X-Git-Url: https://git.saurik.com/apple/javascriptcore.git/blobdiff_plain/4be4e30906bcb8ee30b4d189205cb70bad6707ce..81345200c95645a1b0d2635520f96ad55dfde63f:/runtime/JSObject.cpp

diff --git a/runtime/JSObject.cpp b/runtime/JSObject.cpp
index d18b4e2..4bd6a6e 100644
--- a/runtime/JSObject.cpp
+++ b/runtime/JSObject.cpp
@@ -28,6 +28,7 @@
 #include "CopiedSpaceInlines.h"
 #include "CopyVisitor.h"
 #include "CopyVisitorInlines.h"
+#include "CustomGetterSetter.h"
 #include "DatePrototype.h"
 #include "ErrorConstructor.h"
 #include "Executable.h"
@@ -39,7 +40,7 @@
 #include "NativeErrorConstructor.h"
 #include "Nodes.h"
 #include "ObjectPrototype.h"
-#include "Operations.h"
+#include "JSCInlines.h"
 #include "PropertyDescriptor.h"
 #include "PropertyNameArray.h"
 #include "Reject.h"
@@ -57,16 +58,15 @@ static unsigned lastArraySize = 0;
 
 JSCell* getCallableObjectSlow(JSCell* cell)
 {
-    Structure* structure = cell->structure();
-    if (structure->typeInfo().type() == JSFunctionType)
+    if (cell->type() == JSFunctionType)
         return cell;
-    if (structure->classInfo()->isSubClassOf(&InternalFunction::s_info))
+    if (cell->structure()->classInfo()->isSubClassOf(InternalFunction::info()))
         return cell;
     return 0;
 }
 
-ASSERT_HAS_TRIVIAL_DESTRUCTOR(JSObject);
-ASSERT_HAS_TRIVIAL_DESTRUCTOR(JSFinalObject);
+STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(JSObject);
+STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(JSFinalObject);
 
 const char* StrictModeReadonlyPropertyWriteError = "Attempted to assign to readonly property.";
 
@@ -76,19 +76,17 @@ const ClassInfo JSFinalObject::s_info = { "Object", &Base::s_info, 0, 0, CREATE_
 
 static inline void getClassPropertyNames(ExecState* exec, const ClassInfo* classInfo, PropertyNameArray& propertyNames, EnumerationMode mode, bool didReify)
 {
+    VM& vm = exec->vm();
+
     // Add properties from the static hashtables of properties
     for (; classInfo; classInfo = classInfo->parentClass) {
-        const HashTable* table = classInfo->propHashTable(exec);
+        const HashTable* table = classInfo->propHashTable(vm);
         if (!table)
             continue;
-        table->initializeIfNeeded(exec);
-        ASSERT(table->table);
-
-        int hashSizeMask = table->compactSize - 1;
-        const HashEntry* entry = table->table;
-        for (int i = 0; i <= hashSizeMask; ++i, ++entry) {
-            if (entry->key() && (!(entry->attributes() & DontEnum) || (mode == IncludeDontEnumProperties)) && !((entry->attributes() & Function) && didReify))
-                propertyNames.add(entry->key());
+
+        for (auto iter = table->begin(vm); iter != table->end(vm); ++iter) {
+            if ((!(iter->attributes() & DontEnum) || (mode == IncludeDontEnumProperties)) && !((iter->attributes() & BuiltinOrFunction) && didReify))
+                propertyNames.add(Identifier(&vm, iter.key()));
         }
     }
 }
@@ -102,7 +100,7 @@ ALWAYS_INLINE void JSObject::copyButterfly(CopyVisitor& visitor, Butterfly* butt
     size_t propertyCapacity = structure->outOfLineCapacity();
     size_t preCapacity;
     size_t indexingPayloadSizeInBytes;
-    bool hasIndexingHeader = JSC::hasIndexingHeader(structure->indexingType());
+    bool hasIndexingHeader = this->hasIndexingHeader();
     if (UNLIKELY(hasIndexingHeader)) {
         preCapacity = butterfly->indexingHeader()->preCapacity(structure);
         indexingPayloadSizeInBytes = butterfly->indexingHeader()->indexingPayloadSizeInBytes(structure);
@@ -129,7 +127,7 @@ ALWAYS_INLINE void JSObject::copyButterfly(CopyVisitor& visitor, Butterfly* butt
             WriteBarrier<Unknown>* currentSource;
             size_t count;
             
-            switch (structure->indexingType()) {
+            switch (this->indexingType()) {
             case ALL_UNDECIDED_INDEXING_TYPES:
             case ALL_CONTIGUOUS_INDEXING_TYPES:
             case ALL_INT32_INDEXING_TYPES:
@@ -148,8 +146,8 @@ ALWAYS_INLINE void JSObject::copyButterfly(CopyVisitor& visitor, Butterfly* butt
                 count = newButterfly->arrayStorage()->vectorLength();
                 break;
             }
+                
             default:
-                CRASH();
                 currentTarget = 0;
                 currentSource = 0;
                 count = 0;
@@ -159,7 +157,7 @@ ALWAYS_INLINE void JSObject::copyButterfly(CopyVisitor& visitor, Butterfly* butt
             memcpy(currentTarget, currentSource, count * sizeof(EncodedJSValue));
         }
         
-        m_butterfly = newButterfly;
+        m_butterfly.setWithoutWriteBarrier(newButterfly);
         visitor.didCopy(butterfly->base(preCapacity, propertyCapacity), capacityInBytes);
     } 
 }
@@ -168,12 +166,12 @@ ALWAYS_INLINE void JSObject::visitButterfly(SlotVisitor& visitor, Butterfly* but
 {
     ASSERT(butterfly);
     
-    Structure* structure = this->structure();
+    Structure* structure = this->structure(visitor.vm());
     
     size_t propertyCapacity = structure->outOfLineCapacity();
     size_t preCapacity;
     size_t indexingPayloadSizeInBytes;
-    bool hasIndexingHeader = JSC::hasIndexingHeader(structure->indexingType());
+    bool hasIndexingHeader = this->hasIndexingHeader();
     if (UNLIKELY(hasIndexingHeader)) {
         preCapacity = butterfly->indexingHeader()->preCapacity(structure);
         indexingPayloadSizeInBytes = butterfly->indexingHeader()->indexingPayloadSizeInBytes(structure);
@@ -185,10 +183,12 @@ ALWAYS_INLINE void JSObject::visitButterfly(SlotVisitor& visitor, Butterfly* but
 
     // Mark the properties.
     visitor.appendValues(butterfly->propertyStorage() - storageSize, storageSize);
-    visitor.copyLater(this, butterfly->base(preCapacity, propertyCapacity), capacityInBytes);
+    visitor.copyLater(
+        this, ButterflyCopyToken,
+        butterfly->base(preCapacity, propertyCapacity), capacityInBytes);
     
     // Mark the array if appropriate.
-    switch (structure->indexingType()) {
+    switch (this->indexingType()) {
     case ALL_CONTIGUOUS_INDEXING_TYPES:
         visitor.appendValues(butterfly->contiguous().data(), butterfly->publicLength());
         break;
@@ -205,7 +205,7 @@ ALWAYS_INLINE void JSObject::visitButterfly(SlotVisitor& visitor, Butterfly* but
 void JSObject::visitChildren(JSCell* cell, SlotVisitor& visitor)
 {
     JSObject* thisObject = jsCast<JSObject*>(cell);
-    ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
+    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
 #if !ASSERT_DISABLED
     bool wasCheckingForDefaultMarkViolation = visitor.m_isCheckingForDefaultMarkViolation;
     visitor.m_isCheckingForDefaultMarkViolation = false;
@@ -215,17 +215,20 @@ void JSObject::visitChildren(JSCell* cell, SlotVisitor& visitor)
 
     Butterfly* butterfly = thisObject->butterfly();
     if (butterfly)
-        thisObject->visitButterfly(visitor, butterfly, thisObject->structure()->outOfLineSize());
+        thisObject->visitButterfly(visitor, butterfly, thisObject->structure(visitor.vm())->outOfLineSize());
 
 #if !ASSERT_DISABLED
     visitor.m_isCheckingForDefaultMarkViolation = wasCheckingForDefaultMarkViolation;
 #endif
 }
 
-void JSObject::copyBackingStore(JSCell* cell, CopyVisitor& visitor)
+void JSObject::copyBackingStore(JSCell* cell, CopyVisitor& visitor, CopyToken token)
 {
     JSObject* thisObject = jsCast<JSObject*>(cell);
-    ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
+    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
+    
+    if (token != ButterflyCopyToken)
+        return;
     
     Butterfly* butterfly = thisObject->butterfly();
     if (butterfly)
@@ -235,7 +238,7 @@ void JSObject::copyBackingStore(JSCell* cell, CopyVisitor& visitor)
 void JSFinalObject::visitChildren(JSCell* cell, SlotVisitor& visitor)
 {
     JSFinalObject* thisObject = jsCast<JSFinalObject*>(cell);
-    ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
+    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
 #if !ASSERT_DISABLED
     bool wasCheckingForDefaultMarkViolation = visitor.m_isCheckingForDefaultMarkViolation;
     visitor.m_isCheckingForDefaultMarkViolation = false;
@@ -243,11 +246,12 @@ void JSFinalObject::visitChildren(JSCell* cell, SlotVisitor& visitor)
     
     JSCell::visitChildren(thisObject, visitor);
 
+    Structure* structure = thisObject->structure();
     Butterfly* butterfly = thisObject->butterfly();
     if (butterfly)
-        thisObject->visitButterfly(visitor, butterfly, thisObject->structure()->outOfLineSize());
+        thisObject->visitButterfly(visitor, butterfly, structure->outOfLineSize());
 
-    size_t storageSize = thisObject->structure()->inlineSize();
+    size_t storageSize = structure->inlineSize();
     visitor.appendValues(thisObject->inlineStorage(), storageSize);
 
 #if !ASSERT_DISABLED
@@ -262,31 +266,29 @@ String JSObject::className(const JSObject* object)
     return info->className;
 }
 
-bool JSObject::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned i, PropertySlot& slot)
+bool JSObject::getOwnPropertySlotByIndex(JSObject* thisObject, ExecState* exec, unsigned i, PropertySlot& slot)
 {
     // NB. The fact that we're directly consulting our indexed storage implies that it is not
     // legal for anyone to override getOwnPropertySlot() without also overriding
     // getOwnPropertySlotByIndex().
     
