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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 Type;
66 class TypeInfo;
67 
68 // Type of properties.
69 // Order of kinds is significant.
70 // Must fit in the BitField PropertyDetails::KindField.
71 enum PropertyKind { kData = 0, kAccessor = 1 };
72 
73 
74 // Order of modes is significant.
75 // Must fit in the BitField PropertyDetails::StoreModeField.
76 enum PropertyLocation { kField = 0, kDescriptor = 1 };
77 
78 
79 // Order of properties is significant.
80 // Must fit in the BitField PropertyDetails::TypeField.
81 // A copy of this is in debug/mirrors.js.
82 enum PropertyType {
83   DATA = (kField << 1) | kData,
84   DATA_CONSTANT = (kDescriptor << 1) | kData,
85   ACCESSOR = (kField << 1) | kAccessor,
86   ACCESSOR_CONSTANT = (kDescriptor << 1) | kAccessor
87 };
88 
89 
90 class Representation {
91  public:
92   enum Kind {
93     kNone,
94     kInteger8,
95     kUInteger8,
96     kInteger16,
97     kUInteger16,
98     kSmi,
99     kInteger32,
100     kDouble,
101     kHeapObject,
102     kTagged,
103     kExternal,
104     kNumRepresentations
105   };
106 
Representation()107   Representation() : kind_(kNone) { }
108 
None()109   static Representation None() { return Representation(kNone); }
Tagged()110   static Representation Tagged() { return Representation(kTagged); }
Integer8()111   static Representation Integer8() { return Representation(kInteger8); }
UInteger8()112   static Representation UInteger8() { return Representation(kUInteger8); }
Integer16()113   static Representation Integer16() { return Representation(kInteger16); }
UInteger16()114   static Representation UInteger16() { return Representation(kUInteger16); }
Smi()115   static Representation Smi() { return Representation(kSmi); }
Integer32()116   static Representation Integer32() { return Representation(kInteger32); }
Double()117   static Representation Double() { return Representation(kDouble); }
HeapObject()118   static Representation HeapObject() { return Representation(kHeapObject); }
External()119   static Representation External() { return Representation(kExternal); }
120 
FromKind(Kind kind)121   static Representation FromKind(Kind kind) { return Representation(kind); }
122 
Equals(const Representation & other)123   bool Equals(const Representation& other) const {
124     return kind_ == other.kind_;
125   }
126 
IsCompatibleForLoad(const Representation & other)127   bool IsCompatibleForLoad(const Representation& other) const {
128     return (IsDouble() && other.IsDouble()) ||
129         (!IsDouble() && !other.IsDouble());
130   }
131 
IsCompatibleForStore(const Representation & other)132   bool IsCompatibleForStore(const Representation& other) const {
133     return Equals(other);
134   }
135 
is_more_general_than(const Representation & other)136   bool is_more_general_than(const Representation& other) const {
137     if (kind_ == kExternal && other.kind_ == kNone) return true;
138     if (kind_ == kExternal && other.kind_ == kExternal) return false;
139     if (kind_ == kNone && other.kind_ == kExternal) return false;
140 
141     DCHECK(kind_ != kExternal);
142     DCHECK(other.kind_ != kExternal);
143     if (IsHeapObject()) return other.IsNone();
144     if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
145     if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
146     return kind_ > other.kind_;
147   }
148 
fits_into(const Representation & other)149   bool fits_into(const Representation& other) const {
150     return other.is_more_general_than(*this) || other.Equals(*this);
151   }
152 
generalize(Representation other)153   Representation generalize(Representation other) {
154     if (other.fits_into(*this)) return *this;
155     if (other.is_more_general_than(*this)) return other;
156     return Representation::Tagged();
157   }
158 
size()159   int size() const {
160     DCHECK(!IsNone());
161     if (IsInteger8() || IsUInteger8()) {
162       return sizeof(uint8_t);
163     }
164     if (IsInteger16() || IsUInteger16()) {
165       return sizeof(uint16_t);
166     }
167     if (IsInteger32()) {
168       return sizeof(uint32_t);
169     }
170     return kPointerSize;
171   }
172 
kind()173   Kind kind() const { return static_cast<Kind>(kind_); }
IsNone()174   bool IsNone() const { return kind_ == kNone; }
IsInteger8()175   bool IsInteger8() const { return kind_ == kInteger8; }
IsUInteger8()176   bool IsUInteger8() const { return kind_ == kUInteger8; }
IsInteger16()177   bool IsInteger16() const { return kind_ == kInteger16; }
IsUInteger16()178   bool IsUInteger16() const { return kind_ == kUInteger16; }
IsTagged()179   bool IsTagged() const { return kind_ == kTagged; }
IsSmi()180   bool IsSmi() const { return kind_ == kSmi; }
IsSmiOrTagged()181   bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
IsInteger32()182   bool IsInteger32() const { return kind_ == kInteger32; }
IsSmiOrInteger32()183   bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }
IsDouble()184   bool IsDouble() const { return kind_ == kDouble; }
IsHeapObject()185   bool IsHeapObject() const { return kind_ == kHeapObject; }
IsExternal()186   bool IsExternal() const { return kind_ == kExternal; }
IsSpecialization()187   bool IsSpecialization() const {
188     return IsInteger8() || IsUInteger8() ||
189       IsInteger16() || IsUInteger16() ||
190       IsSmi() || IsInteger32() || IsDouble();
191   }
192   const char* Mnemonic() const;
193 
194  private:
Representation(Kind k)195   explicit Representation(Kind k) : kind_(k) { }
196 
197   // Make sure kind fits in int8.
