Simplify WatchpointSet state tracking
[WebKit-https.git] / Source / JavaScriptCore / runtime / Structure.cpp
index 4083812..7f383d8 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2009, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
 #include "config.h"
 #include "Structure.h"
 
-#include "Identifier.h"
+#include "CodeBlock.h"
+#include "DumpContext.h"
 #include "JSObject.h"
 #include "JSPropertyNameIterator.h"
 #include "Lookup.h"
 #include "PropertyNameArray.h"
 #include "StructureChain.h"
+#include "StructureRareDataInlines.h"
+#include <wtf/CommaPrinter.h>
 #include <wtf/RefCountedLeakCounter.h>
 #include <wtf/RefPtr.h>
-
-#if ENABLE(JSC_MULTIPLE_THREADS)
 #include <wtf/Threading.h>
-#endif
 
 #define DUMP_STRUCTURE_ID_STATISTICS 0
 
@@ -71,7 +71,7 @@ bool StructureTransitionTable::contains(StringImpl* rep, unsigned attributes) co
         Structure* transition = singleTransition();
         return transition && transition->m_nameInPrevious == rep && transition->m_attributesInPrevious == attributes;
     }
-    return map()->contains(make_pair(rep, attributes));
+    return map()->get(make_pair(rep, attributes));
 }
 
 inline Structure* StructureTransitionTable::get(StringImpl* rep, unsigned attributes) const
@@ -83,21 +83,21 @@ inline Structure* StructureTransitionTable::get(StringImpl* rep, unsigned attrib
     return map()->get(make_pair(rep, attributes));
 }
 
-inline void StructureTransitionTable::add(JSGlobalData& globalData, Structure* structure)
+inline void StructureTransitionTable::add(VM& vm, Structure* structure)
 {
     if (isUsingSingleSlot()) {
         Structure* existingTransition = singleTransition();
 
         // This handles the first transition being added.
         if (!existingTransition) {
-            setSingleTransition(globalData, structure);
+            setSingleTransition(vm, structure);
             return;
         }
 
         // This handles the second transition being added
         // (or the first transition being despecified!)
         setMap(new TransitionMap());
-        add(globalData, existingTransition);
+        add(vm, existingTransition);
     }
 
     // Add the structure to the map.
@@ -105,13 +105,7 @@ inline void StructureTransitionTable::add(JSGlobalData& globalData, Structure* s
     // Newer versions of the STL have an std::make_pair function that takes rvalue references.
     // 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.
     // See https://bugs.webkit.org/show_bug.cgi?id=59261 for more details
-    std::pair<TransitionMap::iterator, bool> result = map()->add(globalData, make_pair(structure->m_nameInPrevious, +structure->m_attributesInPrevious), structure);
-    if (!result.second) {
-        // There already is an entry! - we should only hit this when despecifying.
-        ASSERT(result.first.get().second->m_specificValueInPrevious);
-        ASSERT(!structure->m_specificValueInPrevious);
-        map()->set(result.first, structure);
-    }
+    map()->set(make_pair(structure->m_nameInPrevious.get(), +structure->m_attributesInPrevious), structure);
 }
 
 void Structure::dumpStatistics()
@@ -130,7 +124,7 @@ void Structure::dumpStatistics()
         switch (structure->m_transitionTable.size()) {
             case 0:
                 ++numberLeaf;
-               if (!structure->m_previous)
+                if (!structure->previousID())
                     ++numberSingletons;
                 break;
 
@@ -139,171 +133,255 @@ void Structure::dumpStatistics()
                 break;
         }
 
-        if (structure->m_propertyTable) {
+        if (structure->propertyTable()) {
             ++numberWithPropertyMaps;
-            totalPropertyMapsSize += structure->m_propertyTable->sizeInMemory();
+            totalPropertyMapsSize += structure->propertyTable()->sizeInMemory();
         }
     }
 
-    printf("Number of live Structures: %d\n", liveStructureSet.size());
-    printf("Number of Structures using the single item optimization for transition map: %d\n", numberUsingSingleSlot);
-    printf("Number of Structures that are leaf nodes: %d\n", numberLeaf);
-    printf("Number of Structures that singletons: %d\n", numberSingletons);
-    printf("Number of Structures with PropertyMaps: %d\n", numberWithPropertyMaps);
+    dataLogF("Number of live Structures: %d\n", liveStructureSet.size());
+    dataLogF("Number of Structures using the single item optimization for transition map: %d\n", numberUsingSingleSlot);
+    dataLogF("Number of Structures that are leaf nodes: %d\n", numberLeaf);
+    dataLogF("Number of Structures that singletons: %d\n", numberSingletons);
+    dataLogF("Number of Structures with PropertyMaps: %d\n", numberWithPropertyMaps);
 
-    printf("Size of a single Structures: %d\n", static_cast<unsigned>(sizeof(Structure)));
-    printf("Size of sum of all property maps: %d\n", totalPropertyMapsSize);
-    printf("Size of average of all property maps: %f\n", static_cast<double>(totalPropertyMapsSize) / static_cast<double>(liveStructureSet.size()));
+    dataLogF("Size of a single Structures: %d\n", static_cast<unsigned>(sizeof(Structure)));
+    dataLogF("Size of sum of all property maps: %d\n", totalPropertyMapsSize);
+    dataLogF("Size of average of all property maps: %f\n", static_cast<double>(totalPropertyMapsSize) / static_cast<double>(liveStructureSet.size()));
 #else
-    printf("Dumping Structure statistics is not enabled.\n");
+    dataLogF("Dumping Structure statistics is not enabled.\n");
 #endif
 }
 
