Line data Source code
1 : // Copyright 2017 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_OBJECTS_MAP_H_
6 : #define V8_OBJECTS_MAP_H_
7 :
8 : #include "src/globals.h"
9 : #include "src/objects.h"
10 : #include "src/objects/code.h"
11 : #include "src/objects/heap-object.h"
12 :
13 : // Has to be the last include (doesn't have include guards):
14 : #include "src/objects/object-macros.h"
15 :
16 : namespace v8 {
17 : namespace internal {
18 :
19 : enum InstanceType : uint16_t;
20 :
21 : #define VISITOR_ID_LIST(V) \
22 : V(AllocationSite) \
23 : V(BigInt) \
24 : V(ByteArray) \
25 : V(BytecodeArray) \
26 : V(Cell) \
27 : V(Code) \
28 : V(CodeDataContainer) \
29 : V(ConsString) \
30 : V(Context) \
31 : V(DataHandler) \
32 : V(DataObject) \
33 : V(DescriptorArray) \
34 : V(EmbedderDataArray) \
35 : V(EphemeronHashTable) \
36 : V(FeedbackCell) \
37 : V(FeedbackVector) \
38 : V(FixedArray) \
39 : V(FixedDoubleArray) \
40 : V(FixedFloat64Array) \
41 : V(FixedTypedArrayBase) \
42 : V(FreeSpace) \
43 : V(JSApiObject) \
44 : V(JSArrayBuffer) \
45 : V(JSDataView) \
46 : V(JSObject) \
47 : V(JSObjectFast) \
48 : V(JSTypedArray) \
49 : V(JSWeakCell) \
50 : V(JSWeakRef) \
51 : V(JSWeakCollection) \
52 : V(Map) \
53 : V(NativeContext) \
54 : V(Oddball) \
55 : V(PreparseData) \
56 : V(PropertyArray) \
57 : V(PropertyCell) \
58 : V(PrototypeInfo) \
59 : V(SeqOneByteString) \
60 : V(SeqTwoByteString) \
61 : V(SharedFunctionInfo) \
62 : V(ShortcutCandidate) \
63 : V(SlicedString) \
64 : V(SmallOrderedHashMap) \
65 : V(SmallOrderedHashSet) \
66 : V(SmallOrderedNameDictionary) \
67 : V(Struct) \
68 : V(Symbol) \
69 : V(ThinString) \
70 : V(TransitionArray) \
71 : V(UncompiledDataWithoutPreparseData) \
72 : V(UncompiledDataWithPreparseData) \
73 : V(WasmInstanceObject) \
74 : V(WeakArray)
75 :
76 : // For data objects, JS objects and structs along with generic visitor which
77 : // can visit object of any size we provide visitors specialized by
78 : // object size in words.
79 : // Ids of specialized visitors are declared in a linear order (without
80 : // holes) starting from the id of visitor specialized for 2 words objects
81 : // (base visitor id) and ending with the id of generic visitor.
82 : // Method GetVisitorIdForSize depends on this ordering to calculate visitor
83 : // id of specialized visitor from given instance size, base visitor id and
84 : // generic visitor's id.
85 : enum VisitorId {
86 : #define VISITOR_ID_ENUM_DECL(id) kVisit##id,
87 : VISITOR_ID_LIST(VISITOR_ID_ENUM_DECL)
88 : #undef VISITOR_ID_ENUM_DECL
89 : kVisitorIdCount
90 : };
91 :
92 : typedef std::vector<Handle<Map>> MapHandles;
93 :
94 : // All heap objects have a Map that describes their structure.
95 : // A Map contains information about:
96 : // - Size information about the object
97 : // - How to iterate over an object (for garbage collection)
98 : //
99 : // Map layout:
100 : // +---------------+---------------------------------------------+
101 : // | _ Type _ | _ Description _ |
102 : // +---------------+---------------------------------------------+
103 : // | TaggedPointer | map - Always a pointer to the MetaMap root |
104 : // +---------------+---------------------------------------------+
105 : // | Int | The first int field |
106 : // `---+----------+---------------------------------------------+
107 : // | Byte | [instance_size] |
108 : // +----------+---------------------------------------------+
109 : // | Byte | If Map for a primitive type: |
110 : // | | native context index for constructor fn |
111 : // | | If Map for an Object type: |
112 : // | | inobject properties start offset in words |
113 : // +----------+---------------------------------------------+
114 : // | Byte | [used_or_unused_instance_size_in_words] |
115 : // | | For JSObject in fast mode this byte encodes |
116 : // | | the size of the object that includes only |
117 : // | | the used property fields or the slack size |
118 : // | | in properties backing store. |
119 : // +----------+---------------------------------------------+
120 : // | Byte | [visitor_id] |
121 : // +----+----------+---------------------------------------------+
122 : // | Int | The second int field |
123 : // `---+----------+---------------------------------------------+
124 : // | Short | [instance_type] |
125 : // +----------+---------------------------------------------+
126 : // | Byte | [bit_field] |
127 : // | | - has_non_instance_prototype (bit 0) |
128 : // | | - is_callable (bit 1) |
129 : // | | - has_named_interceptor (bit 2) |
130 : // | | - has_indexed_interceptor (bit 3) |
131 : // | | - is_undetectable (bit 4) |
132 : // | | - is_access_check_needed (bit 5) |
133 : // | | - is_constructor (bit 6) |
134 : // | | - has_prototype_slot (bit 7) |
135 : // +----------+---------------------------------------------+
136 : // | Byte | [bit_field2] |
137 : // | | - is_extensible (bit 0) |
138 : // | | - is_prototype_map (bit 1) |
139 : // | | - is_in_retained_map_list (bit 2) |
140 : // | | - elements_kind (bits 3..7) |
141 : // +----+----------+---------------------------------------------+
142 : // | Int | [bit_field3] |
143 : // | | - enum_length (bit 0..9) |
144 : // | | - number_of_own_descriptors (bit 10..19) |
145 : // | | - is_dictionary_map (bit 20) |
146 : // | | - owns_descriptors (bit 21) |
147 : // | | - has_hidden_prototype (bit 22) |
148 : // | | - is_deprecated (bit 23) |
149 : // | | - is_unstable (bit 24) |
150 : // | | - is_migration_target (bit 25) |
151 : // | | - is_immutable_proto (bit 26) |
152 : // | | - new_target_is_base (bit 27) |
153 : // | | - may_have_interesting_symbols (bit 28) |
154 : // | | - construction_counter (bit 29..31) |
155 : // | | |
156 : // +*************************************************************+
157 : // | Int | On systems with 64bit pointer types, there |
158 : // | | is an unused 32bits after bit_field3 |
159 : // +*************************************************************+
160 : // | TaggedPointer | [prototype] |
161 : // +---------------+---------------------------------------------+
162 : // | TaggedPointer | [constructor_or_backpointer] |
163 : // +---------------+---------------------------------------------+
164 : // | TaggedPointer | If Map is a prototype map: |
165 : // | | [prototype_info] |
166 : // | | Else: |
167 : // | | [raw_transitions] |
168 : // +---------------+---------------------------------------------+
169 : // | TaggedPointer | [instance_descriptors] |
170 : // +*************************************************************+
171 : // ! TaggedPointer ! [layout_descriptors] !
