- Create isolate specific resuable handles and use them in the hot lookup paths.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
===================================================================
--- runtime/vm/isolate.cc	(revision 24200)
+++ runtime/vm/isolate.cc	(working copy)
@@ -371,6 +371,9 @@
 }
 
 
+#define REUSABLE_HANDLE_INITIALIZERS(object)                                   \
+  object##_handle_(NULL),
+
 Isolate::Isolate()
     : store_buffer_(),
       message_notify_callback_(NULL),
@@ -409,11 +412,14 @@
       deferred_objects_(NULL),
       stacktrace_(NULL),
       stack_frame_index_(-1),
-      object_histogram_(NULL) {
+      object_histogram_(NULL),
+      REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
+      handles_() {
   if (FLAG_print_object_histogram && (Dart::vm_isolate() != NULL)) {
     object_histogram_ = new ObjectHistogram(this);
   }
 }
+#undef REUSABLE_HANDLE_INITIALIZERS
 
 
 Isolate::~Isolate() {
@@ -461,6 +467,13 @@
   // the current isolate.
   SetCurrent(result);
 
+  // Setup the isolate specific resuable handles.
+#define REUSABLE_HANDLE_ALLOCATION(object)                                     \
+  result->object##_handle_ = result->AllocateReusableHandle<object>();         \
+
+  REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_ALLOCATION)
+#undef REUSABLE_HANDLE_ALLOCATION
+
   // Setup the isolate message handler.
   MessageHandler* handler = new IsolateMessageHandler(result);
   ASSERT(handler != NULL);
@@ -825,6 +838,9 @@
   // Visit objects in zones.
   current_zone()->VisitObjectPointers(visitor);
 
+  // Visit objects in isolate specific handles area.
+  handles_.VisitObjectPointers(visitor);
+
   // Iterate over all the stack frames and visit objects on the stack.
   StackFrameIterator frames_iterator(validate_frames);
   StackFrame* frame = frames_iterator.NextFrame();
@@ -1050,6 +1066,14 @@
 }
 
 
+template<class T>
+T* Isolate::AllocateReusableHandle() {
+  T* handle = reinterpret_cast<T*>(handles_.AllocateScopedHandle());
+  T::initializeHandle(handle, T::null());
+  return handle;
+}
+
+
 static void FillDeferredSlots(DeferredSlot** slot_list) {
   DeferredSlot* slot = *slot_list;
   *slot_list = NULL;