-Structure::Structure(JSGlobalData& globalData, JSValue prototype, const TypeInfo& typeInfo, unsigned anonymousSlotCount, const ClassInfo* classInfo)
-    : JSCell(globalData, globalData.structureStructure.get())
-    , m_typeInfo(typeInfo)
-    , m_prototype(globalData, this, prototype)
+Structure::Structure(VM& vm, JSGlobalObject* globalObject, JSValue prototype, const TypeInfo& typeInfo, const ClassInfo* classInfo, IndexingType indexingType, unsigned inlineCapacity)
+    : JSCell(vm, vm.structureStructure.get())
+    , m_globalObject(vm, this, globalObject, WriteBarrier<JSGlobalObject>::MayBeNull)
+    , m_prototype(vm, this, prototype)
     , m_classInfo(classInfo)
-    , m_propertyStorageCapacity(typeInfo.isFinal() ? JSFinalObject_inlineStorageCapacity : JSNonFinalObject_inlineStorageCapacity)
-    , m_offset(noOffset)
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
+    , m_typeInfo(typeInfo)
+    , m_indexingType(indexingType)
+    , m_inlineCapacity(inlineCapacity)
     , m_dictionaryKind(NoneDictionaryKind)
     , m_isPinnedPropertyTable(false)
     , m_hasGetterSetterProperties(false)
+    , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(false)
     , m_hasNonEnumerableProperties(false)
     , m_attributesInPrevious(0)
     , m_specificFunctionThrashCount(0)
-    , m_anonymousSlotCount(anonymousSlotCount)
     , m_preventExtensions(false)
     , m_didTransition(false)
+    , m_staticFunctionReified(false)
 {
-    ASSERT(m_prototype);
-    ASSERT(m_prototype.isObject() || m_prototype.isNull());
+    ASSERT(inlineCapacity <= JSFinalObject::maxInlineCapacity());
+    ASSERT(static_cast<PropertyOffset>(inlineCapacity) < firstOutOfLineOffset);
+    ASSERT(!typeInfo.structureHasRareData());
 }
 
-const ClassInfo Structure::s_info = { "Structure", 0, 0, 0 };
+const ClassInfo Structure::s_info = { "Structure", 0, 0, 0, CREATE_METHOD_TABLE(Structure) };
 
-Structure::Structure(JSGlobalData& globalData)
-    : JSCell(globalData, this, CreatingEarlyCell)
+Structure::Structure(VM& vm)
+    : JSCell(CreatingEarlyCell)
+    , m_prototype(vm, this, jsNull())
+    , m_classInfo(info())
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
     , m_typeInfo(CompoundType, OverridesVisitChildren)
-    , m_prototype(globalData, this, jsNull())
-    , m_classInfo(&s_info)
-    , m_propertyStorageCapacity(0)
-    , m_offset(noOffset)
+    , m_indexingType(0)
+    , m_inlineCapacity(0)
     , m_dictionaryKind(NoneDictionaryKind)
     , m_isPinnedPropertyTable(false)
     , m_hasGetterSetterProperties(false)
+    , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(false)
     , m_hasNonEnumerableProperties(false)
     , m_attributesInPrevious(0)
     , m_specificFunctionThrashCount(0)
-    , m_anonymousSlotCount(0)
     , m_preventExtensions(false)
     , m_didTransition(false)
+    , m_staticFunctionReified(false)
 {
-    ASSERT(m_prototype);
-    ASSERT(m_prototype.isNull());
-    ASSERT(!globalData.structureStructure);
 }
 
-Structure::Structure(JSGlobalData& globalData, const Structure* previous)
-    : JSCell(globalData, globalData.structureStructure.get())
-    , m_typeInfo(previous->typeInfo())
-    , m_prototype(globalData, this, previous->storedPrototype())
+Structure::Structure(VM& vm, const Structure* previous)
+    : JSCell(vm, vm.structureStructure.get())
+    , m_prototype(vm, this, previous->storedPrototype())
     , m_classInfo(previous->m_classInfo)
-    , m_propertyStorageCapacity(previous->m_propertyStorageCapacity)
-    , m_offset(noOffset)
-    , m_dictionaryKind(NoneDictionaryKind)
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
+    , m_typeInfo(previous->typeInfo().type(), previous->typeInfo().flags() & ~StructureHasRareData)
+    , m_indexingType(previous->indexingTypeIncludingHistory())
+    , m_inlineCapacity(previous->m_inlineCapacity)
+    , m_dictionaryKind(previous->m_dictionaryKind)
     , m_isPinnedPropertyTable(false)
     , m_hasGetterSetterProperties(previous->m_hasGetterSetterProperties)
+    , m_hasReadOnlyOrGetterSetterPropertiesExcludingProto(previous->m_hasReadOnlyOrGetterSetterPropertiesExcludingProto)
     , m_hasNonEnumerableProperties(previous->m_hasNonEnumerableProperties)
     , m_attributesInPrevious(0)
     , m_specificFunctionThrashCount(previous->m_specificFunctionThrashCount)
-    , m_anonymousSlotCount(previous->anonymousSlotCount())
     , m_preventExtensions(previous->m_preventExtensions)
     , m_didTransition(true)
+    , m_staticFunctionReified(previous->m_staticFunctionReified)
 {
-    ASSERT(m_prototype);
-    ASSERT(m_prototype.isObject() || m_prototype.isNull());
+    if (previous->typeInfo().structureHasRareData() && previous->rareData()->needsCloning())
+        cloneRareDataFrom(vm, previous);
+    else if (previous->previousID())
+        m_previousOrRareData.set(vm, this, previous->previousID());
+
+    previous->notifyTransitionFromThisStructure();
+    if (previous->m_globalObject)
+        m_globalObject.set(vm, this, previous->m_globalObject.get());
 }
 
-Structure::~Structure()
+void Structure::destroy(JSCell* cell)
 {
+    static_cast<Structure*>(cell)->Structure::~Structure();
 }
 
-void Structure::materializePropertyMap(JSGlobalData& globalData)
+void Structure::findStructuresAndMapForMaterialization(Vector<Structure*, 8>& structures, Structure*& structure, PropertyTable*& table)
 {
-    ASSERT(structure()->classInfo() == &s_info);
-    ASSERT(!m_propertyTable);
-
-    Vector<Structure*, 8> structures;
-    structures.append(this);
+    ASSERT(structures.isEmpty());
+    table = 0;
 
-    Structure* structure = this;
-
-    // Search for the last Structure with a property table.
-    while ((structure = structure->previousID())) {
-        if (structure->m_isPinnedPropertyTable) {
-            ASSERT(structure->m_propertyTable);
-            ASSERT(!structure->m_previous);
-
-            m_propertyTable = structure->m_propertyTable->copy(globalData, 0, m_offset + 1);
-            break;
+    for (structure = this; structure; structure = structure->previousID()) {
+        structure->m_lock.lock();
+        
+        table = structure->propertyTable().get();
+        if (table) {
+            // Leave the structure locked, so that the caller can do things to it atomically
+            // before it loses its property table.
+            return;
         }
-
+        
         structures.append(structure);
+        structure->m_lock.unlock();
     }
+    
+    ASSERT(!structure);
+    ASSERT(!table);
+}
 
