src/factory.cc

// 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/factory.h"

#include "src/accessors.h"
#include "src/allocation-site-scopes.h"
#include "src/ast/ast-source-ranges.h"
#include "src/ast/ast.h"
#include "src/base/bits.h"
#include "src/bootstrapper.h"
#include "src/compiler.h"
#include "src/conversions.h"
#include "src/isolate-inl.h"
#include "src/macro-assembler.h"
#include "src/objects/bigint-inl.h"
#include "src/objects/debug-objects-inl.h"
#include "src/objects/frame-array-inl.h"
#include "src/objects/module.h"
#include "src/objects/scope-info.h"
#include "src/unicode-cache.h"
#include "src/unicode-decoder.h"

namespace v8 {
namespace internal {


// Calls the FUNCTION_CALL function and retries it up to three times
// to guarantee that any allocations performed during the call will
// succeed if there's enough memory.
//
// Warning: Do not use the identifiers __object__, __maybe_object__,
// __allocation__ or __scope__ in a call to this macro.

#define RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)         \
  if (__allocation__.To(&__object__)) {                   \
    DCHECK(__object__ != (ISOLATE)->heap()->exception()); \
    return Handle<TYPE>(TYPE::cast(__object__), ISOLATE); \
  }

#define CALL_HEAP_FUNCTION(ISOLATE, FUNCTION_CALL, TYPE)                      \
  do {                                                                        \
    AllocationResult __allocation__ = FUNCTION_CALL;                          \
    Object* __object__ = nullptr;                                             \
    RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)                                 \
    /* Two GCs before panicking.  In newspace will almost always succeed. */  \
    for (int __i__ = 0; __i__ < 2; __i__++) {                                 \
      (ISOLATE)->heap()->CollectGarbage(                                      \
          __allocation__.RetrySpace(),                                        \
          GarbageCollectionReason::kAllocationFailure);                       \
      __allocation__ = FUNCTION_CALL;                                         \
      RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)                               \
    }                                                                         \
    (ISOLATE)->counters()->gc_last_resort_from_handles()->Increment();        \
    (ISOLATE)->heap()->CollectAllAvailableGarbage(                            \
        GarbageCollectionReason::kLastResort);                                \
    {                                                                         \
      AlwaysAllocateScope __scope__(ISOLATE);                                 \
      __allocation__ = FUNCTION_CALL;                                         \
    }                                                                         \
    RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)                                 \
    /* TODO(1181417): Fix this. */                                            \
    v8::internal::Heap::FatalProcessOutOfMemory("CALL_AND_RETRY_LAST", true); \
    return Handle<TYPE>();                                                    \
  } while (false)

template<typename T>
Handle<T> Factory::New(Handle<Map> map, AllocationSpace space) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->Allocate(*map, space),
      T);
}


template<typename T>
Handle<T> Factory::New(Handle<Map> map,
                       AllocationSpace space,
                       Handle<AllocationSite> allocation_site) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->Allocate(*map, space, *allocation_site),
      T);
}


Handle<HeapObject> Factory::NewFillerObject(int size,
                                            bool double_align,
                                            AllocationSpace space) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateFillerObject(size, double_align, space),
      HeapObject);
}


Handle<PrototypeInfo> Factory::NewPrototypeInfo() {
  Handle<PrototypeInfo> result =
      Handle<PrototypeInfo>::cast(NewStruct(PROTOTYPE_INFO_TYPE, TENURED));
  result->set_prototype_users(WeakFixedArray::Empty());
  result->set_registry_slot(PrototypeInfo::UNREGISTERED);
  result->set_validity_cell(Smi::kZero);
  result->set_bit_field(0);
  return result;
}

Handle<EnumCache> Factory::NewEnumCache(Handle<FixedArray> keys,
                                        Handle<FixedArray> indices) {
  return Handle<EnumCache>::cast(NewTuple2(keys, indices, TENURED));
}

Handle<Tuple2> Factory::NewTuple2(Handle<Object> value1, Handle<Object> value2,
                                  PretenureFlag pretenure) {
  Handle<Tuple2> result =
      Handle<Tuple2>::cast(NewStruct(TUPLE2_TYPE, pretenure));
  result->set_value1(*value1);
  result->set_value2(*value2);
  return result;
}

Handle<Tuple3> Factory::NewTuple3(Handle<Object> value1, Handle<Object> value2,
                                  Handle<Object> value3,
                                  PretenureFlag pretenure) {
  Handle<Tuple3> result =
      Handle<Tuple3>::cast(NewStruct(TUPLE3_TYPE, pretenure));
  result->set_value1(*value1);
  result->set_value2(*value2);
  result->set_value3(*value3);
  return result;
}

Handle<ContextExtension> Factory::NewContextExtension(
    Handle<ScopeInfo> scope_info, Handle<Object> extension) {
  Handle<ContextExtension> result = Handle<ContextExtension>::cast(
      NewStruct(CONTEXT_EXTENSION_TYPE, TENURED));
  result->set_scope_info(*scope_info);
  result->set_extension(*extension);
  return result;
}

Handle<ConstantElementsPair> Factory::NewConstantElementsPair(
    ElementsKind elements_kind, Handle<FixedArrayBase> constant_values) {
  Handle<ConstantElementsPair> result =
      Handle<ConstantElementsPair>::cast(NewStruct(TUPLE2_TYPE, TENURED));
  result->set_elements_kind(elements_kind);
  result->set_constant_values(*constant_values);
  return result;
}

Handle<TemplateObjectDescription> Factory::NewTemplateObjectDescription(
    int hash, Handle<FixedArray> raw_strings,
    Handle<FixedArray> cooked_strings) {
  DCHECK_EQ(raw_strings->length(), cooked_strings->length());
  DCHECK_LT(0, raw_strings->length());
  Handle<TemplateObjectDescription> result =
      Handle<TemplateObjectDescription>::cast(NewStruct(TUPLE3_TYPE, TENURED));
  result->set_hash(hash);
  result->set_raw_strings(*raw_strings);
  result->set_cooked_strings(*cooked_strings);
  return result;
}

Handle<Oddball> Factory::NewOddball(Handle<Map> map, const char* to_string,
                                    Handle<Object> to_number,
                                    const char* type_of, byte kind) {
  Handle<Oddball> oddball = New<Oddball>(map, OLD_SPACE);
  Oddball::Initialize(isolate(), oddball, to_string, to_number, type_of, kind);
  return oddball;
}


Handle<FixedArray> Factory::NewFixedArray(int size, PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateFixedArray(size, pretenure),
      FixedArray);
}

Handle<PropertyArray> Factory::NewPropertyArray(int size,
                                                PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocatePropertyArray(size, pretenure),
                     PropertyArray);
}

MaybeHandle<FixedArray> Factory::TryNewFixedArray(int size,
                                                  PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  AllocationResult allocation =
      isolate()->heap()->AllocateFixedArray(size, pretenure);
  Object* array = nullptr;
  if (!allocation.To(&array)) return MaybeHandle<FixedArray>();
  return Handle<FixedArray>(FixedArray::cast(array), isolate());
}

Handle<FixedArray> Factory::NewFixedArrayWithHoles(int size,
                                                   PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateFixedArrayWithFiller(size,
                                                      pretenure,
                                                      *the_hole_value()),
      FixedArray);
}

Handle<FixedArray> Factory::NewUninitializedFixedArray(int size) {
  // TODO(ulan): As an experiment this temporarily returns an initialized fixed
  // array. After getting canary/performance coverage, either remove the
  // function or revert to returning uninitilized array.
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateFixedArray(size, NOT_TENURED),
                     FixedArray);
}

Handle<FeedbackVector> Factory::NewFeedbackVector(
    Handle<SharedFunctionInfo> shared, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateFeedbackVector(*shared, pretenure),
      FeedbackVector);
}

Handle<BoilerplateDescription> Factory::NewBoilerplateDescription(
    int boilerplate, int all_properties, int index_keys, bool has_seen_proto) {
  DCHECK_GE(boilerplate, 0);
  DCHECK_GE(all_properties, index_keys);
  DCHECK_GE(index_keys, 0);

  int backing_store_size =
      all_properties - index_keys - (has_seen_proto ? 1 : 0);
  DCHECK_GE(backing_store_size, 0);
  bool has_different_size_backing_store = boilerplate != backing_store_size;

  // Space for name and value for every boilerplate property.
  int size = 2 * boilerplate;

  if (has_different_size_backing_store) {
    // An extra entry for the backing store size.
    size++;
  }

  Handle<BoilerplateDescription> description =
      Handle<BoilerplateDescription>::cast(NewFixedArray(size, TENURED));

  if (has_different_size_backing_store) {
    DCHECK((boilerplate != (all_properties - index_keys)) || has_seen_proto);
    description->set_backing_store_size(isolate(), backing_store_size);
  }
  return description;
}

Handle<FixedArrayBase> Factory::NewFixedDoubleArray(int size,
                                                    PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateUninitializedFixedDoubleArray(size, pretenure),
      FixedArrayBase);
}


Handle<FixedArrayBase> Factory::NewFixedDoubleArrayWithHoles(
    int size,
    PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  Handle<FixedArrayBase> array = NewFixedDoubleArray(size, pretenure);
  if (size > 0) {
    Handle<FixedDoubleArray>::cast(array)->FillWithHoles(0, size);
  }
  return array;
}

Handle<FrameArray> Factory::NewFrameArray(int number_of_frames,
                                          PretenureFlag pretenure) {
  DCHECK_LE(0, number_of_frames);
  Handle<FixedArray> result =
      NewFixedArrayWithHoles(FrameArray::LengthFor(number_of_frames));
  result->set(FrameArray::kFrameCountIndex, Smi::kZero);
  return Handle<FrameArray>::cast(result);
}

Handle<SmallOrderedHashSet> Factory::NewSmallOrderedHashSet(
    int size, PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateSmallOrderedHashSet(size, pretenure),
      SmallOrderedHashSet);
}

Handle<SmallOrderedHashMap> Factory::NewSmallOrderedHashMap(
    int size, PretenureFlag pretenure) {
  DCHECK_LE(0, size);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateSmallOrderedHashMap(size, pretenure),
      SmallOrderedHashMap);
}

Handle<OrderedHashSet> Factory::NewOrderedHashSet() {
  return OrderedHashSet::Allocate(isolate(), OrderedHashSet::kMinCapacity);
}


Handle<OrderedHashMap> Factory::NewOrderedHashMap() {
  return OrderedHashMap::Allocate(isolate(), OrderedHashMap::kMinCapacity);
}


Handle<AccessorPair> Factory::NewAccessorPair() {
  Handle<AccessorPair> accessors =
      Handle<AccessorPair>::cast(NewStruct(ACCESSOR_PAIR_TYPE, TENURED));
  accessors->set_getter(*null_value(), SKIP_WRITE_BARRIER);
  accessors->set_setter(*null_value(), SKIP_WRITE_BARRIER);
  return accessors;
}


Handle<TypeFeedbackInfo> Factory::NewTypeFeedbackInfo() {
  Handle<TypeFeedbackInfo> info =
      Handle<TypeFeedbackInfo>::cast(NewStruct(TUPLE3_TYPE, TENURED));
  info->initialize_storage();
  return info;
}


// Internalized strings are created in the old generation (data space).
Handle<String> Factory::InternalizeUtf8String(Vector<const char> string) {
  Utf8StringKey key(string, isolate()->heap()->HashSeed());
  return InternalizeStringWithKey(&key);
}


Handle<String> Factory::InternalizeOneByteString(Vector<const uint8_t> string) {
  OneByteStringKey key(string, isolate()->heap()->HashSeed());
  return InternalizeStringWithKey(&key);
}


Handle<String> Factory::InternalizeOneByteString(
    Handle<SeqOneByteString> string, int from, int length) {
  SeqOneByteSubStringKey key(string, from, length);
  return InternalizeStringWithKey(&key);
}


Handle<String> Factory::InternalizeTwoByteString(Vector<const uc16> string) {
  TwoByteStringKey key(string, isolate()->heap()->HashSeed());
  return InternalizeStringWithKey(&key);
}


template<class StringTableKey>
Handle<String> Factory::InternalizeStringWithKey(StringTableKey* key) {
  return StringTable::LookupKey(isolate(), key);
}

MaybeHandle<String> Factory::NewStringFromOneByte(Vector<const uint8_t> string,
                                                  PretenureFlag pretenure) {
  int length = string.length();
  if (length == 0) return empty_string();
  if (length == 1) return LookupSingleCharacterStringFromCode(string[0]);
  Handle<SeqOneByteString> result;
  ASSIGN_RETURN_ON_EXCEPTION(
      isolate(),
      result,
      NewRawOneByteString(string.length(), pretenure),
      String);

  DisallowHeapAllocation no_gc;
  // Copy the characters into the new object.
  CopyChars(SeqOneByteString::cast(*result)->GetChars(),
            string.start(),
            length);
  return result;
}

MaybeHandle<String> Factory::NewStringFromUtf8(Vector<const char> string,
                                               PretenureFlag pretenure) {
  // Check for ASCII first since this is the common case.
  const char* start = string.start();
  int length = string.length();
  int non_ascii_start = String::NonAsciiStart(start, length);
  if (non_ascii_start >= length) {
    // If the string is ASCII, we do not need to convert the characters
    // since UTF8 is backwards compatible with ASCII.
    return NewStringFromOneByte(Vector<const uint8_t>::cast(string), pretenure);
  }

  // Non-ASCII and we need to decode.
  Access<UnicodeCache::Utf8Decoder>
      decoder(isolate()->unicode_cache()->utf8_decoder());
  decoder->Reset(string.start() + non_ascii_start,
                 length - non_ascii_start);
  int utf16_length = static_cast<int>(decoder->Utf16Length());
  DCHECK_GT(utf16_length, 0);
  // Allocate string.
  Handle<SeqTwoByteString> result;
  ASSIGN_RETURN_ON_EXCEPTION(
      isolate(), result,
      NewRawTwoByteString(non_ascii_start + utf16_length, pretenure),
      String);
  // Copy ASCII portion.
  uint16_t* data = result->GetChars();
  const char* ascii_data = string.start();
  for (int i = 0; i < non_ascii_start; i++) {
    *data++ = *ascii_data++;
  }
  // Now write the remainder.
  decoder->WriteUtf16(data, utf16_length);
  return result;
}

MaybeHandle<String> Factory::NewStringFromUtf8SubString(
    Handle<SeqOneByteString> str, int begin, int length,
    PretenureFlag pretenure) {
  // Check for ASCII first since this is the common case.
  const char* start = reinterpret_cast<const char*>(str->GetChars() + begin);
  int non_ascii_start = String::NonAsciiStart(start, length);
  if (non_ascii_start >= length) {
    // If the string is ASCII, we can just make a substring.
    // TODO(v8): the pretenure flag is ignored in this case.
    return NewSubString(str, begin, begin + length);
  }

