src/builtins/iterator.tq

// 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-iterator-gen.h'

namespace iterator {
// Returned from IteratorBuiltinsAssembler::GetIterator().
@export
struct IteratorRecord {
  // iteratorRecord.[[Iterator]]
  object: JSReceiver;

  // iteratorRecord.[[NextMethod]]
  next: JSAny;
}

extern macro IteratorBuiltinsAssembler::FastIterableToList(
    implicit context: Context)(JSAny): JSArray labels Slow;

extern macro IteratorBuiltinsAssembler::GetIteratorMethod(
    implicit context: Context)(JSAny): JSAny;
extern macro IteratorBuiltinsAssembler::GetIterator(implicit context: Context)(
    JSAny): IteratorRecord;
extern macro IteratorBuiltinsAssembler::GetIterator(implicit context: Context)(
    JSAny, JSAny): IteratorRecord;

extern macro IteratorBuiltinsAssembler::IteratorStep(implicit context: Context)(
    IteratorRecord): JSReceiver
    labels Done;
extern macro IteratorBuiltinsAssembler::IteratorStep(implicit context: Context)(
    IteratorRecord, Map): JSReceiver
    labels Done;

extern macro IteratorBuiltinsAssembler::IteratorValue(
    implicit context: Context)(JSReceiver): JSAny;
extern macro IteratorBuiltinsAssembler::IteratorValue(
    implicit context: Context)(JSReceiver, Map): JSAny;

extern macro IteratorBuiltinsAssembler::IterableToList(
    implicit context: Context)(JSAny, JSAny): JSArray;

extern macro IteratorBuiltinsAssembler::StringListFromIterable(
    implicit context: Context)(JSAny): JSArray;

extern builtin IterableToListWithSymbolLookup(implicit context: Context)(JSAny):
    JSArray;
extern builtin IterableToFixedArrayWithSymbolLookupSlow(
    implicit context: Context)(JSAny): FixedArray;

transitioning builtin GetIteratorWithFeedback(
    context: Context, receiver: JSAny, loadSlot: TaggedIndex,
    callSlot: TaggedIndex,
    maybeFeedbackVector: Undefined|FeedbackVector): JSAny {
  // TODO(v8:9891): Remove this dcheck once all callers are ported to Torque.
  // This dcheck ensures correctness of maybeFeedbackVector's type which can
  // be easily broken for calls from CSA.
  dcheck(
      IsUndefined(maybeFeedbackVector) ||
      Is<FeedbackVector>(maybeFeedbackVector));
  let iteratorMethod: JSAny;
  typeswitch (maybeFeedbackVector) {
    case (Undefined): {
      iteratorMethod = GetProperty(receiver, IteratorSymbolConstant());
    }
    case (feedback: FeedbackVector): {
      iteratorMethod = LoadIC(
          context, receiver, IteratorSymbolConstant(), loadSlot, feedback);
    }
  }
  // TODO(v8:10047): Use TaggedIndex here once TurboFan supports it.
  const callSlotSmi: Smi = TaggedIndexToSmi(callSlot);
  return CallIteratorWithFeedback(
      context, receiver, iteratorMethod, callSlotSmi, maybeFeedbackVector);
}

extern macro LoadContextFromBaseline(): Context;
extern macro LoadFeedbackVectorFromBaseline(): FeedbackVector;

transitioning builtin GetIteratorBaseline(
    receiver: JSAny, loadSlot: TaggedIndex, callSlot: TaggedIndex): JSAny {
  const context: Context = LoadContextFromBaseline();
  const feedback: FeedbackVector = LoadFeedbackVectorFromBaseline();
  const iteratorMethod: JSAny =
      LoadIC(context, receiver, IteratorSymbolConstant(), loadSlot, feedback);
  // TODO(v8:10047): Use TaggedIndex here once TurboFan supports it.
  const callSlotSmi: Smi = TaggedIndexToSmi(callSlot);
  return CallIteratorWithFeedback(
      context, receiver, iteratorMethod, callSlotSmi, feedback);
}