-    if (!m_propertyTable)
-        createPropertyMap(m_offset + 1);
+void Structure::materializePropertyMap(VM& vm)
+{
+    ASSERT(structure()->classInfo() == info());
+    ASSERT(!propertyTable());
 
-    for (ptrdiff_t i = structures.size() - 2; i >= 0; --i) {
+    Vector<Structure*, 8> structures;
+    Structure* structure;
+    PropertyTable* table;
+    
+    findStructuresAndMapForMaterialization(structures, structure, table);
+    
+    if (table) {
+        table = table->copy(vm, 0, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
+        structure->m_lock.unlock();
+    }
+    
+    // Must hold the lock on this structure, since we will be modifying this structure's
+    // property map. We don't want getConcurrently() to see the property map in a half-baked
+    // state.
+    GCSafeConcurrentJITLocker locker(m_lock, vm.heap);
+    if (!table)
+        createPropertyMap(locker, vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
+    else
+        propertyTable().set(vm, this, table);
+
+    for (size_t i = structures.size(); i--;) {
         structure = structures[i];
-        PropertyMapEntry entry(globalData, this, structure->m_nameInPrevious.get(), m_anonymousSlotCount + structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
-        m_propertyTable->add(entry);
+        if (!structure->m_nameInPrevious)
+            continue;
+        PropertyMapEntry entry(vm, this, structure->m_nameInPrevious.get(), structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
+        propertyTable()->add(entry, m_offset, PropertyTable::PropertyOffsetMustNotChange);
     }
+    
+    checkOffsetConsistency();
 }
 
-void Structure::growPropertyStorageCapacity()
+inline size_t nextOutOfLineStorageCapacity(size_t currentCapacity)
 {
-    if (isUsingInlineStorage())
-        m_propertyStorageCapacity = JSObject::baseExternalStorageCapacity;
-    else
-        m_propertyStorageCapacity *= 2;
+    if (!currentCapacity)
+        return initialOutOfLineCapacity;
+    return currentCapacity * outOfLineGrowthFactor;
 }
 
-void Structure::despecifyDictionaryFunction(JSGlobalData& globalData, const Identifier& propertyName)
+size_t Structure::suggestedNewOutOfLineStorageCapacity()
 {
-    StringImpl* rep = propertyName.impl();
+    return nextOutOfLineStorageCapacity(outOfLineCapacity());
+}
+void Structure::despecifyDictionaryFunction(VM& vm, PropertyName propertyName)
+{
+    StringImpl* rep = propertyName.uid();
 
-    materializePropertyMapIfNecessary(globalData);
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
 
     ASSERT(isDictionary());
-    ASSERT(m_propertyTable);
+    ASSERT(propertyTable());
 
-    PropertyMapEntry* entry = m_propertyTable->find(rep).first;
+    PropertyMapEntry* entry = propertyTable()->find(rep).first;
     ASSERT(entry);
     entry->specificValue.clear();
 }
 
-Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
+Structure* Structure::addPropertyTransitionToExistingStructureImpl(Structure* structure, StringImpl* uid, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
 {
     ASSERT(!structure->isDictionary());
-    ASSERT(structure->typeInfo().type() == ObjectType);
+    ASSERT(structure->isObject());
 
-    if (Structure* existingTransition = structure->m_transitionTable.get(propertyName.impl(), attributes)) {
+    if (Structure* existingTransition = structure->m_transitionTable.get(uid, attributes)) {
         JSCell* specificValueInPrevious = existingTransition->m_specificValueInPrevious.get();
         if (specificValueInPrevious && specificValueInPrevious != specificValue)
             return 0;
-        ASSERT(existingTransition->m_offset != noOffset);
-        offset = existingTransition->m_offset + existingTransition->m_anonymousSlotCount;
-        ASSERT(offset >= structure->m_anonymousSlotCount);
-        ASSERT(structure->m_anonymousSlotCount == existingTransition->m_anonymousSlotCount);
+        validateOffset(existingTransition->m_offset, existingTransition->inlineCapacity());
+        offset = existingTransition->m_offset;
         return existingTransition;
     }
 
     return 0;
 }
 
-Structure* Structure::addPropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
+Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, PropertyName propertyName, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
+{
+    ASSERT(!isCompilationThread());
+    return addPropertyTransitionToExistingStructureImpl(structure, propertyName.uid(), attributes, specificValue, offset);
+}
+
+Structure* Structure::addPropertyTransitionToExistingStructureConcurrently(Structure* structure, StringImpl* uid, unsigned attributes, JSCell* specificValue, PropertyOffset& offset)
+{
+    ConcurrentJITLocker locker(structure->m_lock);
+    return addPropertyTransitionToExistingStructureImpl(structure, uid, attributes, specificValue, offset);
+}
+
+bool Structure::anyObjectInChainMayInterceptIndexedAccesses() const
+{
+    for (const Structure* current = this; ;) {
+        if (current->mayInterceptIndexedAccesses())
+            return true;
+        
+        JSValue prototype = current->storedPrototype();
+        if (prototype.isNull())
+            return false;
+        
+        current = asObject(prototype)->structure();
+    }
+}
+
+bool Structure::needsSlowPutIndexing() const
+{
+    return anyObjectInChainMayInterceptIndexedAccesses()
+        || globalObject()->isHavingABadTime();
+}
+
+NonPropertyTransition Structure::suggestedArrayStorageTransition() const
+{
+    if (needsSlowPutIndexing())
+        return AllocateSlowPutArrayStorage;
+    
+    return AllocateArrayStorage;
+}
+
+Structure* Structure::addPropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes, JSCell* specificValue, PropertyOffset& offset, PutPropertySlot::Context context)
 {
     // If we have a specific function, we may have got to this point if there is
     // already a transition with the correct property name and attributes, but
@@ -312,207 +390,270 @@ Structure* Structure::addPropertyTransition(JSGlobalData& globalData, Structure*
     // In this case we clear the value of specificFunction which will result
     // in us adding a non-specific transition, and any subsequent lookup in
     // Structure::addPropertyTransitionToExistingStructure will just use that.
-    if (specificValue && structure->m_transitionTable.contains(propertyName.impl(), attributes))
+    if (specificValue && structure->m_transitionTable.contains(propertyName.uid(), attributes))
         specificValue = 0;
 
     ASSERT(!structure->isDictionary());
-    ASSERT(structure->typeInfo().type() == ObjectType);
+    ASSERT(structure->isObject());
     ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
     
     if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
         specificValue = 0;
 
