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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 
     33 
     34 enum PropertyFilter {
     35   ALL_PROPERTIES = 0,
     36   ONLY_WRITABLE = 1,
     37   ONLY_ENUMERABLE = 2,
     38   ONLY_CONFIGURABLE = 4,
     39   SKIP_STRINGS = 8,
     40   SKIP_SYMBOLS = 16,
     41   ONLY_ALL_CAN_READ = 32,
     42   ENUMERABLE_STRINGS = ONLY_ENUMERABLE | SKIP_SYMBOLS,
     43 };
     44 // Enable fast comparisons of PropertyAttributes against PropertyFilters.
     45 STATIC_ASSERT(ALL_PROPERTIES == static_cast<PropertyFilter>(NONE));
     46 STATIC_ASSERT(ONLY_WRITABLE == static_cast<PropertyFilter>(READ_ONLY));
     47 STATIC_ASSERT(ONLY_ENUMERABLE == static_cast<PropertyFilter>(DONT_ENUM));
     48 STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(DONT_DELETE));
     49 STATIC_ASSERT(((SKIP_STRINGS | SKIP_SYMBOLS | ONLY_ALL_CAN_READ) &
     50                ALL_ATTRIBUTES_MASK) == 0);
     51 STATIC_ASSERT(ALL_PROPERTIES ==
     52               static_cast<PropertyFilter>(v8::PropertyFilter::ALL_PROPERTIES));
     53 STATIC_ASSERT(ONLY_WRITABLE ==
     54               static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_WRITABLE));
     55 STATIC_ASSERT(ONLY_ENUMERABLE ==
     56               static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_ENUMERABLE));
     57 STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(
     58                                        v8::PropertyFilter::ONLY_CONFIGURABLE));
     59 STATIC_ASSERT(SKIP_STRINGS ==
     60               static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_STRINGS));
     61 STATIC_ASSERT(SKIP_SYMBOLS ==
     62               static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_SYMBOLS));
     63 
     64 class Smi;
     65 class TypeInfo;
     66 
     67 // Type of properties.
     68 // Order of kinds is significant.
     69 // Must fit in the BitField PropertyDetails::KindField.
     70 enum PropertyKind { kData = 0, kAccessor = 1 };
     71 
     72 
     73 // Order of modes is significant.
     74 // Must fit in the BitField PropertyDetails::StoreModeField.
     75 enum PropertyLocation { kField = 0, kDescriptor = 1 };
     76 
     77 
     78 // Order of properties is significant.
     79 // Must fit in the BitField PropertyDetails::TypeField.
     80 // A copy of this is in debug/mirrors.js.
     81 enum PropertyType {
     82   DATA = (kField << 1) | kData,
     83   DATA_CONSTANT = (kDescriptor << 1) | kData,
     84   ACCESSOR = (kField << 1) | kAccessor,
     85   ACCESSOR_CONSTANT = (kDescriptor << 1) | kAccessor
     86 };
     87 
     88 
     89 class Representation {
     90  public:
     91   enum Kind {
     92     kNone,
     93     kInteger8,
     94     kUInteger8,
     95     kInteger16,
     96     kUInteger16,
     97     kSmi,
     98     kInteger32,
     99     kDouble,
    100     kHeapObject,
    101     kTagged,
    102     kExternal,
    103     kNumRepresentations
    104   };
    105 
    106   Representation() : kind_(kNone) { }
    107 
    108   static Representation None() { return Representation(kNone); }
    109   static Representation Tagged() { return Representation(kTagged); }
    110   static Representation Integer8() { return Representation(kInteger8); }
    111   static Representation UInteger8() { return Representation(kUInteger8); }
    112   static Representation Integer16() { return Representation(kInteger16); }
    113   static Representation UInteger16() { return Representation(kUInteger16); }
    114   static Representation Smi() { return Representation(kSmi); }
    115   static Representation Integer32() { return Representation(kInteger32); }
    116   static Representation Double() { return Representation(kDouble); }
    117   static Representation HeapObject() { return Representation(kHeapObject); }
    118   static Representation External() { return Representation(kExternal); }
    119 
    120   static Representation FromKind(Kind kind) { return Representation(kind); }
    121 
    122   bool Equals(const Representation& other) const {
    123     return kind_ == other.kind_;
    124   }
    125 
    126   bool IsCompatibleForLoad(const Representation& other) const {
    127     return (IsDouble() && other.IsDouble()) ||
    128         (!IsDouble() && !other.IsDouble());
    129   }
    130 
    131   bool IsCompatibleForStore(const Representation& other) const {
    132     return Equals(other);
    133   }
    134 
    135   bool is_more_general_than(const Representation& other) const {
    136     if (kind_ == kExternal && other.kind_ == kNone) return true;
    137     if (kind_ == kExternal && other.kind_ == kExternal) return false;
    138     if (kind_ == kNone && other.kind_ == kExternal) return false;
    139 
    140     DCHECK(kind_ != kExternal);
    141     DCHECK(other.kind_ != kExternal);
    142     if (IsHeapObject()) return other.IsNone();
    143     if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
    144     if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
    145     return kind_ > other.kind_;
    146   }
    147 
    148   bool fits_into(const Representation& other) const {
    149     return other.is_more_general_than(*this) || other.Equals(*this);
    150   }
    151 
    152   Representation generalize(Representation other) {
    153     if (other.fits_into(*this)) return *this;
    154     if (other.is_more_general_than(*this)) return other;
    155     return Representation::Tagged();
    156   }
    157 
    158   int size() const {
    159     DCHECK(!IsNone());
    160     if (IsInteger8() || IsUInteger8()) {
    161       return sizeof(uint8_t);
    162     }
    163     if (IsInteger16() || IsUInteger16()) {
    164       return sizeof(uint16_t);
    165     }
