V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
property-details.h
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 // TODO(ishell): remove once FLAG_track_constant_fields is removed.
11 #include "src/flags.h"
12 #include "src/utils.h"
13 
14 namespace v8 {
15 namespace internal {
16 
17 // ES6 6.1.7.1
18 enum PropertyAttributes {
19  NONE = ::v8::None,
20  READ_ONLY = ::v8::ReadOnly,
21  DONT_ENUM = ::v8::DontEnum,
22  DONT_DELETE = ::v8::DontDelete,
23 
24  ALL_ATTRIBUTES_MASK = READ_ONLY | DONT_ENUM | DONT_DELETE,
25 
26  SEALED = DONT_DELETE,
27  FROZEN = SEALED | READ_ONLY,
28 
29  ABSENT = 64, // Used in runtime to indicate a property is absent.
30  // ABSENT can never be stored in or returned from a descriptor's attributes
31  // bitfield. It is only used as a return value meaning the attributes of
32  // a non-existent property.
33 };
34 
35 
36 enum PropertyFilter {
37  ALL_PROPERTIES = 0,
38  ONLY_WRITABLE = 1,
39  ONLY_ENUMERABLE = 2,
40  ONLY_CONFIGURABLE = 4,
41  SKIP_STRINGS = 8,
42  SKIP_SYMBOLS = 16,
43  ONLY_ALL_CAN_READ = 32,
44  ENUMERABLE_STRINGS = ONLY_ENUMERABLE | SKIP_SYMBOLS,
45 };
46 // Enable fast comparisons of PropertyAttributes against PropertyFilters.
47 STATIC_ASSERT(ALL_PROPERTIES == static_cast<PropertyFilter>(NONE));
48 STATIC_ASSERT(ONLY_WRITABLE == static_cast<PropertyFilter>(READ_ONLY));
49 STATIC_ASSERT(ONLY_ENUMERABLE == static_cast<PropertyFilter>(DONT_ENUM));
50 STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(DONT_DELETE));
51 STATIC_ASSERT(((SKIP_STRINGS | SKIP_SYMBOLS | ONLY_ALL_CAN_READ) &
52  ALL_ATTRIBUTES_MASK) == 0);
53 STATIC_ASSERT(ALL_PROPERTIES ==
54  static_cast<PropertyFilter>(v8::PropertyFilter::ALL_PROPERTIES));
55 STATIC_ASSERT(ONLY_WRITABLE ==
56  static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_WRITABLE));
57 STATIC_ASSERT(ONLY_ENUMERABLE ==
58  static_cast<PropertyFilter>(v8::PropertyFilter::ONLY_ENUMERABLE));
59 STATIC_ASSERT(ONLY_CONFIGURABLE == static_cast<PropertyFilter>(
60  v8::PropertyFilter::ONLY_CONFIGURABLE));
61 STATIC_ASSERT(SKIP_STRINGS ==
62  static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_STRINGS));
63 STATIC_ASSERT(SKIP_SYMBOLS ==
64  static_cast<PropertyFilter>(v8::PropertyFilter::SKIP_SYMBOLS));
65 
66 class Smi;
67 class TypeInfo;
68 
69 // Order of kinds is significant.
70 // Must fit in the BitField PropertyDetails::KindField.
71 enum PropertyKind { kData = 0, kAccessor = 1 };
72 
73 // Order of modes is significant.
74 // Must fit in the BitField PropertyDetails::LocationField.
75 enum PropertyLocation { kField = 0, kDescriptor = 1 };
76 
77 // Order of modes is significant.
78 // Must fit in the BitField PropertyDetails::ConstnessField.
79 enum class PropertyConstness { kMutable = 0, kConst = 1 };
80 
81 // TODO(ishell): remove once constant field tracking is done.
82 const PropertyConstness kDefaultFieldConstness =
83  FLAG_track_constant_fields ? PropertyConstness::kConst
84  : PropertyConstness::kMutable;
85 
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_NE(kind_, kExternal);
138  DCHECK_NE(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 static const int kFirstInobjectPropertyOffsetBitCount = 7;
202 // The maximum number of descriptors we want in a descriptor array. It should
203 // fit in a page and also the following should hold:
204 // kMaxNumberOfDescriptors + kFieldsAdded <= PropertyArray::kMaxLength.