-    if (structure->transitionCount() > s_maxTransitionLength) {
-        Structure* transition = toCacheableDictionaryTransition(globalData, structure);
+    int maxTransitionLength;
+    if (context == PutPropertySlot::PutById)
+        maxTransitionLength = s_maxTransitionLengthForNonEvalPutById;
+    else
+        maxTransitionLength = s_maxTransitionLength;
+    if (structure->transitionCount() > maxTransitionLength) {
+        Structure* transition = toCacheableDictionaryTransition(vm, structure);
         ASSERT(structure != transition);
-        offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
-        ASSERT(offset >= structure->m_anonymousSlotCount);
-        ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
-        if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
-            transition->growPropertyStorageCapacity();
+        offset = transition->putSpecificValue(vm, propertyName, attributes, specificValue);
         return transition;
     }
+    
+    Structure* transition = create(vm, structure);
 
-    Structure* transition = create(globalData, structure);
-
-    transition->m_cachedPrototypeChain.setMayBeNull(globalData, transition, structure->m_cachedPrototypeChain.get());
-    transition->m_previous.set(globalData, transition, structure);
-    transition->m_nameInPrevious = propertyName.impl();
+    transition->m_cachedPrototypeChain.setMayBeNull(vm, transition, structure->m_cachedPrototypeChain.get());
+    transition->setPreviousID(vm, transition, structure);
+    transition->m_nameInPrevious = propertyName.uid();
     transition->m_attributesInPrevious = attributes;
-    transition->m_specificValueInPrevious.setMayBeNull(globalData, transition, specificValue);
-
-    if (structure->m_propertyTable) {
-        if (structure->m_isPinnedPropertyTable)
-            transition->m_propertyTable = structure->m_propertyTable->copy(globalData, transition, structure->m_propertyTable->size() + 1);
-        else
-            transition->m_propertyTable = structure->m_propertyTable.release();
-    } else {
-        if (structure->m_previous)
-            transition->materializePropertyMap(globalData);
-        else
-            transition->createPropertyMap();
-    }
+    transition->m_specificValueInPrevious.setMayBeNull(vm, transition, specificValue);
+    transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm, transition));
+    transition->m_offset = structure->m_offset;
 
-    offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
-    ASSERT(offset >= structure->m_anonymousSlotCount);
-    ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
-    if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
-        transition->growPropertyStorageCapacity();
+    offset = transition->putSpecificValue(vm, propertyName, attributes, specificValue);
 
-    transition->m_offset = offset - structure->m_anonymousSlotCount;
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    structure->m_transitionTable.add(globalData, transition);
+    checkOffset(transition->m_offset, transition->inlineCapacity());
+    {
+        ConcurrentJITLocker locker(structure->m_lock);
+        structure->m_transitionTable.add(vm, transition);
+    }
+    transition->checkOffsetConsistency();
+    structure->checkOffsetConsistency();
     return transition;
 }
 
-Structure* Structure::removePropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, size_t& offset)
+Structure* Structure::removePropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
 {
     ASSERT(!structure->isUncacheableDictionary());
 
-    Structure* transition = toUncacheableDictionaryTransition(globalData, structure);
+    Structure* transition = toUncacheableDictionaryTransition(vm, structure);
 
     offset = transition->remove(propertyName);
-    ASSERT(offset >= structure->m_anonymousSlotCount);
-    ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
 
+    transition->checkOffsetConsistency();
     return transition;
 }
 
-Structure* Structure::changePrototypeTransition(JSGlobalData& globalData, Structure* structure, JSValue prototype)
+Structure* Structure::changePrototypeTransition(VM& vm, Structure* structure, JSValue prototype)
 {
-    Structure* transition = create(globalData, structure);
+    Structure* transition = create(vm, structure);
 
-    transition->m_prototype.set(globalData, transition, prototype);
+    transition->m_prototype.set(vm, transition, prototype);
 
-    // Don't set m_offset, as one can not transition to this.
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm, transition));
+    transition->m_offset = structure->m_offset;
+    transition->pin();
 
-    structure->materializePropertyMapIfNecessary(globalData);
-    transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
-    transition->m_isPinnedPropertyTable = true;
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
+    transition->checkOffsetConsistency();
     return transition;
 }
 
-Structure* Structure::despecifyFunctionTransition(JSGlobalData& globalData, Structure* structure, const Identifier& replaceFunction)
+Structure* Structure::despecifyFunctionTransition(VM& vm, Structure* structure, PropertyName replaceFunction)
 {
     ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
-    Structure* transition = create(globalData, structure);
+    Structure* transition = create(vm, structure);
 
     ++transition->m_specificFunctionThrashCount;
 
-    // Don't set m_offset, as one can not transition to this.
-
-    structure->materializePropertyMapIfNecessary(globalData);
-    transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
-    transition->m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm, transition));
+    transition->m_offset = structure->m_offset;
+    transition->pin();
 
     if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
-        transition->despecifyAllFunctions(globalData);
+        transition->despecifyAllFunctions(vm);
     else {
-        bool removed = transition->despecifyFunction(globalData, replaceFunction);
+        bool removed = transition->despecifyFunction(vm, replaceFunction);
         ASSERT_UNUSED(removed, removed);
     }
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
+
+    transition->checkOffsetConsistency();
     return transition;
 }
 
-Structure* Structure::getterSetterTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::attributeChangeTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes)
 {
-    Structure* transition = create(globalData, structure);
+    DeferGC deferGC(vm.heap);
+    if (!structure->isUncacheableDictionary()) {
+        Structure* transition = create(vm, structure);
+
+        structure->materializePropertyMapIfNecessary(vm, deferGC);
+        transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm, transition));
+        transition->m_offset = structure->m_offset;
+        transition->pin();
+        
+        structure = transition;
+    }
 
-    // Don't set m_offset, as one can not transition to this.
+    ASSERT(structure->propertyTable());
+    PropertyMapEntry* entry = structure->propertyTable()->find(propertyName.uid()).first;
+    ASSERT(entry);
+    entry->attributes = attributes;
 
-    structure->materializePropertyMapIfNecessary(globalData);
-    transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
-    transition->m_isPinnedPropertyTable = true;
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    return transition;
+    structure->checkOffsetConsistency();
+    return structure;
 }
 
