[runtime] Object.create(null) creates a slow object

src/code-stub-assembler.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_CODE_STUB_ASSEMBLER_H_
 #define V8_CODE_STUB_ASSEMBLER_H_
 
 #include <functional>
 
 #include "src/compiler/code-assembler.h"
@@ skipping 90 matching lines @@
 
   compiler::Node* HashSeed();
   compiler::Node* StaleRegisterConstant();
 
   compiler::Node* IntPtrOrSmiConstant(int value, ParameterMode mode);
 
   compiler::Node* IntPtrAddFoldConstants(compiler::Node* left,
                                          compiler::Node* right);
   compiler::Node* IntPtrSubFoldConstants(compiler::Node* left,
                                          compiler::Node* right);
+  void BranchIfWordIsPowerOfTwo(compiler::Node* value, Label* if_true,
+                                Label* if_false);
 
   // Float64 operations.
   compiler::Node* Float64Ceil(compiler::Node* x);
   compiler::Node* Float64Floor(compiler::Node* x);
   compiler::Node* Float64Round(compiler::Node* x);
   compiler::Node* Float64Trunc(compiler::Node* x);
 
   // Tag a Word as a Smi value.
   compiler::Node* SmiTag(compiler::Node* value);
   // Untag a Smi value as a Word.
@@ skipping 303 matching lines @@
 
   // Allocate a RegExpResult with the given length (the number of captures,
   // including the match itself), index (the index where the match starts),
   // and input string. |length| and |index| are expected to be tagged, and
   // |input| must be a string.
   compiler::Node* AllocateRegExpResult(compiler::Node* context,
                                        compiler::Node* length,
                                        compiler::Node* index,
                                        compiler::Node* input);
 
+  compiler::Node* AllocateNameDictionary(int capacity);
+  compiler::Node* AllocateNameDictionary(compiler::Node* capacity);
+
   compiler::Node* AllocateJSObjectFromMap(compiler::Node* map,
                                           compiler::Node* properties = nullptr,
                                           compiler::Node* elements = nullptr);
 
   void InitializeJSObjectFromMap(compiler::Node* object, compiler::Node* map,
                                  compiler::Node* size,
                                  compiler::Node* properties = nullptr,
                                  compiler::Node* elements = nullptr);
 
   void InitializeJSObjectBody(compiler::Node* object, compiler::Node* map,
@@ skipping 654 matching lines @@
   static const int kElementLoopUnrollThreshold = 8;
 };
 
 #define CSA_ASSERT(x) Assert((x), #x, __FILE__, __LINE__)
 
 DEFINE_OPERATORS_FOR_FLAGS(CodeStubAssembler::AllocationFlags);
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_CODE_STUB_ASSEMBLER_H_