172 : // ! ! Field is only present if compile-time flag !
173 : // ! ! FLAG_unbox_double_fields is enabled !
174 : // ! ! (basically on 64 bit architectures) !
175 : // +*************************************************************+
176 : // | TaggedPointer | [dependent_code] |
177 : // +---------------+---------------------------------------------+
178 :
179 : class Map : public HeapObject {
180 : public:
181 : // Instance size.
182 : // Size in bytes or kVariableSizeSentinel if instances do not have
183 : // a fixed size.
184 : DECL_INT_ACCESSORS(instance_size)
185 : // Size in words or kVariableSizeSentinel if instances do not have
186 : // a fixed size.
187 : DECL_INT_ACCESSORS(instance_size_in_words)
188 :
189 : // [inobject_properties_start_or_constructor_function_index]:
190 : // Provides access to the inobject properties start offset in words in case of
191 : // JSObject maps, or the constructor function index in case of primitive maps.
192 : DECL_INT_ACCESSORS(inobject_properties_start_or_constructor_function_index)
193 :
194 : // Get/set the in-object property area start offset in words in the object.
195 : inline int GetInObjectPropertiesStartInWords() const;
196 : inline void SetInObjectPropertiesStartInWords(int value);
197 : // Count of properties allocated in the object (JSObject only).
198 : inline int GetInObjectProperties() const;
199 : // Index of the constructor function in the native context (primitives only),
200 : // or the special sentinel value to indicate that there is no object wrapper
201 : // for the primitive (i.e. in case of null or undefined).
202 : static const int kNoConstructorFunctionIndex = 0;
203 : inline int GetConstructorFunctionIndex() const;
204 : inline void SetConstructorFunctionIndex(int value);
205 : static MaybeHandle<JSFunction> GetConstructorFunction(
206 : Handle<Map> map, Handle<Context> native_context);
207 :
208 : // Retrieve interceptors.
209 : inline InterceptorInfo GetNamedInterceptor();
210 : inline InterceptorInfo GetIndexedInterceptor();
211 :
212 : // Instance type.
213 : DECL_PRIMITIVE_ACCESSORS(instance_type, InstanceType)
214 :
215 : // Returns the size of the used in-object area including object header
216 : // (only used for JSObject in fast mode, for the other kinds of objects it
217 : // is equal to the instance size).
218 : inline int UsedInstanceSize() const;
219 :
220 : // Tells how many unused property fields (in-object or out-of object) are
221 : // available in the instance (only used for JSObject in fast mode).
222 : inline int UnusedPropertyFields() const;
223 : // Tells how many unused in-object property words are present.
224 : inline int UnusedInObjectProperties() const;
225 : // Updates the counters tracking unused fields in the object.
226 : inline void SetInObjectUnusedPropertyFields(int unused_property_fields);
227 : // Updates the counters tracking unused fields in the property array.
228 : inline void SetOutOfObjectUnusedPropertyFields(int unused_property_fields);
229 : inline void CopyUnusedPropertyFields(Map map);
230 : inline void CopyUnusedPropertyFieldsAdjustedForInstanceSize(Map map);
231 : inline void AccountAddedPropertyField();
232 : inline void AccountAddedOutOfObjectPropertyField(
233 : int unused_in_property_array);
234 :
235 : //
236 : // Bit field.
237 : //
238 : DECL_PRIMITIVE_ACCESSORS(bit_field, byte)
239 :
240 : // Bit positions for |bit_field|.
241 : #define MAP_BIT_FIELD_FIELDS(V, _) \
242 : V(HasNonInstancePrototypeBit, bool, 1, _) \
243 : V(IsCallableBit, bool, 1, _) \
244 : V(HasNamedInterceptorBit, bool, 1, _) \
245 : V(HasIndexedInterceptorBit, bool, 1, _) \
246 : V(IsUndetectableBit, bool, 1, _) \
247 : V(IsAccessCheckNeededBit, bool, 1, _) \
248 : V(IsConstructorBit, bool, 1, _) \
249 : V(HasPrototypeSlotBit, bool, 1, _)
250 :
251 : DEFINE_BIT_FIELDS(MAP_BIT_FIELD_FIELDS)
252 : #undef MAP_BIT_FIELD_FIELDS
253 :
254 : //
255 : // Bit field 2.
256 : //
257 : DECL_PRIMITIVE_ACCESSORS(bit_field2, byte)
258 :
259 : // Bit positions for |bit_field2|.
260 : #define MAP_BIT_FIELD2_FIELDS(V, _) \
261 : V(IsExtensibleBit, bool, 1, _) \
262 : V(IsPrototypeMapBit, bool, 1, _) \
263 : V(IsInRetainedMapListBit, bool, 1, _) \
264 : V(ElementsKindBits, ElementsKind, 5, _)
265 :
266 : DEFINE_BIT_FIELDS(MAP_BIT_FIELD2_FIELDS)
267 : #undef MAP_BIT_FIELD2_FIELDS
268 :
269 : //
270 : // Bit field 3.
271 : //
272 : DECL_PRIMITIVE_ACCESSORS(bit_field3, uint32_t)
273 :
274 : // Bit positions for |bit_field3|.
