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// Copyright 2012 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.
#ifndef V8_OBJECTS_PROPERTY_DETAILS_H_
#define V8_OBJECTS_PROPERTY_DETAILS_H_
#include "include/v8.h"
#include "src/utils/allocation.h"
// TODO(bmeurer): Remove once FLAG_modify_field_representation_inplace is gone.
#include "src/flags/flags.h"
#include "src/utils/utils.h"
namespace v8 {
namespace internal {
// ES6 6.1.7.1
enum PropertyAttributes {
NONE = ::v8::None,
READ_ONLY = ::v8::ReadOnly,
DONT_ENUM = ::v8::DontEnum,
DONT_DELETE = ::v8::DontDelete,
ALL_ATTRIBUTES_MASK = READ_ONLY | DONT_ENUM | DONT_DELETE,
SEALED = DONT_DELETE,
FROZEN = SEALED | READ_ONLY,
ABSENT = 64, // Used in runtime to indicate a property is absent.
// ABSENT can never be stored in or returned from a descriptor's attributes
// bitfield. It is only used as a return value meaning the attributes of
// a non-existent property.
};
enum PropertyFilter {
ALL_PROPERTIES = 0,
ONLY_WRITABLE = 1,
ONLY_ENUMERABLE = 2,
ONLY_CONFIGURABLE = 4,
SKIP_STRINGS = 8,
SKIP_SYMBOLS = 16,
ONLY_ALL_CAN_READ = 32,
PRIVATE_NAMES_ONLY = 64,
ENUMERABLE_STRINGS = ONLY_ENUMERABLE | SKIP_SYMBOLS,
};
// Enable fast comparisons of PropertyAttributes against PropertyFilters.
STATIC_ASSERT(ALL_PROPERTIES == static_cast<PropertyFilter>(NONE));
STATIC_ASSERT(ONLY_WRITABLE == static_cast<PropertyFilter>(READ_ONLY));
STATIC_ASSERT(ONLY_ENUMERABLE == static_cast<PropertyFilter>(DONT_ENUM));
STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(DONT_DELETE));
STATIC_ASSERT(((SKIP_STRINGS | SKIP_SYMBOLS | ONLY_ALL_CAN_READ) &
ALL_ATTRIBUTES_MASK) == 0);
STATIC_ASSERT(ALL_PROPERTIES ==
static_cast<PropertyFilter>(v8::PropertyFilter::ALL_PROPERTIES));
STATIC_ASSERT(ONLY_WRITABLE ==
static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_WRITABLE));
STATIC_ASSERT(ONLY_ENUMERABLE ==
static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_ENUMERABLE));
STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(
v8::PropertyFilter::ONLY_CONFIGURABLE));
STATIC_ASSERT(SKIP_STRINGS ==
static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_STRINGS));
STATIC_ASSERT(SKIP_SYMBOLS ==
static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_SYMBOLS));
class Smi;
class TypeInfo;
// Order of kinds is significant.
// Must fit in the BitField PropertyDetails::KindField.
enum PropertyKind { kData = 0, kAccessor = 1 };
// Order of modes is significant.
// Must fit in the BitField PropertyDetails::LocationField.
enum PropertyLocation { kField = 0, kDescriptor = 1 };
// Order of modes is significant.
// Must fit in the BitField PropertyDetails::ConstnessField.
enum class PropertyConstness { kMutable = 0, kConst = 1 };
class Representation {
public:
enum Kind { kNone, kSmi, kDouble, kHeapObject, kTagged, kNumRepresentations };
Representation() : kind_(kNone) {}
static Representation None() { return Representation(kNone); }
static Representation Tagged() { return Representation(kTagged); }
static Representation Smi() { return Representation(kSmi); }
static Representation Double() { return Representation(kDouble); }
static Representation HeapObject() { return Representation(kHeapObject); }
static Representation FromKind(Kind kind) { return Representation(kind); }
bool Equals(const Representation& other) const {
return kind_ == other.kind_;
}
bool IsCompatibleForLoad(const Representation& other) const {
return IsDouble() == other.IsDouble();
}
bool IsCompatibleForStore(const Representation& other) const {
return Equals(other);
}
bool CanBeInPlaceChangedTo(const Representation& other) const {
// If it's just a representation generalization case (i.e. property kind and
// attributes stays unchanged) it's fine to transition from None to anything
// but double without any modification to the object, because the default
// uninitialized value for representation None can be overwritten by both
// smi and tagged values. Doubles, however, would require a box allocation.
