Merge webkit.org at r51976 : Initial merge by git.

Change-Id: Ib0e7e2f0fb4bee5a186610272edf3186f0986b43

50 files changed, 1245 insertions, 534 deletions

diff --git a/JavaScriptCore/runtime/ArgList.h b/JavaScriptCore/runtime/ArgList.h
index 3227770..8e1fdbe 100644
--- a/JavaScriptCore/runtime/ArgList.h
+++ b/JavaScriptCore/runtime/ArgList.h
@@ -104,7 +104,11 @@ namespace JSC {
         void append(JSValue v)
         {
             ASSERT(!m_isReadOnly);
-            
+
+#if ENABLE(JSC_ZOMBIES)
+            ASSERT(!v.isZombie());
+#endif
+
             if (m_isUsingInlineBuffer && m_size < inlineCapacity) {
                 m_vector.uncheckedAppend(v);
                 ++m_size;
@@ -187,6 +191,10 @@ namespace JSC {
             : m_args(args)
             , m_argCount(argCount)
         {
+#if ENABLE(JSC_ZOMBIES)
+            for (size_t i = 0; i < argCount; i++)
+                ASSERT(!m_args[i].isZombie());
+#endif
         }
         
         ArgList(Register* args, int argCount)
diff --git a/JavaScriptCore/runtime/ArrayPrototype.cpp b/JavaScriptCore/runtime/ArrayPrototype.cpp
index 7a89447..5b359e7 100644
--- a/JavaScriptCore/runtime/ArrayPrototype.cpp
+++ b/JavaScriptCore/runtime/ArrayPrototype.cpp
@@ -745,8 +745,8 @@ JSValue JSC_HOST_CALL arrayProtoFuncEvery(ExecState* exec, JSObject*, JSValue th
             cachedCall.setArgument(0, array->getIndex(k));
             cachedCall.setArgument(1, jsNumber(exec, k));
             cachedCall.setArgument(2, thisObj);
-            
-            if (!cachedCall.call().toBoolean(exec))
+            JSValue result = cachedCall.call();
+            if (!result.toBoolean(cachedCall.newCallFrame(exec)))
                 return jsBoolean(false);
         }
     }
@@ -846,8 +846,8 @@ JSValue JSC_HOST_CALL arrayProtoFuncSome(ExecState* exec, JSObject*, JSValue thi
             cachedCall.setArgument(0, array->getIndex(k));
             cachedCall.setArgument(1, jsNumber(exec, k));
             cachedCall.setArgument(2, thisObj);
-            
-            if (cachedCall.call().toBoolean(exec))
+            JSValue result = cachedCall.call();
+            if (result.toBoolean(cachedCall.newCallFrame(exec)))
                 return jsBoolean(true);
         }
     }
@@ -1034,7 +1034,7 @@ JSValue JSC_HOST_CALL arrayProtoFuncIndexOf(ExecState* exec, JSObject*, JSValue
         JSValue e = getProperty(exec, thisObj, index);
         if (!e)
             continue;
-        if (JSValue::strictEqual(searchElement, e))
+        if (JSValue::strictEqual(exec, searchElement, e))
             return jsNumber(exec, index);
     }
 
@@ -1065,7 +1065,7 @@ JSValue JSC_HOST_CALL arrayProtoFuncLastIndexOf(ExecState* exec, JSObject*, JSVa
         JSValue e = getProperty(exec, thisObj, index);
         if (!e)
             continue;
-        if (JSValue::strictEqual(searchElement, e))
+        if (JSValue::strictEqual(exec, searchElement, e))
             return jsNumber(exec, index);
     }
 
diff --git a/JavaScriptCore/runtime/BatchedTransitionOptimizer.h b/JavaScriptCore/runtime/BatchedTransitionOptimizer.h
index 929a5e7..74089a5 100644
--- a/JavaScriptCore/runtime/BatchedTransitionOptimizer.h
+++ b/JavaScriptCore/runtime/BatchedTransitionOptimizer.h
@@ -43,7 +43,7 @@ namespace JSC {
 
         ~BatchedTransitionOptimizer()
         {
-            m_object->setStructure(Structure::fromDictionaryTransition(m_object->structure()));
+            m_object->flattenDictionaryObject();
         }
 
     private:
diff --git a/JavaScriptCore/runtime/Collector.cpp b/JavaScriptCore/runtime/Collector.cpp
index 1b238d9..1630a58 100644
--- a/JavaScriptCore/runtime/Collector.cpp
+++ b/JavaScriptCore/runtime/Collector.cpp
@@ -32,6 +32,7 @@
 #include "JSONObject.h"
 #include "JSString.h"
 #include "JSValue.h"
+#include "JSZombie.h"
 #include "MarkStack.h"
 #include "Nodes.h"
 #include "Tracing.h"
@@ -118,11 +119,7 @@ static RHeap* userChunk = 0;
 #if PLATFORM(DARWIN)
 typedef mach_port_t PlatformThread;
 #elif PLATFORM(WIN_OS)
-struct PlatformThread {
-    PlatformThread(DWORD _id, HANDLE _handle) : id(_id), handle(_handle) {}
-    DWORD id;
-    HANDLE handle;
-};
+typedef HANDLE PlatformThread;
 #endif
 
 class Heap::Thread {
@@ -198,9 +195,11 @@ void Heap::destroy()
 
     sweep<PrimaryHeap>();
     // No need to sweep number heap, because the JSNumber destructor doesn't do anything.
-
+#if ENABLE(JSC_ZOMBIES)
+    ASSERT(primaryHeap.numLiveObjects == primaryHeap.numZombies);
+#else
     ASSERT(!primaryHeap.numLiveObjects);
-
+#endif
     freeBlocks(&primaryHeap);
     freeBlocks(&numberHeap);
 
@@ -646,8 +645,7 @@ static inline PlatformThread getCurrentPlatformThread()
 #if PLATFORM(DARWIN)
     return pthread_mach_thread_np(pthread_self());
 #elif PLATFORM(WIN_OS)
-    HANDLE threadHandle = pthread_getw32threadhandle_np(pthread_self());
-    return PlatformThread(GetCurrentThreadId(), threadHandle);
+    return pthread_getw32threadhandle_np(pthread_self());
 #endif
 }
 
@@ -811,7 +809,7 @@ static inline void suspendThread(const PlatformThread& platformThread)
 #if PLATFORM(DARWIN)
     thread_suspend(platformThread);
 #elif PLATFORM(WIN_OS)
-    SuspendThread(platformThread.handle);
+    SuspendThread(platformThread);
 #else
 #error Need a way to suspend threads on this platform
 #endif
@@ -822,7 +820,7 @@ static inline void resumeThread(const PlatformThread& platformThread)
 #if PLATFORM(DARWIN)
     thread_resume(platformThread);
 #elif PLATFORM(WIN_OS)
-    ResumeThread(platformThread.handle);
+    ResumeThread(platformThread);
 #else
 #error Need a way to resume threads on this platform
 #endif
@@ -886,7 +884,7 @@ static size_t getPlatformThreadRegisters(const PlatformThread& platformThread, P
 
 #elif PLATFORM(WIN_OS) && PLATFORM(X86)
     regs.ContextFlags = CONTEXT_INTEGER | CONTEXT_CONTROL | CONTEXT_SEGMENTS;
-    GetThreadContext(platformThread.handle, &regs);
+    GetThreadContext(platformThread, &regs);
     return sizeof(CONTEXT);
 #else
 #error Need a way to get thread registers on this platform
@@ -1041,17 +1039,26 @@ template <HeapType heapType> size_t Heap::sweep()
                         // assumes the object has a valid vptr.)
                         if (cell->u.freeCell.zeroIfFree == 0)
                             continue;
-                        
+#if ENABLE(JSC_ZOMBIES)
+                        if (!imp->isZombie()) {
+                            const ClassInfo* info = imp->classInfo();
+                            imp->~JSCell();
+                            new (imp) JSZombie(info, JSZombie::leakedZombieStructure());
+                            heap.numZombies++;
+                        }
+#else
                         imp->~JSCell();
+#endif
                     }
-                    
-                    --usedCells;
                     --numLiveObjects;
+#if !ENABLE(JSC_ZOMBIES)
+                    --usedCells;
                     
                     // put cell on the free list
                     cell->u.freeCell.zeroIfFree = 0;
                     cell->u.freeCell.next = freeList - (cell + 1);
                     freeList = cell;
+#endif
                 }
             }
         } else {
@@ -1064,8 +1071,18 @@ template <HeapType heapType> size_t Heap::sweep()
                     if (!curBlock->marked.get(i >> HeapConstants<heapType>::bitmapShift)) {
                         if (heapType != NumberHeap) {
                             JSCell* imp = reinterpret_cast<JSCell*>(cell);
+#if ENABLE(JSC_ZOMBIES)
+                            if (!imp->isZombie()) {
+                                const ClassInfo* info = imp->classInfo();
+                                imp->~JSCell();
+                                new (imp) JSZombie(info, JSZombie::leakedZombieStructure());
+                                heap.numZombies++;
+                            }
+#else
                             imp->~JSCell();
+#endif
                         }
+#if !ENABLE(JSC_ZOMBIES)
                         --usedCells;
                         --numLiveObjects;
                         
@@ -1073,6 +1090,7 @@ template <HeapType heapType> size_t Heap::sweep()
                         cell->u.freeCell.zeroIfFree = 0;
                         cell->u.freeCell.next = freeList - (cell + 1); 
                         freeList = cell;
+#endif
                     }
                 }
             }
diff --git a/JavaScriptCore/runtime/Collector.h b/JavaScriptCore/runtime/Collector.h
index 9ca9d18..9128701 100644
--- a/JavaScriptCore/runtime/Collector.h
+++ b/JavaScriptCore/runtime/Collector.h
@@ -60,6 +60,9 @@ namespace JSC {
         size_t numLiveObjects;
         size_t numLiveObjectsAtLastCollect;
         size_t extraCost;
+#if ENABLE(JSC_ZOMBIES)
+        size_t numZombies;
+#endif
 
         OperationInProgress operationInProgress;
     };
diff --git a/JavaScriptCore/runtime/DateConstructor.cpp b/JavaScriptCore/runtime/DateConstructor.cpp
index 9908fef..61ec4c5 100644
--- a/JavaScriptCore/runtime/DateConstructor.cpp
+++ b/JavaScriptCore/runtime/DateConstructor.cpp
@@ -77,14 +77,14 @@ JSObject* constructDate(ExecState* exec, const ArgList& args)
     double value;
 
     if (numArgs == 0) // new Date() ECMA 15.9.3.3
-        value = getCurrentUTCTime();
+        value = jsCurrentTime();
     else if (numArgs == 1) {
         if (args.at(0).inherits(&DateInstance::info))
             value = asDateInstance(args.at(0))->internalNumber();
         else {
             JSValue primitive = args.at(0).toPrimitive(exec);
             if (primitive.isString())
-                value = parseDate(primitive.getString());
+                value = parseDate(exec, primitive.getString(exec));
             else
                 value = primitive.toNumber(exec);
         }
@@ -108,7 +108,7 @@ JSObject* constructDate(ExecState* exec, const ArgList& args)
             t.second = args.at(5).toInt32(exec);
             t.isDST = -1;
             double ms = (numArgs >= 7) ? args.at(6).toNumber(exec) : 0;
-            value = gregorianDateTimeToMS(t, ms, false);
+            value = gregorianDateTimeToMS(exec, t, ms, false);
         }
     }
 
@@ -132,8 +132,8 @@ static JSValue JSC_HOST_CALL callDate(ExecState* exec, JSObject*, JSValue, const
     time_t localTime = time(0);
     tm localTM;
     getLocalTime(&localTime, &localTM);
-    GregorianDateTime ts(localTM);
-    return jsNontrivialString(exec, formatDate(ts) + " " + formatTime(ts, false));
+    GregorianDateTime ts(exec, localTM);
+    return jsNontrivialString(exec, formatDate(ts) + " " + formatTime(ts));
 }
 
 CallType DateConstructor::getCallData(CallData& callData)
@@ -144,12 +144,12 @@ CallType DateConstructor::getCallData(CallData& callData)
 
 static JSValue JSC_HOST_CALL dateParse(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, parseDate(args.at(0).toString(exec)));
+    return jsNumber(exec, parseDate(exec, args.at(0).toString(exec)));
 }
 
 static JSValue JSC_HOST_CALL dateNow(ExecState* exec, JSObject*, JSValue, const ArgList&)
 {
-    return jsNumber(exec, getCurrentUTCTime());
+    return jsNumber(exec, jsCurrentTime());
 }
 
 static JSValue JSC_HOST_CALL dateUTC(ExecState* exec, JSObject*, JSValue, const ArgList& args) 
@@ -173,7 +173,7 @@ static JSValue JSC_HOST_CALL dateUTC(ExecState* exec, JSObject*, JSValue, const
     t.minute = args.at(4).toInt32(exec);
     t.second = args.at(5).toInt32(exec);
     double ms = (n >= 7) ? args.at(6).toNumber(exec) : 0;
-    return jsNumber(exec, gregorianDateTimeToMS(t, ms, true));
+    return jsNumber(exec, gregorianDateTimeToMS(exec, t, ms, true));
 }
 
 } // namespace JSC
diff --git a/JavaScriptCore/runtime/DateConversion.cpp b/JavaScriptCore/runtime/DateConversion.cpp
index a725478..b9d0e02 100644
--- a/JavaScriptCore/runtime/DateConversion.cpp
+++ b/JavaScriptCore/runtime/DateConversion.cpp
@@ -43,6 +43,7 @@
 #include "config.h"
 #include "DateConversion.h"
 
+#include "CallFrame.h"
 #include "UString.h"
 #include <wtf/DateMath.h>
 #include <wtf/StringExtras.h>
@@ -51,9 +52,14 @@ using namespace WTF;
 
 namespace JSC {
 
-double parseDate(const UString &date)
+double parseDate(ExecState* exec, const UString &date)
 {
-    return parseDateFromNullTerminatedCharacters(date.UTF8String().c_str());
+    if (date == exec->globalData().cachedDateString)
+        return exec->globalData().cachedDateStringValue;
+    double value = parseDateFromNullTerminatedCharacters(exec, date.UTF8String().c_str());
+    exec->globalData().cachedDateString = date;
+    exec->globalData().cachedDateStringValue = value;
+    return value;
 }
 
 UString formatDate(const GregorianDateTime &t)
@@ -74,28 +80,31 @@ UString formatDateUTCVariant(const GregorianDateTime &t)
     return buffer;
 }
 
-UString formatTime(const GregorianDateTime &t, bool utc)
+UString formatTime(const GregorianDateTime &t)
 {
     char buffer[100];
-    if (utc) {
-        snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT", t.hour, t.minute, t.second);
-    } else {
-        int offset = abs(gmtoffset(t));
-        char timeZoneName[70];
-        struct tm gtm = t;
-        strftime(timeZoneName, sizeof(timeZoneName), "%Z", &gtm);
+    int offset = abs(gmtoffset(t));
+    char timeZoneName[70];
+    struct tm gtm = t;
+    strftime(timeZoneName, sizeof(timeZoneName), "%Z", &gtm);
 
-        if (timeZoneName[0]) {
-            snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT%c%02d%02d (%s)",
-                t.hour, t.minute, t.second,
-                gmtoffset(t) < 0 ? '-' : '+', offset / (60*60), (offset / 60) % 60, timeZoneName);
-        } else {
-            snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT%c%02d%02d",
-                t.hour, t.minute, t.second,
-                gmtoffset(t) < 0 ? '-' : '+', offset / (60*60), (offset / 60) % 60);
-        }
+    if (timeZoneName[0]) {
+        snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT%c%02d%02d (%s)",
+            t.hour, t.minute, t.second,
+            gmtoffset(t) < 0 ? '-' : '+', offset / (60*60), (offset / 60) % 60, timeZoneName);
+    } else {
+        snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT%c%02d%02d",
+            t.hour, t.minute, t.second,
+            gmtoffset(t) < 0 ? '-' : '+', offset / (60*60), (offset / 60) % 60);
     }
     return UString(buffer);
 }
 
+UString formatTimeUTC(const GregorianDateTime &t)
+{
+    char buffer[100];
+    snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d GMT", t.hour, t.minute, t.second);
+    return UString(buffer);
+}
+
 } // namespace JSC
diff --git a/JavaScriptCore/runtime/DateConversion.h b/JavaScriptCore/runtime/DateConversion.h
index 0d12815..dc980d3 100644
--- a/JavaScriptCore/runtime/DateConversion.h
+++ b/JavaScriptCore/runtime/DateConversion.h
@@ -42,18 +42,17 @@
 #ifndef DateConversion_h
 #define DateConversion_h
 
-namespace WTF {
-    struct GregorianDateTime;
-}
-
 namespace JSC {
 
+class ExecState;
 class UString;
+struct GregorianDateTime;
 
