heap.cc.svn-base

Google浏览器V8内核代码

Object* Heap::GetNumberStringCache(Object* number) {
  int hash;
  if (number->IsSmi()) {
    hash = smi_get_hash(Smi::cast(number));
  } else {
    hash = double_get_hash(number->Number());
  }
  Object* key = number_string_cache_->get(hash * 2);
  if (key == number) {
    return String::cast(number_string_cache_->get(hash * 2 + 1));
  } else if (key->IsHeapNumber() &&
             number->IsHeapNumber() &&
             key->Number() == number->Number()) {
    return String::cast(number_string_cache_->get(hash * 2 + 1));
  }
  return undefined_value();
}


void Heap::SetNumberStringCache(Object* number, String* string) {
  int hash;
  if (number->IsSmi()) {
    hash = smi_get_hash(Smi::cast(number));
    number_string_cache_->set(hash * 2, number, FixedArray::SKIP_WRITE_BARRIER);
  } else {
    hash = double_get_hash(number->Number());
    number_string_cache_->set(hash * 2, number);
  }
  number_string_cache_->set(hash * 2 + 1, string);
}


Object* Heap::SmiOrNumberFromDouble(double value,
                                    bool new_object,
                                    PretenureFlag pretenure) {
  // We need to distinguish the minus zero value and this cannot be
  // done after conversion to int. Doing this by comparing bit
  // patterns is faster than using fpclassify() et al.
  static const DoubleRepresentation plus_zero(0.0);
  static const DoubleRepresentation minus_zero(-0.0);
  static const DoubleRepresentation nan(OS::nan_value());
  ASSERT(minus_zero_value_ != NULL);
  ASSERT(sizeof(plus_zero.value) == sizeof(plus_zero.bits));

  DoubleRepresentation rep(value);
  if (rep.bits == plus_zero.bits) return Smi::FromInt(0);  // not uncommon
  if (rep.bits == minus_zero.bits) {
    return new_object ? AllocateHeapNumber(-0.0, pretenure)
                      : minus_zero_value_;
  }
  if (rep.bits == nan.bits) {
    return new_object
        ? AllocateHeapNumber(OS::nan_value(), pretenure)
        : nan_value_;
  }

  // Try to represent the value as a tagged small integer.
  int int_value = FastD2I(value);
  if (value == FastI2D(int_value) && Smi::IsValid(int_value)) {
    return Smi::FromInt(int_value);
  }

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


Object* Heap::NewNumberFromDouble(double value, PretenureFlag pretenure) {
  return SmiOrNumberFromDouble(value,
                               true /* number object must be new */,
                               pretenure);
}


Object* Heap::NumberFromDouble(double value, PretenureFlag pretenure) {
  return SmiOrNumberFromDouble(value,
                               false /* use preallocated NaN, -0.0 */,
                               pretenure);
}


Object* Heap::AllocateProxy(Address proxy, PretenureFlag pretenure) {
  // Statically ensure that it is safe to allocate proxies in paged spaces.
  STATIC_ASSERT(Proxy::kSize <= Page::kMaxHeapObjectSize);
  AllocationSpace space =
      (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
  Object* result = Allocate(proxy_map(), space);
  if (result->IsFailure()) return result;

  Proxy::cast(result)->set_proxy(proxy);
  return result;
}


Object* Heap::AllocateSharedFunctionInfo(Object* name) {
  Object* result = Allocate(shared_function_info_map(), NEW_SPACE);
  if (result->IsFailure()) return result;

  SharedFunctionInfo* share = SharedFunctionInfo::cast(result);
  share->set_name(name);
  Code* illegal = Builtins::builtin(Builtins::Illegal);
  share->set_code(illegal);
  share->set_expected_nof_properties(0);
  share->set_length(0);
  share->set_formal_parameter_count(0);
  share->set_instance_class_name(Object_symbol());
  share->set_function_data(undefined_value());
  share->set_lazy_load_data(undefined_value());
  share->set_script(undefined_value());
  share->set_start_position_and_type(0);
  share->set_debug_info(undefined_value());
  return result;
}


Object* Heap::AllocateConsString(String* first, String* second) {
  int length = first->length() + second->length();
  bool is_ascii = first->is_ascii() && second->is_ascii();