-    JSObject* thisObject = jsCast<JSObject*>(cell);
-    
     if (i > MAX_ARRAY_INDEX)
-        return thisObject->methodTable()->getOwnPropertySlot(thisObject, exec, Identifier::from(exec, i), slot);
+        return thisObject->methodTable(exec->vm())->getOwnPropertySlot(thisObject, exec, Identifier::from(exec, i), slot);
     
-    switch (thisObject->structure()->indexingType()) {
+    switch (thisObject->indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
     case ALL_UNDECIDED_INDEXING_TYPES:
         break;
         
     case ALL_INT32_INDEXING_TYPES:
     case ALL_CONTIGUOUS_INDEXING_TYPES: {
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (i >= butterfly->vectorLength())
             return false;
         
         JSValue value = butterfly->contiguous()[i].get();
         if (value) {
-            slot.setValue(value);
+            slot.setValue(thisObject, None, value);
             return true;
         }
         
@@ -294,13 +296,13 @@ bool JSObject::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned
     }
         
     case ALL_DOUBLE_INDEXING_TYPES: {
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (i >= butterfly->vectorLength())
             return false;
         
         double value = butterfly->contiguousDouble()[i];
         if (value == value) {
-            slot.setValue(JSValue(JSValue::EncodeAsDouble, value));
+            slot.setValue(thisObject, None, JSValue(JSValue::EncodeAsDouble, value));
             return true;
         }
         
@@ -315,13 +317,13 @@ bool JSObject::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned
         if (i < storage->vectorLength()) {
             JSValue value = storage->m_vector[i].get();
             if (value) {
-                slot.setValue(value);
+                slot.setValue(thisObject, None, value);
                 return true;
             }
         } else if (SparseArrayValueMap* map = storage->m_sparseMap.get()) {
             SparseArrayValueMap::iterator it = map->find(i);
             if (it != map->notFound()) {
-                it->value.get(slot);
+                it->value.get(thisObject, slot);
                 return true;
             }
         }
@@ -355,10 +357,10 @@ void JSObject::put(JSCell* cell, ExecState* exec, PropertyName propertyName, JSV
     // Check if there are any setters or getters in the prototype chain
     JSValue prototype;
     if (propertyName != exec->propertyNames().underscoreProto) {
-        for (JSObject* obj = thisObject; !obj->structure()->hasReadOnlyOrGetterSetterPropertiesExcludingProto(); obj = asObject(prototype)) {
+        for (JSObject* obj = thisObject; !obj->structure(vm)->hasReadOnlyOrGetterSetterPropertiesExcludingProto(); obj = asObject(prototype)) {
             prototype = obj->prototype();
             if (prototype.isNull()) {
-                ASSERT(!thisObject->structure()->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName));
+                ASSERT(!thisObject->structure(vm)->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName));
                 if (!thisObject->putDirectInternal<PutModePut>(vm, propertyName, value, 0, slot, getCallableObject(value))
                     && slot.isStrictMode())
                     throwTypeError(exec, ASCIILiteral(StrictModeReadonlyPropertyWriteError));
@@ -371,48 +373,46 @@ void JSObject::put(JSCell* cell, ExecState* exec, PropertyName propertyName, JSV
     for (obj = thisObject; ; obj = asObject(prototype)) {
         unsigned attributes;
         JSCell* specificValue;
-        PropertyOffset offset = obj->structure()->get(vm, propertyName, attributes, specificValue);
+        PropertyOffset offset = obj->structure(vm)->get(vm, propertyName, attributes, specificValue);
         if (isValidOffset(offset)) {
             if (attributes & ReadOnly) {
-                ASSERT(thisObject->structure()->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName) || obj == thisObject);
+                ASSERT(thisObject->structure(vm)->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName) || obj == thisObject);
                 if (slot.isStrictMode())
-                    throwError(exec, createTypeError(exec, ASCIILiteral(StrictModeReadonlyPropertyWriteError)));
+                    exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral(StrictModeReadonlyPropertyWriteError)));
                 return;
             }
 
             JSValue gs = obj->getDirect(offset);
             if (gs.isGetterSetter()) {
-                ASSERT(attributes & Accessor);
-                ASSERT(thisObject->structure()->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName) || obj == thisObject);
-                JSObject* setterFunc = asGetterSetter(gs)->setter();        
-                if (!setterFunc) {
-                    if (slot.isStrictMode())
-                        throwError(exec, createTypeError(exec, ASCIILiteral("setting a property that has only a getter")));
-                    return;
-                }
-                
-                CallData callData;
-                CallType callType = setterFunc->methodTable()->getCallData(setterFunc, callData);
-                MarkedArgumentBuffer args;
-                args.append(value);
-
-                // If this is WebCore's global object then we need to substitute the shell.
-                call(exec, setterFunc, callType, callData, thisObject->methodTable()->toThisObject(thisObject, exec), args);
+                callSetter(exec, cell, gs, value, slot.isStrictMode() ? StrictMode : NotStrictMode);
+                if (!thisObject->structure()->isDictionary())
+                    slot.setCacheableSetter(obj, offset);
                 return;
-            } else
-                ASSERT(!(attributes & Accessor));
+            }
+            if (gs.isCustomGetterSetter()) {
+                callCustomSetter(exec, gs, obj, slot.thisValue(), value);
+                slot.setCustomProperty(obj, jsCast<CustomGetterSetter*>(gs.asCell())->setter());
+                return;
+            }
+            ASSERT(!(attributes & Accessor));
 
             // If there's an existing property on the object or one of its 
             // prototypes it should be replaced, so break here.
             break;
         }
-
+        const ClassInfo* info = obj->classInfo();
+        if (info->hasStaticSetterOrReadonlyProperties(vm)) {
+            if (const HashTableValue* entry = obj->findPropertyHashEntry(vm, propertyName)) {
+                putEntry(exec, entry, obj, propertyName, value, slot);
+                return;
+            }
+        }
         prototype = obj->prototype();
         if (prototype.isNull())
             break;
     }
     
-    ASSERT(!thisObject->structure()->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName) || obj == thisObject);
+    ASSERT(!thisObject->structure(vm)->prototypeChainMayInterceptStoreTo(exec->vm(), propertyName) || obj == thisObject);
     if (!thisObject->putDirectInternal<PutModePut>(vm, propertyName, value, 0, slot, getCallableObject(value)) && slot.isStrictMode())
         throwTypeError(exec, ASCIILiteral(StrictModeReadonlyPropertyWriteError));
     return;
@@ -423,12 +423,12 @@ void JSObject::putByIndex(JSCell* cell, ExecState* exec, unsigned propertyName,
     JSObject* thisObject = jsCast<JSObject*>(cell);
     
     if (propertyName > MAX_ARRAY_INDEX) {
-        PutPropertySlot slot(shouldThrow);
+        PutPropertySlot slot(cell, shouldThrow);
         thisObject->methodTable()->put(thisObject, exec, Identifier::from(exec, propertyName), value, slot);
         return;
     }
     
-    switch (thisObject->structure()->indexingType()) {
+    switch (thisObject->indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
         break;
         
@@ -445,11 +445,11 @@ void JSObject::putByIndex(JSCell* cell, ExecState* exec, unsigned propertyName,
             putByIndex(cell, exec, propertyName, value, shouldThrow);
             return;
         }
-        // Fall through.
+        FALLTHROUGH;
     }
         
     case ALL_CONTIGUOUS_INDEXING_TYPES: {
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (propertyName >= butterfly->vectorLength())
             break;
         butterfly->contiguous()[propertyName].set(exec->vm(), thisObject, value);
@@ -472,7 +472,7 @@ void JSObject::putByIndex(JSCell* cell, ExecState* exec, unsigned propertyName,
             putByIndex(cell, exec, propertyName, value, shouldThrow);
             return;
         }
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (propertyName >= butterfly->vectorLength())
             break;
         butterfly->contiguousDouble()[propertyName] = valueAsDouble;
@@ -558,20 +558,20 @@ ArrayStorage* JSObject::enterDictionaryIndexingModeWhenArrayStorageAlreadyExists
             map->add(this, i).iterator->value.set(vm, this, value);
     }
 
-    Butterfly* newButterfly = storage->butterfly()->resizeArray(vm, structure(), 0, ArrayStorage::sizeFor(0));
+    DeferGC deferGC(vm.heap);
+    Butterfly* newButterfly = storage->butterfly()->resizeArray(vm, this, structure(vm), 0, ArrayStorage::sizeFor(0));
     RELEASE_ASSERT(newButterfly);
-    
-    m_butterfly = newButterfly;
     newButterfly->arrayStorage()->m_indexBias = 0;
     newButterfly->arrayStorage()->setVectorLength(0);
     newButterfly->arrayStorage()->m_sparseMap.set(vm, this, map);
+    setButterflyWithoutChangingStructure(vm, newButterfly);
     
     return newButterfly->arrayStorage();
 }
 
 void JSObject::enterDictionaryIndexingMode(VM& vm)
 {
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
     case ALL_UNDECIDED_INDEXING_TYPES:
     case ALL_INT32_INDEXING_TYPES:
@@ -595,7 +595,7 @@ void JSObject::notifyPresenceOfIndexedAccessors(VM& vm)
     if (mayInterceptIndexedAccesses())
         return;
     
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AddIndexedAccessors), m_butterfly);
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AddIndexedAccessors));
     
     if (!vm.prototypeMap.isPrototype(this))
         return;
@@ -606,13 +606,13 @@ void JSObject::notifyPresenceOfIndexedAccessors(VM& vm)
 Butterfly* JSObject::createInitialIndexedStorage(VM& vm, unsigned length, size_t elementSize)
 {
     ASSERT(length < MAX_ARRAY_INDEX);
-    IndexingType oldType = structure()->indexingType();
+    IndexingType oldType = indexingType();
     ASSERT_UNUSED(oldType, !hasIndexedProperties(oldType));
     ASSERT(!structure()->needsSlowPutIndexing());
     ASSERT(!indexingShouldBeSparse());
     unsigned vectorLength = std::max(length, BASE_VECTOR_LEN);
-    Butterfly* newButterfly = Butterfly::createOrGrowArrayRight(m_butterfly, 
-        vm, structure(), structure()->outOfLineCapacity(), false, 0,
+    Butterfly* newButterfly = Butterfly::createOrGrowArrayRight(
+        m_butterfly.get(), vm, this, structure(), structure()->outOfLineCapacity(), false, 0,
         elementSize * vectorLength);
     newButterfly->setPublicLength(length);
     newButterfly->setVectorLength(vectorLength);
@@ -621,44 +621,50 @@ Butterfly* JSObject::createInitialIndexedStorage(VM& vm, unsigned length, size_t
 
 Butterfly* JSObject::createInitialUndecided(VM& vm, unsigned length)
 {
+    DeferGC deferGC(vm.heap);
     Butterfly* newButterfly = createInitialIndexedStorage(vm, length, sizeof(EncodedJSValue));
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), AllocateUndecided);
-    setButterfly(vm, newButterfly, newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), AllocateUndecided);
+    setStructureAndButterfly(vm, newStructure, newButterfly);
     return newButterfly;
 }
 
 ContiguousJSValues JSObject::createInitialInt32(VM& vm, unsigned length)
 {
+    DeferGC deferGC(vm.heap);
     Butterfly* newButterfly = createInitialIndexedStorage(vm, length, sizeof(EncodedJSValue));
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), AllocateInt32);
-    setButterfly(vm, newButterfly, newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), AllocateInt32);
+    setStructureAndButterfly(vm, newStructure, newButterfly);
     return newButterfly->contiguousInt32();
 }
 
 ContiguousDoubles JSObject::createInitialDouble(VM& vm, unsigned length)
 {
+    DeferGC deferGC(vm.heap);
     Butterfly* newButterfly = createInitialIndexedStorage(vm, length, sizeof(double));
     for (unsigned i = newButterfly->vectorLength(); i--;)
-        newButterfly->contiguousDouble()[i] = QNaN;
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), AllocateDouble);
-    setButterfly(vm, newButterfly, newStructure);
+        newButterfly->contiguousDouble()[i] = PNaN;
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), AllocateDouble);
+    setStructureAndButterfly(vm, newStructure, newButterfly);
     return newButterfly->contiguousDouble();
 }
 
