Avoid handle dereference during graph optimization.

src/handles.h

 // Copyright 2011 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 47 matching lines @@
     a = b;  // Fake assignment to enforce type checks.
     USE(a);
 #endif
     location_ = reinterpret_cast<T**>(handle.location());
   }
 
   INLINE(T* operator ->() const) { return operator*(); }
 
   // Check if this handle refers to the exact same object as the other handle.
   bool is_identical_to(const Handle<T> other) const {
-    return operator*() == *other;
+    return *location_ == *other.location();

[Jakob Kummerow, 2013/01/23 12:09:18]

Why "location_" vs "location()"? Let's be consistent.

[Yang, 2013/01/23 13:34:25]

Done.

   }
 
   // Provides the C++ dereference operator.
   INLINE(T* operator*() const);
 
   // Returns the address to where the raw pointer is stored.
   T** location() const {
     ASSERT(location_ == NULL ||
            reinterpret_cast<Address>(*location_) != kZapValue);
     return location_;
@@ skipping 253 matching lines @@
   ~NoHandleAllocation() {}
 #else
   inline NoHandleAllocation();
   inline ~NoHandleAllocation();
  private:
   int level_;
   bool active_;
 #endif
 };
 
+
+class NoHandleDereference BASE_EMBEDDED {
+ public:
+#ifndef DEBUG
+  NoHandleDereference() {}
+  ~NoHandleDereference() {}
+#else
+  inline NoHandleDereference();
+  inline ~NoHandleDereference();
+ private:
+  int old_state_;

[Jakob Kummerow, 2013/01/23 12:09:18]

This is used to store bools, so it should be a bool.

[Yang, 2013/01/23 13:34:25]

Done.

+  bool active_;
+#endif
+};
+
+
+class AllowHandleDereference BASE_EMBEDDED {
+ public:
+#ifndef DEBUG
+  AllowHandleDereference() {}
+  ~AllowHandleDereference() {}
+#else
+  inline AllowHandleDereference();
+  inline ~AllowHandleDereference();
+ private:
+  int old_state_;

[Jakob Kummerow, 2013/01/23 12:09:18]

Same here.

[Yang, 2013/01/23 13:34:25]

Done.

+  bool active_;
+#endif
+};
+
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_