205 static const int kMaxNumberOfDescriptors = (1 << kDescriptorIndexBitCount) - 4;
206 static const int kInvalidEnumCacheSentinel =
207  (1 << kDescriptorIndexBitCount) - 1;
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, invalidated or never
219  // existed.
220 
221  // For dictionaries not holding cells.
222  kNoCell = kMutable,
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.
234  public:
235  // Property details for dictionary mode properties/elements.
236  PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
237  PropertyCellType cell_type, int dictionary_index = 0) {
238  value_ = KindField::encode(kind) | LocationField::encode(kField) |
239  AttributesField::encode(attributes) |
240  DictionaryStorageField::encode(dictionary_index) |
241  PropertyCellTypeField::encode(cell_type);
242  }
243 
244  // Property details for fast mode properties.
245  PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
246  PropertyLocation location, PropertyConstness constness,
247  Representation representation, int field_index = 0) {
248  value_ = KindField::encode(kind) | AttributesField::encode(attributes) |
249  LocationField::encode(location) |
250  ConstnessField::encode(constness) |
251  RepresentationField::encode(EncodeRepresentation(representation)) |
252  FieldIndexField::encode(field_index);
253  }
254 
255  static PropertyDetails Empty(
256  PropertyCellType cell_type = PropertyCellType::kNoCell) {
257  return PropertyDetails(kData, NONE, cell_type);
258  }
259 
260  int pointer() const { return DescriptorPointer::decode(value_); }
261 
262  PropertyDetails set_pointer(int i) const {
263  return PropertyDetails(value_, i);
264  }
265 
266  PropertyDetails set_cell_type(PropertyCellType type) const {
267  PropertyDetails details = *this;
268  details.value_ = PropertyCellTypeField::update(details.value_, type);
269  return details;
270  }
271 
272  PropertyDetails set_index(int index) const {
273  PropertyDetails details = *this;
274  details.value_ = DictionaryStorageField::update(details.value_, index);
275  return details;
276  }
277 
278  PropertyDetails CopyWithRepresentation(Representation representation) const {
279  return PropertyDetails(value_, representation);
280  }
281  PropertyDetails CopyWithConstness(PropertyConstness constness) const {
282  return PropertyDetails(value_, constness);
283  }
284  PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
285  new_attributes =
286  static_cast<PropertyAttributes>(attributes() | new_attributes);
287  return PropertyDetails(value_, new_attributes);
288  }
289 
290  // Conversion for storing details as Object*.
291  explicit inline PropertyDetails(Smi smi);
292  inline Smi AsSmi() const;
293 
294  static uint8_t EncodeRepresentation(Representation representation) {
295  return representation.kind();
296  }
297 
298  static Representation DecodeRepresentation(uint32_t bits) {
299  return Representation::FromKind(static_cast<Representation::Kind>(bits));
300  }
301 
302  PropertyKind kind() const { return KindField::decode(value_); }
303  PropertyLocation location() const { return LocationField::decode(value_); }
304  PropertyConstness constness() const { return ConstnessField::decode(value_); }
305 
306  PropertyAttributes attributes() const {
307  return AttributesField::decode(value_);
308  }
309 
310  int dictionary_index() const {
311  return DictionaryStorageField::decode(value_);
312  }
313 
314  Representation representation() const {
315  return DecodeRepresentation(RepresentationField::decode(value_));
316  }
317 
318  int field_index() const { return FieldIndexField::decode(value_); }
319 
320  inline int field_width_in_words() const;
321 
322  static bool IsValidIndex(int index) {
323  return DictionaryStorageField::is_valid(index);
324  }
325 
326  bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
327  bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
328  bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
329  bool IsEnumerable() const { return !IsDontEnum(); }
330  PropertyCellType cell_type() const {
331  return PropertyCellTypeField::decode(value_);
332  }
333 
334  // Bit fields in value_ (type, shift, size). Must be public so the
335  // constants can be embedded in generated code.
