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 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 ? kConst : kMutable;
84
85 class Representation {
86 public:
87 enum Kind {
88 kNone,
89 kInteger8,
90 kUInteger8,
91 kInteger16,
92 kUInteger16,
93 kSmi,
94 kInteger32,
95 kDouble,
96 kHeapObject,
97 kTagged,
98 kExternal,
99 kNumRepresentations
100 };
101
Representation()102 Representation() : kind_(kNone) { }
103
None()104 static Representation None() { return Representation(kNone); }
Tagged()105 static Representation Tagged() { return Representation(kTagged); }
Integer8()106 static Representation Integer8() { return Representation(kInteger8); }
UInteger8()107 static Representation UInteger8() { return Representation(kUInteger8); }
Integer16()108 static Representation Integer16() { return Representation(kInteger16); }
UInteger16()109 static Representation UInteger16() { return Representation(kUInteger16); }
Smi()110 static Representation Smi() { return Representation(kSmi); }
Integer32()111 static Representation Integer32() { return Representation(kInteger32); }
Double()112 static Representation Double() { return Representation(kDouble); }
HeapObject()113 static Representation HeapObject() { return Representation(kHeapObject); }
External()114 static Representation External() { return Representation(kExternal); }
115
FromKind(Kind kind)116 static Representation FromKind(Kind kind) { return Representation(kind); }
117
Equals(const Representation & other)118 bool Equals(const Representation& other) const {
119 return kind_ == other.kind_;
120 }
121
IsCompatibleForLoad(const Representation & other)122 bool IsCompatibleForLoad(const Representation& other) const {
123 return (IsDouble() && other.IsDouble()) ||
124 (!IsDouble() && !other.IsDouble());
125 }
126
IsCompatibleForStore(const Representation & other)127 bool IsCompatibleForStore(const Representation& other) const {
128 return Equals(other);
129 }
130
is_more_general_than(const Representation & other)131 bool is_more_general_than(const Representation& other) const {
132 if (kind_ == kExternal && other.kind_ == kNone) return true;
133 if (kind_ == kExternal && other.kind_ == kExternal) return false;
134 if (kind_ == kNone && other.kind_ == kExternal) return false;
135
136 DCHECK_NE(kind_, kExternal);
137 DCHECK_NE(other.kind_, kExternal);
138 if (IsHeapObject()) return other.IsNone();
139 if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
140 if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
141 return kind_ > other.kind_;
142 }
143
fits_into(const Representation & other)144 bool fits_into(const Representation& other) const {
145 return other.is_more_general_than(*this) || other.Equals(*this);
146 }
147
generalize(Representation other)148 Representation generalize(Representation other) {
149 if (other.fits_into(*this)) return *this;
150 if (other.is_more_general_than(*this)) return other;
151 return Representation::Tagged();
152 }
153
size()154 int size() const {
155 DCHECK(!IsNone());
156 if (IsInteger8() || IsUInteger8()) {
157 return sizeof(uint8_t);
158 }
159 if (IsInteger16() || IsUInteger16()) {
160 return sizeof(uint16_t);
161 }
162 if (IsInteger32()) {
163 return sizeof(uint32_t);
164 }
165 return kPointerSize;
166 }
167
kind()168 Kind kind() const { return static_cast<Kind>(kind_); }
IsNone()169 bool IsNone() const { return kind_ == kNone; }
IsInteger8()170 bool IsInteger8() const { return kind_ == kInteger8; }
IsUInteger8()171 bool IsUInteger8() const { return kind_ == kUInteger8; }
IsInteger16()172 bool IsInteger16() const { return kind_ == kInteger16; }
IsUInteger16()173 bool IsUInteger16() const { return kind_ == kUInteger16; }
IsTagged()174 bool IsTagged() const { return kind_ == kTagged; }
IsSmi()175 bool IsSmi() const { return kind_ == kSmi; }
IsSmiOrTagged()176 bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
IsInteger32()177 bool IsInteger32() const { return kind_ == kInteger32; }
IsSmiOrInteger32()178 bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }
IsDouble()179 bool IsDouble() const { return kind_ == kDouble; }
IsHeapObject()180 bool IsHeapObject() const { return kind_ == kHeapObject; }
IsExternal()181 bool IsExternal() const { return kind_ == kExternal; }
IsSpecialization()182 bool IsSpecialization() const {
183 return IsInteger8() || IsUInteger8() ||
184 IsInteger16() || IsUInteger16() ||
185 IsSmi() || IsInteger32() || IsDouble();
186 }
187 const char* Mnemonic() const;
188
189 private:
Representation(Kind k)190 explicit Representation(Kind k) : kind_(k) { }
191
192 // Make sure kind fits in int8.