-double parseDate(const UString&);
-UString formatDate(const WTF::GregorianDateTime&);
-UString formatDateUTCVariant(const WTF::GregorianDateTime&);
-UString formatTime(const WTF::GregorianDateTime&, bool inputIsUTC);
+double parseDate(ExecState* exec, const UString&);
+UString formatDate(const GregorianDateTime&);
+UString formatDateUTCVariant(const GregorianDateTime&);
+UString formatTime(const GregorianDateTime&);
+UString formatTimeUTC(const GregorianDateTime&);
 
 } // namespace JSC
 
diff --git a/JavaScriptCore/runtime/DateInstance.cpp b/JavaScriptCore/runtime/DateInstance.cpp
index d4c9ef7..77a92be 100644
--- a/JavaScriptCore/runtime/DateInstance.cpp
+++ b/JavaScriptCore/runtime/DateInstance.cpp
@@ -46,30 +46,36 @@ DateInstance::DateInstance(ExecState* exec, double time)
     setInternalValue(jsNumber(exec, timeClip(time)));
 }
 
-bool DateInstance::getGregorianDateTime(ExecState* exec, bool outputIsUTC, GregorianDateTime& t) const
+const GregorianDateTime* DateInstance::calculateGregorianDateTime(ExecState* exec) const
 {
     double milli = internalNumber();
     if (isnan(milli))
-        return false;
+        return 0;
 
     if (!m_data)
         m_data = exec->globalData().dateInstanceCache.add(milli);
 
-    if (outputIsUTC) {
-        if (m_data->m_gregorianDateTimeUTCCachedForMS != milli) {
-            WTF::msToGregorianDateTime(internalNumber(), true, m_data->m_cachedGregorianDateTimeUTC);
-            m_data->m_gregorianDateTimeUTCCachedForMS = milli;
-        }
-        t.copyFrom(m_data->m_cachedGregorianDateTimeUTC);
-    } else {
-        if (m_data->m_gregorianDateTimeCachedForMS != milli) {
-            WTF::msToGregorianDateTime(internalNumber(), false, m_data->m_cachedGregorianDateTime);
-            m_data->m_gregorianDateTimeCachedForMS = milli;
-        }
-        t.copyFrom(m_data->m_cachedGregorianDateTime);
+    if (m_data->m_gregorianDateTimeCachedForMS != milli) {
+        msToGregorianDateTime(exec, milli, false, m_data->m_cachedGregorianDateTime);
+        m_data->m_gregorianDateTimeCachedForMS = milli;
     }
+    return &m_data->m_cachedGregorianDateTime;
+}
+
+const GregorianDateTime* DateInstance::calculateGregorianDateTimeUTC(ExecState* exec) const
+{
+    double milli = internalNumber();
+    if (isnan(milli))
+        return 0;
 
-    return true;
+    if (!m_data)
+        m_data = exec->globalData().dateInstanceCache.add(milli);
+
+    if (m_data->m_gregorianDateTimeUTCCachedForMS != milli) {
+        msToGregorianDateTime(exec, milli, true, m_data->m_cachedGregorianDateTimeUTC);
+        m_data->m_gregorianDateTimeUTCCachedForMS = milli;
+    }
+    return &m_data->m_cachedGregorianDateTimeUTC;
 }
 
 } // namespace JSC
diff --git a/JavaScriptCore/runtime/DateInstance.h b/JavaScriptCore/runtime/DateInstance.h
index 38b321c..44b7521 100644
--- a/JavaScriptCore/runtime/DateInstance.h
+++ b/JavaScriptCore/runtime/DateInstance.h
@@ -38,7 +38,19 @@ namespace JSC {
 
         static JS_EXPORTDATA const ClassInfo info;
 
-        bool getGregorianDateTime(ExecState*, bool outputIsUTC, WTF::GregorianDateTime&) const;
+        const GregorianDateTime* gregorianDateTime(ExecState* exec) const
+        {
+            if (m_data && m_data->m_gregorianDateTimeCachedForMS == internalNumber())
+                return &m_data->m_cachedGregorianDateTime;
+            return calculateGregorianDateTime(exec);
+        }
+        
+        const GregorianDateTime* gregorianDateTimeUTC(ExecState* exec) const
+        {
+            if (m_data && m_data->m_gregorianDateTimeUTCCachedForMS == internalNumber())
+                return &m_data->m_cachedGregorianDateTimeUTC;
+            return calculateGregorianDateTimeUTC(exec);
+        }
 
         static PassRefPtr<Structure> createStructure(JSValue prototype)
         {
@@ -49,6 +61,8 @@ namespace JSC {
         static const unsigned StructureFlags = OverridesMarkChildren | JSWrapperObject::StructureFlags;
 
     private:
+        const GregorianDateTime* calculateGregorianDateTime(ExecState*) const;
+        const GregorianDateTime* calculateGregorianDateTimeUTC(ExecState*) const;
         virtual const ClassInfo* classInfo() const { return &info; }
 
         mutable RefPtr<DateInstanceData> m_data;
diff --git a/JavaScriptCore/runtime/DateInstanceCache.h b/JavaScriptCore/runtime/DateInstanceCache.h
index b626c1d..d208580 100644
--- a/JavaScriptCore/runtime/DateInstanceCache.h
+++ b/JavaScriptCore/runtime/DateInstanceCache.h
@@ -40,9 +40,9 @@ namespace JSC {
         static PassRefPtr<DateInstanceData> create() { return adoptRef(new DateInstanceData); }
 
         double m_gregorianDateTimeCachedForMS;
-        WTF::GregorianDateTime m_cachedGregorianDateTime;
+        GregorianDateTime m_cachedGregorianDateTime;
         double m_gregorianDateTimeUTCCachedForMS;
-        WTF::GregorianDateTime m_cachedGregorianDateTimeUTC;
+        GregorianDateTime m_cachedGregorianDateTimeUTC;
 
     private:
         DateInstanceData()
@@ -56,6 +56,11 @@ namespace JSC {
     public:
         DateInstanceCache()
         {
+            reset();
+        }
+        
+        void reset()
+        {
             for (size_t i = 0; i < cacheSize; ++i)
                 m_cache[i].key = NaN;
         }
@@ -72,7 +77,7 @@ namespace JSC {
         }
 
     private:
-        static const size_t cacheSize = 64;
+        static const size_t cacheSize = 16;
 
         struct CacheEntry {
             double key;
diff --git a/JavaScriptCore/runtime/DatePrototype.cpp b/JavaScriptCore/runtime/DatePrototype.cpp
index 3f3e1f9..7a2e802 100644
--- a/JavaScriptCore/runtime/DatePrototype.cpp
+++ b/JavaScriptCore/runtime/DatePrototype.cpp
@@ -28,7 +28,6 @@
 #include "JSString.h"
 #include "ObjectPrototype.h"
 #include "DateInstance.h"
-#include <float.h>
 
 #if !PLATFORM(MAC) && HAVE(LANGINFO_H)
 #include <langinfo.h>
@@ -253,11 +252,10 @@ static JSCell* formatLocaleDate(ExecState* exec, const GregorianDateTime& gdt, L
 
 static JSCell* formatLocaleDate(ExecState* exec, DateInstance* dateObject, double, LocaleDateTimeFormat format, const ArgList&)
 {
-    GregorianDateTime gregorianDateTime;
-    const bool outputIsUTC = false;
-    if (!dateObject->getGregorianDateTime(exec, outputIsUTC, gregorianDateTime))
+    const GregorianDateTime* gregorianDateTime = dateObject->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return formatLocaleDate(exec, gregorianDateTime, format);
+    return formatLocaleDate(exec, *gregorianDateTime, format);
 }
 
 #endif // !PLATFORM(MAC)
@@ -420,14 +418,12 @@ JSValue JSC_HOST_CALL dateProtoFuncToString(ExecState* exec, JSObject*, JSValue
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return jsNontrivialString(exec, formatDate(t) + " " + formatTime(t, outputIsUTC));
+    return jsNontrivialString(exec, formatDate(*gregorianDateTime) + " " + formatTime(*gregorianDateTime));
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToUTCString(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -435,14 +431,12 @@ JSValue JSC_HOST_CALL dateProtoFuncToUTCString(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return jsNontrivialString(exec, formatDateUTCVariant(t) + " " + formatTime(t, outputIsUTC));
+    return jsNontrivialString(exec, formatDateUTCVariant(*gregorianDateTime) + " " + formatTimeUTC(*gregorianDateTime));
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToISOString(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -450,17 +444,15 @@ JSValue JSC_HOST_CALL dateProtoFuncToISOString(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
     
-    const bool outputIsUTC = true;
-    
     DateInstance* thisDateObj = asDateInstance(thisValue); 
     
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
     // Maximum amount of space we need in buffer: 6 (max. digits in year) + 2 * 5 (2 characters each for month, day, hour, minute, second) + 4 (. + 3 digits for milliseconds)
     // 6 for formatting and one for null termination = 27.  We add one extra character to allow us to force null termination.
     char buffer[28];
-    snprintf(buffer, sizeof(buffer) - 1, "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ", 1900 + t.year, t.month + 1, t.monthDay, t.hour, t.minute, t.second, static_cast<int>(fmod(thisDateObj->internalNumber(), 1000)));
+    snprintf(buffer, sizeof(buffer) - 1, "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ", 1900 + gregorianDateTime->year, gregorianDateTime->month + 1, gregorianDateTime->monthDay, gregorianDateTime->hour, gregorianDateTime->minute, gregorianDateTime->second, static_cast<int>(fmod(thisDateObj->internalNumber(), 1000)));
     buffer[sizeof(buffer) - 1] = 0;
     return jsNontrivialString(exec, buffer);
 }
@@ -470,14 +462,12 @@ JSValue JSC_HOST_CALL dateProtoFuncToDateString(ExecState* exec, JSObject*, JSVa
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return jsNontrivialString(exec, formatDate(t));
+    return jsNontrivialString(exec, formatDate(*gregorianDateTime));
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToTimeString(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -485,14 +475,12 @@ JSValue JSC_HOST_CALL dateProtoFuncToTimeString(ExecState* exec, JSObject*, JSVa
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return jsNontrivialString(exec, formatTime(t, outputIsUTC));
+    return jsNontrivialString(exec, formatTime(*gregorianDateTime));
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToLocaleString(ExecState* exec, JSObject*, JSValue thisValue, const ArgList& args)
@@ -535,14 +523,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetFullYear(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, 1900 + t.year);
+    return jsNumber(exec, 1900 + gregorianDateTime->year);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCFullYear(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -550,14 +536,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCFullYear(ExecState* exec, JSObject*, JS
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, 1900 + t.year);
+    return jsNumber(exec, 1900 + gregorianDateTime->year);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToGMTString(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -565,14 +549,12 @@ JSValue JSC_HOST_CALL dateProtoFuncToGMTString(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNontrivialString(exec, "Invalid Date");
-    return jsNontrivialString(exec, formatDateUTCVariant(t) + " " + formatTime(t, outputIsUTC));
+    return jsNontrivialString(exec, formatDateUTCVariant(*gregorianDateTime) + " " + formatTimeUTC(*gregorianDateTime));
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetMonth(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -580,14 +562,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetMonth(ExecState* exec, JSObject*, JSValue
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.month);
+    return jsNumber(exec, gregorianDateTime->month);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCMonth(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -595,14 +575,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCMonth(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.month);
+    return jsNumber(exec, gregorianDateTime->month);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetDate(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -610,14 +588,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetDate(ExecState* exec, JSObject*, JSValue t
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.monthDay);
+    return jsNumber(exec, gregorianDateTime->monthDay);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCDate(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -625,14 +601,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCDate(ExecState* exec, JSObject*, JSValu
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.monthDay);
+    return jsNumber(exec, gregorianDateTime->monthDay);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetDay(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -640,14 +614,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetDay(ExecState* exec, JSObject*, JSValue th
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.weekDay);
+    return jsNumber(exec, gregorianDateTime->weekDay);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCDay(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -655,14 +627,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCDay(ExecState* exec, JSObject*, JSValue
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.weekDay);
+    return jsNumber(exec, gregorianDateTime->weekDay);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetHours(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -670,14 +640,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetHours(ExecState* exec, JSObject*, JSValue
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.hour);
+    return jsNumber(exec, gregorianDateTime->hour);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCHours(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -685,14 +653,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCHours(ExecState* exec, JSObject*, JSVal
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.hour);
+    return jsNumber(exec, gregorianDateTime->hour);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetMinutes(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -700,14 +666,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetMinutes(ExecState* exec, JSObject*, JSValu
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.minute);
+    return jsNumber(exec, gregorianDateTime->minute);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCMinutes(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -715,14 +679,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCMinutes(ExecState* exec, JSObject*, JSV
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.minute);
+    return jsNumber(exec, gregorianDateTime->minute);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetSeconds(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -730,14 +692,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetSeconds(ExecState* exec, JSObject*, JSValu
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.second);
+    return jsNumber(exec, gregorianDateTime->second);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetUTCSeconds(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -745,14 +705,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetUTCSeconds(ExecState* exec, JSObject*, JSV
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = true;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTimeUTC(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, t.second);
+    return jsNumber(exec, gregorianDateTime->second);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncGetMilliSeconds(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
@@ -790,14 +748,12 @@ JSValue JSC_HOST_CALL dateProtoFuncGetTimezoneOffset(ExecState* exec, JSObject*,
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
-    return jsNumber(exec, -gmtoffset(t) / minutesPerHour);
+    return jsNumber(exec, -gregorianDateTime->utcOffset / minutesPerHour);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncSetTime(ExecState* exec, JSObject*, JSValue thisValue, const ArgList& args)
@@ -830,16 +786,21 @@ static JSValue setNewValueFromTimeArgs(ExecState* exec, JSValue thisValue, const
     double secs = floor(milli / msPerSecond);
     double ms = milli - secs * msPerSecond;
 
-    GregorianDateTime t;
-    thisDateObj->getGregorianDateTime(exec, inputIsUTC, t);
+    const GregorianDateTime* other = inputIsUTC 
+        ? thisDateObj->gregorianDateTimeUTC(exec)
+        : thisDateObj->gregorianDateTime(exec);
+    if (!other)
+        return jsNaN(exec);
 
-    if (!fillStructuresUsingTimeArgs(exec, args, numArgsToUse, &ms, &t)) {
+    GregorianDateTime gregorianDateTime;
+    gregorianDateTime.copyFrom(*other);
+    if (!fillStructuresUsingTimeArgs(exec, args, numArgsToUse, &ms, &gregorianDateTime)) {
         JSValue result = jsNaN(exec);
         thisDateObj->setInternalValue(result);
         return result;
     } 
     
-    JSValue result = jsNumber(exec, gregorianDateTimeToMS(t, ms, inputIsUTC));
+    JSValue result = jsNumber(exec, gregorianDateTimeToMS(exec, gregorianDateTime, ms, inputIsUTC));
     thisDateObj->setInternalValue(result);
     return result;
 }
@@ -857,26 +818,28 @@ static JSValue setNewValueFromDateArgs(ExecState* exec, JSValue thisValue, const
     }      
     
     double milli = thisDateObj->internalNumber();
-    double ms = 0;
-
-    GregorianDateTime t;
-    if (numArgsToUse == 3 && isnan(milli))
-        // Based on ECMA 262 15.9.5.40 - .41 (set[UTC]FullYear)
-        // the time must be reset to +0 if it is NaN. 
-        WTF::msToGregorianDateTime(0, true, t);
-    else {
-        double secs = floor(milli / msPerSecond);
-        ms = milli - secs * msPerSecond;
-        thisDateObj->getGregorianDateTime(exec, inputIsUTC, t);
+    double ms = 0; 
+
+    GregorianDateTime gregorianDateTime; 
+    if (numArgsToUse == 3 && isnan(milli)) 
+        msToGregorianDateTime(exec, 0, true, gregorianDateTime); 
+    else { 
+        ms = milli - floor(milli / msPerSecond) * msPerSecond; 
+        const GregorianDateTime* other = inputIsUTC 
+            ? thisDateObj->gregorianDateTimeUTC(exec)
+            : thisDateObj->gregorianDateTime(exec);
+        if (!other)
+            return jsNaN(exec);
+        gregorianDateTime.copyFrom(*other);
     }
     
-    if (!fillStructuresUsingDateArgs(exec, args, numArgsToUse, &ms, &t)) {
+    if (!fillStructuresUsingDateArgs(exec, args, numArgsToUse, &ms, &gregorianDateTime)) {
         JSValue result = jsNaN(exec);
         thisDateObj->setInternalValue(result);
         return result;
     } 
            