-Structure* Structure::toDictionaryTransition(JSGlobalData& globalData, Structure* structure, DictionaryKind kind)
+Structure* Structure::toDictionaryTransition(VM& vm, Structure* structure, DictionaryKind kind)
 {
     ASSERT(!structure->isUncacheableDictionary());
     
-    Structure* transition = create(globalData, structure);
+    Structure* transition = create(vm, structure);
 
-    structure->materializePropertyMapIfNecessary(globalData);
-    transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
-    transition->m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm, transition));
+    transition->m_offset = structure->m_offset;
     transition->m_dictionaryKind = kind;
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
+    transition->pin();
+
+    transition->checkOffsetConsistency();
     return transition;
 }
 
-Structure* Structure::toCacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::toCacheableDictionaryTransition(VM& vm, Structure* structure)
 {
-    return toDictionaryTransition(globalData, structure, CachedDictionaryKind);
+    return toDictionaryTransition(vm, structure, CachedDictionaryKind);
 }
 
-Structure* Structure::toUncacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::toUncacheableDictionaryTransition(VM& vm, Structure* structure)
 {
-    return toDictionaryTransition(globalData, structure, UncachedDictionaryKind);
+    return toDictionaryTransition(vm, structure, UncachedDictionaryKind);
 }
 
 // In future we may want to cache this transition.
-Structure* Structure::sealTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::sealTransition(VM& vm, Structure* structure)
 {
-    Structure* transition = preventExtensionsTransition(globalData, structure);
+    Structure* transition = preventExtensionsTransition(vm, structure);
 
-    if (transition->m_propertyTable) {
-        PropertyTable::iterator end = transition->m_propertyTable->end();
-        for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
+    if (transition->propertyTable()) {
+        PropertyTable::iterator end = transition->propertyTable()->end();
+        for (PropertyTable::iterator iter = transition->propertyTable()->begin(); iter != end; ++iter)
             iter->attributes |= DontDelete;
     }
 
+    transition->checkOffsetConsistency();
     return transition;
 }
 
 // In future we may want to cache this transition.
-Structure* Structure::freezeTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::freezeTransition(VM& vm, Structure* structure)
 {
-    Structure* transition = preventExtensionsTransition(globalData, structure);
-
-    if (transition->m_propertyTable) {
-        PropertyTable::iterator end = transition->m_propertyTable->end();
-        for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
-            iter->attributes |= (DontDelete | ReadOnly);
+    Structure* transition = preventExtensionsTransition(vm, structure);
+
+    if (transition->propertyTable()) {
+        PropertyTable::iterator iter = transition->propertyTable()->begin();
+        PropertyTable::iterator end = transition->propertyTable()->end();
+        if (iter != end)
+            transition->m_hasReadOnlyOrGetterSetterPropertiesExcludingProto = true;
+        for (; iter != end; ++iter)
+            iter->attributes |= iter->attributes & Accessor ? DontDelete : (DontDelete | ReadOnly);
     }
 
+    transition->checkOffsetConsistency();
     return transition;
 }
 
 // In future we may want to cache this transition.
-Structure* Structure::preventExtensionsTransition(JSGlobalData& globalData, Structure* structure)
+Structure* Structure::preventExtensionsTransition(VM& vm, Structure* structure)
 {
-    Structure* transition = create(globalData, structure);
+    Structure* transition = create(vm, structure);
 
     // Don't set m_offset, as one can not transition to this.
 
-    structure->materializePropertyMapIfNecessary(globalData);
-    transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
-    transition->m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm, transition));
+    transition->m_offset = structure->m_offset;
     transition->m_preventExtensions = true;
+    transition->pin();
+
+    transition->checkOffsetConsistency();
+    return transition;
+}
+
+PropertyTable* Structure::takePropertyTableOrCloneIfPinned(VM& vm, Structure* owner)
+{
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);
+    
+    if (m_isPinnedPropertyTable)
+        return propertyTable()->copy(vm, owner, propertyTable()->size() + 1);
+    
+    // Hold the lock while stealing the table - so that getConcurrently() on another thread
+    // will either have to bypass this structure, or will get to use the property table
+    // before it is stolen.
+    ConcurrentJITLocker locker(m_lock);
+    PropertyTable* takenPropertyTable = propertyTable().get();
+    propertyTable().clear();
+    return takenPropertyTable;
+}
 
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
+Structure* Structure::nonPropertyTransition(VM& vm, Structure* structure, NonPropertyTransition transitionKind)
+{
+    unsigned attributes = toAttributes(transitionKind);
+    IndexingType indexingType = newIndexingType(structure->indexingTypeIncludingHistory(), transitionKind);
+    
+    if (JSGlobalObject* globalObject = structure->m_globalObject.get()) {
+        if (globalObject->isOriginalArrayStructure(structure)) {
+            Structure* result = globalObject->originalArrayStructureForIndexingType(indexingType);
+            if (result->indexingTypeIncludingHistory() == indexingType) {
+                structure->notifyTransitionFromThisStructure();
+                return result;
+            }
+        }
+    }
+    
+    if (Structure* existingTransition = structure->m_transitionTable.get(0, attributes)) {
+        ASSERT(existingTransition->m_attributesInPrevious == attributes);
+        ASSERT(existingTransition->indexingTypeIncludingHistory() == indexingType);
+        return existingTransition;
+    }
+    
+    Structure* transition = create(vm, structure);
+    transition->setPreviousID(vm, transition, structure);
+    transition->m_attributesInPrevious = attributes;
+    transition->m_indexingType = indexingType;
+    transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm, transition));
+    transition->m_offset = structure->m_offset;
+    checkOffset(transition->m_offset, transition->inlineCapacity());
+    
+    {
+        ConcurrentJITLocker locker(structure->m_lock);
+        structure->m_transitionTable.add(vm, transition);
+    }
+    transition->checkOffsetConsistency();
     return transition;
 }
 
 // In future we may want to cache this property.
-bool Structure::isSealed(JSGlobalData& globalData)
+bool Structure::isSealed(VM& vm)
 {
     if (isExtensible())
         return false;
 
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
         return true;
 
-    PropertyTable::iterator end = m_propertyTable->end();
-    for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
         if ((iter->attributes & DontDelete) != DontDelete)
             return false;
     }
@@ -520,81 +661,114 @@ bool Structure::isSealed(JSGlobalData& globalData)
 }
 
 // In future we may want to cache this property.
-bool Structure::isFrozen(JSGlobalData& globalData)
+bool Structure::isFrozen(VM& vm)
 {
     if (isExtensible())
         return false;
 