  // If the resulting string is small make a flat string.
  if (length < ConsString::kMinLength) {
    Object* result = is_ascii
        ? AllocateRawAsciiString(length)
        : AllocateRawTwoByteString(length);
    if (result->IsFailure()) return result;
    // Copy the characters into the new object.
    String* string_result = String::cast(result);
    int first_length = first->length();
    // Copy the content of the first string.
    for (int i = 0; i < first_length; i++) {
      string_result->Set(i, first->Get(i));
    }
    int second_length = second->length();
    // Copy the content of the first string.
    for (int i = 0; i < second_length; i++) {
      string_result->Set(first_length + i, second->Get(i));
    }
    return result;
  }

  Map* map;
  if (length <= String::kMaxShortStringSize) {
    map = is_ascii ? short_cons_ascii_string_map()
      : short_cons_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = is_ascii ? medium_cons_ascii_string_map()
      : medium_cons_string_map();
  } else {
    map = is_ascii ? long_cons_ascii_string_map()
      : long_cons_string_map();
  }

  Object* result = Allocate(map, NEW_SPACE);
  if (result->IsFailure()) return result;

  ConsString* cons_string = ConsString::cast(result);
  cons_string->set_first(first);
  cons_string->set_second(second);
  cons_string->set_length(length);

  return result;
}


Object* Heap::AllocateSlicedString(String* buffer, int start, int end) {
  int length = end - start;

  // If the resulting string is small make a sub string.
  if (end - start <= SlicedString::kMinLength) {
    return Heap::AllocateSubString(buffer, start, end);
  }

  Map* map;
  if (length <= String::kMaxShortStringSize) {
    map = buffer->is_ascii() ? short_sliced_ascii_string_map()
      : short_sliced_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = buffer->is_ascii() ? medium_sliced_ascii_string_map()
      : medium_sliced_string_map();
  } else {
    map = buffer->is_ascii() ? long_sliced_ascii_string_map()
      : long_sliced_string_map();
  }

  Object* result = Allocate(map, NEW_SPACE);
  if (result->IsFailure()) return result;

  SlicedString* sliced_string = SlicedString::cast(result);
  sliced_string->set_buffer(buffer);
  sliced_string->set_start(start);
  sliced_string->set_length(length);

  return result;
}


Object* Heap::AllocateSubString(String* buffer, int start, int end) {
  int length = end - start;

  // Make an attempt to flatten the buffer to reduce access time.
  buffer->TryFlatten();

  Object* result = buffer->is_ascii()
      ? AllocateRawAsciiString(length)
      : AllocateRawTwoByteString(length);
  if (result->IsFailure()) return result;

  // Copy the characters into the new object.
  String* string_result = String::cast(result);
  for (int i = 0; i < length; i++) {
    string_result->Set(i, buffer->Get(start + i));
  }
  return result;
}


Object* Heap::AllocateExternalStringFromAscii(
    ExternalAsciiString::Resource* resource) {
  Map* map;
  int length = resource->length();
  if (length <= String::kMaxShortStringSize) {
    map = short_external_ascii_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = medium_external_ascii_string_map();
  } else {
    map = long_external_ascii_string_map();
  }

  Object* result = Allocate(map, NEW_SPACE);
  if (result->IsFailure()) return result;

  ExternalAsciiString* external_string = ExternalAsciiString::cast(result);
  external_string->set_length(length);
  external_string->set_resource(resource);

  return result;
}


Object* Heap::AllocateExternalStringFromTwoByte(
    ExternalTwoByteString::Resource* resource) {
  Map* map;
  int length = resource->length();
  if (length <= String::kMaxShortStringSize) {
    map = short_external_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = medium_external_string_map();
  } else {
    map = long_external_string_map();
  }

  Object* result = Allocate(map, NEW_SPACE);
  if (result->IsFailure()) return result;

  ExternalTwoByteString* external_string = ExternalTwoByteString::cast(result);
  external_string->set_length(length);
  external_string->set_resource(resource);

  return result;
}


Object* Heap:: LookupSingleCharacterStringFromCode(uint16_t code) {
  if (code <= String::kMaxAsciiCharCode) {
    Object* value = Heap::single_character_string_cache()->get(code);
    if (value != Heap::undefined_value()) return value;
    Object* result = Heap::AllocateRawAsciiString(1);
    if (result->IsFailure()) return result;
    String::cast(result)->Set(0, code);
    Heap::single_character_string_cache()->set(code, result);
    return result;
  }
  Object* result = Heap::AllocateRawTwoByteString(1);
  if (result->IsFailure()) return result;
  String::cast(result)->Set(0, code);
  return result;
}


