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

runtime/vm/handles.h

Index: runtime/vm/handles.h
===================================================================
--- runtime/vm/handles.h	(revision 24061)
+++ runtime/vm/handles.h	(working copy)
@@ -228,6 +228,7 @@
   friend class HandleScope;
   friend class Dart;
   friend class ObjectStore;
+  friend class Isolate;
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Handles);
 };
@@ -338,9 +339,48 @@
 #endif  // defined(DEBUG)
 
 // Macro to start a no handles scope in the code.
-#define NOHANDLESCOPE(isolate)                                                \
+#define NOHANDLESCOPE(isolate)                                                 \
     dart::NoHandleScope no_vm_internal_handles_scope_(isolate);
 
+
+// The class ReusableHandleScope is used in regions of the
+// virtual machine where isolate specific reusable handles are used.
+// This class asserts that we do not add code that will result in recursive
+// uses of reusable handles.
+// It is used as follows:
+// {
+//   REUSABLE_HANDLESCOPE(isolate);
+//   ....
+//   .....
+//   code that uses isolate specific reusable handles.
+//   ....
+// }
+#if defined(DEBUG)
+class ReusableHandleScope : public StackResource {
+ public:
+  explicit ReusableHandleScope(BaseIsolate* isolate);
+  ReusableHandleScope();
+  ~ReusableHandleScope();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ReusableHandleScope);
+};
+#else  // defined(DEBUG)
+class ReusableHandleScope : public ValueObject {
+ public:
+  explicit ReusableHandleScope(BaseIsolate* isolate) { }
+  ReusableHandleScope() { }
+  ~ReusableHandleScope() { }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ReusableHandleScope);
+};
+#endif  // defined(DEBUG)
+
+// Macro to start a no handles scope in the code.

[Ivan Posva, 2013/06/16 11:15:26]

Comment does not match code.

[siva, 2013/06/19 20:41:55]

Done.

+#define REUSABLE_HANDLESCOPE(isolate)                                          \
+    dart::ReusableHandleScope reusable_vm_internal_handles_scope_(isolate);
+
 }  // namespace dart
 
 #endif  // VM_HANDLES_H_