
   virtual oop pin_object(JavaThread* thread, oop obj);
   virtual void unpin_object(JavaThread* thread, oop obj);
 
+  // Deduplicate the string, iff the GC supports string deduplication.
+  virtual void deduplicate_string(oop str);
+
   virtual bool is_oop(oop object) const;
 
   // Non product verification and debugging.