JavaScriptCore-7601.1.46.3.tar.gz

[apple/javascriptcore.git] / runtime / Structure.cpp

diff --git a/runtime/Structure.cpp b/runtime/Structure.cpp
index 6d13f4b98af3d42ae06c24e28633c066085e6427..3985805cf55c83c1da654a135c4510c750170b19 100644 (file)
--- a/runtime/Structure.cpp
+++ b/runtime/Structure.cpp
@@ -1,5 +1,5 @@
 /*
 /*

- * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2009, 2013, 2014 Apple Inc. All rights reserved.

  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions


@@ -10,10 +10,10 @@
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *

- * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY

  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR

  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR


@@ -26,18 +26,22 @@
 #include "config.h"
 #include "Structure.h"
 
 #include "config.h"
 #include "Structure.h"
 

-#include "Identifier.h"
+#include "CodeBlock.h"
+#include "DumpContext.h"
+#include "JSCInlines.h"

 #include "JSObject.h"
 #include "JSObject.h"

-#include "JSPropertyNameIterator.h"
+#include "JSPropertyNameEnumerator.h"

 #include "Lookup.h"
 #include "Lookup.h"

+#include "PropertyMapHashTable.h"

 #include "PropertyNameArray.h"
 #include "StructureChain.h"
 #include "PropertyNameArray.h"
 #include "StructureChain.h"

+#include "StructureRareDataInlines.h"
+#include "WeakGCMapInlines.h"
+#include <wtf/CommaPrinter.h>
+#include <wtf/ProcessID.h>

 #include <wtf/RefCountedLeakCounter.h>
 #include <wtf/RefPtr.h>
 #include <wtf/RefCountedLeakCounter.h>
 #include <wtf/RefPtr.h>

-
-#if ENABLE(JSC_MULTIPLE_THREADS)

 #include <wtf/Threading.h>
 #include <wtf/Threading.h>

-#endif

 
 #define DUMP_STRUCTURE_ID_STATISTICS 0
 
 
 #define DUMP_STRUCTURE_ID_STATISTICS 0
 


@@ -52,131 +56,51 @@ using namespace WTF;
 
 namespace JSC {
 
 
 namespace JSC {
 

-// Choose a number for the following so that most property maps are smaller,
-// but it's not going to blow out the stack to allocate this number of pointers.
-static const int smallMapThreshold = 1024;
-
-// The point at which the function call overhead of the qsort implementation
-// becomes small compared to the inefficiency of insertion sort.
-static const unsigned tinyMapThreshold = 20;
-
-static const unsigned newTableSize = 16;
-
-#ifndef NDEBUG
-static WTF::RefCountedLeakCounter structureCounter("Structure");
-
-#if ENABLE(JSC_MULTIPLE_THREADS)
-static Mutex& ignoreSetMutex = *(new Mutex);
-#endif
-
-static bool shouldIgnoreLeaks;
-static HashSet<Structure*>& ignoreSet = *(new HashSet<Structure*>);
-#endif
-

 #if DUMP_STRUCTURE_ID_STATISTICS
 static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
 #endif
 
 #if DUMP_STRUCTURE_ID_STATISTICS
 static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
 #endif
 

-static int comparePropertyMapEntryIndices(const void* a, const void* b);
-
-inline void Structure::setTransitionTable(TransitionTable* table)
-{
-    ASSERT(m_isUsingSingleSlot);
-#ifndef NDEBUG
-    setSingleTransition(0);
-#endif
-    m_isUsingSingleSlot = false;
-    m_transitions.m_table = table;
-    // This implicitly clears the flag that indicates we're using a single transition
-    ASSERT(!m_isUsingSingleSlot);
-}
-
-// The contains and get methods accept imprecise matches, so if an unspecialised transition exists
-// for the given key they will consider that transition to be a match.  If a specialised transition
-// exists and it matches the provided specificValue, get will return the specific transition.
-inline bool Structure::transitionTableContains(const StructureTransitionTableHash::Key& key, JSCell* specificValue)
+bool StructureTransitionTable::contains(UniquedStringImpl* rep, unsigned attributes) const

 {
 {

-    if (m_isUsingSingleSlot) {
-        Structure* existingTransition = singleTransition();
-        return existingTransition && existingTransition->m_nameInPrevious.get() == key.first
-               && existingTransition->m_attributesInPrevious == key.second
-               && (existingTransition->m_specificValueInPrevious == specificValue || existingTransition->m_specificValueInPrevious == 0);
-    }
-    TransitionTable::iterator find = transitionTable()->find(key);
-    if (find == transitionTable()->end())
-        return false;
-
-    return find->second.first || find->second.second->transitionedFor(specificValue);
-}
-
-inline Structure* Structure::transitionTableGet(const StructureTransitionTableHash::Key& key, JSCell* specificValue) const
-{
-    if (m_isUsingSingleSlot) {
-        Structure* existingTransition = singleTransition();
-        if (existingTransition && existingTransition->m_nameInPrevious.get() == key.first
-            && existingTransition->m_attributesInPrevious == key.second
-            && (existingTransition->m_specificValueInPrevious == specificValue || existingTransition->m_specificValueInPrevious == 0))
-            return existingTransition;
-        return 0;
+    if (isUsingSingleSlot()) {
+        Structure* transition = singleTransition();
+        return transition && transition->m_nameInPrevious == rep && transition->attributesInPrevious() == attributes;

     }
     }

-
-    Transition transition = transitionTable()->get(key);
-    if (transition.second && transition.second->transitionedFor(specificValue))
-        return transition.second;
-    return transition.first;
+    return map()->get(std::make_pair(rep, attributes));

 }
 
 }
 

-inline bool Structure::transitionTableHasTransition(const StructureTransitionTableHash::Key& key) const
+Structure* StructureTransitionTable::get(UniquedStringImpl* rep, unsigned attributes) const

 {
 {

-    if (m_isUsingSingleSlot) {
+    if (isUsingSingleSlot()) {

         Structure* transition = singleTransition();
         Structure* transition = singleTransition();

-        return transition && transition->m_nameInPrevious == key.first
-        && transition->m_attributesInPrevious == key.second;
+        return (transition && transition->m_nameInPrevious == rep && transition->attributesInPrevious() == attributes) ? transition : 0;

     }
     }

-    return transitionTable()->contains(key);
+    return map()->get(std::make_pair(rep, attributes));

 }
 
 }
 

-inline void Structure::transitionTableRemove(const StructureTransitionTableHash::Key& key, JSCell* specificValue)
+void StructureTransitionTable::add(VM& vm, Structure* structure)

 {
 {

-    if (m_isUsingSingleSlot) {
-        ASSERT(transitionTableContains(key, specificValue));
-        setSingleTransition(0);
-        return;
-    }
-    TransitionTable::iterator find = transitionTable()->find(key);
-    if (!specificValue)
-        find->second.first = 0;
-    else
-        find->second.second = 0;
-    if (!find->second.first && !find->second.second)
-        transitionTable()->remove(find);
-}
+    if (isUsingSingleSlot()) {
+        Structure* existingTransition = singleTransition();

 
 

-inline void Structure::transitionTableAdd(const StructureTransitionTableHash::Key& key, Structure* structure, JSCell* specificValue)
-{
-    if (m_isUsingSingleSlot) {
-        if (!singleTransition()) {
-            setSingleTransition(structure);
+        // This handles the first transition being added.
+        if (!existingTransition) {
+            setSingleTransition(vm, structure);

             return;
         }
             return;
         }

-        Structure* existingTransition = singleTransition();
-        TransitionTable* transitionTable = new TransitionTable;
-        setTransitionTable(transitionTable);
-        if (existingTransition)
-            transitionTableAdd(std::make_pair(existingTransition->m_nameInPrevious.get(), existingTransition->m_attributesInPrevious), existingTransition, existingTransition->m_specificValueInPrevious);
-    }
-    if (!specificValue) {
-        TransitionTable::iterator find = transitionTable()->find(key);
-        if (find == transitionTable()->end())
-            transitionTable()->add(key, Transition(structure, static_cast<Structure*>(0)));
-        else
-            find->second.first = structure;
-    } else {
-        // If we're adding a transition to a specific value, then there cannot be
-        // an existing transition
-        ASSERT(!transitionTable()->contains(key));
-        transitionTable()->add(key, Transition(static_cast<Structure*>(0), structure));
+
+        // This handles the second transition being added
+        // (or the first transition being despecified!)
+        setMap(new TransitionMap(vm));
+        add(vm, existingTransition);

     }
     }

+
+    // Add the structure to the map.
+
+    // 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
+    map()->set(std::make_pair(structure->m_nameInPrevious.get(), +structure->attributesInPrevious()), structure);

 }
 
 void Structure::dumpStatistics()
 }
 
 void Structure::dumpStatistics()


@@ -191,1079 +115,1156 @@ void Structure::dumpStatistics()
     HashSet<Structure*>::const_iterator end = liveStructureSet.end();
     for (HashSet<Structure*>::const_iterator it = liveStructureSet.begin(); it != end; ++it) {
         Structure* structure = *it;
     HashSet<Structure*>::const_iterator end = liveStructureSet.end();
     for (HashSet<Structure*>::const_iterator it = liveStructureSet.begin(); it != end; ++it) {
         Structure* structure = *it;

-        if (structure->m_usingSingleTransitionSlot) {
-            if (!structure->m_transitions.singleTransition)
+
+        switch (structure->m_transitionTable.size()) {
+            case 0:

                 ++numberLeaf;
                 ++numberLeaf;

-            else
-                ++numberUsingSingleSlot;
+                if (!structure->previousID())
+                    ++numberSingletons;
+                break;

 
 

-           if (!structure->m_previous && !structure->m_transitions.singleTransition)
-                ++numberSingletons;
+            case 1:
+                ++numberUsingSingleSlot;
+                break;

         }
 
         }
 

-        if (structure->m_propertyTable) {
+        if (structure->propertyTable()) {

             ++numberWithPropertyMaps;
             ++numberWithPropertyMaps;

-            totalPropertyMapsSize += PropertyMapHashTable::allocationSize(structure->m_propertyTable->size);
-            if (structure->m_propertyTable->deletedOffsets)
-                totalPropertyMapsSize += (structure->m_propertyTable->deletedOffsets->capacity() * sizeof(unsigned)); 
+            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
 #else