  // Non-ASCII and we need to decode.
  Access<UnicodeCache::Utf8Decoder> decoder(
      isolate()->unicode_cache()->utf8_decoder());
  decoder->Reset(start + non_ascii_start, length - non_ascii_start);
  int utf16_length = static_cast<int>(decoder->Utf16Length());
  DCHECK_GT(utf16_length, 0);
  // Allocate string.
  Handle<SeqTwoByteString> result;
  ASSIGN_RETURN_ON_EXCEPTION(
      isolate(), result,
      NewRawTwoByteString(non_ascii_start + utf16_length, pretenure), String);

  // Reset the decoder, because the original {str} may have moved.
  const char* ascii_data =
      reinterpret_cast<const char*>(str->GetChars() + begin);
  decoder->Reset(ascii_data + non_ascii_start, length - non_ascii_start);
  // Copy ASCII portion.
  uint16_t* data = result->GetChars();
  for (int i = 0; i < non_ascii_start; i++) {
    *data++ = *ascii_data++;
  }
  // Now write the remainder.
  decoder->WriteUtf16(data, utf16_length);
  return result;
}

MaybeHandle<String> Factory::NewStringFromTwoByte(const uc16* string,
                                                  int length,
                                                  PretenureFlag pretenure) {
  if (length == 0) return empty_string();
  if (String::IsOneByte(string, length)) {
    if (length == 1) return LookupSingleCharacterStringFromCode(string[0]);
    Handle<SeqOneByteString> result;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate(),
        result,
        NewRawOneByteString(length, pretenure),
        String);
    CopyChars(result->GetChars(), string, length);
    return result;
  } else {
    Handle<SeqTwoByteString> result;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate(),
        result,
        NewRawTwoByteString(length, pretenure),
        String);
    CopyChars(result->GetChars(), string, length);
    return result;
  }
}

MaybeHandle<String> Factory::NewStringFromTwoByte(Vector<const uc16> string,
                                                  PretenureFlag pretenure) {
  return NewStringFromTwoByte(string.start(), string.length(), pretenure);
}

MaybeHandle<String> Factory::NewStringFromTwoByte(
    const ZoneVector<uc16>* string, PretenureFlag pretenure) {
  return NewStringFromTwoByte(string->data(), static_cast<int>(string->size()),
                              pretenure);
}

Handle<String> Factory::NewInternalizedStringFromUtf8(Vector<const char> str,
                                                      int chars,
                                                      uint32_t hash_field) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateInternalizedStringFromUtf8(
          str, chars, hash_field),
      String);
}


MUST_USE_RESULT Handle<String> Factory::NewOneByteInternalizedString(
      Vector<const uint8_t> str,
      uint32_t hash_field) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateOneByteInternalizedString(str, hash_field),
      String);
}


MUST_USE_RESULT Handle<String> Factory::NewOneByteInternalizedSubString(
    Handle<SeqOneByteString> string, int offset, int length,
    uint32_t hash_field) {
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateOneByteInternalizedString(
                     Vector<const uint8_t>(string->GetChars() + offset, length),
                     hash_field),
      String);
}


MUST_USE_RESULT Handle<String> Factory::NewTwoByteInternalizedString(
      Vector<const uc16> str,
      uint32_t hash_field) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateTwoByteInternalizedString(str, hash_field),
      String);
}


Handle<String> Factory::NewInternalizedStringImpl(
    Handle<String> string, int chars, uint32_t hash_field) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateInternalizedStringImpl(
          *string, chars, hash_field),
      String);
}

namespace {

MaybeHandle<Map> GetInternalizedStringMap(Factory* f, Handle<String> string) {
  switch (string->map()->instance_type()) {
    case STRING_TYPE:
      return f->internalized_string_map();
    case ONE_BYTE_STRING_TYPE:
      return f->one_byte_internalized_string_map();
    case EXTERNAL_STRING_TYPE:
      return f->external_internalized_string_map();
    case EXTERNAL_ONE_BYTE_STRING_TYPE:
      return f->external_one_byte_internalized_string_map();
    case EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE:
      return f->external_internalized_string_with_one_byte_data_map();
    case SHORT_EXTERNAL_STRING_TYPE:
      return f->short_external_internalized_string_map();
    case SHORT_EXTERNAL_ONE_BYTE_STRING_TYPE:
      return f->short_external_one_byte_internalized_string_map();
    case SHORT_EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE:
      return f->short_external_internalized_string_with_one_byte_data_map();
    default: return MaybeHandle<Map>();  // No match found.
  }
}

}  // namespace

MaybeHandle<Map> Factory::InternalizedStringMapForString(
    Handle<String> string) {
  // If the string is in new space it cannot be used as internalized.
  if (isolate()->heap()->InNewSpace(*string)) return MaybeHandle<Map>();

  return GetInternalizedStringMap(this, string);
}

template <class StringClass>
Handle<StringClass> Factory::InternalizeExternalString(Handle<String> string) {
  Handle<StringClass> cast_string = Handle<StringClass>::cast(string);
  Handle<Map> map = GetInternalizedStringMap(this, string).ToHandleChecked();
  Handle<StringClass> external_string = New<StringClass>(map, OLD_SPACE);
  external_string->set_length(cast_string->length());
  external_string->set_hash_field(cast_string->hash_field());
  external_string->set_resource(nullptr);
  isolate()->heap()->RegisterExternalString(*external_string);
  return external_string;
}

template Handle<ExternalOneByteString>
    Factory::InternalizeExternalString<ExternalOneByteString>(Handle<String>);
template Handle<ExternalTwoByteString>
    Factory::InternalizeExternalString<ExternalTwoByteString>(Handle<String>);

MaybeHandle<SeqOneByteString> Factory::NewRawOneByteString(
    int length, PretenureFlag pretenure) {
  if (length > String::kMaxLength || length < 0) {
    THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), SeqOneByteString);
  }
  DCHECK_GT(length, 0);  // Use Factory::empty_string() instead.
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateRawOneByteString(length, pretenure),
      SeqOneByteString);
}


MaybeHandle<SeqTwoByteString> Factory::NewRawTwoByteString(
    int length, PretenureFlag pretenure) {
  if (length > String::kMaxLength || length < 0) {
    THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), SeqTwoByteString);
  }
  DCHECK_GT(length, 0);  // Use Factory::empty_string() instead.
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateRawTwoByteString(length, pretenure),
      SeqTwoByteString);
}


Handle<String> Factory::LookupSingleCharacterStringFromCode(uint32_t code) {
  if (code <= String::kMaxOneByteCharCodeU) {
    {
      DisallowHeapAllocation no_allocation;
      Object* value = single_character_string_cache()->get(code);
      if (value != *undefined_value()) {
        return handle(String::cast(value), isolate());
      }
    }
    uint8_t buffer[1];
    buffer[0] = static_cast<uint8_t>(code);
    Handle<String> result =
        InternalizeOneByteString(Vector<const uint8_t>(buffer, 1));
    single_character_string_cache()->set(code, *result);
    return result;
  }
  DCHECK_LE(code, String::kMaxUtf16CodeUnitU);

  Handle<SeqTwoByteString> result = NewRawTwoByteString(1).ToHandleChecked();
  result->SeqTwoByteStringSet(0, static_cast<uint16_t>(code));
  return result;
}


// Returns true for a character in a range.  Both limits are inclusive.
static inline bool Between(uint32_t character, uint32_t from, uint32_t to) {
  // This makes uses of the the unsigned wraparound.
  return character - from <= to - from;
}


static inline Handle<String> MakeOrFindTwoCharacterString(Isolate* isolate,
                                                          uint16_t c1,
                                                          uint16_t c2) {
  // Numeric strings have a different hash algorithm not known by
  // LookupTwoCharsStringIfExists, so we skip this step for such strings.
  if (!Between(c1, '0', '9') || !Between(c2, '0', '9')) {
    Handle<String> result;
    if (StringTable::LookupTwoCharsStringIfExists(isolate, c1, c2).
        ToHandle(&result)) {
      return result;
    }
  }

  // Now we know the length is 2, we might as well make use of that fact
  // when building the new string.
  if (static_cast<unsigned>(c1 | c2) <= String::kMaxOneByteCharCodeU) {
    // We can do this.
    DCHECK(base::bits::IsPowerOfTwo(String::kMaxOneByteCharCodeU +
                                    1));  // because of this.
    Handle<SeqOneByteString> str =
        isolate->factory()->NewRawOneByteString(2).ToHandleChecked();
    uint8_t* dest = str->GetChars();
    dest[0] = static_cast<uint8_t>(c1);
    dest[1] = static_cast<uint8_t>(c2);
    return str;
  } else {
    Handle<SeqTwoByteString> str =
        isolate->factory()->NewRawTwoByteString(2).ToHandleChecked();
    uc16* dest = str->GetChars();
    dest[0] = c1;
    dest[1] = c2;
    return str;
  }
}


template<typename SinkChar, typename StringType>
Handle<String> ConcatStringContent(Handle<StringType> result,
                                   Handle<String> first,
                                   Handle<String> second) {
  DisallowHeapAllocation pointer_stays_valid;
  SinkChar* sink = result->GetChars();
  String::WriteToFlat(*first, sink, 0, first->length());
  String::WriteToFlat(*second, sink + first->length(), 0, second->length());
  return result;
}


MaybeHandle<String> Factory::NewConsString(Handle<String> left,
                                           Handle<String> right) {
  if (left->IsThinString()) {
    left = handle(Handle<ThinString>::cast(left)->actual(), isolate());
  }
  if (right->IsThinString()) {
    right = handle(Handle<ThinString>::cast(right)->actual(), isolate());
  }
  int left_length = left->length();
  if (left_length == 0) return right;
  int right_length = right->length();
  if (right_length == 0) return left;

  int length = left_length + right_length;

  if (length == 2) {
    uint16_t c1 = left->Get(0);
    uint16_t c2 = right->Get(0);
    return MakeOrFindTwoCharacterString(isolate(), c1, c2);
  }

  // Make sure that an out of memory exception is thrown if the length
  // of the new cons string is too large.
  if (length > String::kMaxLength || length < 0) {
    THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
  }

  bool left_is_one_byte = left->IsOneByteRepresentation();
  bool right_is_one_byte = right->IsOneByteRepresentation();
  bool is_one_byte = left_is_one_byte && right_is_one_byte;
  bool is_one_byte_data_in_two_byte_string = false;
  if (!is_one_byte) {
    // At least one of the strings uses two-byte representation so we
    // can't use the fast case code for short one-byte strings below, but
    // we can try to save memory if all chars actually fit in one-byte.
    is_one_byte_data_in_two_byte_string =
        left->HasOnlyOneByteChars() && right->HasOnlyOneByteChars();
    if (is_one_byte_data_in_two_byte_string) {
      isolate()->counters()->string_add_runtime_ext_to_one_byte()->Increment();
    }
  }

  // If the resulting string is small make a flat string.
  if (length < ConsString::kMinLength) {
    // Note that neither of the two inputs can be a slice because:
    STATIC_ASSERT(ConsString::kMinLength <= SlicedString::kMinLength);
    DCHECK(left->IsFlat());
    DCHECK(right->IsFlat());

    STATIC_ASSERT(ConsString::kMinLength <= String::kMaxLength);
    if (is_one_byte) {
      Handle<SeqOneByteString> result =
          NewRawOneByteString(length).ToHandleChecked();
      DisallowHeapAllocation no_gc;
      uint8_t* dest = result->GetChars();
      // Copy left part.
      const uint8_t* src =
          left->IsExternalString()
              ? Handle<ExternalOneByteString>::cast(left)->GetChars()
              : Handle<SeqOneByteString>::cast(left)->GetChars();
      for (int i = 0; i < left_length; i++) *dest++ = src[i];
      // Copy right part.
      src = right->IsExternalString()
                ? Handle<ExternalOneByteString>::cast(right)->GetChars()
                : Handle<SeqOneByteString>::cast(right)->GetChars();
      for (int i = 0; i < right_length; i++) *dest++ = src[i];
      return result;
    }

    return (is_one_byte_data_in_two_byte_string)
        ? ConcatStringContent<uint8_t>(
            NewRawOneByteString(length).ToHandleChecked(), left, right)
        : ConcatStringContent<uc16>(
            NewRawTwoByteString(length).ToHandleChecked(), left, right);
  }

  bool one_byte = (is_one_byte || is_one_byte_data_in_two_byte_string);
  return NewConsString(left, right, length, one_byte);
}

Handle<String> Factory::NewConsString(Handle<String> left, Handle<String> right,
                                      int length, bool one_byte) {
  DCHECK(!left->IsThinString());
  DCHECK(!right->IsThinString());
  DCHECK_GE(length, ConsString::kMinLength);
  DCHECK_LE(length, String::kMaxLength);

  Handle<ConsString> result =
      one_byte ? New<ConsString>(cons_one_byte_string_map(), NEW_SPACE)
               : New<ConsString>(cons_string_map(), NEW_SPACE);

  DisallowHeapAllocation no_gc;
  WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);

  result->set_hash_field(String::kEmptyHashField);
  result->set_length(length);
  result->set_first(*left, mode);
  result->set_second(*right, mode);
  return result;
}

Handle<String> Factory::NewSurrogatePairString(uint16_t lead, uint16_t trail) {
  DCHECK_GE(lead, 0xD800);
  DCHECK_LE(lead, 0xDBFF);
  DCHECK_GE(trail, 0xDC00);
  DCHECK_LE(trail, 0xDFFF);

  Handle<SeqTwoByteString> str =
      isolate()->factory()->NewRawTwoByteString(2).ToHandleChecked();
  uc16* dest = str->GetChars();
  dest[0] = lead;
  dest[1] = trail;
  return str;
}

Handle<String> Factory::NewProperSubString(Handle<String> str,
                                           int begin,
                                           int end) {
#if VERIFY_HEAP
  if (FLAG_verify_heap) str->StringVerify();
#endif
  DCHECK(begin > 0 || end < str->length());

  str = String::Flatten(str);

  int length = end - begin;
  if (length <= 0) return empty_string();
  if (length == 1) {
    return LookupSingleCharacterStringFromCode(str->Get(begin));
  }
  if (length == 2) {
    // Optimization for 2-byte strings often used as keys in a decompression
    // dictionary.  Check whether we already have the string in the string
    // table to prevent creation of many unnecessary strings.
    uint16_t c1 = str->Get(begin);
    uint16_t c2 = str->Get(begin + 1);
    return MakeOrFindTwoCharacterString(isolate(), c1, c2);
  }

  if (!FLAG_string_slices || length < SlicedString::kMinLength) {
    if (str->IsOneByteRepresentation()) {
      Handle<SeqOneByteString> result =
          NewRawOneByteString(length).ToHandleChecked();
      uint8_t* dest = result->GetChars();
      DisallowHeapAllocation no_gc;
      String::WriteToFlat(*str, dest, begin, end);
      return result;
    } else {
      Handle<SeqTwoByteString> result =
          NewRawTwoByteString(length).ToHandleChecked();
      uc16* dest = result->GetChars();
      DisallowHeapAllocation no_gc;
      String::WriteToFlat(*str, dest, begin, end);
      return result;
    }
  }

  int offset = begin;

  if (str->IsSlicedString()) {
    Handle<SlicedString> slice = Handle<SlicedString>::cast(str);
    str = Handle<String>(slice->parent(), isolate());
    offset += slice->offset();
  }
  if (str->IsThinString()) {
    Handle<ThinString> thin = Handle<ThinString>::cast(str);
    str = handle(thin->actual(), isolate());
  }

