Micro-optimize not-found for elements on objects with empty_fixed_array backing store

src/lookup-inl.h

 // Copyright 2014 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_LOOKUP_INL_H_
 #define V8_LOOKUP_INL_H_
 
 #include "src/lookup.h"
 
 namespace v8 {
@@ skipping 48 matching lines @@
     case INTERCEPTOR:
       if (IsElement()) {
         // TODO(verwaest): Optimize.
         if (holder->IsStringObjectWithCharacterAt(index_)) {
           PropertyAttributes attributes =
               static_cast<PropertyAttributes>(READ_ONLY | DONT_DELETE);
           property_details_ = PropertyDetails(attributes, v8::internal::DATA, 0,
                                               PropertyCellType::kNoCell);
         } else {
           JSObject* js_object = JSObject::cast(holder);
+          if (js_object->elements() == isolate()->heap()->empty_fixed_array()) {
+            return NOT_FOUND;
+          }
+
           ElementsAccessor* accessor = js_object->GetElementsAccessor();
           FixedArrayBase* backing_store = js_object->elements();
           number_ = accessor->GetIndexForKey(backing_store, index_);
           if (number_ == kMaxUInt32) return NOT_FOUND;
           if (accessor->GetAttributes(js_object, index_, backing_store) ==
               ABSENT) {
             return NOT_FOUND;
           }
           property_details_ = accessor->GetDetails(backing_store, number_);
         }
@@ skipping 51 matching lines @@
     default:
       return NOT_FOUND;
   }
   UNREACHABLE();
   return state_;
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_LOOKUP_INL_H_