| // 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-object.h" |
| #include "src/base/bit-field.h" |
| #include "src/common/globals.h" |
| #include "src/flags/flags.h" |
| #include "src/utils/allocation.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. |
| }; |
| |
| V8_INLINE PropertyAttributes PropertyAttributesFromInt(int value) { |
| DCHECK_EQ(value & ~PropertyAttributes::ALL_ATTRIBUTES_MASK, 0); |
| return static_cast<PropertyAttributes>(value); |
| } |
| |
| // Number of distinct bits in PropertyAttributes. |
| static const int kPropertyAttributesBitsCount = 3; |
| |
| static const int kPropertyAttributesCombinationsCount = |
| 1 << kPropertyAttributesBitsCount; |
| |
| enum PropertyFilter { |
| ALL_PROPERTIES = 0, |
| ONLY_WRITABLE = 1, |
| ONLY_ENUMERABLE = 2, |
| ONLY_CONFIGURABLE = 4, |
| SKIP_STRINGS = 8, |
| SKIP_SYMBOLS = 16, |
| PRIVATE_NAMES_ONLY = 32, |
| 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) & 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)); |
| |
| // Assert that kPropertyAttributesBitsCount value matches the definition of |
| // ALL_ATTRIBUTES_MASK. |
| static_assert((ALL_ATTRIBUTES_MASK == (READ_ONLY | DONT_ENUM | DONT_DELETE)) == |
| (kPropertyAttributesBitsCount == 3)); |
| |
| class Smi; |
| class TypeInfo; |
| |
| // Order of kinds is significant. |
| // Must fit in the BitField PropertyDetails::KindField. |
| enum class PropertyKind { kData = 0, kAccessor = 1 }; |
| |
| // Order of modes is significant. |
| // Must fit in the BitField PropertyDetails::LocationField. |
| enum class 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, |
| // This representation is used for WasmObject fields and basically means |
| // that the actual field type information must be taken from the Wasm RTT |
| // associated with the map. |
| kWasmValue, |
| kNumRepresentations |
| }; |
| |
| constexpr Representation() : kind_(kNone) {} |
| |
| static constexpr Representation None() { return Representation(kNone); } |
| static constexpr Representation Tagged() { return Representation(kTagged); } |
| static constexpr Representation Smi() { return Representation(kSmi); } |
| static constexpr Representation Double() { return Representation(kDouble); } |
| static constexpr Representation HeapObject() { |
| return Representation(kHeapObject); |
| } |
| static constexpr Representation WasmValue() { |
| return Representation(kWasmValue); |
| } |
| |
| static constexpr 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); |
| } |
| |
| // Returns true if a change from this representation to a more general one |
| // might cause a map deprecation. |
| bool MightCauseMapDeprecation() const { |
| // HeapObject to tagged representation change can be done in-place. |
| // Boxed double to tagged transition is always done in-place. |
| // Note that WasmValue is not supposed to be changed at all (the only |
| // representation it fits into is WasmValue), so for the sake of predicate |
| // correctness we treat it as in-place "changeable". |
| if (IsTagged() || IsHeapObject() || IsDouble() || IsWasmValue()) { |
| return false; |
| } |
| // None to double and smi to double representation changes require |
| // deprecation, because doubles might require box allocation, see |
| // CanBeInPlaceChangedTo(). |
| DCHECK(IsNone() || IsSmi()); |
| return true; |
| } |
| |
| bool CanBeInPlaceChangedTo(const Representation& other) const { |
| if (Equals(other)) return true; |
| if (IsWasmValue() || other.IsWasmValue()) return false; |
| // 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 (!other.IsTagged()) return false; |
| DCHECK(IsSmi() || IsDouble() || IsHeapObject()); |
| return true; |
| } |
| |
| // Return the most generic representation that this representation can be |
| // changed to in-place. If an in-place representation change is not allowed, |
| // then this will return the current representation. |
| Representation MostGenericInPlaceChange() const { |