  DCHECK(str->IsSeqString() || str->IsExternalString());
  Handle<Map> map = str->IsOneByteRepresentation()
                        ? sliced_one_byte_string_map()
                        : sliced_string_map();
  Handle<SlicedString> slice = New<SlicedString>(map, NEW_SPACE);

  slice->set_hash_field(String::kEmptyHashField);
  slice->set_length(length);
  slice->set_parent(*str);
  slice->set_offset(offset);
  return slice;
}

MaybeHandle<String> Factory::NewExternalStringFromOneByte(
    const ExternalOneByteString::Resource* resource) {
  size_t length = resource->length();
  if (length > static_cast<size_t>(String::kMaxLength)) {
    THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
  }
  if (length == 0) return empty_string();

  Handle<Map> map;
  if (resource->IsCompressible()) {
    // TODO(hajimehoshi): Rename this to 'uncached_external_one_byte_string_map'
    map = short_external_one_byte_string_map();
  } else {
    map = external_one_byte_string_map();
  }
  Handle<ExternalOneByteString> external_string =
      New<ExternalOneByteString>(map, NEW_SPACE);
  external_string->set_length(static_cast<int>(length));
  external_string->set_hash_field(String::kEmptyHashField);
  external_string->set_resource(resource);

  return external_string;
}


MaybeHandle<String> Factory::NewExternalStringFromTwoByte(
    const ExternalTwoByteString::Resource* resource) {
  size_t length = resource->length();
  if (length > static_cast<size_t>(String::kMaxLength)) {
    THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
  }
  if (length == 0) return empty_string();

  // For small strings we check whether the resource contains only
  // one byte characters.  If yes, we use a different string map.
  static const size_t kOneByteCheckLengthLimit = 32;
  bool is_one_byte = length <= kOneByteCheckLengthLimit &&
      String::IsOneByte(resource->data(), static_cast<int>(length));
  Handle<Map> map;
  if (resource->IsCompressible()) {
    // TODO(hajimehoshi): Rename these to 'uncached_external_string_...'.
    map = is_one_byte ? short_external_string_with_one_byte_data_map()
                      : short_external_string_map();
  } else {
    map = is_one_byte ? external_string_with_one_byte_data_map()
                      : external_string_map();
  }
  Handle<ExternalTwoByteString> external_string =
      New<ExternalTwoByteString>(map, NEW_SPACE);
  external_string->set_length(static_cast<int>(length));
  external_string->set_hash_field(String::kEmptyHashField);
  external_string->set_resource(resource);

  return external_string;
}

Handle<ExternalOneByteString> Factory::NewNativeSourceString(
    const ExternalOneByteString::Resource* resource) {
  size_t length = resource->length();
  DCHECK_LE(length, static_cast<size_t>(String::kMaxLength));

  Handle<Map> map = native_source_string_map();
  Handle<ExternalOneByteString> external_string =
      New<ExternalOneByteString>(map, OLD_SPACE);
  external_string->set_length(static_cast<int>(length));
  external_string->set_hash_field(String::kEmptyHashField);
  external_string->set_resource(resource);

  return external_string;
}

Handle<JSStringIterator> Factory::NewJSStringIterator(Handle<String> string) {
  Handle<Map> map(isolate()->native_context()->string_iterator_map(),
                  isolate());
  Handle<String> flat_string = String::Flatten(string);
  Handle<JSStringIterator> iterator =
      Handle<JSStringIterator>::cast(NewJSObjectFromMap(map));
  iterator->set_string(*flat_string);
  iterator->set_index(0);

  return iterator;
}

Handle<Symbol> Factory::NewSymbol() {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateSymbol(),
      Symbol);
}


Handle<Symbol> Factory::NewPrivateSymbol() {
  Handle<Symbol> symbol = NewSymbol();
  symbol->set_is_private(true);
  return symbol;
}

Handle<Context> Factory::NewNativeContext() {
  Handle<FixedArray> array =
      NewFixedArray(Context::NATIVE_CONTEXT_SLOTS, TENURED);
  array->set_map_no_write_barrier(*native_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_native_context(*context);
  context->set_errors_thrown(Smi::kZero);
  context->set_math_random_index(Smi::kZero);
  Handle<WeakCell> weak_cell = NewWeakCell(context);
  context->set_self_weak_cell(*weak_cell);
  DCHECK(context->IsNativeContext());
  return context;
}


Handle<Context> Factory::NewScriptContext(Handle<JSFunction> function,
                                          Handle<ScopeInfo> scope_info) {
  DCHECK_EQ(scope_info->scope_type(), SCRIPT_SCOPE);
  Handle<FixedArray> array =
      NewFixedArray(scope_info->ContextLength(), TENURED);
  array->set_map_no_write_barrier(*script_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(function->context());
  context->set_extension(*scope_info);
  context->set_native_context(function->native_context());
  DCHECK(context->IsScriptContext());
  return context;
}


Handle<ScriptContextTable> Factory::NewScriptContextTable() {
  Handle<FixedArray> array = NewFixedArray(1);
  array->set_map_no_write_barrier(*script_context_table_map());
  Handle<ScriptContextTable> context_table =
      Handle<ScriptContextTable>::cast(array);
  context_table->set_used(0);
  return context_table;
}

Handle<Context> Factory::NewModuleContext(Handle<Module> module,
                                          Handle<JSFunction> function,
                                          Handle<ScopeInfo> scope_info) {
  DCHECK_EQ(scope_info->scope_type(), MODULE_SCOPE);
  Handle<FixedArray> array =
      NewFixedArray(scope_info->ContextLength(), TENURED);
  array->set_map_no_write_barrier(*module_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(function->context());
  context->set_extension(*module);
  context->set_native_context(function->native_context());
  DCHECK(context->IsModuleContext());
  return context;
}

Handle<Context> Factory::NewFunctionContext(int length,
                                            Handle<JSFunction> function,
                                            ScopeType scope_type) {
  DCHECK(function->shared()->scope_info()->scope_type() == scope_type);
  DCHECK(length >= Context::MIN_CONTEXT_SLOTS);
  Handle<FixedArray> array = NewFixedArray(length);
  Handle<Map> map;
  switch (scope_type) {
    case EVAL_SCOPE:
      map = eval_context_map();
      break;
    case FUNCTION_SCOPE:
      map = function_context_map();
      break;
    default:
      UNREACHABLE();
  }
  array->set_map_no_write_barrier(*map);
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(function->context());
  context->set_extension(*the_hole_value());
  context->set_native_context(function->native_context());
  return context;
}

Handle<Context> Factory::NewCatchContext(Handle<JSFunction> function,
                                         Handle<Context> previous,
                                         Handle<ScopeInfo> scope_info,
                                         Handle<String> name,
                                         Handle<Object> thrown_object) {
  STATIC_ASSERT(Context::MIN_CONTEXT_SLOTS == Context::THROWN_OBJECT_INDEX);
  Handle<ContextExtension> extension = NewContextExtension(scope_info, name);
  Handle<FixedArray> array = NewFixedArray(Context::MIN_CONTEXT_SLOTS + 1);
  array->set_map_no_write_barrier(*catch_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(*previous);
  context->set_extension(*extension);
  context->set_native_context(previous->native_context());
  context->set(Context::THROWN_OBJECT_INDEX, *thrown_object);
  return context;
}

Handle<Context> Factory::NewDebugEvaluateContext(Handle<Context> previous,
                                                 Handle<ScopeInfo> scope_info,
                                                 Handle<JSReceiver> extension,
                                                 Handle<Context> wrapped,
                                                 Handle<StringSet> whitelist) {
  STATIC_ASSERT(Context::WHITE_LIST_INDEX == Context::MIN_CONTEXT_SLOTS + 1);
  DCHECK(scope_info->IsDebugEvaluateScope());
  Handle<ContextExtension> context_extension = NewContextExtension(
      scope_info, extension.is_null() ? Handle<Object>::cast(undefined_value())
                                      : Handle<Object>::cast(extension));
  Handle<FixedArray> array = NewFixedArray(Context::MIN_CONTEXT_SLOTS + 2);
  array->set_map_no_write_barrier(*debug_evaluate_context_map());
  Handle<Context> c = Handle<Context>::cast(array);
  c->set_closure(wrapped.is_null() ? previous->closure() : wrapped->closure());
  c->set_previous(*previous);
  c->set_native_context(previous->native_context());
  c->set_extension(*context_extension);
  if (!wrapped.is_null()) c->set(Context::WRAPPED_CONTEXT_INDEX, *wrapped);
  if (!whitelist.is_null()) c->set(Context::WHITE_LIST_INDEX, *whitelist);
  return c;
}

Handle<Context> Factory::NewWithContext(Handle<JSFunction> function,
                                        Handle<Context> previous,
                                        Handle<ScopeInfo> scope_info,
                                        Handle<JSReceiver> extension) {
  Handle<ContextExtension> context_extension =
      NewContextExtension(scope_info, extension);
  Handle<FixedArray> array = NewFixedArray(Context::MIN_CONTEXT_SLOTS);
  array->set_map_no_write_barrier(*with_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(*previous);
  context->set_extension(*context_extension);
  context->set_native_context(previous->native_context());
  return context;
}


Handle<Context> Factory::NewBlockContext(Handle<JSFunction> function,
                                         Handle<Context> previous,
                                         Handle<ScopeInfo> scope_info) {
  DCHECK_EQ(scope_info->scope_type(), BLOCK_SCOPE);
  Handle<FixedArray> array = NewFixedArray(scope_info->ContextLength());
  array->set_map_no_write_barrier(*block_context_map());
  Handle<Context> context = Handle<Context>::cast(array);
  context->set_closure(*function);
  context->set_previous(*previous);
  context->set_extension(*scope_info);
  context->set_native_context(previous->native_context());
  return context;
}

Handle<Struct> Factory::NewStruct(InstanceType type, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateStruct(type, pretenure), Struct);
}

Handle<AliasedArgumentsEntry> Factory::NewAliasedArgumentsEntry(
    int aliased_context_slot) {
  Handle<AliasedArgumentsEntry> entry = Handle<AliasedArgumentsEntry>::cast(
      NewStruct(ALIASED_ARGUMENTS_ENTRY_TYPE, NOT_TENURED));
  entry->set_aliased_context_slot(aliased_context_slot);
  return entry;
}


Handle<AccessorInfo> Factory::NewAccessorInfo() {
  Handle<AccessorInfo> info =
      Handle<AccessorInfo>::cast(NewStruct(ACCESSOR_INFO_TYPE, TENURED));
  info->set_name(*empty_string());
  info->set_flags(0);  // Must clear the flags, it was initialized as undefined.
  info->set_is_sloppy(true);
  info->set_initial_property_attributes(NONE);
  return info;
}


Handle<Script> Factory::NewScript(Handle<String> source) {
  // Create and initialize script object.
  Heap* heap = isolate()->heap();
  Handle<Script> script = Handle<Script>::cast(NewStruct(SCRIPT_TYPE, TENURED));
  script->set_source(*source);
  script->set_name(heap->undefined_value());
  script->set_id(isolate()->heap()->NextScriptId());
  script->set_line_offset(0);
  script->set_column_offset(0);
  script->set_context_data(heap->undefined_value());
  script->set_type(Script::TYPE_NORMAL);
  script->set_wrapper(heap->undefined_value());
  script->set_line_ends(heap->undefined_value());
  script->set_eval_from_shared(heap->undefined_value());
  script->set_eval_from_position(0);
  script->set_shared_function_infos(*empty_fixed_array(), SKIP_WRITE_BARRIER);
  script->set_flags(0);
  script->set_host_defined_options(*empty_fixed_array());
  heap->set_script_list(*WeakFixedArray::Add(script_list(), script));
  return script;
}


Handle<Foreign> Factory::NewForeign(Address addr, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateForeign(addr, pretenure),
                     Foreign);
}


Handle<Foreign> Factory::NewForeign(const AccessorDescriptor* desc) {
  return NewForeign((Address) desc, TENURED);
}


Handle<ByteArray> Factory::NewByteArray(int length, PretenureFlag pretenure) {
  DCHECK_LE(0, length);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateByteArray(length, pretenure),
      ByteArray);
}


Handle<BytecodeArray> Factory::NewBytecodeArray(
    int length, const byte* raw_bytecodes, int frame_size, int parameter_count,
    Handle<FixedArray> constant_pool) {
  DCHECK_LE(0, length);
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateBytecodeArray(
                                    length, raw_bytecodes, frame_size,
                                    parameter_count, *constant_pool),
                     BytecodeArray);
}


Handle<FixedTypedArrayBase> Factory::NewFixedTypedArrayWithExternalPointer(
    int length, ExternalArrayType array_type, void* external_pointer,
    PretenureFlag pretenure) {
  DCHECK(0 <= length && length <= Smi::kMaxValue);
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateFixedTypedArrayWithExternalPointer(
                     length, array_type, external_pointer, pretenure),
      FixedTypedArrayBase);
}


Handle<FixedTypedArrayBase> Factory::NewFixedTypedArray(
    int length, ExternalArrayType array_type, bool initialize,
    PretenureFlag pretenure) {
  DCHECK(0 <= length && length <= Smi::kMaxValue);
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateFixedTypedArray(
                                    length, array_type, initialize, pretenure),
                     FixedTypedArrayBase);
}

Handle<Cell> Factory::NewCell(Handle<Object> value) {
  AllowDeferredHandleDereference convert_to_cell;
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateCell(*value),
      Cell);
}

Handle<Cell> Factory::NewNoClosuresCell(Handle<Object> value) {
  Handle<Cell> cell = NewCell(value);
  cell->set_map_no_write_barrier(*no_closures_cell_map());
  return cell;
}

Handle<Cell> Factory::NewOneClosureCell(Handle<Object> value) {
  Handle<Cell> cell = NewCell(value);
  cell->set_map_no_write_barrier(*one_closure_cell_map());
  return cell;
}

Handle<Cell> Factory::NewManyClosuresCell(Handle<Object> value) {
  Handle<Cell> cell = NewCell(value);
  cell->set_map_no_write_barrier(*many_closures_cell_map());
  return cell;
}

Handle<PropertyCell> Factory::NewPropertyCell(Handle<Name> name) {
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocatePropertyCell(*name),
                     PropertyCell);
}


