With >= 64 non-string instance types, I removed an optimization

src/objects-inl.h

 // Copyright 2012 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 203 matching lines @@
 bool Object::IsSpecFunction() {
   if (!Object::IsHeapObject()) return false;
   InstanceType type = HeapObject::cast(this)->map()->instance_type();
   return type == JS_FUNCTION_TYPE || type == JS_FUNCTION_PROXY_TYPE;
 }
 
 
 bool Object::IsInternalizedString() {
   if (!this->IsHeapObject()) return false;
   uint32_t type = HeapObject::cast(this)->map()->instance_type();
-  STATIC_ASSERT(kInternalizedTag != 0);
-  return (type & (kIsNotStringMask | kIsInternalizedMask)) ==
-      (kInternalizedTag | kStringTag);
+  STATIC_ASSERT(kNotInternalizedTag != 0);
+  return type < kNotInternalizedTag;

[Yang, 2013/07/19 09:52:18]

I kinda prefer the bit-masking way, since it doesn't implicitly assume anything.
Shouldn't be more expensive. Below as well. But this is your choice.

[mvstanton, 2013/07/19 11:07:42]

I wondered about that too, it's better to be symmetrical with the way we do the
test in assembly. I'll change to the bit test.

 }
 
 
 bool Object::IsConsString() {
   if (!IsString()) return false;
   return StringShape(String::cast(this)).IsCons();
 }
 
 
 bool Object::IsSlicedString() {
@@ skipping 75 matching lines @@
 
 StringShape::StringShape(InstanceType t)
   : type_(static_cast<uint32_t>(t)) {
   set_valid();
   ASSERT((type_ & kIsNotStringMask) == kStringTag);
 }
 
 
 bool StringShape::IsInternalized() {
   ASSERT(valid());
-  STATIC_ASSERT(kInternalizedTag != 0);
-  return (type_ & (kIsNotStringMask | kIsInternalizedMask)) ==
-      (kInternalizedTag | kStringTag);
+  STATIC_ASSERT(kNotInternalizedTag != 0);
+  return type_ < kNotInternalizedTag;

[mvstanton, 2013/07/19 11:07:42]

I restored this one too.

 }
 
 
 bool String::IsOneByteRepresentation() {
   uint32_t type = map()->instance_type();
   return (type & kStringEncodingMask) == kOneByteStringTag;
 }
 
 
 bool String::IsTwoByteRepresentation() {
@@ skipping 5850 matching lines @@
 #undef WRITE_UINT32_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_