-    JSValue result = jsNumber(exec, gregorianDateTimeToMS(t, ms, inputIsUTC));
+    JSValue result = jsNumber(exec, gregorianDateTimeToMS(exec, gregorianDateTime, ms, inputIsUTC));
     thisDateObj->setInternalValue(result);
     return result;
 }
@@ -970,8 +933,6 @@ JSValue JSC_HOST_CALL dateProtoFuncSetYear(ExecState* exec, JSObject*, JSValue t
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue);     
     if (args.isEmpty()) { 
         JSValue result = jsNaN(exec);
@@ -982,15 +943,16 @@ JSValue JSC_HOST_CALL dateProtoFuncSetYear(ExecState* exec, JSObject*, JSValue t
     double milli = thisDateObj->internalNumber();
     double ms = 0;
 
-    GregorianDateTime t;
+    GregorianDateTime gregorianDateTime;
     if (isnan(milli))
         // Based on ECMA 262 B.2.5 (setYear)
         // the time must be reset to +0 if it is NaN. 
-        WTF::msToGregorianDateTime(0, true, t);
+        msToGregorianDateTime(exec, 0, true, gregorianDateTime);
     else {   
         double secs = floor(milli / msPerSecond);
         ms = milli - secs * msPerSecond;
-        thisDateObj->getGregorianDateTime(exec, outputIsUTC, t);
+        if (const GregorianDateTime* other = thisDateObj->gregorianDateTime(exec))
+            gregorianDateTime.copyFrom(*other);
     }
     
     bool ok = true;
@@ -1001,8 +963,8 @@ JSValue JSC_HOST_CALL dateProtoFuncSetYear(ExecState* exec, JSObject*, JSValue t
         return result;
     }
             
-    t.year = (year > 99 || year < 0) ? year - 1900 : year;
-    JSValue result = jsNumber(exec, gregorianDateTimeToMS(t, ms, outputIsUTC));
+    gregorianDateTime.year = (year > 99 || year < 0) ? year - 1900 : year;
+    JSValue result = jsNumber(exec, gregorianDateTimeToMS(exec, gregorianDateTime, ms, false));
     thisDateObj->setInternalValue(result);
     return result;
 }
@@ -1012,16 +974,14 @@ JSValue JSC_HOST_CALL dateProtoFuncGetYear(ExecState* exec, JSObject*, JSValue t
     if (!thisValue.inherits(&DateInstance::info))
         return throwError(exec, TypeError);
 
-    const bool outputIsUTC = false;
-
     DateInstance* thisDateObj = asDateInstance(thisValue); 
 
-    GregorianDateTime t;
-    if (!thisDateObj->getGregorianDateTime(exec, outputIsUTC, t))
+    const GregorianDateTime* gregorianDateTime = thisDateObj->gregorianDateTime(exec);
+    if (!gregorianDateTime)
         return jsNaN(exec);
 
     // NOTE: IE returns the full year even in getYear.
-    return jsNumber(exec, t.year);
+    return jsNumber(exec, gregorianDateTime->year);
 }
 
 JSValue JSC_HOST_CALL dateProtoFuncToJSON(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
diff --git a/JavaScriptCore/runtime/FunctionPrototype.cpp b/JavaScriptCore/runtime/FunctionPrototype.cpp
index 45f17b1..a3a7479 100644
--- a/JavaScriptCore/runtime/FunctionPrototype.cpp
+++ b/JavaScriptCore/runtime/FunctionPrototype.cpp
@@ -90,13 +90,13 @@ JSValue JSC_HOST_CALL functionProtoFuncToString(ExecState* exec, JSObject*, JSVa
             FunctionExecutable* executable = function->jsExecutable();
             UString sourceString = executable->source().toString();
             insertSemicolonIfNeeded(sourceString);
-            return jsString(exec, "function " + function->name(&exec->globalData()) + "(" + executable->paramString() + ") " + sourceString);
+            return jsString(exec, "function " + function->name(exec) + "(" + executable->paramString() + ") " + sourceString);
         }
     }
 
     if (thisValue.inherits(&InternalFunction::info)) {
         InternalFunction* function = asInternalFunction(thisValue);
-        return jsString(exec, "function " + function->name(&exec->globalData()) + "() {\n    [native code]\n}");
+        return jsString(exec, "function " + function->name(exec) + "() {\n    [native code]\n}");
     }
 
     return throwError(exec, TypeError);
diff --git a/JavaScriptCore/runtime/InitializeThreading.cpp b/JavaScriptCore/runtime/InitializeThreading.cpp
index fea89f8..aad1af8 100644
--- a/JavaScriptCore/runtime/InitializeThreading.cpp
+++ b/JavaScriptCore/runtime/InitializeThreading.cpp
@@ -51,7 +51,7 @@ static void initializeThreadingOnce()
     initializeUString();
 #if ENABLE(JSC_MULTIPLE_THREADS)
     s_dtoaP5Mutex = new Mutex;
-    WTF::initializeDates();
+    initializeDates();
 #endif
 }
 
diff --git a/JavaScriptCore/runtime/InternalFunction.cpp b/JavaScriptCore/runtime/InternalFunction.cpp
index 2ba2984..c48d628 100644
--- a/JavaScriptCore/runtime/InternalFunction.cpp
+++ b/JavaScriptCore/runtime/InternalFunction.cpp
@@ -43,29 +43,29 @@ InternalFunction::InternalFunction(JSGlobalData* globalData, NonNullPassRefPtr<S
     putDirect(globalData->propertyNames->name, jsString(globalData, name.ustring()), DontDelete | ReadOnly | DontEnum);
 }
 
-const UString& InternalFunction::name(JSGlobalData* globalData)
+const UString& InternalFunction::name(ExecState* exec)
 {
-    return asString(getDirect(globalData->propertyNames->name))->value();
+    return asString(getDirect(exec->globalData().propertyNames->name))->value(exec);
 }
 
-const UString InternalFunction::displayName(JSGlobalData* globalData)
+const UString InternalFunction::displayName(ExecState* exec)
 {
-    JSValue displayName = getDirect(globalData->propertyNames->displayName);
+    JSValue displayName = getDirect(exec->globalData().propertyNames->displayName);
     
-    if (displayName && isJSString(globalData, displayName))
-        return asString(displayName)->value();
+    if (displayName && isJSString(&exec->globalData(), displayName))
+        return asString(displayName)->value(exec);
     
     return UString::null();
 }
 
-const UString InternalFunction::calculatedDisplayName(JSGlobalData* globalData)
+const UString InternalFunction::calculatedDisplayName(ExecState* exec)
 {
-    const UString explicitName = displayName(globalData);
+    const UString explicitName = displayName(exec);
     
     if (!explicitName.isEmpty())
         return explicitName;
     
-    return name(globalData);
+    return name(exec);
 }
 
 } // namespace JSC
diff --git a/JavaScriptCore/runtime/InternalFunction.h b/JavaScriptCore/runtime/InternalFunction.h
index de9a1d6..fa1e5aa 100644
--- a/JavaScriptCore/runtime/InternalFunction.h
+++ b/JavaScriptCore/runtime/InternalFunction.h
@@ -36,9 +36,9 @@ namespace JSC {
         virtual const ClassInfo* classInfo() const; 
         static JS_EXPORTDATA const ClassInfo info;
 
-        const UString& name(JSGlobalData*);
-        const UString displayName(JSGlobalData*);
-        const UString calculatedDisplayName(JSGlobalData*);
+        const UString& name(ExecState*);
+        const UString displayName(ExecState*);
+        const UString calculatedDisplayName(ExecState*);
 
         static PassRefPtr<Structure> createStructure(JSValue proto) 
         { 
diff --git a/JavaScriptCore/runtime/JSArray.cpp b/JavaScriptCore/runtime/JSArray.cpp
index fd9e7b2..b16d3fa 100644
--- a/JavaScriptCore/runtime/JSArray.cpp
+++ b/JavaScriptCore/runtime/JSArray.cpp
@@ -785,7 +785,7 @@ struct AVLTreeAbstractorForArrayCompare {
             m_cachedCall->setThis(m_globalThisValue);
             m_cachedCall->setArgument(0, va);
             m_cachedCall->setArgument(1, vb);
-            compareResult = m_cachedCall->call().toNumber(m_cachedCall->newCallFrame());
+            compareResult = m_cachedCall->call().toNumber(m_cachedCall->newCallFrame(m_exec));
         } else {
             MarkedArgumentBuffer arguments;
             arguments.append(va);
diff --git a/JavaScriptCore/runtime/JSCell.cpp b/JavaScriptCore/runtime/JSCell.cpp
index fae056e..17410e2 100644
--- a/JavaScriptCore/runtime/JSCell.cpp
+++ b/JavaScriptCore/runtime/JSCell.cpp
@@ -86,17 +86,17 @@ bool JSCell::getUInt32(uint32_t&) const
     return false;
 }
 
-bool JSCell::getString(UString&stringValue) const
+bool JSCell::getString(ExecState* exec, UString&stringValue) const
 {
     if (!isString())
         return false;
-    stringValue = static_cast<const JSString*>(this)->value();
+    stringValue = static_cast<const JSString*>(this)->value(exec);
     return true;
 }
 
-UString JSCell::getString() const
+UString JSCell::getString(ExecState* exec) const
 {
-    return isString() ? static_cast<const JSString*>(this)->value() : UString();
+    return isString() ? static_cast<const JSString*>(this)->value(exec) : UString();
 }
 
 JSObject* JSCell::getObject()
diff --git a/JavaScriptCore/runtime/JSCell.h b/JavaScriptCore/runtime/JSCell.h
index 722ae33..c8ba2b8 100644
--- a/JavaScriptCore/runtime/JSCell.h
+++ b/JavaScriptCore/runtime/JSCell.h
@@ -42,6 +42,7 @@ namespace JSC {
         friend class JSString;
         friend class JSValue;
         friend class JSAPIValueWrapper;
+        friend class JSZombie;
         friend struct VPtrSet;
 
     private:
@@ -64,8 +65,8 @@ namespace JSC {
         Structure* structure() const;
 
         // Extracting the value.
-        bool getString(UString&) const;
-        UString getString() const; // null string if not a string
+        bool getString(ExecState* exec, UString&) const;
+        UString getString(ExecState* exec) const; // null string if not a string
         JSObject* getObject(); // NULL if not an object
         const JSObject* getObject() const; // NULL if not an object
         
@@ -90,6 +91,9 @@ namespace JSC {
         void* operator new(size_t, void* placementNewDestination) { return placementNewDestination; }
 
         virtual void markChildren(MarkStack&);
+#if ENABLE(JSC_ZOMBIES)
+        virtual bool isZombie() const { return false; }
+#endif
 
         // Object operations, with the toObject operation included.
         virtual const ClassInfo* classInfo() const;
@@ -175,14 +179,14 @@ namespace JSC {
         return isCell() && asCell()->isObject();
     }
 
-    inline bool JSValue::getString(UString& s) const
+    inline bool JSValue::getString(ExecState* exec, UString& s) const
     {
-        return isCell() && asCell()->getString(s);
+        return isCell() && asCell()->getString(exec, s);
     }
 
-    inline UString JSValue::getString() const
+    inline UString JSValue::getString(ExecState* exec) const
     {
-        return isCell() ? asCell()->getString() : UString();
+        return isCell() ? asCell()->getString(exec) : UString();
     }
 
     inline JSObject* JSValue::getObject() const
@@ -342,7 +346,13 @@ namespace JSC {
     {
         return cellBlock(c)->heap;
     }
-
+    
+#if ENABLE(JSC_ZOMBIES)
+    inline bool JSValue::isZombie() const
+    {
+        return isCell() && asCell() && asCell()->isZombie();
+    }
+#endif
 } // namespace JSC
 
 #endif // JSCell_h
diff --git a/JavaScriptCore/runtime/JSGlobalData.cpp b/JavaScriptCore/runtime/JSGlobalData.cpp
index 1221ef2..234449f 100644
--- a/JavaScriptCore/runtime/JSGlobalData.cpp
+++ b/JavaScriptCore/runtime/JSGlobalData.cpp
@@ -82,26 +82,28 @@ struct VPtrSet {
 
 VPtrSet::VPtrSet()
 {
-    // Bizarrely, calling fastMalloc here is faster than allocating space on the stack.
-    void* storage = fastMalloc(sizeof(CollectorBlock));
+    CollectorCell cell;
+    void* storage = &cell;
 
+    COMPILE_ASSERT(sizeof(JSArray) <= sizeof(CollectorCell), sizeof_JSArray_must_be_less_than_CollectorCell);
     JSCell* jsArray = new (storage) JSArray(JSArray::createStructure(jsNull()));
     jsArrayVPtr = jsArray->vptr();
     jsArray->~JSCell();
 
+    COMPILE_ASSERT(sizeof(JSByteArray) <= sizeof(CollectorCell), sizeof_JSByteArray_must_be_less_than_CollectorCell);
     JSCell* jsByteArray = new (storage) JSByteArray(JSByteArray::VPtrStealingHack);
     jsByteArrayVPtr = jsByteArray->vptr();
     jsByteArray->~JSCell();
 
+    COMPILE_ASSERT(sizeof(JSString) <= sizeof(CollectorCell), sizeof_JSString_must_be_less_than_CollectorCell);
     JSCell* jsString = new (storage) JSString(JSString::VPtrStealingHack);
     jsStringVPtr = jsString->vptr();
     jsString->~JSCell();
 
+    COMPILE_ASSERT(sizeof(JSFunction) <= sizeof(CollectorCell), sizeof_JSFunction_must_be_less_than_CollectorCell);
     JSCell* jsFunction = new (storage) JSFunction(JSFunction::createStructure(jsNull()));
     jsFunctionVPtr = jsFunction->vptr();
     jsFunction->~JSCell();
-
-    fastFree(storage);
 }
 
 JSGlobalData::JSGlobalData(bool isShared, const VPtrSet& vptrSet)
@@ -147,6 +149,8 @@ JSGlobalData::JSGlobalData(bool isShared, const VPtrSet& vptrSet)
     , functionCodeBlockBeingReparsed(0)
     , firstStringifierToMark(0)
     , markStack(vptrSet.jsArrayVPtr)
+    , cachedUTCOffset(NaN)
+    , weakRandom(static_cast<int>(currentTime()))
 #ifndef NDEBUG
     , mainThreadOnly(false)
 #endif
@@ -251,6 +255,14 @@ JSGlobalData::ClientData::~ClientData()
 {
 }
 
+void JSGlobalData::resetDateCache()
+{
+    cachedUTCOffset = NaN;
+    dstOffsetCache.reset();
+    cachedDateString = UString();
+    dateInstanceCache.reset();
+}
+
 void JSGlobalData::startSampling()
 {
     interpreter->startSampling();
diff --git a/JavaScriptCore/runtime/JSGlobalData.h b/JavaScriptCore/runtime/JSGlobalData.h
index d2aa2da..f0c1b5c 100644
--- a/JavaScriptCore/runtime/JSGlobalData.h
+++ b/JavaScriptCore/runtime/JSGlobalData.h
@@ -38,6 +38,7 @@
 #include "NumericStrings.h"
 #include "SmallStrings.h"
 #include "TimeoutChecker.h"
+#include "WeakRandom.h"
 #include <wtf/Forward.h>
 #include <wtf/HashMap.h>
 #include <wtf/RefCounted.h>
@@ -63,6 +64,26 @@ namespace JSC {
     struct Instruction;    
     struct VPtrSet;
 
+    struct DSTOffsetCache {
+        DSTOffsetCache()
+        {
+            reset();
+        }
+        
+        void reset()
+        {
+            offset = 0.0;
+            start = 0.0;
+            end = -1.0;
+            increment = 0.0;
+        }
+
+        double offset;
+        double start;
+        double end;
+        double increment;
+    };
+
     class JSGlobalData : public RefCounted<JSGlobalData> {
     public:
         struct ClientData {
@@ -153,10 +174,20 @@ namespace JSC {
 
         MarkStack markStack;
 
+        double cachedUTCOffset;
+        DSTOffsetCache dstOffsetCache;
+        
+        UString cachedDateString;
+        double cachedDateStringValue;
+        
+        WeakRandom weakRandom;
+
 #ifndef NDEBUG
         bool mainThreadOnly;
 #endif
 
+        void resetDateCache();
+
         void startSampling();
         void stopSampling();
         void dumpSampleData(ExecState* exec);
@@ -165,7 +196,7 @@ namespace JSC {
         static JSGlobalData*& sharedInstanceInternal();
         void createNativeThunk();
     };
-
+    
 } // namespace JSC
 
 #endif // JSGlobalData_h
diff --git a/JavaScriptCore/runtime/JSGlobalObject.h b/JavaScriptCore/runtime/JSGlobalObject.h
index 720d3a5..9e4ef49 100644
--- a/JavaScriptCore/runtime/JSGlobalObject.h
+++ b/JavaScriptCore/runtime/JSGlobalObject.h
@@ -442,7 +442,13 @@ namespace JSC {
             : m_dynamicGlobalObjectSlot(callFrame->globalData().dynamicGlobalObject)
             , m_savedDynamicGlobalObject(m_dynamicGlobalObjectSlot)
         {
-            m_dynamicGlobalObjectSlot = dynamicGlobalObject;
+            if (!m_dynamicGlobalObjectSlot) {
+                m_dynamicGlobalObjectSlot = dynamicGlobalObject;
+
+                // Reset the date cache between JS invocations to force the VM
+                // to observe time zone changes.
+                callFrame->globalData().resetDateCache();
+            }
         }
 