-    printf("Dumping Structure statistics is not enabled.\n");
+    dataLogF("Dumping Structure statistics is not enabled.\n");

 #endif
 }
 
 #endif
 }
 

-Structure::Structure(JSValue prototype, const TypeInfo& typeInfo, unsigned anonymousSlotCount)
-    : m_typeInfo(typeInfo)
-    , m_prototype(prototype)
-    , m_specificValueInPrevious(0)
-    , m_propertyTable(0)
-    , m_propertyStorageCapacity(JSObject::inlineStorageCapacity)
-    , m_offset(noOffset)
-    , m_dictionaryKind(NoneDictionaryKind)
-    , m_isPinnedPropertyTable(false)
-    , m_hasGetterSetterProperties(false)
-    , m_attributesInPrevious(0)
-    , m_specificFunctionThrashCount(0)
-    , m_anonymousSlotCount(anonymousSlotCount)
-    , m_isUsingSingleSlot(true)
+Structure::Structure(VM& vm, JSGlobalObject* globalObject, JSValue prototype, const TypeInfo& typeInfo, const ClassInfo* classInfo, IndexingType indexingType, unsigned inlineCapacity)
+    : JSCell(vm, vm.structureStructure.get())
+    , m_blob(vm.heap.structureIDTable().allocateID(this), indexingType, typeInfo)
+    , m_outOfLineTypeFlags(typeInfo.outOfLineTypeFlags())
+    , m_globalObject(vm, this, globalObject, WriteBarrier<JSGlobalObject>::MayBeNull)
+    , m_prototype(vm, this, prototype)
+    , m_classInfo(classInfo)
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
+    , m_inlineCapacity(inlineCapacity)
+    , m_bitField(0)

 {
 {

-    m_transitions.m_singleTransition = 0;
-
-    ASSERT(m_prototype);
-    ASSERT(m_prototype.isObject() || m_prototype.isNull());
+    setDictionaryKind(NoneDictionaryKind);
+    setIsPinnedPropertyTable(false);
+    setHasGetterSetterProperties(classInfo->hasStaticSetterOrReadonlyProperties());
+    setHasCustomGetterSetterProperties(false);
+    setHasReadOnlyOrGetterSetterPropertiesExcludingProto(classInfo->hasStaticSetterOrReadonlyProperties());
+    setHasNonEnumerableProperties(false);
+    setAttributesInPrevious(0);
+    setPreventExtensions(false);
+    setDidTransition(false);
+    setStaticFunctionsReified(false);
+    setHasRareData(false);
+ 
+    ASSERT(inlineCapacity <= JSFinalObject::maxInlineCapacity());
+    ASSERT(static_cast<PropertyOffset>(inlineCapacity) < firstOutOfLineOffset);
+    ASSERT(!hasRareData());
+    ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties());
+    ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties());
+}

 
 

-#ifndef NDEBUG
-#if ENABLE(JSC_MULTIPLE_THREADS)
-    MutexLocker protect(ignoreSetMutex);
-#endif
-    if (shouldIgnoreLeaks)
-        ignoreSet.add(this);
-    else
-        structureCounter.increment();
-#endif
+const ClassInfo Structure::s_info = { "Structure", 0, 0, CREATE_METHOD_TABLE(Structure) };

 
 

-#if DUMP_STRUCTURE_ID_STATISTICS
-    liveStructureSet.add(this);
-#endif
+Structure::Structure(VM& vm)
+    : JSCell(CreatingEarlyCell)
+    , m_prototype(vm, this, jsNull())
+    , m_classInfo(info())
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
+    , m_inlineCapacity(0)
+    , m_bitField(0)
+{
+    setDictionaryKind(NoneDictionaryKind);
+    setIsPinnedPropertyTable(false);
+    setHasGetterSetterProperties(m_classInfo->hasStaticSetterOrReadonlyProperties());
+    setHasCustomGetterSetterProperties(false);
+    setHasReadOnlyOrGetterSetterPropertiesExcludingProto(m_classInfo->hasStaticSetterOrReadonlyProperties());
+    setHasNonEnumerableProperties(false);
+    setAttributesInPrevious(0);
+    setPreventExtensions(false);
+    setDidTransition(false);
+    setStaticFunctionsReified(false);
+    setHasRareData(false);
+ 
+    TypeInfo typeInfo = TypeInfo(CellType, StructureFlags);
+    m_blob = StructureIDBlob(vm.heap.structureIDTable().allocateID(this), 0, typeInfo);
+    m_outOfLineTypeFlags = typeInfo.outOfLineTypeFlags();
+
+    ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties());
+    ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties());

 }
 
 }
 

-Structure::~Structure()
+Structure::Structure(VM& vm, Structure* previous)
+    : JSCell(vm, vm.structureStructure.get())
+    , m_prototype(vm, this, previous->storedPrototype())
+    , m_classInfo(previous->m_classInfo)
+    , m_transitionWatchpointSet(IsWatched)
+    , m_offset(invalidOffset)
+    , m_inlineCapacity(previous->m_inlineCapacity)
+    , m_bitField(0)

 {
 {

-    if (m_previous) {
-        ASSERT(m_nameInPrevious);
-        m_previous->transitionTableRemove(make_pair(m_nameInPrevious.get(), m_attributesInPrevious), m_specificValueInPrevious);
-
-    }
-    ASSERT(!m_enumerationCache.hasDeadObject());
-
-    if (m_propertyTable) {
-        unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-        for (unsigned i = 1; i <= entryCount; i++) {
-            if (UString::Rep* key = m_propertyTable->entries()[i].key)
-                key->deref();
-        }
-
-        delete m_propertyTable->deletedOffsets;
-        fastFree(m_propertyTable);
-    }
-
-    if (!m_isUsingSingleSlot)
-        delete transitionTable();
-
-#ifndef NDEBUG
-#if ENABLE(JSC_MULTIPLE_THREADS)
-    MutexLocker protect(ignoreSetMutex);
-#endif
-    HashSet<Structure*>::iterator it = ignoreSet.find(this);
-    if (it != ignoreSet.end())
-        ignoreSet.remove(it);
-    else
-        structureCounter.decrement();
-#endif
-
-#if DUMP_STRUCTURE_ID_STATISTICS
-    liveStructureSet.remove(this);
-#endif
+    setDictionaryKind(previous->dictionaryKind());
+    setIsPinnedPropertyTable(previous->hasBeenFlattenedBefore());
+    setHasGetterSetterProperties(previous->hasGetterSetterProperties());
+    setHasCustomGetterSetterProperties(previous->hasCustomGetterSetterProperties());
+    setHasReadOnlyOrGetterSetterPropertiesExcludingProto(previous->hasReadOnlyOrGetterSetterPropertiesExcludingProto());
+    setHasNonEnumerableProperties(previous->hasNonEnumerableProperties());
+    setAttributesInPrevious(0);
+    setPreventExtensions(previous->preventExtensions());
+    setDidTransition(true);
+    setStaticFunctionsReified(previous->staticFunctionsReified());
+    setHasRareData(false);
+ 
+    TypeInfo typeInfo = previous->typeInfo();
+    m_blob = StructureIDBlob(vm.heap.structureIDTable().allocateID(this), previous->indexingTypeIncludingHistory(), typeInfo);
+    m_outOfLineTypeFlags = typeInfo.outOfLineTypeFlags();
+
+    ASSERT(!previous->typeInfo().structureIsImmortal());
+    setPreviousID(vm, previous);
+
+    previous->didTransitionFromThisStructure();
+    if (previous->m_globalObject)
+        m_globalObject.set(vm, this, previous->m_globalObject.get());
+    ASSERT(hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !m_classInfo->hasStaticSetterOrReadonlyProperties());
+    ASSERT(hasGetterSetterProperties() || !m_classInfo->hasStaticSetterOrReadonlyProperties());

 }
 
 }
 

-void Structure::startIgnoringLeaks()
+Structure::~Structure()

 {
 {

-#ifndef NDEBUG
-    shouldIgnoreLeaks = true;
-#endif
+    if (typeInfo().structureIsImmortal())
+        return;
+    Heap::heap(this)->structureIDTable().deallocateID(this, m_blob.structureID());

 }
 
 }
 

-void Structure::stopIgnoringLeaks()
+void Structure::destroy(JSCell* cell)

 {
 {

-#ifndef NDEBUG
-    shouldIgnoreLeaks = false;
-#endif
+    static_cast<Structure*>(cell)->Structure::~Structure();

 }
 
 }
 

-static bool isPowerOf2(unsigned v)
+void Structure::findStructuresAndMapForMaterialization(Vector<Structure*, 8>& structures, Structure*& structure, PropertyTable*& table)

 {
 {

-    // Taken from http://www.cs.utk.edu/~vose/c-stuff/bithacks.html
+    ASSERT(structures.isEmpty());
+    table = 0;
+
+    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();
+    }

     
     

-    return !(v & (v - 1)) && v;
+    ASSERT(!structure);
+    ASSERT(!table);

 }
 
 }
 

-static unsigned nextPowerOf2(unsigned v)
+void Structure::materializePropertyMap(VM& vm)

 {
 {

-    // Taken from http://www.cs.utk.edu/~vose/c-stuff/bithacks.html
-    // Devised by Sean Anderson, Sepember 14, 2001
+    ASSERT(structure()->classInfo() == info());
+    ASSERT(!propertyTable());

 
 

-    v--;
-    v |= v >> 1;
-    v |= v >> 2;
-    v |= v >> 4;
-    v |= v >> 8;
-    v |= v >> 16;
-    v++;
+    Vector<Structure*, 8> structures;
+    Structure* structure;
+    PropertyTable* table;
+    
+    findStructuresAndMapForMaterialization(structures, structure, table);
+    
+    if (table) {
+        table = table->copy(vm, 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);

 
 

-    return v;
+    for (size_t i = structures.size(); i--;) {
+        structure = structures[i];
+        if (!structure->m_nameInPrevious)
+            continue;
+        PropertyMapEntry entry(structure->m_nameInPrevious.get(), structure->m_offset, structure->attributesInPrevious());
+        propertyTable()->add(entry, m_offset, PropertyTable::PropertyOffsetMustNotChange);
+    }
+    
+    checkOffsetConsistency();

