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// Copyright 2018 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/builtins/builtins-array-gen.h'
namespace array {
// Naming convention from We have a similar intent but implement
// fastpaths using generics instead of using a class hierarchy for elements
// kinds specific implementations.
type GenericElementsAccessor extends ElementsKind;
type FastPackedSmiElements extends ElementsKind;
type FastPackedObjectElements extends ElementsKind;
type FastPackedDoubleElements extends ElementsKind;
type FastSmiOrObjectElements extends ElementsKind;
type FastDoubleElements extends ElementsKind;
type DictionaryElements extends ElementsKind;
macro EnsureWriteableFastElements(implicit context: Context)(array: JSArray) {
const elements: FixedArrayBase = array.elements;
if ( != kCOWMap) return;
// There are no COW *_DOUBLE_ELEMENTS arrays, so we are allowed to always
// extract FixedArrays and don't have to worry about FixedDoubleArrays.
const length = Convert<intptr>(Cast<Smi>(array.length) otherwise unreachable);
array.elements =
ExtractFixedArray(UnsafeCast<FixedArray>(elements), 0, length, length);
assert( != kCOWMap);
macro LoadElementOrUndefined(implicit context: Context)(
a: FixedArray, i: Smi): JSAny {
const e = UnsafeCast<(JSAny | TheHole)>(a.objects[i]);
return ReplaceTheHoleWithUndefined(e);
macro LoadElementOrUndefined(a: FixedDoubleArray, i: Smi): NumberOrUndefined {
const f: float64 = a.floats[i].Value() otherwise return Undefined;
return AllocateHeapNumberWithValue(f);
macro StoreArrayHole(elements: FixedDoubleArray, k: Smi): void {
elements.floats[k] = kDoubleHole;
macro StoreArrayHole(elements: FixedArray, k: Smi): void {
elements.objects[k] = TheHole;
extern macro SetPropertyLength(implicit context: Context)(JSAny, Number);
const kLengthDescriptorIndex:
constexpr int31 generates 'JSArray::kLengthDescriptorIndex';
const kAttributesReadOnlyMask: constexpr int31
generates 'PropertyDetails::kAttributesReadOnlyMask';
macro EnsureArrayLengthWritable(implicit context: Context)(map: Map):
void labels Bailout {
// Don't support arrays in dictionary named property mode.
if (IsDictionaryMap(map)) {
goto Bailout;
// Check whether the length property is writable. The length property is the
// only default named property on arrays. It's nonconfigurable, hence is
// guaranteed to stay the first property.
const descriptors: DescriptorArray = map.instance_descriptors;
const descriptor:&DescriptorEntry =
assert(TaggedEqual(descriptor->key, LengthStringConstant()));
const details: Smi = UnsafeCast<Smi>(descriptor->details);
if ((details & kAttributesReadOnlyMask) != 0) {
goto Bailout;
macro CreateJSArrayWithElements(implicit context: Context)(array: FixedArray):
JSArray {
const nativeContext: NativeContext = LoadNativeContext(context);
const map: Map =
LoadJSArrayElementsMap(ElementsKind::PACKED_ELEMENTS, nativeContext);
return AllocateJSArray(map, array, array.length);