         ~DynamicGlobalObjectScope()
diff --git a/JavaScriptCore/runtime/JSNumberCell.h b/JavaScriptCore/runtime/JSNumberCell.h
index 309488f..e9e2470 100644
--- a/JavaScriptCore/runtime/JSNumberCell.h
+++ b/JavaScriptCore/runtime/JSNumberCell.h
@@ -109,6 +109,11 @@ namespace JSC {
         return static_cast<JSNumberCell*>(v.asCell());
     }
 
+    ALWAYS_INLINE JSValue::JSValue(EncodeAsDoubleTag, ExecState* exec, double d)
+    {
+        *this = jsNumberCell(exec, d);
+    }
+
     inline JSValue::JSValue(ExecState* exec, double d)
     {
         JSValue v = JSImmediate::from(d);
@@ -193,6 +198,11 @@ namespace JSC {
 #endif // USE(JSVALUE32)
 
 #if USE(JSVALUE64)
+    ALWAYS_INLINE JSValue::JSValue(EncodeAsDoubleTag, ExecState*, double d)
+    {
+        *this = JSImmediate::fromNumberOutsideIntegerRange(d);
+    }
+
     inline JSValue::JSValue(ExecState*, double d)
     {
         JSValue v = JSImmediate::from(d);
diff --git a/JavaScriptCore/runtime/JSONObject.cpp b/JavaScriptCore/runtime/JSONObject.cpp
index 297d457..cc7f6d9 100644
--- a/JavaScriptCore/runtime/JSONObject.cpp
+++ b/JavaScriptCore/runtime/JSONObject.cpp
@@ -70,7 +70,23 @@ public:
     void markAggregate(MarkStack&);
 
 private:
-    typedef UString StringBuilder;
+    class StringBuilder : public Vector<UChar> {
+    public:
+        using Vector<UChar>::append;
+
+        inline void append(const char* str)
+        {
+            size_t len = strlen(str);
+            reserveCapacity(size() + len);
+            for (size_t i = 0; i < len; i++)
+                Vector<UChar>::append(str[i]);
+        }
+
+        inline void append(const UString& str)
+        {
+            append(str.data(), str.size());
+        }
+    };
 
     class Holder {
     public:
@@ -156,7 +172,7 @@ static inline UString gap(ExecState* exec, JSValue space)
     }
 
     // If the space value is a string, use it as the gap string, otherwise use no gap string.
-    UString spaces = space.getString();
+    UString spaces = space.getString(exec);
     if (spaces.size() > maxGapLength) {
         spaces = spaces.substr(0, maxGapLength);
     }
@@ -213,7 +229,7 @@ Stringifier::Stringifier(ExecState* exec, JSValue replacer, JSValue space)
                 break;
 
             UString propertyName;
-            if (name.getString(propertyName)) {
+            if (name.getString(exec, propertyName)) {
                 m_arrayReplacerPropertyNames.add(Identifier(exec, propertyName));
                 continue;
             }
@@ -269,7 +285,9 @@ JSValue Stringifier::stringify(JSValue value)
     if (m_exec->hadException())
         return jsNull();
 
-    return jsString(m_exec, result);
+    result.shrinkToFit();
+    size_t length = result.size();
+    return jsString(m_exec, UString(result.releaseBuffer(), length, false));
 }
 
 void Stringifier::appendQuotedString(StringBuilder& builder, const UString& value)
@@ -389,7 +407,7 @@ Stringifier::StringifyResult Stringifier::appendStringifiedValue(StringBuilder&
     }
 
     UString stringValue;
-    if (value.getString(stringValue)) {
+    if (value.getString(m_exec, stringValue)) {
         appendQuotedString(builder, stringValue);
         return StringifySucceeded;
     }
@@ -586,7 +604,7 @@ bool Stringifier::Holder::appendNextProperty(Stringifier& stringifier, StringBui
             // This only occurs when get an undefined value for an object property.
             // In this case we don't want the separator and property name that we
             // already appended, so roll back.
-            builder = builder.substr(0, rollBackPoint);
+            builder.resize(rollBackPoint);
             break;
     }
 
diff --git a/JavaScriptCore/runtime/JSObject.cpp b/JavaScriptCore/runtime/JSObject.cpp
index 6932ded..ed9fdc2 100644
--- a/JavaScriptCore/runtime/JSObject.cpp
+++ b/JavaScriptCore/runtime/JSObject.cpp
@@ -406,26 +406,10 @@ bool JSObject::hasInstance(ExecState* exec, JSValue value, JSValue proto)
 
 bool JSObject::propertyIsEnumerable(ExecState* exec, const Identifier& propertyName) const
 {
-    unsigned attributes;
-    if (!getPropertyAttributes(exec, propertyName, attributes))
+    PropertyDescriptor descriptor;
+    if (!const_cast<JSObject*>(this)->getOwnPropertyDescriptor(exec, propertyName, descriptor))
         return false;
-    return !(attributes & DontEnum);
-}
-
-bool JSObject::getPropertyAttributes(ExecState* exec, const Identifier& propertyName, unsigned& attributes) const
-{
-    JSCell* specificValue;
-    if (m_structure->get(propertyName, attributes, specificValue) != WTF::notFound)
-        return true;
-    
-    // Look in the static hashtable of properties
-    const HashEntry* entry = findPropertyHashEntry(exec, propertyName);
-    if (entry) {
-        attributes = entry->attributes();
-        return true;
-    }
-    
-    return false;
+    return descriptor.enumerable();
 }
 
 bool JSObject::getPropertySpecificValue(ExecState*, const Identifier& propertyName, JSCell*& specificValue) const
@@ -522,12 +506,12 @@ void JSObject::removeDirect(const Identifier& propertyName)
 
 void JSObject::putDirectFunction(ExecState* exec, InternalFunction* function, unsigned attr)
 {
-    putDirectFunction(Identifier(exec, function->name(&exec->globalData())), function, attr);
+    putDirectFunction(Identifier(exec, function->name(exec)), function, attr);
 }
 
 void JSObject::putDirectFunctionWithoutTransition(ExecState* exec, InternalFunction* function, unsigned attr)
 {
-    putDirectFunctionWithoutTransition(Identifier(exec, function->name(&exec->globalData())), function, attr);
+    putDirectFunctionWithoutTransition(Identifier(exec, function->name(exec)), function, attr);
 }
 
 NEVER_INLINE void JSObject::fillGetterPropertySlot(PropertySlot& slot, JSValue* location)
@@ -599,7 +583,7 @@ bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName
     if (descriptor.isEmpty())
         return true;
 
-    if (current.equalTo(descriptor))
+    if (current.equalTo(exec, descriptor))
         return true;
 
     // Filter out invalid changes
@@ -645,7 +629,7 @@ bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName
                 return false;
             }
             if (!current.writable()) {
-                if (descriptor.value() || !JSValue::strictEqual(current.value(), descriptor.value())) {
+                if (descriptor.value() || !JSValue::strictEqual(exec, current.value(), descriptor.value())) {
                     if (throwException)
                         throwError(exec, TypeError, "Attempting to change value of a readonly property.");
                     return false;
@@ -667,12 +651,12 @@ bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName
     // Changing the accessor functions of an existing accessor property
     ASSERT(descriptor.isAccessorDescriptor());
     if (!current.configurable()) {
-        if (descriptor.setterPresent() && !(current.setter() && JSValue::strictEqual(current.setter(), descriptor.setter()))) {
+        if (descriptor.setterPresent() && !(current.setter() && JSValue::strictEqual(exec, current.setter(), descriptor.setter()))) {
             if (throwException)
                 throwError(exec, TypeError, "Attempting to change the setter of an unconfigurable property.");
             return false;
         }
-        if (descriptor.getterPresent() && !(current.getter() && JSValue::strictEqual(current.getter(), descriptor.getter()))) {
+        if (descriptor.getterPresent() && !(current.getter() && JSValue::strictEqual(exec, current.getter(), descriptor.getter()))) {
             if (throwException)
                 throwError(exec, TypeError, "Attempting to change the getter of an unconfigurable property.");
             return false;
diff --git a/JavaScriptCore/runtime/JSObject.h b/JavaScriptCore/runtime/JSObject.h
index 5a89c40..a5da267 100644
--- a/JavaScriptCore/runtime/JSObject.h
+++ b/JavaScriptCore/runtime/JSObject.h
@@ -135,7 +135,6 @@ namespace JSC {
         virtual JSObject* toThisObject(ExecState*) const;
         virtual JSObject* unwrappedObject();
 
-        virtual bool getPropertyAttributes(ExecState*, const Identifier& propertyName, unsigned& attributes) const;
         bool getPropertySpecificValue(ExecState* exec, const Identifier& propertyName, JSCell*& specificFunction) const;
 
         // This get function only looks at the property map.
@@ -210,6 +209,11 @@ namespace JSC {
             return Structure::create(prototype, TypeInfo(ObjectType, StructureFlags));
         }
 
+        void flattenDictionaryObject()
+        {
+            m_structure->flattenDictionaryStructure(this);
+        }
+
     protected:
         static const unsigned StructureFlags = 0;
 
@@ -229,7 +233,7 @@ namespace JSC {
         using JSCell::isGetterSetter;
         using JSCell::toObject;
         void getObject();
-        void getString();
+        void getString(ExecState* exec);
         void isObject();
         void isString();
 #if USE(JSVALUE32)
diff --git a/JavaScriptCore/runtime/JSPropertyNameIterator.cpp b/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
index 6fd0344..d3dcb83 100644
--- a/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
+++ b/JavaScriptCore/runtime/JSPropertyNameIterator.cpp
@@ -45,7 +45,8 @@ JSPropertyNameIterator* JSPropertyNameIterator::create(ExecState* exec, JSObject
     o->getPropertyNames(exec, propertyNames);
     size_t numCacheableSlots = 0;
     if (!o->structure()->hasNonEnumerableProperties() && !o->structure()->hasAnonymousSlots() &&
-        !o->structure()->isUncacheableDictionary() && !o->structure()->typeInfo().overridesGetPropertyNames())
+        !o->structure()->hasGetterSetterProperties() && !o->structure()->isUncacheableDictionary() &&
+        !o->structure()->typeInfo().overridesGetPropertyNames())
         numCacheableSlots = o->structure()->propertyStorageSize();
 
     JSPropertyNameIterator* jsPropertyNameIterator = new (exec) JSPropertyNameIterator(exec, propertyNames.data(), numCacheableSlots);
@@ -76,7 +77,7 @@ JSValue JSPropertyNameIterator::get(ExecState* exec, JSObject* base, size_t i)
     if (m_cachedStructure == base->structure() && m_cachedPrototypeChain == base->structure()->prototypeChain(exec))
         return identifier;
 
-    if (!base->hasProperty(exec, Identifier(exec, asString(identifier)->value())))
+    if (!base->hasProperty(exec, Identifier(exec, asString(identifier)->value(exec))))
         return JSValue();
     return identifier;
 }
diff --git a/JavaScriptCore/runtime/JSString.cpp b/JavaScriptCore/runtime/JSString.cpp
index 20ba868..28ae6f7 100644
--- a/JavaScriptCore/runtime/JSString.cpp
+++ b/JavaScriptCore/runtime/JSString.cpp
@@ -25,41 +25,160 @@
 
 #include "JSGlobalObject.h"
 #include "JSObject.h"
+#include "Operations.h"
 #include "StringObject.h"
 #include "StringPrototype.h"
 
 namespace JSC {
 
+void JSString::Rope::destructNonRecursive()
+{
+    Vector<Rope*, 32> workQueue;
+    Rope* rope = this;
+
+    while (true) {
+        unsigned length = rope->ropeLength();
+        for (unsigned i = 0; i < length; ++i) {
+            Fiber& fiber = rope->fibers(i);
+            if (fiber.isString())
+                fiber.string()->deref();
+            else {
+                Rope* nextRope = fiber.rope();
+                if (nextRope->hasOneRef())
+                    workQueue.append(nextRope);
+                else
+                    nextRope->deref();
+            }
+        }
+        if (rope != this)
+            fastFree(rope);
+
+        if (workQueue.isEmpty())
+            return;
+
+        rope = workQueue.last();
+        workQueue.removeLast();
+    }
+}
+
+JSString::Rope::~Rope()
+{
+    destructNonRecursive();
+}
+
+#define ROPE_COPY_CHARS_INLINE_CUTOFF 20
+
+static inline void copyChars(UChar* destination, const UChar* source, unsigned numCharacters)
+{
+#ifdef ROPE_COPY_CHARS_INLINE_CUTOFF
+    if (numCharacters <= ROPE_COPY_CHARS_INLINE_CUTOFF) {
+        for (unsigned i = 0; i < numCharacters; ++i)
+            destination[i] = source[i];
+        return;
+    }
+#endif
+    memcpy(destination, source, numCharacters * sizeof(UChar));
+}
+
+// Overview: this methods converts a JSString from holding a string in rope form
+// down to a simple UString representation.  It does so by building up the string
+// backwards, since we want to avoid recursion, we expect that the tree structure
+// representing the rope is likely imbalanced with more nodes down the left side
+// (since appending to the string is likely more common) - and as such resolving
+// in this fashion should minimize work queue size.  (If we built the queue forwards
+// we would likely have to place all of the constituent UString::Reps into the
+// Vector before performing any concatenation, but by working backwards we likely
+// only fill the queue with the number of substrings at any given level in a
+// rope-of-ropes.)
+void JSString::resolveRope(ExecState* exec) const
+{
+    ASSERT(isRope());
+
+    // Allocate the buffer to hold the final string, position initially points to the end.
+    UChar* buffer;
+    if (!tryFastMalloc(m_stringLength * sizeof(UChar)).getValue(buffer)) {
+        for (unsigned i = 0; i < m_ropeLength; ++i)
+            m_fibers[i].deref();
+        m_ropeLength = 0;
+        ASSERT(!isRope());
+        ASSERT(m_value == UString());
+
+        throwOutOfMemoryError(exec);
+        return;
+    }
+    UChar* position = buffer + m_stringLength;
+
+    // Start with the current Rope.
+    Vector<Rope::Fiber, 32> workQueue;
+    Rope::Fiber currentFiber;
+    for (unsigned i = 0; i < (m_ropeLength - 1); ++i)
+        workQueue.append(m_fibers[i]);
+    currentFiber = m_fibers[m_ropeLength - 1];
+    while (true) {
+        if (currentFiber.isRope()) {
+            Rope* rope = currentFiber.rope();
+            // Copy the contents of the current rope into the workQueue, with the last item in 'currentFiber'
+            // (we will be working backwards over the rope).
+            unsigned ropeLengthMinusOne = rope->ropeLength() - 1;
+            for (unsigned i = 0; i < ropeLengthMinusOne; ++i)
+                workQueue.append(rope->fibers(i));
+            currentFiber = rope->fibers(ropeLengthMinusOne);
+        } else {
+            UString::Rep* string = currentFiber.string();
+            unsigned length = string->len;
+            position -= length;
+            copyChars(position, string->data(), length);
+
+            // Was this the last item in the work queue?
+            if (workQueue.isEmpty()) {
+                // Create a string from the UChar buffer, clear the rope RefPtr.
+                ASSERT(buffer == position);
+                m_value = UString::Rep::create(buffer, m_stringLength);
+                for (unsigned i = 0; i < m_ropeLength; ++i)
+                    m_fibers[i].deref();
+                m_ropeLength = 0;
+
+                ASSERT(!isRope());
+                return;
+            }
+
+            // No! - set the next item up to process.
+            currentFiber = workQueue.last();
+            workQueue.removeLast();
+        }
+    }
+}
+
 JSValue JSString::toPrimitive(ExecState*, PreferredPrimitiveType) const
 {
     return const_cast<JSString*>(this);
 }
 
-bool JSString::getPrimitiveNumber(ExecState*, double& number, JSValue& value)
+bool JSString::getPrimitiveNumber(ExecState* exec, double& number, JSValue& result)
 {
-    value = this;
-    number = m_value.toDouble();
+    result = this;
+    number = value(exec).toDouble();
     return false;
 }
 
 bool JSString::toBoolean(ExecState*) const
 {
-    return !m_value.isEmpty();
+    return m_stringLength;
 }
 
-double JSString::toNumber(ExecState*) const
+double JSString::toNumber(ExecState* exec) const
 {
-    return m_value.toDouble();
+    return value(exec).toDouble();
 }
 
-UString JSString::toString(ExecState*) const
+UString JSString::toString(ExecState* exec) const
 {
-    return m_value;
+    return value(exec);
 }
 
-UString JSString::toThisString(ExecState*) const
+UString JSString::toThisString(ExecState* exec) const
 {
-    return m_value;
+    return value(exec);
 }
 