198   STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
199 
200   int8_t kind_;
201 };
202 
203 
204 static const int kDescriptorIndexBitCount = 10;
205 // The maximum number of descriptors we want in a descriptor array (should
206 // fit in a page).
207 static const int kMaxNumberOfDescriptors =
208     (1 << kDescriptorIndexBitCount) - 2;
209 static const int kInvalidEnumCacheSentinel =
210     (1 << kDescriptorIndexBitCount) - 1;
211 
212 
213 enum class PropertyCellType {
214   // Meaningful when a property cell does not contain the hole.
215   kUndefined,     // The PREMONOMORPHIC of property cells.
216   kConstant,      // Cell has been assigned only once.
217   kConstantType,  // Cell has been assigned only one type.
218   kMutable,       // Cell will no longer be tracked as constant.
219 
220   // Meaningful when a property cell contains the hole.
221   kUninitialized = kUndefined,  // Cell has never been initialized.
222   kInvalidated = kConstant,     // Cell has been deleted or invalidated.
223 
224   // For dictionaries not holding cells.
225   kNoCell = kMutable,
226 };
227 
228 
229 enum class PropertyCellConstantType {
230   kSmi,
231   kStableMap,
232 };
233 
234 
235 // PropertyDetails captures type and attributes for a property.
236 // They are used both in property dictionaries and instance descriptors.
237 class PropertyDetails BASE_EMBEDDED {
238  public:
PropertyDetails(PropertyAttributes attributes,PropertyType type,int index,PropertyCellType cell_type)239   PropertyDetails(PropertyAttributes attributes, PropertyType type, int index,
240                   PropertyCellType cell_type) {
241     value_ = TypeField::encode(type) | AttributesField::encode(attributes) |
242              DictionaryStorageField::encode(index) |
243              PropertyCellTypeField::encode(cell_type);
244 
245     DCHECK(type == this->type());
246     DCHECK(attributes == this->attributes());
247   }
248 
249   PropertyDetails(PropertyAttributes attributes,
250                   PropertyType type,
251                   Representation representation,
252                   int field_index = 0) {
253     value_ = TypeField::encode(type)
254         | AttributesField::encode(attributes)
255         | RepresentationField::encode(EncodeRepresentation(representation))
256         | FieldIndexField::encode(field_index);
257   }
258 
259   PropertyDetails(PropertyAttributes attributes, PropertyKind kind,
260                   PropertyLocation location, Representation representation,
261                   int field_index = 0) {
262     value_ = KindField::encode(kind) | LocationField::encode(location) |
263              AttributesField::encode(attributes) |
264              RepresentationField::encode(EncodeRepresentation(representation)) |
265              FieldIndexField::encode(field_index);
266   }
267 
Empty()268   static PropertyDetails Empty() {
269     return PropertyDetails(NONE, DATA, 0, PropertyCellType::kNoCell);
270   }
271 
pointer()272   int pointer() const { return DescriptorPointer::decode(value_); }
273 
set_pointer(int i)274   PropertyDetails set_pointer(int i) const {
275     return PropertyDetails(value_, i);
276   }
277 
set_cell_type(PropertyCellType type)278   PropertyDetails set_cell_type(PropertyCellType type) const {
279     PropertyDetails details = *this;
280     details.value_ = PropertyCellTypeField::update(details.value_, type);
281     return details;
282   }
283 
set_index(int index)284   PropertyDetails set_index(int index) const {
285     PropertyDetails details = *this;
286     details.value_ = DictionaryStorageField::update(details.value_, index);
287     return details;
288   }
289 
CopyWithRepresentation(Representation representation)290   PropertyDetails CopyWithRepresentation(Representation representation) const {
291     return PropertyDetails(value_, representation);
292   }
CopyAddAttributes(PropertyAttributes new_attributes)293   PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
294     new_attributes =
295         static_cast<PropertyAttributes>(attributes() | new_attributes);
296     return PropertyDetails(value_, new_attributes);
297   }
298 
299   // Conversion for storing details as Object*.
