runtime-array.cc 48.2 KB
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// Copyright 2014 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/v8.h"

#include "src/arguments.h"
#include "src/runtime/runtime-utils.h"

namespace v8 {
namespace internal {

RUNTIME_FUNCTION(Runtime_FinishArrayPrototypeSetup) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 1);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, prototype, 0);
  Object* length = prototype->length();
  RUNTIME_ASSERT(length->IsSmi() && Smi::cast(length)->value() == 0);
  RUNTIME_ASSERT(prototype->HasFastSmiOrObjectElements());
  // This is necessary to enable fast checks for absence of elements
  // on Array.prototype and below.
  prototype->set_elements(isolate->heap()->empty_fixed_array());
  return Smi::FromInt(0);
}


static void InstallBuiltin(Isolate* isolate, Handle<JSObject> holder,
                           const char* name, Builtins::Name builtin_name) {
  Handle<String> key = isolate->factory()->InternalizeUtf8String(name);
  Handle<Code> code(isolate->builtins()->builtin(builtin_name));
  Handle<JSFunction> optimized =
      isolate->factory()->NewFunctionWithoutPrototype(key, code);
  optimized->shared()->DontAdaptArguments();
  JSObject::AddProperty(holder, key, optimized, NONE);
}


RUNTIME_FUNCTION(Runtime_SpecialArrayFunctions) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 0);
  Handle<JSObject> holder =
      isolate->factory()->NewJSObject(isolate->object_function());

  InstallBuiltin(isolate, holder, "pop", Builtins::kArrayPop);
  InstallBuiltin(isolate, holder, "push", Builtins::kArrayPush);
  InstallBuiltin(isolate, holder, "shift", Builtins::kArrayShift);
  InstallBuiltin(isolate, holder, "unshift", Builtins::kArrayUnshift);
  InstallBuiltin(isolate, holder, "slice", Builtins::kArraySlice);
  InstallBuiltin(isolate, holder, "splice", Builtins::kArraySplice);
  InstallBuiltin(isolate, holder, "concat", Builtins::kArrayConcat);

  return *holder;
}


RUNTIME_FUNCTION(Runtime_TransitionElementsKind) {
  HandleScope scope(isolate);
  RUNTIME_ASSERT(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
  CONVERT_ARG_HANDLE_CHECKED(Map, map, 1);
  JSObject::TransitionElementsKind(array, map->elements_kind());
  return *array;
}


// Push an object unto an array of objects if it is not already in the
// array.  Returns true if the element was pushed on the stack and
// false otherwise.
RUNTIME_FUNCTION(Runtime_PushIfAbsent) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, element, 1);
  RUNTIME_ASSERT(array->HasFastSmiOrObjectElements());
  int length = Smi::cast(array->length())->value();
  FixedArray* elements = FixedArray::cast(array->elements());
  for (int i = 0; i < length; i++) {
    if (elements->get(i) == *element) return isolate->heap()->false_value();
  }

  // Strict not needed. Used for cycle detection in Array join implementation.
  RETURN_FAILURE_ON_EXCEPTION(
      isolate, JSObject::SetFastElement(array, length, element, SLOPPY, true));
  return isolate->heap()->true_value();
}


/**
 * A simple visitor visits every element of Array's.
 * The backend storage can be a fixed array for fast elements case,
 * or a dictionary for sparse array. Since Dictionary is a subtype
 * of FixedArray, the class can be used by both fast and slow cases.
 * The second parameter of the constructor, fast_elements, specifies
 * whether the storage is a FixedArray or Dictionary.
 *
 * An index limit is used to deal with the situation that a result array
 * length overflows 32-bit non-negative integer.
 */
class ArrayConcatVisitor {
 public:
  ArrayConcatVisitor(Isolate* isolate, Handle<FixedArray> storage,
                     bool fast_elements)
      : isolate_(isolate),
        storage_(Handle<FixedArray>::cast(
            isolate->global_handles()->Create(*storage))),
        index_offset_(0u),
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        bit_field_(FastElementsField::encode(fast_elements) |
                   ExceedsLimitField::encode(false)) {}
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  ~ArrayConcatVisitor() { clear_storage(); }

  void visit(uint32_t i, Handle<Object> elm) {
    if (i > JSObject::kMaxElementCount - index_offset_) {
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      set_exceeds_array_limit(true);
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      return;
    }
    uint32_t index = index_offset_ + i;

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    if (fast_elements()) {
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      if (index < static_cast<uint32_t>(storage_->length())) {
        storage_->set(index, *elm);
        return;
      }
      // Our initial estimate of length was foiled, possibly by
      // getters on the arrays increasing the length of later arrays
      // during iteration.
      // This shouldn't happen in anything but pathological cases.
      SetDictionaryMode();
      // Fall-through to dictionary mode.
    }
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    DCHECK(!fast_elements());
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    Handle<SeededNumberDictionary> dict(
        SeededNumberDictionary::cast(*storage_));
    Handle<SeededNumberDictionary> result =
        SeededNumberDictionary::AtNumberPut(dict, index, elm);
    if (!result.is_identical_to(dict)) {
      // Dictionary needed to grow.
      clear_storage();
      set_storage(*result);
    }
  }

  void increase_index_offset(uint32_t delta) {
    if (JSObject::kMaxElementCount - index_offset_ < delta) {
      index_offset_ = JSObject::kMaxElementCount;
    } else {
      index_offset_ += delta;
    }
    // If the initial length estimate was off (see special case in visit()),
    // but the array blowing the limit didn't contain elements beyond the
    // provided-for index range, go to dictionary mode now.
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    if (fast_elements() &&
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        index_offset_ >
            static_cast<uint32_t>(FixedArrayBase::cast(*storage_)->length())) {
      SetDictionaryMode();
    }
  }