Handle<WeakCell> Factory::NewWeakCell(Handle<HeapObject> value) {
  // It is safe to dereference the value because we are embedding it
  // in cell and not inspecting its fields.
  AllowDeferredHandleDereference convert_to_cell;
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateWeakCell(*value),
                     WeakCell);
}


Handle<TransitionArray> Factory::NewTransitionArray(int capacity) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateTransitionArray(capacity),
                     TransitionArray);
}


Handle<AllocationSite> Factory::NewAllocationSite() {
  Handle<Map> map = allocation_site_map();
  Handle<AllocationSite> site = New<AllocationSite>(map, OLD_SPACE);
  site->Initialize();

  // Link the site
  site->set_weak_next(isolate()->heap()->allocation_sites_list());
  isolate()->heap()->set_allocation_sites_list(*site);
  return site;
}

Handle<Map> Factory::NewMap(InstanceType type, int instance_size,
                            ElementsKind elements_kind,
                            int inobject_properties) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateMap(type, instance_size, elements_kind,
                                     inobject_properties),
      Map);
}


Handle<JSObject> Factory::CopyJSObject(Handle<JSObject> object) {
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->CopyJSObject(*object, nullptr), JSObject);
}


Handle<JSObject> Factory::CopyJSObjectWithAllocationSite(
    Handle<JSObject> object,
    Handle<AllocationSite> site) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyJSObject(
                         *object, site.is_null() ? nullptr : *site),
                     JSObject);
}

Handle<FixedArray> Factory::CopyFixedArrayWithMap(Handle<FixedArray> array,
                                                  Handle<Map> map) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyFixedArrayWithMap(*array, *map),
                     FixedArray);
}

Handle<FixedArray> Factory::CopyFixedArrayAndGrow(Handle<FixedArray> array,
                                                  int grow_by,
                                                  PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->CopyArrayAndGrow(*array, grow_by, pretenure),
      FixedArray);
}

Handle<PropertyArray> Factory::CopyPropertyArrayAndGrow(
    Handle<PropertyArray> array, int grow_by, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->CopyArrayAndGrow(*array, grow_by, pretenure),
      PropertyArray);
}

Handle<FixedArray> Factory::CopyFixedArrayUpTo(Handle<FixedArray> array,
                                               int new_len,
                                               PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->CopyFixedArrayUpTo(
                                    *array, new_len, pretenure),
                     FixedArray);
}

Handle<FixedArray> Factory::CopyFixedArray(Handle<FixedArray> array) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyFixedArray(*array),
                     FixedArray);
}


Handle<FixedArray> Factory::CopyAndTenureFixedCOWArray(
    Handle<FixedArray> array) {
  DCHECK(isolate()->heap()->InNewSpace(*array));
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyAndTenureFixedCOWArray(*array),
                     FixedArray);
}


Handle<FixedDoubleArray> Factory::CopyFixedDoubleArray(
    Handle<FixedDoubleArray> array) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyFixedDoubleArray(*array),
                     FixedDoubleArray);
}

Handle<FeedbackVector> Factory::CopyFeedbackVector(
    Handle<FeedbackVector> array) {
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->CopyFeedbackVector(*array),
                     FeedbackVector);
}

Handle<Object> Factory::NewNumber(double value,
                                  PretenureFlag pretenure) {
  // Materialize as a SMI if possible
  int32_t int_value;
  if (DoubleToSmiInteger(value, &int_value)) {
    return handle(Smi::FromInt(int_value), isolate());
  }

  // Materialize the value in the heap.
  return NewHeapNumber(value, IMMUTABLE, pretenure);
}


Handle<Object> Factory::NewNumberFromInt(int32_t value,
                                         PretenureFlag pretenure) {
  if (Smi::IsValid(value)) return handle(Smi::FromInt(value), isolate());
  // Bypass NewNumber to avoid various redundant checks.
  return NewHeapNumber(FastI2D(value), IMMUTABLE, pretenure);
}


Handle<Object> Factory::NewNumberFromUint(uint32_t value,
                                          PretenureFlag pretenure) {
  int32_t int32v = static_cast<int32_t>(value);
  if (int32v >= 0 && Smi::IsValid(int32v)) {
    return handle(Smi::FromInt(int32v), isolate());
  }
  return NewHeapNumber(FastUI2D(value), IMMUTABLE, pretenure);
}

Handle<HeapNumber> Factory::NewHeapNumber(MutableMode mode,
                                          PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateHeapNumber(mode, pretenure),
                     HeapNumber);
}

Handle<BigInt> Factory::NewBigInt(int length, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateBigInt(length, true, pretenure),
                     BigInt);
}

Handle<BigInt> Factory::NewBigIntRaw(int length, PretenureFlag pretenure) {
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateBigInt(length, false, pretenure),
      BigInt);
}

Handle<BigInt> Factory::NewBigIntFromSafeInteger(double value,
                                                 PretenureFlag pretenure) {
  if (value == 0) return NewBigInt(0);

  uint64_t absolute = std::abs(value);

#if V8_TARGET_ARCH_64_BIT
  static_assert(sizeof(BigInt::digit_t) == sizeof(uint64_t),
                "unexpected BigInt digit size");
  Handle<BigInt> result = NewBigIntRaw(1);
  result->set_digit(0, absolute);
#else
  static_assert(sizeof(BigInt::digit_t) == sizeof(uint32_t),
                "unexpected BigInt digit size");
  Handle<BigInt> result = NewBigIntRaw(2);
  result->set_digit(0, absolute);
  result->set_digit(1, absolute >> 32);
#endif

  result->set_sign(value < 0);  // Treats -0 like 0.
  return result;
}

Handle<BigInt> Factory::NewBigIntFromInt(int value, PretenureFlag pretenure) {
  if (value == 0) return NewBigInt(0);
  Handle<BigInt> result = NewBigIntRaw(1);
  if (value > 0) {
    result->set_digit(0, value);
  } else if (value == kMinInt) {
    STATIC_ASSERT(kMinInt == -kMaxInt - 1);
    result->set_digit(0, static_cast<BigInt::digit_t>(kMaxInt) + 1);
    result->set_sign(true);
  } else {
    result->set_digit(0, -value);
    result->set_sign(true);
  }
  return result;
}

Handle<Object> Factory::NewError(Handle<JSFunction> constructor,
                                 MessageTemplate::Template template_index,
                                 Handle<Object> arg0, Handle<Object> arg1,
                                 Handle<Object> arg2) {
  HandleScope scope(isolate());
  if (isolate()->bootstrapper()->IsActive()) {
    // During bootstrapping we cannot construct error objects.
    return scope.CloseAndEscape(NewStringFromAsciiChecked(
        MessageTemplate::TemplateString(template_index)));
  }

  if (arg0.is_null()) arg0 = undefined_value();
  if (arg1.is_null()) arg1 = undefined_value();
  if (arg2.is_null()) arg2 = undefined_value();

  Handle<Object> result;
  if (!ErrorUtils::MakeGenericError(isolate(), constructor, template_index,
                                    arg0, arg1, arg2, SKIP_NONE)
           .ToHandle(&result)) {
    // If an exception is thrown while
    // running the factory method, use the exception as the result.
    DCHECK(isolate()->has_pending_exception());
    result = handle(isolate()->pending_exception(), isolate());
    isolate()->clear_pending_exception();
  }

  return scope.CloseAndEscape(result);
}


Handle<Object> Factory::NewError(Handle<JSFunction> constructor,
                                 Handle<String> message) {
  // Construct a new error object. If an exception is thrown, use the exception
  // as the result.

  Handle<Object> no_caller;
  MaybeHandle<Object> maybe_error =
      ErrorUtils::Construct(isolate(), constructor, constructor, message,
                            SKIP_NONE, no_caller, false);
  if (maybe_error.is_null()) {
    DCHECK(isolate()->has_pending_exception());
    maybe_error = handle(isolate()->pending_exception(), isolate());
    isolate()->clear_pending_exception();
  }

  return maybe_error.ToHandleChecked();
}

Handle<Object> Factory::NewInvalidStringLengthError() {
  if (FLAG_abort_on_stack_or_string_length_overflow) {
    FATAL("Aborting on invalid string length");
  }
  // Invalidate the "string length" protector.
  if (isolate()->IsStringLengthOverflowIntact()) {
    isolate()->InvalidateStringLengthOverflowProtector();
  }
  return NewRangeError(MessageTemplate::kInvalidStringLength);
}

#define DEFINE_ERROR(NAME, name)                                              \
  Handle<Object> Factory::New##NAME(MessageTemplate::Template template_index, \
                                    Handle<Object> arg0, Handle<Object> arg1, \
                                    Handle<Object> arg2) {                    \
    return NewError(isolate()->name##_function(), template_index, arg0, arg1, \
                    arg2);                                                    \
  }
DEFINE_ERROR(Error, error)
DEFINE_ERROR(EvalError, eval_error)
DEFINE_ERROR(RangeError, range_error)
DEFINE_ERROR(ReferenceError, reference_error)
DEFINE_ERROR(SyntaxError, syntax_error)
DEFINE_ERROR(TypeError, type_error)
DEFINE_ERROR(WasmCompileError, wasm_compile_error)
DEFINE_ERROR(WasmLinkError, wasm_link_error)
DEFINE_ERROR(WasmRuntimeError, wasm_runtime_error)
#undef DEFINE_ERROR

Handle<JSFunction> Factory::NewFunction(Handle<Map> map,
                                        Handle<SharedFunctionInfo> info,
                                        Handle<Object> context_or_undefined,
                                        PretenureFlag pretenure) {
  AllocationSpace space = pretenure == TENURED ? OLD_SPACE : NEW_SPACE;
  Handle<JSFunction> function = New<JSFunction>(map, space);
  DCHECK(context_or_undefined->IsContext() ||
         context_or_undefined->IsUndefined(isolate()));

  function->initialize_properties();
  function->initialize_elements();
  function->set_shared(*info);
  function->set_code(info->code());
  function->set_context(*context_or_undefined);
  function->set_feedback_vector_cell(*undefined_cell());
  int header_size;
  if (map->has_prototype_slot()) {
    header_size = JSFunction::kSizeWithPrototype;
    function->set_prototype_or_initial_map(*the_hole_value());
  } else {
    header_size = JSFunction::kSizeWithoutPrototype;
  }
  isolate()->heap()->InitializeJSObjectBody(*function, *map, header_size);
  return function;
}

Handle<JSFunction> Factory::NewFunction(Handle<Map> map, Handle<String> name,
                                        MaybeHandle<Code> maybe_code) {
  DCHECK(!name.is_null());
  Handle<Context> context(isolate()->native_context());
  Handle<SharedFunctionInfo> info =
      NewSharedFunctionInfo(name, maybe_code, map->is_constructor());
  // Proper language mode in shared function info will be set outside.
  DCHECK(is_sloppy(info->language_mode()));
  DCHECK(!map->IsUndefined(isolate()));
#ifdef DEBUG
  if (isolate()->bootstrapper()->IsActive()) {
    Handle<Code> code;
    bool has_code = maybe_code.ToHandle(&code);
    DCHECK(
        // During bootstrapping some of these maps could be not created yet.
        (*map == context->get(Context::STRICT_FUNCTION_MAP_INDEX)) ||
        (*map ==
         context->get(Context::STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX)) ||
        (*map ==
         context->get(
             Context::STRICT_FUNCTION_WITH_READONLY_PROTOTYPE_MAP_INDEX)) ||
        // Check if it's a creation of an empty or Proxy function during
        // bootstrapping.
        (has_code && (code->builtin_index() == Builtins::kEmptyFunction ||
                      code->builtin_index() == Builtins::kProxyConstructor)));
  } else {
    DCHECK(
        (*map == *isolate()->sloppy_function_map()) ||
        (*map == *isolate()->sloppy_function_without_prototype_map()) ||
        (*map == *isolate()->sloppy_function_with_readonly_prototype_map()) ||
        (*map == *isolate()->strict_function_map()) ||
        (*map == *isolate()->strict_function_without_prototype_map()) ||
        (*map == *isolate()->native_function_map()));
  }
#endif
  return NewFunction(map, info, context);
}


Handle<JSFunction> Factory::NewFunction(Handle<String> name) {
  Handle<JSFunction> result =
      NewFunction(isolate()->sloppy_function_map(), name, MaybeHandle<Code>());
  DCHECK(is_sloppy(result->shared()->language_mode()));
  return result;
}

Handle<JSFunction> Factory::NewFunctionWithoutPrototype(
    Handle<String> name, Handle<Code> code, LanguageMode language_mode) {
  Handle<Map> map = is_strict(language_mode)
                        ? isolate()->strict_function_without_prototype_map()
                        : isolate()->sloppy_function_without_prototype_map();
  Handle<JSFunction> result = NewFunction(map, name, code);
  result->shared()->set_language_mode(language_mode);
  return result;
}

Handle<JSFunction> Factory::NewFunction(Handle<String> name, Handle<Code> code,
                                        Handle<Object> prototype,
                                        LanguageMode language_mode,
                                        MutableMode prototype_mutability) {
  Handle<Map> map;
  if (prototype_mutability == MUTABLE) {
    map = is_strict(language_mode) ? isolate()->strict_function_map()
                                   : isolate()->sloppy_function_map();
  } else {
    map = is_strict(language_mode)
              ? isolate()->strict_function_with_readonly_prototype_map()
              : isolate()->sloppy_function_with_readonly_prototype_map();
  }
  Handle<JSFunction> result = NewFunction(map, name, code);
  result->set_prototype_or_initial_map(*prototype);
  result->shared()->set_language_mode(language_mode);
  return result;
}

Handle<JSFunction> Factory::NewFunction(Handle<String> name, Handle<Code> code,
                                        Handle<Object> prototype,
                                        InstanceType type, int instance_size,
                                        int inobject_properties,
                                        LanguageMode language_mode,
                                        MutableMode prototype_mutability) {
  // Allocate the function
  Handle<JSFunction> function =
      NewFunction(name, code, prototype, language_mode, prototype_mutability);

  ElementsKind elements_kind =
      type == JS_ARRAY_TYPE ? PACKED_SMI_ELEMENTS : TERMINAL_FAST_ELEMENTS_KIND;
  Handle<Map> initial_map =
      NewMap(type, instance_size, elements_kind, inobject_properties);
  // TODO(littledan): Why do we have this is_generator test when
  // NewFunctionPrototype already handles finding an appropriately
  // shared prototype?
  if (!IsResumableFunction(function->shared()->kind())) {
    if (prototype->IsTheHole(isolate())) {
      prototype = NewFunctionPrototype(function);
    }
  }
  JSFunction::SetInitialMap(function, initial_map, prototype);
  return function;
}

Handle<JSFunction> Factory::NewFunction(Handle<String> name, Handle<Code> code,
                                        InstanceType type, int instance_size,
                                        int inobject_properties) {
  DCHECK(isolate()->bootstrapper()->IsActive());
  return NewFunction(name, code, the_hole_value(), type, instance_size,
                     inobject_properties, LanguageMode::kStrict);
}