 JSString* JSString::toThisJSString(ExecState*)
@@ -106,14 +225,14 @@ bool JSString::getOwnPropertySlot(ExecState* exec, const Identifier& propertyNam
 bool JSString::getStringPropertyDescriptor(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
 {
     if (propertyName == exec->propertyNames().length) {
-        descriptor.setDescriptor(jsNumber(exec, m_value.size()), DontEnum | DontDelete | ReadOnly);
+        descriptor.setDescriptor(jsNumber(exec, m_stringLength), DontEnum | DontDelete | ReadOnly);
         return true;
     }
     
     bool isStrictUInt32;
     unsigned i = propertyName.toStrictUInt32(&isStrictUInt32);
-    if (isStrictUInt32 && i < static_cast<unsigned>(m_value.size())) {
-        descriptor.setDescriptor(jsSingleCharacterSubstring(exec, m_value, i), DontDelete | ReadOnly);
+    if (isStrictUInt32 && i < m_stringLength) {
+        descriptor.setDescriptor(jsSingleCharacterSubstring(exec, value(exec), i), DontDelete | ReadOnly);
         return true;
     }
     
diff --git a/JavaScriptCore/runtime/JSString.h b/JavaScriptCore/runtime/JSString.h
index 39dfe75..1867b17 100644
--- a/JavaScriptCore/runtime/JSString.h
+++ b/JavaScriptCore/runtime/JSString.h
@@ -60,13 +60,110 @@ namespace JSC {
     JSString* jsOwnedString(ExecState*, const UString&); 
 
     class JSString : public JSCell {
+    public:
         friend class JIT;
         friend struct VPtrSet;
 
-    public:
+        // A Rope is a string composed of a set of substrings.
+        class Rope : public RefCounted<Rope> {
+        public:
+            // A Rope is composed from a set of smaller strings called Fibers.
+            // Each Fiber in a rope is either UString::Rep or another Rope.
+            class Fiber {
+            public:
+                Fiber() {}
+                Fiber(UString::Rep* string) : m_value(reinterpret_cast<intptr_t>(string)) {}
+                Fiber(Rope* rope) : m_value(reinterpret_cast<intptr_t>(rope) | 1) {}
+
+                void deref()
+                {
+                    if (isRope())
+                        rope()->deref();
+                    else
+                        string()->deref();
+                }
+
+                Fiber& ref()
+                {
+                    if (isString())
+                        string()->ref();
+                    else
+                        rope()->ref();
+                    return *this;
+                }
+
+                unsigned refAndGetLength()
+                {
+                    if (isString()) {
+                        UString::Rep* rep = string();
+                        return rep->ref()->len;
+                    } else {
+                        Rope* r = rope();
+                        r->ref();
+                        return r->stringLength();
+                    }
+                }
+
+                bool isRope() { return m_value & 1; }
+                Rope* rope() { return reinterpret_cast<Rope*>(m_value & ~1); }
+                bool isString() { return !isRope(); }
+                UString::Rep* string() { return reinterpret_cast<UString::Rep*>(m_value); }
+
+            private:
+                intptr_t m_value;
+            };
+
+            // Creates a Rope comprising of 'ropeLength' Fibers.
+            // The Rope is constructed in an uninitialized state - initialize must be called for each Fiber in the Rope.
+            static PassRefPtr<Rope> createOrNull(unsigned ropeLength)
+            {
+                void* allocation;
+                if (tryFastMalloc(sizeof(Rope) + (ropeLength - 1) * sizeof(Fiber)).getValue(allocation))
+                    return adoptRef(new (allocation) Rope(ropeLength));
+                return 0;
+            }
+
+            ~Rope();
+            void destructNonRecursive();
+
+            void append(unsigned &index, Fiber& fiber)
+            {
+                m_fibers[index++] = fiber;
+                m_stringLength += fiber.refAndGetLength();
+            }
+            void append(unsigned &index, const UString& string)
+            {
+                UString::Rep* rep = string.rep();
+                m_fibers[index++] = Fiber(rep);
+                m_stringLength += rep->ref()->len;
+            }
+            void append(unsigned& index, JSString* jsString)
+            {
+                if (jsString->isRope()) {
+                    for (unsigned i = 0; i < jsString->m_ropeLength; ++i)
+                        append(index, jsString->m_fibers[i]);
+                } else
+                    append(index, jsString->string());
+            }
+
+            unsigned ropeLength() { return m_ropeLength; }
+            unsigned stringLength() { return m_stringLength; }
+            Fiber& fibers(unsigned index) { return m_fibers[index]; }
+
+        private:
+            Rope(unsigned ropeLength) : m_ropeLength(ropeLength), m_stringLength(0) {}
+            void* operator new(size_t, void* inPlace) { return inPlace; }
+            
+            unsigned m_ropeLength;
+            unsigned m_stringLength;
+            Fiber m_fibers[1];
+        };
+
         JSString(JSGlobalData* globalData, const UString& value)
             : JSCell(globalData->stringStructure.get())
+            , m_stringLength(value.size())
             , m_value(value)
+            , m_ropeLength(0)
         {
             Heap::heap(this)->reportExtraMemoryCost(value.cost());
         }
@@ -74,23 +171,106 @@ namespace JSC {
         enum HasOtherOwnerType { HasOtherOwner };
         JSString(JSGlobalData* globalData, const UString& value, HasOtherOwnerType)
             : JSCell(globalData->stringStructure.get())
+            , m_stringLength(value.size())
             , m_value(value)
+            , m_ropeLength(0)
         {
         }
         JSString(JSGlobalData* globalData, PassRefPtr<UString::Rep> value, HasOtherOwnerType)
             : JSCell(globalData->stringStructure.get())
+            , m_stringLength(value->size())
             , m_value(value)
+            , m_ropeLength(0)
         {
         }
-        
-        const UString& value() const { return m_value; }
+        JSString(JSGlobalData* globalData, PassRefPtr<JSString::Rope> rope)
+            : JSCell(globalData->stringStructure.get())
+            , m_stringLength(rope->stringLength())
+            , m_ropeLength(1)
+        {
+            m_fibers[0] = rope.releaseRef();
+        }
+        // This constructor constructs a new string by concatenating s1 & s2.
+        // This should only be called with ropeLength <= 3.
+        JSString(JSGlobalData* globalData, unsigned ropeLength, JSString* s1, JSString* s2)
+            : JSCell(globalData->stringStructure.get())
+            , m_stringLength(s1->length() + s2->length())
+            , m_ropeLength(ropeLength)
+        {
+            ASSERT(ropeLength <= s_maxInternalRopeLength);
+            unsigned index = 0;
+            appendStringInConstruct(index, s1);
+            appendStringInConstruct(index, s2);
+            ASSERT(ropeLength == index);
+        }
+        // This constructor constructs a new string by concatenating s1 & s2.
+        // This should only be called with ropeLength <= 3.
+        JSString(JSGlobalData* globalData, unsigned ropeLength, JSString* s1, const UString& u2)
+            : JSCell(globalData->stringStructure.get())
+            , m_stringLength(s1->length() + u2.size())
+            , m_ropeLength(ropeLength)
+        {
+            ASSERT(ropeLength <= s_maxInternalRopeLength);
+            unsigned index = 0;
+            appendStringInConstruct(index, s1);
+            appendStringInConstruct(index, u2);
+            ASSERT(ropeLength == index);
+        }
+        // This constructor constructs a new string by concatenating s1 & s2.
+        // This should only be called with ropeLength <= 3.
+        JSString(JSGlobalData* globalData, unsigned ropeLength, const UString& u1, JSString* s2)
+            : JSCell(globalData->stringStructure.get())
+            , m_stringLength(u1.size() + s2->length())
+            , m_ropeLength(ropeLength)
+        {
+            ASSERT(ropeLength <= s_maxInternalRopeLength);
+            unsigned index = 0;
+            appendStringInConstruct(index, u1);
+            appendStringInConstruct(index, s2);
+            ASSERT(ropeLength == index);
+        }
+        // This constructor constructs a new string by concatenating v1, v2 & v3.
+        // This should only be called with ropeLength <= 3 ... which since every
+        // value must require a ropeLength of at least one implies that the length
+        // for each value must be exactly 1!
+        JSString(ExecState* exec, JSValue v1, JSValue v2, JSValue v3)
+            : JSCell(exec->globalData().stringStructure.get())
+            , m_stringLength(0)
+            , m_ropeLength(s_maxInternalRopeLength)
+        {
+            unsigned index = 0;
+            appendValueInConstructAndIncrementLength(exec, index, v1);
+            appendValueInConstructAndIncrementLength(exec, index, v2);
+            appendValueInConstructAndIncrementLength(exec, index, v3);
+            ASSERT(index == s_maxInternalRopeLength);
+        }
+
+        ~JSString()
+        {
+            for (unsigned i = 0; i < m_ropeLength; ++i)
+                m_fibers[i].deref();
+        }
+
+        const UString& value(ExecState* exec) const
+        {
+            if (isRope())
+                resolveRope(exec);
+            return m_value;
+        }
+        const UString tryGetValue() const
+        {
+            if (isRope())
+                UString();
+            return m_value;
+        }
+        unsigned length() { return m_stringLength; }
 
         bool getStringPropertySlot(ExecState*, const Identifier& propertyName, PropertySlot&);
         bool getStringPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
         bool getStringPropertyDescriptor(ExecState*, const Identifier& propertyName, PropertyDescriptor&);
 
-        bool canGetIndex(unsigned i) { return i < static_cast<unsigned>(m_value.size()); }
-        JSString* getIndex(JSGlobalData*, unsigned);
+        bool canGetIndex(unsigned i) { return i < m_stringLength; }
+        JSString* getIndex(ExecState*, unsigned);
 
         static PassRefPtr<Structure> createStructure(JSValue proto) { return Structure::create(proto, TypeInfo(StringType, OverridesGetOwnPropertySlot | NeedsThisConversion)); }
 
@@ -98,7 +278,39 @@ namespace JSC {
         enum VPtrStealingHackType { VPtrStealingHack };
         JSString(VPtrStealingHackType) 
             : JSCell(0)
+            , m_ropeLength(0)
+        {
+        }
+
+        void resolveRope(ExecState*) const;
+
+        void appendStringInConstruct(unsigned& index, const UString& string)
+        {
+            m_fibers[index++] = Rope::Fiber(string.rep()->ref());
+        }
+
+        void appendStringInConstruct(unsigned& index, JSString* jsString)
+        {
+            if (jsString->isRope()) {
+                for (unsigned i = 0; i < jsString->m_ropeLength; ++i)
+                    m_fibers[index++] = jsString->m_fibers[i].ref();
+            } else
+                appendStringInConstruct(index, jsString->string());
+        }
+
+        void appendValueInConstructAndIncrementLength(ExecState* exec, unsigned& index, JSValue v)
         {
+            if (v.isString()) {
+                ASSERT(asCell(v)->isString());
+                JSString* s = static_cast<JSString*>(asCell(v));
+                ASSERT(s->ropeLength() == 1);
+                appendStringInConstruct(index, s);
+                m_stringLength += s->length();
+            } else {
+                UString u(v.toString(exec));
+                m_fibers[index++] = Rope::Fiber(u.rep()->ref());
+                m_stringLength += u.size();
+            }
         }
 
         virtual JSValue toPrimitive(ExecState*, PreferredPrimitiveType) const;
@@ -117,7 +329,22 @@ namespace JSC {
         virtual bool getOwnPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
         virtual bool getOwnPropertyDescriptor(ExecState*, const Identifier&, PropertyDescriptor&);
 
-        UString m_value;
+        static const unsigned s_maxInternalRopeLength = 3;
+
+        // A string is represented either by a UString or a Rope.
+        unsigned m_stringLength;
+        mutable UString m_value;
+        mutable unsigned m_ropeLength;
+        mutable Rope::Fiber m_fibers[s_maxInternalRopeLength];
+
+        bool isRope() const { return m_ropeLength; }
+        UString& string() { ASSERT(!isRope()); return m_value; }
+        unsigned ropeLength() { return m_ropeLength ? m_ropeLength : 1; }
+
+        friend JSValue jsString(ExecState* exec, JSString* s1, JSString* s2);
+        friend JSValue jsString(ExecState* exec, const UString& u1, JSString* s2);
+        friend JSValue jsString(ExecState* exec, JSString* s1, const UString& u2);
+        friend JSValue jsString(ExecState* exec, Register* strings, unsigned count);
     };
 
     JSString* asString(JSValue);
@@ -146,7 +373,7 @@ namespace JSC {
         UChar c = s.data()[offset];
         if (c <= 0xFF)
             return globalData->smallStrings.singleCharacterString(globalData, c);
-        return new (globalData) JSString(globalData, UString::Rep::create(s.rep(), offset, 1));
+        return new (globalData) JSString(globalData, UString(UString::Rep::create(s.rep(), offset, 1)));
     }
 
     inline JSString* jsNontrivialString(JSGlobalData* globalData, const char* s)
@@ -163,10 +390,10 @@ namespace JSC {
         return new (globalData) JSString(globalData, s);
     }
 
-    inline JSString* JSString::getIndex(JSGlobalData* globalData, unsigned i)
+    inline JSString* JSString::getIndex(ExecState* exec, unsigned i)
     {
         ASSERT(canGetIndex(i));
-        return jsSingleCharacterSubstring(globalData, m_value, i);
+        return jsSingleCharacterSubstring(&exec->globalData(), value(exec), i);
     }
 
     inline JSString* jsString(JSGlobalData* globalData, const UString& s)
@@ -181,7 +408,7 @@ namespace JSC {
         }
         return new (globalData) JSString(globalData, s);
     }
-        
+
     inline JSString* jsSubstring(JSGlobalData* globalData, const UString& s, unsigned offset, unsigned length)
     {
         ASSERT(offset <= static_cast<unsigned>(s.size()));
@@ -194,7 +421,7 @@ namespace JSC {
             if (c <= 0xFF)
                 return globalData->smallStrings.singleCharacterString(globalData, c);
         }
-        return new (globalData) JSString(globalData, UString::Rep::create(s.rep(), offset, length));
+        return new (globalData) JSString(globalData, UString(UString::Rep::create(s.rep(), offset, length)));
     }
 
     inline JSString* jsOwnedString(JSGlobalData* globalData, const UString& s)
@@ -222,14 +449,14 @@ namespace JSC {
     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
     {
         if (propertyName == exec->propertyNames().length) {
-            slot.setValue(jsNumber(exec, m_value.size()));
+            slot.setValue(jsNumber(exec, m_stringLength));
             return true;
         }
 
         bool isStrictUInt32;
         unsigned i = propertyName.toStrictUInt32(&isStrictUInt32);
-        if (isStrictUInt32 && i < static_cast<unsigned>(m_value.size())) {
-            slot.setValue(jsSingleCharacterSubstring(exec, m_value, i));
+        if (isStrictUInt32 && i < m_stringLength) {
+            slot.setValue(jsSingleCharacterSubstring(exec, value(exec), i));
             return true;
         }
 
@@ -238,8 +465,8 @@ namespace JSC {
         
     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
     {
-        if (propertyName < static_cast<unsigned>(m_value.size())) {
-            slot.setValue(jsSingleCharacterSubstring(exec, m_value, propertyName));
+        if (propertyName < m_stringLength) {
+            slot.setValue(jsSingleCharacterSubstring(exec, value(exec), propertyName));
             return true;
         }
 
@@ -258,7 +485,7 @@ namespace JSC {
     inline UString JSValue::toString(ExecState* exec) const
     {
         if (isString())
-            return static_cast<JSString*>(asCell())->value();
+            return static_cast<JSString*>(asCell())->value(exec);
         if (isInt32())
             return exec->globalData().numericStrings.add(asInt32());
         if (isDouble())
diff --git a/JavaScriptCore/runtime/JSValue.h b/JavaScriptCore/runtime/JSValue.h
index 1063cdc..fa5b5c0 100644
--- a/JavaScriptCore/runtime/JSValue.h
+++ b/JavaScriptCore/runtime/JSValue.h
@@ -80,6 +80,7 @@ namespace JSC {
         enum JSUndefinedTag { JSUndefined };
         enum JSTrueTag { JSTrue };
         enum JSFalseTag { JSFalse };
+        enum EncodeAsDoubleTag { EncodeAsDouble };
 
         JSValue();
         JSValue(JSNullTag);
@@ -90,6 +91,7 @@ namespace JSC {
         JSValue(const JSCell* ptr);
 
         // Numbers
+        JSValue(EncodeAsDoubleTag, ExecState*, double);
         JSValue(ExecState*, double);
         JSValue(ExecState*, char);
         JSValue(ExecState*, unsigned char);
@@ -135,8 +137,8 @@ namespace JSC {
         bool getBoolean() const; // false if not a boolean
         bool getNumber(double&) const;
         double uncheckedGetNumber() const;
-        bool getString(UString&) const;
-        UString getString() const; // null string if not a string
+        bool getString(ExecState* exec, UString&) const;
+        UString getString(ExecState* exec) const; // null string if not a string
         JSObject* getObject() const; // 0 if not an object
 
