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

test/cctest/test-code-stub-assembler.cc

 // Copyright 2015 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/base/utils/random-number-generator.h"
 #include "src/code-factory.h"
 #include "src/code-stub-assembler.h"
 #include "src/compiler/node.h"
 #include "src/ic/stub-cache.h"
 #include "src/isolate.h"
@@ skipping 329 matching lines @@
   {
     // TryToName(<non-internalized string>) => bailout.
     Handle<Object> key = isolate->factory()->NewStringFromAsciiChecked("test");
     ft.CheckTrue(key, expect_bailout);
   }
 }
 
 namespace {
 
 template <typename Dictionary>
+void TestEntryToIndex() {
+  Isolate* isolate(CcTest::InitIsolateOnce());
+
+  const int kNumParams = 1;
+  CodeStubAssemblerTester m(isolate, kNumParams);
+  {
+    Node* entry = m.SmiUntag(m.Parameter(0));
+    Node* result = m.EntryToIndex<Dictionary>(entry);
+    m.Return(m.SmiTag(result));
+  }
+
+  Handle<Code> code = m.GenerateCode();
+  FunctionTester ft(code, kNumParams);
+
+  // Test a wide range of entries but staying linear in the first 100 entries.
+  for (int entry = 0; entry < Dictionary::kMaxCapacity;
+       entry = entry * 1.01 + 1) {
+    Handle<Object> result =
+        ft.Call(handle(Smi::FromInt(entry), isolate)).ToHandleChecked();
+    CHECK_EQ(Dictionary::EntryToIndex(entry), Smi::cast(*result)->value());
+  }
+}
+
+TEST(NameDictionaryEntryToIndex) { TestEntryToIndex<NameDictionary>(); }
+TEST(GlobalDictionaryEntryToIndex) { TestEntryToIndex<GlobalDictionary>(); }
+
+}  // namespace
+
+namespace {
+
+template <typename Dictionary>
 void TestNameDictionaryLookup() {
   typedef CodeStubAssembler::Label Label;
   typedef CodeStubAssembler::Variable Variable;
   Isolate* isolate(CcTest::InitIsolateOnce());
 
   const int kNumParams = 4;
   CodeStubAssemblerTester m(isolate, kNumParams);
 
   enum Result { kFound, kNotFound };
   {
@@ skipping 1259 matching lines @@
 
     Node* result = m.AllocateJSObjectFromMap(map, properties, elements);
 
     m.Return(result);
   }
 
   Handle<Code> code = m.GenerateCode();
   FunctionTester ft(code, kNumParams);
 
   Handle<Map> maps[] = {
-      isolate->object_with_null_prototype_map(),
       handle(isolate->object_function()->initial_map(), isolate),
       handle(isolate->array_function()->initial_map(), isolate),
   };
 
 #define VERIFY(result, map_value, properties_value, elements_value) \
   CHECK_EQ(result->map(), map_value);                               \
   CHECK_EQ(result->properties(), properties_value);                 \
   CHECK_EQ(result->elements(), elements_value);
 
   {
     Handle<Object> empty_fixed_array = factory->empty_fixed_array();
     for (int i = 0; i < arraysize(maps); i++) {
       Handle<Map> map = maps[i];
       Handle<JSObject> result = Handle<JSObject>::cast(
           ft.Call(map, empty_fixed_array, empty_fixed_array).ToHandleChecked());
       VERIFY(result, *map, *empty_fixed_array, *empty_fixed_array);
+      CHECK(result->HasFastProperties());
 #ifdef VERIFY_HEAP
       isolate->heap()->Verify();
 #endif
     }
   }
 
   {
     // TODO(cbruni): handle in-object properties
     Handle<JSObject> object = Handle<JSObject>::cast(
         v8::Utils::OpenHandle(*CompileRun("var object = {a:1,b:2, 1:1, 2:2}; "
                                           "object")));
     JSObject::NormalizeProperties(object, KEEP_INOBJECT_PROPERTIES, 0,
                                   "Normalize");
     Handle<JSObject> result = Handle<JSObject>::cast(
         ft.Call(handle(object->map()), handle(object->properties()),
                 handle(object->elements()))
             .ToHandleChecked());
     VERIFY(result, object->map(), object->properties(), object->elements());
+    CHECK(!result->HasFastProperties());
 #ifdef VERIFY_HEAP
     isolate->heap()->Verify();
 #endif
   }
+#undef VERIFY
+}
+
+TEST(AllocateNameDictionary) {
+  Isolate* isolate(CcTest::InitIsolateOnce());
+  Factory* factory = isolate->factory();
+
+  const int kNumParams = 1;
+  CodeStubAssemblerTester m(isolate, kNumParams);
+
+  {
+    Node* capacity = m.Parameter(0);
+    Node* result = m.AllocateNameDictionary(m.SmiUntag(capacity));
+    m.Return(result);
+  }
+
+  Handle<Code> code = m.GenerateCode();
+  FunctionTester ft(code, kNumParams);
+
+  {
+    Handle<Object> empty_fixed_array = factory->empty_fixed_array();
+    for (int i = 0; i < 256; i = i * 1.1 + 1) {
+      Handle<JSObject> result = Handle<JSObject>::cast(
+          ft.Call(handle(Smi::FromInt(i), isolate)).ToHandleChecked());
+      Handle<NameDictionary> dict = NameDictionary::New(isolate, i);
+      // Both dictionaries should be memory equal.
+      int size =
+          FixedArrayBase::kHeaderSize + (dict->length() - 1) * kPointerSize;
+      CHECK_EQ(0, memcmp(*dict, *result, size));
+    }
+  }
 }
 
 }  // namespace internal
 }  // namespace v8