 }
 
 }
 

-static unsigned sizeForKeyCount(size_t keyCount)
+Structure* Structure::addPropertyTransitionToExistingStructureImpl(Structure* structure, UniquedStringImpl* uid, unsigned attributes, PropertyOffset& offset)

 {
 {

-    if (keyCount == notFound)
-        return newTableSize;
-
-    if (keyCount < 8)
-        return newTableSize;
+    ASSERT(!structure->isDictionary());
+    ASSERT(structure->isObject());

 
 

-    if (isPowerOf2(keyCount))
-        return keyCount * 4;
+    if (Structure* existingTransition = structure->m_transitionTable.get(uid, attributes)) {
+        validateOffset(existingTransition->m_offset, existingTransition->inlineCapacity());
+        offset = existingTransition->m_offset;
+        return existingTransition;
+    }

 
 

-    return nextPowerOf2(keyCount) * 2;
+    return 0;

 }
 
 }
 

-void Structure::materializePropertyMap()
+Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, PropertyName propertyName, unsigned attributes, PropertyOffset& offset)

 {
 {

-    ASSERT(!m_propertyTable);
-
-    Vector<Structure*, 8> structures;
-    structures.append(this);
+    ASSERT(!isCompilationThread());
+    return addPropertyTransitionToExistingStructureImpl(structure, propertyName.uid(), attributes, offset);
+}

 
 

-    Structure* structure = this;
+Structure* Structure::addPropertyTransitionToExistingStructureConcurrently(Structure* structure, UniquedStringImpl* uid, unsigned attributes, PropertyOffset& offset)
+{
+    ConcurrentJITLocker locker(structure->m_lock);
+    return addPropertyTransitionToExistingStructureImpl(structure, uid, attributes, offset);
+}

 
 

-    // 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);
+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();
+    }
+}

 
 

-            m_propertyTable = structure->copyPropertyTable();
-            break;
-        }
+bool Structure::holesMustForwardToPrototype(VM& vm) const
+{
+    if (this->mayInterceptIndexedAccesses())
+        return true;

 
 

-        structures.append(structure);
-    }
+    JSValue prototype = this->storedPrototype();
+    if (!prototype.isObject())
+        return false;
+    JSObject* object = asObject(prototype);

 
 

-    if (!m_propertyTable)
-        createPropertyMapHashTable(sizeForKeyCount(m_offset + 1));
-    else {
-        if (sizeForKeyCount(m_offset + 1) > m_propertyTable->size)
-            rehashPropertyMapHashTable(sizeForKeyCount(m_offset + 1)); // This could be made more efficient by combining with the copy above. 
+    while (true) {
+        Structure& structure = *object->structure(vm);
+        if (hasIndexedProperties(object->indexingType()) || structure.mayInterceptIndexedAccesses())
+            return true;
+        prototype = structure.storedPrototype();
+        if (!prototype.isObject())
+            return false;
+        object = asObject(prototype);

     }
 
     }
 

-    for (ptrdiff_t i = structures.size() - 2; i >= 0; --i) {
-        structure = structures[i];
-        structure->m_nameInPrevious->ref();
-        PropertyMapEntry entry(structure->m_nameInPrevious.get(), m_anonymousSlotCount + structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious, ++m_propertyTable->lastIndexUsed);
-        insertIntoPropertyMapHashTable(entry);
-    }
+    RELEASE_ASSERT_NOT_REACHED();
+    return false;

 }
 
 }
 

-void Structure::growPropertyStorageCapacity()
+bool Structure::needsSlowPutIndexing() const

 {
 {

-    if (m_propertyStorageCapacity == JSObject::inlineStorageCapacity)
-        m_propertyStorageCapacity = JSObject::nonInlineBaseStorageCapacity;
-    else
-        m_propertyStorageCapacity *= 2;
+    return anyObjectInChainMayInterceptIndexedAccesses()
+        || globalObject()->isHavingABadTime();

 }
 
 }
 

-void Structure::despecifyDictionaryFunction(const Identifier& propertyName)
+NonPropertyTransition Structure::suggestedArrayStorageTransition() const

 {
 {

-    const UString::Rep* rep = propertyName._ustring.rep();
-
-    materializePropertyMapIfNecessary();
-
-    ASSERT(isDictionary());
-    ASSERT(m_propertyTable);
+    if (needsSlowPutIndexing())
+        return AllocateSlowPutArrayStorage;
+    
+    return AllocateArrayStorage;
+}

 
 

-    unsigned i = rep->existingHash();
+Structure* Structure::addPropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes, PropertyOffset& offset, PutPropertySlot::Context context)
+{
+    ASSERT(!structure->isDictionary());
+    ASSERT(structure->isObject());
+    ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, offset));
+    
+    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->add(vm, propertyName, attributes);
+        return transition;
+    }
+    
+    Structure* transition = create(vm, structure);

 
 

-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-#endif
+    transition->m_cachedPrototypeChain.setMayBeNull(vm, transition, structure->m_cachedPrototypeChain.get());
+    transition->m_nameInPrevious = propertyName.uid();
+    transition->setAttributesInPrevious(attributes);
+    transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm));
+    transition->m_offset = structure->m_offset;

 
 

-    unsigned entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-    ASSERT(entryIndex != emptyEntryIndex);
+    offset = transition->add(vm, propertyName, attributes);

 
 

-    if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-        m_propertyTable->entries()[entryIndex - 1].specificValue = 0;
-        return;
+    checkOffset(transition->m_offset, transition->inlineCapacity());
+    {
+        ConcurrentJITLocker locker(structure->m_lock);
+        structure->m_transitionTable.add(vm, transition);

     }
     }

+    transition->checkOffsetConsistency();
+    structure->checkOffsetConsistency();
+    return transition;
+}

 
 

-#if DUMP_PROPERTYMAP_STATS
-    ++numCollisions;
-#endif
-
-    unsigned k = 1 | doubleHash(rep->existingHash());
-
-    while (1) {
-        i += k;
+Structure* Structure::removePropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
+{
+    ASSERT(!structure->isUncacheableDictionary());

 
 

-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
+    Structure* transition = toUncacheableDictionaryTransition(vm, structure);

 
 

-        entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        ASSERT(entryIndex != emptyEntryIndex);
+    offset = transition->remove(propertyName);

 
 

-        if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-            m_propertyTable->entries()[entryIndex - 1].specificValue = 0;
-            return;
-        }
-    }
+    transition->checkOffsetConsistency();
+    return transition;

 }
 
 }
 

-PassRefPtr<Structure> Structure::addPropertyTransitionToExistingStructure(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
+Structure* Structure::changePrototypeTransition(VM& vm, Structure* structure, JSValue prototype)

 {
 {

-    ASSERT(!structure->isDictionary());
-    ASSERT(structure->typeInfo().type() == ObjectType);
+    Structure* transition = create(vm, structure);

 
 

-    if (Structure* existingTransition = structure->transitionTableGet(make_pair(propertyName.ustring().rep(), attributes), specificValue)) {
-        ASSERT(existingTransition->m_offset != noOffset);
-        offset = existingTransition->m_offset + existingTransition->m_anonymousSlotCount;
-        ASSERT(offset >= structure->m_anonymousSlotCount);
-        ASSERT(structure->m_anonymousSlotCount == existingTransition->m_anonymousSlotCount);
-        return existingTransition;
-    }
+    transition->m_prototype.set(vm, transition, prototype);

 
 

-    return 0;
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
+    transition->m_offset = structure->m_offset;
+    transition->pin();
+
+    transition->checkOffsetConsistency();
+    return transition;

 }
 
 }
 

-PassRefPtr<Structure> Structure::addPropertyTransition(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
+Structure* Structure::attributeChangeTransition(VM& vm, Structure* structure, PropertyName propertyName, unsigned attributes)

 {
 {

-    ASSERT(!structure->isDictionary());
-    ASSERT(structure->typeInfo().type() == ObjectType);
-    ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
-    
-    if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
-        specificValue = 0;
-
-    if (structure->transitionCount() > s_maxTransitionLength) {
-        RefPtr<Structure> transition = toCacheableDictionaryTransition(structure);
-        ASSERT(structure != transition);
-        offset = transition->put(propertyName, attributes, specificValue);
-        ASSERT(offset >= structure->m_anonymousSlotCount);
-        ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
-        if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
-            transition->growPropertyStorageCapacity();
-        return transition.release();
-    }
-
-    RefPtr<Structure> transition = create(structure->m_prototype, structure->typeInfo(), structure->anonymousSlotCount());
-
-    transition->m_cachedPrototypeChain = structure->m_cachedPrototypeChain;
-    transition->m_previous = structure;
-    transition->m_nameInPrevious = propertyName.ustring().rep();
-    transition->m_attributesInPrevious = attributes;
-    transition->m_specificValueInPrevious = specificValue;
-    transition->m_propertyStorageCapacity = structure->m_propertyStorageCapacity;
-    transition->m_hasGetterSetterProperties = structure->m_hasGetterSetterProperties;
-    transition->m_hasNonEnumerableProperties = structure->m_hasNonEnumerableProperties;
-    transition->m_specificFunctionThrashCount = structure->m_specificFunctionThrashCount;
-
-    if (structure->m_propertyTable) {
-        if (structure->m_isPinnedPropertyTable)
-            transition->m_propertyTable = structure->copyPropertyTable();
-        else {
-            transition->m_propertyTable = structure->m_propertyTable;
-            structure->m_propertyTable = 0;
-        }
-    } else {
-        if (structure->m_previous)
-            transition->materializePropertyMap();
-        else
-            transition->createPropertyMapHashTable();
+    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->m_offset = structure->m_offset;
+        transition->pin();
+        
+        structure = transition;

     }
 
     }
 

-    offset = transition->put(propertyName, attributes, specificValue);
-    ASSERT(offset >= structure->m_anonymousSlotCount);
-    ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
-    if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
-        transition->growPropertyStorageCapacity();
+    ASSERT(structure->propertyTable());
+    PropertyMapEntry* entry = structure->propertyTable()->get(propertyName.uid());
+    ASSERT(entry);
+    entry->attributes = attributes;

 
 

-    transition->m_offset = offset - structure->m_anonymousSlotCount;
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    structure->transitionTableAdd(make_pair(propertyName.ustring().rep(), attributes), transition.get(), specificValue);
-    return transition.release();
+    structure->checkOffsetConsistency();
+    return structure;

