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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_PROPERTY_DETAILS_H_
      6 #define V8_PROPERTY_DETAILS_H_
      7 
      8 #include "include/v8.h"
      9 #include "src/allocation.h"
     10 #include "src/utils.h"
     11 
     12 namespace v8 {
     13 namespace internal {
     14 
     15 // ES6 6.1.7.1
     16 enum PropertyAttributes {
     17   NONE = ::v8::None,
     18   READ_ONLY = ::v8::ReadOnly,
     19   DONT_ENUM = ::v8::DontEnum,
     20   DONT_DELETE = ::v8::DontDelete,
     21 
     22   ALL_ATTRIBUTES_MASK = READ_ONLY | DONT_ENUM | DONT_DELETE,
     23 
     24   SEALED = DONT_DELETE,
     25   FROZEN = SEALED | READ_ONLY,
     26 
     27   ABSENT = 64,  // Used in runtime to indicate a property is absent.
     28   // ABSENT can never be stored in or returned from a descriptor's attributes
     29   // bitfield.  It is only used as a return value meaning the attributes of
     30   // a non-existent property.
     31 
     32   // When creating a property, EVAL_DECLARED used to indicate that the property
     33   // came from a sloppy-mode direct eval, and certain checks need to be done.
     34   // Cannot be stored in or returned from a descriptor's attributes bitfield.
     35   EVAL_DECLARED = 128
     36 };
     37 
     38 
     39 enum PropertyFilter {
     40   ALL_PROPERTIES = 0,
     41   ONLY_WRITABLE = 1,
     42   ONLY_ENUMERABLE = 2,
     43   ONLY_CONFIGURABLE = 4,
     44   SKIP_STRINGS = 8,
     45   SKIP_SYMBOLS = 16,
     46   ONLY_ALL_CAN_READ = 32,
     47   ENUMERABLE_STRINGS = ONLY_ENUMERABLE | SKIP_SYMBOLS,
     48 };
     49 // Enable fast comparisons of PropertyAttributes against PropertyFilters.
     50 STATIC_ASSERT(ALL_PROPERTIES == static_cast<PropertyFilter>(NONE));
     51 STATIC_ASSERT(ONLY_WRITABLE == static_cast<PropertyFilter>(READ_ONLY));
     52 STATIC_ASSERT(ONLY_ENUMERABLE == static_cast<PropertyFilter>(DONT_ENUM));
     53 STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(DONT_DELETE));
     54 STATIC_ASSERT(((SKIP_STRINGS | SKIP_SYMBOLS | ONLY_ALL_CAN_READ) &
     55                ALL_ATTRIBUTES_MASK) == 0);
     56 
     57 
     58 class Smi;
     59 template<class> class TypeImpl;
     60 struct ZoneTypeConfig;
     61 typedef TypeImpl<ZoneTypeConfig> Type;
     62 class TypeInfo;
     63 
     64 // Type of properties.
     65 // Order of kinds is significant.
     66 // Must fit in the BitField PropertyDetails::KindField.
     67 enum PropertyKind { kData = 0, kAccessor = 1 };
     68 
     69 
     70 // Order of modes is significant.
     71 // Must fit in the BitField PropertyDetails::StoreModeField.
     72 enum PropertyLocation { kField = 0, kDescriptor = 1 };
     73 
     74 
     75 // Order of properties is significant.
     76 // Must fit in the BitField PropertyDetails::TypeField.
     77 // A copy of this is in debug/mirrors.js.
