Unreviewed, roll out r171641-r171644. It broke some tests; will investigate and
[WebKit-https.git] / Source / JavaScriptCore / runtime / Structure.cpp
1 /*
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25
26 #include "config.h"
27 #include "Structure.h"
28
29 #include "CodeBlock.h"
30 #include "DumpContext.h"
31 #include "JSCInlines.h"
32 #include "JSObject.h"
33 #include "JSPropertyNameIterator.h"
34 #include "Lookup.h"
35 #include "PropertyMapHashTable.h"
36 #include "PropertyNameArray.h"
37 #include "StructureChain.h"
38 #include "StructureRareDataInlines.h"
39 #include <wtf/CommaPrinter.h>
40 #include <wtf/ProcessID.h>
41 #include <wtf/RefCountedLeakCounter.h>
42 #include <wtf/RefPtr.h>
43 #include <wtf/Threading.h>
44
45 #define DUMP_STRUCTURE_ID_STATISTICS 0
46
47 #ifndef NDEBUG
48 #define DO_PROPERTYMAP_CONSTENCY_CHECK 0
49 #else
50 #define DO_PROPERTYMAP_CONSTENCY_CHECK 0
51 #endif
52
53 using namespace std;
54 using namespace WTF;
55
56 namespace JSC {
57
58 #if DUMP_STRUCTURE_ID_STATISTICS
59 static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
60 #endif
61
62 bool StructureTransitionTable::contains(StringImpl* rep, unsigned attributes) const
63 {
64     if (isUsingSingleSlot()) {
65         Structure* transition = singleTransition();
66         return transition && transition->m_nameInPrevious == rep && transition->m_attributesInPrevious == attributes;
67     }
68     return map()->get(std::make_pair(rep, attributes));
69 }
70
71 inline Structure* StructureTransitionTable::get(StringImpl* rep, unsigned attributes) const
72 {
73     if (isUsingSingleSlot()) {
74         Structure* transition = singleTransition();
75         return (transition && transition->m_nameInPrevious == rep && transition->m_attributesInPrevious == attributes) ? transition : 0;
76     }
77     return map()->get(std::make_pair(rep, attributes));
78 }
79
80 inline void StructureTransitionTable::add(VM& vm, Structure* structure)
81 {
82     if (isUsingSingleSlot()) {
83         Structure* existingTransition = singleTransition();
84
85         // This handles the first transition being added.
86         if (!existingTransition) {
87             setSingleTransition(vm, structure);
88             return;
89         }
90
91         // This handles the second transition being added
92         // (or the first transition being despecified!)
93         setMap(new TransitionMap());
94         add(vm, existingTransition);
95     }
96
97     // Add the structure to the map.
98
99     // Newer versions of the STL have an std::make_pair function that takes rvalue references.
100     // When either of the parameters are bitfields, the C++ compiler will try to bind them as lvalues, which is invalid. To work around this, use unary "+" to make the parameter an rvalue.
101     // See https://bugs.webkit.org/show_bug.cgi?id=59261 for more details
102     map()->set(std::make_pair(structure->m_nameInPrevious.get(), +structure->m_attributesInPrevious), structure);
103 }
104
105 void Structure::dumpStatistics()
106 {
107 #if DUMP_STRUCTURE_ID_STATISTICS
108     unsigned numberLeaf = 0;
109     unsigned numberUsingSingleSlot = 0;
110     unsigned numberSingletons = 0;
111     unsigned numberWithPropertyMaps = 0;
112     unsigned totalPropertyMapsSize = 0;
113
114     HashSet<Structure*>::const_iterator end = liveStructureSet.end();
115     for (HashSet<Structure*>::const_iterator it = liveStructureSet.begin(); it != end; ++it) {
116         Structure* structure = *it;
117
118         switch (structure->m_transitionTable.size()) {
119             case 0:
120                 ++numberLeaf;
121                 if (!structure->previousID())
122                     ++numberSingletons;
123                 break;
124
125             case 1:
126                 ++numberUsingSingleSlot;
127                 break;
128         }
129
130         if (structure->propertyTable()) {
131             ++numberWithPropertyMaps;
132             totalPropertyMapsSize += structure->propertyTable()->sizeInMemory();
133         }
134     }
135
136     dataLogF("Number of live Structures: %d\n", liveStructureSet.size());
137     dataLogF("Number of Structures using the single item optimization for transition map: %d\n", numberUsingSingleSlot);
138     dataLogF("Number of Structures that are leaf nodes: %d\n", numberLeaf);
139     dataLogF("Number of Structures that singletons: %d\n", numberSingletons);
140     dataLogF("Number of Structures with PropertyMaps: %d\n", numberWithPropertyMaps);
141
142     dataLogF("Size of a single Structures: %d\n", static_cast<unsigned>(sizeof(Structure)));
143     dataLogF("Size of sum of all property maps: %d\n", totalPropertyMapsSize);
144     dataLogF("Size of average of all property maps: %f\n", static_cast<double>(totalPropertyMapsSize) / static_cast<double>(liveStructureSet.size()));
145 #else
146     dataLogF("Dumping Structure statistics is not enabled.\n");
147 #endif
148 }
149
150 Structure::Structure(VM& vm, JSGlobalObject* globalObject, JSValue prototype, const TypeInfo& typeInfo, const ClassInfo* classInfo, IndexingType indexingType, unsigned inlineCapacity)
151     : JSCell(vm, vm.structureStructure.get())
152     , m_blob(vm.heap.structureIDTable().allocateID(this), indexingType, typeInfo)
153     , m_outOfLineTypeFlags(typeInfo.outOfLineTypeFlags())
154     , m_globalObject(vm, this, globalObject, WriteBarrier<JSGlobalObject>::MayBeNull)
