[elements] Add CreateFromArrayLike fast-path for JS_ARRAY_TYPE

src/objects.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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 840 matching lines @@
     return isolate->factory()->undefined_value();
   }
   if (!func->IsCallable()) {
     THROW_NEW_ERROR(isolate, NewTypeError(MessageTemplate::kPropertyNotFunction,
                                           func, name, receiver),
                     Object);
   }
   return func;
 }
 
+namespace {
+MaybeHandle<FixedArray> CreateListFromArrayLikeFastPath(
+    Isolate* isolate, Handle<Object> object, ElementTypes element_types) {
+  if (element_types != ElementTypes::kAll || !object->IsJSArray()) {
+    return MaybeHandle<FixedArray>();
+  }
+  Handle<JSArray> array = Handle<JSArray>::cast(object);
+  uint32_t length;
+  if (!array->HasArrayPrototype(isolate) ||
+      !array->length()->ToUint32(&length) || !array->HasFastElements() ||
+      !JSObject::PrototypeHasNoElements(isolate, *array)) {
+    return MaybeHandle<FixedArray>();
+  }
+  return array->GetElementsAccessor()->CreateListFromArray(isolate, array);
+}
+}  // namespace
 
 // static
 MaybeHandle<FixedArray> Object::CreateListFromArrayLike(
     Isolate* isolate, Handle<Object> object, ElementTypes element_types) {
+  // Fast-path for JS_ARRAY_TYPE.
+  MaybeHandle<FixedArray> fast_result =
+      CreateListFromArrayLikeFastPath(isolate, object, element_types);
+  if (!fast_result.is_null()) return fast_result;
   // 1. ReturnIfAbrupt(object).
   // 2. (default elementTypes -- not applicable.)
   // 3. If Type(obj) is not Object, throw a TypeError exception.
   if (!object->IsJSReceiver()) {
     THROW_NEW_ERROR(isolate,
                     NewTypeError(MessageTemplate::kCalledOnNonObject,
                                  isolate->factory()->NewStringFromAsciiChecked(
                                      "CreateListFromArrayLike")),
                     FixedArray);
   }
+
   // 4. Let len be ? ToLength(? Get(obj, "length")).
   Handle<JSReceiver> receiver = Handle<JSReceiver>::cast(object);
   Handle<Object> raw_length_number;
   ASSIGN_RETURN_ON_EXCEPTION(isolate, raw_length_number,
                              Object::GetLengthFromArrayLike(isolate, receiver),
                              FixedArray);
   uint32_t len;
   if (!raw_length_number->ToUint32(&len) ||
       len > static_cast<uint32_t>(FixedArray::kMaxLength)) {
     THROW_NEW_ERROR(isolate,
@@ skipping 19533 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8