Handle<JSObject> Factory::NewFunctionPrototype(Handle<JSFunction> function) {
  // Make sure to use globals from the function's context, since the function
  // can be from a different context.
  Handle<Context> native_context(function->context()->native_context());
  Handle<Map> new_map;
  if (V8_UNLIKELY(IsAsyncGeneratorFunction(function->shared()->kind()))) {
    new_map = handle(native_context->async_generator_object_prototype_map());
  } else if (IsResumableFunction(function->shared()->kind())) {
    // Generator and async function prototypes can share maps since they
    // don't have "constructor" properties.
    new_map = handle(native_context->generator_object_prototype_map());
  } else {
    // Each function prototype gets a fresh map to avoid unwanted sharing of
    // maps between prototypes of different constructors.
    Handle<JSFunction> object_function(native_context->object_function());
    DCHECK(object_function->has_initial_map());
    new_map = handle(object_function->initial_map());
  }

  DCHECK(!new_map->is_prototype_map());
  Handle<JSObject> prototype = NewJSObjectFromMap(new_map);

  if (!IsResumableFunction(function->shared()->kind())) {
    JSObject::AddProperty(prototype, constructor_string(), function, DONT_ENUM);
  }

  return prototype;
}


Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
    Handle<SharedFunctionInfo> info,
    Handle<Context> context,
    PretenureFlag pretenure) {
  Handle<Map> initial_map(
      Map::cast(context->native_context()->get(info->function_map_index())));
  return NewFunctionFromSharedFunctionInfo(initial_map, info, context,
                                           pretenure);
}

Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
    Handle<SharedFunctionInfo> info, Handle<Context> context,
    Handle<Cell> vector, PretenureFlag pretenure) {
  Handle<Map> initial_map(
      Map::cast(context->native_context()->get(info->function_map_index())));
  return NewFunctionFromSharedFunctionInfo(initial_map, info, context, vector,
                                           pretenure);
}

Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
    Handle<Map> initial_map, Handle<SharedFunctionInfo> info,
    Handle<Object> context_or_undefined, PretenureFlag pretenure) {
  DCHECK_EQ(JS_FUNCTION_TYPE, initial_map->instance_type());
  Handle<JSFunction> result =
      NewFunction(initial_map, info, context_or_undefined, pretenure);

  if (context_or_undefined->IsContext()) {
    // Give compiler a chance to pre-initialize.
    Compiler::PostInstantiation(result, pretenure);
  }

  return result;
}

Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
    Handle<Map> initial_map, Handle<SharedFunctionInfo> info,
    Handle<Object> context_or_undefined, Handle<Cell> vector,
    PretenureFlag pretenure) {
  DCHECK_EQ(JS_FUNCTION_TYPE, initial_map->instance_type());
  Handle<JSFunction> result =
      NewFunction(initial_map, info, context_or_undefined, pretenure);

  // Bump the closure count that is encoded in the vector cell's map.
  if (vector->map() == *no_closures_cell_map()) {
    vector->set_map(*one_closure_cell_map());
  } else if (vector->map() == *one_closure_cell_map()) {
    vector->set_map(*many_closures_cell_map());
  } else {
    DCHECK_EQ(vector->map(), *many_closures_cell_map());
  }

  // Check that the optimized code in the feedback vector wasn't marked for
  // deoptimization while not pointed to by any live JSFunction.
  if (vector->value()->IsFeedbackVector()) {
    FeedbackVector::cast(vector->value())
        ->EvictOptimizedCodeMarkedForDeoptimization(
            *info, "new function from shared function info");
  }
  result->set_feedback_vector_cell(*vector);

  if (context_or_undefined->IsContext()) {
    // Give compiler a chance to pre-initialize.
    Compiler::PostInstantiation(result, pretenure);
  }

  return result;
}

Handle<ScopeInfo> Factory::NewScopeInfo(int length) {
  Handle<FixedArray> array = NewFixedArray(length, TENURED);
  array->set_map_no_write_barrier(*scope_info_map());
  Handle<ScopeInfo> scope_info = Handle<ScopeInfo>::cast(array);
  return scope_info;
}

Handle<ModuleInfo> Factory::NewModuleInfo() {
  Handle<FixedArray> array = NewFixedArray(ModuleInfo::kLength, TENURED);
  array->set_map_no_write_barrier(*module_info_map());
  return Handle<ModuleInfo>::cast(array);
}

Handle<PreParsedScopeData> Factory::NewPreParsedScopeData() {
  Handle<PreParsedScopeData> result =
      Handle<PreParsedScopeData>::cast(NewStruct(TUPLE2_TYPE, TENURED));
  result->set_scope_data(PodArray<uint8_t>::cast(*empty_byte_array()));
  result->set_child_data(*empty_fixed_array());
  return result;
}

Handle<JSObject> Factory::NewExternal(void* value) {
  Handle<Foreign> foreign = NewForeign(static_cast<Address>(value));
  Handle<JSObject> external = NewJSObjectFromMap(external_map());
  external->SetEmbedderField(0, *foreign);
  return external;
}

Handle<CodeDataContainer> Factory::NewCodeDataContainer(int flags) {
  Handle<CodeDataContainer> data_container =
      New<CodeDataContainer>(code_data_container_map(), OLD_SPACE);
  data_container->set_next_code_link(*undefined_value(), SKIP_WRITE_BARRIER);
  data_container->set_kind_specific_flags(flags);
  data_container->clear_padding();
  return data_container;
}

Handle<Code> Factory::NewCodeRaw(int object_size, bool immovable) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->AllocateCode(object_size, immovable),
                     Code);
}

Handle<Code> Factory::NewCode(
    const CodeDesc& desc, Code::Kind kind, Handle<Object> self_ref,
    MaybeHandle<HandlerTable> maybe_handler_table,
    MaybeHandle<ByteArray> maybe_source_position_table,
    MaybeHandle<DeoptimizationData> maybe_deopt_data, bool immovable,
    uint32_t stub_key, bool is_turbofanned, int stack_slots,
    int safepoint_table_offset) {
  Handle<ByteArray> reloc_info = NewByteArray(desc.reloc_size, TENURED);
  Handle<CodeDataContainer> data_container = NewCodeDataContainer(0);

  Handle<HandlerTable> handler_table =
      maybe_handler_table.is_null() ? HandlerTable::Empty(isolate())
                                    : maybe_handler_table.ToHandleChecked();
  Handle<ByteArray> source_position_table =
      maybe_source_position_table.is_null()
          ? empty_byte_array()
          : maybe_source_position_table.ToHandleChecked();
  Handle<DeoptimizationData> deopt_data =
      maybe_deopt_data.is_null() ? DeoptimizationData::Empty(isolate())
                                 : maybe_deopt_data.ToHandleChecked();

  bool has_unwinding_info = desc.unwinding_info != nullptr;
  DCHECK((has_unwinding_info && desc.unwinding_info_size > 0) ||
         (!has_unwinding_info && desc.unwinding_info_size == 0));

  // Compute size.
  int body_size = desc.instr_size;
  int unwinding_info_size_field_size = kInt64Size;
  if (has_unwinding_info) {
    body_size = RoundUp(body_size, kInt64Size) + desc.unwinding_info_size +
                unwinding_info_size_field_size;
  }
  int obj_size = Code::SizeFor(RoundUp(body_size, kObjectAlignment));

  CodeSpaceMemoryModificationScope code_allocation(isolate()->heap());
  Handle<Code> code = NewCodeRaw(obj_size, immovable);
  DCHECK(!isolate()->heap()->memory_allocator()->code_range()->valid() ||
         isolate()->heap()->memory_allocator()->code_range()->contains(
             code->address()) ||
         obj_size <= isolate()->heap()->code_space()->AreaSize());

  // The code object has not been fully initialized yet.  We rely on the
  // fact that no allocation will happen from this point on.
  DisallowHeapAllocation no_gc;
  code->set_instruction_size(desc.instr_size);
  code->set_relocation_info(*reloc_info);
  code->initialize_flags(kind);
  code->set_has_unwinding_info(has_unwinding_info);
  code->set_is_turbofanned(is_turbofanned);
  code->set_stack_slots(stack_slots);
  code->set_safepoint_table_offset(safepoint_table_offset);
  code->set_code_data_container(*data_container);
  code->set_has_tagged_params(true);
  code->set_deoptimization_data(*deopt_data);
  code->set_stub_key(stub_key);
  code->set_handler_table(*handler_table);
  code->set_source_position_table(*source_position_table);
  code->set_protected_instructions(*empty_fixed_array(), SKIP_WRITE_BARRIER);
  code->set_constant_pool_offset(desc.instr_size - desc.constant_pool_size);
  code->set_builtin_index(-1);
  code->set_trap_handler_index(Smi::FromInt(-1));

  switch (code->kind()) {
    case Code::OPTIMIZED_FUNCTION:
      code->set_marked_for_deoptimization(false);
      break;
    case Code::JS_TO_WASM_FUNCTION:
    case Code::WASM_FUNCTION:
      code->set_has_tagged_params(false);
      break;
    default:
      break;
  }

  // Allow self references to created code object by patching the handle to
  // point to the newly allocated Code object.
  if (!self_ref.is_null()) *(self_ref.location()) = *code;

  // Migrate generated code.
  // The generated code can contain Object** values (typically from handles)
  // that are dereferenced during the copy to point directly to the actual heap
  // objects. These pointers can include references to the code object itself,
  // through the self_reference parameter.
  code->CopyFrom(desc);

  code->clear_padding();

#ifdef VERIFY_HEAP
  if (FLAG_verify_heap) code->ObjectVerify();
#endif
  return code;
}

Handle<Code> Factory::NewCodeForDeserialization(uint32_t size) {
  const bool kNotImmovable = false;
  return NewCodeRaw(size, kNotImmovable);
}

Handle<Code> Factory::CopyCode(Handle<Code> code) {
  Handle<CodeDataContainer> data_container =
      NewCodeDataContainer(code->code_data_container()->kind_specific_flags());
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyCode(*code, *data_container), Code);
}


Handle<BytecodeArray> Factory::CopyBytecodeArray(
    Handle<BytecodeArray> bytecode_array) {
  CALL_HEAP_FUNCTION(isolate(),
                     isolate()->heap()->CopyBytecodeArray(*bytecode_array),
                     BytecodeArray);
}

Handle<JSObject> Factory::NewJSObject(Handle<JSFunction> constructor,
                                      PretenureFlag pretenure) {
  JSFunction::EnsureHasInitialMap(constructor);
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateJSObject(*constructor, pretenure), JSObject);
}

Handle<JSObject> Factory::NewJSObjectWithNullProto(PretenureFlag pretenure) {
  Handle<JSObject> result =
      NewJSObject(isolate()->object_function(), pretenure);
  Handle<Map> new_map =
      Map::Copy(Handle<Map>(result->map()), "ObjectWithNullProto");
  Map::SetPrototype(new_map, null_value());
  JSObject::MigrateToMap(result, new_map);
  return result;
}

Handle<JSGlobalObject> Factory::NewJSGlobalObject(
    Handle<JSFunction> constructor) {
  DCHECK(constructor->has_initial_map());
  Handle<Map> map(constructor->initial_map());
  DCHECK(map->is_dictionary_map());

  // Make sure no field properties are described in the initial map.
  // This guarantees us that normalizing the properties does not
  // require us to change property values to PropertyCells.
  DCHECK_EQ(map->NextFreePropertyIndex(), 0);

  // Make sure we don't have a ton of pre-allocated slots in the
  // global objects. They will be unused once we normalize the object.
  DCHECK_EQ(map->UnusedPropertyFields(), 0);
  DCHECK_EQ(map->GetInObjectProperties(), 0);

  // Initial size of the backing store to avoid resize of the storage during
  // bootstrapping. The size differs between the JS global object ad the
  // builtins object.
  int initial_size = 64;

  // Allocate a dictionary object for backing storage.
  int at_least_space_for = map->NumberOfOwnDescriptors() * 2 + initial_size;
  Handle<GlobalDictionary> dictionary =
      GlobalDictionary::New(isolate(), at_least_space_for);

  // The global object might be created from an object template with accessors.
  // Fill these accessors into the dictionary.
  Handle<DescriptorArray> descs(map->instance_descriptors());
  for (int i = 0; i < map->NumberOfOwnDescriptors(); i++) {
    PropertyDetails details = descs->GetDetails(i);
    // Only accessors are expected.
    DCHECK_EQ(kAccessor, details.kind());
    PropertyDetails d(kAccessor, details.attributes(),
                      PropertyCellType::kMutable);
    Handle<Name> name(descs->GetKey(i));
    Handle<PropertyCell> cell = NewPropertyCell(name);
    cell->set_value(descs->GetValue(i));
    // |dictionary| already contains enough space for all properties.
    USE(GlobalDictionary::Add(dictionary, name, cell, d));
  }

  // Allocate the global object and initialize it with the backing store.
  Handle<JSGlobalObject> global = New<JSGlobalObject>(map, OLD_SPACE);
  isolate()->heap()->InitializeJSObjectFromMap(*global, *dictionary, *map);

  // Create a new map for the global object.
  Handle<Map> new_map = Map::CopyDropDescriptors(map);
  new_map->set_may_have_interesting_symbols(true);
  new_map->set_dictionary_map(true);

  // Set up the global object as a normalized object.
  global->set_global_dictionary(*dictionary);
  global->synchronized_set_map(*new_map);

  // Make sure result is a global object with properties in dictionary.
  DCHECK(global->IsJSGlobalObject() && !global->HasFastProperties());
  return global;
}


Handle<JSObject> Factory::NewJSObjectFromMap(
    Handle<Map> map,
    PretenureFlag pretenure,
    Handle<AllocationSite> allocation_site) {
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateJSObjectFromMap(
          *map, pretenure,
          allocation_site.is_null() ? nullptr : *allocation_site),
      JSObject);
}

Handle<JSObject> Factory::NewSlowJSObjectFromMap(Handle<Map> map, int capacity,
                                                 PretenureFlag pretenure) {
  DCHECK(map->is_dictionary_map());
  Handle<NameDictionary> object_properties =
      NameDictionary::New(isolate(), capacity);
  Handle<JSObject> js_object = NewJSObjectFromMap(map, pretenure);
  js_object->set_raw_properties_or_hash(*object_properties);
  return js_object;
}

Handle<JSArray> Factory::NewJSArray(ElementsKind elements_kind,
                                    PretenureFlag pretenure) {
  Context* native_context = isolate()->raw_native_context();
  Map* map = native_context->GetInitialJSArrayMap(elements_kind);
  if (map == nullptr) {
    JSFunction* array_function = native_context->array_function();
    map = array_function->initial_map();
  }
  return Handle<JSArray>::cast(NewJSObjectFromMap(handle(map), pretenure));
}

