src/builtins/array-map.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.

namespace array {

// Continuation for lazy deopt triggered by allocation of the result array.
transitioning javascript builtin
ArrayMapPreLoopLazyDeoptContinuation(
    js-implicit context: NativeContext, receiver: JSAny)(
    callback: JSAny, thisArg: JSAny, length: JSAny, result: JSAny): JSAny {
  const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
  const outputArray = Cast<JSReceiver>(result) otherwise unreachable;
  const numberLength = Cast<Number>(length) otherwise unreachable;

  const callbackfn = Cast<Callable>(callback)
      otherwise ThrowTypeError(MessageTemplate::kCalledNonCallable, callback);
  return ArrayMapLoopContinuation(
      jsreceiver, callbackfn, thisArg, outputArray, jsreceiver, kZero,
      numberLength);
}

transitioning javascript builtin
ArrayMapLoopEagerDeoptContinuation(
    js-implicit context: NativeContext, receiver: JSAny)(
    callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
    length: JSAny): JSAny {
  const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
  const callbackfn = Cast<Callable>(callback) otherwise unreachable;
  const outputArray = Cast<JSReceiver>(array) otherwise unreachable;
  const numberK = Cast<Number>(initialK) otherwise unreachable;
  const numberLength = Cast<Number>(length) otherwise unreachable;

  return ArrayMapLoopContinuation(
      jsreceiver, callbackfn, thisArg, outputArray, jsreceiver, numberK,
      numberLength);
}

transitioning javascript builtin
ArrayMapLoopLazyDeoptContinuation(
    js-implicit context: NativeContext, receiver: JSAny)(
    callback: JSAny, thisArg: JSAny, array: JSAny, initialK: JSAny,
    length: JSAny, result: JSAny): JSAny {
  const jsreceiver = Cast<JSReceiver>(receiver) otherwise unreachable;
  const callbackfn = Cast<Callable>(callback) otherwise unreachable;
  const outputArray = Cast<JSReceiver>(array) otherwise unreachable;
  let numberK = Cast<Number>(initialK) otherwise unreachable;
  const numberLength = Cast<Number>(length) otherwise unreachable;

  // This custom lazy deopt point is right after the callback. The continuation
  // needs to pick up at the next step, which is setting the callback result in
  // the output array. After incrementing k, we can glide into the loop
  // continuation builtin.

  // iii. Perform ? CreateDataPropertyOrThrow(A, Pk, mappedValue).
  FastCreateDataProperty(outputArray, numberK, result);

  // 7d. Increase k by 1.
  numberK = numberK + 1;

  return ArrayMapLoopContinuation(
      jsreceiver, callbackfn, thisArg, outputArray, jsreceiver, numberK,
      numberLength);
}

transitioning builtin ArrayMapLoopContinuation(implicit context: Context)(
    _receiver: JSReceiver, callbackfn: Callable, thisArg: JSAny,
    array: JSReceiver, o: JSReceiver, initialK: Number, length: Number): JSAny {
  // 6. Let k be 0.
  // 7. Repeat, while k < len
  for (let k: Number = initialK; k < length; k++) {
    // 7a. Let Pk be ! ToString(k).
    // k is guaranteed to be a positive integer, hence ToString is
    // side-effect free and HasProperty/GetProperty do the conversion inline.

    // 7b. Let kPresent be ? HasProperty(O, Pk).
    const kPresent: Boolean = HasProperty_Inline(o, k);

    // 7c. If kPresent is true, then:
    if (kPresent == True) {
      //  i. Let kValue be ? Get(O, Pk).
      const kValue: JSAny = GetProperty(o, k);

      // ii. Let mapped_value be ? Call(callbackfn, T, kValue, k, O).
      const mappedValue: JSAny =
          Call(context, callbackfn, thisArg, kValue, k, o);

      // iii. Perform ? CreateDataPropertyOrThrow(A, Pk, mapped_value).
      FastCreateDataProperty(array, k, mappedValue);
    }

    // 7d. Increase k by 1. (done by the loop).
  }

  // 8. Return A.
  return array;
}

struct Vector {
  macro ReportSkippedElement() {
    this.skippedElements = true;
  }

  macro CreateJSArray(implicit context: Context)(validLength: Smi): JSArray {
    const length: Smi = this.fixedArray.length;
    assert(validLength <= length);
    let kind: ElementsKind = ElementsKind::PACKED_SMI_ELEMENTS;
    if (!this.onlySmis) {
      if (this.onlyNumbers) {
        kind = ElementsKind::PACKED_DOUBLE_ELEMENTS;
      } else {
        kind = ElementsKind::PACKED_ELEMENTS;
      }
    }

    if (this.skippedElements || validLength < length) {
      // We also need to create a holey output array if we are
      // bailing out of the fast path partway through the array.
      // This is indicated by {validLength} < {length}.
      // Who knows if the bailout condition will continue to fill in
      // every element?
      kind = FastHoleyElementsKind(kind);
    }

    const map: Map = LoadJSArrayElementsMap(kind, LoadNativeContext(context));
    let a: JSArray;

