Use map to distinguish type feedback vectors.

src/type-feedback-vector-inl.h

 // Copyright 2012 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_TYPE_FEEDBACK_VECTOR_INL_H_
 #define V8_TYPE_FEEDBACK_VECTOR_INL_H_
 
 #include "src/globals.h"
 #include "src/type-feedback-vector.h"
 
 namespace v8 {
 namespace internal {
 
 
 template <typename Derived>
 FeedbackVectorSlot FeedbackVectorSpecBase<Derived>::AddSlot(
     FeedbackVectorSlotKind kind) {
   int slot = This()->slots();
   int entries_per_slot = TypeFeedbackMetadata::GetSlotSize(kind);
   This()->append(kind);
   for (int i = 1; i < entries_per_slot; i++) {
     This()->append(FeedbackVectorSlotKind::INVALID);
   }
   return FeedbackVectorSlot(slot);
 }
 
 
 // static
 TypeFeedbackMetadata* TypeFeedbackMetadata::cast(Object* obj) {
-  DCHECK(obj->IsTypeFeedbackVector());
+  DCHECK(obj->IsTypeFeedbackMetadata());

[mvstanton, 2017/01/09 09:56:38]

Good catch!

   return reinterpret_cast<TypeFeedbackMetadata*>(obj);
 }
 
 bool TypeFeedbackMetadata::is_empty() const {
   if (length() == 0) return true;
   return false;
 }
 
 int TypeFeedbackMetadata::slot_count() const {
   if (length() == 0) return 0;
@@ skipping 231 matching lines @@
   int index = vector()->GetIndex(slot()) + 1;
   vector()->set(index, feedback_extra, mode);
 }
 
 
 Isolate* FeedbackNexus::GetIsolate() const { return vector()->GetIsolate(); }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TYPE_FEEDBACK_VECTOR_INL_H_