155     , m_prototype(vm, this, prototype)
156     , m_classInfo(classInfo)
157     , m_transitionWatchpointSet(IsWatched)
158     , m_offset(invalidOffset)
159     , m_inlineCapacity(inlineCapacity)
160     , m_dictionaryKind(NoneDictionaryKind)
161     , m_hasBeenFlattenedBefore(false)
162     , m_isPinnedPropertyTable(false)
163     , m_hasGetterSetterProperties(classInfo->hasStaticSetterOrReadonlyProperties(vm))
164     , m_hasCustomGetterSetterProperties(false)
165     , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(classInfo->hasStaticSetterOrReadonlyProperties(vm))
166     , m_hasNonEnumerableProperties(false)
167     , m_attributesInPrevious(0)
168     , m_specificFunctionThrashCount(0)
169     , m_preventExtensions(false)
170     , m_didTransition(false)
171     , m_staticFunctionReified(false)
172     , m_hasRareData(false)
173 {
174     ASSERT(inlineCapacity <= JSFinalObject::maxInlineCapacity());
175     ASSERT(static_cast<PropertyOffset>(inlineCapacity) < firstOutOfLineOffset);
176     ASSERT(!m_hasRareData);
177     ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
178     ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
179 }
180
181 const ClassInfo Structure::s_info = { "Structure", 0, 0, 0, CREATE_METHOD_TABLE(Structure) };
182
183 Structure::Structure(VM& vm)
184     : JSCell(CreatingEarlyCell)
185     , m_prototype(vm, this, jsNull())
186     , m_classInfo(info())
187     , m_transitionWatchpointSet(IsWatched)
188     , m_offset(invalidOffset)
189     , m_inlineCapacity(0)
190     , m_dictionaryKind(NoneDictionaryKind)
191     , m_hasBeenFlattenedBefore(false)
192     , m_isPinnedPropertyTable(false)
193     , m_hasGetterSetterProperties(m_classInfo->hasStaticSetterOrReadonlyProperties(vm))
194     , m_hasCustomGetterSetterProperties(false)
195     , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(m_classInfo->hasStaticSetterOrReadonlyProperties(vm))
196     , m_hasNonEnumerableProperties(false)
197     , m_attributesInPrevious(0)
198     , m_specificFunctionThrashCount(0)
199     , m_preventExtensions(false)
200     , m_didTransition(false)
201     , m_staticFunctionReified(false)
202     , m_hasRareData(false)
203 {
204     TypeInfo typeInfo = TypeInfo(CompoundType, OverridesVisitChildren | StructureIsImmortal);
205     m_blob = StructureIDBlob(vm.heap.structureIDTable().allocateID(this), 0, typeInfo);
206     m_outOfLineTypeFlags = typeInfo.outOfLineTypeFlags();
207
208     ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
209     ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
210 }
211
212 Structure::Structure(VM& vm, Structure* previous)
213     : JSCell(vm, vm.structureStructure.get())
214     , m_prototype(vm, this, previous->storedPrototype())
215     , m_classInfo(previous->m_classInfo)
216     , m_transitionWatchpointSet(IsWatched)
217     , m_offset(invalidOffset)
218     , m_inlineCapacity(previous->m_inlineCapacity)
219     , m_dictionaryKind(previous->m_dictionaryKind)
220     , m_hasBeenFlattenedBefore(previous->m_hasBeenFlattenedBefore)
221     , m_isPinnedPropertyTable(false)
222     , m_hasGetterSetterProperties(previous->m_hasGetterSetterProperties)
223     , m_hasCustomGetterSetterProperties(previous->m_hasCustomGetterSetterProperties)
224     , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(previous->m_hasReadOnlyOrGetterSetterPropertiesExcludingProto)
225     , m_hasNonEnumerableProperties(previous->m_hasNonEnumerableProperties)
226     , m_attributesInPrevious(0)
227     , m_specificFunctionThrashCount(previous->m_specificFunctionThrashCount)
228     , m_preventExtensions(previous->m_preventExtensions)
229     , m_didTransition(true)
230     , m_staticFunctionReified(previous->m_staticFunctionReified)
231     , m_hasRareData(false)
232 {
233     TypeInfo typeInfo = previous->typeInfo();
234     m_blob = StructureIDBlob(vm.heap.structureIDTable().allocateID(this), previous->indexingTypeIncludingHistory(), typeInfo);
235     m_outOfLineTypeFlags = typeInfo.outOfLineTypeFlags();
236
237     ASSERT(!previous->typeInfo().structureIsImmortal());
238     if (previous->m_hasRareData && previous->rareData()->needsCloning())
239         cloneRareDataFrom(vm, previous);
240     setPreviousID(vm, previous);
241
242     previous->notifyTransitionFromThisStructure();
243     if (previous->m_globalObject)
244         m_globalObject.set(vm, this, previous->m_globalObject.get());
245     ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
246     ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties(vm));
247 }
248
249 Structure::~Structure()
250 {
251     if (typeInfo().structureIsImmortal())
252         return;
253     Heap::heap(this)->structureIDTable().deallocateID(this, m_blob.structureID());
254 }
255
256 void Structure::destroy(JSCell* cell)
257 {
258     static_cast<Structure*>(cell)->Structure::~Structure();
259 }
260
261 void Structure::findStructuresAndMapForMaterialization(Vector<Structure*, 8>& structures, Structure*& structure, PropertyTable*& table)
262 {
263     ASSERT(structures.isEmpty());
264     table = 0;
265
266     for (structure = this; structure; structure = structure->previousID()) {
267         structure->m_lock.lock();
268         
269         table = structure->propertyTable().get();
270         if (table) {
271             // Leave the structure locked, so that the caller can do things to it atomically
272             // before it loses its property table.