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  bool exceeds_array_limit() const {
    return ExceedsLimitField::decode(bit_field_);
  }
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  Handle<JSArray> ToArray() {
    Handle<JSArray> array = isolate_->factory()->NewJSArray(0);
    Handle<Object> length =
        isolate_->factory()->NewNumber(static_cast<double>(index_offset_));
    Handle<Map> map = JSObject::GetElementsTransitionMap(
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        array, fast_elements() ? FAST_HOLEY_ELEMENTS : DICTIONARY_ELEMENTS);
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    array->set_map(*map);
    array->set_length(*length);
    array->set_elements(*storage_);
    return array;
  }

 private:
  // Convert storage to dictionary mode.
  void SetDictionaryMode() {
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    DCHECK(fast_elements());
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    Handle<FixedArray> current_storage(*storage_);
    Handle<SeededNumberDictionary> slow_storage(
        SeededNumberDictionary::New(isolate_, current_storage->length()));
    uint32_t current_length = static_cast<uint32_t>(current_storage->length());
    for (uint32_t i = 0; i < current_length; i++) {
      HandleScope loop_scope(isolate_);
      Handle<Object> element(current_storage->get(i), isolate_);
      if (!element->IsTheHole()) {
        Handle<SeededNumberDictionary> new_storage =
            SeededNumberDictionary::AtNumberPut(slow_storage, i, element);
        if (!new_storage.is_identical_to(slow_storage)) {
          slow_storage = loop_scope.CloseAndEscape(new_storage);
        }
      }
    }
    clear_storage();
    set_storage(*slow_storage);
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    set_fast_elements(false);
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  }

  inline void clear_storage() {
    GlobalHandles::Destroy(Handle<Object>::cast(storage_).location());
  }

  inline void set_storage(FixedArray* storage) {
    storage_ =
        Handle<FixedArray>::cast(isolate_->global_handles()->Create(storage));
  }

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  class FastElementsField : public BitField<bool, 0, 1> {};
  class ExceedsLimitField : public BitField<bool, 1, 1> {};

  bool fast_elements() const { return FastElementsField::decode(bit_field_); }
  void set_fast_elements(bool fast) {
    bit_field_ = FastElementsField::update(bit_field_, fast);
  }
  void set_exceeds_array_limit(bool exceeds) {
    bit_field_ = ExceedsLimitField::update(bit_field_, exceeds);
  }

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  Isolate* isolate_;
  Handle<FixedArray> storage_;  // Always a global handle.
  // Index after last seen index. Always less than or equal to
  // JSObject::kMaxElementCount.
  uint32_t index_offset_;
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  uint32_t bit_field_;
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};


static uint32_t EstimateElementCount(Handle<JSArray> array) {
  uint32_t length = static_cast<uint32_t>(array->length()->Number());
  int element_count = 0;
  switch (array->GetElementsKind()) {
    case FAST_SMI_ELEMENTS:
    case FAST_HOLEY_SMI_ELEMENTS:
    case FAST_ELEMENTS:
    case FAST_HOLEY_ELEMENTS: {
      // Fast elements can't have lengths that are not representable by
      // a 32-bit signed integer.
      DCHECK(static_cast<int32_t>(FixedArray::kMaxLength) >= 0);
      int fast_length = static_cast<int>(length);
      Handle<FixedArray> elements(FixedArray::cast(array->elements()));
      for (int i = 0; i < fast_length; i++) {
        if (!elements->get(i)->IsTheHole()) element_count++;
      }
      break;
    }
    case FAST_DOUBLE_ELEMENTS:
    case FAST_HOLEY_DOUBLE_ELEMENTS: {
      // Fast elements can't have lengths that are not representable by
      // a 32-bit signed integer.
      DCHECK(static_cast<int32_t>(FixedDoubleArray::kMaxLength) >= 0);
      int fast_length = static_cast<int>(length);
      if (array->elements()->IsFixedArray()) {
        DCHECK(FixedArray::cast(array->elements())->length() == 0);
        break;
      }
      Handle<FixedDoubleArray> elements(
          FixedDoubleArray::cast(array->elements()));
      for (int i = 0; i < fast_length; i++) {
        if (!elements->is_the_hole(i)) element_count++;
      }
      break;
    }
    case DICTIONARY_ELEMENTS: {
      Handle<SeededNumberDictionary> dictionary(
          SeededNumberDictionary::cast(array->elements()));
      int capacity = dictionary->Capacity();
      for (int i = 0; i < capacity; i++) {
        Handle<Object> key(dictionary->KeyAt(i), array->GetIsolate());
        if (dictionary->IsKey(*key)) {
          element_count++;
        }
      }
      break;
    }
    case SLOPPY_ARGUMENTS_ELEMENTS:
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case EXTERNAL_##TYPE##_ELEMENTS:                      \
  case TYPE##_ELEMENTS:

      TYPED_ARRAYS(TYPED_ARRAY_CASE)
#undef TYPED_ARRAY_CASE
      // External arrays are always dense.
      return length;
  }
  // As an estimate, we assume that the prototype doesn't contain any
  // inherited elements.
  return element_count;
}


template <class ExternalArrayClass, class ElementType>
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static void IterateTypedArrayElements(Isolate* isolate,
                                      Handle<JSObject> receiver,
                                      bool elements_are_ints,
                                      bool elements_are_guaranteed_smis,
                                      ArrayConcatVisitor* visitor) {
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  Handle<ExternalArrayClass> array(
      ExternalArrayClass::cast(receiver->elements()));
  uint32_t len = static_cast<uint32_t>(array->length());

  DCHECK(visitor != NULL);
  if (elements_are_ints) {
    if (elements_are_guaranteed_smis) {
      for (uint32_t j = 0; j < len; j++) {
        HandleScope loop_scope(isolate);
        Handle<Smi> e(Smi::FromInt(static_cast<int>(array->get_scalar(j))),
                      isolate);
        visitor->visit(j, e);
      }
    } else {
      for (uint32_t j = 0; j < len; j++) {
        HandleScope loop_scope(isolate);
        int64_t val = static_cast<int64_t>(array->get_scalar(j));
        if (Smi::IsValid(static_cast<intptr_t>(val))) {
          Handle<Smi> e(Smi::FromInt(static_cast<int>(val)), isolate);
          visitor->visit(j, e);
        } else {
          Handle<Object> e =
              isolate->factory()->NewNumber(static_cast<ElementType>(val));
          visitor->visit(j, e);
        }
      }
    }
  } else {
    for (uint32_t j = 0; j < len; j++) {
      HandleScope loop_scope(isolate);
      Handle<Object> e = isolate->factory()->NewNumber(array->get_scalar(j));
      visitor->visit(j, e);
    }
  }
}