         CallType getCallData(CallData&);
@@ -166,6 +168,10 @@ namespace JSC {
         uint32_t toUInt32(ExecState*) const;
         uint32_t toUInt32(ExecState*, bool& ok) const;
 
+#if ENABLE(JSC_ZOMBIES)
+        bool isZombie() const;
+#endif
+
         // Floating point conversions (this is a convenience method for webcore;
         // signle precision float is not a representation used in JS or JSC).
         float toFloat(ExecState* exec) const { return static_cast<float>(toNumber(exec)); }
@@ -186,9 +192,9 @@ namespace JSC {
         static bool equal(ExecState* exec, JSValue v1, JSValue v2);
         static bool equalSlowCase(ExecState* exec, JSValue v1, JSValue v2);
         static bool equalSlowCaseInline(ExecState* exec, JSValue v1, JSValue v2);
-        static bool strictEqual(JSValue v1, JSValue v2);
-        static bool strictEqualSlowCase(JSValue v1, JSValue v2);
-        static bool strictEqualSlowCaseInline(JSValue v1, JSValue v2);
+        static bool strictEqual(ExecState* exec, JSValue v1, JSValue v2);
+        static bool strictEqualSlowCase(ExecState* exec, JSValue v1, JSValue v2);
+        static bool strictEqualSlowCaseInline(ExecState* exec, JSValue v1, JSValue v2);
 
         JSValue getJSNumber(); // JSValue() if this is not a JSNumber or number object
 
@@ -279,6 +285,11 @@ namespace JSC {
         return b ? JSValue(JSValue::JSTrue) : JSValue(JSValue::JSFalse);
     }
 
+    ALWAYS_INLINE JSValue jsDoubleNumber(ExecState* exec, double d)
+    {
+        return JSValue(JSValue::EncodeAsDouble, exec, d);
+    }
+
     ALWAYS_INLINE JSValue jsNumber(ExecState* exec, double d)
     {
         return JSValue(exec, d);
@@ -431,6 +442,9 @@ namespace JSC {
     {
         JSValue v;
         v.u.asEncodedJSValue = encodedJSValue;
+#if ENABLE(JSC_ZOMBIES)
+        ASSERT(!v.isZombie());
+#endif
         return v;
     }
 
@@ -477,6 +491,9 @@ namespace JSC {
         else
             u.asBits.tag = EmptyValueTag;
         u.asBits.payload = reinterpret_cast<int32_t>(ptr);
+#if ENABLE(JSC_ZOMBIES)
+        ASSERT(!isZombie());
+#endif
     }
 
     inline JSValue::JSValue(const JSCell* ptr)
@@ -486,6 +503,9 @@ namespace JSC {
         else
             u.asBits.tag = EmptyValueTag;
         u.asBits.payload = reinterpret_cast<int32_t>(const_cast<JSCell*>(ptr));
+#if ENABLE(JSC_ZOMBIES)
+        ASSERT(!isZombie());
+#endif
     }
 
     inline JSValue::operator bool() const
@@ -583,6 +603,11 @@ namespace JSC {
         return reinterpret_cast<JSCell*>(u.asBits.payload);
     }
 
+    ALWAYS_INLINE JSValue::JSValue(EncodeAsDoubleTag, ExecState*, double d)
+    {
+        u.asDouble = d;
+    }
+
     inline JSValue::JSValue(ExecState* exec, double d)
     {
         const int32_t asInt32 = static_cast<int32_t>(d);
@@ -781,11 +806,17 @@ namespace JSC {
     inline JSValue::JSValue(JSCell* ptr)
         : m_ptr(ptr)
     {
+#if ENABLE(JSC_ZOMBIES)
+        ASSERT(!isZombie());
+#endif
     }
 
     inline JSValue::JSValue(const JSCell* ptr)
         : m_ptr(const_cast<JSCell*>(ptr))
     {
+#if ENABLE(JSC_ZOMBIES)
+        ASSERT(!isZombie());
+#endif
     }
 
     inline JSValue::operator bool() const
diff --git a/JavaScriptCore/runtime/JSVariableObject.cpp b/JavaScriptCore/runtime/JSVariableObject.cpp
index 6586393..3aa9e62 100644
--- a/JavaScriptCore/runtime/JSVariableObject.cpp
+++ b/JavaScriptCore/runtime/JSVariableObject.cpp
@@ -53,16 +53,6 @@ void JSVariableObject::getOwnPropertyNames(ExecState* exec, PropertyNameArray& p
     JSObject::getOwnPropertyNames(exec, propertyNames);
 }
 
-bool JSVariableObject::getPropertyAttributes(ExecState* exec, const Identifier& propertyName, unsigned& attributes) const
-{
-    SymbolTableEntry entry = symbolTable().get(propertyName.ustring().rep());
-    if (!entry.isNull()) {
-        attributes = entry.getAttributes() | DontDelete;
-        return true;
-    }
-    return JSObject::getPropertyAttributes(exec, propertyName, attributes);
-}
-
 bool JSVariableObject::isVariableObject() const
 {
     return true;
diff --git a/JavaScriptCore/runtime/JSVariableObject.h b/JavaScriptCore/runtime/JSVariableObject.h
index d8b1479..15d6ff5 100644
--- a/JavaScriptCore/runtime/JSVariableObject.h
+++ b/JavaScriptCore/runtime/JSVariableObject.h
@@ -54,8 +54,6 @@ namespace JSC {
         virtual bool isVariableObject() const;
         virtual bool isDynamicScope() const = 0;
 
-        virtual bool getPropertyAttributes(ExecState*, const Identifier& propertyName, unsigned& attributes) const;
-
         Register& registerAt(int index) const { return d->registers[index]; }
 
         static PassRefPtr<Structure> createStructure(JSValue prototype)
diff --git a/JavaScriptCore/runtime/JSZombie.cpp b/JavaScriptCore/runtime/JSZombie.cpp
new file mode 100644
index 0000000..072d29b
--- /dev/null
+++ b/JavaScriptCore/runtime/JSZombie.cpp
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2009 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    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 INC. ``AS IS'' AND ANY
+ * 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 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
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "JSZombie.h"
+#include "ClassInfo.h"
+
+#if ENABLE(JSC_ZOMBIES)
+
+namespace JSC {
+
+const ClassInfo JSZombie::s_info = { "Zombie", 0, 0, 0 };
+
+Structure* JSZombie::leakedZombieStructure() {
+    static Structure* structure = 0;
+    if (!structure) {
+        Structure::startIgnoringLeaks();
+        structure = Structure::create(jsNull(), TypeInfo(UnspecifiedType)).releaseRef();
+        Structure::stopIgnoringLeaks();
+    }
+    return structure;
+}
+
+}
+
+#endif // ENABLE(JSC_ZOMBIES)
diff --git a/JavaScriptCore/runtime/JSZombie.h b/JavaScriptCore/runtime/JSZombie.h
new file mode 100644
index 0000000..8b33ea6
--- /dev/null
+++ b/JavaScriptCore/runtime/JSZombie.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2009 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    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 INC. ``AS IS'' AND ANY
+ * 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 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
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#ifndef JSZombie_h
+#define JSZombie_h
+
+#include "JSCell.h"
+
+#if ENABLE(JSC_ZOMBIES)
+namespace JSC {
+
+class JSZombie : public JSCell {
+public:
+    JSZombie(const ClassInfo* oldInfo, Structure* structure)
+        : JSCell(structure)
+        , m_oldInfo(oldInfo)
+    {
+    }
+    virtual bool isZombie() const { return true; }
+    virtual const ClassInfo* classInfo() const { return &s_info; }
+    static Structure* leakedZombieStructure();
+
+    virtual bool isGetterSetter() const { ASSERT_NOT_REACHED(); return false; }
+    virtual bool isAPIValueWrapper() const { ASSERT_NOT_REACHED(); return false; }
+    virtual bool isPropertyNameIterator() const { ASSERT_NOT_REACHED(); return false; }
+    virtual CallType getCallData(CallData&) { ASSERT_NOT_REACHED(); return CallTypeNone; }
+    virtual ConstructType getConstructData(ConstructData&) { ASSERT_NOT_REACHED(); return ConstructTypeNone; }
+    virtual bool getUInt32(uint32_t&) const { ASSERT_NOT_REACHED(); return false; }
+    virtual JSValue toPrimitive(ExecState*, PreferredPrimitiveType) const { ASSERT_NOT_REACHED(); return jsNull(); }
+    virtual bool getPrimitiveNumber(ExecState*, double&, JSValue&) { ASSERT_NOT_REACHED(); return false; }
+    virtual bool toBoolean(ExecState*) const { ASSERT_NOT_REACHED(); return false; }
+    virtual double toNumber(ExecState*) const { ASSERT_NOT_REACHED(); return 0.0; }
+    virtual UString toString(ExecState*) const { ASSERT_NOT_REACHED(); return ""; }
+    virtual JSObject* toObject(ExecState*) const { ASSERT_NOT_REACHED(); return 0; }
+    virtual void markChildren(MarkStack&) { ASSERT_NOT_REACHED(); }
+    virtual void put(ExecState*, const Identifier&, JSValue, PutPropertySlot&) { ASSERT_NOT_REACHED(); }
+    virtual void put(ExecState*, unsigned, JSValue) { ASSERT_NOT_REACHED(); }
+    virtual bool deleteProperty(ExecState*, const Identifier&) { ASSERT_NOT_REACHED(); return false; }
+    virtual bool deleteProperty(ExecState*, unsigned) { ASSERT_NOT_REACHED(); return false; }
+    virtual JSObject* toThisObject(ExecState*) const { ASSERT_NOT_REACHED(); return 0; }
+    virtual UString toThisString(ExecState*) const { ASSERT_NOT_REACHED(); return ""; }
+    virtual JSString* toThisJSString(ExecState*) { ASSERT_NOT_REACHED(); return 0; }
+    virtual JSValue getJSNumber() { ASSERT_NOT_REACHED(); return jsNull(); }
+    virtual bool getOwnPropertySlot(ExecState*, const Identifier&, PropertySlot&) { ASSERT_NOT_REACHED(); return false; }
+    virtual bool getOwnPropertySlot(ExecState*, unsigned, PropertySlot&) { ASSERT_NOT_REACHED(); return false; }
+    
+    static const ClassInfo s_info;
+private:
+    const ClassInfo* m_oldInfo;
+};
+
+}
+
+#endif // ENABLE(JSC_ZOMBIES)
+
+#endif // JSZombie_h
diff --git a/JavaScriptCore/runtime/MarkStack.h b/JavaScriptCore/runtime/MarkStack.h
index ea09f54..a114ae0 100644
--- a/JavaScriptCore/runtime/MarkStack.h
+++ b/JavaScriptCore/runtime/MarkStack.h
@@ -153,7 +153,7 @@ namespace JSC {
                 ASSERT(0 == (size % MarkStack::pageSize()));
                 if (size == m_allocated)
                     return;
-#if PLATFORM(WIN) || PLATFORM(SYMBIAN)
+#if PLATFORM(WIN_OS) || PLATFORM(SYMBIAN)
                 // We cannot release a part of a region with VirtualFree.  To get around this,
                 // we'll release the entire region and reallocate the size that we want.
                 releaseStack(m_data, m_allocated);
diff --git a/JavaScriptCore/runtime/MathObject.cpp b/JavaScriptCore/runtime/MathObject.cpp
index e8b7b97..98ff3ba 100644
--- a/JavaScriptCore/runtime/MathObject.cpp
+++ b/JavaScriptCore/runtime/MathObject.cpp
@@ -96,7 +96,6 @@ MathObject::MathObject(ExecState* exec, NonNullPassRefPtr<Structure> structure)
     putDirectWithoutTransition(Identifier(exec, "PI"), jsNumber(exec, piDouble), DontDelete | DontEnum | ReadOnly);
     putDirectWithoutTransition(Identifier(exec, "SQRT1_2"), jsNumber(exec, sqrt(0.5)), DontDelete | DontEnum | ReadOnly);
     putDirectWithoutTransition(Identifier(exec, "SQRT2"), jsNumber(exec, sqrt(2.0)), DontDelete | DontEnum | ReadOnly);
-    WTF::initializeWeakRandomNumberGenerator();
 }
 
 // ECMA 15.8
@@ -120,22 +119,22 @@ JSValue JSC_HOST_CALL mathProtoFuncAbs(ExecState* exec, JSObject*, JSValue, cons
 
 JSValue JSC_HOST_CALL mathProtoFuncACos(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, acos(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, acos(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncASin(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, asin(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, asin(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncATan(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, atan(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, atan(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncATan2(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, atan2(args.at(0).toNumber(exec), args.at(1).toNumber(exec)));
+    return jsDoubleNumber(exec, atan2(args.at(0).toNumber(exec), args.at(1).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncCeil(ExecState* exec, JSObject*, JSValue, const ArgList& args)
@@ -145,12 +144,12 @@ JSValue JSC_HOST_CALL mathProtoFuncCeil(ExecState* exec, JSObject*, JSValue, con
 
 JSValue JSC_HOST_CALL mathProtoFuncCos(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, cos(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, cos(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncExp(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, exp(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, exp(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncFloor(ExecState* exec, JSObject*, JSValue, const ArgList& args)
@@ -160,7 +159,7 @@ JSValue JSC_HOST_CALL mathProtoFuncFloor(ExecState* exec, JSObject*, JSValue, co
 
 JSValue JSC_HOST_CALL mathProtoFuncLog(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, log(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, log(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncMax(ExecState* exec, JSObject*, JSValue, const ArgList& args)
@@ -211,7 +210,7 @@ JSValue JSC_HOST_CALL mathProtoFuncPow(ExecState* exec, JSObject*, JSValue, cons
 
 JSValue JSC_HOST_CALL mathProtoFuncRandom(ExecState* exec, JSObject*, JSValue, const ArgList&)
 {
-    return jsNumber(exec, WTF::weakRandomNumber());
+    return jsDoubleNumber(exec, exec->globalData().weakRandom.get());
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncRound(ExecState* exec, JSObject*, JSValue, const ArgList& args)
@@ -224,17 +223,17 @@ JSValue JSC_HOST_CALL mathProtoFuncRound(ExecState* exec, JSObject*, JSValue, co
 
 JSValue JSC_HOST_CALL mathProtoFuncSin(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, sin(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, sin(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncSqrt(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, sqrt(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, sqrt(args.at(0).toNumber(exec)));
 }
 
 JSValue JSC_HOST_CALL mathProtoFuncTan(ExecState* exec, JSObject*, JSValue, const ArgList& args)
 {
-    return jsNumber(exec, tan(args.at(0).toNumber(exec)));
+    return jsDoubleNumber(exec, tan(args.at(0).toNumber(exec)));
 }
 
 } // namespace JSC
diff --git a/JavaScriptCore/runtime/NativeErrorConstructor.cpp b/JavaScriptCore/runtime/NativeErrorConstructor.cpp
index c655fae..403fc7e 100644
--- a/JavaScriptCore/runtime/NativeErrorConstructor.cpp
+++ b/JavaScriptCore/runtime/NativeErrorConstructor.cpp
@@ -33,7 +33,7 @@ ASSERT_CLASS_FITS_IN_CELL(NativeErrorConstructor);
 const ClassInfo NativeErrorConstructor::info = { "Function", &InternalFunction::info, 0, 0 };
 
 NativeErrorConstructor::NativeErrorConstructor(ExecState* exec, NonNullPassRefPtr<Structure> structure, NativeErrorPrototype* nativeErrorPrototype)
-    : InternalFunction(&exec->globalData(), structure, Identifier(exec, nativeErrorPrototype->getDirect(exec->propertyNames().name).getString()))
+    : InternalFunction(&exec->globalData(), structure, Identifier(exec, nativeErrorPrototype->getDirect(exec->propertyNames().name).getString(exec)))
     , m_errorStructure(ErrorInstance::createStructure(nativeErrorPrototype))
 {
     putDirect(exec->propertyNames().length, jsNumber(exec, 1), DontDelete | ReadOnly | DontEnum); // ECMA 15.11.7.5
diff --git a/JavaScriptCore/runtime/ObjectConstructor.cpp b/JavaScriptCore/runtime/ObjectConstructor.cpp
index 837d5a6..693efc3 100644
--- a/JavaScriptCore/runtime/ObjectConstructor.cpp
+++ b/JavaScriptCore/runtime/ObjectConstructor.cpp
@@ -148,14 +148,14 @@ static bool toPropertyDescriptor(ExecState* exec, JSValue in, PropertyDescriptor
     }
     JSObject* description = asObject(in);
 