275 : #define MAP_BIT_FIELD3_FIELDS(V, _) \
276 : V(EnumLengthBits, int, kDescriptorIndexBitCount, _) \
277 : V(NumberOfOwnDescriptorsBits, int, kDescriptorIndexBitCount, _) \
278 : V(IsDictionaryMapBit, bool, 1, _) \
279 : V(OwnsDescriptorsBit, bool, 1, _) \
280 : V(HasHiddenPrototypeBit, bool, 1, _) \
281 : V(IsDeprecatedBit, bool, 1, _) \
282 : V(IsUnstableBit, bool, 1, _) \
283 : V(IsMigrationTargetBit, bool, 1, _) \
284 : V(IsImmutablePrototypeBit, bool, 1, _) \
285 : V(NewTargetIsBaseBit, bool, 1, _) \
286 : V(MayHaveInterestingSymbolsBit, bool, 1, _) \
287 : V(ConstructionCounterBits, int, 3, _)
288 :
289 : DEFINE_BIT_FIELDS(MAP_BIT_FIELD3_FIELDS)
290 : #undef MAP_BIT_FIELD3_FIELDS
291 :
292 : STATIC_ASSERT(NumberOfOwnDescriptorsBits::kMax >= kMaxNumberOfDescriptors);
293 :
294 : static const int kSlackTrackingCounterStart = 7;
295 : static const int kSlackTrackingCounterEnd = 1;
296 : static const int kNoSlackTracking = 0;
297 : STATIC_ASSERT(kSlackTrackingCounterStart <= ConstructionCounterBits::kMax);
298 :
299 : // Inobject slack tracking is the way to reclaim unused inobject space.
300 : //
301 : // The instance size is initially determined by adding some slack to
302 : // expected_nof_properties (to allow for a few extra properties added
303 : // after the constructor). There is no guarantee that the extra space
304 : // will not be wasted.
305 : //
306 : // Here is the algorithm to reclaim the unused inobject space:
307 : // - Detect the first constructor call for this JSFunction.
308 : // When it happens enter the "in progress" state: initialize construction
309 : // counter in the initial_map.
310 : // - While the tracking is in progress initialize unused properties of a new
311 : // object with one_pointer_filler_map instead of undefined_value (the "used"
312 : // part is initialized with undefined_value as usual). This way they can
313 : // be resized quickly and safely.
314 : // - Once enough objects have been created compute the 'slack'
315 : // (traverse the map transition tree starting from the
316 : // initial_map and find the lowest value of unused_property_fields).
317 : // - Traverse the transition tree again and decrease the instance size
318 : // of every map. Existing objects will resize automatically (they are
319 : // filled with one_pointer_filler_map). All further allocations will
320 : // use the adjusted instance size.
321 : // - SharedFunctionInfo's expected_nof_properties left unmodified since
322 : // allocations made using different closures could actually create different
323 : // kind of objects (see prototype inheritance pattern).
324 : //
325 : // Important: inobject slack tracking is not attempted during the snapshot
326 : // creation.
327 :
328 : static const int kGenerousAllocationCount =
329 : kSlackTrackingCounterStart - kSlackTrackingCounterEnd + 1;
330 :
331 : // Starts the tracking by initializing object constructions countdown counter.
332 : void StartInobjectSlackTracking();
333 :
334 : // True if the object constructions countdown counter is a range
335 : // [kSlackTrackingCounterEnd, kSlackTrackingCounterStart].
336 : inline bool IsInobjectSlackTrackingInProgress() const;
337 :
338 : // Does the tracking step.
339 : inline void InobjectSlackTrackingStep(Isolate* isolate);
340 :
341 : // Computes inobject slack for the transition tree starting at this initial
342 : // map.
343 : int ComputeMinObjectSlack(Isolate* isolate);
344 : inline int InstanceSizeFromSlack(int slack) const;
345 :
346 : // Completes inobject slack tracking for the transition tree starting at this
347 : // initial map.
348 : void CompleteInobjectSlackTracking(Isolate* isolate);
349 :
350 : // Tells whether the object in the prototype property will be used
351 : // for instances created from this function. If the prototype
352 : // property is set to a value that is not a JSObject, the prototype
353 : // property will not be used to create instances of the function.
354 : // See ECMA-262, 13.2.2.
355 : DECL_BOOLEAN_ACCESSORS(has_non_instance_prototype)
356 :
357 : // Tells whether the instance has a [[Construct]] internal method.
358 : // This property is implemented according to ES6, section 7.2.4.
359 : DECL_BOOLEAN_ACCESSORS(is_constructor)
360 :
361 : // Tells whether the instance with this map may have properties for
362 : // interesting symbols on it.
363 : // An "interesting symbol" is one for which Name::IsInterestingSymbol()
364 : // returns true, i.e. a well-known symbol like @@toStringTag.
365 : DECL_BOOLEAN_ACCESSORS(may_have_interesting_symbols)
366 :
367 : DECL_BOOLEAN_ACCESSORS(has_prototype_slot)
368 :
369 : // Tells whether the instance with this map has a hidden prototype.
370 : DECL_BOOLEAN_ACCESSORS(has_hidden_prototype)
371 :
372 : // Records and queries whether the instance has a named interceptor.
373 : DECL_BOOLEAN_ACCESSORS(has_named_interceptor)
374 :
375 : // Records and queries whether the instance has an indexed interceptor.
376 : DECL_BOOLEAN_ACCESSORS(has_indexed_interceptor)
377 :
378 : // Tells whether the instance is undetectable.
379 : // An undetectable object is a special class of JSObject: 'typeof' operator
380 : // returns undefined, ToBoolean returns false. Otherwise it behaves like
381 : // a normal JS object. It is useful for implementing undetectable
382 : // document.all in Firefox & Safari.
383 : // See https://bugzilla.mozilla.org/show_bug.cgi?id=248549.
384 : DECL_BOOLEAN_ACCESSORS(is_undetectable)
385 :
386 : // Tells whether the instance has a [[Call]] internal method.
387 : // This property is implemented according to ES6, section 7.2.3.
388 : DECL_BOOLEAN_ACCESSORS(is_callable)
389 :
390 : DECL_BOOLEAN_ACCESSORS(new_target_is_base)
391 : DECL_BOOLEAN_ACCESSORS(is_extensible)
392 : DECL_BOOLEAN_ACCESSORS(is_prototype_map)
393 : inline bool is_abandoned_prototype_map() const;
394 :
395 : // Whether the instance has been added to the retained map list by
396 : // Heap::AddRetainedMap.