336  class KindField : public BitField<PropertyKind, 0, 1> {};
337  class LocationField : public BitField<PropertyLocation, KindField::kNext, 1> {
338  };
340  : public BitField<PropertyConstness, LocationField::kNext, 1> {};
342  : public BitField<PropertyAttributes, ConstnessField::kNext, 3> {};
343  static const int kAttributesReadOnlyMask =
344  (READ_ONLY << AttributesField::kShift);
345  static const int kAttributesDontDeleteMask =
346  (DONT_DELETE << AttributesField::kShift);
347  static const int kAttributesDontEnumMask =
348  (DONT_ENUM << AttributesField::kShift);
349 
350  // Bit fields for normalized objects.
352  : public BitField<PropertyCellType, AttributesField::kNext, 2> {};
354  : public BitField<uint32_t, PropertyCellTypeField::kNext, 23> {};
355 
356  // Bit fields for fast objects.
358  : public BitField<uint32_t, AttributesField::kNext, 4> {};
360  : public BitField<uint32_t, RepresentationField::kNext,
361  kDescriptorIndexBitCount> {}; // NOLINT
362  class FieldIndexField : public BitField<uint32_t, DescriptorPointer::kNext,
363  kDescriptorIndexBitCount> {
364  }; // NOLINT
365 
366  // All bits for both fast and slow objects must fit in a smi.
367  STATIC_ASSERT(DictionaryStorageField::kNext <= 31);
368  STATIC_ASSERT(FieldIndexField::kNext <= 31);
369 
370  static const int kInitialIndex = 1;
371 
372 #ifdef OBJECT_PRINT
373  // For our gdb macros, we should perhaps change these in the future.
374  void Print(bool dictionary_mode);
375 #endif
376 
377  enum PrintMode {
378  kPrintAttributes = 1 << 0,
379  kPrintFieldIndex = 1 << 1,
380  kPrintRepresentation = 1 << 2,
381  kPrintPointer = 1 << 3,
382 
383  kForProperties = kPrintFieldIndex,
384  kForTransitions = kPrintAttributes,
385  kPrintFull = -1,
386  };
387  void PrintAsSlowTo(std::ostream& out);
388  void PrintAsFastTo(std::ostream& out, PrintMode mode = kPrintFull);
389 
390  private:
391  PropertyDetails(int value, int pointer) {
392  value_ = DescriptorPointer::update(value, pointer);
393  }
394  PropertyDetails(int value, Representation representation) {
395  value_ = RepresentationField::update(
396  value, EncodeRepresentation(representation));
397  }
398  PropertyDetails(int value, PropertyConstness constness) {
399  value_ = ConstnessField::update(value, constness);
400  }
401  PropertyDetails(int value, PropertyAttributes attributes) {
402  value_ = AttributesField::update(value, attributes);
403  }
404 
405  uint32_t value_;
406 };
407 
408 // kField location is more general than kDescriptor, kDescriptor generalizes
409 // only to itself.
410 inline bool IsGeneralizableTo(PropertyLocation a, PropertyLocation b) {
411  return b == kField || a == kDescriptor;
412 }
413 
414 // PropertyConstness::kMutable constness is more general than
415 // VariableMode::kConst, VariableMode::kConst generalizes only to itself.
416 inline bool IsGeneralizableTo(PropertyConstness a, PropertyConstness b) {
417  return b == PropertyConstness::kMutable || a == PropertyConstness::kConst;
418 }
419 
420 inline PropertyConstness GeneralizeConstness(PropertyConstness a,
421  PropertyConstness b) {
422  return a == PropertyConstness::kMutable ? PropertyConstness::kMutable : b;
423 }
424 
425 std::ostream& operator<<(std::ostream& os,
426  const PropertyAttributes& attributes);
427 } // namespace internal
428 } // namespace v8
429 
430 #endif // V8_PROPERTY_DETAILS_H_
Definition: libplatform.h:13
PropertyFilter
Definition: v8.h:3185