Avoid write barrier when writing an external pointer to an internal field.

src/objects-inl.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 1367 matching lines @@
   ASSERT(index < GetInternalFieldCount() && index >= 0);
   // Internal objects do follow immediately after the header, whereas in-object
   // properties are at the end of the object. Therefore there is no need
   // to adjust the index here.
   int offset = GetHeaderSize() + (kPointerSize * index);
   WRITE_FIELD(this, offset, value);
   WRITE_BARRIER(GetHeap(), this, offset, value);
 }
 
 
+void JSObject::SetInternalField(int index, Smi* value) {
+  ASSERT(index < GetInternalFieldCount() && index >= 0);
+  // Internal objects do follow immediately after the header, whereas in-object
+  // properties are at the end of the object. Therefore there is no need
+  // to adjust the index here.
+  int offset = GetHeaderSize() + (kPointerSize * index);
+  WRITE_FIELD(this, offset, value);
+}
+
+
 // Access fast-case object properties at index. The use of these routines
 // is needed to correctly distinguish between properties stored in-object and
 // properties stored in the properties array.
 Object* JSObject::FastPropertyAt(int index) {
   // Adjust for the number of properties stored in the object.
   index -= map()->inobject_properties();
   if (index < 0) {
     int offset = map()->instance_size() + (index * kPointerSize);
     return READ_FIELD(this, offset);
   } else {
@@ skipping 3220 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_