397 : DECL_BOOLEAN_ACCESSORS(is_in_retained_map_list)
398 :
399 : DECL_PRIMITIVE_ACCESSORS(elements_kind, ElementsKind)
400 :
401 : // Tells whether the instance has fast elements that are only Smis.
402 : inline bool has_fast_smi_elements() const;
403 :
404 : // Tells whether the instance has fast elements.
405 : inline bool has_fast_object_elements() const;
406 : inline bool has_fast_smi_or_object_elements() const;
407 : inline bool has_fast_double_elements() const;
408 : inline bool has_fast_elements() const;
409 : inline bool has_sloppy_arguments_elements() const;
410 : inline bool has_fast_sloppy_arguments_elements() const;
411 : inline bool has_fast_string_wrapper_elements() const;
412 : inline bool has_fixed_typed_array_elements() const;
413 : inline bool has_dictionary_elements() const;
414 :
415 : // Returns true if the current map doesn't have DICTIONARY_ELEMENTS but if a
416 : // map with DICTIONARY_ELEMENTS was found in the prototype chain.
417 : bool DictionaryElementsInPrototypeChainOnly(Isolate* isolate);
418 :
419 : inline Map ElementsTransitionMap();
420 :
421 : inline FixedArrayBase GetInitialElements() const;
422 :
423 : // [raw_transitions]: Provides access to the transitions storage field.
424 : // Don't call set_raw_transitions() directly to overwrite transitions, use
425 : // the TransitionArray::ReplaceTransitions() wrapper instead!
426 : DECL_ACCESSORS(raw_transitions, MaybeObject)
427 : // [prototype_info]: Per-prototype metadata. Aliased with transitions
428 : // (which prototype maps don't have).
429 : DECL_ACCESSORS(prototype_info, Object)
430 : // PrototypeInfo is created lazily using this helper (which installs it on
431 : // the given prototype's map).
432 : static Handle<PrototypeInfo> GetOrCreatePrototypeInfo(
433 : Handle<JSObject> prototype, Isolate* isolate);
434 : static Handle<PrototypeInfo> GetOrCreatePrototypeInfo(
435 : Handle<Map> prototype_map, Isolate* isolate);
436 : inline bool should_be_fast_prototype_map() const;
437 : static void SetShouldBeFastPrototypeMap(Handle<Map> map, bool value,
438 : Isolate* isolate);
439 :
440 : // [prototype chain validity cell]: Associated with a prototype object,
441 : // stored in that object's map, indicates that prototype chains through this
442 : // object are currently valid. The cell will be invalidated and replaced when
443 : // the prototype chain changes. When there's nothing to guard (for example,
444 : // when direct prototype is null or Proxy) this function returns Smi with
445 : // |kPrototypeChainValid| sentinel value.
446 : static Handle<Object> GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
447 : Isolate* isolate);
448 : static const int kPrototypeChainValid = 0;
449 : static const int kPrototypeChainInvalid = 1;
450 :
451 : static bool IsPrototypeChainInvalidated(Map map);
452 :
453 : // Return the map of the root of object's prototype chain.
454 : Map GetPrototypeChainRootMap(Isolate* isolate) const;
455 :
456 : Map FindRootMap(Isolate* isolate) const;
457 : Map FindFieldOwner(Isolate* isolate, int descriptor) const;
458 :
459 : inline int GetInObjectPropertyOffset(int index) const;
460 :
461 : class FieldCounts {
462 : public:
463 : FieldCounts(int mutable_count, int const_count)
464 : : mutable_count_(mutable_count), const_count_(const_count) {}
465 :
466 2596814 : int GetTotal() const { return mutable_count() + const_count(); }
467 :
468 : int mutable_count() const { return mutable_count_; }
469 : int const_count() const { return const_count_; }
470 :
471 : private:
472 : int mutable_count_;
473 : int const_count_;
474 : };
475 :
476 : FieldCounts GetFieldCounts() const;
477 : int NumberOfFields() const;
478 :
479 : bool HasOutOfObjectProperties() const;
480 :
481 : // Returns true if transition to the given map requires special
482 : // synchronization with the concurrent marker.
483 : bool TransitionRequiresSynchronizationWithGC(Map target) const;
484 : // Returns true if transition to the given map removes a tagged in-object
485 : // field.
486 : bool TransitionRemovesTaggedField(Map target) const;
487 : // Returns true if transition to the given map replaces a tagged in-object
488 : // field with an untagged in-object field.
489 : bool TransitionChangesTaggedFieldToUntaggedField(Map target) const;
490 :
491 : // TODO(ishell): candidate with JSObject::MigrateToMap().
492 : bool InstancesNeedRewriting(Map target) const;
493 : bool InstancesNeedRewriting(Map target, int target_number_of_fields,
494 : int target_inobject, int target_unused,
495 : int* old_number_of_fields) const;
496 : V8_WARN_UNUSED_RESULT static Handle<FieldType> GeneralizeFieldType(
497 : Representation rep1, Handle<FieldType> type1, Representation rep2,
498 : Handle<FieldType> type2, Isolate* isolate);
499 : static void GeneralizeField(Isolate* isolate, Handle<Map> map,
500 : int modify_index, PropertyConstness new_constness,
501 : Representation new_representation,
502 : Handle<FieldType> new_field_type);
503 : // Returns true if |descriptor|'th property is a field that may be generalized
504 : // by just updating current map.
505 : static inline bool IsInplaceGeneralizableField(PropertyConstness constness,
506 : Representation representation,
507 : FieldType field_type);
508 :
509 : // Generalizes constness, representation and field_type if objects with given
510 : // instance type can have fast elements that can be transitioned by stubs or
511 : // optimized code to more general elements kind.
512 : // This generalization is necessary in order to ensure that elements kind
513 : // transitions performed by stubs / optimized code don't silently transition
514 : // PropertyConstness::kMutable fields back to VariableMode::kConst state or
515 : // fields with HeapObject representation and "Any" type back to "Class" type.