// Used for sorting indices in a List<uint32_t>.
static int compareUInt32(const uint32_t* ap, const uint32_t* bp) {
  uint32_t a = *ap;
  uint32_t b = *bp;
  return (a == b) ? 0 : (a < b) ? -1 : 1;
}


static void CollectElementIndices(Handle<JSObject> object, uint32_t range,
                                  List<uint32_t>* indices) {
  Isolate* isolate = object->GetIsolate();
  ElementsKind kind = object->GetElementsKind();
  switch (kind) {
    case FAST_SMI_ELEMENTS:
    case FAST_ELEMENTS:
    case FAST_HOLEY_SMI_ELEMENTS:
    case FAST_HOLEY_ELEMENTS: {
      Handle<FixedArray> elements(FixedArray::cast(object->elements()));
      uint32_t length = static_cast<uint32_t>(elements->length());
      if (range < length) length = range;
      for (uint32_t i = 0; i < length; i++) {
        if (!elements->get(i)->IsTheHole()) {
          indices->Add(i);
        }
      }
      break;
    }
    case FAST_HOLEY_DOUBLE_ELEMENTS:
    case FAST_DOUBLE_ELEMENTS: {
      if (object->elements()->IsFixedArray()) {
        DCHECK(object->elements()->length() == 0);
        break;
      }
      Handle<FixedDoubleArray> elements(
          FixedDoubleArray::cast(object->elements()));
      uint32_t length = static_cast<uint32_t>(elements->length());
      if (range < length) length = range;
      for (uint32_t i = 0; i < length; i++) {
        if (!elements->is_the_hole(i)) {
          indices->Add(i);
        }
      }
      break;
    }
    case DICTIONARY_ELEMENTS: {
      Handle<SeededNumberDictionary> dict(
          SeededNumberDictionary::cast(object->elements()));
      uint32_t capacity = dict->Capacity();
      for (uint32_t j = 0; j < capacity; j++) {
        HandleScope loop_scope(isolate);
        Handle<Object> k(dict->KeyAt(j), isolate);
        if (dict->IsKey(*k)) {
          DCHECK(k->IsNumber());
          uint32_t index = static_cast<uint32_t>(k->Number());
          if (index < range) {
            indices->Add(index);
          }
        }
      }
      break;
    }
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case TYPE##_ELEMENTS:                                 \
  case EXTERNAL_##TYPE##_ELEMENTS:

      TYPED_ARRAYS(TYPED_ARRAY_CASE)
#undef TYPED_ARRAY_CASE
      {
        uint32_t length = static_cast<uint32_t>(
            FixedArrayBase::cast(object->elements())->length());
        if (range <= length) {
          length = range;
          // We will add all indices, so we might as well clear it first
          // and avoid duplicates.
          indices->Clear();
        }
        for (uint32_t i = 0; i < length; i++) {
          indices->Add(i);
        }
        if (length == range) return;  // All indices accounted for already.
        break;
      }
    case SLOPPY_ARGUMENTS_ELEMENTS: {
      MaybeHandle<Object> length_obj =
          Object::GetProperty(object, isolate->factory()->length_string());
      double length_num = length_obj.ToHandleChecked()->Number();
      uint32_t length = static_cast<uint32_t>(DoubleToInt32(length_num));
      ElementsAccessor* accessor = object->GetElementsAccessor();
      for (uint32_t i = 0; i < length; i++) {
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        if (accessor->HasElement(object, i)) {
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          indices->Add(i);
        }
      }
      break;
    }
  }

  PrototypeIterator iter(isolate, object);
  if (!iter.IsAtEnd()) {
    // The prototype will usually have no inherited element indices,
    // but we have to check.
    CollectElementIndices(
        Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)), range,
        indices);
  }
}


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static bool IterateElementsSlow(Isolate* isolate, Handle<JSObject> receiver,
                                uint32_t length, ArrayConcatVisitor* visitor) {
  for (uint32_t i = 0; i < length; ++i) {
    HandleScope loop_scope(isolate);
    Maybe<bool> maybe = JSReceiver::HasElement(receiver, i);
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    if (!maybe.IsJust()) return false;
    if (maybe.FromJust()) {
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      Handle<Object> element_value;
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(
          isolate, element_value,
          Runtime::GetElementOrCharAt(isolate, receiver, i), false);
      visitor->visit(i, element_value);
    }
  }
  visitor->increase_index_offset(length);
  return true;
}


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/**
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 * A helper function that visits elements of a JSObject in numerical
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 * order.
 *
 * The visitor argument called for each existing element in the array
 * with the element index and the element's value.
 * Afterwards it increments the base-index of the visitor by the array
 * length.
 * Returns false if any access threw an exception, otherwise true.
 */
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static bool IterateElements(Isolate* isolate, Handle<JSObject> receiver,
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                            ArrayConcatVisitor* visitor) {
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  uint32_t length = 0;

  if (receiver->IsJSArray()) {
    Handle<JSArray> array(Handle<JSArray>::cast(receiver));
    length = static_cast<uint32_t>(array->length()->Number());
  } else {
    Handle<Object> val;
    Handle<Object> key(isolate->heap()->length_string(), isolate);
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
        Runtime::GetObjectProperty(isolate, receiver, key), false);
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    // TODO(caitp): Support larger element indexes (up to 2^53-1).
    if (!val->ToUint32(&length)) {
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
          Execution::ToLength(isolate, val), false);
      val->ToUint32(&length);
    }
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  }

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  if (!(receiver->IsJSArray() || receiver->IsJSTypedArray())) {
    // For classes which are not known to be safe to access via elements alone,
    // use the slow case.
    return IterateElementsSlow(isolate, receiver, length, visitor);
  }