-    PropertySlot enumerableSlot;
+    PropertySlot enumerableSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().enumerable, enumerableSlot)) {
         desc.setEnumerable(enumerableSlot.getValue(exec, exec->propertyNames().enumerable).toBoolean(exec));
         if (exec->hadException())
             return false;
     }
 
-    PropertySlot configurableSlot;
+    PropertySlot configurableSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().configurable, configurableSlot)) {
         desc.setConfigurable(configurableSlot.getValue(exec, exec->propertyNames().configurable).toBoolean(exec));
         if (exec->hadException())
@@ -163,21 +163,21 @@ static bool toPropertyDescriptor(ExecState* exec, JSValue in, PropertyDescriptor
     }
 
     JSValue value;
-    PropertySlot valueSlot;
+    PropertySlot valueSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().value, valueSlot)) {
         desc.setValue(valueSlot.getValue(exec, exec->propertyNames().value));
         if (exec->hadException())
             return false;
     }
 
-    PropertySlot writableSlot;
+    PropertySlot writableSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().writable, writableSlot)) {
         desc.setWritable(writableSlot.getValue(exec, exec->propertyNames().writable).toBoolean(exec));
         if (exec->hadException())
             return false;
     }
 
-    PropertySlot getSlot;
+    PropertySlot getSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().get, getSlot)) {
         JSValue get = getSlot.getValue(exec, exec->propertyNames().get);
         if (exec->hadException())
@@ -193,7 +193,7 @@ static bool toPropertyDescriptor(ExecState* exec, JSValue in, PropertyDescriptor
         desc.setGetter(get);
     }
 
-    PropertySlot setSlot;
+    PropertySlot setSlot(description);
     if (description->getPropertySlot(exec, exec->propertyNames().set, setSlot)) {
         JSValue set = setSlot.getValue(exec, exec->propertyNames().set);
         if (exec->hadException())
diff --git a/JavaScriptCore/runtime/Operations.cpp b/JavaScriptCore/runtime/Operations.cpp
index 093bbec..0e1887c 100644
--- a/JavaScriptCore/runtime/Operations.cpp
+++ b/JavaScriptCore/runtime/Operations.cpp
@@ -29,10 +29,6 @@
 #include <stdio.h>
 #include <wtf/MathExtras.h>
 
-#if HAVE(FLOAT_H)
-#include <float.h>
-#endif
-
 namespace JSC {
 
 bool JSValue::equalSlowCase(ExecState* exec, JSValue v1, JSValue v2)
@@ -40,9 +36,9 @@ bool JSValue::equalSlowCase(ExecState* exec, JSValue v1, JSValue v2)
     return equalSlowCaseInline(exec, v1, v2);
 }
 
-bool JSValue::strictEqualSlowCase(JSValue v1, JSValue v2)
+bool JSValue::strictEqualSlowCase(ExecState* exec, JSValue v1, JSValue v2)
 {
-    return strictEqualSlowCaseInline(v1, v2);
+    return strictEqualSlowCaseInline(exec, v1, v2);
 }
 
 NEVER_INLINE JSValue throwOutOfMemoryError(ExecState* exec)
@@ -58,12 +54,13 @@ NEVER_INLINE JSValue jsAddSlowCase(CallFrame* callFrame, JSValue v1, JSValue v2)
     JSValue p1 = v1.toPrimitive(callFrame);
     JSValue p2 = v2.toPrimitive(callFrame);
 
-    if (p1.isString() || p2.isString()) {
-        RefPtr<UString::Rep> value = concatenate(p1.toString(callFrame).rep(), p2.toString(callFrame).rep());
-        if (!value)
-            return throwOutOfMemoryError(callFrame);
-        return jsString(callFrame, value.release());
+    if (p1.isString()) {
+        return p2.isString()
+            ? jsString(callFrame, asString(p1), asString(p2))
+            : jsString(callFrame, asString(p1), p2.toString(callFrame));
     }
+    if (p2.isString())
+        return jsString(callFrame, p1.toString(callFrame), asString(p2));
 
     return jsNumber(callFrame, p1.toNumber(callFrame) + p2.toNumber(callFrame));
 }
diff --git a/JavaScriptCore/runtime/Operations.h b/JavaScriptCore/runtime/Operations.h
index 1aa68b3..0289ac2 100644
--- a/JavaScriptCore/runtime/Operations.h
+++ b/JavaScriptCore/runtime/Operations.h
@@ -35,6 +35,99 @@ namespace JSC {
     bool jsIsObjectType(JSValue);
     bool jsIsFunctionType(JSValue);
 
+    ALWAYS_INLINE JSValue jsString(ExecState* exec, JSString* s1, JSString* s2)
+    {
+        if (!s1->length())
+            return s2;
+        if (!s2->length())
+            return s1;
+
+        unsigned ropeLength = s1->ropeLength() + s2->ropeLength();
+        JSGlobalData* globalData = &exec->globalData();
+
+        if (ropeLength <= JSString::s_maxInternalRopeLength)
+            return new (globalData) JSString(globalData, ropeLength, s1, s2);
+
+        unsigned index = 0;
+        RefPtr<JSString::Rope> rope = JSString::Rope::createOrNull(ropeLength);
+        if (UNLIKELY(!rope))
+            return throwOutOfMemoryError(exec);
+        rope->append(index, s1);
+        rope->append(index, s2);
+        ASSERT(index == ropeLength);
+        return new (globalData) JSString(globalData, rope.release());
+    }
+
+    ALWAYS_INLINE JSValue jsString(ExecState* exec, const UString& u1, JSString* s2)
+    {
+        unsigned ropeLength = 1 + s2->ropeLength();
+        JSGlobalData* globalData = &exec->globalData();
+
+        if (ropeLength <= JSString::s_maxInternalRopeLength)
+            return new (globalData) JSString(globalData, ropeLength, u1, s2);
+
+        unsigned index = 0;
+        RefPtr<JSString::Rope> rope = JSString::Rope::createOrNull(ropeLength);
+        if (UNLIKELY(!rope))
+            return throwOutOfMemoryError(exec);
+        rope->append(index, u1);
+        rope->append(index, s2);
+        ASSERT(index == ropeLength);
+        return new (globalData) JSString(globalData, rope.release());
+    }
+
+    ALWAYS_INLINE JSValue jsString(ExecState* exec, JSString* s1, const UString& u2)
+    {
+        unsigned ropeLength = s1->ropeLength() + 1;
+        JSGlobalData* globalData = &exec->globalData();
+
+        if (ropeLength <= JSString::s_maxInternalRopeLength)
+            return new (globalData) JSString(globalData, ropeLength, s1, u2);
+
+        unsigned index = 0;
+        RefPtr<JSString::Rope> rope = JSString::Rope::createOrNull(ropeLength);
+        if (UNLIKELY(!rope))
+            return throwOutOfMemoryError(exec);
+        rope->append(index, s1);
+        rope->append(index, u2);
+        ASSERT(index == ropeLength);
+        return new (globalData) JSString(globalData, rope.release());
+    }
+
+    ALWAYS_INLINE JSValue jsString(ExecState* exec, Register* strings, unsigned count)
+    {
+        ASSERT(count >= 3);
+
+        unsigned ropeLength = 0;
+        for (unsigned i = 0; i < count; ++i) {
+            JSValue v = strings[i].jsValue();
+            if (LIKELY(v.isString()))
+                ropeLength += asString(v)->ropeLength();
+            else
+                ++ropeLength;
+        }
+
+        JSGlobalData* globalData = &exec->globalData();
+        if (ropeLength == 3)
+            return new (globalData) JSString(exec, strings[0].jsValue(), strings[1].jsValue(), strings[2].jsValue());
+
+        RefPtr<JSString::Rope> rope = JSString::Rope::createOrNull(ropeLength);
+        if (UNLIKELY(!rope))
+            return throwOutOfMemoryError(exec);
+
+        unsigned index = 0;
+        for (unsigned i = 0; i < count; ++i) {
+            JSValue v = strings[i].jsValue();
+            if (LIKELY(v.isString()))
+                rope->append(index, asString(v));
+            else
+                rope->append(index, v.toString(exec));
+        }
+
+        ASSERT(index == ropeLength);
+        return new (globalData) JSString(globalData, rope.release());
+    }
+
     // ECMA 11.9.3
     inline bool JSValue::equal(ExecState* exec, JSValue v1, JSValue v2)
     {
@@ -53,7 +146,7 @@ namespace JSC {
             bool s1 = v1.isString();
             bool s2 = v2.isString();
             if (s1 && s2)
-                return asString(v1)->value() == asString(v2)->value();
+                return asString(v1)->value(exec) == asString(v2)->value(exec);
 
             if (v1.isUndefinedOrNull()) {
                 if (v2.isUndefinedOrNull())
@@ -110,17 +203,17 @@ namespace JSC {
     }
 
     // ECMA 11.9.3
-    ALWAYS_INLINE bool JSValue::strictEqualSlowCaseInline(JSValue v1, JSValue v2)
+    ALWAYS_INLINE bool JSValue::strictEqualSlowCaseInline(ExecState* exec, JSValue v1, JSValue v2)
     {
         ASSERT(v1.isCell() && v2.isCell());
 
         if (v1.asCell()->isString() && v2.asCell()->isString())
-            return asString(v1)->value() == asString(v2)->value();
+            return asString(v1)->value(exec) == asString(v2)->value(exec);
 
         return v1 == v2;
     }
 
-    inline bool JSValue::strictEqual(JSValue v1, JSValue v2)
+    inline bool JSValue::strictEqual(ExecState* exec, JSValue v1, JSValue v2)
     {
         if (v1.isInt32() && v2.isInt32())
             return v1 == v2;
@@ -131,7 +224,7 @@ namespace JSC {
         if (!v1.isCell() || !v2.isCell())
             return v1 == v2;
 
-        return strictEqualSlowCaseInline(v1, v2);
+        return strictEqualSlowCaseInline(exec, v1, v2);
     }
 
     inline bool jsLess(CallFrame* callFrame, JSValue v1, JSValue v2)
@@ -146,7 +239,7 @@ namespace JSC {
 
         JSGlobalData* globalData = &callFrame->globalData();
         if (isJSString(globalData, v1) && isJSString(globalData, v2))
-            return asString(v1)->value() < asString(v2)->value();
+            return asString(v1)->value(callFrame) < asString(v2)->value(callFrame);
 
         JSValue p1;
         JSValue p2;
@@ -156,7 +249,7 @@ namespace JSC {
         if (wasNotString1 | wasNotString2)
             return n1 < n2;
 
-        return asString(p1)->value() < asString(p2)->value();
+        return asString(p1)->value(callFrame) < asString(p2)->value(callFrame);
     }
 
     inline bool jsLessEq(CallFrame* callFrame, JSValue v1, JSValue v2)
@@ -171,7 +264,7 @@ namespace JSC {
 
         JSGlobalData* globalData = &callFrame->globalData();
         if (isJSString(globalData, v1) && isJSString(globalData, v2))
-            return !(asString(v2)->value() < asString(v1)->value());
+            return !(asString(v2)->value(callFrame) < asString(v1)->value(callFrame));
 
         JSValue p1;
         JSValue p2;
@@ -181,7 +274,7 @@ namespace JSC {
         if (wasNotString1 | wasNotString2)
             return n1 <= n2;
 
-        return !(asString(p2)->value() < asString(p1)->value());
+        return !(asString(p2)->value(callFrame) < asString(p1)->value(callFrame));
     }
 
     // Fast-path choices here are based on frequency data from SunSpider:
@@ -195,29 +288,14 @@ namespace JSC {
 
     ALWAYS_INLINE JSValue jsAdd(CallFrame* callFrame, JSValue v1, JSValue v2)
     {
-        double left;
-        double right = 0.0;
-
-        bool rightIsNumber = v2.getNumber(right);
-        if (rightIsNumber && v1.getNumber(left))
+        double left = 0.0, right;
+        if (v1.getNumber(left), v2.getNumber(right))
             return jsNumber(callFrame, left + right);
         
-        bool leftIsString = v1.isString();
-        if (leftIsString && v2.isString()) {
-            RefPtr<UString::Rep> value = concatenate(asString(v1)->value().rep(), asString(v2)->value().rep());
-            if (!value)
-                return throwOutOfMemoryError(callFrame);
-            return jsString(callFrame, value.release());
-        }
-
-        if (rightIsNumber & leftIsString) {
-            RefPtr<UString::Rep> value = v2.isInt32() ?
-                concatenate(asString(v1)->value().rep(), v2.asInt32()) :
-                concatenate(asString(v1)->value().rep(), right);
-
-            if (!value)
-                return throwOutOfMemoryError(callFrame);
-            return jsString(callFrame, value.release());
+        if (v1.isString()) {
+            return v2.isString()
+                ? jsString(callFrame, asString(v1), asString(v2))
+                : jsString(callFrame, asString(v1), v2.toString(callFrame));
         }
 
         // All other cases are pretty uncommon
@@ -243,7 +321,7 @@ namespace JSC {
             // Since we're accessing a prototype in a loop, it's a good bet that it
             // should not be treated as a dictionary.
             if (cell->structure()->isDictionary())
-                asObject(cell)->setStructure(Structure::fromDictionaryTransition(cell->structure()));
+                asObject(cell)->flattenDictionaryObject();
 
             ++count;
         }
@@ -265,7 +343,7 @@ namespace JSC {
             // Since we're accessing a prototype in a loop, it's a good bet that it
             // should not be treated as a dictionary.
             if (base->structure()->isDictionary())
-                asObject(base)->setStructure(Structure::fromDictionaryTransition(base->structure()));
+                asObject(base)->flattenDictionaryObject();
 
             ++count;
         }
@@ -293,52 +371,6 @@ namespace JSC {
         ASSERT_NOT_REACHED();
         return JSValue();
     }
-
-    ALWAYS_INLINE JSValue concatenateStrings(CallFrame* callFrame, Register* strings, unsigned count)
-    {
-        ASSERT(count >= 3);
-
-        // Estimate the amount of space required to hold the entire string.  If all
-        // arguments are strings, we can easily calculate the exact amount of space
-        // required.  For any other arguments, for now let's assume they may require
-        // 11 UChars of storage.  This is enouch to hold any int, and likely is also
-        // reasonable for the other immediates.  We may want to come back and tune
-        // this value at some point.
-        unsigned bufferSize = 0;
-        for (unsigned i = 0; i < count; ++i) {
-            JSValue v = strings[i].jsValue();
-            if (LIKELY(v.isString()))
-                bufferSize += asString(v)->value().size();
-            else
-                bufferSize += 11;
-        }
-
-        // Allocate an output string to store the result.
-        // If the first argument is a String, and if it has the capacity (or can grow
-        // its capacity) to hold the entire result then use this as a base to concatenate
-        // onto.  Otherwise, allocate a new empty output buffer.
-        JSValue firstValue = strings[0].jsValue();
-        RefPtr<UString::Rep> resultRep;
-        if (firstValue.isString() && (resultRep = asString(firstValue)->value().rep())->reserveCapacity(bufferSize)) {
-            // We're going to concatenate onto the first string - remove it from the list of items to be appended.
-            ++strings;
-            --count;
-        } else
-            resultRep = UString::Rep::createEmptyBuffer(bufferSize);
-        UString result(resultRep);
-
-        // Loop over the operands, writing them into the output buffer.
-        for (unsigned i = 0; i < count; ++i) {
-            JSValue v = strings[i].jsValue();
-            if (LIKELY(v.isString()))
-                result.append(asString(v)->value());
-            else
-                result.append(v.toString(callFrame));
-        }
-
-        return jsString(callFrame, result);
-    }
-
 } // namespace JSC
 
 #endif // Operations_h
diff --git a/JavaScriptCore/runtime/PropertyDescriptor.cpp b/JavaScriptCore/runtime/PropertyDescriptor.cpp
index 4db814f..558ae28 100644
--- a/JavaScriptCore/runtime/PropertyDescriptor.cpp
+++ b/JavaScriptCore/runtime/PropertyDescriptor.cpp
@@ -153,15 +153,15 @@ void PropertyDescriptor::setGetter(JSValue getter)
     m_attributes &= ~ReadOnly;
 }
 