 ContiguousJSValues JSObject::createInitialContiguous(VM& vm, unsigned length)
 {
+    DeferGC deferGC(vm.heap);
     Butterfly* newButterfly = createInitialIndexedStorage(vm, length, sizeof(EncodedJSValue));
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), AllocateContiguous);
-    setButterfly(vm, newButterfly, newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), AllocateContiguous);
+    setStructureAndButterfly(vm, newStructure, newButterfly);
     return newButterfly->contiguous();
 }
 
 ArrayStorage* JSObject::createArrayStorage(VM& vm, unsigned length, unsigned vectorLength)
 {
-    IndexingType oldType = structure()->indexingType();
+    DeferGC deferGC(vm.heap);
+    Structure* structure = this->structure(vm);
+    IndexingType oldType = indexingType();
     ASSERT_UNUSED(oldType, !hasIndexedProperties(oldType));
-    Butterfly* newButterfly = Butterfly::createOrGrowArrayRight(m_butterfly, 
-        vm, structure(), structure()->outOfLineCapacity(), false, 0,
+    Butterfly* newButterfly = Butterfly::createOrGrowArrayRight(
+        m_butterfly.get(), vm, this, structure, structure->outOfLineCapacity(), false, 0,
         ArrayStorage::sizeFor(vectorLength));
     RELEASE_ASSERT(newButterfly);
 
@@ -668,8 +674,8 @@ ArrayStorage* JSObject::createArrayStorage(VM& vm, unsigned length, unsigned vec
     result->m_sparseMap.clear();
     result->m_numValuesInVector = 0;
     result->m_indexBias = 0;
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), structure()->suggestedArrayStorageTransition());
-    setButterfly(vm, newButterfly, newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure, structure->suggestedArrayStorageTransition());
+    setStructureAndButterfly(vm, newStructure, newButterfly);
     return result;
 }
 
@@ -680,37 +686,38 @@ ArrayStorage* JSObject::createInitialArrayStorage(VM& vm)
 
 ContiguousJSValues JSObject::convertUndecidedToInt32(VM& vm)
 {
-    ASSERT(hasUndecided(structure()->indexingType()));
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateInt32), m_butterfly);
+    ASSERT(hasUndecided(indexingType()));
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateInt32));
     return m_butterfly->contiguousInt32();
 }
 
 ContiguousDoubles JSObject::convertUndecidedToDouble(VM& vm)
 {
-    ASSERT(hasUndecided(structure()->indexingType()));
+    ASSERT(hasUndecided(indexingType()));
     
     for (unsigned i = m_butterfly->vectorLength(); i--;)
-        m_butterfly->contiguousDouble()[i] = QNaN;
+        m_butterfly->contiguousDouble()[i] = PNaN;
     
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateDouble), m_butterfly);
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateDouble));
     return m_butterfly->contiguousDouble();
 }
 
 ContiguousJSValues JSObject::convertUndecidedToContiguous(VM& vm)
 {
-    ASSERT(hasUndecided(structure()->indexingType()));
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateContiguous), m_butterfly);
+    ASSERT(hasUndecided(indexingType()));
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateContiguous));
     return m_butterfly->contiguous();
 }
 
 ArrayStorage* JSObject::constructConvertedArrayStorageWithoutCopyingElements(VM& vm, unsigned neededLength)
 {
+    Structure* structure = this->structure(vm);
     unsigned publicLength = m_butterfly->publicLength();
-    unsigned propertyCapacity = structure()->outOfLineCapacity();
-    unsigned propertySize = structure()->outOfLineSize();
+    unsigned propertyCapacity = structure->outOfLineCapacity();
+    unsigned propertySize = structure->outOfLineSize();
     
     Butterfly* newButterfly = Butterfly::createUninitialized(
-        vm, 0, propertyCapacity, true, ArrayStorage::sizeFor(neededLength));
+        vm, this, 0, propertyCapacity, true, ArrayStorage::sizeFor(neededLength));
     
     memcpy(
         newButterfly->propertyStorage() - propertySize,
@@ -729,13 +736,14 @@ ArrayStorage* JSObject::constructConvertedArrayStorageWithoutCopyingElements(VM&
 
 ArrayStorage* JSObject::convertUndecidedToArrayStorage(VM& vm, NonPropertyTransition transition, unsigned neededLength)
 {
-    ASSERT(hasUndecided(structure()->indexingType()));
+    DeferGC deferGC(vm.heap);
+    ASSERT(hasUndecided(indexingType()));
     
     ArrayStorage* storage = constructConvertedArrayStorageWithoutCopyingElements(vm, neededLength);
     // No need to copy elements.
     
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), transition);
-    setButterfly(vm, storage->butterfly(), newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), transition);
+    setStructureAndButterfly(vm, newStructure, storage->butterfly());
     return storage;
 }
 
@@ -746,41 +754,42 @@ ArrayStorage* JSObject::convertUndecidedToArrayStorage(VM& vm, NonPropertyTransi
 
 ArrayStorage* JSObject::convertUndecidedToArrayStorage(VM& vm)
 {
-    return convertUndecidedToArrayStorage(vm, structure()->suggestedArrayStorageTransition());
+    return convertUndecidedToArrayStorage(vm, structure(vm)->suggestedArrayStorageTransition());
 }
 
 ContiguousDoubles JSObject::convertInt32ToDouble(VM& vm)
 {
-    ASSERT(hasInt32(structure()->indexingType()));
+    ASSERT(hasInt32(indexingType()));
     
     for (unsigned i = m_butterfly->vectorLength(); i--;) {
         WriteBarrier<Unknown>* current = &m_butterfly->contiguousInt32()[i];
         double* currentAsDouble = bitwise_cast<double*>(current);
         JSValue v = current->get();
         if (!v) {
-            *currentAsDouble = QNaN;
+            *currentAsDouble = PNaN;
             continue;
         }
         ASSERT(v.isInt32());
         *currentAsDouble = v.asInt32();
     }
     
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateDouble), m_butterfly);
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateDouble));
     return m_butterfly->contiguousDouble();
 }
 
 ContiguousJSValues JSObject::convertInt32ToContiguous(VM& vm)
 {
-    ASSERT(hasInt32(structure()->indexingType()));
+    ASSERT(hasInt32(indexingType()));
     
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateContiguous), m_butterfly);
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateContiguous));
     return m_butterfly->contiguous();
 }
 
 ArrayStorage* JSObject::convertInt32ToArrayStorage(VM& vm, NonPropertyTransition transition, unsigned neededLength)
 {
-    ASSERT(hasInt32(structure()->indexingType()));
+    ASSERT(hasInt32(indexingType()));
     
+    DeferGC deferGC(vm.heap);
     ArrayStorage* newStorage = constructConvertedArrayStorageWithoutCopyingElements(vm, neededLength);
     for (unsigned i = m_butterfly->publicLength(); i--;) {
         JSValue v = m_butterfly->contiguous()[i].get();
@@ -790,8 +799,8 @@ ArrayStorage* JSObject::convertInt32ToArrayStorage(VM& vm, NonPropertyTransition
         newStorage->m_numValuesInVector++;
     }
     
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), transition);
-    setButterfly(vm, newStorage->butterfly(), newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), transition);
+    setStructureAndButterfly(vm, newStructure, newStorage->butterfly());
     return newStorage;
 }
 
@@ -802,13 +811,13 @@ ArrayStorage* JSObject::convertInt32ToArrayStorage(VM& vm, NonPropertyTransition
 
 ArrayStorage* JSObject::convertInt32ToArrayStorage(VM& vm)
 {
-    return convertInt32ToArrayStorage(vm, structure()->suggestedArrayStorageTransition());
+    return convertInt32ToArrayStorage(vm, structure(vm)->suggestedArrayStorageTransition());
 }
 
 template<JSObject::DoubleToContiguousMode mode>
 ContiguousJSValues JSObject::genericConvertDoubleToContiguous(VM& vm)
 {
-    ASSERT(hasDouble(structure()->indexingType()));
+    ASSERT(hasDouble(indexingType()));
     
     for (unsigned i = m_butterfly->vectorLength(); i--;) {
         double* current = &m_butterfly->contiguousDouble()[i];
@@ -826,12 +835,16 @@ ContiguousJSValues JSObject::genericConvertDoubleToContiguous(VM& vm)
         case RageConvertDoubleToValue:
             v = jsNumber(value);
             break;
+        default:
+            v = JSValue();
+            RELEASE_ASSERT_NOT_REACHED();
+            break;
         }
         ASSERT(v.isNumber());
         currentAsValue->setWithoutWriteBarrier(v);
     }
     
-    setStructure(vm, Structure::nonPropertyTransition(vm, structure(), AllocateContiguous), m_butterfly);
+    setStructure(vm, Structure::nonPropertyTransition(vm, structure(vm), AllocateContiguous));
     return m_butterfly->contiguous();
 }
 
@@ -847,7 +860,8 @@ ContiguousJSValues JSObject::rageConvertDoubleToContiguous(VM& vm)
 
 ArrayStorage* JSObject::convertDoubleToArrayStorage(VM& vm, NonPropertyTransition transition, unsigned neededLength)
 {
-    ASSERT(hasDouble(structure()->indexingType()));
+    DeferGC deferGC(vm.heap);
+    ASSERT(hasDouble(indexingType()));
     
     ArrayStorage* newStorage = constructConvertedArrayStorageWithoutCopyingElements(vm, neededLength);
     for (unsigned i = m_butterfly->publicLength(); i--;) {
@@ -858,8 +872,8 @@ ArrayStorage* JSObject::convertDoubleToArrayStorage(VM& vm, NonPropertyTransitio
         newStorage->m_numValuesInVector++;
     }
     
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), transition);
-    setButterfly(vm, newStorage->butterfly(), newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), transition);
+    setStructureAndButterfly(vm, newStructure, newStorage->butterfly());
     return newStorage;
 }
 
@@ -870,12 +884,13 @@ ArrayStorage* JSObject::convertDoubleToArrayStorage(VM& vm, NonPropertyTransitio
 
 ArrayStorage* JSObject::convertDoubleToArrayStorage(VM& vm)
 {
-    return convertDoubleToArrayStorage(vm, structure()->suggestedArrayStorageTransition());
+    return convertDoubleToArrayStorage(vm, structure(vm)->suggestedArrayStorageTransition());
 }
 
 ArrayStorage* JSObject::convertContiguousToArrayStorage(VM& vm, NonPropertyTransition transition, unsigned neededLength)
 {
-    ASSERT(hasContiguous(structure()->indexingType()));
+    DeferGC deferGC(vm.heap);
+    ASSERT(hasContiguous(indexingType()));
     
     ArrayStorage* newStorage = constructConvertedArrayStorageWithoutCopyingElements(vm, neededLength);
     for (unsigned i = m_butterfly->publicLength(); i--;) {
@@ -886,8 +901,8 @@ ArrayStorage* JSObject::convertContiguousToArrayStorage(VM& vm, NonPropertyTrans
         newStorage->m_numValuesInVector++;
     }
     
-    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), transition);
-    setButterfly(vm, newStorage->butterfly(), newStructure);
+    Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), transition);
+    setStructureAndButterfly(vm, newStructure, newStorage->butterfly());
     return newStorage;
 }
 
@@ -898,7 +913,7 @@ ArrayStorage* JSObject::convertContiguousToArrayStorage(VM& vm, NonPropertyTrans
 