| if (IsWasmValue()) return Representation::WasmValue(); |
| return Representation::Tagged(); |
| } |
| |
| bool is_more_general_than(const Representation& other) const { |
| if (IsWasmValue()) return false; |
| 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; |
| } |
| |
| constexpr Kind kind() const { return static_cast<Kind>(kind_); } |
| constexpr bool IsNone() const { return kind_ == kNone; } |
| constexpr bool IsWasmValue() const { return kind_ == kWasmValue; } |
| constexpr bool IsTagged() const { return kind_ == kTagged; } |
| constexpr bool IsSmi() const { return kind_ == kSmi; } |
| constexpr bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); } |
| constexpr bool IsDouble() const { return kind_ == kDouble; } |
| constexpr 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"; |
| case kWasmValue: |
| return "w"; |
| } |
| UNREACHABLE(); |
| } |
| |
| bool operator==(const Representation& other) const { |
| return kind_ == other.kind_; |
| } |
| |
| private: |
| explicit constexpr 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; |
| |
| // A PropertyCell's property details contains a cell type that is meaningful if |
| // the cell is still valid (does not hold the hole). |
| enum class PropertyCellType { |
| kMutable, // Cell will no longer be tracked as constant. |
| kUndefined, // The PREMONOMORPHIC of property cells. |
| kConstant, // Cell has been assigned only once. |
| kConstantType, // Cell has been assigned only one type. |
| // Temporary value indicating an ongoing property cell state transition. Only |
| // observable by a background thread. |
| kInTransition, |
| // Value for dictionaries not holding cells, must be 0: |
| kNoCell = kMutable, |
| }; |
| |
| // PropertyDetails captures type and attributes for a property. |
| // They are used both in property dictionaries and instance descriptors. |
| class PropertyDetails { |
| public: |
| // Property details for global dictionary properties. |
| constexpr PropertyDetails(PropertyKind kind, PropertyAttributes attributes, |
| PropertyCellType cell_type, |
| int dictionary_index = 0) |
| : value_(KindField::encode(kind) | |
| LocationField::encode(PropertyLocation::kField) | |
| AttributesField::encode(attributes) | |
| // We track PropertyCell constness via PropertyCellTypeField, |
| // so we set ConstnessField to kMutable to simplify DCHECKs |
| // related to non-global property constness tracking. |
| ConstnessField::encode(PropertyConstness::kMutable) | |
| DictionaryStorageField::encode(dictionary_index) | |
| PropertyCellTypeField::encode(cell_type)) {} |
| |
| // Property details for dictionary mode properties/elements. |
| constexpr PropertyDetails(PropertyKind kind, PropertyAttributes attributes, |
| PropertyConstness constness, |
| int dictionary_index = 0) |
| : value_(KindField::encode(kind) | |
| LocationField::encode(PropertyLocation::kField) | |
| AttributesField::encode(attributes) | |
| ConstnessField::encode(constness) | |
| DictionaryStorageField::encode(dictionary_index) | |
| PropertyCellTypeField::encode(PropertyCellType::kNoCell)) {} |
| |
| // Property details for fast mode properties. |
| constexpr 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 constexpr PropertyDetails Empty( |
| PropertyCellType cell_type = PropertyCellType::kNoCell) { |
| return PropertyDetails(PropertyKind::kData, NONE, cell_type); |
| } |
| |
| bool operator==(PropertyDetails const& other) const { |
| return value_ == other.value_; |
| } |
| |
| bool operator!=(PropertyDetails const& other) const { |
| return value_ != other.value_; |
| } |
| |
| 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(Tagged<Smi> smi); |
| inline Tagged<Smi> AsSmi() const; |
| |
| static constexpr 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. |
| using KindField = base::BitField<PropertyKind, 0, 1>; |
| using ConstnessField = KindField::Next<PropertyConstness, 1>; |