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
         return true;
 
-    PropertyTable::iterator end = m_propertyTable->end();
-    for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
-        if ((iter->attributes & (DontDelete | ReadOnly)) != (DontDelete | ReadOnly))
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
+        if (!(iter->attributes & DontDelete))
+            return false;
+        if (!(iter->attributes & (ReadOnly | Accessor)))
             return false;
     }
     return true;
 }
 
-Structure* Structure::flattenDictionaryStructure(JSGlobalData& globalData, JSObject* object)
+Structure* Structure::flattenDictionaryStructure(VM& vm, JSObject* object)
 {
+    checkOffsetConsistency();
     ASSERT(isDictionary());
     if (isUncacheableDictionary()) {
-        ASSERT(m_propertyTable);
+        ASSERT(propertyTable());
+
+        size_t propertyCount = propertyTable()->size();
 
-        unsigned anonymousSlotCount = m_anonymousSlotCount;
-        size_t propertyCount = m_propertyTable->size();
+        // Holds our values compacted by insertion order.
         Vector<JSValue> values(propertyCount);
 
+        // Copies out our values from their hashed locations, compacting property table offsets as we go.
         unsigned i = 0;
-        PropertyTable::iterator end = m_propertyTable->end();
-        for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter, ++i) {
-            values[i] = object->getDirectOffset(iter->offset);
-            // Update property table to have the new property offsets
-            iter->offset = anonymousSlotCount + i;
+        PropertyTable::iterator end = propertyTable()->end();
+        m_offset = invalidOffset;
+        for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter, ++i) {
+            values[i] = object->getDirect(iter->offset);
+            m_offset = iter->offset = offsetForPropertyNumber(i, m_inlineCapacity);
         }
         
-        // Copy the original property values into their final locations
+        // Copies in our values to their compacted locations.
         for (unsigned i = 0; i < propertyCount; i++)
-            object->putDirectOffset(globalData, anonymousSlotCount + i, values[i]);
+            object->putDirect(vm, offsetForPropertyNumber(i, m_inlineCapacity), values[i]);
 
-        m_propertyTable->clearDeletedOffsets();
+        propertyTable()->clearDeletedOffsets();
+        checkOffsetConsistency();
     }
 
     m_dictionaryKind = NoneDictionaryKind;
+
+    // If the object had a Butterfly but after flattening/compacting we no longer have need of it,
+    // we need to zero it out because the collector depends on the Structure to know the size for copying.
+    if (object->butterfly() && !this->outOfLineCapacity() && !this->hasIndexingHeader(object))
+        object->setStructureAndButterfly(vm, this, 0);
+
     return this;
 }
 
-size_t Structure::addPropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
+PropertyOffset Structure::addPropertyWithoutTransition(VM& vm, PropertyName propertyName, unsigned attributes, JSCell* specificValue)
 {
-    ASSERT(!m_enumerationCache);
+    ASSERT(!enumerationCache());
 
     if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
         specificValue = 0;
 
-    materializePropertyMapIfNecessary(globalData);
-
-    m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);
+    
+    pin();
 
-    size_t offset = putSpecificValue(globalData, propertyName, attributes, specificValue);
-    ASSERT(offset >= m_anonymousSlotCount);
-    if (propertyStorageSize() > propertyStorageCapacity())
-        growPropertyStorageCapacity();
-    return offset;
+    return putSpecificValue(vm, propertyName, attributes, specificValue);
 }
 
-size_t Structure::removePropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName)
+PropertyOffset Structure::removePropertyWithoutTransition(VM& vm, PropertyName propertyName)
 {
     ASSERT(isUncacheableDictionary());
-    ASSERT(!m_enumerationCache);
+    ASSERT(!enumerationCache());
 
-    materializePropertyMapIfNecessary(globalData);
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);
 
+    pin();
+    return remove(propertyName);
+}
+
+void Structure::pin()
+{
+    ASSERT(propertyTable());
     m_isPinnedPropertyTable = true;
-    size_t offset = remove(propertyName);
-    ASSERT(offset >= m_anonymousSlotCount);
-    return offset;
+    clearPreviousID();
+    m_nameInPrevious.clear();
+}
+
+void Structure::allocateRareData(VM& vm)
+{
+    ASSERT(!typeInfo().structureHasRareData());
+    StructureRareData* rareData = StructureRareData::create(vm, previous());
+    m_typeInfo = TypeInfo(typeInfo().type(), typeInfo().flags() | StructureHasRareData);
+    m_previousOrRareData.set(vm, this, rareData);
+}
+
+void Structure::cloneRareDataFrom(VM& vm, const Structure* other)
+{
+    ASSERT(other->typeInfo().structureHasRareData());
+    StructureRareData* newRareData = StructureRareData::clone(vm, other->rareData());
+    m_typeInfo = TypeInfo(typeInfo().type(), typeInfo().flags() | StructureHasRareData);
+    m_previousOrRareData.set(vm, this, newRareData);
 }
 
 #if DUMP_PROPERTYMAP_STATS
@@ -607,11 +781,11 @@ static PropertyMapStatisticsExitLogger logger;
 
 PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
 {
-    printf("\nJSC::PropertyMap statistics\n\n");
-    printf("%d probes\n", numProbes);
-    printf("%d collisions (%.1f%%)\n", numCollisions, 100.0 * numCollisions / numProbes);
-    printf("%d rehashes\n", numRehashes);
-    printf("%d removes\n", numRemoves);
+    dataLogF("\nJSC::PropertyMap statistics\n\n");
+    dataLogF("%d probes\n", numProbes);
+    dataLogF("%d collisions (%.1f%%)\n", numCollisions, 100.0 * numCollisions / numProbes);
+    dataLogF("%d rehashes\n", numRehashes);
+    dataLogF("%d removes\n", numRemoves);
 }
 