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  switch (receiver->GetElementsKind()) {
    case FAST_SMI_ELEMENTS:
    case FAST_ELEMENTS:
    case FAST_HOLEY_SMI_ELEMENTS:
    case FAST_HOLEY_ELEMENTS: {
      // Run through the elements FixedArray and use HasElement and GetElement
      // to check the prototype for missing elements.
      Handle<FixedArray> elements(FixedArray::cast(receiver->elements()));
      int fast_length = static_cast<int>(length);
      DCHECK(fast_length <= elements->length());
      for (int j = 0; j < fast_length; j++) {
        HandleScope loop_scope(isolate);
        Handle<Object> element_value(elements->get(j), isolate);
        if (!element_value->IsTheHole()) {
          visitor->visit(j, element_value);
        } else {
          Maybe<bool> maybe = JSReceiver::HasElement(receiver, j);
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          if (!maybe.IsJust()) return false;
          if (maybe.FromJust()) {
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            // Call GetElement on receiver, not its prototype, or getters won't
            // have the correct receiver.
            ASSIGN_RETURN_ON_EXCEPTION_VALUE(
                isolate, element_value,
                Object::GetElement(isolate, receiver, j), false);
            visitor->visit(j, element_value);
          }
        }
      }
      break;
    }
    case FAST_HOLEY_DOUBLE_ELEMENTS:
    case FAST_DOUBLE_ELEMENTS: {
      // Empty array is FixedArray but not FixedDoubleArray.
      if (length == 0) break;
      // Run through the elements FixedArray and use HasElement and GetElement
      // to check the prototype for missing elements.
      if (receiver->elements()->IsFixedArray()) {
        DCHECK(receiver->elements()->length() == 0);
        break;
      }
      Handle<FixedDoubleArray> elements(
          FixedDoubleArray::cast(receiver->elements()));
      int fast_length = static_cast<int>(length);
      DCHECK(fast_length <= elements->length());
      for (int j = 0; j < fast_length; j++) {
        HandleScope loop_scope(isolate);
        if (!elements->is_the_hole(j)) {
          double double_value = elements->get_scalar(j);
          Handle<Object> element_value =
              isolate->factory()->NewNumber(double_value);
          visitor->visit(j, element_value);
        } else {
          Maybe<bool> maybe = JSReceiver::HasElement(receiver, j);
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          if (!maybe.IsJust()) return false;
          if (maybe.FromJust()) {
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            // Call GetElement on receiver, not its prototype, or getters won't
            // have the correct receiver.
            Handle<Object> element_value;
            ASSIGN_RETURN_ON_EXCEPTION_VALUE(
                isolate, element_value,
                Object::GetElement(isolate, receiver, j), false);
            visitor->visit(j, element_value);
          }
        }
      }
      break;
    }
    case DICTIONARY_ELEMENTS: {
      Handle<SeededNumberDictionary> dict(receiver->element_dictionary());
      List<uint32_t> indices(dict->Capacity() / 2);
      // Collect all indices in the object and the prototypes less
      // than length. This might introduce duplicates in the indices list.
      CollectElementIndices(receiver, length, &indices);
      indices.Sort(&compareUInt32);
      int j = 0;
      int n = indices.length();
      while (j < n) {
        HandleScope loop_scope(isolate);
        uint32_t index = indices[j];
        Handle<Object> element;
        ASSIGN_RETURN_ON_EXCEPTION_VALUE(
            isolate, element, Object::GetElement(isolate, receiver, index),
            false);
        visitor->visit(index, element);
        // Skip to next different index (i.e., omit duplicates).
        do {
          j++;
        } while (j < n && indices[j] == index);
      }
      break;
    }
    case EXTERNAL_UINT8_CLAMPED_ELEMENTS: {
      Handle<ExternalUint8ClampedArray> pixels(
          ExternalUint8ClampedArray::cast(receiver->elements()));
      for (uint32_t j = 0; j < length; j++) {
        Handle<Smi> e(Smi::FromInt(pixels->get_scalar(j)), isolate);
        visitor->visit(j, e);
      }
      break;
    }
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    case UINT8_CLAMPED_ELEMENTS: {
      Handle<FixedUint8ClampedArray> pixels(
      FixedUint8ClampedArray::cast(receiver->elements()));
      for (uint32_t j = 0; j < length; j++) {
        Handle<Smi> e(Smi::FromInt(pixels->get_scalar(j)), isolate);
        visitor->visit(j, e);
      }
      break;
    }
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    case EXTERNAL_INT8_ELEMENTS: {
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      IterateTypedArrayElements<ExternalInt8Array, int8_t>(
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          isolate, receiver, true, true, visitor);
      break;
    }
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    case INT8_ELEMENTS: {
      IterateTypedArrayElements<FixedInt8Array, int8_t>(
      isolate, receiver, true, true, visitor);
      break;
    }
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    case EXTERNAL_UINT8_ELEMENTS: {
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      IterateTypedArrayElements<ExternalUint8Array, uint8_t>(
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          isolate, receiver, true, true, visitor);
      break;
    }
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    case UINT8_ELEMENTS: {
      IterateTypedArrayElements<FixedUint8Array, uint8_t>(
      isolate, receiver, true, true, visitor);
      break;
    }
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    case EXTERNAL_INT16_ELEMENTS: {
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      IterateTypedArrayElements<ExternalInt16Array, int16_t>(
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          isolate, receiver, true, true, visitor);
      break;
    }
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    case INT16_ELEMENTS: {
      IterateTypedArrayElements<FixedInt16Array, int16_t>(
      isolate, receiver, true, true, visitor);
      break;
    }
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    case EXTERNAL_UINT16_ELEMENTS: {
637
      IterateTypedArrayElements<ExternalUint16Array, uint16_t>(
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          isolate, receiver, true, true, visitor);
      break;
    }
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    case UINT16_ELEMENTS: {
      IterateTypedArrayElements<FixedUint16Array, uint16_t>(
      isolate, receiver, true, true, visitor);
      break;
    }
646
    case EXTERNAL_INT32_ELEMENTS: {
647
      IterateTypedArrayElements<ExternalInt32Array, int32_t>(
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          isolate, receiver, true, false, visitor);
      break;
    }
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    case INT32_ELEMENTS: {
      IterateTypedArrayElements<FixedInt32Array, int32_t>(
      isolate, receiver, true, false, visitor);
      break;
    }
656
    case EXTERNAL_UINT32_ELEMENTS: {
657
      IterateTypedArrayElements<ExternalUint32Array, uint32_t>(
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          isolate, receiver, true, false, visitor);
      break;
    }
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    case UINT32_ELEMENTS: {
      IterateTypedArrayElements<FixedUint32Array, uint32_t>(
      isolate, receiver, true, false, visitor);
      break;
    }
666
    case EXTERNAL_FLOAT32_ELEMENTS: {
667
      IterateTypedArrayElements<ExternalFloat32Array, float>(
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          isolate, receiver, false, false, visitor);
      break;
    }
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    case FLOAT32_ELEMENTS: {
      IterateTypedArrayElements<FixedFloat32Array, float>(
      isolate, receiver, false, false, visitor);
      break;
    }
676
    case EXTERNAL_FLOAT64_ELEMENTS: {
677
      IterateTypedArrayElements<ExternalFloat64Array, double>(
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          isolate, receiver, false, false, visitor);
      break;
    }
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    case FLOAT64_ELEMENTS: {
      IterateTypedArrayElements<FixedFloat64Array, double>(
      isolate, receiver, false, false, visitor);
684
      break;
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    }
    case SLOPPY_ARGUMENTS_ELEMENTS: {
      ElementsAccessor* accessor = receiver->GetElementsAccessor();
      for (uint32_t index = 0; index < length; index++) {
        HandleScope loop_scope(isolate);
690
        if (accessor->HasElement(receiver, index)) {
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          Handle<Object> element;
          ASSIGN_RETURN_ON_EXCEPTION_VALUE(
              isolate, element, accessor->Get(receiver, receiver, index),
              false);
          visitor->visit(index, element);
        }
      }
      break;
    }
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  }
  visitor->increase_index_offset(length);
  return true;
}


