[runtime] More LookupIterator / Transition related performance tweaks

src/field-type.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_FIELD_TYPE_H_
 #define V8_FIELD_TYPE_H_
 
 #include "src/handles.h"
 #include "src/objects.h"
 #include "src/ostreams.h"
 
 namespace v8 {
 namespace internal {
 
 class FieldType : public Object {
  public:
   static FieldType* None();
   static FieldType* Any();
   static Handle<FieldType> None(Isolate* isolate);
   static Handle<FieldType> Any(Isolate* isolate);
   static FieldType* Class(i::Map* map);
   static Handle<FieldType> Class(i::Handle<i::Map> map, Isolate* isolate);
   static FieldType* cast(Object* object);
 
-  bool NowContains(Object* value);
-  bool NowContains(Handle<Object> value);
+  bool NowContains(Object* value) {
+    if (this == Any()) return true;
+    if (this == None()) return false;
+    if (!value->IsHeapObject()) return false;
+    return HeapObject::cast(value)->map() == Map::cast(this);
+  }
+
+  bool NowContains(Handle<Object> value) { return NowContains(*value); }
+
   bool IsClass();
   Handle<i::Map> AsClass();
   bool IsNone() { return this == None(); }
   bool IsAny() { return this == Any(); }
   bool NowStable();
   bool NowIs(FieldType* other);
   bool NowIs(Handle<FieldType> other);
   Type* Convert(Zone* zone);
 
   void PrintTo(std::ostream& os);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_FIELD_TYPE_H_