    166     if (IsInteger32()) {
    167       return sizeof(uint32_t);
    168     }
    169     return kPointerSize;
    170   }
    171 
    172   Kind kind() const { return static_cast<Kind>(kind_); }
    173   bool IsNone() const { return kind_ == kNone; }
    174   bool IsInteger8() const { return kind_ == kInteger8; }
    175   bool IsUInteger8() const { return kind_ == kUInteger8; }
    176   bool IsInteger16() const { return kind_ == kInteger16; }
    177   bool IsUInteger16() const { return kind_ == kUInteger16; }
    178   bool IsTagged() const { return kind_ == kTagged; }
    179   bool IsSmi() const { return kind_ == kSmi; }
    180   bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
    181   bool IsInteger32() const { return kind_ == kInteger32; }
    182   bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }
    183   bool IsDouble() const { return kind_ == kDouble; }
    184   bool IsHeapObject() const { return kind_ == kHeapObject; }
    185   bool IsExternal() const { return kind_ == kExternal; }
    186   bool IsSpecialization() const {
    187     return IsInteger8() || IsUInteger8() ||
    188       IsInteger16() || IsUInteger16() ||
    189       IsSmi() || IsInteger32() || IsDouble();
    190   }
    191   const char* Mnemonic() const;
    192 
    193  private:
    194   explicit Representation(Kind k) : kind_(k) { }
    195 
    196   // Make sure kind fits in int8.
    197   STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
    198 
    199   int8_t kind_;
    200 };
    201 
    202 
    203 static const int kDescriptorIndexBitCount = 10;
    204 // The maximum number of descriptors we want in a descriptor array (should
    205 // fit in a page).
    206 static const int kMaxNumberOfDescriptors =
    207     (1 << kDescriptorIndexBitCount) - 2;
    208 static const int kInvalidEnumCacheSentinel =
    209     (1 << kDescriptorIndexBitCount) - 1;
    210 
    211 enum class PropertyCellType {
    212   // Meaningful when a property cell does not contain the hole.
    213   kUndefined,     // The PREMONOMORPHIC of property cells.
    214   kConstant,      // Cell has been assigned only once.
    215   kConstantType,  // Cell has been assigned only one type.
    216   kMutable,       // Cell will no longer be tracked as constant.
    217 
    218   // Meaningful when a property cell contains the hole.
    219   kUninitialized = kUndefined,  // Cell has never been initialized.
    220   kInvalidated = kConstant,     // Cell has been deleted, invalidated or never
    221                                 // existed.
    222 
    223   // For dictionaries not holding cells.
    224   kNoCell = kMutable,
    225 };
    226 
    227 enum class PropertyCellConstantType {
    228   kSmi,
    229   kStableMap,
    230 };
    231 
    232 
    233 // PropertyDetails captures type and attributes for a property.
    234 // They are used both in property dictionaries and instance descriptors.
    235 class PropertyDetails BASE_EMBEDDED {
    236  public:
    237   PropertyDetails(PropertyAttributes attributes, PropertyType type, int index,
    238                   PropertyCellType cell_type) {
    239     value_ = TypeField::encode(type) | AttributesField::encode(attributes) |
    240              DictionaryStorageField::encode(index) |
    241              PropertyCellTypeField::encode(cell_type);
    242 
    243     DCHECK(type == this->type());
    244     DCHECK(attributes == this->attributes());
    245   }
    246 
    247   PropertyDetails(PropertyAttributes attributes,
    248                   PropertyType type,
    249                   Representation representation,
    250                   int field_index = 0) {
    251     value_ = TypeField::encode(type)
    252         | AttributesField::encode(attributes)
    253         | RepresentationField::encode(EncodeRepresentation(representation))
    254         | FieldIndexField::encode(field_index);
    255   }
    256 
    257   PropertyDetails(PropertyAttributes attributes, PropertyKind kind,
    258                   PropertyLocation location, Representation representation,
    259                   int field_index = 0) {
    260     value_ = KindField::encode(kind) | LocationField::encode(location) |
    261              AttributesField::encode(attributes) |
    262              RepresentationField::encode(EncodeRepresentation(representation)) |
    263              FieldIndexField::encode(field_index);
    264   }
    265 
    266   static PropertyDetails Empty(
    267       PropertyCellType cell_type = PropertyCellType::kNoCell) {
    268     return PropertyDetails(NONE, DATA, 0, cell_type);
    269   }
    270 
    271   int pointer() const { return DescriptorPointer::decode(value_); }
    272 
    273   PropertyDetails set_pointer(int i) const {
    274     return PropertyDetails(value_, i);
    275   }
    276 
    277   PropertyDetails set_cell_type(PropertyCellType type) const {
    278     PropertyDetails details = *this;
    279     details.value_ = PropertyCellTypeField::update(details.value_, type);
    280     return details;
    281   }
    282 
    283   PropertyDetails set_index(int index) const {
    284     PropertyDetails details = *this;
    285     details.value_ = DictionaryStorageField::update(details.value_, index);
    286     return details;
    287   }
    288 
    289   PropertyDetails CopyWithRepresentation(Representation representation) const {
    290     return PropertyDetails(value_, representation);
    291   }
    292   PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
    293     new_attributes =
    294         static_cast<PropertyAttributes>(attributes() | new_attributes);
    295     return PropertyDetails(value_, new_attributes);
    296   }
    297 
    298   // Conversion for storing details as Object*.