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static bool IsConcatSpreadable(Isolate* isolate, Handle<Object> obj) {
  HandleScope handle_scope(isolate);
  if (!obj->IsSpecObject()) return false;
  if (obj->IsJSArray()) return true;
  if (FLAG_harmony_arrays) {
    Handle<Symbol> key(isolate->factory()->is_concat_spreadable_symbol());
    Handle<Object> value;
    MaybeHandle<Object> maybeValue =
        i::Runtime::GetObjectProperty(isolate, obj, key);
    if (maybeValue.ToHandle(&value)) {
      return value->BooleanValue();
    }
  }
  return false;
}


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/**
 * Array::concat implementation.
 * See ECMAScript 262, 15.4.4.4.
 * TODO(581): Fix non-compliance for very large concatenations and update to
 * following the ECMAScript 5 specification.
 */
RUNTIME_FUNCTION(Runtime_ArrayConcat) {
  HandleScope handle_scope(isolate);
  DCHECK(args.length() == 1);

  CONVERT_ARG_HANDLE_CHECKED(JSArray, arguments, 0);
  int argument_count = static_cast<int>(arguments->length()->Number());
  RUNTIME_ASSERT(arguments->HasFastObjectElements());
  Handle<FixedArray> elements(FixedArray::cast(arguments->elements()));

  // Pass 1: estimate the length and number of elements of the result.
  // The actual length can be larger if any of the arguments have getters
  // that mutate other arguments (but will otherwise be precise).
  // The number of elements is precise if there are no inherited elements.

  ElementsKind kind = FAST_SMI_ELEMENTS;

  uint32_t estimate_result_length = 0;
  uint32_t estimate_nof_elements = 0;
  for (int i = 0; i < argument_count; i++) {
    HandleScope loop_scope(isolate);
    Handle<Object> obj(elements->get(i), isolate);
    uint32_t length_estimate;
    uint32_t element_estimate;
    if (obj->IsJSArray()) {
      Handle<JSArray> array(Handle<JSArray>::cast(obj));
      length_estimate = static_cast<uint32_t>(array->length()->Number());
      if (length_estimate != 0) {
        ElementsKind array_kind =
            GetPackedElementsKind(array->map()->elements_kind());
        if (IsMoreGeneralElementsKindTransition(kind, array_kind)) {
          kind = array_kind;
        }
      }
      element_estimate = EstimateElementCount(array);
    } else {
      if (obj->IsHeapObject()) {
        if (obj->IsNumber()) {
          if (IsMoreGeneralElementsKindTransition(kind, FAST_DOUBLE_ELEMENTS)) {
            kind = FAST_DOUBLE_ELEMENTS;
          }
        } else if (IsMoreGeneralElementsKindTransition(kind, FAST_ELEMENTS)) {
          kind = FAST_ELEMENTS;
        }
      }
      length_estimate = 1;
      element_estimate = 1;
    }
    // Avoid overflows by capping at kMaxElementCount.
    if (JSObject::kMaxElementCount - estimate_result_length < length_estimate) {
      estimate_result_length = JSObject::kMaxElementCount;
    } else {
      estimate_result_length += length_estimate;
    }
    if (JSObject::kMaxElementCount - estimate_nof_elements < element_estimate) {
      estimate_nof_elements = JSObject::kMaxElementCount;
    } else {
      estimate_nof_elements += element_estimate;
    }
  }

  // If estimated number of elements is more than half of length, a
  // fixed array (fast case) is more time and space-efficient than a
  // dictionary.
  bool fast_case = (estimate_nof_elements * 2) >= estimate_result_length;

  if (fast_case && kind == FAST_DOUBLE_ELEMENTS) {
    Handle<FixedArrayBase> storage =
        isolate->factory()->NewFixedDoubleArray(estimate_result_length);
    int j = 0;
    bool failure = false;
    if (estimate_result_length > 0) {
      Handle<FixedDoubleArray> double_storage =
          Handle<FixedDoubleArray>::cast(storage);
      for (int i = 0; i < argument_count; i++) {
        Handle<Object> obj(elements->get(i), isolate);
        if (obj->IsSmi()) {
          double_storage->set(j, Smi::cast(*obj)->value());
          j++;
        } else if (obj->IsNumber()) {
          double_storage->set(j, obj->Number());
          j++;
        } else {
          JSArray* array = JSArray::cast(*obj);
          uint32_t length = static_cast<uint32_t>(array->length()->Number());
          switch (array->map()->elements_kind()) {
            case FAST_HOLEY_DOUBLE_ELEMENTS:
            case FAST_DOUBLE_ELEMENTS: {
              // Empty array is FixedArray but not FixedDoubleArray.
              if (length == 0) break;
              FixedDoubleArray* elements =
                  FixedDoubleArray::cast(array->elements());
              for (uint32_t i = 0; i < length; i++) {
                if (elements->is_the_hole(i)) {
                  // TODO(jkummerow/verwaest): We could be a bit more clever
                  // here: Check if there are no elements/getters on the
                  // prototype chain, and if so, allow creation of a holey
                  // result array.
                  // Same thing below (holey smi case).
                  failure = true;
                  break;
                }
                double double_value = elements->get_scalar(i);
                double_storage->set(j, double_value);
                j++;
              }
              break;
            }
            case FAST_HOLEY_SMI_ELEMENTS:
            case FAST_SMI_ELEMENTS: {
              FixedArray* elements(FixedArray::cast(array->elements()));
              for (uint32_t i = 0; i < length; i++) {
                Object* element = elements->get(i);
                if (element->IsTheHole()) {
                  failure = true;
                  break;
                }
                int32_t int_value = Smi::cast(element)->value();
                double_storage->set(j, int_value);
                j++;
              }
              break;
            }
            case FAST_HOLEY_ELEMENTS:
            case FAST_ELEMENTS:
853
            case DICTIONARY_ELEMENTS:
854
              DCHECK_EQ(0u, length);
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              break;
            default:
              UNREACHABLE();
          }
        }
        if (failure) break;
      }
    }
    if (!failure) {
      Handle<JSArray> array = isolate->factory()->NewJSArray(0);
      Smi* length = Smi::FromInt(j);
      Handle<Map> map;
      map = JSObject::GetElementsTransitionMap(array, kind);
      array->set_map(*map);
      array->set_length(length);
      array->set_elements(*storage);
      return *array;
    }
    // In case of failure, fall through.
  }