 }
 
 }
 

-PassRefPtr<Structure> Structure::removePropertyTransition(Structure* structure, const Identifier& propertyName, size_t& offset)
+Structure* Structure::toDictionaryTransition(VM& vm, Structure* structure, DictionaryKind kind)

 {
     ASSERT(!structure->isUncacheableDictionary());
 {
     ASSERT(!structure->isUncacheableDictionary());

+    
+    Structure* transition = create(vm, structure);

 
 

-    RefPtr<Structure> transition = toUncacheableDictionaryTransition(structure);
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
+    transition->m_offset = structure->m_offset;
+    transition->setDictionaryKind(kind);
+    transition->pin();

 
 

-    offset = transition->remove(propertyName);
-    ASSERT(offset >= structure->m_anonymousSlotCount);
-    ASSERT(structure->m_anonymousSlotCount == transition->m_anonymousSlotCount);
+    transition->checkOffsetConsistency();
+    return transition;
+}

 
 

-    return transition.release();
+Structure* Structure::toCacheableDictionaryTransition(VM& vm, Structure* structure)
+{
+    return toDictionaryTransition(vm, structure, CachedDictionaryKind);

 }
 
 }
 

-PassRefPtr<Structure> Structure::changePrototypeTransition(Structure* structure, JSValue prototype)
+Structure* Structure::toUncacheableDictionaryTransition(VM& vm, Structure* structure)

 {
 {

-    RefPtr<Structure> transition = create(prototype, structure->typeInfo(), structure->anonymousSlotCount());
+    return toDictionaryTransition(vm, structure, UncachedDictionaryKind);
+}

 
 

-    transition->m_propertyStorageCapacity = structure->m_propertyStorageCapacity;
-    transition->m_hasGetterSetterProperties = structure->m_hasGetterSetterProperties;
-    transition->m_hasNonEnumerableProperties = structure->m_hasNonEnumerableProperties;
-    transition->m_specificFunctionThrashCount = structure->m_specificFunctionThrashCount;
+// In future we may want to cache this transition.
+Structure* Structure::sealTransition(VM& vm, Structure* structure)
+{
+    Structure* transition = preventExtensionsTransition(vm, structure);

 
 

-    // Don't set m_offset, as one can not transition to this.
+    if (transition->propertyTable()) {
+        PropertyTable::iterator end = transition->propertyTable()->end();
+        for (PropertyTable::iterator iter = transition->propertyTable()->begin(); iter != end; ++iter)
+            iter->attributes |= DontDelete;
+    }

 
 

-    structure->materializePropertyMapIfNecessary();
-    transition->m_propertyTable = structure->copyPropertyTable();
-    transition->m_isPinnedPropertyTable = true;
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    return transition.release();
+    transition->checkOffsetConsistency();
+    return transition;

 }
 
 }
 

-PassRefPtr<Structure> Structure::despecifyFunctionTransition(Structure* structure, const Identifier& replaceFunction)
+// In future we may want to cache this transition.
+Structure* Structure::freezeTransition(VM& vm, Structure* structure)

 {
 {

-    ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
-    RefPtr<Structure> transition = create(structure->storedPrototype(), structure->typeInfo(), structure->anonymousSlotCount());
+    Structure* transition = preventExtensionsTransition(vm, structure);
+
+    if (transition->propertyTable()) {
+        PropertyTable::iterator iter = transition->propertyTable()->begin();
+        PropertyTable::iterator end = transition->propertyTable()->end();
+        if (iter != end)
+            transition->setHasReadOnlyOrGetterSetterPropertiesExcludingProto(true);
+        for (; iter != end; ++iter)
+            iter->attributes |= iter->attributes & Accessor ? DontDelete : (DontDelete | ReadOnly);
+    }
+
+    ASSERT(transition->hasReadOnlyOrGetterSetterPropertiesExcludingProto() || !transition->classInfo()->hasStaticSetterOrReadonlyProperties());
+    ASSERT(transition->hasGetterSetterProperties() || !transition->classInfo()->hasStaticSetterOrReadonlyProperties());
+    transition->checkOffsetConsistency();
+    return transition;
+}

 
 

-    transition->m_propertyStorageCapacity = structure->m_propertyStorageCapacity;
-    transition->m_hasGetterSetterProperties = structure->m_hasGetterSetterProperties;
-    transition->m_hasNonEnumerableProperties = structure->m_hasNonEnumerableProperties;
-    transition->m_specificFunctionThrashCount = structure->m_specificFunctionThrashCount + 1;
+// In future we may want to cache this transition.
+Structure* Structure::preventExtensionsTransition(VM& vm, Structure* structure)
+{
+    Structure* transition = create(vm, structure);

 
     // Don't set m_offset, as one can not transition to this.
 
 
     // Don't set m_offset, as one can not transition to this.
 

-    structure->materializePropertyMapIfNecessary();
-    transition->m_propertyTable = structure->copyPropertyTable();
-    transition->m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    structure->materializePropertyMapIfNecessary(vm, deferGC);
+    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
+    transition->m_offset = structure->m_offset;
+    transition->setPreventExtensions(true);
+    transition->pin();

 
 

-    if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
-        transition->despecifyAllFunctions();
-    else {
-        bool removed = transition->despecifyFunction(replaceFunction);
-        ASSERT_UNUSED(removed, removed);
-    }
-    
-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    return transition.release();
+    transition->checkOffsetConsistency();
+    return transition;

 }
 
 }
 

-PassRefPtr<Structure> Structure::getterSetterTransition(Structure* structure)
+PropertyTable* Structure::takePropertyTableOrCloneIfPinned(VM& vm)

 {
 {

-    RefPtr<Structure> transition = create(structure->storedPrototype(), structure->typeInfo(), structure->anonymousSlotCount());
-    transition->m_propertyStorageCapacity = structure->m_propertyStorageCapacity;
-    transition->m_hasGetterSetterProperties = transition->m_hasGetterSetterProperties;
-    transition->m_hasNonEnumerableProperties = structure->m_hasNonEnumerableProperties;
-    transition->m_specificFunctionThrashCount = structure->m_specificFunctionThrashCount;
-
-    // Don't set m_offset, as one can not transition to this.
-
-    structure->materializePropertyMapIfNecessary();
-    transition->m_propertyTable = structure->copyPropertyTable();
-    transition->m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);

     
     

-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    return transition.release();
+    if (isPinnedPropertyTable())
+        return propertyTable()->copy(vm, 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;

 }
 
 }
 

-PassRefPtr<Structure> Structure::toDictionaryTransition(Structure* structure, DictionaryKind kind)
+Structure* Structure::nonPropertyTransition(VM& vm, Structure* structure, NonPropertyTransition transitionKind)

 {
 {

-    ASSERT(!structure->isUncacheableDictionary());
+    unsigned attributes = toAttributes(transitionKind);
+    IndexingType indexingType = newIndexingType(structure->indexingTypeIncludingHistory(), transitionKind);

     
     

-    RefPtr<Structure> transition = create(structure->m_prototype, structure->typeInfo(), structure->anonymousSlotCount());
-    transition->m_dictionaryKind = kind;
-    transition->m_propertyStorageCapacity = structure->m_propertyStorageCapacity;
-    transition->m_hasGetterSetterProperties = structure->m_hasGetterSetterProperties;
-    transition->m_hasNonEnumerableProperties = structure->m_hasNonEnumerableProperties;
-    transition->m_specificFunctionThrashCount = structure->m_specificFunctionThrashCount;
+    if (JSGlobalObject* globalObject = structure->m_globalObject.get()) {
+        if (globalObject->isOriginalArrayStructure(structure)) {
+            Structure* result = globalObject->originalArrayStructureForIndexingType(indexingType);
+            if (result->indexingTypeIncludingHistory() == indexingType) {
+                structure->didTransitionFromThisStructure();
+                return result;
+            }
+        }
+    }

     
     

-    structure->materializePropertyMapIfNecessary();
-    transition->m_propertyTable = structure->copyPropertyTable();
-    transition->m_isPinnedPropertyTable = true;
+    Structure* existingTransition;
+    if (!structure->isDictionary() && (existingTransition = structure->m_transitionTable.get(0, attributes))) {
+        ASSERT(existingTransition->attributesInPrevious() == attributes);
+        ASSERT(existingTransition->indexingTypeIncludingHistory() == indexingType);
+        return existingTransition;
+    }

     
     

-    ASSERT(structure->anonymousSlotCount() == transition->anonymousSlotCount());
-    return transition.release();
+    Structure* transition = create(vm, structure);
+    transition->setAttributesInPrevious(attributes);
+    transition->m_blob.setIndexingType(indexingType);
+    transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm));
+    transition->m_offset = structure->m_offset;
+    checkOffset(transition->m_offset, transition->inlineCapacity());
+    
+    if (structure->isDictionary())
+        transition->pin();
+    else {
+        ConcurrentJITLocker locker(structure->m_lock);
+        structure->m_transitionTable.add(vm, transition);
+    }
+    transition->checkOffsetConsistency();
+    return transition;

 }
 
 }
 

-PassRefPtr<Structure> Structure::toCacheableDictionaryTransition(Structure* structure)
+// In future we may want to cache this property.
+bool Structure::isSealed(VM& vm)

 {
 {

-    return toDictionaryTransition(structure, CachedDictionaryKind);
+    if (isExtensible())
+        return false;
+
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
+        return true;
+
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
+        if ((iter->attributes & DontDelete) != DontDelete)
+            return false;
+    }
+    return true;

 }
 
 }
 

-PassRefPtr<Structure> Structure::toUncacheableDictionaryTransition(Structure* structure)
+// In future we may want to cache this property.
+bool Structure::isFrozen(VM& vm)

 {
 {

-    return toDictionaryTransition(structure, UncachedDictionaryKind);
+    if (isExtensible())
+        return false;
+
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
+        return true;
+
+    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;

 }
 
 }
 

-PassRefPtr<Structure> Structure::flattenDictionaryStructure(JSObject* object)
+Structure* Structure::flattenDictionaryStructure(VM& vm, JSObject* object)

 {
 {

+    checkOffsetConsistency();

     ASSERT(isDictionary());
     ASSERT(isDictionary());

+
+    size_t beforeOutOfLineCapacity = this->outOfLineCapacity();

     if (isUncacheableDictionary()) {
     if (isUncacheableDictionary()) {

-        ASSERT(m_propertyTable);
-        Vector<PropertyMapEntry*> sortedPropertyEntries(m_propertyTable->keyCount);
-        PropertyMapEntry** p = sortedPropertyEntries.data();
-        unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-        for (unsigned i = 1; i <= entryCount; i++) {
-            if (m_propertyTable->entries()[i].key)
-                *p++ = &m_propertyTable->entries()[i];
-        }
-        size_t propertyCount = p - sortedPropertyEntries.data();
-        qsort(sortedPropertyEntries.data(), propertyCount, sizeof(PropertyMapEntry*), comparePropertyMapEntryIndices);
-        sortedPropertyEntries.resize(propertyCount);
+        ASSERT(propertyTable());

 
 

-        // We now have the properties currently defined on this object
-        // in the order that they are expected to be in, but we need to
-        // reorder the storage, so we have to copy the current values out
+        size_t propertyCount = propertyTable()->size();
+
+        // Holds our values compacted by insertion order.