193 STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
194
195 int8_t kind_;
196 };
197
198
199 static const int kDescriptorIndexBitCount = 10;
200 static const int kFirstInobjectPropertyOffsetBitCount = 7;
201 // The maximum number of descriptors we want in a descriptor array. It should
202 // fit in a page and also the following should hold:
203 // kMaxNumberOfDescriptors + kFieldsAdded <= PropertyArray::kMaxLength.
204 static const int kMaxNumberOfDescriptors = (1 << kDescriptorIndexBitCount) - 4;
205 static const int kInvalidEnumCacheSentinel =
206 (1 << kDescriptorIndexBitCount) - 1;
207
208 enum class PropertyCellType {
209 // Meaningful when a property cell does not contain the hole.
210 kUndefined, // The PREMONOMORPHIC of property cells.
211 kConstant, // Cell has been assigned only once.
212 kConstantType, // Cell has been assigned only one type.
213 kMutable, // Cell will no longer be tracked as constant.
214
215 // Meaningful when a property cell contains the hole.
216 kUninitialized = kUndefined, // Cell has never been initialized.
217 kInvalidated = kConstant, // Cell has been deleted, invalidated or never
218 // existed.
219
220 // For dictionaries not holding cells.
221 kNoCell = kMutable,
222 };
223
224 enum class PropertyCellConstantType {
225 kSmi,
226 kStableMap,
227 };
228
229
230 // PropertyDetails captures type and attributes for a property.
231 // They are used both in property dictionaries and instance descriptors.
232 class PropertyDetails BASE_EMBEDDED {
233 public:
234 // Property details for dictionary mode properties/elements.
235 PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
236 PropertyCellType cell_type, int dictionary_index = 0) {
237 value_ = KindField::encode(kind) | LocationField::encode(kField) |
238 AttributesField::encode(attributes) |
239 DictionaryStorageField::encode(dictionary_index) |
240 PropertyCellTypeField::encode(cell_type);
241 }
242
243 // Property details for fast mode properties.
244 PropertyDetails(PropertyKind kind, PropertyAttributes attributes,
245 PropertyLocation location, PropertyConstness constness,
246 Representation representation, int field_index = 0) {
247 value_ = KindField::encode(kind) | AttributesField::encode(attributes) |
248 LocationField::encode(location) |
249 ConstnessField::encode(constness) |
250 RepresentationField::encode(EncodeRepresentation(representation)) |
251 FieldIndexField::encode(field_index);
252 }
253
254 static PropertyDetails Empty(
255 PropertyCellType cell_type = PropertyCellType::kNoCell) {
256 return PropertyDetails(kData, NONE, cell_type);
257 }
258
pointer()259 int pointer() const { return DescriptorPointer::decode(value_); }
260
set_pointer(int i)261 PropertyDetails set_pointer(int i) const {
262 return PropertyDetails(value_, i);
263 }
264
set_cell_type(PropertyCellType type)265 PropertyDetails set_cell_type(PropertyCellType type) const {
266 PropertyDetails details = *this;
267 details.value_ = PropertyCellTypeField::update(details.value_, type);
268 return details;
269 }
270
set_index(int index)271 PropertyDetails set_index(int index) const {
272 PropertyDetails details = *this;
273 details.value_ = DictionaryStorageField::update(details.value_, index);
274 return details;
275 }
276
CopyWithRepresentation(Representation representation)277 PropertyDetails CopyWithRepresentation(Representation representation) const {
278 return PropertyDetails(value_, representation);
279 }
CopyWithConstness(PropertyConstness constness)280 PropertyDetails CopyWithConstness(PropertyConstness constness) const {
281 return PropertyDetails(value_, constness);
282 }
CopyAddAttributes(PropertyAttributes new_attributes)283 PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) const {
284 new_attributes =
285 static_cast<PropertyAttributes>(attributes() | new_attributes);
286 return PropertyDetails(value_, new_attributes);
287 }
288
289 // Conversion for storing details as Object*.