  Handle<FixedArray> storage;
  if (fast_case) {
    // The backing storage array must have non-existing elements to preserve
    // holes across concat operations.
    storage =
        isolate->factory()->NewFixedArrayWithHoles(estimate_result_length);
  } else {
    // TODO(126): move 25% pre-allocation logic into Dictionary::Allocate
    uint32_t at_least_space_for =
        estimate_nof_elements + (estimate_nof_elements >> 2);
    storage = Handle<FixedArray>::cast(
        SeededNumberDictionary::New(isolate, at_least_space_for));
  }

  ArrayConcatVisitor visitor(isolate, storage, fast_case);

  for (int i = 0; i < argument_count; i++) {
    Handle<Object> obj(elements->get(i), isolate);
894 895 896 897 898
    bool spreadable = IsConcatSpreadable(isolate, obj);
    if (isolate->has_pending_exception()) return isolate->heap()->exception();
    if (spreadable) {
      Handle<JSObject> object = Handle<JSObject>::cast(obj);
      if (!IterateElements(isolate, object, &visitor)) {
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        return isolate->heap()->exception();
      }
    } else {
      visitor.visit(0, obj);
      visitor.increase_index_offset(1);
    }
  }

  if (visitor.exceeds_array_limit()) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate,
        NewRangeError("invalid_array_length", HandleVector<Object>(NULL, 0)));
  }
  return *visitor.ToArray();
}


// Moves all own elements of an object, that are below a limit, to positions
// starting at zero. All undefined values are placed after non-undefined values,
// and are followed by non-existing element. Does not change the length
// property.
// Returns the number of non-undefined elements collected.
// Returns -1 if hole removal is not supported by this method.
RUNTIME_FUNCTION(Runtime_RemoveArrayHoles) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
  CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
  return *JSObject::PrepareElementsForSort(object, limit);
}


// Move contents of argument 0 (an array) to argument 1 (an array)
RUNTIME_FUNCTION(Runtime_MoveArrayContents) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, from, 0);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, to, 1);
  JSObject::ValidateElements(from);
  JSObject::ValidateElements(to);

  Handle<FixedArrayBase> new_elements(from->elements());
  ElementsKind from_kind = from->GetElementsKind();
  Handle<Map> new_map = JSObject::GetElementsTransitionMap(to, from_kind);
  JSObject::SetMapAndElements(to, new_map, new_elements);
  to->set_length(from->length());

  JSObject::ResetElements(from);
  from->set_length(Smi::FromInt(0));

  JSObject::ValidateElements(to);
  return *to;
}


// How many elements does this object/array have?
RUNTIME_FUNCTION(Runtime_EstimateNumberOfElements) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 1);
  CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
  Handle<FixedArrayBase> elements(array->elements(), isolate);
  SealHandleScope shs(isolate);
  if (elements->IsDictionary()) {
    int result =
        Handle<SeededNumberDictionary>::cast(elements)->NumberOfElements();
    return Smi::FromInt(result);
  } else {
    DCHECK(array->length()->IsSmi());
    // For packed elements, we know the exact number of elements
    int length = elements->length();
    ElementsKind kind = array->GetElementsKind();
    if (IsFastPackedElementsKind(kind)) {
      return Smi::FromInt(length);
    }
    // For holey elements, take samples from the buffer checking for holes
    // to generate the estimate.
    const int kNumberOfHoleCheckSamples = 97;
    int increment = (length < kNumberOfHoleCheckSamples)
                        ? 1
                        : static_cast<int>(length / kNumberOfHoleCheckSamples);
    ElementsAccessor* accessor = array->GetElementsAccessor();
    int holes = 0;
    for (int i = 0; i < length; i += increment) {
982
      if (!accessor->HasElement(array, i, elements)) {
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        ++holes;
      }
    }
    int estimate = static_cast<int>((kNumberOfHoleCheckSamples - holes) /
                                    kNumberOfHoleCheckSamples * length);
    return Smi::FromInt(estimate);
  }
}


// Returns an array that tells you where in the [0, length) interval an array
// might have elements.  Can either return an array of keys (positive integers
// or undefined) or a number representing the positive length of an interval
// starting at index 0.
// Intervals can span over some keys that are not in the object.
RUNTIME_FUNCTION(Runtime_GetArrayKeys) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(JSObject, array, 0);
  CONVERT_NUMBER_CHECKED(uint32_t, length, Uint32, args[1]);
  if (array->elements()->IsDictionary()) {
    Handle<FixedArray> keys = isolate->factory()->empty_fixed_array();
    for (PrototypeIterator iter(isolate, array,
                                PrototypeIterator::START_AT_RECEIVER);
         !iter.IsAtEnd(); iter.Advance()) {
      if (PrototypeIterator::GetCurrent(iter)->IsJSProxy() ||
          JSObject::cast(*PrototypeIterator::GetCurrent(iter))
              ->HasIndexedInterceptor()) {
        // Bail out if we find a proxy or interceptor, likely not worth
        // collecting keys in that case.
        return *isolate->factory()->NewNumberFromUint(length);
      }
      Handle<JSObject> current =
          Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
      Handle<FixedArray> current_keys =
          isolate->factory()->NewFixedArray(current->NumberOfOwnElements(NONE));
      current->GetOwnElementKeys(*current_keys, NONE);
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, keys, FixedArray::UnionOfKeys(keys, current_keys));
    }
    // Erase any keys >= length.
    // TODO(adamk): Remove this step when the contract of %GetArrayKeys
    // is changed to let this happen on the JS side.
    for (int i = 0; i < keys->length(); i++) {
      if (NumberToUint32(keys->get(i)) >= length) keys->set_undefined(i);
    }
    return *isolate->factory()->NewJSArrayWithElements(keys);
  } else {
    RUNTIME_ASSERT(array->HasFastSmiOrObjectElements() ||
                   array->HasFastDoubleElements());
    uint32_t actual_length = static_cast<uint32_t>(array->elements()->length());
    return *isolate->factory()->NewNumberFromUint(Min(actual_length, length));
  }
}