| using AttributesField = ConstnessField::Next<PropertyAttributes, 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/dictionary mode objects. |
| using PropertyCellTypeField = AttributesField::Next<PropertyCellType, 3>; |
| using DictionaryStorageField = PropertyCellTypeField::Next<uint32_t, 23>; |
| |
| // Bit fields for fast objects. |
| using LocationField = AttributesField::Next<PropertyLocation, 1>; |
| using RepresentationField = LocationField::Next<uint32_t, 3>; |
| using DescriptorPointer = |
| RepresentationField::Next<uint32_t, kDescriptorIndexBitCount>; |
| using FieldIndexField = |
| DescriptorPointer::Next<uint32_t, kDescriptorIndexBitCount>; |
| |
| // All bits for both fast and slow objects must fit in a smi. |
| static_assert(DictionaryStorageField::kLastUsedBit < 31); |
| static_assert(FieldIndexField::kLastUsedBit < 31); |
| |
| // DictionaryStorageField must be the last field, so that overflowing it |
| // doesn't overwrite other fields. |
| static_assert(DictionaryStorageField::kLastUsedBit == 30); |
| |
| // All bits for non-global dictionary mode objects except enumeration index |
| // must fit in a byte. |
| static_assert(KindField::kLastUsedBit < 8); |
| static_assert(ConstnessField::kLastUsedBit < 8); |
| static_assert(AttributesField::kLastUsedBit < 8); |
| |
| static const int kInitialIndex = 1; |
| |
| static constexpr PropertyConstness kConstIfDictConstnessTracking = |
| V8_DICT_PROPERTY_CONST_TRACKING_BOOL ? PropertyConstness::kConst |
| : PropertyConstness::kMutable; |
| |
| #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, bool print_dict_index); |
| void PrintAsFastTo(std::ostream& out, PrintMode mode = kPrintFull); |
| |
| // Encodes those property details for non-global dictionary properties |
| // with an enumeration index of 0 as a single byte. |
| uint8_t ToByte() { |
| // We only care about the value of KindField, ConstnessField, and |
| // AttributesField. We've statically asserted earlier that these fields fit |
| // into a byte together. |
| |
| DCHECK_EQ(PropertyLocation::kField, location()); |
| static_assert(static_cast<int>(PropertyLocation::kField) == 0); |
| |
| DCHECK_EQ(PropertyCellType::kNoCell, cell_type()); |
| static_assert(static_cast<int>(PropertyCellType::kNoCell) == 0); |
| |
| // Only to be used when the enum index isn't actually maintained |
| // by the PropertyDetails: |
| DCHECK_EQ(0, dictionary_index()); |
| |
| return value_; |
| } |
| |
| // Only to be used for bytes obtained by ToByte. In particular, only used for |
| // non-global dictionary properties. |
| static PropertyDetails FromByte(uint8_t encoded_details) { |
| // The 0-extension to 32bit sets PropertyLocation to kField, |
| // PropertyCellType to kNoCell, and enumeration index to 0, as intended. |
| // Everything else is obtained from |encoded_details|. |
| PropertyDetails details(encoded_details); |
| DCHECK_EQ(PropertyLocation::kField, details.location()); |
| DCHECK_EQ(PropertyCellType::kNoCell, details.cell_type()); |
| DCHECK_EQ(0, details.dictionary_index()); |
| return details; |
| } |
| |
| 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); |
| } |
| |
| explicit PropertyDetails(uint32_t value) : value_{value} {} |
| |
| uint32_t value_; |
| }; |
| |
| // kField location is more general than kDescriptor, kDescriptor generalizes |
| // only to itself. |
| inline bool IsGeneralizableTo(PropertyLocation a, PropertyLocation b) { |
| return b == PropertyLocation::kField || a == PropertyLocation::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 Representation& representation); |
| V8_EXPORT_PRIVATE std::ostream& operator<<( |
| std::ostream& os, const PropertyAttributes& attributes); |
| V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& os, |
| PropertyConstness constness); |
| V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& os, |
| PropertyCellType type); |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_OBJECTS_PROPERTY_DETAILS_H_ |