Handle<JSArray> Factory::NewJSArray(ElementsKind elements_kind, int length,
                                    int capacity,
                                    ArrayStorageAllocationMode mode,
                                    PretenureFlag pretenure) {
  Handle<JSArray> array = NewJSArray(elements_kind, pretenure);
  NewJSArrayStorage(array, length, capacity, mode);
  return array;
}

Handle<JSArray> Factory::NewJSArrayWithElements(Handle<FixedArrayBase> elements,
                                                ElementsKind elements_kind,
                                                int length,
                                                PretenureFlag pretenure) {
  DCHECK(length <= elements->length());
  Handle<JSArray> array = NewJSArray(elements_kind, pretenure);

  array->set_elements(*elements);
  array->set_length(Smi::FromInt(length));
  JSObject::ValidateElements(*array);
  return array;
}


void Factory::NewJSArrayStorage(Handle<JSArray> array,
                                int length,
                                int capacity,
                                ArrayStorageAllocationMode mode) {
  DCHECK(capacity >= length);

  if (capacity == 0) {
    array->set_length(Smi::kZero);
    array->set_elements(*empty_fixed_array());
    return;
  }

  HandleScope inner_scope(isolate());
  Handle<FixedArrayBase> elms;
  ElementsKind elements_kind = array->GetElementsKind();
  if (IsDoubleElementsKind(elements_kind)) {
    if (mode == DONT_INITIALIZE_ARRAY_ELEMENTS) {
      elms = NewFixedDoubleArray(capacity);
    } else {
      DCHECK(mode == INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
      elms = NewFixedDoubleArrayWithHoles(capacity);
    }
  } else {
    DCHECK(IsSmiOrObjectElementsKind(elements_kind));
    if (mode == DONT_INITIALIZE_ARRAY_ELEMENTS) {
      elms = NewUninitializedFixedArray(capacity);
    } else {
      DCHECK(mode == INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
      elms = NewFixedArrayWithHoles(capacity);
    }
  }

  array->set_elements(*elms);
  array->set_length(Smi::FromInt(length));
}

Handle<JSModuleNamespace> Factory::NewJSModuleNamespace() {
  Handle<Map> map = isolate()->js_module_namespace_map();
  Handle<JSModuleNamespace> module_namespace(
      Handle<JSModuleNamespace>::cast(NewJSObjectFromMap(map)));
  FieldIndex index = FieldIndex::ForDescriptor(
      *map, JSModuleNamespace::kToStringTagFieldIndex);
  module_namespace->FastPropertyAtPut(index,
                                      isolate()->heap()->Module_string());
  return module_namespace;
}

Handle<JSGeneratorObject> Factory::NewJSGeneratorObject(
    Handle<JSFunction> function) {
  DCHECK(IsResumableFunction(function->shared()->kind()));
  JSFunction::EnsureHasInitialMap(function);
  Handle<Map> map(function->initial_map());

  DCHECK(map->instance_type() == JS_GENERATOR_OBJECT_TYPE ||
         map->instance_type() == JS_ASYNC_GENERATOR_OBJECT_TYPE);

  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateJSObjectFromMap(*map),
      JSGeneratorObject);
}

Handle<Module> Factory::NewModule(Handle<SharedFunctionInfo> code) {
  Handle<ModuleInfo> module_info(code->scope_info()->ModuleDescriptorInfo(),
                                 isolate());
  Handle<ObjectHashTable> exports =
      ObjectHashTable::New(isolate(), module_info->RegularExportCount());
  Handle<FixedArray> regular_exports =
      NewFixedArray(module_info->RegularExportCount());
  Handle<FixedArray> regular_imports =
      NewFixedArray(module_info->regular_imports()->length());
  int requested_modules_length = module_info->module_requests()->length();
  Handle<FixedArray> requested_modules =
      requested_modules_length > 0 ? NewFixedArray(requested_modules_length)
                                   : empty_fixed_array();

  Handle<Module> module = Handle<Module>::cast(NewStruct(MODULE_TYPE, TENURED));
  module->set_code(*code);
  module->set_exports(*exports);
  module->set_regular_exports(*regular_exports);
  module->set_regular_imports(*regular_imports);
  module->set_hash(isolate()->GenerateIdentityHash(Smi::kMaxValue));
  module->set_module_namespace(isolate()->heap()->undefined_value());
  module->set_requested_modules(*requested_modules);
  module->set_script(Script::cast(code->script()));
  module->set_status(Module::kUninstantiated);
  module->set_exception(isolate()->heap()->the_hole_value());
  module->set_import_meta(isolate()->heap()->the_hole_value());
  module->set_dfs_index(-1);
  module->set_dfs_ancestor_index(-1);
  return module;
}

Handle<JSArrayBuffer> Factory::NewJSArrayBuffer(SharedFlag shared,
                                                PretenureFlag pretenure) {
  Handle<JSFunction> array_buffer_fun(
      shared == SharedFlag::kShared
          ? isolate()->native_context()->shared_array_buffer_fun()
          : isolate()->native_context()->array_buffer_fun());
  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateJSObject(
                                    *array_buffer_fun, pretenure),
                     JSArrayBuffer);
}


Handle<JSDataView> Factory::NewJSDataView() {
  Handle<JSFunction> data_view_fun(
      isolate()->native_context()->data_view_fun());
  CALL_HEAP_FUNCTION(
      isolate(),
      isolate()->heap()->AllocateJSObject(*data_view_fun),
      JSDataView);
}

Handle<JSIteratorResult> Factory::NewJSIteratorResult(Handle<Object> value,
                                                      bool done) {
  Handle<Map> map(isolate()->native_context()->iterator_result_map());
  Handle<JSIteratorResult> js_iter_result =
      Handle<JSIteratorResult>::cast(NewJSObjectFromMap(map));
  js_iter_result->set_value(*value);
  js_iter_result->set_done(*ToBoolean(done));
  return js_iter_result;
}

Handle<JSAsyncFromSyncIterator> Factory::NewJSAsyncFromSyncIterator(
    Handle<JSReceiver> sync_iterator) {
  Handle<Map> map(isolate()->native_context()->async_from_sync_iterator_map());
  Handle<JSAsyncFromSyncIterator> iterator =
      Handle<JSAsyncFromSyncIterator>::cast(NewJSObjectFromMap(map));

  iterator->set_sync_iterator(*sync_iterator);
  return iterator;
}

Handle<JSMap> Factory::NewJSMap() {
  Handle<Map> map(isolate()->native_context()->js_map_map());
  Handle<JSMap> js_map = Handle<JSMap>::cast(NewJSObjectFromMap(map));
  JSMap::Initialize(js_map, isolate());
  return js_map;
}


Handle<JSSet> Factory::NewJSSet() {
  Handle<Map> map(isolate()->native_context()->js_set_map());
  Handle<JSSet> js_set = Handle<JSSet>::cast(NewJSObjectFromMap(map));
  JSSet::Initialize(js_set, isolate());
  return js_set;
}

Handle<JSMapIterator> Factory::NewJSMapIterator(Handle<Map> map,
                                                Handle<OrderedHashMap> table,
                                                int index) {
  Handle<JSMapIterator> result =
      Handle<JSMapIterator>::cast(NewJSObjectFromMap(map));
  result->set_table(*table);
  result->set_index(Smi::FromInt(index));
  return result;
}

Handle<JSSetIterator> Factory::NewJSSetIterator(Handle<Map> map,
                                                Handle<OrderedHashSet> table,
                                                int index) {
  Handle<JSSetIterator> result =
      Handle<JSSetIterator>::cast(NewJSObjectFromMap(map));
  result->set_table(*table);
  result->set_index(Smi::FromInt(index));
  return result;
}

ExternalArrayType Factory::GetArrayTypeFromElementsKind(ElementsKind kind) {
  switch (kind) {
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case TYPE##_ELEMENTS:                                 \
    return kExternal##Type##Array;
    TYPED_ARRAYS(TYPED_ARRAY_CASE)
    default:
      UNREACHABLE();
  }
#undef TYPED_ARRAY_CASE
}

size_t Factory::GetExternalArrayElementSize(ExternalArrayType type) {
  switch (type) {
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case kExternal##Type##Array:                          \
    return size;
    TYPED_ARRAYS(TYPED_ARRAY_CASE)
    default:
      UNREACHABLE();
  }
#undef TYPED_ARRAY_CASE
}

namespace {

ElementsKind GetExternalArrayElementsKind(ExternalArrayType type) {
  switch (type) {
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case kExternal##Type##Array:                          \
    return TYPE##_ELEMENTS;
    TYPED_ARRAYS(TYPED_ARRAY_CASE)
  }
  UNREACHABLE();
#undef TYPED_ARRAY_CASE
}

size_t GetFixedTypedArraysElementSize(ElementsKind kind) {
  switch (kind) {
#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size) \
  case TYPE##_ELEMENTS:                                 \
    return size;
    TYPED_ARRAYS(TYPED_ARRAY_CASE)
    default:
      UNREACHABLE();
  }
#undef TYPED_ARRAY_CASE
}


JSFunction* GetTypedArrayFun(ExternalArrayType type, Isolate* isolate) {
  Context* native_context = isolate->context()->native_context();
  switch (type) {
#define TYPED_ARRAY_FUN(Type, type, TYPE, ctype, size)                        \
    case kExternal##Type##Array:                                              \
      return native_context->type##_array_fun();

    TYPED_ARRAYS(TYPED_ARRAY_FUN)
#undef TYPED_ARRAY_FUN

    default:
      UNREACHABLE();
  }
}


JSFunction* GetTypedArrayFun(ElementsKind elements_kind, Isolate* isolate) {
  Context* native_context = isolate->context()->native_context();
  switch (elements_kind) {
#define TYPED_ARRAY_FUN(Type, type, TYPE, ctype, size) \
  case TYPE##_ELEMENTS:                                \
    return native_context->type##_array_fun();

    TYPED_ARRAYS(TYPED_ARRAY_FUN)
#undef TYPED_ARRAY_FUN

    default:
      UNREACHABLE();
  }
}


void SetupArrayBufferView(i::Isolate* isolate,
                          i::Handle<i::JSArrayBufferView> obj,
                          i::Handle<i::JSArrayBuffer> buffer,
                          size_t byte_offset, size_t byte_length,
                          PretenureFlag pretenure = NOT_TENURED) {
  DCHECK(byte_offset + byte_length <=
         static_cast<size_t>(buffer->byte_length()->Number()));

  DCHECK_EQ(obj->GetEmbedderFieldCount(),
            v8::ArrayBufferView::kEmbedderFieldCount);
  for (int i = 0; i < v8::ArrayBufferView::kEmbedderFieldCount; i++) {
    obj->SetEmbedderField(i, Smi::kZero);
  }

  obj->set_buffer(*buffer);

  i::Handle<i::Object> byte_offset_object =
      isolate->factory()->NewNumberFromSize(byte_offset, pretenure);
  obj->set_byte_offset(*byte_offset_object);

  i::Handle<i::Object> byte_length_object =
      isolate->factory()->NewNumberFromSize(byte_length, pretenure);
  obj->set_byte_length(*byte_length_object);
}


}  // namespace


Handle<JSTypedArray> Factory::NewJSTypedArray(ExternalArrayType type,
                                              PretenureFlag pretenure) {
  Handle<JSFunction> typed_array_fun_handle(GetTypedArrayFun(type, isolate()));

  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateJSObject(
                                    *typed_array_fun_handle, pretenure),
                     JSTypedArray);
}


Handle<JSTypedArray> Factory::NewJSTypedArray(ElementsKind elements_kind,
                                              PretenureFlag pretenure) {
  Handle<JSFunction> typed_array_fun_handle(
      GetTypedArrayFun(elements_kind, isolate()));

  CALL_HEAP_FUNCTION(isolate(), isolate()->heap()->AllocateJSObject(
                                    *typed_array_fun_handle, pretenure),
                     JSTypedArray);
}


Handle<JSTypedArray> Factory::NewJSTypedArray(ExternalArrayType type,
                                              Handle<JSArrayBuffer> buffer,
                                              size_t byte_offset, size_t length,
                                              PretenureFlag pretenure) {
  Handle<JSTypedArray> obj = NewJSTypedArray(type, pretenure);

  size_t element_size = GetExternalArrayElementSize(type);
  ElementsKind elements_kind = GetExternalArrayElementsKind(type);

  CHECK_EQ(byte_offset % element_size, 0);

  CHECK(length <= (std::numeric_limits<size_t>::max() / element_size));
  CHECK(length <= static_cast<size_t>(Smi::kMaxValue));
  size_t byte_length = length * element_size;
  SetupArrayBufferView(isolate(), obj, buffer, byte_offset, byte_length,
                       pretenure);

  Handle<Object> length_object = NewNumberFromSize(length, pretenure);
  obj->set_length(*length_object);

  Handle<FixedTypedArrayBase> elements = NewFixedTypedArrayWithExternalPointer(
      static_cast<int>(length), type,
      static_cast<uint8_t*>(buffer->backing_store()) + byte_offset, pretenure);
  Handle<Map> map = JSObject::GetElementsTransitionMap(obj, elements_kind);
  JSObject::SetMapAndElements(obj, map, elements);
  return obj;
}


Handle<JSTypedArray> Factory::NewJSTypedArray(ElementsKind elements_kind,
                                              size_t number_of_elements,
                                              PretenureFlag pretenure) {
  Handle<JSTypedArray> obj = NewJSTypedArray(elements_kind, pretenure);
  DCHECK_EQ(obj->GetEmbedderFieldCount(),
            v8::ArrayBufferView::kEmbedderFieldCount);
  for (int i = 0; i < v8::ArrayBufferView::kEmbedderFieldCount; i++) {
    obj->SetEmbedderField(i, Smi::kZero);
  }

  size_t element_size = GetFixedTypedArraysElementSize(elements_kind);
  ExternalArrayType array_type = GetArrayTypeFromElementsKind(elements_kind);

  CHECK(number_of_elements <=
        (std::numeric_limits<size_t>::max() / element_size));
  CHECK(number_of_elements <= static_cast<size_t>(Smi::kMaxValue));
  size_t byte_length = number_of_elements * element_size;

  obj->set_byte_offset(Smi::kZero);
  i::Handle<i::Object> byte_length_object =
      NewNumberFromSize(byte_length, pretenure);
  obj->set_byte_length(*byte_length_object);
  Handle<Object> length_object =
      NewNumberFromSize(number_of_elements, pretenure);
  obj->set_length(*length_object);

  Handle<JSArrayBuffer> buffer =
      NewJSArrayBuffer(SharedFlag::kNotShared, pretenure);
  JSArrayBuffer::Setup(buffer, isolate(), true, nullptr, byte_length,
                       SharedFlag::kNotShared);
  obj->set_buffer(*buffer);
  Handle<FixedTypedArrayBase> elements = NewFixedTypedArray(
      static_cast<int>(number_of_elements), array_type, true, pretenure);
  obj->set_elements(*elements);
  return obj;
}