    if (IsDoubleElementsKind(kind)) {
      // We need to allocate and copy.
      // First, initialize the elements field before allocation to prevent
      // heap corruption.
      const elements: FixedDoubleArray = AllocateFixedDoubleArrayWithHoles(
          SmiUntag(length), AllocationFlag::kAllowLargeObjectAllocation);
      a = NewJSArray(map, this.fixedArray);
      for (let i: Smi = 0; i < validLength; i++) {
        typeswitch (
            UnsafeCast<(Number | TheHole)>(this.fixedArray.objects[i])) {
          case (n: Number): {
            elements.floats[i] = Convert<float64_or_hole>(n);
          }
          case (TheHole): {
          }
        }
      }
      a.elements = elements;
    } else {
      // Simply install the given fixedArray in {vector}.
      a = NewJSArray(map, this.fixedArray);
    }

    // Paranoia. the FixedArray now "belongs" to JSArray {a}.
    this.fixedArray = kEmptyFixedArray;
    return a;
  }

  macro StoreResult(implicit context: Context)(index: Smi, result: JSAny) {
    typeswitch (result) {
      case (s: Smi): {
        this.fixedArray.objects[index] = s;
      }
      case (s: HeapNumber): {
        this.onlySmis = false;
        this.fixedArray.objects[index] = s;
      }
      case (s: JSAnyNotNumber): {
        this.onlySmis = false;
        this.onlyNumbers = false;
        this.fixedArray.objects[index] = s;
      }
    }
  }

  fixedArray: FixedArray;
  onlySmis: bool;         // initially true.
  onlyNumbers: bool;      // initially true.
  skippedElements: bool;  // initially false.
}

macro NewVector(implicit context: Context)(length: Smi): Vector {
  const fixedArray = length > 0 ?
      AllocateFixedArrayWithHoles(
          SmiUntag(length), AllocationFlag::kAllowLargeObjectAllocation) :
      kEmptyFixedArray;
  return Vector{
    fixedArray,
    onlySmis: true,
    onlyNumbers: true,
    skippedElements: false
  };
}

transitioning macro FastArrayMap(implicit context: Context)(
    fastO: FastJSArrayForRead, len: Smi, callbackfn: Callable,
    thisArg: JSAny): JSArray
    labels Bailout(JSArray, Smi) {
  let k: Smi = 0;
  let fastOW = NewFastJSArrayForReadWitness(fastO);
  let vector = NewVector(len);

  // Build a fast loop over the smi array.
  // 7. Repeat, while k < len.
  try {
    for (; k < len; k++) {
      fastOW.Recheck() otherwise goto PrepareBailout(k);

      // Ensure that we haven't walked beyond a possibly updated length.
      if (k >= fastOW.Get().length) goto PrepareBailout(k);

      try {
        const value: JSAny = fastOW.LoadElementNoHole(k)
            otherwise FoundHole;
        const result: JSAny =
            Call(context, callbackfn, thisArg, value, k, fastOW.Get());
        vector.StoreResult(k, result);
      } label FoundHole {
        // Our output array must necessarily be holey because of holes in
        // the input array.
        vector.ReportSkippedElement();
      }
    }
  } label PrepareBailout(k: Smi) deferred {
    // Transform {vector} into a JSArray and bail out.
    goto Bailout(vector.CreateJSArray(k), k);
  }

  return vector.CreateJSArray(len);
}

// https://tc39.github.io/ecma262/#sec-array.prototype.map
transitioning javascript builtin
ArrayMap(
    js-implicit context: NativeContext, receiver: JSAny)(...arguments): JSAny {
  try {
    RequireObjectCoercible(receiver, 'Array.prototype.map');

    // 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(o);

    // 3. If IsCallable(callbackfn) is false, throw a TypeError exception.
    if (arguments.length == 0) goto TypeError;

    const callbackfn = Cast<Callable>(arguments[0]) otherwise TypeError;

    // 4. If thisArg is present, let T be thisArg; else let T be undefined.
    const thisArg: JSAny = arguments[1];

    let array: JSReceiver;
    let k: Number = 0;
    try {
      // 5. Let A be ? ArraySpeciesCreate(O, len).
      if (IsArraySpeciesProtectorCellInvalid()) goto SlowSpeciesCreate;
      const o: FastJSArrayForRead = Cast<FastJSArrayForRead>(receiver)
          otherwise SlowSpeciesCreate;
      const smiLength: Smi = Cast<Smi>(len)
          otherwise SlowSpeciesCreate;

      return FastArrayMap(o, smiLength, callbackfn, thisArg)
          otherwise Bailout;
    } label SlowSpeciesCreate {
      array = ArraySpeciesCreate(context, receiver, len);
    } label Bailout(output: JSArray, kValue: Smi) deferred {
      array = output;
      k = kValue;
    }

    return ArrayMapLoopContinuation(o, callbackfn, thisArg, array, o, k, len);
  } label TypeError deferred {
    ThrowTypeError(MessageTemplate::kCalledNonCallable, arguments[0]);
  }
}
}