extern macro CreateAsyncFromSyncIterator(Context, JSAny): JSAny;

transitioning builtin CreateAsyncFromSyncIteratorBaseline(syncIterator: JSAny):
    JSAny {
  const context: Context = LoadContextFromBaseline();
  return CreateAsyncFromSyncIterator(context, syncIterator);
}

macro GetLazyReceiver(receiver: JSAny): JSAny {
  return receiver;
}

transitioning builtin CallIteratorWithFeedback(
    context: Context, receiver: JSAny, iteratorMethod: JSAny, callSlot: Smi,
    feedback: Undefined|FeedbackVector): JSAny {
  // TODO(v8:10047): Use TaggedIndex here once TurboFan supports it.
  const callSlotUnTagged: uintptr = Unsigned(SmiUntag(callSlot));
  ic::CollectCallFeedback(
      iteratorMethod, %MakeLazy<JSAny, JSAny>('GetLazyReceiver', receiver),
      context, feedback, callSlotUnTagged);
  const iteratorCallable: Callable = Cast<Callable>(iteratorMethod)
      otherwise ThrowIteratorError(receiver);
  const iterator = Call(context, iteratorCallable, receiver);
  ThrowIfNotJSReceiver(iterator, MessageTemplate::kSymbolIteratorInvalid, '');
  return iterator;
}

// https://tc39.es/ecma262/#sec-iteratorclose
// IteratorCloseOnException should be used to close iterators due to exceptions
// being thrown.
@export
transitioning macro IteratorCloseOnException(implicit context: Context)(
    iterator: IteratorRecord): void {
  try {
    // 3. Let innerResult be GetMethod(iterator, "return").
    const method = GetProperty(iterator.object, kReturnString);

    // 4. If innerResult.[[Type]] is normal, then
    //   a. Let return be innerResult.[[Value]].
    //   b. If return is undefined, return Completion(completion).
    if (method == Undefined || method == Null) return;

    //   c. Set innerResult to Call(return, iterator).
    // If an exception occurs, the original exception remains bound
    Call(context, method, iterator.object);
  } catch (_e, _message) {
    // Swallow the exception.
  }

  // (5. If completion.[[Type]] is throw) return Completion(completion).
}

@export
transitioning macro IteratorClose(implicit context: Context)(
    iterator: IteratorRecord): void {
  // 3. Let innerResult be GetMethod(iterator, "return").
  const method = GetProperty(iterator.object, kReturnString);

  // 4. If innerResult.[[Type]] is normal, then
  //   a. Let return be innerResult.[[Value]].
  //   b. If return is undefined, return Completion(completion).
  if (method == Undefined || method == Null) return;

  //   c. Set innerResult to Call(return, iterator).
  const result = Call(context, method, iterator.object);

  // 5. If completion.[[Type]] is throw, return Completion(completion).
  // It is handled in IteratorCloseOnException.

  // 7. If innerResult.[[Value]] is not an Object, throw a TypeError
  // exception.
  Cast<JSReceiver>(result)
      otherwise ThrowTypeError(MessageTemplate::kCalledOnNonObject, 'return');
}

// https://tc39.es/proposal-iterator-helpers/#sec-iterator
transitioning javascript builtin IteratorConstructor(
    js-implicit context: NativeContext, receiver: JSAny, newTarget: JSAny,
    target: JSFunction)(): JSObject {
  const methodName: constexpr string = 'Iterator';

  // 1. If NewTarget is undefined or the active function object, throw a
  //    TypeError exception.
  if (newTarget == Undefined) {
    ThrowTypeError(MessageTemplate::kConstructorNotFunction, methodName);
  }
  if (newTarget == target) {
    ThrowTypeError(MessageTemplate::kConstructAbstractClass, methodName);
  }

  // 2. Return ? OrdinaryCreateFromConstructor(NewTarget,
  //    "%Iterator.prototype%").
  const map = GetDerivedMap(target, UnsafeCast<JSReceiver>(newTarget));
  return AllocateFastOrSlowJSObjectFromMap(map);
}
}  // namespace iterator