300   explicit inline PropertyDetails(Smi* smi);
301   inline Smi* AsSmi() const;
302 
EncodeRepresentation(Representation representation)303   static uint8_t EncodeRepresentation(Representation representation) {
304     return representation.kind();
305   }
306 
DecodeRepresentation(uint32_t bits)307   static Representation DecodeRepresentation(uint32_t bits) {
308     return Representation::FromKind(static_cast<Representation::Kind>(bits));
309   }
310 
kind()311   PropertyKind kind() const { return KindField::decode(value_); }
location()312   PropertyLocation location() const { return LocationField::decode(value_); }
313 
type()314   PropertyType type() const { return TypeField::decode(value_); }
315 
attributes()316   PropertyAttributes attributes() const {
317     return AttributesField::decode(value_);
318   }
319 
dictionary_index()320   int dictionary_index() const {
321     return DictionaryStorageField::decode(value_);
322   }
323 
representation()324   Representation representation() const {
325     return DecodeRepresentation(RepresentationField::decode(value_));
326   }
327 
field_index()328   int field_index() const { return FieldIndexField::decode(value_); }
329 
330   inline int field_width_in_words() const;
331 
IsValidIndex(int index)332   static bool IsValidIndex(int index) {
333     return DictionaryStorageField::is_valid(index);
334   }
335 
IsReadOnly()336   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
IsConfigurable()337   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
IsDontEnum()338   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
IsEnumerable()339   bool IsEnumerable() const { return !IsDontEnum(); }
cell_type()340   PropertyCellType cell_type() const {
341     return PropertyCellTypeField::decode(value_);
342   }
343 
344   // Bit fields in value_ (type, shift, size). Must be public so the
345   // constants can be embedded in generated code.
346   class KindField : public BitField<PropertyKind, 0, 1> {};
347   class LocationField : public BitField<PropertyLocation, 1, 1> {};
348   class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
349   static const int kAttributesReadOnlyMask =
350       (READ_ONLY << AttributesField::kShift);
351 
352   // Bit fields for normalized objects.
353   class PropertyCellTypeField : public BitField<PropertyCellType, 5, 2> {};
354   class DictionaryStorageField : public BitField<uint32_t, 7, 24> {};
355 
356   // Bit fields for fast objects.
357   class RepresentationField : public BitField<uint32_t, 5, 4> {};
358   class DescriptorPointer
359       : public BitField<uint32_t, 9, kDescriptorIndexBitCount> {};  // NOLINT
360   class FieldIndexField
361       : public BitField<uint32_t, 9 + kDescriptorIndexBitCount,
362                         kDescriptorIndexBitCount> {};  // NOLINT
363 
364   // NOTE: TypeField overlaps with KindField and LocationField.
365   class TypeField : public BitField<PropertyType, 0, 2> {};
366   STATIC_ASSERT(KindField::kNext == LocationField::kShift);
367   STATIC_ASSERT(TypeField::kShift == KindField::kShift);
368   STATIC_ASSERT(TypeField::kNext == LocationField::kNext);
369 
370   // All bits for both fast and slow objects must fit in a smi.
371   STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
372   STATIC_ASSERT(FieldIndexField::kNext <= 31);
373 
374   static const int kInitialIndex = 1;
375 
376 #ifdef OBJECT_PRINT
377   // For our gdb macros, we should perhaps change these in the future.
378   void Print(bool dictionary_mode);
379 #endif
380 
381  private:
PropertyDetails(int value,int pointer)382   PropertyDetails(int value, int pointer) {
383     value_ = DescriptorPointer::update(value, pointer);
384   }
PropertyDetails(int value,Representation representation)385   PropertyDetails(int value, Representation representation) {
386     value_ = RepresentationField::update(
387         value, EncodeRepresentation(representation));
388   }
PropertyDetails(int value,PropertyAttributes attributes)389   PropertyDetails(int value, PropertyAttributes attributes) {
390     value_ = AttributesField::update(value, attributes);
391   }
392 
393   uint32_t value_;
394 };
395 
396 
397 std::ostream& operator<<(std::ostream& os,
398                          const PropertyAttributes& attributes);
399 std::ostream& operator<<(std::ostream& os, const PropertyDetails& details);
400 }  // namespace internal
401 }  // namespace v8
402 
403 #endif  // V8_PROPERTY_DETAILS_H_
404