 ArrayStorage* JSObject::convertContiguousToArrayStorage(VM& vm)
 {
-    return convertContiguousToArrayStorage(vm, structure()->suggestedArrayStorageTransition());
+    return convertContiguousToArrayStorage(vm, structure(vm)->suggestedArrayStorageTransition());
 }
 
 void JSObject::convertUndecidedForValue(VM& vm, JSValue value)
@@ -908,7 +923,7 @@ void JSObject::convertUndecidedForValue(VM& vm, JSValue value)
         return;
     }
     
-    if (value.isDouble()) {
+    if (value.isDouble() && value.asNumber() == value.asNumber()) {
         convertUndecidedToDouble(vm);
         return;
     }
@@ -916,6 +931,24 @@ void JSObject::convertUndecidedForValue(VM& vm, JSValue value)
     convertUndecidedToContiguous(vm);
 }
 
+void JSObject::createInitialForValueAndSet(VM& vm, unsigned index, JSValue value)
+{
+    if (value.isInt32()) {
+        createInitialInt32(vm, index + 1)[index].set(vm, this, value);
+        return;
+    }
+    
+    if (value.isDouble()) {
+        double doubleValue = value.asNumber();
+        if (doubleValue == doubleValue) {
+            createInitialDouble(vm, index + 1)[index] = doubleValue;
+            return;
+        }
+    }
+    
+    createInitialContiguous(vm, index + 1)[index].set(vm, this, value);
+}
+
 void JSObject::convertInt32ForValue(VM& vm, JSValue value)
 {
     ASSERT(!value.isInt32());
@@ -952,11 +985,11 @@ void JSObject::convertDoubleToContiguousWhilePerformingSetIndex(VM& vm, unsigned
 
 ContiguousJSValues JSObject::ensureInt32Slow(VM& vm)
 {
-    ASSERT(inherits(&s_info));
+    ASSERT(inherits(info()));
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
-        if (UNLIKELY(indexingShouldBeSparse() || structure()->needsSlowPutIndexing()))
+        if (UNLIKELY(indexingShouldBeSparse() || structure(vm)->needsSlowPutIndexing()))
             return ContiguousJSValues();
         return createInitialInt32(vm, 0);
         
@@ -976,11 +1009,11 @@ ContiguousJSValues JSObject::ensureInt32Slow(VM& vm)
 
 ContiguousDoubles JSObject::ensureDoubleSlow(VM& vm)
 {
-    ASSERT(inherits(&s_info));
+    ASSERT(inherits(info()));
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
-        if (UNLIKELY(indexingShouldBeSparse() || structure()->needsSlowPutIndexing()))
+        if (UNLIKELY(indexingShouldBeSparse() || structure(vm)->needsSlowPutIndexing()))
             return ContiguousDoubles();
         return createInitialDouble(vm, 0);
         
@@ -1002,11 +1035,11 @@ ContiguousDoubles JSObject::ensureDoubleSlow(VM& vm)
 
 ContiguousJSValues JSObject::ensureContiguousSlow(VM& vm, DoubleToContiguousMode mode)
 {
-    ASSERT(inherits(&s_info));
+    ASSERT(inherits(info()));
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
-        if (UNLIKELY(indexingShouldBeSparse() || structure()->needsSlowPutIndexing()))
+        if (UNLIKELY(indexingShouldBeSparse() || structure(vm)->needsSlowPutIndexing()))
             return ContiguousJSValues();
         return createInitialContiguous(vm, 0);
         
@@ -1042,9 +1075,9 @@ ContiguousJSValues JSObject::rageEnsureContiguousSlow(VM& vm)
 
 ArrayStorage* JSObject::ensureArrayStorageSlow(VM& vm)
 {
-    ASSERT(inherits(&s_info));
+    ASSERT(inherits(info()));
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
         if (UNLIKELY(indexingShouldBeSparse()))
             return ensureArrayStorageExistsAndEnterDictionaryIndexingMode(vm);
@@ -1052,22 +1085,22 @@ ArrayStorage* JSObject::ensureArrayStorageSlow(VM& vm)
         
     case ALL_UNDECIDED_INDEXING_TYPES:
         ASSERT(!indexingShouldBeSparse());
-        ASSERT(!structure()->needsSlowPutIndexing());
+        ASSERT(!structure(vm)->needsSlowPutIndexing());
         return convertUndecidedToArrayStorage(vm);
         
     case ALL_INT32_INDEXING_TYPES:
         ASSERT(!indexingShouldBeSparse());
-        ASSERT(!structure()->needsSlowPutIndexing());
+        ASSERT(!structure(vm)->needsSlowPutIndexing());
         return convertInt32ToArrayStorage(vm);
         
     case ALL_DOUBLE_INDEXING_TYPES:
         ASSERT(!indexingShouldBeSparse());
-        ASSERT(!structure()->needsSlowPutIndexing());
+        ASSERT(!structure(vm)->needsSlowPutIndexing());
         return convertDoubleToArrayStorage(vm);
         
     case ALL_CONTIGUOUS_INDEXING_TYPES:
         ASSERT(!indexingShouldBeSparse());
-        ASSERT(!structure()->needsSlowPutIndexing());
+        ASSERT(!structure(vm)->needsSlowPutIndexing());
         return convertContiguousToArrayStorage(vm);
         
     default:
@@ -1078,7 +1111,7 @@ ArrayStorage* JSObject::ensureArrayStorageSlow(VM& vm)
 
 ArrayStorage* JSObject::ensureArrayStorageExistsAndEnterDictionaryIndexingMode(VM& vm)
 {
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES: {
         createArrayStorage(vm, 0, 0);
         SparseArrayValueMap* map = allocateSparseIndexMap(vm);
@@ -1109,7 +1142,7 @@ ArrayStorage* JSObject::ensureArrayStorageExistsAndEnterDictionaryIndexingMode(V
 
 void JSObject::switchToSlowPutArrayStorage(VM& vm)
 {
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_UNDECIDED_INDEXING_TYPES:
         convertUndecidedToArrayStorage(vm, AllocateSlowPutArrayStorage);
         break;
@@ -1128,8 +1161,8 @@ void JSObject::switchToSlowPutArrayStorage(VM& vm)
         
     case NonArrayWithArrayStorage:
     case ArrayWithArrayStorage: {
-        Structure* newStructure = Structure::nonPropertyTransition(vm, structure(), SwitchToSlowPutArrayStorage);
-        setStructure(vm, newStructure, m_butterfly);
+        Structure* newStructure = Structure::nonPropertyTransition(vm, structure(vm), SwitchToSlowPutArrayStorage);
+        setStructure(vm, newStructure);
         break;
     }
         
@@ -1139,21 +1172,14 @@ void JSObject::switchToSlowPutArrayStorage(VM& vm)
     }
 }
 
-void JSObject::putDirectVirtual(JSObject* object, ExecState* exec, PropertyName propertyName, JSValue value, unsigned attributes)
-{
-    ASSERT(!value.isGetterSetter() && !(attributes & Accessor));
-    PutPropertySlot slot;
-    object->putDirectInternal<PutModeDefineOwnProperty>(exec->vm(), propertyName, value, attributes, slot, getCallableObject(value));
-}
-
 void JSObject::setPrototype(VM& vm, JSValue prototype)
 {
     ASSERT(prototype);
     if (prototype.isObject())
         vm.prototypeMap.addPrototype(asObject(prototype));
     
-    Structure* newStructure = Structure::changePrototypeTransition(vm, structure(), prototype);
-    setStructure(vm, newStructure, m_butterfly);
+    Structure* newStructure = Structure::changePrototypeTransition(vm, structure(vm), prototype);
+    setStructure(vm, newStructure);
     
     if (!newStructure->anyObjectInChainMayInterceptIndexedAccesses())
         return;
@@ -1163,28 +1189,25 @@ void JSObject::setPrototype(VM& vm, JSValue prototype)
         return;
     }
     
-    if (!hasIndexingHeader(structure()->indexingType()))
+    if (!hasIndexedProperties(indexingType()))
         return;
     
-    if (shouldUseSlowPut(structure()->indexingType()))
+    if (shouldUseSlowPut(indexingType()))
         return;
     
     switchToSlowPutArrayStorage(vm);
 }
 
-bool JSObject::setPrototypeWithCycleCheck(VM& vm, JSValue prototype)
+bool JSObject::setPrototypeWithCycleCheck(ExecState* exec, JSValue prototype)
 {
-    JSValue checkFor = this;
-    if (this->isGlobalObject())
-        checkFor = jsCast<JSGlobalObject*>(this)->globalExec()->thisValue();
-
+    ASSERT(methodTable(exec->vm())->toThis(this, exec, NotStrictMode) == this);
     JSValue nextPrototype = prototype;
     while (nextPrototype && nextPrototype.isObject()) {
-        if (nextPrototype == checkFor)
+        if (nextPrototype == this)
             return false;
         nextPrototype = asObject(nextPrototype)->prototype();
     }
-    setPrototype(vm, prototype);
+    setPrototype(exec->vm(), prototype);
     return true;
 }
 
@@ -1204,32 +1227,51 @@ void JSObject::putDirectAccessor(ExecState* exec, PropertyName propertyName, JSV
         return;
     }
 
-    VM& vm = exec->vm();
+    putDirectNonIndexAccessor(exec->vm(), propertyName, value, attributes);
+}
 
-    PutPropertySlot slot;
+void JSObject::putDirectCustomAccessor(VM& vm, PropertyName propertyName, JSValue value, unsigned attributes)
+{
+    ASSERT(propertyName.asIndex() == PropertyName::NotAnIndex);
+
+    PutPropertySlot slot(this);
+    putDirectInternal<PutModeDefineOwnProperty>(vm, propertyName, value, attributes, slot, getCallableObject(value));
+
+    ASSERT(slot.type() == PutPropertySlot::NewProperty);
+
+    Structure* structure = this->structure(vm);
+    if (attributes & ReadOnly)
+        structure->setContainsReadOnlyProperties();
+    structure->setHasCustomGetterSetterProperties(propertyName == vm.propertyNames->underscoreProto);
+}
+
+void JSObject::putDirectNonIndexAccessor(VM& vm, PropertyName propertyName, JSValue value, unsigned attributes)
+{
+    PutPropertySlot slot(this);
     putDirectInternal<PutModeDefineOwnProperty>(vm, propertyName, value, attributes, slot, getCallableObject(value));
 
     // putDirect will change our Structure if we add a new property. For
     // getters and setters, though, we also need to change our Structure
     // if we override an existing non-getter or non-setter.
     if (slot.type() != PutPropertySlot::NewProperty)
-        setStructure(vm, Structure::attributeChangeTransition(vm, structure(), propertyName, attributes), m_butterfly);
+        setStructure(vm, Structure::attributeChangeTransition(vm, structure(vm), propertyName, attributes));
 
+    Structure* structure = this->structure(vm);
     if (attributes & ReadOnly)
-        structure()->setContainsReadOnlyProperties();
+        structure->setContainsReadOnlyProperties();
 
-    structure()->setHasGetterSetterProperties(propertyName == vm.propertyNames->underscoreProto);
+    structure->setHasGetterSetterProperties(propertyName == vm.propertyNames->underscoreProto);
 }
 
 bool JSObject::hasProperty(ExecState* exec, PropertyName propertyName) const
 {
-    PropertySlot slot;
+    PropertySlot slot(this);
     return const_cast<JSObject*>(this)->getPropertySlot(exec, propertyName, slot);
 }
 
 bool JSObject::hasProperty(ExecState* exec, unsigned propertyName) const
 {
-    PropertySlot slot;
+    PropertySlot slot(this);
     return const_cast<JSObject*>(this)->getPropertySlot(exec, propertyName, slot);
 }
 