-bool PropertyDescriptor::equalTo(const PropertyDescriptor& other) const
+bool PropertyDescriptor::equalTo(ExecState* exec, const PropertyDescriptor& other) const
 {
     if (!other.m_value == m_value ||
         !other.m_getter == m_getter ||
         !other.m_setter == m_setter)
         return false;
-    return (!m_value || JSValue::strictEqual(other.m_value, m_value)) && 
-           (!m_getter || JSValue::strictEqual(other.m_getter, m_getter)) && 
-           (!m_setter || JSValue::strictEqual(other.m_setter, m_setter)) &&
+    return (!m_value || JSValue::strictEqual(exec, other.m_value, m_value)) && 
+           (!m_getter || JSValue::strictEqual(exec, other.m_getter, m_getter)) && 
+           (!m_setter || JSValue::strictEqual(exec, other.m_setter, m_setter)) &&
            attributesEqual(other);
 }
 
diff --git a/JavaScriptCore/runtime/PropertyDescriptor.h b/JavaScriptCore/runtime/PropertyDescriptor.h
index 40bec86..ff9f160 100644
--- a/JavaScriptCore/runtime/PropertyDescriptor.h
+++ b/JavaScriptCore/runtime/PropertyDescriptor.h
@@ -61,7 +61,7 @@ namespace JSC {
         bool configurablePresent() const { return m_seenAttributes & ConfigurablePresent; }
         bool setterPresent() const { return m_setter; }
         bool getterPresent() const { return m_getter; }
-        bool equalTo(const PropertyDescriptor& other) const;
+        bool equalTo(ExecState* exec, const PropertyDescriptor& other) const;
         bool attributesEqual(const PropertyDescriptor& other) const;
         unsigned attributesWithOverride(const PropertyDescriptor& other) const;
     private:
diff --git a/JavaScriptCore/runtime/RegExpConstructor.cpp b/JavaScriptCore/runtime/RegExpConstructor.cpp
index c609e08..e5c6909 100644
--- a/JavaScriptCore/runtime/RegExpConstructor.cpp
+++ b/JavaScriptCore/runtime/RegExpConstructor.cpp
@@ -132,6 +132,8 @@ void RegExpMatchesArray::fillArrayInstance(ExecState* exec)
         int start = d->lastOvector()[2 * i];
         if (start >= 0)
             JSArray::put(exec, i, jsSubstring(exec, d->lastInput, start, d->lastOvector()[2 * i + 1] - start));
+        else
+            JSArray::put(exec, i, jsUndefined());
     }
 
     PutPropertySlot slot;
diff --git a/JavaScriptCore/runtime/StringObject.cpp b/JavaScriptCore/runtime/StringObject.cpp
index 7216d3a..f23a20d 100644
--- a/JavaScriptCore/runtime/StringObject.cpp
+++ b/JavaScriptCore/runtime/StringObject.cpp
@@ -79,12 +79,16 @@ bool StringObject::deleteProperty(ExecState* exec, const Identifier& propertyNam
 {
     if (propertyName == exec->propertyNames().length)
         return false;
+    bool isStrictUInt32;
+    unsigned i = propertyName.toStrictUInt32(&isStrictUInt32);
+    if (isStrictUInt32 && internalValue()->canGetIndex(i))
+        return false;
     return JSObject::deleteProperty(exec, propertyName);
 }
 
 void StringObject::getOwnPropertyNames(ExecState* exec, PropertyNameArray& propertyNames)
 {
-    int size = internalValue()->value().size();
+    int size = internalValue()->length();
     for (int i = 0; i < size; ++i)
         propertyNames.add(Identifier(exec, UString::from(i)));
     return JSObject::getOwnPropertyNames(exec, propertyNames);
diff --git a/JavaScriptCore/runtime/StringPrototype.cpp b/JavaScriptCore/runtime/StringPrototype.cpp
index a0713b8..32f9e6b 100644
--- a/JavaScriptCore/runtime/StringPrototype.cpp
+++ b/JavaScriptCore/runtime/StringPrototype.cpp
@@ -224,7 +224,7 @@ static inline int localeCompare(const UString& a, const UString& b)
 JSValue JSC_HOST_CALL stringProtoFuncReplace(ExecState* exec, JSObject*, JSValue thisValue, const ArgList& args)
 {
     JSString* sourceVal = thisValue.toThisJSString(exec);
-    const UString& source = sourceVal->value();
+    const UString& source = sourceVal->value(exec);
 
     JSValue pattern = args.at(0);
 
@@ -281,7 +281,8 @@ JSValue JSC_HOST_CALL stringProtoFuncReplace(ExecState* exec, JSObject*, JSValue
                 cachedCall.setArgument(i++, sourceVal);
                 
                 cachedCall.setThis(exec->globalThisValue());
-                replacements.append(cachedCall.call().toString(cachedCall.newCallFrame()));
+                JSValue result = cachedCall.call();
+                replacements.append(result.toString(cachedCall.newCallFrame(exec)));
                 if (exec->hadException())
                     break;
 
@@ -469,6 +470,11 @@ JSValue JSC_HOST_CALL stringProtoFuncLastIndexOf(ExecState* exec, JSObject*, JSV
         dpos = 0;
     else if (!(dpos <= len)) // true for NaN
         dpos = len;
+#if PLATFORM(SYMBIAN)
+    // Work around for broken NaN compare operator
+    else if (isnan(dpos))
+        dpos = len;
+#endif
     return jsNumber(exec, s.rfind(u2, static_cast<int>(dpos)));
 }
 
@@ -691,7 +697,7 @@ JSValue JSC_HOST_CALL stringProtoFuncSubstring(ExecState* exec, JSObject*, JSVal
 JSValue JSC_HOST_CALL stringProtoFuncToLowerCase(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
 {
     JSString* sVal = thisValue.toThisJSString(exec);
-    const UString& s = sVal->value();
+    const UString& s = sVal->value(exec);
 
     int sSize = s.size();
     if (!sSize)
@@ -725,7 +731,7 @@ JSValue JSC_HOST_CALL stringProtoFuncToLowerCase(ExecState* exec, JSObject*, JSV
 JSValue JSC_HOST_CALL stringProtoFuncToUpperCase(ExecState* exec, JSObject*, JSValue thisValue, const ArgList&)
 {
     JSString* sVal = thisValue.toThisJSString(exec);
-    const UString& s = sVal->value();
+    const UString& s = sVal->value(exec);
 
     int sSize = s.size();
     if (!sSize)
diff --git a/JavaScriptCore/runtime/Structure.cpp b/JavaScriptCore/runtime/Structure.cpp
index 65b62f9..e4c9ac3 100644
--- a/JavaScriptCore/runtime/Structure.cpp
+++ b/JavaScriptCore/runtime/Structure.cpp
@@ -77,6 +77,8 @@ static HashSet<Structure*>& ignoreSet = *(new HashSet<Structure*>);
 static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
 #endif
 
+static int comparePropertyMapEntryIndices(const void* a, const void* b);
+
 void Structure::dumpStatistics()
 {
 #if DUMP_STRUCTURE_ID_STATISTICS
@@ -534,20 +536,47 @@ PassRefPtr<Structure> Structure::toUncacheableDictionaryTransition(Structure* st
     return toDictionaryTransition(structure, UncachedDictionaryKind);
 }
 
-PassRefPtr<Structure> Structure::fromDictionaryTransition(Structure* structure)
+PassRefPtr<Structure> Structure::flattenDictionaryStructure(JSObject* object)
 {
-    ASSERT(structure->isDictionary());
-
-    // Since dictionary Structures are not shared, and no opcodes specialize
-    // for them, we don't need to allocate a new Structure when transitioning
-    // to non-dictionary status.
-
-    // FIMXE: We can make this more efficient by canonicalizing the Structure (draining the
-    // deleted offsets vector) before transitioning from dictionary. 
-    if (!structure->m_propertyTable || !structure->m_propertyTable->deletedOffsets || structure->m_propertyTable->deletedOffsets->isEmpty())
-        structure->m_dictionaryKind = NoneDictionaryKind;
+    ASSERT(isDictionary());
+    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);
+
+        // 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
+        Vector<JSValue> values(propertyCount);
+        unsigned anonymousSlotCount = m_propertyTable->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;
+        }
+        
+        // Copy the original property values into their final locations
+        for (unsigned i = 0; i < propertyCount; i++)
+            object->putDirectOffset(anonymousSlotCount + i, values[i]);
+
+        if (m_propertyTable->deletedOffsets) {
+            delete m_propertyTable->deletedOffsets;
+            m_propertyTable->deletedOffsets = 0;
+        }
+    }
 
-    return structure;
+    m_dictionaryKind = NoneDictionaryKind;
+    return this;
 }
 
 size_t Structure::addPropertyWithoutTransition(const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
@@ -556,8 +585,6 @@ size_t Structure::addPropertyWithoutTransition(const Identifier& propertyName, u
     materializePropertyMapIfNecessary();
 
     m_isPinnedPropertyTable = true;
-    if (attributes & DontEnum)
-        m_hasNonEnumerableProperties = true;
 
     size_t offset = put(propertyName, attributes, specificValue);
     if (propertyStorageSize() > propertyStorageCapacity())
@@ -739,6 +766,9 @@ size_t Structure::put(const Identifier& propertyName, unsigned attributes, JSCel
 
     checkConsistency();
 
+    if (attributes & DontEnum)
+        m_hasNonEnumerableProperties = true;
+
     UString::Rep* rep = propertyName._ustring.rep();
 
     if (!m_propertyTable)
@@ -1003,7 +1033,7 @@ void Structure::rehashPropertyMapHashTable(unsigned newTableSize)
     checkConsistency();
 }
 
-static int comparePropertyMapEntryIndices(const void* a, const void* b)
+int comparePropertyMapEntryIndices(const void* a, const void* b)
 {
     unsigned ia = static_cast<PropertyMapEntry* const*>(a)[0]->index;
     unsigned ib = static_cast<PropertyMapEntry* const*>(b)[0]->index;
@@ -1025,6 +1055,7 @@ void Structure::getEnumerablePropertyNames(PropertyNameArray& propertyNames)
         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)) {
                 PropertyMapEntry* value = &m_propertyTable->entries()[k];
                 int j;
@@ -1112,6 +1143,7 @@ void Structure::checkConsistency()
 
     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;
         if (!rep)
             continue;
diff --git a/JavaScriptCore/runtime/Structure.h b/JavaScriptCore/runtime/Structure.h
index f355c53..c6b7d91 100644
--- a/JavaScriptCore/runtime/Structure.h
+++ b/JavaScriptCore/runtime/Structure.h
@@ -74,7 +74,8 @@ namespace JSC {
         static PassRefPtr<Structure> getterSetterTransition(Structure*);
         static PassRefPtr<Structure> toCacheableDictionaryTransition(Structure*);
         static PassRefPtr<Structure> toUncacheableDictionaryTransition(Structure*);
-        static PassRefPtr<Structure> fromDictionaryTransition(Structure*);
+
+        PassRefPtr<Structure> flattenDictionaryStructure(JSObject*);
 
         ~Structure();
 
@@ -306,7 +307,7 @@ namespace JSC {
         TransitionTable* transitionTable = new TransitionTable;
         setTransitionTable(transitionTable);
         if (existingTransition)
-            add(make_pair(existingTransition->m_nameInPrevious.get(), existingTransition->m_attributesInPrevious), existingTransition, existingTransition->m_specificValueInPrevious);
+            add(std::make_pair(existingTransition->m_nameInPrevious.get(), existingTransition->m_attributesInPrevious), existingTransition, existingTransition->m_specificValueInPrevious);
     }
 } // namespace JSC
 
diff --git a/JavaScriptCore/runtime/UString.cpp b/JavaScriptCore/runtime/UString.cpp
index e66ca93..50d23c4 100644
--- a/JavaScriptCore/runtime/UString.cpp
+++ b/JavaScriptCore/runtime/UString.cpp
@@ -30,12 +30,12 @@
 #include "Identifier.h"
 #include "Operations.h"
 #include <ctype.h>
-#include <float.h>
 #include <limits.h>
 #include <limits>
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <wtf/ASCIICType.h>
 #include <wtf/Assertions.h>
 #include <wtf/MathExtras.h>
@@ -44,9 +44,6 @@
 #include <wtf/unicode/UTF8.h>
 #include <wtf/StringExtras.h>
 
-#if HAVE(STRING_H)
-#include <string.h>
-#endif
 #if HAVE(STRINGS_H)
 #include <strings.h>
 #endif
@@ -578,11 +575,33 @@ static PassRefPtr<UString::Rep> createRep(const char* c)
 
 }
 
+static inline PassRefPtr<UString::Rep> createRep(const char* c, int length)
+{
+    if (!c)
+        return &UString::Rep::null();
+
+    if (!length)
+        return &UString::Rep::empty();
+
+    UChar* d;
+    if (!allocChars(length).getValue(d))
+        return &UString::Rep::null();
+
+    for (int i = 0; i < length; i++)
+        d[i] = static_cast<unsigned char>(c[i]); // use unsigned char to zero-extend instead of sign-extend
+    return UString::Rep::create(d, length);
+}
+
 UString::UString(const char* c)
     : m_rep(createRep(c))
 {
 }
 
+UString::UString(const char* c, int length)
+    : m_rep(createRep(c, length))
+{
+}
+
 UString::UString(const UChar* c, int length)
 {
     if (length == 0) 
@@ -1025,69 +1044,10 @@ UString UString::from(long l)
 
 UString UString::from(double d)
 {
-    // avoid ever printing -NaN, in JS conceptually there is only one NaN value
-    if (isnan(d))
-        return "NaN";
-    if (!d)
-        return "0"; // -0 -> "0"
-
-    char buf[80];
-    int decimalPoint;
-    int sign;
-    
-    char result[80];
-    WTF::dtoa(result, d, 0, &decimalPoint, &sign, NULL);
-    int length = static_cast<int>(strlen(result));
-  
-    int i = 0;
-    if (sign)
-        buf[i++] = '-';
-  
-    if (decimalPoint <= 0 && decimalPoint > -6) {
-        buf[i++] = '0';
-        buf[i++] = '.';
-        for (int j = decimalPoint; j < 0; j++)
-            buf[i++] = '0';
-        strcpy(buf + i, result);
-    } else if (decimalPoint <= 21 && decimalPoint > 0) {
-        if (length <= decimalPoint) {
-            strcpy(buf + i, result);
-            i += length;
-            for (int j = 0; j < decimalPoint - length; j++)
-                buf[i++] = '0';
-            buf[i] = '\0';
-        } else {
-            strncpy(buf + i, result, decimalPoint);
-            i += decimalPoint;
-            buf[i++] = '.';
-            strcpy(buf + i, result + decimalPoint);
-        }
-    } else if (result[0] < '0' || result[0] > '9')
-        strcpy(buf + i, result);
-    else {
-        buf[i++] = result[0];
-        if (length > 1) {
-            buf[i++] = '.';
-            strcpy(buf + i, result + 1);
-            i += length - 1;
-        }
-        
-        buf[i++] = 'e';
-        buf[i++] = (decimalPoint >= 0) ? '+' : '-';
-        // decimalPoint can't be more than 3 digits decimal given the
-        // nature of float representation
-        int exponential = decimalPoint - 1;
-        if (exponential < 0)
-            exponential = -exponential;
-        if (exponential >= 100)
-            buf[i++] = static_cast<char>('0' + exponential / 100);
-        if (exponential >= 10)
-            buf[i++] = static_cast<char>('0' + (exponential % 100) / 10);
-        buf[i++] = static_cast<char>('0' + exponential % 10);
-        buf[i++] = '\0';
-    }
-    
-    return UString(buf);
+    DtoaBuffer buffer;
+    unsigned length;
+    doubleToStringInJavaScriptFormat(d, buffer, &length);
+    return UString(buffer, length);
 }
 
 UString UString::spliceSubstringsWithSeparators(const Range* substringRanges, int rangeCount, const UString* separators, int separatorCount) const
diff --git a/JavaScriptCore/runtime/UString.h b/JavaScriptCore/runtime/UString.h
index c4dad2a..9b046f2 100644
--- a/JavaScriptCore/runtime/UString.h
+++ b/JavaScriptCore/runtime/UString.h
@@ -235,7 +235,10 @@ namespace JSC {
 
     public:
         UString();
+        // Constructor for null-terminated ASCII string.
         UString(const char*);
+        // Constructor for non-null-terminated ASCII string.
+        UString(const char*, int length);
         UString(const UChar*, int length);
         UString(UChar*, int length, bool copy);
 
diff --git a/JavaScriptCore/runtime/WeakRandom.h b/JavaScriptCore/runtime/WeakRandom.h
new file mode 100644
index 0000000..ff3995e
--- /dev/null
+++ b/JavaScriptCore/runtime/WeakRandom.h
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2009 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    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 INC. ``AS IS'' AND ANY
+ * 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 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
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ *
+ *
+ * Copyright (c) 2009 Ian C. Bullard
+ * 
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following
+ * conditions:
+ * 
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef WeakRandom_h
+#define WeakRandom_h
+
+#include <limits.h>
+#include <wtf/StdLibExtras.h>
+
+namespace JSC {
+
+class WeakRandom {
+public:
+    WeakRandom(unsigned seed)
+        : m_low(seed ^ 0x49616E42)
+        , m_high(seed)
+    {
+    }
+
+    double get()
+    {
+        return advance() / (UINT_MAX + 1.0);
+    }
+
+private:
+    unsigned advance()
+    {
+        m_high = (m_high << 16) + (m_high >> 16);
+        m_high += m_low;
+        m_low += m_high;
+        return m_high;
+    }
+
+    unsigned m_low;
+    unsigned m_high;
+};
+
+} // namespace JSC
+
+#endif // WeakRandom_h