516 : static inline void GeneralizeIfCanHaveTransitionableFastElementsKind(
517 : Isolate* isolate, InstanceType instance_type,
518 : PropertyConstness* constness, Representation* representation,
519 : Handle<FieldType>* field_type);
520 :
521 : static Handle<Map> ReconfigureProperty(Isolate* isolate, Handle<Map> map,
522 : int modify_index,
523 : PropertyKind new_kind,
524 : PropertyAttributes new_attributes,
525 : Representation new_representation,
526 : Handle<FieldType> new_field_type);
527 :
528 : static Handle<Map> ReconfigureElementsKind(Isolate* isolate, Handle<Map> map,
529 : ElementsKind new_elements_kind);
530 :
531 : static Handle<Map> PrepareForDataProperty(Isolate* isolate,
532 : Handle<Map> old_map,
533 : int descriptor_number,
534 : PropertyConstness constness,
535 : Handle<Object> value);
536 :
537 : static Handle<Map> Normalize(Isolate* isolate, Handle<Map> map,
538 : PropertyNormalizationMode mode,
539 : const char* reason);
540 :
541 : // Tells whether the map is used for JSObjects in dictionary mode (ie
542 : // normalized objects, ie objects for which HasFastProperties returns false).
543 : // A map can never be used for both dictionary mode and fast mode JSObjects.
544 : // False by default and for HeapObjects that are not JSObjects.
545 : DECL_BOOLEAN_ACCESSORS(is_dictionary_map)
546 :
547 : // Tells whether the instance needs security checks when accessing its
548 : // properties.
549 : DECL_BOOLEAN_ACCESSORS(is_access_check_needed)
550 :
551 : // [prototype]: implicit prototype object.
552 : DECL_ACCESSORS(prototype, Object)
553 : // TODO(jkummerow): make set_prototype private.
554 : static void SetPrototype(Isolate* isolate, Handle<Map> map,
555 : Handle<Object> prototype,
556 : bool enable_prototype_setup_mode = true);
557 :
558 : // [constructor]: points back to the function or FunctionTemplateInfo
559 : // responsible for this map.
560 : // The field overlaps with the back pointer. All maps in a transition tree
561 : // have the same constructor, so maps with back pointers can walk the
562 : // back pointer chain until they find the map holding their constructor.
563 : // Returns null_value if there's neither a constructor function nor a
564 : // FunctionTemplateInfo available.
565 : DECL_ACCESSORS(constructor_or_backpointer, Object)
566 : inline Object GetConstructor() const;
567 : inline FunctionTemplateInfo GetFunctionTemplateInfo() const;
568 : inline void SetConstructor(Object constructor,
569 : WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
570 : // [back pointer]: points back to the parent map from which a transition
571 : // leads to this map. The field overlaps with the constructor (see above).
572 : inline Object GetBackPointer() const;
573 : inline void SetBackPointer(Object value,
574 : WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
575 :
576 : // [instance descriptors]: describes the object.
577 : inline DescriptorArray instance_descriptors() const;
578 : inline DescriptorArray synchronized_instance_descriptors() const;
579 : void SetInstanceDescriptors(Isolate* isolate, DescriptorArray descriptors,
580 : int number_of_own_descriptors);
581 :
582 : // [layout descriptor]: describes the object layout.
583 : DECL_ACCESSORS(layout_descriptor, LayoutDescriptor)
584 : // |layout descriptor| accessor which can be used from GC.
585 : inline LayoutDescriptor layout_descriptor_gc_safe() const;
586 : inline bool HasFastPointerLayout() const;
587 :
588 : // |layout descriptor| accessor that is safe to call even when
589 : // FLAG_unbox_double_fields is disabled (in this case Map does not contain
590 : // |layout_descriptor| field at all).
591 : inline LayoutDescriptor GetLayoutDescriptor() const;
592 :
593 : inline void UpdateDescriptors(Isolate* isolate, DescriptorArray descriptors,
594 : LayoutDescriptor layout_descriptor,
595 : int number_of_own_descriptors);
596 : inline void InitializeDescriptors(Isolate* isolate,
597 : DescriptorArray descriptors,
598 : LayoutDescriptor layout_descriptor);
599 :
600 : // [dependent code]: list of optimized codes that weakly embed this map.
601 : DECL_ACCESSORS(dependent_code, DependentCode)
602 :
603 : // [prototype_validity_cell]: Cell containing the validity bit for prototype
604 : // chains or Smi(0) if uninitialized.
605 : // The meaning of this validity cell is different for prototype maps and
606 : // non-prototype maps.
607 : // For prototype maps the validity bit "guards" modifications of prototype
608 : // chains going through this object. When a prototype object changes, both its
609 : // own validity cell and those of all "downstream" prototypes are invalidated;
610 : // handlers for a given receiver embed the currently valid cell for that
611 : // receiver's prototype during their creation and check it on execution.
612 : // For non-prototype maps which are used as transitioning store handlers this
613 : // field contains the validity cell which guards modifications of this map's
614 : // prototype.
615 : DECL_ACCESSORS(prototype_validity_cell, Object)
616 :
617 : // Returns true if prototype validity cell value represents "valid" prototype
618 : // chain state.
619 : inline bool IsPrototypeValidityCellValid() const;
620 :
621 : inline PropertyDetails GetLastDescriptorDetails() const;
622 :
623 : inline int LastAdded() const;
624 :
625 : inline int NumberOfOwnDescriptors() const;
626 : inline void SetNumberOfOwnDescriptors(int number);
627 :
628 : inline Cell RetrieveDescriptorsPointer();
629 :
630 : // Checks whether all properties are stored either in the map or on the object
631 : // (inobject, properties, or elements backing store), requiring no special
632 : // checks.
633 : bool OnlyHasSimpleProperties() const;
634 : inline int EnumLength() const;
635 : inline void SetEnumLength(int length);
636 :
637 : DECL_BOOLEAN_ACCESSORS(owns_descriptors)
638 :
639 : inline void mark_unstable();
640 : inline bool is_stable() const;
641 :
642 : DECL_BOOLEAN_ACCESSORS(is_migration_target)
643 :
644 : DECL_BOOLEAN_ACCESSORS(is_immutable_proto)
645 :
646 : // This counter is used for in-object slack tracking.
647 : // The in-object slack tracking is considered enabled when the counter is
648 : // non zero. The counter only has a valid count for initial maps. For
649 : // transitioned maps only kNoSlackTracking has a meaning, namely that inobject
650 : // slack tracking already finished for the transition tree. Any other value
651 : // indicates that either inobject slack tracking is still in progress, or that
652 : // the map isn't part of the transition tree anymore.
