Ensure slow properties for simple {__proto__:null} literals.

src/code-stub-assembler.cc

 // 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.
 #include "src/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 2029 matching lines @@
   Node* start_address = IntPtrAdd(
       result_word, IntPtrConstant(NameDictionary::OffsetOfElementAt(
                                       NameDictionary::kElementsStartIndex) -
                                   kHeapObjectTag));
   Node* end_address = IntPtrAdd(
       result_word, IntPtrSub(store_size, IntPtrConstant(kHeapObjectTag)));
   StoreFieldsNoWriteBarrier(start_address, end_address, filler);
   return result;
 }
 
+Node* CodeStubAssembler::CopyNameDictionary(Node* dictionary,
+                                            Label* large_object_fallback) {
+  Comment("Copy boilerplate property dict");
+  Label done(this);
+  Node* length = SmiUntag(LoadFixedArrayBaseLength(dictionary));
+  GotoIf(
+      IntPtrGreaterThan(length, IntPtrConstant(FixedArray::kMaxRegularLength)),
+      large_object_fallback);
+  Node* properties =
+      AllocateNameDictionary(SmiUntag(GetCapacity<NameDictionary>(dictionary)));
+  CopyFixedArrayElements(FAST_ELEMENTS, dictionary, properties, length,
+                         SKIP_WRITE_BARRIER, INTPTR_PARAMETERS);
+  return properties;
+}
+
 Node* CodeStubAssembler::AllocateJSObjectFromMap(Node* map, Node* properties,
                                                  Node* elements,
                                                  AllocationFlags flags) {
   CSA_ASSERT(this, IsMap(map));
   Node* size =
       IntPtrMul(LoadMapInstanceSize(map), IntPtrConstant(kPointerSize));
   Node* object = AllocateInNewSpace(size, flags);
   StoreMapNoWriteBarrier(object, map);
   InitializeJSObjectFromMap(object, map, size, properties, elements);
   return object;
@@ skipping 6681 matching lines @@
         formatted.c_str(), TENURED);
     CallRuntime(Runtime::kGlobalPrint, NoContextConstant(),
                 HeapConstant(string));
   }
   CallRuntime(Runtime::kDebugPrint, NoContextConstant(), tagged_value);
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8