@@ -1240,27 +1282,29 @@ bool JSObject::deleteProperty(JSCell* cell, ExecState* exec, PropertyName proper
     
     unsigned i = propertyName.asIndex();
     if (i != PropertyName::NotAnIndex)
-        return thisObject->methodTable()->deletePropertyByIndex(thisObject, exec, i);
+        return thisObject->methodTable(exec->vm())->deletePropertyByIndex(thisObject, exec, i);
 
     if (!thisObject->staticFunctionsReified())
         thisObject->reifyStaticFunctionsForDelete(exec);
 
     unsigned attributes;
     JSCell* specificValue;
-    if (isValidOffset(thisObject->structure()->get(exec->vm(), propertyName, attributes, specificValue))) {
-        if (attributes & DontDelete && !exec->vm().isInDefineOwnProperty())
+    VM& vm = exec->vm();
+    if (isValidOffset(thisObject->structure(vm)->get(vm, propertyName, attributes, specificValue))) {
+        if (attributes & DontDelete && !vm.isInDefineOwnProperty())
             return false;
-        thisObject->removeDirect(exec->vm(), propertyName);
+        thisObject->removeDirect(vm, propertyName);
         return true;
     }
 
     // Look in the static hashtable of properties
-    const HashEntry* entry = thisObject->findPropertyHashEntry(exec, propertyName);
+    const HashTableValue* entry = thisObject->findPropertyHashEntry(vm, propertyName);
     if (entry) {
-        if (entry->attributes() & DontDelete && !exec->vm().isInDefineOwnProperty())
+        if (entry->attributes() & DontDelete && !vm.isInDefineOwnProperty())
             return false; // this builtin property can't be deleted
 
-        putEntry(exec, entry, propertyName, jsUndefined(), thisObject);
+        PutPropertySlot slot(thisObject);
+        putEntry(exec, entry, thisObject, propertyName, jsUndefined(), slot);
     }
 
     return true;
@@ -1268,8 +1312,8 @@ bool JSObject::deleteProperty(JSCell* cell, ExecState* exec, PropertyName proper
 
 bool JSObject::hasOwnProperty(ExecState* exec, PropertyName propertyName) const
 {
-    PropertySlot slot;
-    return const_cast<JSObject*>(this)->methodTable()->getOwnPropertySlot(const_cast<JSObject*>(this), exec, propertyName, slot);
+    PropertySlot slot(this);
+    return const_cast<JSObject*>(this)->methodTable(exec->vm())->getOwnPropertySlot(const_cast<JSObject*>(this), exec, propertyName, slot);
 }
 
 bool JSObject::deletePropertyByIndex(JSCell* cell, ExecState* exec, unsigned i)
@@ -1277,16 +1321,16 @@ bool JSObject::deletePropertyByIndex(JSCell* cell, ExecState* exec, unsigned i)
     JSObject* thisObject = jsCast<JSObject*>(cell);
     
     if (i > MAX_ARRAY_INDEX)
-        return thisObject->methodTable()->deleteProperty(thisObject, exec, Identifier::from(exec, i));
+        return thisObject->methodTable(exec->vm())->deleteProperty(thisObject, exec, Identifier::from(exec, i));
     
-    switch (thisObject->structure()->indexingType()) {
+    switch (thisObject->indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
     case ALL_UNDECIDED_INDEXING_TYPES:
         return true;
         
     case ALL_INT32_INDEXING_TYPES:
     case ALL_CONTIGUOUS_INDEXING_TYPES: {
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (i >= butterfly->vectorLength())
             return true;
         butterfly->contiguous()[i].clear();
@@ -1294,10 +1338,10 @@ bool JSObject::deletePropertyByIndex(JSCell* cell, ExecState* exec, unsigned i)
     }
         
     case ALL_DOUBLE_INDEXING_TYPES: {
-        Butterfly* butterfly = thisObject->m_butterfly;
+        Butterfly* butterfly = thisObject->butterfly();
         if (i >= butterfly->vectorLength())
             return true;
-        butterfly->contiguousDouble()[i] = QNaN;
+        butterfly->contiguousDouble()[i] = PNaN;
         return true;
     }
         
@@ -1352,7 +1396,7 @@ static ALWAYS_INLINE JSValue callDefaultValueFunction(ExecState* exec, const JSO
 
 bool JSObject::getPrimitiveNumber(ExecState* exec, double& number, JSValue& result) const
 {
-    result = methodTable()->defaultValue(this, exec, PreferNumber);
+    result = methodTable(exec->vm())->defaultValue(this, exec, PreferNumber);
     number = result.toNumber(exec);
     return !result.isString();
 }
@@ -1379,14 +1423,14 @@ JSValue JSObject::defaultValue(const JSObject* object, ExecState* exec, Preferre
 
     ASSERT(!exec->hadException());
 
-    return throwError(exec, createTypeError(exec, ASCIILiteral("No default value")));
+    return exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("No default value")));
 }
 
-const HashEntry* JSObject::findPropertyHashEntry(ExecState* exec, PropertyName propertyName) const
+const HashTableValue* JSObject::findPropertyHashEntry(VM& vm, PropertyName propertyName) const
 {
     for (const ClassInfo* info = classInfo(); info; info = info->parentClass) {
-        if (const HashTable* propHashTable = info->propHashTable(exec)) {
-            if (const HashEntry* entry = propHashTable->entry(exec, propertyName))
+        if (const HashTable* propHashTable = info->propHashTable(vm)) {
+            if (const HashTableValue* entry = propHashTable->entry(vm, propertyName))
                 return entry;
         }
     }
@@ -1395,12 +1439,13 @@ const HashEntry* JSObject::findPropertyHashEntry(ExecState* exec, PropertyName p
 
 bool JSObject::hasInstance(ExecState* exec, JSValue value)
 {
-    TypeInfo info = structure()->typeInfo();
+    VM& vm = exec->vm();
+    TypeInfo info = structure(vm)->typeInfo();
     if (info.implementsDefaultHasInstance())
         return defaultHasInstance(exec, value, get(exec, exec->propertyNames().prototype));
     if (info.implementsHasInstance())
-        return methodTable()->customHasInstance(this, exec, value);
-    throwError(exec, createInvalidParamError(exec, "instanceof" , this));
+        return methodTable(vm)->customHasInstance(this, exec, value);
+    vm.throwException(exec, createInvalidParameterError(exec, "instanceof" , this));
     return false;
 }
 
@@ -1410,7 +1455,7 @@ bool JSObject::defaultHasInstance(ExecState* exec, JSValue value, JSValue proto)
         return false;
 
     if (!proto.isObject()) {
-        throwError(exec, createTypeError(exec, ASCIILiteral("instanceof called on an object with an invalid prototype property.")));
+        exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("instanceof called on an object with an invalid prototype property.")));
         return false;
     }
 
@@ -1422,18 +1467,11 @@ bool JSObject::defaultHasInstance(ExecState* exec, JSValue value, JSValue proto)
     return false;
 }
 
-bool JSObject::propertyIsEnumerable(ExecState* exec, const Identifier& propertyName) const
-{
-    PropertyDescriptor descriptor;
-    if (!const_cast<JSObject*>(this)->methodTable()->getOwnPropertyDescriptor(const_cast<JSObject*>(this), exec, propertyName, descriptor))
-        return false;
-    return descriptor.enumerable();
-}
-
 bool JSObject::getPropertySpecificValue(ExecState* exec, PropertyName propertyName, JSCell*& specificValue) const
 {
+    VM& vm = exec->vm();
     unsigned attributes;
-    if (isValidOffset(structure()->get(exec->vm(), propertyName, attributes, specificValue)))
+    if (isValidOffset(structure(vm)->get(vm, propertyName, attributes, specificValue)))
         return true;
 
     // This could be a function within the static table? - should probably
@@ -1446,18 +1484,19 @@ bool JSObject::getPropertySpecificValue(ExecState* exec, PropertyName propertyNa
 void JSObject::getPropertyNames(JSObject* object, ExecState* exec, PropertyNameArray& propertyNames, EnumerationMode mode)
 {
     propertyNames.setBaseObject(object);
-    object->methodTable()->getOwnPropertyNames(object, exec, propertyNames, mode);
+    object->methodTable(exec->vm())->getOwnPropertyNames(object, exec, propertyNames, mode);
 
     if (object->prototype().isNull())
         return;
 
+    VM& vm = exec->vm();
     JSObject* prototype = asObject(object->prototype());
     while(1) {
-        if (prototype->structure()->typeInfo().overridesGetPropertyNames()) {
-            prototype->methodTable()->getPropertyNames(prototype, exec, propertyNames, mode);
+        if (prototype->structure(vm)->typeInfo().overridesGetPropertyNames()) {
+            prototype->methodTable(vm)->getPropertyNames(prototype, exec, propertyNames, mode);
             break;
         }
-        prototype->methodTable()->getOwnPropertyNames(prototype, exec, propertyNames, mode);
+        prototype->methodTable(vm)->getOwnPropertyNames(prototype, exec, propertyNames, mode);
         JSValue nextProto = prototype->prototype();
         if (nextProto.isNull())
             break;
@@ -1471,14 +1510,14 @@ void JSObject::getOwnPropertyNames(JSObject* object, ExecState* exec, PropertyNa
     // FIXME: Filling PropertyNameArray with an identifier for every integer
     // is incredibly inefficient for large arrays. We need a different approach,
     // which almost certainly means a different structure for PropertyNameArray.
-    switch (object->structure()->indexingType()) {
+    switch (object->indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
     case ALL_UNDECIDED_INDEXING_TYPES:
         break;
         
     case ALL_INT32_INDEXING_TYPES:
     case ALL_CONTIGUOUS_INDEXING_TYPES: {
-        Butterfly* butterfly = object->m_butterfly;
+        Butterfly* butterfly = object->butterfly();
         unsigned usedLength = butterfly->publicLength();
         for (unsigned i = 0; i < usedLength; ++i) {
             if (!butterfly->contiguous()[i])
@@ -1489,7 +1528,7 @@ void JSObject::getOwnPropertyNames(JSObject* object, ExecState* exec, PropertyNa
     }
         
     case ALL_DOUBLE_INDEXING_TYPES: {
-        Butterfly* butterfly = object->m_butterfly;
+        Butterfly* butterfly = object->butterfly();
         unsigned usedLength = butterfly->publicLength();
         for (unsigned i = 0; i < usedLength; ++i) {
             double value = butterfly->contiguousDouble()[i];
@@ -1530,15 +1569,16 @@ void JSObject::getOwnPropertyNames(JSObject* object, ExecState* exec, PropertyNa
         RELEASE_ASSERT_NOT_REACHED();
     }
     
-    object->methodTable()->getOwnNonIndexPropertyNames(object, exec, propertyNames, mode);
+    object->methodTable(exec->vm())->getOwnNonIndexPropertyNames(object, exec, propertyNames, mode);
 }
 
 void JSObject::getOwnNonIndexPropertyNames(JSObject* object, ExecState* exec, PropertyNameArray& propertyNames, EnumerationMode mode)
 {
     getClassPropertyNames(exec, object->classInfo(), propertyNames, mode, object->staticFunctionsReified());
 
