Optimizing HandleScope. Also fixed HandleScope destruction when API getter th...

src/handles.h

 // Copyright 2006-2008 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 89 matching lines @@
 // handle scope and a new one is created, all allocations will take
 // place in the new handle scope until it is deleted.  After that,
 // new handles will again be allocated in the original handle scope.
 //
 // After the handle scope of a local handle has been deleted the
 // garbage collector will no longer track the object stored in the
 // handle and may deallocate it.  The behavior of accessing a handle
 // for which the handle scope has been deleted is undefined.
 class HandleScope {
  public:
-  HandleScope() : previous_(current_) {
-    current_.extensions = 0;
+  HandleScope() : prev_next_(current_.next), prev_limit_(current_.limit) {
+    current_.level++;
   }
 
   ~HandleScope() {
-    Leave(&previous_);
+    current_.next = prev_next_;
+    current_.level--;
+    if (current_.limit != prev_limit_) {
+      current_.limit = prev_limit_;
+      DeleteExtensions();
+    }
+#ifdef DEBUG
+    ZapRange(prev_next_, prev_limit_);
+#endif
   }
 
   // Counts the number of allocated handles.
   static int NumberOfHandles();
 
   // Creates a new handle with the given value.
   template <typename T>
   static inline T** CreateHandle(T* value) {
     internal::Object** cur = current_.next;
     if (cur == current_.limit) cur = Extend();
     // Update the current next field, set the value in the created
     // handle, and return the result.
     ASSERT(cur < current_.limit);
     current_.next = cur + 1;
 
     T** result = reinterpret_cast<T**>(cur);
     *result = value;
     return result;
   }
 
   // Deallocates any extensions used by the current scope.
   static void DeleteExtensions();
 
-  static Address current_extensions_address();
   static Address current_next_address();
   static Address current_limit_address();
+  static Address current_level_address();
 
  private:
   // Prevent heap allocation or illegal handle scopes.
   HandleScope(const HandleScope&);
   void operator=(const HandleScope&);
   void* operator new(size_t size);
   void operator delete(void* size_t);
 
   static v8::ImplementationUtilities::HandleScopeData current_;
-  const v8::ImplementationUtilities::HandleScopeData previous_;
-
-  // Pushes a fresh handle scope to be used when allocating new handles.
-  static void Enter(
-      v8::ImplementationUtilities::HandleScopeData* previous) {
-    *previous = current_;
-    current_.extensions = 0;
-  }
-
-  // Re-establishes the previous scope state. Should be called only
-  // once, and only for the current scope.
-  static void Leave(
-      const v8::ImplementationUtilities::HandleScopeData* previous) {
-    if (current_.extensions > 0) {
-      DeleteExtensions();
-    }
-    current_ = *previous;
-#ifdef DEBUG
-    ZapRange(current_.next, current_.limit);
-#endif
-  }
+  Object** const prev_next_;
+  Object** const prev_limit_;
 
   // Extend the handle scope making room for more handles.
   static internal::Object** Extend();
 
   // Zaps the handles in the half-open interval [start, end).
   static void ZapRange(internal::Object** start, internal::Object** end);
 
   friend class v8::HandleScope;
   friend class v8::ImplementationUtilities;
 };
@@ skipping 173 matching lines @@
 
 class NoHandleAllocation BASE_EMBEDDED {
  public:
 #ifndef DEBUG
   NoHandleAllocation() {}
   ~NoHandleAllocation() {}
 #else
   inline NoHandleAllocation();
   inline ~NoHandleAllocation();
  private:
-  int extensions_;
+  int level_;
 #endif
 };
 
 
 // ----------------------------------------------------------------------------
 
 
 // Stack allocated wrapper call for optimizing adding multiple
 // properties to an object.
 class OptimizedObjectForAddingMultipleProperties BASE_EMBEDDED {
  public:
   OptimizedObjectForAddingMultipleProperties(Handle<JSObject> object,
                                              int expected_property_count,
                                              bool condition = true);
   ~OptimizedObjectForAddingMultipleProperties();
  private:
   bool has_been_transformed_;  // Tells whether the object has been transformed.
   int unused_property_fields_;  // Captures the unused number of field.
   Handle<JSObject> object_;    // The object being optimized.
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_