         Vector<JSValue> values(propertyCount);
         Vector<JSValue> values(propertyCount);

-        unsigned anonymousSlotCount = m_anonymousSlotCount;
-        for (unsigned i = 0; i < propertyCount; i++) {
-            PropertyMapEntry* entry = sortedPropertyEntries[i];
-            values[i] = object->getDirectOffset(entry->offset);
-            // Update property table to have the new property offsets
-            entry->offset = anonymousSlotCount + i;
-            entry->index = i;
+
+        // Copies out our values from their hashed locations, compacting property table offsets as we go.
+        unsigned i = 0;
+        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++)
         for (unsigned i = 0; i < propertyCount; i++)

-            object->putDirectOffset(anonymousSlotCount + i, values[i]);
+            object->putDirect(vm, offsetForPropertyNumber(i, m_inlineCapacity), values[i]);

 
 

-        if (m_propertyTable->deletedOffsets) {
-            delete m_propertyTable->deletedOffsets;
-            m_propertyTable->deletedOffsets = 0;
-        }
+        propertyTable()->clearDeletedOffsets();
+        checkOffsetConsistency();
+    }
+
+    setDictionaryKind(NoneDictionaryKind);
+    setHasBeenFlattenedBefore(true);
+
+    size_t afterOutOfLineCapacity = this->outOfLineCapacity();
+
+    if (beforeOutOfLineCapacity != afterOutOfLineCapacity) {
+        ASSERT(beforeOutOfLineCapacity > afterOutOfLineCapacity);
+        // 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() && !afterOutOfLineCapacity && !this->hasIndexingHeader(object))
+            object->setStructureAndButterfly(vm, this, 0);
+        // If the object was down-sized to the point where the base of the Butterfly is no longer within the 
+        // first CopiedBlock::blockSize bytes, we'll get the wrong answer if we try to mask the base back to 
+        // the CopiedBlock header. To prevent this case we need to memmove the Butterfly down.
+        else if (object->butterfly())
+            object->shiftButterflyAfterFlattening(vm, beforeOutOfLineCapacity, afterOutOfLineCapacity);

     }
 
     }
 

-    m_dictionaryKind = NoneDictionaryKind;

     return this;
 }
 
     return this;
 }
 

-size_t Structure::addPropertyWithoutTransition(const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
+PropertyOffset Structure::addPropertyWithoutTransition(VM& vm, PropertyName propertyName, unsigned attributes)

 {
 {

-    ASSERT(!m_enumerationCache);
-
-    if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
-        specificValue = 0;
-
-    materializePropertyMapIfNecessary();
-
-    m_isPinnedPropertyTable = true;
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);
+    
+    pin();

 
 

-    size_t offset = put(propertyName, attributes, specificValue);
-    ASSERT(offset >= m_anonymousSlotCount);
-    if (propertyStorageSize() > propertyStorageCapacity())
-        growPropertyStorageCapacity();
-    return offset;
+    return add(vm, propertyName, attributes);

 }
 
 }
 

-size_t Structure::removePropertyWithoutTransition(const Identifier& propertyName)
+PropertyOffset Structure::removePropertyWithoutTransition(VM& vm, PropertyName propertyName)

 {
     ASSERT(isUncacheableDictionary());
 {
     ASSERT(isUncacheableDictionary());

-    ASSERT(!m_enumerationCache);

 
 

-    materializePropertyMapIfNecessary();
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessaryForPinning(vm, deferGC);

 
 

-    m_isPinnedPropertyTable = true;
-    size_t offset = remove(propertyName);
-    ASSERT(offset >= m_anonymousSlotCount);
-    return offset;
+    pin();
+    return remove(propertyName);

 }
 
 }
 

-#if DUMP_PROPERTYMAP_STATS
-
-static int numProbes;
-static int numCollisions;
-static int numRehashes;
-static int numRemoves;
-
-struct PropertyMapStatisticsExitLogger {
-    ~PropertyMapStatisticsExitLogger();
-};
-
-static PropertyMapStatisticsExitLogger logger;
-
-PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
+void Structure::pin()

 {
 {

-    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);
+    ASSERT(propertyTable());
+    setIsPinnedPropertyTable(true);
+    clearPreviousID();
+    m_nameInPrevious = nullptr;

 }
 
 }
 

-#endif
-
-static const unsigned deletedSentinelIndex = 1;
-
-#if !DO_PROPERTYMAP_CONSTENCY_CHECK
-
-inline void Structure::checkConsistency()
+void Structure::allocateRareData(VM& vm)

 {
 {

+    ASSERT(!hasRareData());
+    StructureRareData* rareData = StructureRareData::create(vm, previous());
+    WTF::storeStoreFence();
+    m_previousOrRareData.set(vm, this, rareData);
+    WTF::storeStoreFence();
+    setHasRareData(true);
+    ASSERT(hasRareData());

 }
 
 }
 

-#endif
-
-PropertyMapHashTable* Structure::copyPropertyTable()
+WatchpointSet* Structure::ensurePropertyReplacementWatchpointSet(VM& vm, PropertyOffset offset)

 {
 {

-    if (!m_propertyTable)
-        return 0;
-
-    size_t tableSize = PropertyMapHashTable::allocationSize(m_propertyTable->size);
-    PropertyMapHashTable* newTable = static_cast<PropertyMapHashTable*>(fastMalloc(tableSize));
-    memcpy(newTable, m_propertyTable, tableSize);
-
-    unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-    for (unsigned i = 1; i <= entryCount; ++i) {
-        if (UString::Rep* key = newTable->entries()[i].key)
-            key->ref();
+    ASSERT(!isUncacheableDictionary());
+    
+    if (!hasRareData())
+        allocateRareData(vm);
+    ConcurrentJITLocker locker(m_lock);
+    StructureRareData* rareData = this->rareData();
+    if (!rareData->m_replacementWatchpointSets) {
+        rareData->m_replacementWatchpointSets =
+            std::make_unique<StructureRareData::PropertyWatchpointMap>();
+        WTF::storeStoreFence();

     }
     }

-
-    // Copy the deletedOffsets vector.
-    if (m_propertyTable->deletedOffsets)
-        newTable->deletedOffsets = new Vector<unsigned>(*m_propertyTable->deletedOffsets);
-
-    return newTable;
+    auto result = rareData->m_replacementWatchpointSets->add(offset, nullptr);
+    if (result.isNewEntry)
+        result.iterator->value = adoptRef(new WatchpointSet(IsWatched));
+    return result.iterator->value.get();

 }
 
 }
 

-size_t Structure::get(const UString::Rep* rep, unsigned& attributes, JSCell*& specificValue)
+void Structure::startWatchingPropertyForReplacements(VM& vm, PropertyName propertyName)

 {
 {

-    materializePropertyMapIfNecessary();
-    if (!m_propertyTable)
-        return notFound;
-
-    unsigned i = rep->existingHash();
-
-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-#endif
+    ASSERT(!isUncacheableDictionary());
+    
+    PropertyOffset offset = get(vm, propertyName);
+    if (!JSC::isValidOffset(offset))
+        return;
+    
+    startWatchingPropertyForReplacements(vm, offset);
+}

 
 

-    unsigned entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-    if (entryIndex == emptyEntryIndex)
-        return notFound;
+void Structure::didCachePropertyReplacement(VM& vm, PropertyOffset offset)
+{
+    ensurePropertyReplacementWatchpointSet(vm, offset)->fireAll("Did cache property replacement");
+}

 
 

-    if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-        attributes = m_propertyTable->entries()[entryIndex - 1].attributes;
-        specificValue = m_propertyTable->entries()[entryIndex - 1].specificValue;
-        ASSERT(m_propertyTable->entries()[entryIndex - 1].offset >= m_anonymousSlotCount);
-        return m_propertyTable->entries()[entryIndex - 1].offset;
+void Structure::startWatchingInternalProperties(VM& vm)
+{
+    if (!isUncacheableDictionary()) {
+        startWatchingPropertyForReplacements(vm, vm.propertyNames->toString);
+        startWatchingPropertyForReplacements(vm, vm.propertyNames->valueOf);

     }
     }

+    setDidWatchInternalProperties(true);
+}

 
 #if DUMP_PROPERTYMAP_STATS
 
 #if DUMP_PROPERTYMAP_STATS

-    ++numCollisions;
-#endif
-
-    unsigned k = 1 | doubleHash(rep->existingHash());

 
 

-    while (1) {
-        i += k;
+PropertyMapHashTableStats* propertyMapHashTableStats = 0;

 
 

-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
+struct PropertyMapStatisticsExitLogger {
+    PropertyMapStatisticsExitLogger();
+    ~PropertyMapStatisticsExitLogger();
+};

 
 

-        entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        if (entryIndex == emptyEntryIndex)
-            return notFound;
+DEFINE_GLOBAL_FOR_LOGGING(PropertyMapStatisticsExitLogger, logger, );

 
 

-        if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-            attributes = m_propertyTable->entries()[entryIndex - 1].attributes;
-            specificValue = m_propertyTable->entries()[entryIndex - 1].specificValue;
-            ASSERT(m_propertyTable->entries()[entryIndex - 1].offset >= m_anonymousSlotCount);
-            return m_propertyTable->entries()[entryIndex - 1].offset;
-        }
-    }
+PropertyMapStatisticsExitLogger::PropertyMapStatisticsExitLogger()
+{
+    propertyMapHashTableStats = adoptPtr(new PropertyMapHashTableStats()).leakPtr();

