[Isolates] Cleanup of codepaths slowing down Dromaeo in browser.

include/v8.h

 // Copyright 2007-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 92 matching lines @@
 class Data;
 class AccessorInfo;
 class StackTrace;
 class StackFrame;
 
 namespace internal {
 
 class Arguments;
 class Object;
 class Heap;
+class HeapObject;
 class Isolate;
 }
 
 
 // --- W e a k  H a n d l e s
 
 
 /**
  * A weak reference callback function.
  *
@@ skipping 307 matching lines @@
 
   /**
    * Counts the number of allocated handles.
    */
   static int NumberOfHandles();
 
   /**
    * Creates a new handle with the given value.
    */
   static internal::Object** CreateHandle(internal::Object* value);
+  // Faster version, uses HeapObject to obtain the current Isolate.
+  static internal::Object** CreateHandle(internal::HeapObject* value);
 
  private:
   // Make it impossible to create heap-allocated or illegal handle
   // scopes by disallowing certain operations.
   HandleScope(const HandleScope&);
   void operator=(const HandleScope&);
   void* operator new(size_t size);
   void operator delete(void*, size_t);
 
   // This Data class is accessible internally as HandleScopeData through a
@@ skipping 3026 matching lines @@
   static inline bool IsExternalTwoByteString(int instance_type) {
     int representation = (instance_type & kFullStringRepresentationMask);
     return representation == kExternalTwoByteRepresentationTag;
   }
 
   template <typename T>
   static inline T ReadField(Object* ptr, int offset) {
     uint8_t* addr = reinterpret_cast<uint8_t*>(ptr) + offset - kHeapObjectTag;
     return *reinterpret_cast<T*>(addr);
   }
+
+ static inline bool CanCastToHeapObject(void*) { return false; }
+ static inline bool CanCastToHeapObject(Context*) { return true; }
+ static inline bool CanCastToHeapObject(String*) { return true; }
+ static inline bool CanCastToHeapObject(Object*) { return true; }
+ static inline bool CanCastToHeapObject(Message*) { return true; }
+ static inline bool CanCastToHeapObject(StackTrace*) { return true; }
+ static inline bool CanCastToHeapObject(StackFrame*) { return true; }
+
 };
 
 }  // namespace internal
 
 
 template <class T>
 Handle<T>::Handle() : val_(0) { }
 
 
 template <class T>
 Local<T>::Local() : Handle<T>() { }
 
 
 template <class T>
 Local<T> Local<T>::New(Handle<T> that) {
   if (that.IsEmpty()) return Local<T>();
-  internal::Object** p = reinterpret_cast<internal::Object**>(*that);
+  T* that_ptr = *that;
+  internal::Object** p = reinterpret_cast<internal::Object**>(that_ptr);
+  if (internal::Internals::CanCastToHeapObject(that_ptr)) {
+    return Local<T>(reinterpret_cast<T*>(
+      HandleScope::CreateHandle(reinterpret_cast<internal::HeapObject*>(*p))));
+  }
   return Local<T>(reinterpret_cast<T*>(HandleScope::CreateHandle(*p)));
 }
 
 
 template <class T>
 Persistent<T> Persistent<T>::New(Handle<T> that) {
   if (that.IsEmpty()) return Persistent<T>();
   internal::Object** p = reinterpret_cast<internal::Object**>(*that);
   return Persistent<T>(reinterpret_cast<T*>(V8::GlobalizeReference(p)));
 }
@@ skipping 312 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_