Handle<JSDataView> Factory::NewJSDataView(Handle<JSArrayBuffer> buffer,
                                          size_t byte_offset,
                                          size_t byte_length) {
  Handle<JSDataView> obj = NewJSDataView();
  SetupArrayBufferView(isolate(), obj, buffer, byte_offset, byte_length);
  return obj;
}


MaybeHandle<JSBoundFunction> Factory::NewJSBoundFunction(
    Handle<JSReceiver> target_function, Handle<Object> bound_this,
    Vector<Handle<Object>> bound_args) {
  DCHECK(target_function->IsCallable());
  STATIC_ASSERT(Code::kMaxArguments <= FixedArray::kMaxLength);
  if (bound_args.length() >= Code::kMaxArguments) {
    THROW_NEW_ERROR(isolate(),
                    NewRangeError(MessageTemplate::kTooManyArguments),
                    JSBoundFunction);
  }

  // Determine the prototype of the {target_function}.
  Handle<Object> prototype;
  ASSIGN_RETURN_ON_EXCEPTION(
      isolate(), prototype,
      JSReceiver::GetPrototype(isolate(), target_function), JSBoundFunction);

  SaveContext save(isolate());
  isolate()->set_context(*target_function->GetCreationContext());

  // Create the [[BoundArguments]] for the result.
  Handle<FixedArray> bound_arguments;
  if (bound_args.length() == 0) {
    bound_arguments = empty_fixed_array();
  } else {
    bound_arguments = NewFixedArray(bound_args.length());
    for (int i = 0; i < bound_args.length(); ++i) {
      bound_arguments->set(i, *bound_args[i]);
    }
  }

  // Setup the map for the JSBoundFunction instance.
  Handle<Map> map = target_function->IsConstructor()
                        ? isolate()->bound_function_with_constructor_map()
                        : isolate()->bound_function_without_constructor_map();
  if (map->prototype() != *prototype) {
    map = Map::TransitionToPrototype(map, prototype);
  }
  DCHECK_EQ(target_function->IsConstructor(), map->is_constructor());

  // Setup the JSBoundFunction instance.
  Handle<JSBoundFunction> result =
      Handle<JSBoundFunction>::cast(NewJSObjectFromMap(map));
  result->set_bound_target_function(*target_function);
  result->set_bound_this(*bound_this);
  result->set_bound_arguments(*bound_arguments);
  return result;
}


// ES6 section 9.5.15 ProxyCreate (target, handler)
Handle<JSProxy> Factory::NewJSProxy(Handle<JSReceiver> target,
                                    Handle<JSReceiver> handler) {
  // Allocate the proxy object.
  Handle<Map> map;
  if (target->IsCallable()) {
    if (target->IsConstructor()) {
      map = Handle<Map>(isolate()->proxy_constructor_map());
    } else {
      map = Handle<Map>(isolate()->proxy_callable_map());
    }
  } else {
    map = Handle<Map>(isolate()->proxy_map());
  }
  DCHECK(map->prototype()->IsNull(isolate()));
  Handle<JSProxy> result = New<JSProxy>(map, NEW_SPACE);
  result->initialize_properties();
  result->set_target(*target);
  result->set_handler(*handler);
  return result;
}

Handle<JSGlobalProxy> Factory::NewUninitializedJSGlobalProxy(int size) {
  // Create an empty shell of a JSGlobalProxy that needs to be reinitialized
  // via ReinitializeJSGlobalProxy later.
  Handle<Map> map = NewMap(JS_GLOBAL_PROXY_TYPE, size);
  // Maintain invariant expected from any JSGlobalProxy.
  map->set_is_access_check_needed(true);
  map->set_may_have_interesting_symbols(true);
  CALL_HEAP_FUNCTION(
      isolate(), isolate()->heap()->AllocateJSObjectFromMap(*map, NOT_TENURED),
      JSGlobalProxy);
}


void Factory::ReinitializeJSGlobalProxy(Handle<JSGlobalProxy> object,
                                        Handle<JSFunction> constructor) {
  DCHECK(constructor->has_initial_map());
  Handle<Map> map(constructor->initial_map(), isolate());
  Handle<Map> old_map(object->map(), isolate());

  // The proxy's hash should be retained across reinitialization.
  Handle<Object> raw_properties_or_hash(object->raw_properties_or_hash(),
                                        isolate());

  if (old_map->is_prototype_map()) {
    map = Map::Copy(map, "CopyAsPrototypeForJSGlobalProxy");
    map->set_is_prototype_map(true);
  }
  JSObject::NotifyMapChange(old_map, map, isolate());
  old_map->NotifyLeafMapLayoutChange();

  // Check that the already allocated object has the same size and type as
  // objects allocated using the constructor.
  DCHECK(map->instance_size() == old_map->instance_size());
  DCHECK(map->instance_type() == old_map->instance_type());

  // In order to keep heap in consistent state there must be no allocations
  // before object re-initialization is finished.
  DisallowHeapAllocation no_allocation;

  // Reset the map for the object.
  object->synchronized_set_map(*map);

  Heap* heap = isolate()->heap();
  // Reinitialize the object from the constructor map.
  heap->InitializeJSObjectFromMap(*object, *raw_properties_or_hash, *map);
}

Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfo(
    MaybeHandle<String> name, FunctionKind kind, Handle<Code> code,
    Handle<ScopeInfo> scope_info) {
  DCHECK(IsValidFunctionKind(kind));
  Handle<SharedFunctionInfo> shared =
      NewSharedFunctionInfo(name, code, IsConstructable(kind), kind);
  shared->set_scope_info(*scope_info);
  shared->set_outer_scope_info(*the_hole_value());
  if (IsGeneratorFunction(kind)) {
    shared->set_instance_class_name(isolate()->heap()->Generator_string());
  }
  return shared;
}

Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfoForLiteral(
    FunctionLiteral* literal, Handle<Script> script) {
  Handle<Code> code = BUILTIN_CODE(isolate(), CompileLazy);
  Handle<ScopeInfo> scope_info(ScopeInfo::Empty(isolate()));
  Handle<SharedFunctionInfo> result =
      NewSharedFunctionInfo(literal->name(), literal->kind(), code, scope_info);
  SharedFunctionInfo::InitFromFunctionLiteral(result, literal);
  SharedFunctionInfo::SetScript(result, script, false);
  return result;
}

Handle<JSMessageObject> Factory::NewJSMessageObject(
    MessageTemplate::Template message, Handle<Object> argument,
    int start_position, int end_position, Handle<Object> script,
    Handle<Object> stack_frames) {
  Handle<Map> map = message_object_map();
  Handle<JSMessageObject> message_obj = New<JSMessageObject>(map, NEW_SPACE);
  message_obj->set_raw_properties_or_hash(*empty_fixed_array(),
                                          SKIP_WRITE_BARRIER);
  message_obj->initialize_elements();
  message_obj->set_elements(*empty_fixed_array(), SKIP_WRITE_BARRIER);
  message_obj->set_type(message);
  message_obj->set_argument(*argument);
  message_obj->set_start_position(start_position);
  message_obj->set_end_position(end_position);
  message_obj->set_script(*script);
  message_obj->set_stack_frames(*stack_frames);
  message_obj->set_error_level(v8::Isolate::kMessageError);
  return message_obj;
}

Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfo(
    MaybeHandle<String> maybe_name, MaybeHandle<Code> maybe_code,
    bool is_constructor, FunctionKind kind) {
  // Function names are assumed to be flat elsewhere. Must flatten before
  // allocating SharedFunctionInfo to avoid GC seeing the uninitialized SFI.
  Handle<String> shared_name;
  bool has_shared_name = maybe_name.ToHandle(&shared_name);
  if (has_shared_name) {
    shared_name = String::Flatten(shared_name, TENURED);
  }

  Handle<Map> map = shared_function_info_map();
  Handle<SharedFunctionInfo> share = New<SharedFunctionInfo>(map, OLD_SPACE);

  // Set pointer fields.
  share->set_raw_name(has_shared_name
                          ? *shared_name
                          : SharedFunctionInfo::kNoSharedNameSentinel);
  Handle<Code> code;
  if (!maybe_code.ToHandle(&code)) {
    code = BUILTIN_CODE(isolate(), Illegal);
  }
  Object* function_data =
      (code->is_builtin() && Builtins::IsLazy(code->builtin_index()))
          ? Smi::FromInt(code->builtin_index())
          : Object::cast(*undefined_value());
  share->set_function_data(function_data, SKIP_WRITE_BARRIER);
  share->set_code(*code);
  share->set_scope_info(ScopeInfo::Empty(isolate()));
  share->set_outer_scope_info(*the_hole_value());
  Handle<Code> construct_stub =
      is_constructor ? isolate()->builtins()->JSConstructStubGeneric()
                     : BUILTIN_CODE(isolate(), ConstructedNonConstructable);
  share->SetConstructStub(*construct_stub);
  share->set_instance_class_name(*Object_string());
  share->set_script(*undefined_value(), SKIP_WRITE_BARRIER);
  share->set_debug_info(Smi::kZero, SKIP_WRITE_BARRIER);
  share->set_function_identifier(*undefined_value(), SKIP_WRITE_BARRIER);
  StaticFeedbackVectorSpec empty_spec;
  Handle<FeedbackMetadata> feedback_metadata =
      FeedbackMetadata::New(isolate(), &empty_spec);
  share->set_feedback_metadata(*feedback_metadata, SKIP_WRITE_BARRIER);
  share->set_function_literal_id(FunctionLiteral::kIdTypeInvalid);
#if V8_SFI_HAS_UNIQUE_ID
  share->set_unique_id(isolate()->GetNextUniqueSharedFunctionInfoId());
#endif

  // Set integer fields (smi or int, depending on the architecture).
  share->set_length(0);
  share->set_internal_formal_parameter_count(0);
  share->set_expected_nof_properties(0);
  share->set_start_position_and_type(0);
  share->set_end_position(0);
  share->set_function_token_position(0);
  // All compiler hints default to false or 0.
  share->set_compiler_hints(0);
  share->set_kind(kind);

  share->set_preparsed_scope_data(*null_value());

  share->clear_padding();

  // Link into the list.
  Handle<Object> new_noscript_list =
      WeakFixedArray::Add(noscript_shared_function_infos(), share);
  isolate()->heap()->set_noscript_shared_function_infos(*new_noscript_list);

#ifdef VERIFY_HEAP
  share->SharedFunctionInfoVerify();
#endif
  return share;
}


static inline int NumberCacheHash(Handle<FixedArray> cache,
                                  Handle<Object> number) {
  int mask = (cache->length() >> 1) - 1;
  if (number->IsSmi()) {
    return Handle<Smi>::cast(number)->value() & mask;
  } else {
    int64_t bits = bit_cast<int64_t>(number->Number());
    return (static_cast<int>(bits) ^ static_cast<int>(bits >> 32)) & mask;
  }
}


Handle<Object> Factory::GetNumberStringCache(Handle<Object> number) {
  DisallowHeapAllocation no_gc;
  int hash = NumberCacheHash(number_string_cache(), number);
  Object* key = number_string_cache()->get(hash * 2);
  if (key == *number || (key->IsHeapNumber() && number->IsHeapNumber() &&
                         key->Number() == number->Number())) {
    return Handle<String>(
        String::cast(number_string_cache()->get(hash * 2 + 1)), isolate());
  }
  return undefined_value();
}


void Factory::SetNumberStringCache(Handle<Object> number,
                                   Handle<String> string) {
  int hash = NumberCacheHash(number_string_cache(), number);
  if (number_string_cache()->get(hash * 2) != *undefined_value()) {
    int full_size = isolate()->heap()->FullSizeNumberStringCacheLength();
    if (number_string_cache()->length() != full_size) {
      Handle<FixedArray> new_cache = NewFixedArray(full_size, TENURED);
      isolate()->heap()->set_number_string_cache(*new_cache);
      return;
    }
  }
  number_string_cache()->set(hash * 2, *number);
  number_string_cache()->set(hash * 2 + 1, *string);
}


Handle<String> Factory::NumberToString(Handle<Object> number,
                                       bool check_number_string_cache) {
  isolate()->counters()->number_to_string_runtime()->Increment();
  if (check_number_string_cache) {
    Handle<Object> cached = GetNumberStringCache(number);
    if (!cached->IsUndefined(isolate())) return Handle<String>::cast(cached);
  }

  char arr[100];
  Vector<char> buffer(arr, arraysize(arr));
  const char* str;
  if (number->IsSmi()) {
    int num = Handle<Smi>::cast(number)->value();
    str = IntToCString(num, buffer);
  } else {
    double num = Handle<HeapNumber>::cast(number)->value();
    str = DoubleToCString(num, buffer);
  }

  // We tenure the allocated string since it is referenced from the
  // number-string cache which lives in the old space.
  Handle<String> js_string = NewStringFromAsciiChecked(str, TENURED);
  SetNumberStringCache(number, js_string);
  return js_string;
}

Handle<DebugInfo> Factory::NewDebugInfo(Handle<SharedFunctionInfo> shared) {
  DCHECK(!shared->HasDebugInfo());
  Heap* heap = isolate()->heap();

  Handle<DebugInfo> debug_info =
      Handle<DebugInfo>::cast(NewStruct(DEBUG_INFO_TYPE, TENURED));
  debug_info->set_flags(DebugInfo::kNone);
  debug_info->set_shared(*shared);
  debug_info->set_debugger_hints(shared->debugger_hints());
  debug_info->set_debug_bytecode_array(heap->undefined_value());
  debug_info->set_break_points(heap->empty_fixed_array());

  // Link debug info to function.
  shared->set_debug_info(*debug_info);

  return debug_info;
}

Handle<CoverageInfo> Factory::NewCoverageInfo(
    const ZoneVector<SourceRange>& slots) {
  const int slot_count = static_cast<int>(slots.size());

  const int length = CoverageInfo::FixedArrayLengthForSlotCount(slot_count);
  Handle<CoverageInfo> info =
      Handle<CoverageInfo>::cast(NewUninitializedFixedArray(length));

  for (int i = 0; i < slot_count; i++) {
    SourceRange range = slots[i];
    info->InitializeSlot(i, range.start, range.end);
  }

  return info;
}

Handle<BreakPointInfo> Factory::NewBreakPointInfo(int source_position) {
  Handle<BreakPointInfo> new_break_point_info =
      Handle<BreakPointInfo>::cast(NewStruct(TUPLE2_TYPE, TENURED));
  new_break_point_info->set_source_position(source_position);
  new_break_point_info->set_break_point_objects(*undefined_value());
  return new_break_point_info;
}

Handle<BreakPoint> Factory::NewBreakPoint(int id, Handle<String> condition) {
  Handle<BreakPoint> new_break_point =
      Handle<BreakPoint>::cast(NewStruct(TUPLE2_TYPE, TENURED));
  new_break_point->set_id(id);
  new_break_point->set_condition(*condition);
  return new_break_point;
}