 }
 
 }
 

-bool Structure::despecifyFunction(const Identifier& propertyName)
+PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()

 {
 {

-    ASSERT(!propertyName.isNull());
-
-    materializePropertyMapIfNecessary();
-    if (!m_propertyTable)
-        return false;
-
-    UString::Rep* rep = propertyName._ustring.rep();
-
-    unsigned i = rep->existingHash();
-
-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-#endif
-
-    unsigned entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-    if (entryIndex == emptyEntryIndex)
-        return false;
-
-    if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-        ASSERT(m_propertyTable->entries()[entryIndex - 1].specificValue);
-        m_propertyTable->entries()[entryIndex - 1].specificValue = 0;
-        return true;
-    }
+    unsigned finds = propertyMapHashTableStats->numFinds;
+    unsigned collisions = propertyMapHashTableStats->numCollisions;
+    dataLogF("\nJSC::PropertyMap statistics for process %d\n\n", getCurrentProcessID());
+    dataLogF("%d finds\n", finds);
+    dataLogF("%d collisions (%.1f%%)\n", collisions, 100.0 * collisions / finds);
+    dataLogF("%d lookups\n", propertyMapHashTableStats->numLookups.load());
+    dataLogF("%d lookup probings\n", propertyMapHashTableStats->numLookupProbing.load());
+    dataLogF("%d adds\n", propertyMapHashTableStats->numAdds.load());
+    dataLogF("%d removes\n", propertyMapHashTableStats->numRemoves.load());
+    dataLogF("%d rehashes\n", propertyMapHashTableStats->numRehashes.load());
+    dataLogF("%d reinserts\n", propertyMapHashTableStats->numReinserts.load());
+}

 
 

-#if DUMP_PROPERTYMAP_STATS
-    ++numCollisions;

 #endif
 
 #endif
 

-    unsigned k = 1 | doubleHash(rep->existingHash());
-
-    while (1) {
-        i += k;
+PropertyTable* Structure::copyPropertyTable(VM& vm)
+{
+    if (!propertyTable())
+        return 0;
+    return PropertyTable::clone(vm, *propertyTable().get());
+}

 
 

-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
+PropertyTable* Structure::copyPropertyTableForPinning(VM& vm)
+{
+    if (propertyTable())
+        return PropertyTable::clone(vm, *propertyTable().get());
+    return PropertyTable::create(vm, numberOfSlotsForLastOffset(m_offset, m_inlineCapacity));
+}

 
 

-        entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        if (entryIndex == emptyEntryIndex)
+PropertyOffset Structure::getConcurrently(UniquedStringImpl* uid, unsigned& attributes)
+{
+    PropertyOffset result = invalidOffset;
+    
+    forEachPropertyConcurrently(
+        [&] (const PropertyMapEntry& candidate) -> bool {
+            if (candidate.key != uid)
+                return true;
+            
+            result = candidate.offset;
+            attributes = candidate.attributes;

             return false;
             return false;

-
-        if (rep == m_propertyTable->entries()[entryIndex - 1].key) {
-            ASSERT(m_propertyTable->entries()[entryIndex - 1].specificValue);
-            m_propertyTable->entries()[entryIndex - 1].specificValue = 0;
-            return true;
-        }
-    }
+        });
+    
+    return result;

 }
 
 }
 

-void Structure::despecifyAllFunctions()
+Vector<PropertyMapEntry> Structure::getPropertiesConcurrently()

 {
 {

-    materializePropertyMapIfNecessary();
-    if (!m_propertyTable)
-        return;
+    Vector<PropertyMapEntry> result;
+
+    forEachPropertyConcurrently(
+        [&] (const PropertyMapEntry& entry) -> bool {
+            result.append(entry);
+            return true;
+        });

     
     

-    unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-    for (unsigned i = 1; i <= entryCount; ++i)
-        m_propertyTable->entries()[i].specificValue = 0;
+    return result;

 }
 
 }
 

-size_t Structure::put(const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
+PropertyOffset Structure::add(VM& vm, PropertyName propertyName, unsigned attributes)

 {
 {

-    ASSERT(!propertyName.isNull());
-    ASSERT(get(propertyName) == notFound);
+    GCSafeConcurrentJITLocker locker(m_lock, vm.heap);
+    
+    ASSERT(!JSC::isValidOffset(get(vm, propertyName)));

 
     checkConsistency();
 
     checkConsistency();

-

     if (attributes & DontEnum)
     if (attributes & DontEnum)

-        m_hasNonEnumerableProperties = true;
-
-    UString::Rep* rep = propertyName._ustring.rep();
+        setHasNonEnumerableProperties(true);

 
 

-    if (!m_propertyTable)
-        createPropertyMapHashTable();
+    auto rep = propertyName.uid();

 
 

-    // FIXME: Consider a fast case for tables with no deleted sentinels.
+    if (!propertyTable())
+        createPropertyMap(locker, vm);

 
 

-    unsigned i = rep->existingHash();
-    unsigned k = 0;
-    bool foundDeletedElement = false;
-    unsigned deletedElementIndex = 0; // initialize to make the compiler happy
-
-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-#endif
-
-    while (1) {
-        unsigned entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        if (entryIndex == emptyEntryIndex)
-            break;
-
-        if (entryIndex == deletedSentinelIndex) {
-            // If we find a deleted-element sentinel, remember it for use later.
-            if (!foundDeletedElement) {
-                foundDeletedElement = true;
-                deletedElementIndex = i;
-            }
-        }
-
-        if (k == 0) {
-            k = 1 | doubleHash(rep->existingHash());
-#if DUMP_PROPERTYMAP_STATS
-            ++numCollisions;
-#endif
-        }
-
-        i += k;
-
-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
-    }
-
-    // Figure out which entry to use.
-    unsigned entryIndex = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount + 2;
-    if (foundDeletedElement) {
-        i = deletedElementIndex;
-        --m_propertyTable->deletedSentinelCount;
-
-        // Since we're not making the table bigger, we can't use the entry one past
-        // the end that we were planning on using, so search backwards for the empty
-        // slot that we can use. We know it will be there because we did at least one
-        // deletion in the past that left an entry empty.
-        while (m_propertyTable->entries()[--entryIndex - 1].key) { }
-    }
+    PropertyOffset newOffset = propertyTable()->nextOffset(m_inlineCapacity);

 
 

-    // Create a new hash table entry.
-    m_propertyTable->entryIndices[i & m_propertyTable->sizeMask] = entryIndex;
-
-    // Create a new hash table entry.
-    rep->ref();
-    m_propertyTable->entries()[entryIndex - 1].key = rep;
-    m_propertyTable->entries()[entryIndex - 1].attributes = attributes;
-    m_propertyTable->entries()[entryIndex - 1].specificValue = specificValue;
-    m_propertyTable->entries()[entryIndex - 1].index = ++m_propertyTable->lastIndexUsed;
-
-    unsigned newOffset;
-    if (m_propertyTable->deletedOffsets && !m_propertyTable->deletedOffsets->isEmpty()) {
-        newOffset = m_propertyTable->deletedOffsets->last();
-        m_propertyTable->deletedOffsets->removeLast();
-    } else
-        newOffset = m_propertyTable->keyCount + m_anonymousSlotCount;
-    m_propertyTable->entries()[entryIndex - 1].offset = newOffset;
+    propertyTable()->add(PropertyMapEntry(rep, newOffset, attributes), m_offset, PropertyTable::PropertyOffsetMayChange);

     
     

-    ASSERT(newOffset >= m_anonymousSlotCount);
-    ++m_propertyTable->keyCount;
-
-    if ((m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount) * 2 >= m_propertyTable->size)
-        expandPropertyMapHashTable();
-

     checkConsistency();
     return newOffset;
 }
 
     checkConsistency();
     return newOffset;
 }
 

-bool Structure::hasTransition(UString::Rep* rep, unsigned attributes)
-{
-    return transitionTableHasTransition(make_pair(rep, attributes));
-}
-
-size_t Structure::remove(const Identifier& propertyName)
+PropertyOffset Structure::remove(PropertyName propertyName)

 {
 {

-    ASSERT(!propertyName.isNull());
-
+    ConcurrentJITLocker locker(m_lock);
+    

     checkConsistency();
 
     checkConsistency();
 

-    UString::Rep* rep = propertyName._ustring.rep();
+    auto rep = propertyName.uid();

 
 

-    if (!m_propertyTable)
-        return notFound;
+    if (!propertyTable())
+        return invalidOffset;

 
 

-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-    ++numRemoves;
-#endif
+    PropertyTable::find_iterator position = propertyTable()->find(rep);
+    if (!position.first)
+        return invalidOffset;

 
 

-    // Find the thing to remove.
-    unsigned i = rep->existingHash();
-    unsigned k = 0;
-    unsigned entryIndex;
-    UString::Rep* key = 0;
-    while (1) {
-        entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        if (entryIndex == emptyEntryIndex)
-            return notFound;
-
-        key = m_propertyTable->entries()[entryIndex - 1].key;
-        if (rep == key)
-            break;
+    PropertyOffset offset = position.first->offset;

 
 

-        if (k == 0) {
-            k = 1 | doubleHash(rep->existingHash());
-#if DUMP_PROPERTYMAP_STATS
-            ++numCollisions;
-#endif
-        }
-
-        i += k;
-
-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
-    }
-
-    // Replace this one element with the deleted sentinel. Also clear out
-    // the entry so we can iterate all the entries as needed.
-    m_propertyTable->entryIndices[i & m_propertyTable->sizeMask] = deletedSentinelIndex;
-
-    size_t offset = m_propertyTable->entries()[entryIndex - 1].offset;
-    ASSERT(offset >= m_anonymousSlotCount);
-
-    key->deref();
-    m_propertyTable->entries()[entryIndex - 1].key = 0;
-    m_propertyTable->entries()[entryIndex - 1].attributes = 0;
-    m_propertyTable->entries()[entryIndex - 1].specificValue = 0;
-    m_propertyTable->entries()[entryIndex - 1].offset = 0;
-
-    if (!m_propertyTable->deletedOffsets)
-        m_propertyTable->deletedOffsets = new Vector<unsigned>;
-    m_propertyTable->deletedOffsets->append(offset);
-
-    ASSERT(m_propertyTable->keyCount >= 1);
-    --m_propertyTable->keyCount;
-    ++m_propertyTable->deletedSentinelCount;
-
-    if (m_propertyTable->deletedSentinelCount * 4 >= m_propertyTable->size)
-        rehashPropertyMapHashTable();
+    propertyTable()->remove(position);
+    propertyTable()->addDeletedOffset(offset);

 
     checkConsistency();
     return offset;
 }
 
 
     checkConsistency();
     return offset;
 }
 

-void Structure::insertIntoPropertyMapHashTable(const PropertyMapEntry& entry)
+void Structure::createPropertyMap(const GCSafeConcurrentJITLocker&, VM& vm, unsigned capacity)

