8220610: Make CollectedHeap nmethod functions pure virtual

Reviewed-by: shade

src/hotspot/share/gc/epsilon/epsilonHeap.hpp

@@ -129,6 +129,12 @@ public:
   virtual void print_gc_threads_on(outputStream* st) const {}
   virtual void gc_threads_do(ThreadClosure* tc) const {}
 
+  // No nmethod handling
+  virtual void register_nmethod(nmethod* nm) {}
+  virtual void unregister_nmethod(nmethod* nm) {}
+  virtual void flush_nmethod(nmethod* nm) {}
+  virtual void verify_nmethod(nmethod* nm) {}
+
   // No heap verification
   virtual void prepare_for_verify() {}
   virtual void verify(VerifyOption option) {}

src/hotspot/share/gc/g1/g1CollectedHeap.hpp

@@ -1322,6 +1322,12 @@ public:
   // Unregister the given nmethod from the G1 heap.
   virtual void unregister_nmethod(nmethod* nm);
 
+  // No nmethod flushing needed.
+  virtual void flush_nmethod(nmethod* nm) {}
+
+  // No nmethod verification implemented.
+  virtual void verify_nmethod(nmethod* nm) {}
+
   // Free up superfluous code root memory.
   void purge_code_root_memory();
 

src/hotspot/share/gc/shared/collectedHeap.hpp

@@ -510,11 +510,11 @@ class CollectedHeap : public CHeapObj<mtInternal> {
   void print_heap_after_gc();
 
   // Registering and unregistering an nmethod (compiled code) with the heap.
-  // Override with specific mechanism for each specialized heap type.
-  virtual void register_nmethod(nmethod* nm) {}
-  virtual void unregister_nmethod(nmethod* nm) {}
-  virtual void flush_nmethod(nmethod* nm) {}
-  virtual void verify_nmethod(nmethod* nmethod) {}
+  virtual void register_nmethod(nmethod* nm) = 0;
+  virtual void unregister_nmethod(nmethod* nm) = 0;
+  // Callback for when nmethod is about to be deleted.
+  virtual void flush_nmethod(nmethod* nm) = 0;
+  virtual void verify_nmethod(nmethod* nm) = 0;
 
   void trace_heap_before_gc(const GCTracer* gc_tracer);
   void trace_heap_after_gc(const GCTracer* gc_tracer);

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -584,6 +584,8 @@ public:
 public:
   void register_nmethod(nmethod* nm);
   void unregister_nmethod(nmethod* nm);
+  void flush_nmethod(nmethod* nm) {}
+  void verify_nmethod(nmethod* nm) {}
 
 // ---------- Pinning hooks
 //