if (IsNone()) return !other.IsDouble();
if (!FLAG_modify_field_representation_inplace) return false;
return (IsSmi() || IsHeapObject()) && other.IsTagged();
}
bool is_more_general_than(const Representation& other) const {
if (IsHeapObject()) return other.IsNone();
return kind_ > other.kind_;
}
bool fits_into(const Representation& other) const {
return other.is_more_general_than(*this) || other.Equals(*this);
}
Representation generalize(Representation other) {
if (other.fits_into(*this)) return *this;
if (other.is_more_general_than(*this)) return other;
return Representation::Tagged();
}
int size() const {
DCHECK(!IsNone());
if (IsDouble()) return kDoubleSize;
DCHECK(IsTagged() || IsSmi() || IsHeapObject());
return kTaggedSize;
}
Kind kind() const { return static_cast<Kind>(kind_); }
bool IsNone() const { return kind_ == kNone; }
bool IsTagged() const { return kind_ == kTagged; }
bool IsSmi() const { return kind_ == kSmi; }
bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
bool IsDouble() const { return kind_ == kDouble; }
bool IsHeapObject() const { return kind_ == kHeapObject; }
const char* Mnemonic() const {
switch (kind_) {
case kNone:
return "v";
case kTagged:
return "t";
case kSmi:
return "s";
case kDouble:
return "d";
case kHeapObject:
return "h";
}
UNREACHABLE();
}
private:
explicit Representation(Kind k) : kind_(k) {}
// Make sure kind fits in int8.
STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
int8_t kind_;
};
static const int kDescriptorIndexBitCount = 10;
static const int kFirstInobjectPropertyOffsetBitCount = 7;
// The maximum number of descriptors we want in a descriptor array. It should
// fit in a page and also the following should hold:
// kMaxNumberOfDescriptors + kFieldsAdded <= PropertyArray::kMaxLength.
static const int kMaxNumberOfDescriptors = (1 << kDescriptorIndexBitCount) - 4;
static const int kInvalidEnumCacheSentinel =
(1 << kDescriptorIndexBitCount) - 1;
enum class PropertyCellType {
// Meaningful when a property cell does not contain the hole.
kUndefined, // The PREMONOMORPHIC of property cells.
kConstant, // Cell has been assigned only once.
kConstantType, // Cell has been assigned only one type.
kMutable, // Cell will no longer be tracked as constant.
// Meaningful when a property cell contains the hole.
kUninitialized = kUndefined, // Cell has never been initialized.
kInvalidated = kConstant, // Cell has been deleted, invalidated or never
// existed.
// For dictionaries not holding cells.
kNoCell = kMutable,
};
enum class PropertyCellConstantType {
kSmi,
kStableMap,
};
// PropertyDetails captures type and attributes for a property.
// They are used both in property dictionaries and instance descriptors.
class PropertyDetails {
public:
// Property details for dictionary mode properties/elements.
PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
PropertyCellType cell_type, int dictionary_index = 0) {
value_ = KindField::encode(kind) | LocationField::encode(kField) |
AttributesField::encode(attributes) |
DictionaryStorageField::encode(dictionary_index) |
PropertyCellTypeField::encode(cell_type);
}
// Property details for fast mode properties.
PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
PropertyLocation location, PropertyConstness constness,
Representation representation, int field_index = 0) {
value_ = KindField::encode(kind) | AttributesField::encode(attributes) |
LocationField::encode(location) |
ConstnessField::encode(constness) |
RepresentationField::encode(EncodeRepresentation(representation)) |
FieldIndexField::encode(field_index);
}
static PropertyDetails Empty(
PropertyCellType cell_type = PropertyCellType::kNoCell) {
return PropertyDetails(kData, NONE, cell_type);
}
int pointer() const { return DescriptorPointer::decode(value_); }
PropertyDetails set_pointer(int i) const {
return PropertyDetails(value_, i);
}
PropertyDetails set_cell_type(PropertyCellType type) const {
PropertyDetails details = *this;
details.value_ = PropertyCellTypeField::update(details.value_, type);
return details;
}
PropertyDetails set_index(int index) const {
PropertyDetails details = *this;
details.value_ = DictionaryStorageField::update(details.value_, index);
return details;
}
PropertyDetails CopyWithRepresentation(Representation representation) const {
return PropertyDetails(value_, representation);
}
PropertyDetails CopyWithConstness(PropertyConstness constness) const {
return PropertyDetails(value_, constness);
}
PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
new_attributes =
static_cast<PropertyAttributes>(attributes() | new_attributes);
return PropertyDetails(value_, new_attributes);
}
// Conversion for storing details as Object.