static Object* ArrayConstructorCommon(Isolate* isolate,
                                      Handle<JSFunction> constructor,
1041
                                      Handle<JSFunction> original_constructor,
1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112
                                      Handle<AllocationSite> site,
                                      Arguments* caller_args) {
  Factory* factory = isolate->factory();

  bool holey = false;
  bool can_use_type_feedback = true;
  if (caller_args->length() == 1) {
    Handle<Object> argument_one = caller_args->at<Object>(0);
    if (argument_one->IsSmi()) {
      int value = Handle<Smi>::cast(argument_one)->value();
      if (value < 0 || value >= JSObject::kInitialMaxFastElementArray) {
        // the array is a dictionary in this case.
        can_use_type_feedback = false;
      } else if (value != 0) {
        holey = true;
      }
    } else {
      // Non-smi length argument produces a dictionary
      can_use_type_feedback = false;
    }
  }

  Handle<JSArray> array;
  if (!site.is_null() && can_use_type_feedback) {
    ElementsKind to_kind = site->GetElementsKind();
    if (holey && !IsFastHoleyElementsKind(to_kind)) {
      to_kind = GetHoleyElementsKind(to_kind);
      // Update the allocation site info to reflect the advice alteration.
      site->SetElementsKind(to_kind);
    }

    // We should allocate with an initial map that reflects the allocation site
    // advice. Therefore we use AllocateJSObjectFromMap instead of passing
    // the constructor.
    Handle<Map> initial_map(constructor->initial_map(), isolate);
    if (to_kind != initial_map->elements_kind()) {
      initial_map = Map::AsElementsKind(initial_map, to_kind);
    }

    // If we don't care to track arrays of to_kind ElementsKind, then
    // don't emit a memento for them.
    Handle<AllocationSite> allocation_site;
    if (AllocationSite::GetMode(to_kind) == TRACK_ALLOCATION_SITE) {
      allocation_site = site;
    }

    array = Handle<JSArray>::cast(factory->NewJSObjectFromMap(
        initial_map, NOT_TENURED, true, allocation_site));
  } else {
    array = Handle<JSArray>::cast(factory->NewJSObject(constructor));

    // We might need to transition to holey
    ElementsKind kind = constructor->initial_map()->elements_kind();
    if (holey && !IsFastHoleyElementsKind(kind)) {
      kind = GetHoleyElementsKind(kind);
      JSObject::TransitionElementsKind(array, kind);
    }
  }

  factory->NewJSArrayStorage(array, 0, 0, DONT_INITIALIZE_ARRAY_ELEMENTS);

  ElementsKind old_kind = array->GetElementsKind();
  RETURN_FAILURE_ON_EXCEPTION(
      isolate, ArrayConstructInitializeElements(array, caller_args));
  if (!site.is_null() &&
      (old_kind != array->GetElementsKind() || !can_use_type_feedback)) {
    // The arguments passed in caused a transition. This kind of complexity
    // can't be dealt with in the inlined hydrogen array constructor case.
    // We must mark the allocationsite as un-inlinable.
    site->SetDoNotInlineCall();
  }
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  // Set up the prototoype using original function.
  // TODO(dslomov): instead of setting the __proto__,
  // use and cache the correct map.
  if (*original_constructor != *constructor) {
    if (original_constructor->has_instance_prototype()) {
      Handle<Object> prototype =
          handle(original_constructor->instance_prototype(), isolate);
      RETURN_FAILURE_ON_EXCEPTION(
          isolate, JSObject::SetPrototype(array, prototype, false));
    }
  }

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  return *array;
}


RUNTIME_FUNCTION(Runtime_ArrayConstructor) {
  HandleScope scope(isolate);
  // If we get 2 arguments then they are the stub parameters (constructor, type
  // info).  If we get 4, then the first one is a pointer to the arguments
  // passed by the caller, and the last one is the length of the arguments
  // passed to the caller (redundant, but useful to check on the deoptimizer
  // with an assert).
  Arguments empty_args(0, NULL);
  bool no_caller_args = args.length() == 2;
  DCHECK(no_caller_args || args.length() == 4);
  int parameters_start = no_caller_args ? 0 : 1;
  Arguments* caller_args =
      no_caller_args ? &empty_args : reinterpret_cast<Arguments*>(args[0]);
  CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, parameters_start);
  CONVERT_ARG_HANDLE_CHECKED(Object, type_info, parameters_start + 1);
#ifdef DEBUG
  if (!no_caller_args) {
    CONVERT_SMI_ARG_CHECKED(arg_count, parameters_start + 2);
    DCHECK(arg_count == caller_args->length());
  }
#endif

  Handle<AllocationSite> site;
  if (!type_info.is_null() &&
      *type_info != isolate->heap()->undefined_value()) {
    site = Handle<AllocationSite>::cast(type_info);
    DCHECK(!site->SitePointsToLiteral());
  }

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  return ArrayConstructorCommon(isolate, constructor, constructor, site,
                                caller_args);
}


RUNTIME_FUNCTION(Runtime_ArrayConstructorWithSubclassing) {
  HandleScope scope(isolate);
  int args_length = args.length();
  CHECK(args_length >= 2);

  // This variables and checks work around -Werror=strict-overflow.
  int pre_last_arg_index = args_length - 2;
  int last_arg_index = args_length - 1;
  CHECK(pre_last_arg_index >= 0);
  CHECK(last_arg_index >= 0);

  CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, pre_last_arg_index);
  CONVERT_ARG_HANDLE_CHECKED(JSFunction, original_constructor, last_arg_index);
  Arguments caller_args(args_length - 2, args.arguments());
  return ArrayConstructorCommon(isolate, constructor, original_constructor,
                                Handle<AllocationSite>::null(), &caller_args);
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}


RUNTIME_FUNCTION(Runtime_InternalArrayConstructor) {
  HandleScope scope(isolate);
  Arguments empty_args(0, NULL);
  bool no_caller_args = args.length() == 1;
  DCHECK(no_caller_args || args.length() == 3);
  int parameters_start = no_caller_args ? 0 : 1;
  Arguments* caller_args =
      no_caller_args ? &empty_args : reinterpret_cast<Arguments*>(args[0]);
  CONVERT_ARG_HANDLE_CHECKED(JSFunction, constructor, parameters_start);
#ifdef DEBUG
  if (!no_caller_args) {
    CONVERT_SMI_ARG_CHECKED(arg_count, parameters_start + 1);
    DCHECK(arg_count == caller_args->length());
  }
#endif
1198
  return ArrayConstructorCommon(isolate, constructor, constructor,
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                                Handle<AllocationSite>::null(), caller_args);
}