653 : DECL_INT_ACCESSORS(construction_counter)
654 :
655 : DECL_BOOLEAN_ACCESSORS(is_deprecated)
656 : inline bool CanBeDeprecated() const;
657 : // Returns a non-deprecated version of the input. If the input was not
658 : // deprecated, it is directly returned. Otherwise, the non-deprecated version
659 : // is found by re-transitioning from the root of the transition tree using the
660 : // descriptor array of the map. Returns MaybeHandle<Map>() if no updated map
661 : // is found.
662 : static MaybeHandle<Map> TryUpdate(Isolate* isolate,
663 : Handle<Map> map) V8_WARN_UNUSED_RESULT;
664 : static Map TryUpdateSlow(Isolate* isolate, Map map) V8_WARN_UNUSED_RESULT;
665 :
666 : // Returns a non-deprecated version of the input. This method may deprecate
667 : // existing maps along the way if encodings conflict. Not for use while
668 : // gathering type feedback. Use TryUpdate in those cases instead.
669 : static Handle<Map> Update(Isolate* isolate, Handle<Map> map);
670 :
671 : static inline Handle<Map> CopyInitialMap(Isolate* isolate, Handle<Map> map);
672 : static Handle<Map> CopyInitialMap(Isolate* isolate, Handle<Map> map,
673 : int instance_size, int in_object_properties,
674 : int unused_property_fields);
675 : static Handle<Map> CopyInitialMapNormalized(
676 : Isolate* isolate, Handle<Map> map,
677 : PropertyNormalizationMode mode = CLEAR_INOBJECT_PROPERTIES);
678 : static Handle<Map> CopyDropDescriptors(Isolate* isolate, Handle<Map> map);
679 : static Handle<Map> CopyInsertDescriptor(Isolate* isolate, Handle<Map> map,
680 : Descriptor* descriptor,
681 : TransitionFlag flag);
682 :
683 : static MaybeObjectHandle WrapFieldType(Isolate* isolate,
684 : Handle<FieldType> type);
685 : static FieldType UnwrapFieldType(MaybeObject wrapped_type);
686 :
687 : V8_WARN_UNUSED_RESULT static MaybeHandle<Map> CopyWithField(
688 : Isolate* isolate, Handle<Map> map, Handle<Name> name,
689 : Handle<FieldType> type, PropertyAttributes attributes,
690 : PropertyConstness constness, Representation representation,
691 : TransitionFlag flag);
692 :
693 : V8_WARN_UNUSED_RESULT static MaybeHandle<Map> CopyWithConstant(
694 : Isolate* isolate, Handle<Map> map, Handle<Name> name,
695 : Handle<Object> constant, PropertyAttributes attributes,
696 : TransitionFlag flag);
697 :
698 : // Returns a new map with all transitions dropped from the given map and
699 : // the ElementsKind set.
700 : static Handle<Map> TransitionElementsTo(Isolate* isolate, Handle<Map> map,
701 : ElementsKind to_kind);
702 :
703 : static Handle<Map> AsElementsKind(Isolate* isolate, Handle<Map> map,
704 : ElementsKind kind);
705 :
706 : static Handle<Map> CopyAsElementsKind(Isolate* isolate, Handle<Map> map,
707 : ElementsKind kind, TransitionFlag flag);
708 :
709 : static Handle<Map> AsLanguageMode(Isolate* isolate, Handle<Map> initial_map,
710 : Handle<SharedFunctionInfo> shared_info);
711 :
712 : static Handle<Map> CopyForPreventExtensions(Isolate* isolate, Handle<Map> map,
713 : PropertyAttributes attrs_to_add,
714 : Handle<Symbol> transition_marker,
715 : const char* reason);
716 :
717 : static Handle<Map> FixProxy(Handle<Map> map, InstanceType type, int size);
718 :
719 : // Maximal number of fast properties. Used to restrict the number of map
720 : // transitions to avoid an explosion in the number of maps for objects used as
721 : // dictionaries.
722 : inline bool TooManyFastProperties(StoreOrigin store_origin) const;
723 : static Handle<Map> TransitionToDataProperty(Isolate* isolate, Handle<Map> map,
724 : Handle<Name> name,
725 : Handle<Object> value,
726 : PropertyAttributes attributes,
727 : PropertyConstness constness,
728 : StoreOrigin store_origin);
729 : static Handle<Map> TransitionToAccessorProperty(
730 : Isolate* isolate, Handle<Map> map, Handle<Name> name, int descriptor,
731 : Handle<Object> getter, Handle<Object> setter,
732 : PropertyAttributes attributes);
733 : static Handle<Map> ReconfigureExistingProperty(Isolate* isolate,
734 : Handle<Map> map,
735 : int descriptor,
736 : PropertyKind kind,
737 : PropertyAttributes attributes);
738 :
739 : inline void AppendDescriptor(Isolate* isolate, Descriptor* desc);
740 :
741 : // Returns a copy of the map, prepared for inserting into the transition
742 : // tree (if the |map| owns descriptors then the new one will share
743 : // descriptors with |map|).
744 : static Handle<Map> CopyForElementsTransition(Isolate* isolate,
745 : Handle<Map> map);
746 :
747 : // Returns a copy of the map, with all transitions dropped from the
748 : // instance descriptors.
749 : static Handle<Map> Copy(Isolate* isolate, Handle<Map> map,
750 : const char* reason);
751 : static Handle<Map> Create(Isolate* isolate, int inobject_properties);
752 :
753 : // Returns the next free property index (only valid for FAST MODE).
754 : int NextFreePropertyIndex() const;
755 :
756 : // Returns the number of enumerable properties.
757 : int NumberOfEnumerableProperties() const;
758 :
759 : DECL_CAST(Map)
760 :
761 : static inline int SlackForArraySize(int old_size, int size_limit);
762 :
763 : static void EnsureDescriptorSlack(Isolate* isolate, Handle<Map> map,
764 : int slack);
765 :
766 : // Returns the map to be used for instances when the given {prototype} is
767 : // passed to an Object.create call. Might transition the given {prototype}.