explicit inline PropertyDetails(Smi smi);
inline Smi AsSmi() const;
static uint8_t EncodeRepresentation(Representation representation) {
return representation.kind();
}
static Representation DecodeRepresentation(uint32_t bits) {
return Representation::FromKind(static_cast<Representation::Kind>(bits));
}
PropertyKind kind() const { return KindField::decode(value_); }
PropertyLocation location() const { return LocationField::decode(value_); }
PropertyConstness constness() const { return ConstnessField::decode(value_); }
PropertyAttributes attributes() const {
return AttributesField::decode(value_);
}
bool HasKindAndAttributes(PropertyKind kind, PropertyAttributes attributes) {
return (value_ & (KindField::kMask | AttributesField::kMask)) ==
(KindField::encode(kind) | AttributesField::encode(attributes));
}
int dictionary_index() const {
return DictionaryStorageField::decode(value_);
}
Representation representation() const {
return DecodeRepresentation(RepresentationField::decode(value_));
}
int field_index() const { return FieldIndexField::decode(value_); }
inline int field_width_in_words() const;
static bool IsValidIndex(int index) {
return DictionaryStorageField::is_valid(index);
}
bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
bool IsEnumerable() const { return !IsDontEnum(); }
PropertyCellType cell_type() const {
return PropertyCellTypeField::decode(value_);
}
// Bit fields in value_ (type, shift, size). Must be public so the
// constants can be embedded in generated code.
class KindField : public BitField<PropertyKind, 0, 1> {};
class LocationField : public BitField<PropertyLocation, KindField::kNext, 1> {
};
class ConstnessField
: public BitField<PropertyConstness, LocationField::kNext, 1> {};
class AttributesField
: public BitField<PropertyAttributes, ConstnessField::kNext, 3> {};
static const int kAttributesReadOnlyMask =
(READ_ONLY << AttributesField::kShift);
static const int kAttributesDontDeleteMask =
(DONT_DELETE << AttributesField::kShift);
static const int kAttributesDontEnumMask =
(DONT_ENUM << AttributesField::kShift);
// Bit fields for normalized objects.
class PropertyCellTypeField
: public BitField<PropertyCellType, AttributesField::kNext, 2> {};
class DictionaryStorageField
: public BitField<uint32_t, PropertyCellTypeField::kNext, 23> {};
// Bit fields for fast objects.
class RepresentationField
: public BitField<uint32_t, AttributesField::kNext, 3> {};
class DescriptorPointer
: public BitField<uint32_t, RepresentationField::kNext,
kDescriptorIndexBitCount> {}; // NOLINT
class FieldIndexField : public BitField<uint32_t, DescriptorPointer::kNext,
kDescriptorIndexBitCount> {
}; // NOLINT
// All bits for both fast and slow objects must fit in a smi.
STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
STATIC_ASSERT(FieldIndexField::kNext <= 31);
static const int kInitialIndex = 1;
#ifdef OBJECT_PRINT
// For our gdb macros, we should perhaps change these in the future.
void Print(bool dictionary_mode);
#endif
enum PrintMode {
kPrintAttributes = 1 << 0,
kPrintFieldIndex = 1 << 1,
kPrintRepresentation = 1 << 2,
kPrintPointer = 1 << 3,
kForProperties = kPrintFieldIndex,
kForTransitions = kPrintAttributes,
kPrintFull = -1,
};
void PrintAsSlowTo(std::ostream& out);
void PrintAsFastTo(std::ostream& out, PrintMode mode = kPrintFull);
private:
PropertyDetails(int value, int pointer) {
value_ = DescriptorPointer::update(value, pointer);
}
PropertyDetails(int value, Representation representation) {
value_ = RepresentationField::update(value,
EncodeRepresentation(representation));
}
PropertyDetails(int value, PropertyConstness constness) {
value_ = ConstnessField::update(value, constness);
}
PropertyDetails(int value, PropertyAttributes attributes) {
value_ = AttributesField::update(value, attributes);
}
uint32_t value_;
};
// kField location is more general than kDescriptor, kDescriptor generalizes
// only to itself.
inline bool IsGeneralizableTo(PropertyLocation a, PropertyLocation b) {
return b == kField || a == kDescriptor;
}
// PropertyConstness::kMutable constness is more general than
// VariableMode::kConst, VariableMode::kConst generalizes only to itself.
inline bool IsGeneralizableTo(PropertyConstness a, PropertyConstness b) {
return b == PropertyConstness::kMutable || a == PropertyConstness::kConst;
}
inline PropertyConstness GeneralizeConstness(PropertyConstness a,
PropertyConstness b) {
return a == PropertyConstness::kMutable ? PropertyConstness::kMutable : b;
}
V8_EXPORT_PRIVATE std::ostream& operator<<(
std::ostream& os, const PropertyAttributes& attributes);
} // namespace internal
} // namespace v8
#endif // V8_OBJECTS_PROPERTY_DETAILS_H_