273             return;
274         }
275         
276         structures.append(structure);
277         structure->m_lock.unlock();
278     }
279     
280     ASSERT(!structure);
281     ASSERT(!table);
282 }
283
284 void Structure::materializePropertyMap(VM& vm)
285 {
286     ASSERT(structure()->classInfo() == info());
287     ASSERT(!propertyTable());
288
289     Vector<Structure*, 8> structures;
290     Structure* structure;
291     PropertyTable* table;
292     
293     findStructuresAndMapForMaterialization(structures, structure, table);
294     
295     if (table) {
296         table = table->copy(vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
297         structure->m_lock.unlock();
298     }
299     
300     // Must hold the lock on this structure, since we will be modifying this structure's
301     // property map. We don't want getConcurrently() to see the property map in a half-baked
302     // state.
303     GCSafeConcurrentJITLocker locker(m_lock, vm.heap);
304     if (!table)
305         createPropertyMap(locker, vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
306     else
307         propertyTable().set(vm, this, table);
308
309     for (size_t i = structures.size(); i--;) {
310         structure = structures[i];
311         if (!structure->m_nameInPrevious)
312             continue;
313         PropertyMapEntry entry(vm, this, structure->m_nameInPrevious.get(), structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
314         propertyTable()->add(entry, m_offset, PropertyTable::PropertyOffsetMustNotChange);
315     }
316     
317     checkOffsetConsistency();
318 }
319
320 void Structure::despecifyDictionaryFunction(VM& vm, PropertyName propertyName)
321 {
322     StringImpl* rep = propertyName.uid();
323
324     DeferGC deferGC(vm.heap);
325     materializePropertyMapIfNecessary(vm, deferGC);
326
327     ASSERT(isDictionary());
328     ASSERT(propertyTable());
329
330     PropertyMapEntry* entry = propertyTable()->get(rep);
331     ASSERT(entry);
332     entry->specificValue.clear();
333 }
334
335 Structure* Structure::addPropertyTransitionToExistingStructureImpl(Structure* structure, StringImpl* uid, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
336 {
337     ASSERT(!structure->isDictionary());
338     ASSERT(structure->isObject());
339
340     if (Structure* existingTransition = structure->m_transitionTable.get(uid, attributes)) {
341         JSCell* specificValueInPrevious = existingTransition->m_specificValueInPrevious.get();
342         if (specificValueInPrevious && specificValueInPrevious != specificValue)
343             return 0;
344         validateOffset(existingTransition->m_offset, existingTransition->inlineCapacity());
345         offset = existingTransition->m_offset;
346         return existingTransition;
347     }
348
349     return 0;
350 }
351
352 Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, PropertyName propertyName, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
353 {
354     ASSERT(!isCompilationThread());
355     return addPropertyTransitionToExistingStructureImpl(structure, propertyName.uid(), attributes, specificValue, offset);
356 }
357
358 Structure* Structure::addPropertyTransitionToExistingStructureConcurrently(Structure* structure, StringImpl* uid, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
359 {
360     ConcurrentJITLocker locker(structure->m_lock);
361     return addPropertyTransitionToExistingStructureImpl(structure, uid, attributes, specificValue, offset);
362 }
363
364 bool Structure::anyObjectInChainMayInterceptIndexedAccesses() const
365 {
366     for (const Structure* current = this; ;) {
367         if (current->mayInterceptIndexedAccesses())
368             return true;
369         
370         JSValue prototype = current->storedPrototype();
371         if (prototype.isNull())
372             return false;
373         
374         current = asObject(prototype)->structure();
375     }
376 }
377
378 bool Structure::holesMustForwardToPrototype(VM& vm) const
379 {
380     if (this->mayInterceptIndexedAccesses())
381         return true;
382
383     JSValue prototype = this->storedPrototype();
384     if (!prototype.isObject())
385         return false;
386     JSObject* object = asObject(prototype);
387
388     while (true) {
389         Structure& structure = *object->structure(vm);
390         if (hasIndexedProperties(object->indexingType()) || structure.mayInterceptIndexedAccesses())
391             return true;
392         prototype = structure.storedPrototype();
393         if (!prototype.isObject())
394             return false;
395         object = asObject(prototype);
396     }
397
398     RELEASE_ASSERT_NOT_REACHED();
399     return false;
400 }
401
402 bool Structure::needsSlowPutIndexing() const
403 {
404     return anyObjectInChainMayInterceptIndexedAccesses()
405         || globalObject()->isHavingABadTime();
406 }
407
408 NonPropertyTransition Structure::suggestedArrayStorageTransition() const
409 {
410     if (needsSlowPutIndexing())
411         return AllocateSlowPutArrayStorage;
412     
413     return AllocateArrayStorage;
414 }
415
416 Structure* Structure::addPropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes, JSCell* specificValue, PropertyOffset& offset, PutPropertySlot::Context context)
417 {
418     // If we have a specific function, we may have got to this point if there is
419     // already a transition with the correct property name and attributes, but
420     // specialized to a different function.  In this case we just want to give up
421     // and despecialize the transition.
422     // In this case we clear the value of specificFunction which will result
423     // in us adding a non-specific transition, and any subsequent lookup in
424     // Structure::addPropertyTransitionToExistingStructure will just use that.