Handle<StackFrameInfo> Factory::NewStackFrameInfo() {
  Handle<StackFrameInfo> stack_frame_info = Handle<StackFrameInfo>::cast(
      NewStruct(STACK_FRAME_INFO_TYPE, NOT_TENURED));
  stack_frame_info->set_line_number(0);
  stack_frame_info->set_column_number(0);
  stack_frame_info->set_script_id(0);
  stack_frame_info->set_script_name(Smi::kZero);
  stack_frame_info->set_script_name_or_source_url(Smi::kZero);
  stack_frame_info->set_function_name(Smi::kZero);
  stack_frame_info->set_flag(0);
  return stack_frame_info;
}

Handle<SourcePositionTableWithFrameCache>
Factory::NewSourcePositionTableWithFrameCache(
    Handle<ByteArray> source_position_table,
    Handle<UnseededNumberDictionary> stack_frame_cache) {
  Handle<SourcePositionTableWithFrameCache>
      source_position_table_with_frame_cache =
          Handle<SourcePositionTableWithFrameCache>::cast(
              NewStruct(TUPLE2_TYPE, TENURED));
  source_position_table_with_frame_cache->set_source_position_table(
      *source_position_table);
  source_position_table_with_frame_cache->set_stack_frame_cache(
      *stack_frame_cache);
  return source_position_table_with_frame_cache;
}

Handle<JSObject> Factory::NewArgumentsObject(Handle<JSFunction> callee,
                                             int length) {
  bool strict_mode_callee = is_strict(callee->shared()->language_mode()) ||
                            !callee->shared()->has_simple_parameters();
  Handle<Map> map = strict_mode_callee ? isolate()->strict_arguments_map()
                                       : isolate()->sloppy_arguments_map();
  AllocationSiteUsageContext context(isolate(), Handle<AllocationSite>(),
                                     false);
  DCHECK(!isolate()->has_pending_exception());
  Handle<JSObject> result = NewJSObjectFromMap(map);
  Handle<Smi> value(Smi::FromInt(length), isolate());
  Object::SetProperty(result, length_string(), value, LanguageMode::kStrict)
      .Assert();
  if (!strict_mode_callee) {
    Object::SetProperty(result, callee_string(), callee, LanguageMode::kStrict)
        .Assert();
  }
  return result;
}


Handle<JSWeakMap> Factory::NewJSWeakMap() {
  // TODO(adamk): Currently the map is only created three times per
  // isolate. If it's created more often, the map should be moved into the
  // strong root list.
  Handle<Map> map = NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
  return Handle<JSWeakMap>::cast(NewJSObjectFromMap(map));
}

Handle<Map> Factory::ObjectLiteralMapFromCache(Handle<Context> native_context,
                                               int number_of_properties) {
  DCHECK(native_context->IsNativeContext());
  const int kMapCacheSize = 128;
  // We do not cache maps for too many properties or when running builtin code.
  if (isolate()->bootstrapper()->IsActive()) {
    return Map::Create(isolate(), number_of_properties);
  }
  // Use initial slow object proto map for too many properties.
  if (number_of_properties > kMapCacheSize) {
    return handle(native_context->slow_object_with_object_prototype_map(),
                  isolate());
  }
  if (number_of_properties == 0) {
    // Reuse the initial map of the Object function if the literal has no
    // predeclared properties.
    return handle(native_context->object_function()->initial_map(), isolate());
  }

  int cache_index = number_of_properties - 1;
  Handle<Object> maybe_cache(native_context->map_cache(), isolate());
  if (maybe_cache->IsUndefined(isolate())) {
    // Allocate the new map cache for the native context.
    maybe_cache = NewFixedArray(kMapCacheSize, TENURED);
    native_context->set_map_cache(*maybe_cache);
  } else {
    // Check to see whether there is a matching element in the cache.
    Handle<FixedArray> cache = Handle<FixedArray>::cast(maybe_cache);
    Object* result = cache->get(cache_index);
    if (result->IsWeakCell()) {
      WeakCell* cell = WeakCell::cast(result);
      if (!cell->cleared()) {
        Map* map = Map::cast(cell->value());
        DCHECK(!map->is_dictionary_map());
        return handle(map, isolate());
      }
    }
  }
  // Create a new map and add it to the cache.
  Handle<FixedArray> cache = Handle<FixedArray>::cast(maybe_cache);
  Handle<Map> map = Map::Create(isolate(), number_of_properties);
  DCHECK(!map->is_dictionary_map());
  Handle<WeakCell> cell = NewWeakCell(map);
  cache->set(cache_index, *cell);
  return map;
}


void Factory::SetRegExpAtomData(Handle<JSRegExp> regexp,
                                JSRegExp::Type type,
                                Handle<String> source,
                                JSRegExp::Flags flags,
                                Handle<Object> data) {
  Handle<FixedArray> store = NewFixedArray(JSRegExp::kAtomDataSize);

  store->set(JSRegExp::kTagIndex, Smi::FromInt(type));
  store->set(JSRegExp::kSourceIndex, *source);
  store->set(JSRegExp::kFlagsIndex, Smi::FromInt(flags));
  store->set(JSRegExp::kAtomPatternIndex, *data);
  regexp->set_data(*store);
}


void Factory::SetRegExpIrregexpData(Handle<JSRegExp> regexp,
                                    JSRegExp::Type type,
                                    Handle<String> source,
                                    JSRegExp::Flags flags,
                                    int capture_count) {
  Handle<FixedArray> store = NewFixedArray(JSRegExp::kIrregexpDataSize);
  Smi* uninitialized = Smi::FromInt(JSRegExp::kUninitializedValue);
  store->set(JSRegExp::kTagIndex, Smi::FromInt(type));
  store->set(JSRegExp::kSourceIndex, *source);
  store->set(JSRegExp::kFlagsIndex, Smi::FromInt(flags));
  store->set(JSRegExp::kIrregexpLatin1CodeIndex, uninitialized);
  store->set(JSRegExp::kIrregexpUC16CodeIndex, uninitialized);
  store->set(JSRegExp::kIrregexpMaxRegisterCountIndex, Smi::kZero);
  store->set(JSRegExp::kIrregexpCaptureCountIndex,
             Smi::FromInt(capture_count));
  store->set(JSRegExp::kIrregexpCaptureNameMapIndex, uninitialized);
  regexp->set_data(*store);
}

Handle<RegExpMatchInfo> Factory::NewRegExpMatchInfo() {
  // Initially, the last match info consists of all fixed fields plus space for
  // the match itself (i.e., 2 capture indices).
  static const int kInitialSize = RegExpMatchInfo::kFirstCaptureIndex +
                                  RegExpMatchInfo::kInitialCaptureIndices;

  Handle<FixedArray> elems = NewFixedArray(kInitialSize);
  Handle<RegExpMatchInfo> result = Handle<RegExpMatchInfo>::cast(elems);

  result->SetNumberOfCaptureRegisters(RegExpMatchInfo::kInitialCaptureIndices);
  result->SetLastSubject(*empty_string());
  result->SetLastInput(*undefined_value());
  result->SetCapture(0, 0);
  result->SetCapture(1, 0);

  return result;
}

Handle<Object> Factory::GlobalConstantFor(Handle<Name> name) {
  if (Name::Equals(name, undefined_string())) return undefined_value();
  if (Name::Equals(name, NaN_string())) return nan_value();
  if (Name::Equals(name, Infinity_string())) return infinity_value();
  return Handle<Object>::null();
}


Handle<Object> Factory::ToBoolean(bool value) {
  return value ? true_value() : false_value();
}

Handle<String> Factory::ToPrimitiveHintString(ToPrimitiveHint hint) {
  switch (hint) {
    case ToPrimitiveHint::kDefault:
      return default_string();
    case ToPrimitiveHint::kNumber:
      return number_string();
    case ToPrimitiveHint::kString:
      return string_string();
  }
  UNREACHABLE();
}

Handle<Map> Factory::CreateSloppyFunctionMap(
    FunctionMode function_mode, MaybeHandle<JSFunction> maybe_empty_function) {
  bool has_prototype = IsFunctionModeWithPrototype(function_mode);
  int header_size = has_prototype ? JSFunction::kSizeWithPrototype
                                  : JSFunction::kSizeWithoutPrototype;
  int descriptors_count = has_prototype ? 5 : 4;
  int inobject_properties_count = 0;
  if (IsFunctionModeWithName(function_mode)) ++inobject_properties_count;

  Handle<Map> map = NewMap(
      JS_FUNCTION_TYPE, header_size + inobject_properties_count * kPointerSize,
      TERMINAL_FAST_ELEMENTS_KIND, inobject_properties_count);
  map->set_has_prototype_slot(has_prototype);
  map->set_is_constructor(has_prototype);
  map->set_is_callable();
  Handle<JSFunction> empty_function;
  if (maybe_empty_function.ToHandle(&empty_function)) {
    Map::SetPrototype(map, empty_function);
  }

  //
  // Setup descriptors array.
  //
  Map::EnsureDescriptorSlack(map, descriptors_count);

  PropertyAttributes ro_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
  PropertyAttributes rw_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
  PropertyAttributes roc_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);

  int field_index = 0;
  STATIC_ASSERT(JSFunction::kLengthDescriptorIndex == 0);
  {  // Add length accessor.
    Descriptor d = Descriptor::AccessorConstant(
        length_string(), function_length_accessor(), roc_attribs);
    map->AppendDescriptor(&d);
  }

  STATIC_ASSERT(JSFunction::kNameDescriptorIndex == 1);
  if (IsFunctionModeWithName(function_mode)) {
    // Add name field.
    Handle<Name> name = isolate()->factory()->name_string();
    Descriptor d = Descriptor::DataField(name, field_index++, roc_attribs,
                                         Representation::Tagged());
    map->AppendDescriptor(&d);

  } else {
    // Add name accessor.
    Descriptor d = Descriptor::AccessorConstant(
        name_string(), function_name_accessor(), roc_attribs);
    map->AppendDescriptor(&d);
  }
  {  // Add arguments accessor.
    Descriptor d = Descriptor::AccessorConstant(
        arguments_string(), function_arguments_accessor(), ro_attribs);
    map->AppendDescriptor(&d);
  }
  {  // Add caller accessor.
    Descriptor d = Descriptor::AccessorConstant(
        caller_string(), function_caller_accessor(), ro_attribs);
    map->AppendDescriptor(&d);
  }
  if (IsFunctionModeWithPrototype(function_mode)) {
    // Add prototype accessor.
    PropertyAttributes attribs =
        IsFunctionModeWithWritablePrototype(function_mode) ? rw_attribs
                                                           : ro_attribs;
    Descriptor d = Descriptor::AccessorConstant(
        prototype_string(), function_prototype_accessor(), attribs);
    map->AppendDescriptor(&d);
  }
  DCHECK_EQ(inobject_properties_count, field_index);
  return map;
}

Handle<Map> Factory::CreateStrictFunctionMap(
    FunctionMode function_mode, Handle<JSFunction> empty_function) {
  bool has_prototype = IsFunctionModeWithPrototype(function_mode);
  int header_size = has_prototype ? JSFunction::kSizeWithPrototype
                                  : JSFunction::kSizeWithoutPrototype;
  int inobject_properties_count = 0;
  if (IsFunctionModeWithName(function_mode)) ++inobject_properties_count;
  if (IsFunctionModeWithHomeObject(function_mode)) ++inobject_properties_count;
  int descriptors_count = (IsFunctionModeWithPrototype(function_mode) ? 3 : 2) +
                          inobject_properties_count;

  Handle<Map> map = NewMap(
      JS_FUNCTION_TYPE, header_size + inobject_properties_count * kPointerSize,
      TERMINAL_FAST_ELEMENTS_KIND, inobject_properties_count);
  map->set_has_prototype_slot(has_prototype);
  map->set_is_constructor(has_prototype);
  map->set_is_callable();
  Map::SetPrototype(map, empty_function);

  //
  // Setup descriptors array.
  //
  Map::EnsureDescriptorSlack(map, descriptors_count);

  PropertyAttributes rw_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
  PropertyAttributes ro_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
  PropertyAttributes roc_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);

  int field_index = 0;
  STATIC_ASSERT(JSFunction::kLengthDescriptorIndex == 0);
  {  // Add length accessor.
    Descriptor d = Descriptor::AccessorConstant(
        length_string(), function_length_accessor(), roc_attribs);
    map->AppendDescriptor(&d);
  }

  STATIC_ASSERT(JSFunction::kNameDescriptorIndex == 1);
  if (IsFunctionModeWithName(function_mode)) {
    // Add name field.
    Handle<Name> name = isolate()->factory()->name_string();
    Descriptor d = Descriptor::DataField(name, field_index++, roc_attribs,
                                         Representation::Tagged());
    map->AppendDescriptor(&d);

  } else {
    // Add name accessor.
    Descriptor d = Descriptor::AccessorConstant(
        name_string(), function_name_accessor(), roc_attribs);
    map->AppendDescriptor(&d);
  }

  if (IsFunctionModeWithPrototype(function_mode)) {
    // Add prototype accessor.
    PropertyAttributes attribs =
        IsFunctionModeWithWritablePrototype(function_mode) ? rw_attribs
                                                           : ro_attribs;
    Descriptor d = Descriptor::AccessorConstant(
        prototype_string(), function_prototype_accessor(), attribs);
    map->AppendDescriptor(&d);
  }

  if (IsFunctionModeWithHomeObject(function_mode)) {
    // Add home object field.
    Handle<Name> name = isolate()->factory()->home_object_symbol();
    Descriptor d = Descriptor::DataField(name, field_index++, DONT_ENUM,
                                         Representation::Tagged());
    map->AppendDescriptor(&d);
  }
  DCHECK_EQ(inobject_properties_count, field_index);
  return map;
}

Handle<Map> Factory::CreateClassFunctionMap(Handle<JSFunction> empty_function) {
  Handle<Map> map = NewMap(JS_FUNCTION_TYPE, JSFunction::kSizeWithPrototype);
  map->set_has_prototype_slot(true);
  map->set_is_constructor(true);
  map->set_is_callable();
  Map::SetPrototype(map, empty_function);

  //
  // Setup descriptors array.
  //
  Map::EnsureDescriptorSlack(map, 2);

  PropertyAttributes rw_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
  PropertyAttributes roc_attribs =
      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);

  STATIC_ASSERT(JSFunction::kLengthDescriptorIndex == 0);
  {  // Add length accessor.
    Descriptor d = Descriptor::AccessorConstant(
        length_string(), function_length_accessor(), roc_attribs);
    map->AppendDescriptor(&d);
  }

  {
    // Add prototype accessor.
    Descriptor d = Descriptor::AccessorConstant(
        prototype_string(), function_prototype_accessor(), rw_attribs);
    map->AppendDescriptor(&d);
  }
  return map;
}

}  // namespace internal
}  // namespace v8