768 : static Handle<Map> GetObjectCreateMap(Isolate* isolate,
769 : Handle<HeapObject> prototype);
770 :
771 : // Similar to {GetObjectCreateMap} but does not transition {prototype} and
772 : // fails gracefully by returning an empty handle instead.
773 : static MaybeHandle<Map> TryGetObjectCreateMap(Isolate* isolate,
774 : Handle<HeapObject> prototype);
775 :
776 : // Computes a hash value for this map, to be used in HashTables and such.
777 : int Hash();
778 :
779 : // Returns the transitioned map for this map with the most generic
780 : // elements_kind that's found in |candidates|, or |nullptr| if no match is
781 : // found at all.
782 : Map FindElementsKindTransitionedMap(Isolate* isolate,
783 : MapHandles const& candidates);
784 :
785 : inline bool CanTransition() const;
786 :
787 : #define DECL_TESTER(Type, ...) inline bool Is##Type##Map() const;
788 : INSTANCE_TYPE_CHECKERS(DECL_TESTER)
789 : #undef DECL_TESTER
790 : inline bool IsBooleanMap() const;
791 : inline bool IsNullOrUndefinedMap() const;
792 : inline bool IsPrimitiveMap() const;
793 : inline bool IsSpecialReceiverMap() const;
794 : inline bool IsCustomElementsReceiverMap() const;
795 :
796 : bool IsMapInArrayPrototypeChain(Isolate* isolate) const;
797 :
798 : // Dispatched behavior.
799 : void MapPrint(std::ostream& os);
800 : DECL_VERIFIER(Map)
801 :
802 : #ifdef VERIFY_HEAP
803 : void DictionaryMapVerify(Isolate* isolate);
804 : #endif
805 :
806 : DECL_PRIMITIVE_ACCESSORS(visitor_id, VisitorId)
807 :
808 : static Handle<Map> TransitionToPrototype(Isolate* isolate, Handle<Map> map,
809 : Handle<Object> prototype);
810 :
811 : static Handle<Map> TransitionToImmutableProto(Isolate* isolate,
812 : Handle<Map> map);
813 :
814 : static const int kMaxPreAllocatedPropertyFields = 255;
815 :
816 : // Layout description.
817 : #define MAP_FIELDS(V) \
818 : /* Raw data fields. */ \
819 : V(kInstanceSizeInWordsOffset, kUInt8Size) \
820 : V(kInObjectPropertiesStartOrConstructorFunctionIndexOffset, kUInt8Size) \
821 : V(kUsedOrUnusedInstanceSizeInWordsOffset, kUInt8Size) \
822 : V(kVisitorIdOffset, kUInt8Size) \
823 : V(kInstanceTypeOffset, kUInt16Size) \
824 : V(kBitFieldOffset, kUInt8Size) \
825 : V(kBitField2Offset, kUInt8Size) \
826 : V(kBitField3Offset, kUInt32Size) \
827 : V(k64BitArchPaddingOffset, \
828 : kSystemPointerSize == kUInt32Size ? 0 : kUInt32Size) \
829 : /* Pointer fields. */ \
830 : V(kPointerFieldsBeginOffset, 0) \
831 : V(kPrototypeOffset, kTaggedSize) \
832 : V(kConstructorOrBackPointerOffset, kTaggedSize) \
833 : V(kTransitionsOrPrototypeInfoOffset, kTaggedSize) \
834 : V(kDescriptorsOffset, kTaggedSize) \
835 : V(kLayoutDescriptorOffset, FLAG_unbox_double_fields ? kTaggedSize : 0) \
836 : V(kDependentCodeOffset, kTaggedSize) \
837 : V(kPrototypeValidityCellOffset, kTaggedSize) \
838 : V(kPointerFieldsEndOffset, 0) \
839 : /* Total size. */ \
840 : V(kSize, 0)
841 :
842 : DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, MAP_FIELDS)
843 : #undef MAP_FIELDS
844 :
845 : STATIC_ASSERT(kInstanceTypeOffset == Internals::kMapInstanceTypeOffset);
846 :
847 : class BodyDescriptor;
848 :
849 : // Compares this map to another to see if they describe equivalent objects.
850 : // If |mode| is set to CLEAR_INOBJECT_PROPERTIES, |other| is treated as if
851 : // it had exactly zero inobject properties.
852 : // The "shared" flags of both this map and |other| are ignored.
853 : bool EquivalentToForNormalization(const Map other,
854 : PropertyNormalizationMode mode) const;
855 :
856 : // Returns true if given field is unboxed double.
857 : inline bool IsUnboxedDoubleField(FieldIndex index) const;
858 :
859 : void PrintMapDetails(std::ostream& os);
860 :
861 : static inline Handle<Map> AddMissingTransitionsForTesting(
862 : Isolate* isolate, Handle<Map> split_map,
863 : Handle<DescriptorArray> descriptors,
864 : Handle<LayoutDescriptor> full_layout_descriptor);
865 :
866 : // Fires when the layout of an object with a leaf map changes.
867 : // This includes adding transitions to the leaf map or changing
868 : // the descriptor array.
869 : inline void NotifyLeafMapLayoutChange(Isolate* isolate);
870 :
871 : static VisitorId GetVisitorId(Map map);
872 :
873 : // Returns true if objects with given instance type are allowed to have
874 : // fast transitionable elements kinds. This predicate is used to ensure
875 : // that objects that can have transitionable fast elements kind will not
876 : // get in-place generalizable fields because the elements kind transition
877 : // performed by stubs or optimized code can't properly generalize such
878 : // fields.
879 : static inline bool CanHaveFastTransitionableElementsKind(
880 : InstanceType instance_type);
881 : inline bool CanHaveFastTransitionableElementsKind() const;
882 :
883 : private:
884 : // This byte encodes either the instance size without the in-object slack or
885 : // the slack size in properties backing store.
886 : // Let H be JSObject::kHeaderSize / kTaggedSize.
887 : // If value >= H then:
888 : // - all field properties are stored in the object.
889 : // - there is no property array.
890 : // - value * kTaggedSize is the actual object size without the slack.
891 : // Otherwise:
892 : // - there is no slack in the object.
893 : // - the property array has value slack slots.
894 : // Note that this encoding requires that H = JSObject::kFieldsAdded.
895 : DECL_INT_ACCESSORS(used_or_unused_instance_size_in_words)
896 :
897 : // Returns the map that this (root) map transitions to if its elements_kind
898 : // is changed to |elements_kind|, or |nullptr| if no such map is cached yet.