425     if (specificValue && structure->m_transitionTable.contains(propertyName.uid(), attributes))
426         specificValue = 0;
427
428     ASSERT(!structure->isDictionary());
429     ASSERT(structure->isObject());
430     ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
431     
432     if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
433         specificValue = 0;
434
435     int maxTransitionLength;
436     if (context == PutPropertySlot::PutById)
437         maxTransitionLength = s_maxTransitionLengthForNonEvalPutById;
438     else
439         maxTransitionLength = s_maxTransitionLength;
440     if (structure->transitionCount() > maxTransitionLength) {
441         Structure* transition = toCacheableDictionaryTransition(vm, structure);
442         ASSERT(structure != transition);
443         offset = transition->putSpecificValue(vm, propertyName, attributes, specificValue);
444         return transition;
445     }
446     
447     Structure* transition = create(vm, structure);
448
449     transition->m_cachedPrototypeChain.setMayBeNull(vm, transition, structure->m_cachedPrototypeChain.get());
450     transition->m_nameInPrevious = propertyName.uid();
451     transition->m_attributesInPrevious = attributes;
452     transition->m_specificValueInPrevious.setMayBeNull(vm, transition, specificValue);
453     transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm));
454     transition->m_offset = structure->m_offset;
455
456     offset = transition->putSpecificValue(vm, propertyName, attributes, specificValue);
457
458     checkOffset(transition->m_offset, transition->inlineCapacity());
459     {
460         ConcurrentJITLocker locker(structure->m_lock);
461         structure->m_transitionTable.add(vm, transition);
462     }
463     transition->checkOffsetConsistency();
464     structure->checkOffsetConsistency();
465     return transition;
466 }
467
468 Structure* Structure::removePropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
469 {
470     ASSERT(!structure->isUncacheableDictionary());
471
472     Structure* transition = toUncacheableDictionaryTransition(vm, structure);
473
474     offset = transition->remove(propertyName);
475
476     transition->checkOffsetConsistency();
477     return transition;
478 }
479
480 Structure* Structure::changePrototypeTransition(VM& vm, Structure* structure, JSValue prototype)
481 {
482     Structure* transition = create(vm, structure);
483
484     transition->m_prototype.set(vm, transition, prototype);
485
486     DeferGC deferGC(vm.heap);
487     structure->materializePropertyMapIfNecessary(vm, deferGC);
488     transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
489     transition->m_offset = structure->m_offset;
490     transition->pin();
491
492     transition->checkOffsetConsistency();
493     return transition;
494 }
495
496 Structure* Structure::despecifyFunctionTransition(VM& vm, Structure* structure, PropertyName replaceFunction)
497 {
498     ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
499     Structure* transition = create(vm, structure);
500
501     ++transition->m_specificFunctionThrashCount;
502
503     DeferGC deferGC(vm.heap);
504     structure->materializePropertyMapIfNecessary(vm, deferGC);
505     transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
506     transition->m_offset = structure->m_offset;
507     transition->pin();
508
509     if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
510         transition->despecifyAllFunctions(vm);
511     else {
512         bool removed = transition->despecifyFunction(vm, replaceFunction);
513         ASSERT_UNUSED(removed, removed);
514     }
515
516     transition->checkOffsetConsistency();
517     return transition;
518 }
519
520 Structure* Structure::attributeChangeTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes)
521 {
522     DeferGC deferGC(vm.heap);
523     if (!structure->isUncacheableDictionary()) {
524         Structure* transition = create(vm, structure);
525
526         structure->materializePropertyMapIfNecessary(vm, deferGC);
527         transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
528         transition->m_offset = structure->m_offset;
529         transition->pin();
530         
531         structure = transition;
532     }
533
534     ASSERT(structure->propertyTable());
535     PropertyMapEntry* entry = structure->propertyTable()->get(propertyName.uid());
536     ASSERT(entry);
537     entry->attributes = attributes;
538
539     structure->checkOffsetConsistency();
540     return structure;
541 }
542
543 Structure* Structure::toDictionaryTransition(VM& vm, Structure* structure, DictionaryKind kind)
544 {
545     ASSERT(!structure->isUncacheableDictionary());
546     
547     Structure* transition = create(vm, structure);
548
549     DeferGC deferGC(vm.heap);
550     structure->materializePropertyMapIfNecessary(vm, deferGC);
551     transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
552     transition->m_offset = structure->m_offset;
553     transition->m_dictionaryKind = kind;
554     transition->pin();
555
556     transition->checkOffsetConsistency();
557     return transition;
558 }
559
560 Structure* Structure::toCacheableDictionaryTransition(VM& vm, Structure* structure)
561 {
562     return toDictionaryTransition(vm, structure, CachedDictionaryKind);
563 }
564
565 Structure* Structure::toUncacheableDictionaryTransition(VM& vm, Structure* structure)
566 {
567     return toDictionaryTransition(vm, structure, UncachedDictionaryKind);
568 }
569
570 // In future we may want to cache this transition.
571 Structure* Structure::sealTransition(VM& vm, Structure* structure)
572 {
573     Structure* transition = preventExtensionsTransition(vm, structure);
574
575     if (transition->propertyTable()) {
576         PropertyTable::iterator end = transition->propertyTable()->end();
577         for (PropertyTable::iterator iter = transition->propertyTable()->begin(); iter != end; ++iter)
578             iter->attributes |= DontDelete;
579     }
580
581     transition->checkOffsetConsistency();
582     return transition;
583 }
584
585 // In future we may want to cache this transition.
586 Structure* Structure::freezeTransition(VM& vm, Structure* structure)
587 {
588     Structure* transition = preventExtensionsTransition(vm, structure);
589
590     if (transition->propertyTable()) {
591         PropertyTable::iterator iter = transition->propertyTable()->begin();
592         PropertyTable::iterator end = transition->propertyTable()->end();
593         if (iter != end)
594             transition->m_hasReadOnlyOrGetterSetterPropertiesExcludingProto = true;
595         for (; iter != end; ++iter)
596             iter->attributes |= iter->attributes & Accessor ? DontDelete : (DontDelete | ReadOnly);
597     }
598
599     ASSERT(transition->hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !transition->classInfo()->hasStaticSetterOrReadonlyProperties(vm));
600     ASSERT(transition->hasGetterSetterProperties() || !transition->classInfo()->hasStaticSetterOrReadonlyProperties(vm));
601     transition->checkOffsetConsistency();
602     return transition;
603 }
604
605 // In future we may want to cache this transition.
