src/builtins/array-foreach.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.

module array {
  macro ArrayForEachTorqueContinuation(
      context: Context, o: JSReceiver, len: Number, callbackfn: Callable,
      thisArg: Object, initial_k: Smi): Object {
    // 5. Let k be 0.
    // 6. Repeat, while k < len
    for (let k: Smi = initial_k; k < len; k = k + 1) {
      // 6a. Let Pk be ! ToString(k).
      const pK: String = ToString_Inline(context, k);

      // 6b. Let kPresent be ? HasProperty(O, Pk).
      const kPresent: Boolean = HasProperty(context, o, pK);

      // 6c. If kPresent is true, then
      if (kPresent == True) {
        // 6c. i. Let kValue be ? Get(O, Pk).
        const kValue: Object = GetProperty(context, o, pK);

        // 6c. ii. Perform ? Call(callbackfn, T, <kValue, k, O>).
        Call(context, callbackfn, thisArg, kValue, k, o);
      }

      // 6d. Increase k by 1. (done by the loop).
    }
    return Undefined;
  }

  javascript builtin ArrayForEachLoopEagerDeoptContinuation(
      context: Context, receiver: Object, callback: Object, thisArg: Object,
      initialK: Object, length: Object): Object {
    // The unsafe cast is safe because all continuation points in forEach are
    // after the ToObject(O) call that ensures we are dealing with a
    // JSReceiver.
    const jsreceiver: JSReceiver = unsafe_cast<JSReceiver>(receiver);
    return ArrayForEachLoopContinuation(
        context, jsreceiver, callback, thisArg, Undefined, jsreceiver, initialK,
        length, Undefined);
  }

  javascript builtin ArrayForEachLoopLazyDeoptContinuation(
      context: Context, receiver: Object, callback: Object, thisArg: Object,
      initialK: Object, length: Object, result: Object): Object {
    // The unsafe cast is safe because all continuation points in forEach are
    // after the ToObject(O) call that ensures we are dealing with a
    // JSReceiver.
    const jsreceiver: JSReceiver = unsafe_cast<JSReceiver>(receiver);
    return ArrayForEachLoopContinuation(
        context, jsreceiver, callback, thisArg, Undefined, jsreceiver, initialK,
        length, Undefined);
  }

  builtin ArrayForEachLoopContinuation(
      context: Context, receiver: JSReceiver, callback: Object, thisArg: Object,
      array: Object, object: Object, initialK: Object, length: Object,
      to: Object): Object {
    try {
      const callbackfn: Callable =
          cast<Callable>(callback) otherwise Unexpected;
      const k: Smi = cast<Smi>(initialK) otherwise Unexpected;
      const number_length: Number = cast<Number>(length) otherwise Unexpected;

      return ArrayForEachTorqueContinuation(
          context, receiver, number_length, callbackfn, thisArg, k);
    }
    label Unexpected {
      unreachable;
    }
  }

  macro VisitAllElements<FixedArrayType : type>(
      context: Context, a: JSArray, len: Smi, callbackfn: Callable,
      thisArg: Object): void labels
  Bailout(Smi) {
    let k: Smi = 0;
    const map: Map = a.map;

    try {
      // Build a fast loop over the smi array.
      for (; k < len; k = k + 1) {
        // Ensure that the map didn't change.
        if (map != a.map) goto Slow;
        // Ensure that we haven't walked beyond a possibly updated length.
        if (k >= a.length) goto Slow;

        try {
          const value: Object =
              LoadElementNoHole<FixedArrayType>(a, k) otherwise FoundHole;
          Call(context, callbackfn, thisArg, value, k, a);
        }
        label FoundHole {
          // If we found the hole, we need to bail out if the initial
          // array prototype has had elements inserted. This is preferable
          // to walking the prototype chain looking for elements.

          if (IsNoElementsProtectorCellInvalid()) goto Bailout(k);
        }
      }
    }
    label Slow {
      goto Bailout(k);
    }
  }

  macro FastArrayForEach(
      context: Context, o: JSReceiver, len: Number, callbackfn: Callable,
      thisArg: Object): Object labels
  Bailout(Smi) {
    let k: Smi = 0;
    try {
      const smi_len: Smi = cast<Smi>(len) otherwise Slow;
      const a: JSArray = cast<JSArray>(o) otherwise Slow;
      const map: Map = a.map;

      if (!IsPrototypeInitialArrayPrototype(context, map)) goto Slow;
      const elementsKind: ElementsKind = map.elements_kind;
      if (!IsFastElementsKind(elementsKind)) goto Slow;

      if (IsElementsKindGreaterThan(elementsKind, HOLEY_ELEMENTS)) {
        VisitAllElements<FixedDoubleArray>(
            context, a, smi_len, callbackfn, thisArg)
        otherwise Bailout;
      } else {
        VisitAllElements<FixedArray>(context, a, smi_len, callbackfn, thisArg)
        otherwise Bailout;
      }
    }
    label Slow {
      goto Bailout(k);
    }
    return Undefined;
  }

  // https://tc39.github.io/ecma262/#sec-array.prototype.foreach
  javascript builtin ArrayForEach(
      context: Context, receiver: Object, ...arguments): Object {
    try {
      if (IsNullOrUndefined(receiver)) {
        goto NullOrUndefinedError;
      }

      // 1. Let O be ? ToObject(this value).
      const o: JSReceiver = ToObject_Inline(context, receiver);

      // 2. Let len be ? ToLength(? Get(O, "length")).
      const len: Number = GetLengthProperty(context, o);

      // 3. If IsCallable(callbackfn) is false, throw a TypeError exception.
      if (arguments.length == 0) {
        goto TypeError;
      }
      const callbackfn: Callable =
          cast<Callable>(arguments[0]) otherwise TypeError;

      // 4. If thisArg is present, let T be thisArg; else let T be undefined.
      const thisArg: Object = arguments.length > 1 ? arguments[1] : Undefined;

      // Special cases.
      let k: Smi = 0;
      try {
        return FastArrayForEach(context, o, len, callbackfn, thisArg)
        otherwise Bailout;
      }
      label Bailout(k_value: Smi) {
        k = k_value;
      }

      return ArrayForEachTorqueContinuation(
          context, o, len, callbackfn, thisArg, k);
    }
    label TypeError {
      ThrowTypeError(context, kCalledNonCallable, arguments[0]);
    }
    label NullOrUndefinedError {
      ThrowTypeError(
          context, kCalledOnNullOrUndefined, 'Array.prototype.forEach');
    }
  }
}