290 explicit inline PropertyDetails(Smi* smi);
291 inline Smi* AsSmi() const;
292
EncodeRepresentation(Representation representation)293 static uint8_t EncodeRepresentation(Representation representation) {
294 return representation.kind();
295 }
296
DecodeRepresentation(uint32_t bits)297 static Representation DecodeRepresentation(uint32_t bits) {
298 return Representation::FromKind(static_cast<Representation::Kind>(bits));
299 }
300
kind()301 PropertyKind kind() const { return KindField::decode(value_); }
location()302 PropertyLocation location() const { return LocationField::decode(value_); }
constness()303 PropertyConstness constness() const { return ConstnessField::decode(value_); }
304
attributes()305 PropertyAttributes attributes() const {
306 return AttributesField::decode(value_);
307 }
308
dictionary_index()309 int dictionary_index() const {
310 return DictionaryStorageField::decode(value_);
311 }
312
representation()313 Representation representation() const {
314 return DecodeRepresentation(RepresentationField::decode(value_));
315 }
316
field_index()317 int field_index() const { return FieldIndexField::decode(value_); }
318
319 inline int field_width_in_words() const;
320
IsValidIndex(int index)321 static bool IsValidIndex(int index) {
322 return DictionaryStorageField::is_valid(index);
323 }
324
IsReadOnly()325 bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
IsConfigurable()326 bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
IsDontEnum()327 bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
IsEnumerable()328 bool IsEnumerable() const { return !IsDontEnum(); }
cell_type()329 PropertyCellType cell_type() const {
330 return PropertyCellTypeField::decode(value_);
331 }
332
333 // Bit fields in value_ (type, shift, size). Must be public so the
334 // constants can be embedded in generated code.
335 class KindField : public BitField<PropertyKind, 0, 1> {};
336 class LocationField : public BitField<PropertyLocation, KindField::kNext, 1> {
337 };
338 class ConstnessField
339 : public BitField<PropertyConstness, LocationField::kNext, 1> {};
340 class AttributesField
341 : public BitField<PropertyAttributes, ConstnessField::kNext, 3> {};
342 static const int kAttributesReadOnlyMask =
343 (READ_ONLY << AttributesField::kShift);
344 static const int kAttributesDontDeleteMask =
345 (DONT_DELETE << AttributesField::kShift);
346 static const int kAttributesDontEnumMask =
347 (DONT_ENUM << AttributesField::kShift);
348
349 // Bit fields for normalized objects.
350 class PropertyCellTypeField
351 : public BitField<PropertyCellType, AttributesField::kNext, 2> {};
352 class DictionaryStorageField
353 : public BitField<uint32_t, PropertyCellTypeField::kNext, 23> {};
354
355 // Bit fields for fast objects.
356 class RepresentationField
357 : public BitField<uint32_t, AttributesField::kNext, 4> {};
358 class DescriptorPointer
359 : public BitField<uint32_t, RepresentationField::kNext,
360 kDescriptorIndexBitCount> {}; // NOLINT
361 class FieldIndexField : public BitField<uint32_t, DescriptorPointer::kNext,
362 kDescriptorIndexBitCount> {
363 }; // NOLINT
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 enum PrintMode {
377 kPrintAttributes = 1 << 0,
378 kPrintFieldIndex = 1 << 1,
379 kPrintRepresentation = 1 << 2,
380 kPrintPointer = 1 << 3,
381
382 kForProperties = kPrintFieldIndex,
383 kForTransitions = kPrintAttributes,
384 kPrintFull = -1,
385 };
386 void PrintAsSlowTo(std::ostream& out);
387 void PrintAsFastTo(std::ostream& out, PrintMode mode = kPrintFull);
388
389 private:
PropertyDetails(int value,int pointer)390 PropertyDetails(int value, int pointer) {
391 value_ = DescriptorPointer::update(value, pointer);
392 }
PropertyDetails(int value,Representation representation)393 PropertyDetails(int value, Representation representation) {
394 value_ = RepresentationField::update(
395 value, EncodeRepresentation(representation));
396 }
PropertyDetails(int value,PropertyConstness constness)397 PropertyDetails(int value, PropertyConstness constness) {
398 value_ = ConstnessField::update(value, constness);
399 }
PropertyDetails(int value,PropertyAttributes attributes)400 PropertyDetails(int value, PropertyAttributes attributes) {
401 value_ = AttributesField::update(value, attributes);
402 }
403
404 uint32_t value_;
405 };
406
407 // kField location is more general than kDescriptor, kDescriptor generalizes
408 // only to itself.
IsGeneralizableTo(PropertyLocation a,PropertyLocation b)409 inline bool IsGeneralizableTo(PropertyLocation a, PropertyLocation b) {
410 return b == kField || a == kDescriptor;
411 }
412
413 // kMutable constness is more general than kConst, kConst generalizes only to
414 // itself.
IsGeneralizableTo(PropertyConstness a,PropertyConstness b)415 inline bool IsGeneralizableTo(PropertyConstness a, PropertyConstness b) {
416 return b == kMutable || a == kConst;
417 }
418
GeneralizeConstness(PropertyConstness a,PropertyConstness b)419 inline PropertyConstness GeneralizeConstness(PropertyConstness a,
420 PropertyConstness b) {
421 return a == kMutable ? kMutable : b;
422 }
423
424 std::ostream& operator<<(std::ostream& os,
425 const PropertyAttributes& attributes);
426 } // namespace internal
427 } // namespace v8
428
429 #endif // V8_PROPERTY_DETAILS_H_
430