606 Structure* Structure::preventExtensionsTransition(VM& vm, Structure* structure)
607 {
608     Structure* transition = create(vm, structure);
609
610     // Don't set m_offset, as one can not transition to this.
611
612     DeferGC deferGC(vm.heap);
613     structure->materializePropertyMapIfNecessary(vm, deferGC);
614     transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
615     transition->m_offset = structure->m_offset;
616     transition->m_preventExtensions = true;
617     transition->pin();
618
619     transition->checkOffsetConsistency();
620     return transition;
621 }
622
623 PropertyTable* Structure::takePropertyTableOrCloneIfPinned(VM& vm)
624 {
625     DeferGC deferGC(vm.heap);
626     materializePropertyMapIfNecessaryForPinning(vm, deferGC);
627     
628     if (m_isPinnedPropertyTable)
629         return propertyTable()->copy(vm, propertyTable()->size() + 1);
630     
631     // Hold the lock while stealing the table - so that getConcurrently() on another thread
632     // will either have to bypass this structure, or will get to use the property table
633     // before it is stolen.
634     ConcurrentJITLocker locker(m_lock);
635     PropertyTable* takenPropertyTable = propertyTable().get();
636     propertyTable().clear();
637     return takenPropertyTable;
638 }
639
640 Structure* Structure::nonPropertyTransition(VM& vm, Structure* structure, NonPropertyTransition transitionKind)
641 {
642     unsigned attributes = toAttributes(transitionKind);
643     IndexingType indexingType = newIndexingType(structure->indexingTypeIncludingHistory(), transitionKind);
644     
645     if (JSGlobalObject* globalObject = structure->m_globalObject.get()) {
646         if (globalObject->isOriginalArrayStructure(structure)) {
647             Structure* result = globalObject->originalArrayStructureForIndexingType(indexingType);
648             if (result->indexingTypeIncludingHistory() == indexingType) {
649                 structure->notifyTransitionFromThisStructure();
650                 return result;
651             }
652         }
653     }
654     
655     Structure* existingTransition;
656     if (!structure->isDictionary() && (existingTransition = structure->m_transitionTable.get(0, attributes))) {
657         ASSERT(existingTransition->m_attributesInPrevious == attributes);
658         ASSERT(existingTransition->indexingTypeIncludingHistory() == indexingType);
659         return existingTransition;
660     }
661     
662     Structure* transition = create(vm, structure);
663     transition->m_attributesInPrevious = attributes;
664     transition->m_blob.setIndexingType(indexingType);
665     transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm));
666     transition->m_offset = structure->m_offset;
667     checkOffset(transition->m_offset, transition->inlineCapacity());
668     
669     if (structure->isDictionary())
670         transition->pin();
671     else {
672         ConcurrentJITLocker locker(structure->m_lock);
673         structure->m_transitionTable.add(vm, transition);
674     }
675     transition->checkOffsetConsistency();
676     return transition;
677 }
678
679 // In future we may want to cache this property.
680 bool Structure::isSealed(VM& vm)
681 {
682     if (isExtensible())
683         return false;
684
685     DeferGC deferGC(vm.heap);
686     materializePropertyMapIfNecessary(vm, deferGC);
687     if (!propertyTable())
688         return true;
689
690     PropertyTable::iterator end = propertyTable()->end();
691     for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
692         if ((iter->attributes & DontDelete) != DontDelete)
693             return false;
694     }
695     return true;
696 }
697
698 // In future we may want to cache this property.
699 bool Structure::isFrozen(VM& vm)
700 {
701     if (isExtensible())
702         return false;
703
704     DeferGC deferGC(vm.heap);
705     materializePropertyMapIfNecessary(vm, deferGC);
706     if (!propertyTable())
707         return true;
708
709     PropertyTable::iterator end = propertyTable()->end();
710     for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
711         if (!(iter->attributes & DontDelete))
712             return false;
713         if (!(iter->attributes & (ReadOnly | Accessor)))
714             return false;
715     }
716     return true;
717 }
718
719 Structure* Structure::flattenDictionaryStructure(VM& vm, JSObject* object)
720 {
721     checkOffsetConsistency();
722     ASSERT(isDictionary());
723
724     size_t beforeOutOfLineCapacity = this->outOfLineCapacity();
725     if (isUncacheableDictionary()) {
726         ASSERT(propertyTable());
727
728         size_t propertyCount = propertyTable()->size();
729
730         // Holds our values compacted by insertion order.
731         Vector<JSValue> values(propertyCount);
732
733         // Copies out our values from their hashed locations, compacting property table offsets as we go.
734         unsigned i = 0;
735         PropertyTable::iterator end = propertyTable()->end();
736         m_offset = invalidOffset;
737         for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter, ++i) {
738             values[i] = object->getDirect(iter->offset);
739             m_offset = iter->offset = offsetForPropertyNumber(i, m_inlineCapacity);
740         }
741         
742         // Copies in our values to their compacted locations.
743         for (unsigned i = 0; i < propertyCount; i++)
744             object->putDirect(vm, offsetForPropertyNumber(i, m_inlineCapacity), values[i]);
745
746         propertyTable()->clearDeletedOffsets();
747         checkOffsetConsistency();
748     }
749
750     m_dictionaryKind = NoneDictionaryKind;
751     m_hasBeenFlattenedBefore = true;
752
753     size_t afterOutOfLineCapacity = this->outOfLineCapacity();
754
755     if (beforeOutOfLineCapacity != afterOutOfLineCapacity) {
756         ASSERT(beforeOutOfLineCapacity > afterOutOfLineCapacity);
757         // If the object had a Butterfly but after flattening/compacting we no longer have need of it,
758         // we need to zero it out because the collector depends on the Structure to know the size for copying.
