Use map to distinguish type feedback vectors.

R=mvstanton@chromium.org, ulan@chromium.org
BUG=v8:5808

Review-Url: https://codereview.chromium.org/2617363003
Cr-Commit-Position: refs/heads/master@{#42137}

src/heap/heap.cc

@@ -2247,6 +2247,7 @@ bool Heap::CreateInitialMaps() {
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, scope_info)
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, module_info)
+    ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, type_feedback_vector)
     ALLOCATE_PRIMITIVE_MAP(HEAP_NUMBER_TYPE, HeapNumber::kSize, heap_number,
                            Context::NUMBER_FUNCTION_INDEX)
     ALLOCATE_MAP(MUTABLE_HEAP_NUMBER_TYPE, HeapNumber::kSize,
@@ -2775,6 +2776,7 @@ void Heap::CreateInitialObjects() {
                                     empty_fixed_array());
     empty_type_feedback_vector->set(TypeFeedbackVector::kInvocationCountIndex,
                                     Smi::kZero);
+    empty_type_feedback_vector->set_map(type_feedback_vector_map());
     set_empty_type_feedback_vector(*empty_type_feedback_vector);
 
     // We use a canonical empty LiteralsArray for all functions that neither

src/heap/heap.h

@@ -94,6 +94,7 @@ using v8::MemoryPressureLevel;
   V(Map, external_map, ExternalMap)                                            \
   V(Map, bytecode_array_map, BytecodeArrayMap)                                 \
   V(Map, module_info_map, ModuleInfoMap)                                       \
+  V(Map, type_feedback_vector_map, TypeFeedbackVectorMap)                      \
   /* String maps */                                                            \
   V(Map, native_source_string_map, NativeSourceStringMap)                      \
   V(Map, string_map, StringMap)                                                \

src/objects-inl.h

@@ -349,7 +349,9 @@ bool Object::IsLayoutDescriptor() const {
   return IsSmi() || IsFixedTypedArrayBase();
 }
 
-bool HeapObject::IsTypeFeedbackVector() const { return IsFixedArray(); }
+bool HeapObject::IsTypeFeedbackVector() const {
+  return map() == GetHeap()->type_feedback_vector_map();
+}
 
 bool HeapObject::IsTypeFeedbackMetadata() const { return IsFixedArray(); }
 

src/type-feedback-vector-inl.h

@@ -27,7 +27,7 @@ FeedbackVectorSlot FeedbackVectorSpecBase<Derived>::AddSlot(
 
 // static
 TypeFeedbackMetadata* TypeFeedbackMetadata::cast(Object* obj) {
-  DCHECK(obj->IsTypeFeedbackVector());
+  DCHECK(obj->IsTypeFeedbackMetadata());
   return reinterpret_cast<TypeFeedbackMetadata*>(obj);
 }
 

src/type-feedback-vector.cc

@@ -191,6 +191,7 @@ Handle<TypeFeedbackVector> TypeFeedbackVector::New(
   }
 
   Handle<FixedArray> array = factory->NewFixedArray(length, TENURED);
+  array->set_map_no_write_barrier(isolate->heap()->type_feedback_vector_map());
   array->set(kMetadataIndex, *metadata);
   array->set(kInvocationCountIndex, Smi::kZero);