src/share/vm/memory/iterator.hpp

rev 7183 : autospecialized oop_iterate using SFINAE and templates

@@ -45,10 +45,15 @@
  public:
   virtual void do_oop(oop* o) = 0;
   virtual void do_oop_v(oop* o) { do_oop(o); }
   virtual void do_oop(narrowOop* o) = 0;
   virtual void do_oop_v(narrowOop* o) { do_oop(o); }
+
+  // Use SFINAE to dispatch to the "most appropriate" do_oop using OopClosureDispatcher.
+  // Read the specialized_oop_closures.hpp file how this works
+  template<class OopClosureType, class OopType>
+  void do_oop_auto(OopType* o);
 };
 
 // ExtendedOopClosure adds extra code to be run during oop iterations.
 // This is needed by the GC and is extracted to a separate type to not
 // pollute the OopClosure interface.

@@ -74,23 +79,47 @@
   // Currently, only CMS and G1 need these.
 
   virtual bool do_metadata() { return do_metadata_nv(); }
   bool do_metadata_v()       { return do_metadata(); }
   bool do_metadata_nv()      { return false; }
+  // Use SFINAE to dispatch to the "most appropriate" do_metadata using OopClosureDispatcher.
+  // Read the specialized_oop_closures.hpp file how this works
+  template<class OopClosureType>
+  bool do_metadata_auto();
 
   virtual void do_klass(Klass* k)   { do_klass_nv(k); }
   void do_klass_v(Klass* k)         { do_klass(k); }
   void do_klass_nv(Klass* k)        { ShouldNotReachHere(); }
+  // Use SFINAE to dispatch to the "most appropriate" do_klass using OopClosureDispatcher.
+  // Read the specialized_oop_closures.hpp file how this works
+  template<class OopClosureType>
+  void do_klass_auto(Klass* klass);
 
   virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
+  // Use SFINAE to dispatch to the "most appropriate" do_class_loader_data using OopClosureDispatcher.
+  // Read the specialized_oop_closures.hpp file how this works
+  template<class OopClosureType>
+  void do_class_loader_data_auto(ClassLoaderData* cld);
 
   // True iff this closure may be safely applied more than once to an oop
   // location without an intervening "major reset" (like the end of a GC).
   virtual bool idempotent() { return false; }
   virtual bool apply_to_weak_ref_discovered_field() { return false; }
 };
 
+// Autospecialization uses an OopClosure rather than ExtendedOopClosure
+// for oop_iterate_no_header to make sure metadata methods are not called
+// in the first place using SFINAE type checks
+template<class OopClosureType>
+class NoHeaderOopClosure : public OopClosure {
+  OopClosureType* _cl;
+ public:
+  NoHeaderOopClosure(OopClosureType *cl) : _cl(cl) {}
+  void do_oop(oop *p)       { _cl->template do_oop_auto<OopClosureType, oop>(p); }
+  void do_oop(narrowOop *p) { _cl->template do_oop_auto<OopClosureType, narrowOop>(p); }
+};
+
 // Wrapper closure only used to implement oop_iterate_no_header().
 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
   OopClosure* _wrapped_closure;
  public:
   NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}