+    VM& vm = exec->vm();
     bool canCachePropertiesFromStructure = !propertyNames.size();
-    object->structure()->getPropertyNamesFromStructure(exec->vm(), propertyNames, mode);
+    object->structure(vm)->getPropertyNamesFromStructure(vm, propertyNames, mode);
 
     if (canCachePropertiesFromStructure)
         propertyNames.setNumCacheableSlotsForObject(object, propertyNames.size());
@@ -1560,7 +1600,7 @@ JSString* JSObject::toString(ExecState* exec) const
     return primitive.toString(exec);
 }
 
-JSObject* JSObject::toThisObject(JSCell* cell, ExecState*)
+JSValue JSObject::toThis(JSCell* cell, ExecState*, ECMAMode)
 {
     return jsCast<JSObject*>(cell);
 }
@@ -1570,7 +1610,7 @@ void JSObject::seal(VM& vm)
     if (isSealed(vm))
         return;
     preventExtensions(vm);
-    setStructure(vm, Structure::sealTransition(vm, structure()), m_butterfly);
+    setStructure(vm, Structure::sealTransition(vm, structure(vm)));
 }
 
 void JSObject::freeze(VM& vm)
@@ -1578,14 +1618,14 @@ void JSObject::freeze(VM& vm)
     if (isFrozen(vm))
         return;
     preventExtensions(vm);
-    setStructure(vm, Structure::freezeTransition(vm, structure()), m_butterfly);
+    setStructure(vm, Structure::freezeTransition(vm, structure(vm)));
 }
 
 void JSObject::preventExtensions(VM& vm)
 {
     enterDictionaryIndexingMode(vm);
     if (isExtensible())
-        setStructure(vm, Structure::preventExtensionsTransition(vm, structure()), m_butterfly);
+        setStructure(vm, Structure::preventExtensionsTransition(vm, structure(vm)));
 }
 
 // This presently will flatten to an uncachable dictionary; this is suitable
@@ -1598,66 +1638,67 @@ void JSObject::reifyStaticFunctionsForDelete(ExecState* exec)
     // If this object's ClassInfo has no static properties, then nothing to reify!
     // We can safely set the flag to avoid the expensive check again in the future.
     if (!classInfo()->hasStaticProperties()) {
-        structure()->setStaticFunctionsReified();
+        structure(vm)->setStaticFunctionsReified();
         return;
     }
 
-    if (!structure()->isUncacheableDictionary())
-        setStructure(vm, Structure::toUncacheableDictionaryTransition(vm, structure()), m_butterfly);
+    if (!structure(vm)->isUncacheableDictionary())
+        setStructure(vm, Structure::toUncacheableDictionaryTransition(vm, structure(vm)));
 
     for (const ClassInfo* info = classInfo(); info; info = info->parentClass) {
-        const HashTable* hashTable = info->propHashTable(globalObject()->globalExec());
+        const HashTable* hashTable = info->propHashTable(vm);
         if (!hashTable)
             continue;
-        PropertySlot slot;
-        for (HashTable::ConstIterator iter = hashTable->begin(vm); iter != hashTable->end(vm); ++iter) {
-            if (iter->attributes() & Function)
-                setUpStaticFunctionSlot(globalObject()->globalExec(), *iter, this, Identifier(&vm, iter->key()), slot);
+        PropertySlot slot(this);
+        for (auto iter = hashTable->begin(vm); iter != hashTable->end(vm); ++iter) {
+            if (iter->attributes() & BuiltinOrFunction)
+                setUpStaticFunctionSlot(globalObject()->globalExec(), iter.value(), this, Identifier(&vm, iter.key()), slot);
         }
     }
 
-    structure()->setStaticFunctionsReified();
+    structure(vm)->setStaticFunctionsReified();
 }
 
 bool JSObject::removeDirect(VM& vm, PropertyName propertyName)
 {
-    if (!isValidOffset(structure()->get(vm, propertyName)))
+    Structure* structure = this->structure(vm);
+    if (!isValidOffset(structure->get(vm, propertyName)))
         return false;
 
     PropertyOffset offset;
-    if (structure()->isUncacheableDictionary()) {
-        offset = structure()->removePropertyWithoutTransition(vm, propertyName);
+    if (structure->isUncacheableDictionary()) {
+        offset = structure->removePropertyWithoutTransition(vm, propertyName);
         if (offset == invalidOffset)
             return false;
         putDirectUndefined(offset);
         return true;
     }
 
-    setStructure(vm, Structure::removePropertyTransition(vm, structure(), propertyName, offset), m_butterfly);
+    setStructure(vm, Structure::removePropertyTransition(vm, structure, propertyName, offset));
     if (offset == invalidOffset)
         return false;
     putDirectUndefined(offset);
     return true;
 }
 
-NEVER_INLINE void JSObject::fillGetterPropertySlot(PropertySlot& slot, PropertyOffset offset)
+NEVER_INLINE void JSObject::fillGetterPropertySlot(PropertySlot& slot, JSValue getterSetter, unsigned attributes, PropertyOffset offset)
 {
-    if (JSObject* getterFunction = asGetterSetter(getDirect(offset))->getter()) {
-        if (!structure()->isDictionary())
-            slot.setCacheableGetterSlot(this, getterFunction, offset);
-        else
-            slot.setGetterSlot(getterFunction);
-    } else
-        slot.setUndefined();
+    if (structure()->isDictionary()) {
+        slot.setGetterSlot(this, attributes, jsCast<GetterSetter*>(getterSetter));
+        return;
+    }
+    slot.setCacheableGetterSlot(this, attributes, jsCast<GetterSetter*>(getterSetter), offset);
 }
 
-void JSObject::putIndexedDescriptor(ExecState* exec, SparseArrayEntry* entryInMap, PropertyDescriptor& descriptor, PropertyDescriptor& oldDescriptor)
+void JSObject::putIndexedDescriptor(ExecState* exec, SparseArrayEntry* entryInMap, const PropertyDescriptor& descriptor, PropertyDescriptor& oldDescriptor)
 {
+    VM& vm = exec->vm();
+
     if (descriptor.isDataDescriptor()) {
         if (descriptor.value())
-            entryInMap->set(exec->vm(), this, descriptor.value());
+            entryInMap->set(vm, this, descriptor.value());
         else if (oldDescriptor.isAccessorDescriptor())
-            entryInMap->set(exec->vm(), this, jsUndefined());
+            entryInMap->set(vm, this, jsUndefined());
         entryInMap->attributes = descriptor.attributesOverridingCurrent(oldDescriptor) & ~Accessor;
         return;
     }
@@ -1674,13 +1715,13 @@ void JSObject::putIndexedDescriptor(ExecState* exec, SparseArrayEntry* entryInMa
         else if (oldDescriptor.isAccessorDescriptor())
             setter = oldDescriptor.setterObject();
 
-        GetterSetter* accessor = GetterSetter::create(exec);
+        GetterSetter* accessor = GetterSetter::create(vm);
         if (getter)
-            accessor->setGetter(exec->vm(), getter);
+            accessor->setGetter(vm, getter);
         if (setter)
-            accessor->setSetter(exec->vm(), setter);
+            accessor->setSetter(vm, setter);
 
-        entryInMap->set(exec->vm(), this, accessor);
+        entryInMap->set(vm, this, accessor);
         entryInMap->attributes = descriptor.attributesOverridingCurrent(oldDescriptor) & ~ReadOnly;
         return;
     }
@@ -1690,7 +1731,7 @@ void JSObject::putIndexedDescriptor(ExecState* exec, SparseArrayEntry* entryInMa
 }
 
 // Defined in ES5.1 8.12.9
-bool JSObject::defineOwnIndexedProperty(ExecState* exec, unsigned index, PropertyDescriptor& descriptor, bool throwException)
+bool JSObject::defineOwnIndexedProperty(ExecState* exec, unsigned index, const PropertyDescriptor& descriptor, bool throwException)
 {
     ASSERT(index <= MAX_ARRAY_INDEX);
     
@@ -1861,7 +1902,7 @@ bool JSObject::attemptToInterceptPutByIndexOnHole(ExecState* exec, unsigned i, J
 template<IndexingType indexingShape>
 void JSObject::putByIndexBeyondVectorLengthWithoutAttributes(ExecState* exec, unsigned i, JSValue value)
 {
-    ASSERT((structure()->indexingType() & IndexingShapeMask) == indexingShape);
+    ASSERT((indexingType() & IndexingShapeMask) == indexingShape);
     ASSERT(!indexingShouldBeSparse());
     
     // For us to get here, the index is either greater than the public length, or greater than
@@ -1872,7 +1913,7 @@ void JSObject::putByIndexBeyondVectorLengthWithoutAttributes(ExecState* exec, un
     
     if (i >= MAX_ARRAY_INDEX - 1
         || (i >= MIN_SPARSE_ARRAY_INDEX
-            && !isDenseEnoughForVector(i, countElements<indexingShape>(m_butterfly)))
+            && !isDenseEnoughForVector(i, countElements<indexingShape>(butterfly())))
         || indexIsSufficientlyBeyondLengthForSparseMap(i, m_butterfly->vectorLength())) {
         ASSERT(i <= MAX_ARRAY_INDEX);
         ensureArrayStorageSlow(vm);
@@ -1990,7 +2031,7 @@ void JSObject::putByIndexBeyondVectorLength(ExecState* exec, unsigned i, JSValue
     // i should be a valid array index that is outside of the current vector.
     ASSERT(i <= MAX_ARRAY_INDEX);
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES: {
         if (indexingShouldBeSparse()) {
             putByIndexBeyondVectorLengthWithArrayStorage(
@@ -2003,14 +2044,14 @@ void JSObject::putByIndexBeyondVectorLength(ExecState* exec, unsigned i, JSValue
                 exec, i, value, shouldThrow, createArrayStorage(vm, 0, 0));
             break;
         }
-        if (structure()->needsSlowPutIndexing()) {
+        if (structure(vm)->needsSlowPutIndexing()) {
             ArrayStorage* storage = createArrayStorage(vm, i + 1, getNewVectorLength(0, 0, i + 1));
             storage->m_vector[i].set(vm, this, value);
             storage->m_numValuesInVector++;
             break;
         }
-            
-        createInitialContiguous(vm, i + 1)[i].set(vm, this, value);
+        
+        createInitialForValueAndSet(vm, i, value);
         break;
     }
         
@@ -2040,7 +2081,7 @@ void JSObject::putByIndexBeyondVectorLength(ExecState* exec, unsigned i, JSValue
         SparseArrayValueMap* map = arrayStorage()->m_sparseMap.get();
         if (!(map && map->contains(i)) && attemptToInterceptPutByIndexOnHole(exec, i, value, shouldThrow))
             return;
-        // Otherwise, fall though.
+        FALLTHROUGH;
     }
 
     case NonArrayWithArrayStorage:
@@ -2058,7 +2099,7 @@ bool JSObject::putDirectIndexBeyondVectorLengthWithArrayStorage(ExecState* exec,
     VM& vm = exec->vm();
     
     // i should be a valid array index that is outside of the current vector.
-    ASSERT(hasArrayStorage(structure()->indexingType()));
+    ASSERT(hasAnyArrayStorage(indexingType()));
     ASSERT(arrayStorage() == storage);
     ASSERT(i >= storage->vectorLength() || attributes);
     ASSERT(i <= MAX_ARRAY_INDEX);
@@ -2140,7 +2181,7 @@ bool JSObject::putDirectIndexBeyondVectorLength(ExecState* exec, unsigned i, JSV
     if (attributes & (ReadOnly | Accessor))
         notifyPresenceOfIndexedAccessors(vm);
     