759         if (object->butterfly() && !afterOutOfLineCapacity && !this->hasIndexingHeader(object))
760             object->setStructureAndButterfly(vm, this, 0);
761         // If the object was down-sized to the point where the base of the Butterfly is no longer within the 
762         // first CopiedBlock::blockSize bytes, we'll get the wrong answer if we try to mask the base back to 
763         // the CopiedBlock header. To prevent this case we need to memmove the Butterfly down.
764         else if (object->butterfly())
765             object->shiftButterflyAfterFlattening(vm, beforeOutOfLineCapacity, afterOutOfLineCapacity);
766     }
767
768     return this;
769 }
770
771 PropertyOffset Structure::addPropertyWithoutTransition(VM& vm, PropertyName propertyName, unsigned attributes, JSCell* specificValue)
772 {
773     ASSERT(!enumerationCache());
774
775     if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
776         specificValue = 0;
777
778     DeferGC deferGC(vm.heap);
779     materializePropertyMapIfNecessaryForPinning(vm, deferGC);
780     
781     pin();
782
783     return putSpecificValue(vm, propertyName, attributes, specificValue);
784 }
785
786 PropertyOffset Structure::removePropertyWithoutTransition(VM& vm, PropertyName propertyName)
787 {
788     ASSERT(isUncacheableDictionary());
789     ASSERT(!enumerationCache());
790
791     DeferGC deferGC(vm.heap);
792     materializePropertyMapIfNecessaryForPinning(vm, deferGC);
793
794     pin();
795     return remove(propertyName);
796 }
797
798 void Structure::pin()
799 {
800     ASSERT(propertyTable());
801     m_isPinnedPropertyTable = true;
802     clearPreviousID();
803     m_nameInPrevious.clear();
804 }
805
806 void Structure::allocateRareData(VM& vm)
807 {
808     ASSERT(!m_hasRareData);
809     StructureRareData* rareData = StructureRareData::create(vm, previous());
810     m_previousOrRareData.set(vm, this, rareData);
811     m_hasRareData = true;
812     ASSERT(m_hasRareData);
813 }
814
815 void Structure::cloneRareDataFrom(VM& vm, const Structure* other)
816 {
817     ASSERT(!m_hasRareData);
818     ASSERT(other->m_hasRareData);
819     StructureRareData* newRareData = StructureRareData::clone(vm, other->rareData());
820     m_previousOrRareData.set(vm, this, newRareData);
821     m_hasRareData = true;
822     ASSERT(m_hasRareData);
823 }
824
825 #if DUMP_PROPERTYMAP_STATS
826
827 PropertyMapHashTableStats* propertyMapHashTableStats = 0;
828
829 struct PropertyMapStatisticsExitLogger {
830     PropertyMapStatisticsExitLogger();
831     ~PropertyMapStatisticsExitLogger();
832 };
833
834 DEFINE_GLOBAL_FOR_LOGGING(PropertyMapStatisticsExitLogger, logger, );
835
836 PropertyMapStatisticsExitLogger::PropertyMapStatisticsExitLogger()
837 {
838     propertyMapHashTableStats = adoptPtr(new PropertyMapHashTableStats()).leakPtr();
839 }
840
841 PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
842 {
843     unsigned finds = propertyMapHashTableStats->numFinds;
844     unsigned collisions = propertyMapHashTableStats->numCollisions;
845     dataLogF("\nJSC::PropertyMap statistics for process %d\n\n", getCurrentProcessID());
846     dataLogF("%d finds\n", finds);
847     dataLogF("%d collisions (%.1f%%)\n", collisions, 100.0 * collisions / finds);
848     dataLogF("%d lookups\n", propertyMapHashTableStats->numLookups.load());
849     dataLogF("%d lookup probings\n", propertyMapHashTableStats->numLookupProbing.load());
850     dataLogF("%d adds\n", propertyMapHashTableStats->numAdds.load());
851     dataLogF("%d removes\n", propertyMapHashTableStats->numRemoves.load());
852     dataLogF("%d rehashes\n", propertyMapHashTableStats->numRehashes.load());
853     dataLogF("%d reinserts\n", propertyMapHashTableStats->numReinserts.load());
854 }
855
856 #endif
857
858 #if !DO_PROPERTYMAP_CONSTENCY_CHECK
859
860 inline void Structure::checkConsistency()
861 {
862     checkOffsetConsistency();
863 }
864
865 #endif
866
867 PropertyTable* Structure::copyPropertyTable(VM& vm)
868 {
869     if (!propertyTable())
870         return 0;
871     return PropertyTable::clone(vm, *propertyTable().get());
872 }
873
874 PropertyTable* Structure::copyPropertyTableForPinning(VM& vm)
875 {
876     if (propertyTable())
877         return PropertyTable::clone(vm, *propertyTable().get());
878     return PropertyTable::create(vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
879 }
880
881 PropertyOffset Structure::getConcurrently(VM&, StringImpl* uid, unsigned& attributes, JSCell*& specificValue)
882 {
883     Vector<Structure*, 8> structures;
884     Structure* structure;
885     PropertyTable* table;
886     
887     findStructuresAndMapForMaterialization(structures, structure, table);
888     
889     if (table) {
890         PropertyMapEntry* entry = table->get(uid);
891         if (entry) {
892             attributes = entry->attributes;
893             specificValue = entry->specificValue.get();
894             PropertyOffset result = entry->offset;
895             structure->m_lock.unlock();
896             return result;
897         }
898         structure->m_lock.unlock();
899     }
900     
901     for (unsigned i = structures.size(); i--;) {
902         structure = structures[i];
903         if (structure->m_nameInPrevious.get() != uid)
904             continue;
905         
906         attributes = structure->m_attributesInPrevious;
907         specificValue = structure->m_specificValueInPrevious.get();