    299   explicit inline PropertyDetails(Smi* smi);
    300   inline Smi* AsSmi() const;
    301 
    302   static uint8_t EncodeRepresentation(Representation representation) {
    303     return representation.kind();
    304   }
    305 
    306   static Representation DecodeRepresentation(uint32_t bits) {
    307     return Representation::FromKind(static_cast<Representation::Kind>(bits));
    308   }
    309 
    310   PropertyKind kind() const { return KindField::decode(value_); }
    311   PropertyLocation location() const { return LocationField::decode(value_); }
    312 
    313   PropertyType type() const { return TypeField::decode(value_); }
    314 
    315   PropertyAttributes attributes() const {
    316     return AttributesField::decode(value_);
    317   }
    318 
    319   int dictionary_index() const {
    320     return DictionaryStorageField::decode(value_);
    321   }
    322 
    323   Representation representation() const {
    324     return DecodeRepresentation(RepresentationField::decode(value_));
    325   }
    326 
    327   int field_index() const { return FieldIndexField::decode(value_); }
    328 
    329   inline int field_width_in_words() const;
    330 
    331   static bool IsValidIndex(int index) {
    332     return DictionaryStorageField::is_valid(index);
    333   }
    334 
    335   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
    336   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
    337   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
    338   bool IsEnumerable() const { return !IsDontEnum(); }
    339   PropertyCellType cell_type() const {
    340     return PropertyCellTypeField::decode(value_);
    341   }
    342 
    343   // Bit fields in value_ (type, shift, size). Must be public so the
    344   // constants can be embedded in generated code.
    345   class KindField : public BitField<PropertyKind, 0, 1> {};
    346   class LocationField : public BitField<PropertyLocation, 1, 1> {};
    347   class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
    348   static const int kAttributesReadOnlyMask =
    349       (READ_ONLY << AttributesField::kShift);
    350 
    351   // Bit fields for normalized objects.
    352   class PropertyCellTypeField : public BitField<PropertyCellType, 5, 2> {};
    353   class DictionaryStorageField : public BitField<uint32_t, 7, 24> {};
    354 
    355   // Bit fields for fast objects.
    356   class RepresentationField : public BitField<uint32_t, 5, 4> {};
    357   class DescriptorPointer
    358       : public BitField<uint32_t, 9, kDescriptorIndexBitCount> {};  // NOLINT
    359   class FieldIndexField
    360       : public BitField<uint32_t, 9 + kDescriptorIndexBitCount,
    361                         kDescriptorIndexBitCount> {};  // NOLINT
    362 
    363   // NOTE: TypeField overlaps with KindField and LocationField.
    364   class TypeField : public BitField<PropertyType, 0, 2> {};
    365   STATIC_ASSERT(KindField::kNext == LocationField::kShift);
    366   STATIC_ASSERT(TypeField::kShift == KindField::kShift);
    367   STATIC_ASSERT(TypeField::kNext == LocationField::kNext);
    368 
    369   // All bits for both fast and slow objects must fit in a smi.
    370   STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
    371   STATIC_ASSERT(FieldIndexField::kNext <= 31);
    372 
    373   static const int kInitialIndex = 1;
    374 
    375 #ifdef OBJECT_PRINT
    376   // For our gdb macros, we should perhaps change these in the future.
    377   void Print(bool dictionary_mode);
    378 #endif
    379 
    380  private:
    381   PropertyDetails(int value, int pointer) {
    382     value_ = DescriptorPointer::update(value, pointer);
    383   }
    384   PropertyDetails(int value, Representation representation) {
    385     value_ = RepresentationField::update(
    386         value, EncodeRepresentation(representation));
    387   }
    388   PropertyDetails(int value, PropertyAttributes attributes) {
    389     value_ = AttributesField::update(value, attributes);
    390   }
    391 
    392   uint32_t value_;
    393 };
    394 
    395 
    396 std::ostream& operator<<(std::ostream& os,
    397                          const PropertyAttributes& attributes);
    398 std::ostream& operator<<(std::ostream& os, const PropertyDetails& details);
    399 }  // namespace internal
    400 }  // namespace v8
    401 
    402 #endif  // V8_PROPERTY_DETAILS_H_
    403