 #endif
@@ -620,39 +794,85 @@ PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
 
 inline void Structure::checkConsistency()
 {
+    checkOffsetConsistency();
 }
 
 #endif
 
-PassOwnPtr<PropertyTable> Structure::copyPropertyTable(JSGlobalData& globalData, Structure* owner)
+PropertyTable* Structure::copyPropertyTable(VM& vm, Structure* owner)
+{
+    if (!propertyTable())
+        return 0;
+    return PropertyTable::clone(vm, owner, *propertyTable().get());
+}
+
+PropertyTable* Structure::copyPropertyTableForPinning(VM& vm, Structure* owner)
+{
+    if (propertyTable())
+        return PropertyTable::clone(vm, owner, *propertyTable().get());
+    return PropertyTable::create(vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
+}
+
+PropertyOffset Structure::getConcurrently(VM&, StringImpl* uid, unsigned& attributes, JSCell*& specificValue)
 {
-    return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : 0);
+    Vector<Structure*, 8> structures;
+    Structure* structure;
+    PropertyTable* table;
+    
+    findStructuresAndMapForMaterialization(structures, structure, table);
+    
+    if (table) {
+        PropertyMapEntry* entry = table->find(uid).first;
+        if (entry) {
+            attributes = entry->attributes;
+            specificValue = entry->specificValue.get();
+            PropertyOffset result = entry->offset;
+            structure->m_lock.unlock();
+            return result;
+        }
+        structure->m_lock.unlock();
+    }
+    
+    for (unsigned i = structures.size(); i--;) {
+        structure = structures[i];
+        if (structure->m_nameInPrevious.get() != uid)
+            continue;
+        
+        attributes = structure->m_attributesInPrevious;
+        specificValue = structure->m_specificValueInPrevious.get();
+        return structure->m_offset;
+    }
+    
+    return invalidOffset;
 }
 
-size_t Structure::get(JSGlobalData& globalData, StringImpl* propertyName, unsigned& attributes, JSCell*& specificValue)
+PropertyOffset Structure::get(VM& vm, PropertyName propertyName, unsigned& attributes, JSCell*& specificValue)
 {
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
-        return WTF::notFound;
+    ASSERT(!isCompilationThread());
+    ASSERT(structure()->classInfo() == info());
+
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
+        return invalidOffset;
 
-    PropertyMapEntry* entry = m_propertyTable->find(propertyName).first;
+    PropertyMapEntry* entry = propertyTable()->find(propertyName.uid()).first;
     if (!entry)
-        return WTF::notFound;
+        return invalidOffset;
 
     attributes = entry->attributes;
     specificValue = entry->specificValue.get();
-    ASSERT(entry->offset >= m_anonymousSlotCount);
     return entry->offset;
 }
 
-bool Structure::despecifyFunction(JSGlobalData& globalData, const Identifier& propertyName)
+bool Structure::despecifyFunction(VM& vm, PropertyName propertyName)
 {
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
         return false;
 
-    ASSERT(!propertyName.isNull());
-    PropertyMapEntry* entry = m_propertyTable->find(propertyName.impl()).first;
+    PropertyMapEntry* entry = propertyTable()->find(propertyName.uid()).first;
     if (!entry)
         return false;
 
@@ -661,91 +881,86 @@ bool Structure::despecifyFunction(JSGlobalData& globalData, const Identifier& pr
     return true;
 }
 
-void Structure::despecifyAllFunctions(JSGlobalData& globalData)
+void Structure::despecifyAllFunctions(VM& vm)
 {
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
         return;
 
-    PropertyTable::iterator end = m_propertyTable->end();
-    for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter)
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter)
         iter->specificValue.clear();
 }
 
-size_t Structure::putSpecificValue(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
+PropertyOffset Structure::putSpecificValue(VM& vm, PropertyName propertyName, unsigned attributes, JSCell* specificValue)
 {
-    ASSERT(!propertyName.isNull());
-    ASSERT(get(globalData, propertyName) == notFound);
+    GCSafeConcurrentJITLocker locker(m_lock, vm.heap);
+    
+    ASSERT(!JSC::isValidOffset(get(vm, propertyName)));
 
     checkConsistency();
     if (attributes & DontEnum)
         m_hasNonEnumerableProperties = true;
 
-    StringImpl* rep = propertyName.impl();
-
-    if (!m_propertyTable)
-        createPropertyMap();
+    StringImpl* rep = propertyName.uid();
 
-    unsigned newOffset;
+    if (!propertyTable())
+        createPropertyMap(locker, vm);
 
-    if (m_propertyTable->hasDeletedOffset())
-        newOffset = m_propertyTable->getDeletedOffset();
-    else
-        newOffset = m_propertyTable->size() + m_anonymousSlotCount;
-    ASSERT(newOffset >= m_anonymousSlotCount);
-
-    m_propertyTable->add(PropertyMapEntry(globalData, this, rep, newOffset, attributes, specificValue));
+    PropertyOffset newOffset = propertyTable()->nextOffset(m_inlineCapacity);
 
+    propertyTable()->add(PropertyMapEntry(vm, this, rep, newOffset, attributes, specificValue), m_offset, PropertyTable::PropertyOffsetMayChange);
+    
     checkConsistency();
     return newOffset;
 }
 
-size_t Structure::remove(const Identifier& propertyName)
+PropertyOffset Structure::remove(PropertyName propertyName)
 {
-    ASSERT(!propertyName.isNull());
-
+    ConcurrentJITLocker locker(m_lock);
+    
     checkConsistency();
 
-    StringImpl* rep = propertyName.impl();
+    StringImpl* rep = propertyName.uid();
 
-    if (!m_propertyTable)
-        return notFound;
+    if (!propertyTable())
+        return invalidOffset;
 
-    PropertyTable::find_iterator position = m_propertyTable->find(rep);
+    PropertyTable::find_iterator position = propertyTable()->find(rep);
     if (!position.first)
-        return notFound;
+        return invalidOffset;
 
-    size_t offset = position.first->offset;
-    ASSERT(offset >= m_anonymousSlotCount);
+    PropertyOffset offset = position.first->offset;
 
-    m_propertyTable->remove(position);
-    m_propertyTable->addDeletedOffset(offset);
+    propertyTable()->remove(position);
+    propertyTable()->addDeletedOffset(offset);
 
     checkConsistency();
     return offset;
 }
 
-void Structure::createPropertyMap(unsigned capacity)
+void Structure::createPropertyMap(const GCSafeConcurrentJITLocker&, VM& vm, unsigned capacity)
 {
-    ASSERT(!m_propertyTable);
+    ASSERT(!propertyTable());
 
     checkConsistency();
-    m_propertyTable = adoptPtr(new PropertyTable(capacity));
-    checkConsistency();
+    propertyTable().set(vm, this, PropertyTable::create(vm, capacity));
 }
 
-void Structure::getPropertyNames(JSGlobalData& globalData, PropertyNameArray& propertyNames, EnumerationMode mode)
+void Structure::getPropertyNamesFromStructure(VM& vm, PropertyNameArray& propertyNames, EnumerationMode mode)
 {
-    materializePropertyMapIfNecessary(globalData);
-    if (!m_propertyTable)
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
         return;
 
     bool knownUnique = !propertyNames.size();
 