     78 enum PropertyType {
     79   DATA = (kField << 1) | kData,
     80   DATA_CONSTANT = (kDescriptor << 1) | kData,
     81   ACCESSOR = (kField << 1) | kAccessor,
     82   ACCESSOR_CONSTANT = (kDescriptor << 1) | kAccessor
     83 };
     84 
     85 
     86 class Representation {
     87  public:
     88   enum Kind {
     89     kNone,
     90     kInteger8,
     91     kUInteger8,
     92     kInteger16,
     93     kUInteger16,
     94     kSmi,
     95     kInteger32,
     96     kDouble,
     97     kHeapObject,
     98     kTagged,
     99     kExternal,
    100     kNumRepresentations
    101   };
    102 
    103   Representation() : kind_(kNone) { }
    104 
    105   static Representation None() { return Representation(kNone); }
    106   static Representation Tagged() { return Representation(kTagged); }
    107   static Representation Integer8() { return Representation(kInteger8); }
    108   static Representation UInteger8() { return Representation(kUInteger8); }
    109   static Representation Integer16() { return Representation(kInteger16); }
    110   static Representation UInteger16() { return Representation(kUInteger16); }
    111   static Representation Smi() { return Representation(kSmi); }
    112   static Representation Integer32() { return Representation(kInteger32); }
    113   static Representation Double() { return Representation(kDouble); }
    114   static Representation HeapObject() { return Representation(kHeapObject); }
    115   static Representation External() { return Representation(kExternal); }
    116 
    117   static Representation FromKind(Kind kind) { return Representation(kind); }
    118 
    119   bool Equals(const Representation& other) const {
    120     return kind_ == other.kind_;
    121   }
    122 
    123   bool IsCompatibleForLoad(const Representation& other) const {
    124     return (IsDouble() && other.IsDouble()) ||
    125         (!IsDouble() && !other.IsDouble());
    126   }
    127 
    128   bool IsCompatibleForStore(const Representation& other) const {
    129     return Equals(other);
    130   }
    131 
    132   bool is_more_general_than(const Representation& other) const {
    133     if (kind_ == kExternal && other.kind_ == kNone) return true;
    134     if (kind_ == kExternal && other.kind_ == kExternal) return false;
    135     if (kind_ == kNone && other.kind_ == kExternal) return false;
    136 
    137     DCHECK(kind_ != kExternal);
    138     DCHECK(other.kind_ != kExternal);
    139     if (IsHeapObject()) return other.IsNone();
    140     if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
    141     if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
    142     return kind_ > other.kind_;
    143   }
    144 
    145   bool fits_into(const Representation& other) const {
    146     return other.is_more_general_than(*this) || other.Equals(*this);
    147   }
    148 
    149   Representation generalize(Representation other) {
    150     if (other.fits_into(*this)) return *this;
    151     if (other.is_more_general_than(*this)) return other;
    152     return Representation::Tagged();
    153   }
    154 
    155   int size() const {
    156     DCHECK(!IsNone());
    157     if (IsInteger8() || IsUInteger8()) {
    158       return sizeof(uint8_t);
    159     }
    160     if (IsInteger16() || IsUInteger16()) {
    161       return sizeof(uint16_t);
    162     }
    163     if (IsInteger32()) {
    164       return sizeof(uint32_t);
    165     }
    166     return kPointerSize;
    167   }
    168 
    169   Kind kind() const { return static_cast<Kind>(kind_); }
    170   bool IsNone() const { return kind_ == kNone; }
    171   bool IsInteger8() const { return kind_ == kInteger8; }
    172   bool IsUInteger8() const { return kind_ == kUInteger8; }
    173   bool IsInteger16() const { return kind_ == kInteger16; }
    174   bool IsUInteger16() const { return kind_ == kUInteger16; }
    175   bool IsTagged() const { return kind_ == kTagged; }
    176   bool IsSmi() const { return kind_ == kSmi; }
    177   bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
    178   bool IsInteger32() const { return kind_ == kInteger32; }
    179   bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }
    180   bool IsDouble() const { return kind_ == kDouble; }
    181   bool IsHeapObject() const { return kind_ == kHeapObject; }
    182   bool IsExternal() const { return kind_ == kExternal; }
    183   bool IsSpecialization() const {
    184     return IsInteger8() || IsUInteger8() ||
    185       IsInteger16() || IsUInteger16() ||
    186       IsSmi() || IsInteger32() || IsDouble();
    187   }
    188   const char* Mnemonic() const;
    189 
    190  private:
    191   explicit Representation(Kind k) : kind_(k) { }
    192 
    193   // Make sure kind fits in int8.
    194   STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
    195 
    196   int8_t kind_;
    197 };
    198 
    199 
    200 static const int kDescriptorIndexBitCount = 10;
    201 // The maximum number of descriptors we want in a descriptor array (should
    202 // fit in a page).
    203 static const int kMaxNumberOfDescriptors =
    204     (1 << kDescriptorIndexBitCount) - 2;
    205 static const int kInvalidEnumCacheSentinel =
    206     (1 << kDescriptorIndexBitCount) - 1;
    207 
    208 
    209 enum class PropertyCellType {
    210   // Meaningful when a property cell does not contain the hole.
    211   kUndefined,     // The PREMONOMORPHIC of property cells.
    212   kConstant,      // Cell has been assigned only once.
    213   kConstantType,  // Cell has been assigned only one type.
    214   kMutable,       // Cell will no longer be tracked as constant.
    215 
    216   // Meaningful when a property cell contains the hole.
    217   kUninitialized = kUndefined,  // Cell has never been initialized.
    218   kInvalidated = kConstant,     // Cell has been deleted or invalidated.
    219 
    220   // For dictionaries not holding cells.
    221   kNoCell = kMutable,
    222 };
    223 
    224 
    225 enum class PropertyCellConstantType {
    226   kSmi,
    227   kStableMap,
    228 };
    229 
    230 
    231 // PropertyDetails captures type and attributes for a property.
    232 // They are used both in property dictionaries and instance descriptors.
    233 class PropertyDetails BASE_EMBEDDED {
    234  public:
    235   PropertyDetails(PropertyAttributes attributes, PropertyType type, int index,
    236                   PropertyCellType cell_type) {
    237     value_ = TypeField::encode(type) | AttributesField::encode(attributes) |
    238              DictionaryStorageField::encode(index) |
    239              PropertyCellTypeField::encode(cell_type);
    240 
    241     DCHECK(type == this->type());
    242     DCHECK(attributes == this->attributes());
    243   }
    244 
    245   PropertyDetails(PropertyAttributes attributes,
    246                   PropertyType type,
    247                   Representation representation,
    248                   int field_index = 0) {
    249     value_ = TypeField::encode(type)
    250         | AttributesField::encode(attributes)
    251         | RepresentationField::encode(EncodeRepresentation(representation))
    252         | FieldIndexField::encode(field_index);
    253   }
    254 
    255   PropertyDetails(PropertyAttributes attributes, PropertyKind kind,
    256                   PropertyLocation location, Representation representation,
    257                   int field_index = 0) {
    258     value_ = KindField::encode(kind) | LocationField::encode(location) |
    259              AttributesField::encode(attributes) |
    260              RepresentationField::encode(EncodeRepresentation(representation)) |
    261              FieldIndexField::encode(field_index);
    262   }
    263 
    264   static PropertyDetails Empty() {
    265     return PropertyDetails(NONE, DATA, 0, PropertyCellType::kNoCell);
    266   }
    267 
    268   int pointer() const { return DescriptorPointer::decode(value_); }
    269 
    270   PropertyDetails set_pointer(int i) const {
    271     return PropertyDetails(value_, i);
    272   }
    273 
    274   PropertyDetails set_cell_type(PropertyCellType type) const {
    275     PropertyDetails details = *this;
    276     details.value_ = PropertyCellTypeField::update(details.value_, type);
    277     return details;
    278   }
    279 
    280   PropertyDetails set_index(int index) const {
    281     PropertyDetails details = *this;
    282     details.value_ = DictionaryStorageField::update(details.value_, index);
    283     return details;
    284   }
    285 
    286   PropertyDetails CopyWithRepresentation(Representation representation) const {
    287     return PropertyDetails(value_, representation);
    288   }
    289   PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
    290     new_attributes =
    291         static_cast<PropertyAttributes>(attributes() | new_attributes);
    292     return PropertyDetails(value_, new_attributes);
    293   }
    294 
    295   // Conversion for storing details as Object*.