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES: {
         if (indexingShouldBeSparse() || attributes) {
             return putDirectIndexBeyondVectorLengthWithArrayStorage(
@@ -2151,14 +2192,14 @@ bool JSObject::putDirectIndexBeyondVectorLength(ExecState* exec, unsigned i, JSV
             return putDirectIndexBeyondVectorLengthWithArrayStorage(
                 exec, i, value, attributes, mode, createArrayStorage(vm, 0, 0));
         }
-        if (structure()->needsSlowPutIndexing()) {
+        if (structure(vm)->needsSlowPutIndexing()) {
             ArrayStorage* storage = createArrayStorage(vm, i + 1, getNewVectorLength(0, 0, i + 1));
             storage->m_vector[i].set(vm, this, value);
             storage->m_numValuesInVector++;
             return true;
         }
         
-        createInitialContiguous(vm, i + 1)[i].set(vm, this, value);
+        createInitialForValueAndSet(vm, i, value);
         return true;
     }
         
@@ -2217,14 +2258,46 @@ bool JSObject::putDirectIndexBeyondVectorLength(ExecState* exec, unsigned i, JSV
     }
 }
 
-void JSObject::putDirectNativeFunction(ExecState* exec, JSGlobalObject* globalObject, const PropertyName& propertyName, unsigned functionLength, NativeFunction nativeFunction, Intrinsic intrinsic, unsigned attributes)
+void JSObject::putDirectNativeFunction(VM& vm, JSGlobalObject* globalObject, const PropertyName& propertyName, unsigned functionLength, NativeFunction nativeFunction, Intrinsic intrinsic, unsigned attributes)
 {
     StringImpl* name = propertyName.publicName();
+    if (!name)
+        name = vm.propertyNames->anonymous.impl();
     ASSERT(name);
-    
-    JSFunction* function =
-        JSFunction::create(exec, globalObject, functionLength, name, nativeFunction, intrinsic);
-    putDirect(exec->vm(), propertyName, function, attributes);
+
+    JSFunction* function = JSFunction::create(vm, globalObject, functionLength, name, nativeFunction, intrinsic);
+    putDirect(vm, propertyName, function, attributes);
+}
+
+JSFunction* JSObject::putDirectBuiltinFunction(VM& vm, JSGlobalObject* globalObject, const PropertyName& propertyName, FunctionExecutable* functionExecutable, unsigned attributes)
+{
+    StringImpl* name = propertyName.publicName();
+    if (!name)
+        name = vm.propertyNames->anonymous.impl();
+    ASSERT(name);
+    JSFunction* function = JSFunction::createBuiltinFunction(vm, static_cast<FunctionExecutable*>(functionExecutable), globalObject);
+    putDirect(vm, propertyName, function, attributes);
+    return function;
+}
+
+JSFunction* JSObject::putDirectBuiltinFunctionWithoutTransition(VM& vm, JSGlobalObject* globalObject, const PropertyName& propertyName, FunctionExecutable* functionExecutable, unsigned attributes)
+{
+    StringImpl* name = propertyName.publicName();
+    if (!name)
+        name = vm.propertyNames->anonymous.impl();
+    ASSERT(name);
+    JSFunction* function = JSFunction::createBuiltinFunction(vm, static_cast<FunctionExecutable*>(functionExecutable), globalObject);
+    putDirectWithoutTransition(vm, propertyName, function, attributes);
+    return function;
+}
+
+void JSObject::putDirectNativeFunctionWithoutTransition(VM& vm, JSGlobalObject* globalObject, const PropertyName& propertyName, unsigned functionLength, NativeFunction nativeFunction, Intrinsic intrinsic, unsigned attributes)
+{
+    StringImpl* name = propertyName.publicName();
+    ASSERT(name);
+
+    JSFunction* function = JSFunction::create(vm, globalObject, functionLength, name, nativeFunction, intrinsic);
+    putDirectWithoutTransition(vm, propertyName, function, attributes);
 }
 
 ALWAYS_INLINE unsigned JSObject::getNewVectorLength(unsigned currentVectorLength, unsigned currentLength, unsigned desiredLength)
@@ -2254,7 +2327,7 @@ ALWAYS_INLINE unsigned JSObject::getNewVectorLength(unsigned desiredLength)
     unsigned vectorLength;
     unsigned length;
     
-    if (hasIndexedProperties(structure()->indexingType())) {
+    if (hasIndexedProperties(indexingType())) {
         vectorLength = m_butterfly->vectorLength();
         length = m_butterfly->publicLength();
     } else {
@@ -2293,19 +2366,19 @@ unsigned JSObject::countElements(Butterfly* butterfly)
 
 unsigned JSObject::countElements()
 {
-    switch (structure()->indexingType()) {
+    switch (indexingType()) {
     case ALL_BLANK_INDEXING_TYPES:
     case ALL_UNDECIDED_INDEXING_TYPES:
         return 0;
         
     case ALL_INT32_INDEXING_TYPES:
-        return countElements<Int32Shape>(m_butterfly);
+        return countElements<Int32Shape>(butterfly());
         
     case ALL_DOUBLE_INDEXING_TYPES:
-        return countElements<DoubleShape>(m_butterfly);
+        return countElements<DoubleShape>(butterfly());
         
     case ALL_CONTIGUOUS_INDEXING_TYPES:
-        return countElements<ContiguousShape>(m_butterfly);
+        return countElements<ContiguousShape>(butterfly());
         
     default:
         CRASH();
@@ -2332,49 +2405,56 @@ bool JSObject::increaseVectorLength(VM& vm, unsigned newLength)
     unsigned newVectorLength = getNewVectorLength(newLength);
 
     // Fast case - there is no precapacity. In these cases a realloc makes sense.
+    Structure* structure = this->structure(vm);
     if (LIKELY(!indexBias)) {
-        Butterfly* newButterfly = storage->butterfly()->growArrayRight(vm, structure(), structure()->outOfLineCapacity(), true, ArrayStorage::sizeFor(vectorLength), ArrayStorage::sizeFor(newVectorLength));
+        DeferGC deferGC(vm.heap);
+        Butterfly* newButterfly = storage->butterfly()->growArrayRight(
+            vm, this, structure, structure->outOfLineCapacity(), true,
+            ArrayStorage::sizeFor(vectorLength), ArrayStorage::sizeFor(newVectorLength));
         if (!newButterfly)
             return false;
-        m_butterfly = newButterfly;
         newButterfly->arrayStorage()->setVectorLength(newVectorLength);
+        setButterflyWithoutChangingStructure(vm, newButterfly);
         return true;
     }
     
     // Remove some, but not all of the precapacity. Atomic decay, & capped to not overflow array length.
+    DeferGC deferGC(vm.heap);
     unsigned newIndexBias = std::min(indexBias >> 1, MAX_STORAGE_VECTOR_LENGTH - newVectorLength);
     Butterfly* newButterfly = storage->butterfly()->resizeArray(
-        vm,
-        structure()->outOfLineCapacity(), true, ArrayStorage::sizeFor(vectorLength),
+        vm, this,
+        structure->outOfLineCapacity(), true, ArrayStorage::sizeFor(vectorLength),
         newIndexBias, true, ArrayStorage::sizeFor(newVectorLength));
     if (!newButterfly)
         return false;
-    
-    m_butterfly = newButterfly;
     newButterfly->arrayStorage()->setVectorLength(newVectorLength);
     newButterfly->arrayStorage()->m_indexBias = newIndexBias;
+    setButterflyWithoutChangingStructure(vm, newButterfly);
     return true;
 }
 
 void JSObject::ensureLengthSlow(VM& vm, unsigned length)
 {
     ASSERT(length < MAX_ARRAY_INDEX);
-    ASSERT(hasContiguous(structure()->indexingType()) || hasInt32(structure()->indexingType()) || hasDouble(structure()->indexingType()) || hasUndecided(structure()->indexingType()));
+    ASSERT(hasContiguous(indexingType()) || hasInt32(indexingType()) || hasDouble(indexingType()) || hasUndecided(indexingType()));
     ASSERT(length > m_butterfly->vectorLength());
     
     unsigned newVectorLength = std::min(
         length << 1,
         MAX_STORAGE_VECTOR_LENGTH);
     unsigned oldVectorLength = m_butterfly->vectorLength();
-    m_butterfly = m_butterfly->growArrayRight(
-        vm, structure(), structure()->outOfLineCapacity(), true,
+    DeferGC deferGC(vm.heap);
+    m_butterfly.set(vm, this, m_butterfly->growArrayRight(
+        vm, this, structure(), structure()->outOfLineCapacity(), true,
         oldVectorLength * sizeof(EncodedJSValue),
-        newVectorLength * sizeof(EncodedJSValue));
-    if (hasDouble(structure()->indexingType())) {
+        newVectorLength * sizeof(EncodedJSValue)));
+
+    m_butterfly->setVectorLength(newVectorLength);
+
+    if (hasDouble(indexingType())) {
         for (unsigned i = oldVectorLength; i < newVectorLength; ++i)
-            m_butterfly->contiguousDouble().data()[i] = QNaN;
+            m_butterfly->contiguousDouble().data()[i] = PNaN;
     }
-    m_butterfly->setVectorLength(newVectorLength);
 }
 
 Butterfly* JSObject::growOutOfLineStorage(VM& vm, size_t oldSize, size_t newSize)
@@ -2384,100 +2464,36 @@ Butterfly* JSObject::growOutOfLineStorage(VM& vm, size_t oldSize, size_t newSize
     // It's important that this function not rely on structure(), for the property
     // capacity, since we might have already mutated the structure in-place.
     
-    return m_butterfly->growPropertyStorage(vm, structure(), oldSize, newSize);
+    return Butterfly::createOrGrowPropertyStorage(m_butterfly.get(), vm, this, structure(vm), oldSize, newSize);
 }
 
