Use the number of in-object properties when deciding how many fast...

src/objects-inl.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 1317 matching lines @@
 
 
 void JSObject::InitializeBody(int object_size) {
   Object* value = Heap::undefined_value();
   for (int offset = kHeaderSize; offset < object_size; offset += kPointerSize) {
     WRITE_FIELD(this, offset, value);
   }
 }
 
 
+bool JSObject::HasFastProperties() {
+  return !properties()->IsDictionary();
+}
+
+
+int JSObject::MaxFastProperties() {
+  // Allow extra fast properties if the object has more than
+  // kMaxFastProperties in-object properties. When this is the case,
+  // it is very unlikely that the object is being used as a dictionary
+  // and there is a good chance that allowing more map transitions
+  // will be worth it.
+  return Max(map()->inobject_properties(), kMaxFastProperties);
+}
+
+
 void Struct::InitializeBody(int object_size) {
   Object* value = Heap::undefined_value();
   for (int offset = kHeaderSize; offset < object_size; offset += kPointerSize) {
     WRITE_FIELD(this, offset, value);
   }
 }
 
 
-bool JSObject::HasFastProperties() {
-  return !properties()->IsDictionary();
-}
-
-
 bool Object::ToArrayIndex(uint32_t* index) {
   if (IsSmi()) {
     int value = Smi::cast(this)->value();
     if (value < 0) return false;
     *index = value;
     return true;
   }
   if (IsHeapNumber()) {
     double value = HeapNumber::cast(this)->value();
     uint32_t uint_value = static_cast<uint32_t>(value);
@@ skipping 1893 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_