Object* Heap::AllocateByteArray(int length) {
  int size = ByteArray::SizeFor(length);
  AllocationSpace space =
      size > MaxHeapObjectSize() ? LO_SPACE : NEW_SPACE;

  Object* result = AllocateRaw(size, space);

  if (result->IsFailure()) return result;

  reinterpret_cast<Array*>(result)->set_map(byte_array_map());
  reinterpret_cast<Array*>(result)->set_length(length);
  return result;
}


Object* Heap::CreateCode(const CodeDesc& desc,
                         ScopeInfo<>* sinfo,
                         Code::Flags flags) {
  // Compute size
  int body_size = RoundUp(desc.instr_size + desc.reloc_size, kObjectAlignment);
  int sinfo_size = 0;
  if (sinfo != NULL) sinfo_size = sinfo->Serialize(NULL);
  int obj_size = Code::SizeFor(body_size, sinfo_size);
  Object* result;
  if (obj_size > MaxHeapObjectSize()) {
    result = lo_space_->AllocateRawCode(obj_size);
  } else {
    result = code_space_->AllocateRaw(obj_size);
  }

  if (result->IsFailure()) return result;

  // Initialize the object
  HeapObject::cast(result)->set_map(code_map());
  Code* code = Code::cast(result);
  code->set_instruction_size(desc.instr_size);
  code->set_relocation_size(desc.reloc_size);
  code->set_sinfo_size(sinfo_size);
  code->set_flags(flags);
  code->set_ic_flag(Code::IC_TARGET_IS_ADDRESS);
  code->CopyFrom(desc);  // migrate generated code
  if (sinfo != NULL) sinfo->Serialize(code);  // write scope info

#ifdef DEBUG
  code->Verify();
#endif
  return code;
}


Object* Heap::CopyCode(Code* code) {
  // Allocate an object the same size as the code object.
  int obj_size = code->Size();
  Object* result;
  if (obj_size > MaxHeapObjectSize()) {
    result = lo_space_->AllocateRawCode(obj_size);
  } else {
    result = code_space_->AllocateRaw(obj_size);
  }

  if (result->IsFailure()) return result;

  // Copy code object.
  Address old_addr = code->address();
  Address new_addr = reinterpret_cast<HeapObject*>(result)->address();
  memcpy(new_addr, old_addr, obj_size);

  // Relocate the copy.
  Code* new_code = Code::cast(result);
  new_code->Relocate(new_addr - old_addr);
  return new_code;
}


Object* Heap::Allocate(Map* map, AllocationSpace space) {
  ASSERT(gc_state_ == NOT_IN_GC);
  ASSERT(map->instance_type() != MAP_TYPE);
  Object* result = AllocateRaw(map->instance_size(), space);
  if (result->IsFailure()) return result;
  HeapObject::cast(result)->set_map(map);
  return result;
}


Object* Heap::InitializeFunction(JSFunction* function,
                                 SharedFunctionInfo* shared,
                                 Object* prototype) {
  ASSERT(!prototype->IsMap());
  function->initialize_properties();
  function->initialize_elements();
  function->set_shared(shared);
  function->set_prototype_or_initial_map(prototype);
  function->set_context(undefined_value());
  function->set_literals(empty_fixed_array());
  return function;
}


Object* Heap::AllocateFunctionPrototype(JSFunction* function) {
  // Allocate the prototype.
  Object* prototype =
      AllocateJSObject(Top::context()->global_context()->object_function());
  if (prototype->IsFailure()) return prototype;
  // When creating the prototype for the function we must set its
  // constructor to the function.
  Object* result =
      JSObject::cast(prototype)->SetProperty(constructor_symbol(),
                                             function,
                                             DONT_ENUM);
  if (result->IsFailure()) return result;
  return prototype;
}


Object* Heap::AllocateFunction(Map* function_map,
                               SharedFunctionInfo* shared,
                               Object* prototype) {
  Object* result = Allocate(function_map, OLD_POINTER_SPACE);
  if (result->IsFailure()) return result;
  return InitializeFunction(JSFunction::cast(result), shared, prototype);
}