 {
 {

-    ASSERT(m_propertyTable);
-    ASSERT(entry.offset >= m_anonymousSlotCount);
-    unsigned i = entry.key->existingHash();
-    unsigned k = 0;
+    ASSERT(!propertyTable());

 
 

-#if DUMP_PROPERTYMAP_STATS
-    ++numProbes;
-#endif
+    checkConsistency();
+    propertyTable().set(vm, this, PropertyTable::create(vm, capacity));
+}

 
 

-    while (1) {
-        unsigned entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-        if (entryIndex == emptyEntryIndex)
-            break;
+void Structure::getPropertyNamesFromStructure(VM& vm, PropertyNameArray& propertyNames, EnumerationMode mode)
+{
+    DeferGC deferGC(vm.heap);
+    materializePropertyMapIfNecessary(vm, deferGC);
+    if (!propertyTable())
+        return;

 
 

-        if (k == 0) {
-            k = 1 | doubleHash(entry.key->existingHash());
-#if DUMP_PROPERTYMAP_STATS
-            ++numCollisions;
-#endif
+    bool knownUnique = propertyNames.canAddKnownUniqueForStructure();
+
+    PropertyTable::iterator end = propertyTable()->end();
+    for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
+        ASSERT(hasNonEnumerableProperties() || !(iter->attributes & DontEnum));
+        if (!(iter->attributes & DontEnum) || mode.includeDontEnumProperties()) {
+            if (iter->key->isSymbol() && !mode.includeSymbolProperties())
+                continue;
+            if (knownUnique)
+                propertyNames.addKnownUnique(iter->key);
+            else
+                propertyNames.add(iter->key);

         }
         }

+    }
+}

 
 

-        i += k;
+namespace {

 
 

-#if DUMP_PROPERTYMAP_STATS
-        ++numRehashes;
-#endif
+class StructureFireDetail : public FireDetail {
+public:
+    StructureFireDetail(const Structure* structure)
+        : m_structure(structure)
+    {
+    }
+    
+    virtual void dump(PrintStream& out) const override
+    {
+        out.print("Structure transition from ", *m_structure);

     }
 
     }
 

-    unsigned entryIndex = m_propertyTable->keyCount + 2;
-    m_propertyTable->entryIndices[i & m_propertyTable->sizeMask] = entryIndex;
-    m_propertyTable->entries()[entryIndex - 1] = entry;
+private:
+    const Structure* m_structure;
+};

 
 

-    ++m_propertyTable->keyCount;
-}
+} // anonymous namespace

 
 

-void Structure::createPropertyMapHashTable()
+void Structure::didTransitionFromThisStructure() const

 {
 {

-    ASSERT(sizeForKeyCount(7) == newTableSize);
-    createPropertyMapHashTable(newTableSize);
+    m_transitionWatchpointSet.fireAll(StructureFireDetail(this));

 }
 
 }
 

-void Structure::createPropertyMapHashTable(unsigned newTableSize)
+JSValue Structure::prototypeForLookup(CodeBlock* codeBlock) const

 {
 {

-    ASSERT(!m_propertyTable);
-    ASSERT(isPowerOf2(newTableSize));
-
-    checkConsistency();
-
-    m_propertyTable = static_cast<PropertyMapHashTable*>(fastZeroedMalloc(PropertyMapHashTable::allocationSize(newTableSize)));
-    m_propertyTable->size = newTableSize;
-    m_propertyTable->sizeMask = newTableSize - 1;
-
-    checkConsistency();
+    return prototypeForLookup(codeBlock->globalObject());

 }
 
 }
 

-void Structure::expandPropertyMapHashTable()
+void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)

 {
 {

-    ASSERT(m_propertyTable);
-    rehashPropertyMapHashTable(m_propertyTable->size * 2);
+    Structure* thisObject = jsCast<Structure*>(cell);
+    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
+
+    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);
+
+    if (thisObject->isPinnedPropertyTable()) {
+        ASSERT(thisObject->m_propertyTableUnsafe);
+        visitor.append(&thisObject->m_propertyTableUnsafe);
+    } else if (thisObject->m_propertyTableUnsafe)
+        thisObject->m_propertyTableUnsafe.clear();

 }
 
 }
 

-void Structure::rehashPropertyMapHashTable()
+bool Structure::prototypeChainMayInterceptStoreTo(VM& vm, PropertyName propertyName)

 {
 {

-    ASSERT(m_propertyTable);
-    ASSERT(m_propertyTable->size);
-    rehashPropertyMapHashTable(m_propertyTable->size);
+    if (parseIndex(propertyName))
+        return anyObjectInChainMayInterceptIndexedAccesses();
+    
+    for (Structure* current = this; ;) {
+        JSValue prototype = current->storedPrototype();
+        if (prototype.isNull())
+            return false;
+        
+        current = prototype.asCell()->structure(vm);
+        
+        unsigned attributes;
+        PropertyOffset offset = current->get(vm, propertyName, attributes);
+        if (!JSC::isValidOffset(offset))
+            continue;
+        
+        if (attributes & (ReadOnly | Accessor))
+            return true;
+        
+        return false;
+    }

 }
 
 }
 

-void Structure::rehashPropertyMapHashTable(unsigned newTableSize)
+PassRefPtr<StructureShape> Structure::toStructureShape(JSValue value)

 {
 {

-    ASSERT(m_propertyTable);
-    ASSERT(isPowerOf2(newTableSize));
+    RefPtr<StructureShape> baseShape = StructureShape::create();
+    RefPtr<StructureShape> curShape = baseShape;
+    Structure* curStructure = this;
+    JSValue curValue = value;
+    while (curStructure) {
+        Vector<Structure*, 8> structures;
+        Structure* structure;
+        PropertyTable* table;
+
+        curStructure->findStructuresAndMapForMaterialization(structures, structure, table);
+        if (table) {
+            PropertyTable::iterator iter = table->begin();
+            PropertyTable::iterator end = table->end();
+            for (; iter != end; ++iter)
+                curShape->addProperty(*iter->key);
+            
+            structure->m_lock.unlock();
+        }
+        for (unsigned i = structures.size(); i--;) {
+            Structure* structure = structures[i];
+            if (structure->m_nameInPrevious)
+                curShape->addProperty(*structure->m_nameInPrevious);
+        }

 
 

-    checkConsistency();
+        if (JSObject* curObject = curValue.getObject())
+            curShape->setConstructorName(JSObject::calculatedClassName(curObject));
+        else
+            curShape->setConstructorName(curStructure->classInfo()->className);

 
 

-    PropertyMapHashTable* oldTable = m_propertyTable;
+        if (curStructure->isDictionary())
+            curShape->enterDictionaryMode();

 
 

-    m_propertyTable = static_cast<PropertyMapHashTable*>(fastZeroedMalloc(PropertyMapHashTable::allocationSize(newTableSize)));
-    m_propertyTable->size = newTableSize;
-    m_propertyTable->sizeMask = newTableSize - 1;
+        curShape->markAsFinal();

 
 

-    unsigned lastIndexUsed = 0;
-    unsigned entryCount = oldTable->keyCount + oldTable->deletedSentinelCount;
-    for (unsigned i = 1; i <= entryCount; ++i) {
-        if (oldTable->entries()[i].key) {
-            lastIndexUsed = max(oldTable->entries()[i].index, lastIndexUsed);
-            insertIntoPropertyMapHashTable(oldTable->entries()[i]);
+        if (curStructure->storedPrototypeStructure()) {
+            RefPtr<StructureShape> newShape = StructureShape::create();
+            curShape->setProto(newShape);
+            curShape = newShape.release();
+            curValue = curStructure->storedPrototype();

         }
         }

-    }
-    m_propertyTable->lastIndexUsed = lastIndexUsed;
-    m_propertyTable->deletedOffsets = oldTable->deletedOffsets;
-
-    fastFree(oldTable);

 
 

-    checkConsistency();
+        curStructure = curStructure->storedPrototypeStructure();
+    }
+    
+    return baseShape.release();

 }
 
 }
 

-int comparePropertyMapEntryIndices(const void* a, const void* b)
+bool Structure::canUseForAllocationsOf(Structure* other)

 {
 {

-    unsigned ia = static_cast<PropertyMapEntry* const*>(a)[0]->index;
-    unsigned ib = static_cast<PropertyMapEntry* const*>(b)[0]->index;
-    if (ia < ib)
-        return -1;
-    if (ia > ib)
-        return +1;
-    return 0;
+    return inlineCapacity() == other->inlineCapacity()
+        && storedPrototype() == other->storedPrototype()
+        && objectInitializationBlob() == other->objectInitializationBlob();

 }
 
 }
 

-void Structure::getPropertyNames(PropertyNameArray& propertyNames, EnumerationMode mode)
+void Structure::dump(PrintStream& out) const

 {
 {

-    materializePropertyMapIfNecessary();
-    if (!m_propertyTable)
-        return;
-
-    if (m_propertyTable->keyCount < tinyMapThreshold) {
-        PropertyMapEntry* a[tinyMapThreshold];
-        int i = 0;
-        unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-        for (unsigned k = 1; k <= entryCount; k++) {
-            ASSERT(m_hasNonEnumerableProperties || !(m_propertyTable->entries()[k].attributes & DontEnum));
-            if (m_propertyTable->entries()[k].key && (!(m_propertyTable->entries()[k].attributes & DontEnum) || (mode == IncludeDontEnumProperties))) {
-                PropertyMapEntry* value = &m_propertyTable->entries()[k];
-                int j;
-                for (j = i - 1; j >= 0 && a[j]->index > value->index; --j)
-                    a[j + 1] = a[j];
-                a[j + 1] = value;
-                ++i;
-            }
-        }
-        if (!propertyNames.size()) {
-            for (int k = 0; k < i; ++k)
-                propertyNames.addKnownUnique(a[k]->key);
-        } else {
-            for (int k = 0; k < i; ++k)
-                propertyNames.add(a[k]->key);
-        }
-
-        return;
-    }
+    out.print(RawPointer(this), ":[", classInfo()->className, ", {");
+    
+    CommaPrinter comma;
+    
+    const_cast<Structure*>(this)->forEachPropertyConcurrently(
+        [&] (const PropertyMapEntry& entry) -> bool {
+            out.print(comma, entry.key, ":", static_cast<int>(entry.offset));
+            return true;
+        });
+    
+    out.print("}, ", IndexingTypeDump(indexingType()));
+    
+    if (m_prototype.get().isCell())
+        out.print(", Proto:", RawPointer(m_prototype.get().asCell()));
+    
+    out.print("]");
+}