908         return structure->m_offset;
909     }
910     
911     return invalidOffset;
912 }
913
914 bool Structure::despecifyFunction(VM& vm, PropertyName propertyName)
915 {
916     DeferGC deferGC(vm.heap);
917     materializePropertyMapIfNecessary(vm, deferGC);
918     if (!propertyTable())
919         return false;
920
921     PropertyMapEntry* entry = propertyTable()->get(propertyName.uid());
922     if (!entry)
923         return false;
924
925     ASSERT(entry->specificValue);
926     entry->specificValue.clear();
927     return true;
928 }
929
930 void Structure::despecifyAllFunctions(VM& vm)
931 {
932     DeferGC deferGC(vm.heap);
933     materializePropertyMapIfNecessary(vm, deferGC);
934     if (!propertyTable())
935         return;
936
937     PropertyTable::iterator end = propertyTable()->end();
938     for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter)
939         iter->specificValue.clear();
940 }
941
942 PropertyOffset Structure::putSpecificValue(VM& vm, PropertyName propertyName, unsigned attributes, JSCell* specificValue)
943 {
944     GCSafeConcurrentJITLocker locker(m_lock, vm.heap);
945     
946     ASSERT(!JSC::isValidOffset(get(vm, propertyName)));
947
948     checkConsistency();
949     if (attributes & DontEnum)
950         m_hasNonEnumerableProperties = true;
951
952     StringImpl* rep = propertyName.uid();
953
954     if (!propertyTable())
955         createPropertyMap(locker, vm);
956
957     PropertyOffset newOffset = propertyTable()->nextOffset(m_inlineCapacity);
958
959     propertyTable()->add(PropertyMapEntry(vm, propertyTable().get(), rep, newOffset, attributes, specificValue), m_offset, PropertyTable::PropertyOffsetMayChange);
960     
961     checkConsistency();
962     return newOffset;
963 }
964
965 PropertyOffset Structure::remove(PropertyName propertyName)
966 {
967     ConcurrentJITLocker locker(m_lock);
968     
969     checkConsistency();
970
971     StringImpl* rep = propertyName.uid();
972
973     if (!propertyTable())
974         return invalidOffset;
975
976     PropertyTable::find_iterator position = propertyTable()->find(rep);
977     if (!position.first)
978         return invalidOffset;
979
980     PropertyOffset offset = position.first->offset;
981
982     propertyTable()->remove(position);
983     propertyTable()->addDeletedOffset(offset);
984
985     checkConsistency();
986     return offset;
987 }
988
989 void Structure::createPropertyMap(const GCSafeConcurrentJITLocker&, VM& vm, unsigned capacity)
990 {
991     ASSERT(!propertyTable());
992
993     checkConsistency();
994     propertyTable().set(vm, this, PropertyTable::create(vm, capacity));
995 }
996
997 void Structure::getPropertyNamesFromStructure(VM& vm, PropertyNameArray& propertyNames, EnumerationMode mode)
998 {
999     DeferGC deferGC(vm.heap);
1000     materializePropertyMapIfNecessary(vm, deferGC);
1001     if (!propertyTable())
1002         return;
1003
1004     bool knownUnique = !propertyNames.size();
1005
1006     PropertyTable::iterator end = propertyTable()->end();
1007     for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
1008         ASSERT(m_hasNonEnumerableProperties || !(iter->attributes & DontEnum));
1009         if (!iter->key->isEmptyUnique() && (!(iter->attributes & DontEnum) || mode == IncludeDontEnumProperties)) {
1010             if (knownUnique)
1011                 propertyNames.addKnownUnique(iter->key);
1012             else
1013                 propertyNames.add(iter->key);
1014         }
1015     }
1016 }
1017
1018 JSValue Structure::prototypeForLookup(CodeBlock* codeBlock) const
1019 {
1020     return prototypeForLookup(codeBlock->globalObject());
1021 }
1022
1023 void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)
1024 {
1025     Structure* thisObject = jsCast<Structure*>(cell);
1026     ASSERT_GC_OBJECT_INHERITS(thisObject, info());
1027     ASSERT(thisObject->structure()->typeInfo().overridesVisitChildren());
1028
1029     JSCell::visitChildren(thisObject, visitor);
1030     visitor.append(&thisObject->m_globalObject);
1031     if (!thisObject->isObject())
1032         thisObject->m_cachedPrototypeChain.clear();
1033     else {
1034         visitor.append(&thisObject->m_prototype);
1035         visitor.append(&thisObject->m_cachedPrototypeChain);
1036     }
1037     visitor.append(&thisObject->m_previousOrRareData);
1038     visitor.append(&thisObject->m_specificValueInPrevious);
1039
1040     if (thisObject->m_isPinnedPropertyTable) {
1041         ASSERT(thisObject->m_propertyTableUnsafe);
1042         visitor.append(&thisObject->m_propertyTableUnsafe);
1043     } else if (thisObject->m_propertyTableUnsafe)
1044         thisObject->m_propertyTableUnsafe.clear();
1045 }
1046
1047 bool Structure::prototypeChainMayInterceptStoreTo(VM& vm, PropertyName propertyName)
1048 {
1049     unsigned i = propertyName.asIndex();
1050     if (i != PropertyName::NotAnIndex)
1051         return anyObjectInChainMayInterceptIndexedAccesses();
1052     
1053     for (Structure* current = this; ;) {
1054         JSValue prototype = current->storedPrototype();
1055         if (prototype.isNull())
1056             return false;
1057         
1058         current = prototype.asCell()->structure(vm);
1059         
1060         unsigned attributes;
1061         JSCell* specificValue;
1062         PropertyOffset offset = current->get(vm, propertyName, attributes, specificValue);
1063         if (!JSC::isValidOffset(offset))