RUNTIME_FUNCTION(Runtime_NormalizeElements) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 1);
  CONVERT_ARG_HANDLE_CHECKED(JSObject, array, 0);
  RUNTIME_ASSERT(!array->HasExternalArrayElements() &&
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                 !array->HasFixedTypedArrayElements() &&
                 !array->IsJSGlobalProxy());
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  JSObject::NormalizeElements(array);
  return *array;
}


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RUNTIME_FUNCTION(Runtime_HasComplexElements) {
  HandleScope scope(isolate);
  DCHECK(args.length() == 1);
  CONVERT_ARG_HANDLE_CHECKED(JSObject, array, 0);
  for (PrototypeIterator iter(isolate, array,
                              PrototypeIterator::START_AT_RECEIVER);
       !iter.IsAtEnd(); iter.Advance()) {
    if (PrototypeIterator::GetCurrent(iter)->IsJSProxy()) {
      return isolate->heap()->true_value();
    }
    Handle<JSObject> current =
        Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
    if (current->HasIndexedInterceptor()) {
      return isolate->heap()->true_value();
    }
    if (!current->HasDictionaryElements()) continue;
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    if (current->element_dictionary()
            ->HasComplexElements<DictionaryEntryType::kObjects>()) {
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      return isolate->heap()->true_value();
    }
  }
  return isolate->heap()->false_value();
}


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// TODO(dcarney): remove this function when TurboFan supports it.
// Takes the object to be iterated over and the result of GetPropertyNamesFast
// Returns pair (cache_array, cache_type).
RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ForInInit) {
  SealHandleScope scope(isolate);
  DCHECK(args.length() == 2);
  // This simulates CONVERT_ARG_HANDLE_CHECKED for calls returning pairs.
  // Not worth creating a macro atm as this function should be removed.
  if (!args[0]->IsJSReceiver() || !args[1]->IsObject()) {
    Object* error = isolate->ThrowIllegalOperation();
    return MakePair(error, isolate->heap()->undefined_value());
  }
  Handle<JSReceiver> object = args.at<JSReceiver>(0);
  Handle<Object> cache_type = args.at<Object>(1);
  if (cache_type->IsMap()) {
    // Enum cache case.
    if (Map::EnumLengthBits::decode(Map::cast(*cache_type)->bit_field3()) ==
        0) {
      // 0 length enum.
      // Can't handle this case in the graph builder,
      // so transform it into the empty fixed array case.
      return MakePair(isolate->heap()->empty_fixed_array(), Smi::FromInt(1));
    }
    return MakePair(object->map()->instance_descriptors()->GetEnumCache(),
                    *cache_type);
  } else {
    // FixedArray case.
    Smi* new_cache_type = Smi::FromInt(object->IsJSProxy() ? 0 : 1);
    return MakePair(*Handle<FixedArray>::cast(cache_type), new_cache_type);
  }
}


// TODO(dcarney): remove this function when TurboFan supports it.
RUNTIME_FUNCTION(Runtime_ForInCacheArrayLength) {
  SealHandleScope shs(isolate);
  DCHECK(args.length() == 2);
  CONVERT_ARG_HANDLE_CHECKED(Object, cache_type, 0);
  CONVERT_ARG_HANDLE_CHECKED(FixedArray, array, 1);
  int length = 0;
  if (cache_type->IsMap()) {
    length = Map::cast(*cache_type)->EnumLength();
  } else {
    DCHECK(cache_type->IsSmi());
    length = array->length();
  }
  return Smi::FromInt(length);
}


// TODO(dcarney): remove this function when TurboFan supports it.
// Takes (the object to be iterated over,
//        cache_array from ForInInit,
//        cache_type from ForInInit,
//        the current index)
// Returns pair (array[index], needs_filtering).
RUNTIME_FUNCTION_RETURN_PAIR(Runtime_ForInNext) {
  SealHandleScope scope(isolate);
  DCHECK(args.length() == 4);
  int32_t index;
  // This simulates CONVERT_ARG_HANDLE_CHECKED for calls returning pairs.
  // Not worth creating a macro atm as this function should be removed.
  if (!args[0]->IsJSReceiver() || !args[1]->IsFixedArray() ||
      !args[2]->IsObject() || !args[3]->ToInt32(&index)) {
    Object* error = isolate->ThrowIllegalOperation();
    return MakePair(error, isolate->heap()->undefined_value());
  }
  Handle<JSReceiver> object = args.at<JSReceiver>(0);
  Handle<FixedArray> array = args.at<FixedArray>(1);
  Handle<Object> cache_type = args.at<Object>(2);
  // Figure out first if a slow check is needed for this object.
  bool slow_check_needed = false;
  if (cache_type->IsMap()) {
    if (object->map() != Map::cast(*cache_type)) {
      // Object transitioned.  Need slow check.
      slow_check_needed = true;
    }
  } else {
    // No slow check needed for proxies.
    slow_check_needed = Smi::cast(*cache_type)->value() == 1;
  }
  return MakePair(array->get(index),
                  isolate->heap()->ToBoolean(slow_check_needed));
}


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RUNTIME_FUNCTION(Runtime_IsArray) {
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  SealHandleScope shs(isolate);
  DCHECK(args.length() == 1);
  CONVERT_ARG_CHECKED(Object, obj, 0);
  return isolate->heap()->ToBoolean(obj->IsJSArray());
}


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RUNTIME_FUNCTION(Runtime_HasCachedArrayIndex) {
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  SealHandleScope shs(isolate);
  DCHECK(args.length() == 1);
  return isolate->heap()->false_value();
}


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RUNTIME_FUNCTION(Runtime_GetCachedArrayIndex) {
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  // This can never be reached, because Runtime_HasCachedArrayIndex always
  // returns false.
  UNIMPLEMENTED();
  return nullptr;
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}


1349
RUNTIME_FUNCTION(Runtime_FastOneByteArrayJoin) {
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  SealHandleScope shs(isolate);
  DCHECK(args.length() == 2);
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  // Returning undefined means that this fast path fails and one has to resort
  // to a slow path.
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  return isolate->heap()->undefined_value();
}
}
}  // namespace v8::internal