-bool JSObject::getOwnPropertyDescriptor(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
+bool JSObject::getOwnPropertyDescriptor(ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
 {
-    unsigned attributes = 0;
-    JSCell* cell = 0;
-    PropertyOffset offset = object->structure()->get(exec->vm(), propertyName, attributes, cell);
-    if (isValidOffset(offset)) {
-        descriptor.setDescriptor(object->getDirect(offset), attributes);
-        return true;
-    }
-    
-    unsigned i = propertyName.asIndex();
-    if (i == PropertyName::NotAnIndex)
+    JSC::PropertySlot slot(this);
+    if (!methodTable(exec->vm())->getOwnPropertySlot(this, exec, propertyName, slot))
         return false;
-    
-    switch (object->structure()->indexingType()) {
-    case ALL_BLANK_INDEXING_TYPES:
-    case ALL_UNDECIDED_INDEXING_TYPES:
+    /* Workaround, JSDOMWindow::getOwnPropertySlot searches the prototype chain. :-( */
+    if (slot.slotBase() != this && slot.slotBase() && slot.slotBase()->methodTable(exec->vm())->toThis(slot.slotBase(), exec, NotStrictMode) != this)
         return false;
-        
-    case ALL_INT32_INDEXING_TYPES:
-    case ALL_CONTIGUOUS_INDEXING_TYPES: {
-        Butterfly* butterfly = object->m_butterfly;
-        if (i >= butterfly->vectorLength())
-            return false;
-        JSValue value = butterfly->contiguous()[i].get();
-        if (!value)
-            return false;
-        descriptor.setDescriptor(value, 0);
-        return true;
-    }
-        
-    case ALL_DOUBLE_INDEXING_TYPES: {
-        Butterfly* butterfly = object->m_butterfly;
-        if (i >= butterfly->vectorLength())
-            return false;
-        double value = butterfly->contiguousDouble()[i];
-        if (value != value)
-            return false;
-        descriptor.setDescriptor(JSValue(JSValue::EncodeAsDouble, value), 0);
-        return true;
-    }
-        
-    case ALL_ARRAY_STORAGE_INDEXING_TYPES: {
-        ArrayStorage* storage = object->m_butterfly->arrayStorage();
-        if (i >= storage->length())
-            return false;
-        if (i < storage->vectorLength()) {
-            WriteBarrier<Unknown>& value = storage->m_vector[i];
-            if (!value)
-                return false;
-            descriptor.setDescriptor(value.get(), 0);
-            return true;
-        }
-        if (SparseArrayValueMap* map = storage->m_sparseMap.get()) {
-            SparseArrayValueMap::iterator it = map->find(i);
-            if (it == map->notFound())
-                return false;
-            it->value.get(descriptor);
-            return true;
-        }
-        return false;
-    }
-        
-    default:
-        RELEASE_ASSERT_NOT_REACHED();
-        return false;
-    }
-}
-
-bool JSObject::getPropertyDescriptor(ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
-{
-    JSObject* object = this;
-    while (true) {
-        if (object->methodTable()->getOwnPropertyDescriptor(object, exec, propertyName, descriptor))
-            return true;
-        JSValue prototype = object->prototype();
-        if (!prototype.isObject())
-            return false;
-        object = asObject(prototype);
-    }
+    if (slot.isAccessor())
+        descriptor.setAccessorDescriptor(slot.getterSetter(), slot.attributes());
+    else if (slot.attributes() & CustomAccessor)
+        descriptor.setCustomDescriptor(slot.attributes());
+    else
+        descriptor.setDescriptor(slot.getValue(exec, propertyName), slot.attributes());
+    return true;
 }
 
-static bool putDescriptor(ExecState* exec, JSObject* target, PropertyName propertyName, PropertyDescriptor& descriptor, unsigned attributes, const PropertyDescriptor& oldDescriptor)
+static bool putDescriptor(ExecState* exec, JSObject* target, PropertyName propertyName, const PropertyDescriptor& descriptor, unsigned attributes, const PropertyDescriptor& oldDescriptor)
 {
+    VM& vm = exec->vm();
     if (descriptor.isGenericDescriptor() || descriptor.isDataDescriptor()) {
         if (descriptor.isGenericDescriptor() && oldDescriptor.isAccessorDescriptor()) {
-            GetterSetter* accessor = GetterSetter::create(exec);
+            GetterSetter* accessor = GetterSetter::create(vm);
             if (oldDescriptor.getterPresent())
-                accessor->setGetter(exec->vm(), oldDescriptor.getterObject());
+                accessor->setGetter(vm, oldDescriptor.getterObject());
             if (oldDescriptor.setterPresent())
-                accessor->setSetter(exec->vm(), oldDescriptor.setterObject());
+                accessor->setSetter(vm, oldDescriptor.setterObject());
             target->putDirectAccessor(exec, propertyName, accessor, attributes | Accessor);
             return true;
         }
@@ -2486,22 +2502,22 @@ static bool putDescriptor(ExecState* exec, JSObject* target, PropertyName proper
             newValue = descriptor.value();
         else if (oldDescriptor.value())
             newValue = oldDescriptor.value();
-        target->putDirect(exec->vm(), propertyName, newValue, attributes & ~Accessor);
+        target->putDirect(vm, propertyName, newValue, attributes & ~Accessor);
         if (attributes & ReadOnly)
-            target->structure()->setContainsReadOnlyProperties();
+            target->structure(vm)->setContainsReadOnlyProperties();
         return true;
     }
     attributes &= ~ReadOnly;
-    GetterSetter* accessor = GetterSetter::create(exec);
+    GetterSetter* accessor = GetterSetter::create(vm);
 
     if (descriptor.getterPresent())
-        accessor->setGetter(exec->vm(), descriptor.getterObject());
+        accessor->setGetter(vm, descriptor.getterObject());
     else if (oldDescriptor.getterPresent())
-        accessor->setGetter(exec->vm(), oldDescriptor.getterObject());
+        accessor->setGetter(vm, oldDescriptor.getterObject());
     if (descriptor.setterPresent())
-        accessor->setSetter(exec->vm(), descriptor.setterObject());
+        accessor->setSetter(vm, descriptor.setterObject());
     else if (oldDescriptor.setterPresent())
-        accessor->setSetter(exec->vm(), oldDescriptor.setterObject());
+        accessor->setSetter(vm, oldDescriptor.setterObject());
 
     target->putDirectAccessor(exec, propertyName, accessor, attributes | Accessor);
     return true;
@@ -2533,7 +2549,7 @@ private:
     VM& m_vm;
 };
 
-bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor, bool throwException)
+bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool throwException)
 {
     // Track on the globaldata that we're in define property.
     // Currently DefineOwnProperty uses delete to remove properties when they are being replaced
@@ -2543,11 +2559,11 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
     
     // If we have a new property we can just put it on normally
     PropertyDescriptor current;
-    if (!methodTable()->getOwnPropertyDescriptor(this, exec, propertyName, current)) {
+    if (!getOwnPropertyDescriptor(exec, propertyName, current)) {
         // unless extensions are prevented!
         if (!isExtensible()) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to define property on object that is not extensible.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to define property on object that is not extensible.")));
             return false;
         }
         PropertyDescriptor oldDescriptor;
@@ -2565,12 +2581,12 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
     if (!current.configurable()) {
         if (descriptor.configurable()) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to configurable attribute of unconfigurable property.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to configurable attribute of unconfigurable property.")));
             return false;
         }
         if (descriptor.enumerablePresent() && descriptor.enumerable() != current.enumerable()) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change enumerable attribute of unconfigurable property.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change enumerable attribute of unconfigurable property.")));
             return false;
         }
     }
@@ -2578,7 +2594,7 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
     // A generic descriptor is simply changing the attributes of an existing property
     if (descriptor.isGenericDescriptor()) {
         if (!current.attributesEqual(descriptor)) {
-            methodTable()->deleteProperty(this, exec, propertyName);
+            methodTable(exec->vm())->deleteProperty(this, exec, propertyName);
             return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributesOverridingCurrent(current), current);
         }
         return true;
@@ -2588,10 +2604,10 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
     if (descriptor.isDataDescriptor() != current.isDataDescriptor()) {
         if (!current.configurable()) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change access mechanism for an unconfigurable property.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change access mechanism for an unconfigurable property.")));
             return false;
         }
-        methodTable()->deleteProperty(this, exec, propertyName);
+        methodTable(exec->vm())->deleteProperty(this, exec, propertyName);
         return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributesOverridingCurrent(current), current);
     }
 
@@ -2600,20 +2616,20 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
         if (!current.configurable()) {
             if (!current.writable() && descriptor.writable()) {
                 if (throwException)
-                    throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change writable attribute of unconfigurable property.")));
+                    exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change writable attribute of unconfigurable property.")));
                 return false;
             }
             if (!current.writable()) {
                 if (descriptor.value() && !sameValue(exec, current.value(), descriptor.value())) {
                     if (throwException)
-                        throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change value of a readonly property.")));
+                        exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change value of a readonly property.")));
                     return false;
                 }
             }
         }
         if (current.attributesEqual(descriptor) && !descriptor.value())
             return true;
-        methodTable()->deleteProperty(this, exec, propertyName);
+        methodTable(exec->vm())->deleteProperty(this, exec, propertyName);
         return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributesOverridingCurrent(current), current);
     }
 
@@ -2622,32 +2638,43 @@ bool JSObject::defineOwnNonIndexProperty(ExecState* exec, PropertyName propertyN
     if (!current.configurable()) {
         if (descriptor.setterPresent() && !(current.setterPresent() && JSValue::strictEqual(exec, current.setter(), descriptor.setter()))) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change the setter of an unconfigurable property.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change the setter of an unconfigurable property.")));
             return false;
         }
         if (descriptor.getterPresent() && !(current.getterPresent() && JSValue::strictEqual(exec, current.getter(), descriptor.getter()))) {
             if (throwException)
-                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change the getter of an unconfigurable property.")));
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change the getter of an unconfigurable property.")));
+            return false;
+        }
+        if (current.attributes() & CustomAccessor) {
+            if (throwException)
+                exec->vm().throwException(exec, createTypeError(exec, ASCIILiteral("Attempting to change access mechanism for an unconfigurable property.")));
             return false;
         }
     }
     JSValue accessor = getDirect(exec->vm(), propertyName);
     if (!accessor)
         return false;
-    GetterSetter* getterSetter = asGetterSetter(accessor);
+    GetterSetter* getterSetter;
+    if (accessor.isCustomGetterSetter())
+        getterSetter = GetterSetter::create(exec->vm());
+    else {
+        ASSERT(accessor.isGetterSetter());
+        getterSetter = asGetterSetter(accessor);
+    }
     if (descriptor.setterPresent())
         getterSetter->setSetter(exec->vm(), descriptor.setterObject());
     if (descriptor.getterPresent())
         getterSetter->setGetter(exec->vm(), descriptor.getterObject());
     if (current.attributesEqual(descriptor))
         return true;
-    methodTable()->deleteProperty(this, exec, propertyName);
+    methodTable(exec->vm())->deleteProperty(this, exec, propertyName);
     unsigned attrs = descriptor.attributesOverridingCurrent(current);
     putDirectAccessor(exec, propertyName, getterSetter, attrs | Accessor);
     return true;
 }
 
-bool JSObject::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor, bool throwException)
+bool JSObject::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool throwException)
 {
     // If it's an array index, then use the indexed property storage.
     unsigned index = propertyName.asIndex();
@@ -2664,17 +2691,20 @@ bool JSObject::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName
     return object->defineOwnNonIndexProperty(exec, propertyName, descriptor, throwException);
 }
 
-bool JSObject::getOwnPropertySlotSlow(ExecState* exec, PropertyName propertyName, PropertySlot& slot)
+JSObject* throwTypeError(ExecState* exec, const String& message)
 {
-    unsigned i = propertyName.asIndex();
-    if (i != PropertyName::NotAnIndex)
-        return getOwnPropertySlotByIndex(this, exec, i, slot);
-    return false;
+    return exec->vm().throwException(exec, createTypeError(exec, message));
 }
 
-JSObject* throwTypeError(ExecState* exec, const String& message)
+void JSObject::shiftButterflyAfterFlattening(VM& vm, size_t outOfLineCapacityBefore, size_t outOfLineCapacityAfter)
 {
-    return throwError(exec, createTypeError(exec, message));
+    Butterfly* butterfly = this->butterfly();
+    size_t preCapacity = this->butterflyPreCapacity();
+    void* currentBase = butterfly->base(preCapacity, outOfLineCapacityAfter);
+    void* newBase = butterfly->base(preCapacity, outOfLineCapacityBefore);
+
+    memmove(newBase, currentBase, this->butterflyTotalSize());
+    setButterflyWithoutChangingStructure(vm, Butterfly::fromBase(newBase, preCapacity, outOfLineCapacityAfter));
 }
 
 } // namespace JSC