899 : Map LookupElementsTransitionMap(Isolate* isolate, ElementsKind elements_kind);
900 :
901 : // Tries to replay property transitions starting from this (root) map using
902 : // the descriptor array of the |map|. The |root_map| is expected to have
903 : // proper elements kind and therefore elements kinds transitions are not
904 : // taken by this function. Returns |nullptr| if matching transition map is
905 : // not found.
906 : Map TryReplayPropertyTransitions(Isolate* isolate, Map map);
907 :
908 : static void ConnectTransition(Isolate* isolate, Handle<Map> parent,
909 : Handle<Map> child, Handle<Name> name,
910 : SimpleTransitionFlag flag);
911 :
912 : bool EquivalentToForTransition(const Map other) const;
913 : bool EquivalentToForElementsKindTransition(const Map other) const;
914 : static Handle<Map> RawCopy(Isolate* isolate, Handle<Map> map,
915 : int instance_size, int inobject_properties);
916 : static Handle<Map> ShareDescriptor(Isolate* isolate, Handle<Map> map,
917 : Handle<DescriptorArray> descriptors,
918 : Descriptor* descriptor);
919 : static Handle<Map> AddMissingTransitions(
920 : Isolate* isolate, Handle<Map> map, Handle<DescriptorArray> descriptors,
921 : Handle<LayoutDescriptor> full_layout_descriptor);
922 : static void InstallDescriptors(
923 : Isolate* isolate, Handle<Map> parent_map, Handle<Map> child_map,
924 : int new_descriptor, Handle<DescriptorArray> descriptors,
925 : Handle<LayoutDescriptor> full_layout_descriptor);
926 : static Handle<Map> CopyAddDescriptor(Isolate* isolate, Handle<Map> map,
927 : Descriptor* descriptor,
928 : TransitionFlag flag);
929 : static Handle<Map> CopyReplaceDescriptors(
930 : Isolate* isolate, Handle<Map> map, Handle<DescriptorArray> descriptors,
931 : Handle<LayoutDescriptor> layout_descriptor, TransitionFlag flag,
932 : MaybeHandle<Name> maybe_name, const char* reason,
933 : SimpleTransitionFlag simple_flag);
934 :
935 : static Handle<Map> CopyReplaceDescriptor(Isolate* isolate, Handle<Map> map,
936 : Handle<DescriptorArray> descriptors,
937 : Descriptor* descriptor, int index,
938 : TransitionFlag flag);
939 : static Handle<Map> CopyNormalized(Isolate* isolate, Handle<Map> map,
940 : PropertyNormalizationMode mode);
941 :
942 : // TODO(ishell): Move to MapUpdater.
943 : static Handle<Map> CopyGeneralizeAllFields(Isolate* isolate, Handle<Map> map,
944 : ElementsKind elements_kind,
945 : int modify_index,
946 : PropertyKind kind,
947 : PropertyAttributes attributes,
948 : const char* reason);
949 :
950 : void DeprecateTransitionTree(Isolate* isolate);
951 :
952 : void ReplaceDescriptors(Isolate* isolate, DescriptorArray new_descriptors,
953 : LayoutDescriptor new_layout_descriptor);
954 :
955 : // Update field type of the given descriptor to new representation and new
956 : // type. The type must be prepared for storing in descriptor array:
957 : // it must be either a simple type or a map wrapped in a weak cell.
958 : void UpdateFieldType(Isolate* isolate, int descriptor_number,
959 : Handle<Name> name, PropertyConstness new_constness,
960 : Representation new_representation,
961 : const MaybeObjectHandle& new_wrapped_type);
962 :
963 : // TODO(ishell): Move to MapUpdater.
964 : void PrintReconfiguration(Isolate* isolate, FILE* file, int modify_index,
965 : PropertyKind kind, PropertyAttributes attributes);
966 : // TODO(ishell): Move to MapUpdater.
967 : void PrintGeneralization(
968 : Isolate* isolate, FILE* file, const char* reason, int modify_index,
969 : int split, int descriptors, bool constant_to_field,
970 : Representation old_representation, Representation new_representation,
971 : MaybeHandle<FieldType> old_field_type, MaybeHandle<Object> old_value,
972 : MaybeHandle<FieldType> new_field_type, MaybeHandle<Object> new_value);
973 :
974 : // Use the high-level instance_descriptors/SetInstanceDescriptors instead.
975 : inline void set_synchronized_instance_descriptors(
976 : DescriptorArray array, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
977 :
978 : static const int kFastPropertiesSoftLimit = 12;
979 : static const int kMaxFastProperties = 128;
980 :
981 : friend class MapUpdater;
982 :
983 12320148367 : OBJECT_CONSTRUCTORS(Map, HeapObject);
984 : };
985 :
986 : // The cache for maps used by normalized (dictionary mode) objects.
987 : // Such maps do not have property descriptors, so a typical program
988 : // needs very limited number of distinct normalized maps.
989 : class NormalizedMapCache : public WeakFixedArray {
990 : public:
991 : NEVER_READ_ONLY_SPACE
992 : static Handle<NormalizedMapCache> New(Isolate* isolate);
993 :
994 : V8_WARN_UNUSED_RESULT MaybeHandle<Map> Get(Handle<Map> fast_map,
995 : PropertyNormalizationMode mode);
996 : void Set(Handle<Map> fast_map, Handle<Map> normalized_map);
997 :
998 : DECL_CAST(NormalizedMapCache)
999 :
1000 : static inline bool IsNormalizedMapCache(const HeapObject obj);
1001 :
1002 : DECL_VERIFIER(NormalizedMapCache)
1003 :
1004 : private:
1005 : static const int kEntries = 64;
1006 :
1007 : static inline int GetIndex(Handle<Map> map);
1008 :
1009 : // The following declarations hide base class methods.
1010 : Object get(int index);
1011 : void set(int index, Object value);
1012 :
1013 : OBJECT_CONSTRUCTORS(NormalizedMapCache, WeakFixedArray)
1014 : };
1015 :
1016 : } // namespace internal
1017 : } // namespace v8
1018 :
1019 : #include "src/objects/object-macros-undef.h"
1020 :
1021 : #endif // V8_OBJECTS_MAP_H_
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