1064             continue;
1065         
1066         if (attributes & (ReadOnly | Accessor))
1067             return true;
1068         
1069         return false;
1070     }
1071 }
1072
1073 void Structure::dump(PrintStream& out) const
1074 {
1075     out.print(RawPointer(this), ":[", classInfo()->className, ", {");
1076     
1077     Vector<Structure*, 8> structures;
1078     Structure* structure;
1079     PropertyTable* table;
1080     
1081     const_cast<Structure*>(this)->findStructuresAndMapForMaterialization(
1082         structures, structure, table);
1083     
1084     CommaPrinter comma;
1085     
1086     if (table) {
1087         PropertyTable::iterator iter = table->begin();
1088         PropertyTable::iterator end = table->end();
1089         for (; iter != end; ++iter) {
1090             out.print(comma, iter->key, ":", static_cast<int>(iter->offset));
1091             if (iter->specificValue) {
1092                 DumpContext dummyContext;
1093                 out.print("=>", RawPointer(iter->specificValue.get()));
1094             }
1095         }
1096         
1097         structure->m_lock.unlock();
1098     }
1099     
1100     for (unsigned i = structures.size(); i--;) {
1101         Structure* structure = structures[i];
1102         if (!structure->m_nameInPrevious)
1103             continue;
1104         out.print(comma, structure->m_nameInPrevious.get(), ":", static_cast<int>(structure->m_offset));
1105         if (structure->m_specificValueInPrevious) {
1106             DumpContext dummyContext;
1107             out.print("=>", RawPointer(structure->m_specificValueInPrevious.get()));
1108         }
1109     }
1110     
1111     out.print("}, ", IndexingTypeDump(indexingType()));
1112     
1113     if (m_prototype.get().isCell())
1114         out.print(", Proto:", RawPointer(m_prototype.get().asCell()));
1115     
1116     out.print("]");
1117 }
1118
1119 void Structure::dumpInContext(PrintStream& out, DumpContext* context) const
1120 {
1121     if (context)
1122         context->structures.dumpBrief(this, out);
1123     else
1124         dump(out);
1125 }
1126
1127 void Structure::dumpBrief(PrintStream& out, const CString& string) const
1128 {
1129     out.print("%", string, ":", classInfo()->className);
1130 }
1131
1132 void Structure::dumpContextHeader(PrintStream& out)
1133 {
1134     out.print("Structures:");
1135 }
1136
1137 #if DO_PROPERTYMAP_CONSTENCY_CHECK
1138
1139 void PropertyTable::checkConsistency()
1140 {
1141     checkOffsetConsistency();
1142     ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
1143     ASSERT(m_indexMask);
1144     ASSERT(m_indexSize == m_indexMask + 1);
1145     ASSERT(!(m_indexSize & m_indexMask));
1146
1147     ASSERT(m_keyCount <= m_indexSize / 2);
1148     ASSERT(m_keyCount + m_deletedCount <= m_indexSize / 2);
1149     ASSERT(m_deletedCount <= m_indexSize / 4);
1150
1151     unsigned indexCount = 0;
1152     unsigned deletedIndexCount = 0;
1153     for (unsigned a = 0; a != m_indexSize; ++a) {
1154         unsigned entryIndex = m_index[a];
1155         if (entryIndex == PropertyTable::EmptyEntryIndex)
1156             continue;
1157         if (entryIndex == deletedEntryIndex()) {
1158             ++deletedIndexCount;
1159             continue;
1160         }
1161         ASSERT(entryIndex < deletedEntryIndex());
1162         ASSERT(entryIndex - 1 <= usedCount());
1163         ++indexCount;
1164
1165         for (unsigned b = a + 1; b != m_indexSize; ++b)
1166             ASSERT(m_index[b] != entryIndex);
1167     }
1168     ASSERT(indexCount == m_keyCount);
1169     ASSERT(deletedIndexCount == m_deletedCount);
1170
1171     ASSERT(!table()[deletedEntryIndex() - 1].key);
1172
1173     unsigned nonEmptyEntryCount = 0;
1174     for (unsigned c = 0; c < usedCount(); ++c) {
1175         StringImpl* rep = table()[c].key;
1176         if (rep == PROPERTY_MAP_DELETED_ENTRY_KEY)
1177             continue;
1178         ++nonEmptyEntryCount;
1179         unsigned i = rep->existingHash();
1180         unsigned k = 0;
1181         unsigned entryIndex;
1182         while (1) {
1183             entryIndex = m_index[i & m_indexMask];
1184             ASSERT(entryIndex != PropertyTable::EmptyEntryIndex);
1185             if (rep == table()[entryIndex - 1].key)
1186                 break;
1187             if (k == 0)
1188                 k = 1 | doubleHash(rep->existingHash());
1189             i += k;
1190         }
1191         ASSERT(entryIndex == c + 1);
1192     }
1193
1194     ASSERT(nonEmptyEntryCount == m_keyCount);
1195 }
1196
1197 void Structure::checkConsistency()
1198 {
1199     if (!propertyTable())
1200         return;
1201
1202     if (!m_hasNonEnumerableProperties) {
1203         PropertyTable::iterator end = propertyTable()->end();
1204         for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
1205             ASSERT(!(iter->attributes & DontEnum));
1206         }
1207     }
1208
1209     propertyTable()->checkConsistency();
1210 }
1211
1212 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
1213
1214 bool ClassInfo::hasStaticSetterOrReadonlyProperties(VM& vm) const
1215 {
1216     for (const ClassInfo* ci = this; ci; ci = ci->parentClass) {
1217         if (const HashTable* table = ci->propHashTable(vm)) {
1218             if (table->hasSetterOrReadonlyProperties)
1219                 return true;
1220         }
1221     }
1222     return false;
1223 }
1224
1225 } // namespace JSC