 
 

-    // Allocate a buffer to use to sort the keys.
-    Vector<PropertyMapEntry*, smallMapThreshold> sortedEnumerables(m_propertyTable->keyCount);
+void Structure::dumpInContext(PrintStream& out, DumpContext* context) const
+{
+    if (context)
+        context->structures.dumpBrief(this, out);
+    else
+        dump(out);
+}

 
 

-    // Get pointers to the enumerable entries in the buffer.
-    PropertyMapEntry** p = sortedEnumerables.data();
-    unsigned entryCount = m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount;
-    for (unsigned i = 1; i <= entryCount; i++) {
-        if (m_propertyTable->entries()[i].key && (!(m_propertyTable->entries()[i].attributes & DontEnum) || (mode == IncludeDontEnumProperties)))
-            *p++ = &m_propertyTable->entries()[i];
-    }
+void Structure::dumpBrief(PrintStream& out, const CString& string) const
+{
+    out.print("%", string, ":", classInfo()->className);
+}

 
 

-    size_t enumerableCount = p - sortedEnumerables.data();
-    // Sort the entries by index.
-    qsort(sortedEnumerables.data(), enumerableCount, sizeof(PropertyMapEntry*), comparePropertyMapEntryIndices);
-    sortedEnumerables.resize(enumerableCount);
-
-    // Put the keys of the sorted entries into the list.
-    if (!propertyNames.size()) {
-        for (size_t i = 0; i < sortedEnumerables.size(); ++i)
-            propertyNames.addKnownUnique(sortedEnumerables[i]->key);
-    } else {
-        for (size_t i = 0; i < sortedEnumerables.size(); ++i)
-            propertyNames.add(sortedEnumerables[i]->key);
-    }
+void Structure::dumpContextHeader(PrintStream& out)
+{
+    out.print("Structures:");

 }
 
 #if DO_PROPERTYMAP_CONSTENCY_CHECK
 
 }
 
 #if DO_PROPERTYMAP_CONSTENCY_CHECK
 

-void Structure::checkConsistency()
+void PropertyTable::checkConsistency()

 {
 {

-    if (!m_propertyTable)
-        return;
-
-    ASSERT(m_propertyTable->size >= newTableSize);
-    ASSERT(m_propertyTable->sizeMask);
-    ASSERT(m_propertyTable->size == m_propertyTable->sizeMask + 1);
-    ASSERT(!(m_propertyTable->size & m_propertyTable->sizeMask));
-
-    ASSERT(m_propertyTable->keyCount <= m_propertyTable->size / 2);
-    ASSERT(m_propertyTable->deletedSentinelCount <= m_propertyTable->size / 4);
+    ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
+    ASSERT(m_indexMask);
+    ASSERT(m_indexSize == m_indexMask + 1);
+    ASSERT(!(m_indexSize & m_indexMask));

 
 

-    ASSERT(m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount <= m_propertyTable->size / 2);
+    ASSERT(m_keyCount <= m_indexSize / 2);
+    ASSERT(m_keyCount + m_deletedCount <= m_indexSize / 2);
+    ASSERT(m_deletedCount <= m_indexSize / 4);

 
     unsigned indexCount = 0;
     unsigned deletedIndexCount = 0;
 
     unsigned indexCount = 0;
     unsigned deletedIndexCount = 0;

-    for (unsigned a = 0; a != m_propertyTable->size; ++a) {
-        unsigned entryIndex = m_propertyTable->entryIndices[a];
-        if (entryIndex == emptyEntryIndex)
+    for (unsigned a = 0; a != m_indexSize; ++a) {
+        unsigned entryIndex = m_index[a];
+        if (entryIndex == PropertyTable::EmptyEntryIndex)

             continue;
             continue;

-        if (entryIndex == deletedSentinelIndex) {
+        if (entryIndex == deletedEntryIndex()) {

             ++deletedIndexCount;
             continue;
         }
             ++deletedIndexCount;
             continue;
         }

-        ASSERT(entryIndex > deletedSentinelIndex);
-        ASSERT(entryIndex - 1 <= m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount);
+        ASSERT(entryIndex < deletedEntryIndex());
+        ASSERT(entryIndex - 1 <= usedCount());

         ++indexCount;
 
         ++indexCount;
 

-        for (unsigned b = a + 1; b != m_propertyTable->size; ++b)
-            ASSERT(m_propertyTable->entryIndices[b] != entryIndex);
+        for (unsigned b = a + 1; b != m_indexSize; ++b)
+            ASSERT(m_index[b] != entryIndex);

     }
     }

-    ASSERT(indexCount == m_propertyTable->keyCount);
-    ASSERT(deletedIndexCount == m_propertyTable->deletedSentinelCount);
+    ASSERT(indexCount == m_keyCount);
+    ASSERT(deletedIndexCount == m_deletedCount);

 
 

-    ASSERT(m_propertyTable->entries()[0].key == 0);
+    ASSERT(!table()[deletedEntryIndex() - 1].key);

 
     unsigned nonEmptyEntryCount = 0;
 
     unsigned nonEmptyEntryCount = 0;

-    for (unsigned c = 1; c <= m_propertyTable->keyCount + m_propertyTable->deletedSentinelCount; ++c) {
-        ASSERT(m_hasNonEnumerableProperties || !(m_propertyTable->entries()[c].attributes & DontEnum));
-        UString::Rep* rep = m_propertyTable->entries()[c].key;
-        ASSERT(m_propertyTable->entries()[c].offset >= m_anonymousSlotCount);
-        if (!rep)
+    for (unsigned c = 0; c < usedCount(); ++c) {
+        StringImpl* rep = table()[c].key;
+        if (rep == PROPERTY_MAP_DELETED_ENTRY_KEY)

             continue;
         ++nonEmptyEntryCount;
             continue;
         ++nonEmptyEntryCount;

-        unsigned i = rep->existingHash();
+        unsigned i = IdentifierRepHash::hash(rep);

         unsigned k = 0;
         unsigned entryIndex;
         while (1) {
         unsigned k = 0;
         unsigned entryIndex;
         while (1) {

-            entryIndex = m_propertyTable->entryIndices[i & m_propertyTable->sizeMask];
-            ASSERT(entryIndex != emptyEntryIndex);
-            if (rep == m_propertyTable->entries()[entryIndex - 1].key)
+            entryIndex = m_index[i & m_indexMask];
+            ASSERT(entryIndex != PropertyTable::EmptyEntryIndex);
+            if (rep == table()[entryIndex - 1].key)

                 break;
             if (k == 0)
                 break;
             if (k == 0)

-                k = 1 | doubleHash(rep->existingHash());
+                k = 1 | doubleHash(IdentifierRepHash::hash(rep));

             i += k;
         }
         ASSERT(entryIndex == c + 1);
     }
 
             i += k;
         }
         ASSERT(entryIndex == c + 1);
     }
 

-    ASSERT(nonEmptyEntryCount == m_propertyTable->keyCount);
+    ASSERT(nonEmptyEntryCount == m_keyCount);
+}
+
+void Structure::checkConsistency()
+{
+    checkOffsetConsistency();
+
+    if (!propertyTable())
+        return;
+
+    if (!hasNonEnumerableProperties()) {
+        PropertyTable::iterator end = propertyTable()->end();
+        for (PropertyTable::iterator iter = propertyTable()->begin(); iter != end; ++iter) {
+            ASSERT(!(iter->attributes & DontEnum));
+        }
+    }
+
+    propertyTable()->checkConsistency();
+}
+
+#else
+
+inline void Structure::checkConsistency()
+{
+    checkOffsetConsistency();

 }
 
 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
 
 }
 
 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
 

+bool ClassInfo::hasStaticSetterOrReadonlyProperties() const
+{
+    for (const ClassInfo* ci = this; ci; ci = ci->parentClass) {
+        if (const HashTable* table = ci->staticPropHashTable) {
+            if (table->hasSetterOrReadonlyProperties)
+                return true;
+        }
+    }
+    return false;
+}
+
+void Structure::setCachedPropertyNameEnumerator(VM& vm, JSPropertyNameEnumerator* enumerator)
+{
+    ASSERT(!isDictionary());
+    if (!hasRareData())
+        allocateRareData(vm);
+    rareData()->setCachedPropertyNameEnumerator(vm, enumerator);
+}
+
+JSPropertyNameEnumerator* Structure::cachedPropertyNameEnumerator() const
+{
+    if (!hasRareData())
+        return nullptr;
+    return rareData()->cachedPropertyNameEnumerator();
+}
+
+bool Structure::canCachePropertyNameEnumerator() const
+{
+    if (isDictionary())
+        return false;
+
+    if (hasIndexedProperties(indexingType()))
+        return false;
+
+    if (typeInfo().overridesGetPropertyNames())
+        return false;
+
+    StructureChain* structureChain = m_cachedPrototypeChain.get();
+    ASSERT(structureChain);
+    WriteBarrier<Structure>* structure = structureChain->head();
+    while (true) {
+        if (!structure->get())
+            break;
+        if (structure->get()->typeInfo().overridesGetPropertyNames())
+            return false;
+        structure++;
+    }
+    
+    return true;
+}
+    
+bool Structure::canAccessPropertiesQuickly() const
+{
+    if (hasNonEnumerableProperties())
+        return false;
+    if (hasGetterSetterProperties())
+        return false;
+    if (isUncacheableDictionary())
+        return false;
+    return true;
+}
+

 } // namespace JSC
 } // namespace JSC