    296   explicit inline PropertyDetails(Smi* smi);
    297   inline Smi* AsSmi() const;
    298 
    299   static uint8_t EncodeRepresentation(Representation representation) {
    300     return representation.kind();
    301   }
    302 
    303   static Representation DecodeRepresentation(uint32_t bits) {
    304     return Representation::FromKind(static_cast<Representation::Kind>(bits));
    305   }
    306 
    307   PropertyKind kind() const { return KindField::decode(value_); }
    308   PropertyLocation location() const { return LocationField::decode(value_); }
    309 
    310   PropertyType type() const { return TypeField::decode(value_); }
    311 
    312   PropertyAttributes attributes() const {
    313     return AttributesField::decode(value_);
    314   }
    315 
    316   int dictionary_index() const {
    317     return DictionaryStorageField::decode(value_);
    318   }
    319 
    320   Representation representation() const {
    321     return DecodeRepresentation(RepresentationField::decode(value_));
    322   }
    323 
    324   int field_index() const { return FieldIndexField::decode(value_); }
    325 
    326   inline int field_width_in_words() const;
    327 
    328   static bool IsValidIndex(int index) {
    329     return DictionaryStorageField::is_valid(index);
    330   }
    331 
    332   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
    333   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
    334   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
    335   PropertyCellType cell_type() const {
    336     return PropertyCellTypeField::decode(value_);
    337   }
    338 
    339   // Bit fields in value_ (type, shift, size). Must be public so the
    340   // constants can be embedded in generated code.
    341   class KindField : public BitField<PropertyKind, 0, 1> {};
    342   class LocationField : public BitField<PropertyLocation, 1, 1> {};
    343   class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
    344   static const int kAttributesReadOnlyMask =
    345       (READ_ONLY << AttributesField::kShift);
    346 
    347   // Bit fields for normalized objects.
    348   class PropertyCellTypeField : public BitField<PropertyCellType, 5, 2> {};
    349   class DictionaryStorageField : public BitField<uint32_t, 7, 24> {};
    350 
    351   // Bit fields for fast objects.
    352   class RepresentationField : public BitField<uint32_t, 5, 4> {};
    353   class DescriptorPointer
    354       : public BitField<uint32_t, 9, kDescriptorIndexBitCount> {};  // NOLINT
    355   class FieldIndexField
    356       : public BitField<uint32_t, 9 + kDescriptorIndexBitCount,
    357                         kDescriptorIndexBitCount> {};  // NOLINT
    358 
    359   // NOTE: TypeField overlaps with KindField and LocationField.
    360   class TypeField : public BitField<PropertyType, 0, 2> {};
    361   STATIC_ASSERT(KindField::kNext == LocationField::kShift);
    362   STATIC_ASSERT(TypeField::kShift == KindField::kShift);
    363   STATIC_ASSERT(TypeField::kNext == LocationField::kNext);
    364 
    365   // All bits for both fast and slow objects must fit in a smi.
    366   STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
    367   STATIC_ASSERT(FieldIndexField::kNext <= 31);
    368 
    369   static const int kInitialIndex = 1;
    370 
    371 #ifdef OBJECT_PRINT
    372   // For our gdb macros, we should perhaps change these in the future.
    373   void Print(bool dictionary_mode);
    374 #endif
    375 
    376  private:
    377   PropertyDetails(int value, int pointer) {
    378     value_ = DescriptorPointer::update(value, pointer);
    379   }
    380   PropertyDetails(int value, Representation representation) {
    381     value_ = RepresentationField::update(
    382         value, EncodeRepresentation(representation));
    383   }
    384   PropertyDetails(int value, PropertyAttributes attributes) {
    385     value_ = AttributesField::update(value, attributes);
    386   }
    387 
    388   uint32_t value_;
    389 };
    390 
    391 
    392 std::ostream& operator<<(std::ostream& os,
    393                          const PropertyAttributes& attributes);
    394 std::ostream& operator<<(std::ostream& os, const PropertyDetails& details);
    395 }  // namespace internal
    396 }  // namespace v8
    397 
    398 #endif  // V8_PROPERTY_DETAILS_H_
    399