-    PropertyTable::iterator end = m_propertyTable->end();
-    for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
         ASSERT(m_hasNonEnumerableProperties || !(iter->attributes & DontEnum));
-        if (!(iter->attributes & DontEnum) || (mode == IncludeDontEnumProperties)) {
+        if (iter->key->isIdentifier() && (!(iter->attributes & DontEnum) || mode == IncludeDontEnumProperties)) {
             if (knownUnique)
                 propertyNames.addKnownUnique(iter->key);
             else
@@ -754,34 +969,121 @@ void Structure::getPropertyNames(JSGlobalData& globalData, PropertyNameArray& pr
     }
 }
 
-void Structure::visitChildren(SlotVisitor& visitor)
-{
-    ASSERT_GC_OBJECT_INHERITS(this, &s_info);
-    ASSERT(structure()->typeInfo().overridesVisitChildren());
-    JSCell::visitChildren(visitor);
-    if (m_prototype)
-        visitor.append(&m_prototype);
-    if (m_cachedPrototypeChain)
-        visitor.append(&m_cachedPrototypeChain);
-    if (m_previous)
-        visitor.append(&m_previous);
-    if (m_specificValueInPrevious)
-        visitor.append(&m_specificValueInPrevious);
-    if (m_enumerationCache)
-        visitor.append(&m_enumerationCache);
-    if (m_propertyTable) {
-        PropertyTable::iterator end = m_propertyTable->end();
-        for (PropertyTable::iterator ptr = m_propertyTable->begin(); ptr != end; ++ptr) {
-            if (ptr->specificValue)
-                visitor.append(&ptr->specificValue);
-        }
+JSValue Structure::prototypeForLookup(CodeBlock* codeBlock) const
+{
+    return prototypeForLookup(codeBlock->globalObject());
+}
+
+void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)
+{
+    Structure* thisObject = jsCast<Structure*>(cell);
+    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
+    ASSERT(thisObject->structure()->typeInfo().overridesVisitChildren());
+
+    JSCell::visitChildren(thisObject, visitor);
+    visitor.append(&thisObject->m_globalObject);
+    if (!thisObject->isObject())
+        thisObject->m_cachedPrototypeChain.clear();
+    else {
+        visitor.append(&thisObject->m_prototype);
+        visitor.append(&thisObject->m_cachedPrototypeChain);
+    }
+    visitor.append(&thisObject->m_previousOrRareData);
+    visitor.append(&thisObject->m_specificValueInPrevious);
+
+    if (thisObject->m_isPinnedPropertyTable) {
+        ASSERT(thisObject->m_propertyTableUnsafe);
+        visitor.append(&thisObject->m_propertyTableUnsafe);
+    } else if (thisObject->m_propertyTableUnsafe)
+        thisObject->m_propertyTableUnsafe.clear();
+}
+
+bool Structure::prototypeChainMayInterceptStoreTo(VM& vm, PropertyName propertyName)
+{
+    unsigned i = propertyName.asIndex();
+    if (i != PropertyName::NotAnIndex)
+        return anyObjectInChainMayInterceptIndexedAccesses();
+    
+    for (Structure* current = this; ;) {
+        JSValue prototype = current->storedPrototype();
+        if (prototype.isNull())
+            return false;
+        
+        current = prototype.asCell()->structure();
+        
+        unsigned attributes;
+        JSCell* specificValue;
+        PropertyOffset offset = current->get(vm, propertyName, attributes, specificValue);
+        if (!JSC::isValidOffset(offset))
+            continue;
+        
+        if (attributes & (ReadOnly | Accessor))
+            return true;
+        
+        return false;
+    }
+}
+
+void Structure::dump(PrintStream& out) const
+{
+    out.print(RawPointer(this), ":[", classInfo()->className, ", {");
+    
+    Vector<Structure*, 8> structures;
+    Structure* structure;
+    PropertyTable* table;
+    
+    const_cast<Structure*>(this)->findStructuresAndMapForMaterialization(
+        structures, structure, table);
+    
+    CommaPrinter comma;
+    
+    if (table) {
+        PropertyTable::iterator iter = table->begin();
+        PropertyTable::iterator end = table->end();
+        for (; iter != end; ++iter)
+            out.print(comma, iter->key, ":", static_cast<int>(iter->offset));
+        
+        structure->m_lock.unlock();
     }
+    
+    for (unsigned i = structures.size(); i--;) {
+        Structure* structure = structures[i];
+        if (!structure->m_nameInPrevious)
+            continue;
+        out.print(comma, structure->m_nameInPrevious.get(), ":", static_cast<int>(structure->m_offset));
+    }
+    
+    out.print("}, ", IndexingTypeDump(indexingType()));
+    
+    if (m_prototype.get().isCell())
+        out.print(", Proto:", RawPointer(m_prototype.get().asCell()));
+    
+    out.print("]");
+}
+
+void Structure::dumpInContext(PrintStream& out, DumpContext* context) const
+{
+    if (context)
+        context->structures.dumpBrief(this, out);
+    else
+        dump(out);
+}
+
+void Structure::dumpBrief(PrintStream& out, const CString& string) const
+{
+    out.print("%", string, ":", classInfo()->className);
+}
+
+void Structure::dumpContextHeader(PrintStream& out)
+{
+    out.print("Structures:");
 }
 
 #if DO_PROPERTYMAP_CONSTENCY_CHECK
 
 void PropertyTable::checkConsistency()
 {
+    checkOffsetConsistency();
     ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
     ASSERT(m_indexMask);
     ASSERT(m_indexSize == m_indexMask + 1);
@@ -839,18 +1141,17 @@ void PropertyTable::checkConsistency()
 
 void Structure::checkConsistency()
 {
-    if (!m_propertyTable)
+    if (!propertyTable())
         return;
 
     if (!m_hasNonEnumerableProperties) {
-        PropertyTable::iterator end = m_propertyTable->end();
-        for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
+        PropertyTable::iterator end = propertyTable()->end();
+        for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
             ASSERT(!(iter->attributes & DontEnum));
-            ASSERT(iter->offset >= m_anonymousSlotCount);
         }
     }
 
-    m_propertyTable->checkConsistency();
+    propertyTable()->checkConsistency();
 }
 
 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK