Rework QJSValue internals

Use a flagged pointer to either store a pointer to a
QV4::Value (from the persistent storage) or a pointer to
a QVariant in QJSValue::d. Like this we don't need to malloc
to create a QJSValue for most use cases.

Significantly reduces the memory consumption of QJSValue and
speeds it up a lot.

Change-Id: I10902cc4b6cc3f43d3f816875dc6c4bbb6b4490f
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

11 files changed, 354 insertions, 274 deletions

diff --git a/src/imports/statemachine/signaltransition.cpp b/src/imports/statemachine/signaltransition.cpp
index 41286d84c8..1b18444358 100644
--- a/src/imports/statemachine/signaltransition.cpp
+++ b/src/imports/statemachine/signaltransition.cpp
@@ -95,7 +95,7 @@ void SignalTransition::setSignal(const QJSValue &signal)
     QV4::ExecutionEngine *jsEngine = QV8Engine::getV4(QQmlEngine::contextForObject(this)->engine());
     QV4::Scope scope(jsEngine);
 
-    QV4::Scoped<QV4::QObjectMethod> qobjectSignal(scope, QJSValuePrivate::get(m_signal)->getValue(jsEngine));
+    QV4::Scoped<QV4::QObjectMethod> qobjectSignal(scope, QJSValuePrivate::convertedToValue(jsEngine, m_signal));
     Q_ASSERT(qobjectSignal);
 
     QObject *sender = qobjectSignal->object();
diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index e82849746f..413e0eedaf 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -250,12 +250,18 @@ void QJSEngine::collectGarbage()
 */
 void QJSEngine::installTranslatorFunctions(const QJSValue &object)
 {
-    QV4::ExecutionEngine *v4 = d->m_v4Engine;
-    QV4::Scope scope(v4);
-    QJSValuePrivate *vp = QJSValuePrivate::get(object);
-    QV4::ScopedObject obj(scope, vp->getValue(v4));
+    QV4::ExecutionEngine *otherEngine = QJSValuePrivate::engine(&object);
+    if (otherEngine && otherEngine != d->m_v4Engine) {
+        qWarning("QJSEngine: Trying to install a translator function from a different engine");
+        return;
+    }
+    QV4::Scope scope(d->m_v4Engine);
+    QV4::ScopedObject obj(scope);
+    QV4::Value *val = QJSValuePrivate::getValue(&object);
+    if (val)
+        obj = val;
     if (!obj)
-        obj = v4->globalObject();
+        obj = scope.engine->globalObject();
 #ifndef QT_NO_TRANSLATION
     obj->defineDefaultProperty(QStringLiteral("qsTranslate"), QV4::GlobalExtensions::method_qsTranslate);
     obj->defineDefaultProperty(QStringLiteral("QT_TRANSLATE_NOOP"), QV4::GlobalExtensions::method_qsTranslateNoOp);
@@ -265,7 +271,7 @@ void QJSEngine::installTranslatorFunctions(const QJSValue &object)
     obj->defineDefaultProperty(QStringLiteral("QT_TRID_NOOP"), QV4::GlobalExtensions::method_qsTrIdNoOp);
 
     // string prototype extension
-    v4->stringPrototype.asObject()->defineDefaultProperty(QStringLiteral("arg"),
+    scope.engine->stringPrototype.asObject()->defineDefaultProperty(QStringLiteral("arg"),
                                                           QV4::GlobalExtensions::method_string_arg);
 #endif
 }
@@ -420,21 +426,21 @@ QJSValue QJSEngine::create(int type, const void *ptr)
 */
 bool QJSEngine::convertV2(const QJSValue &value, int type, void *ptr)
 {
-    QJSValuePrivate *vp = QJSValuePrivate::get(value);
-    QV4::ExecutionEngine *v4 = vp->engine();
+    QV4::ExecutionEngine *v4 = QJSValuePrivate::engine(&value);
     QV4::Value scratch;
-    QV4::Value *val = vp->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(&value, &scratch);
     if (v4) {
         QV4::Scope scope(v4);
         QV4::ScopedValue v(scope, *val);
         return scope.engine->metaTypeFromJS(v, type, ptr);
     }
 
-    Q_ASSERT(vp->persistent.isEmpty());
-
     if (!val) {
-        if (vp->unboundData.userType() == QMetaType::QString) {
-            QString string = vp->unboundData.toString();
+        QVariant *variant = QJSValuePrivate::getVariant(&value);
+        Q_ASSERT(variant);
+
+        if (variant->userType() == QMetaType::QString) {
+            QString string = variant->toString();
             // have a string based value without engine. Do conversion manually
             if (type == QMetaType::Bool) {
                 *reinterpret_cast<bool*>(ptr) = string.length() != 0;
@@ -483,7 +489,7 @@ bool QJSEngine::convertV2(const QJSValue &value, int type, void *ptr)
                 return false;
             }
         } else {
-            return QMetaType::convert(&vp->unboundData.data_ptr(), vp->unboundData.userType(), ptr, type);
+            return QMetaType::convert(&variant->data_ptr(), variant->userType(), ptr, type);
         }
     }
 
diff --git a/src/qml/jsapi/qjsvalue.cpp b/src/qml/jsapi/qjsvalue.cpp
index 479a2d0901..5310b56af1 100644
--- a/src/qml/jsapi/qjsvalue.cpp
+++ b/src/qml/jsapi/qjsvalue.cpp
@@ -48,53 +48,6 @@
 #include <private/qv4mm_p.h>
 #include <private/qv4scopedvalue_p.h>
 
-QV4::ReturnedValue QJSValuePrivate::getValue(QV4::ExecutionEngine *e)
-{
-    QV4::ExecutionEngine *engine = persistent.engine();
-    if (!engine) {
-        persistent = QV4::PersistentValue(e, e->fromVariant(unboundData));
-        unboundData.clear();
-        engine = e;
-    }
-
-    if (engine != e) {
-        qWarning("JSValue can't be reassigned to another engine.");
-        return QV4::Encode::undefined();
-    }
-
-    return persistent.value();
-}
-
-QV4::Value QJSValuePrivate::primitiveValueForUnboundData() const
-{
-    QV4::Value v = QV4::Primitive::emptyValue();
-    switch ((int)unboundData.type()) {
-    case QMetaType::UnknownType:
-    case QMetaType::Void:
-        v = QV4::Encode::undefined();
-        break;
-    case QMetaType::VoidStar:
-        v = QV4::Encode::null();
-        break;
-    case QMetaType::Bool:
-        v = QV4::Encode(unboundData.toBool());
-        break;
-    case QMetaType::Double:
-        v = QV4::Encode(unboundData.toDouble());
-        break;
-    case QMetaType::Int:
-    case QMetaType::Short:
-    case QMetaType::UShort:
-    case QMetaType::Char:
-    case QMetaType::UChar:
-        v = QV4::Encode(unboundData.toInt());
-        break;
-    case QMetaType::UInt:
-        v = QV4::Encode(unboundData.toUInt());
-        break;
-    }
-    return v;
-}
 
 /*!
   \since 5.0
@@ -168,66 +121,66 @@ using namespace QV4;
   Constructs a new QJSValue with a boolean \a value.
 */
 QJSValue::QJSValue(bool value)
-    : d(new QJSValuePrivate(QVariant(value)))
 {
+    QJSValuePrivate::setVariant(this, QVariant(value));
 }
 
 /*!
   \internal
 */
 QJSValue::QJSValue(ExecutionEngine *e, quint64 val)
-    : d(new QJSValuePrivate(e, val))
 {
+    QJSValuePrivate::setValue(this, e, val);
 }
 
 /*!
   Constructs a new QJSValue with a number \a value.
 */
 QJSValue::QJSValue(int value)
-    : d(new QJSValuePrivate(QVariant((double)value)))
 {
+    QJSValuePrivate::setVariant(this, QVariant(value));
 }
 
 /*!
   Constructs a new QJSValue with a number \a value.
 */
 QJSValue::QJSValue(uint value)
-    : d(new QJSValuePrivate(QVariant((double)value)))
 {
+    QJSValuePrivate::setVariant(this, QVariant((double)value));
 }
 
 /*!
   Constructs a new QJSValue with a number \a value.
 */
 QJSValue::QJSValue(double value)
-    : d(new QJSValuePrivate(QVariant(value)))
 {
+    QJSValuePrivate::setVariant(this, QVariant(value));
 }
 
 /*!
   Constructs a new QJSValue with a string \a value.
 */
 QJSValue::QJSValue(const QString& value)
-    : d(new QJSValuePrivate(value))
 {
+    QJSValuePrivate::setVariant(this, QVariant(value));
 }
 
 /*!
   Constructs a new QJSValue with a special \a value.
 */
 QJSValue::QJSValue(SpecialValue value)
-    : d(new QJSValuePrivate)
+    : d(0)
 {
     if (value == NullValue)
-        d->unboundData = QVariant(QMetaType::VoidStar, (void *)0);
+        QJSValuePrivate::setVariant(this, QVariant(QMetaType::VoidStar, (void *)0));
 }
 
 /*!
   Constructs a new QJSValue with a string \a value.
 */
 QJSValue::QJSValue(const QLatin1String &value)
-    : d(new QJSValuePrivate(value))
 {
+    QJSValuePrivate::setVariant(this, QVariant(value));
 }
 
 /*!
@@ -235,8 +188,8 @@ QJSValue::QJSValue(const QLatin1String &value)
 */
 #ifndef QT_NO_CAST_FROM_ASCII
 QJSValue::QJSValue(const char *value)
-    : d(new QJSValuePrivate(QString::fromUtf8(value)))
 {
+    QJSValuePrivate::setVariant(this, QVariant(QString::fromUtf8(value)));
 }
 #endif
 
@@ -248,9 +201,14 @@ QJSValue::QJSValue(const char *value)
   the new script value (i.e., the object itself is not copied).
 */
 QJSValue::QJSValue(const QJSValue& other)
-    : d(other.d)
+    : d(0)
 {
-    d->ref();
+    QV4::Value *v = QJSValuePrivate::getValue(&other);
+    if (v) {
+        QJSValuePrivate::setValue(this, QJSValuePrivate::engine(&other), v);
+    } else if (QVariant *v = QJSValuePrivate::getVariant(&other)) {
+        QJSValuePrivate::setVariant(this, *v);
+    }
 }
 
 /*!
@@ -258,8 +216,7 @@ QJSValue::QJSValue(const QJSValue& other)
 */
 QJSValue::~QJSValue()
 {
-    if (d)
-        d->deref();
+    QJSValuePrivate::free(this);
 }
 
 /*!
@@ -270,9 +227,11 @@ QJSValue::~QJSValue()
 */
 bool QJSValue::isBool() const
 {
-    if (d->persistent.valueRef())
-        return d->persistent.valueRef()->isBoolean();
-    return d->unboundData.type() == QVariant::Bool;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val)
+        return val->isBoolean();
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    return variant && variant->type() == QVariant::Bool;
 }
 
 /*!
@@ -283,9 +242,27 @@ bool QJSValue::isBool() const
 */
 bool QJSValue::isNumber() const
 {
-    if (d->persistent.valueRef())
-        return d->persistent.valueRef()->isNumber();
-    return d->unboundData.type() == QVariant::Double;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val)
+        return val->isNumber();
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    if (!variant)
+        return false;
+
+    switch (variant->userType()) {
+    case QMetaType::Double:
+    case QMetaType::Int:
+    case QMetaType::UInt:
+    case QMetaType::Long:
+    case QMetaType::ULong:
+    case QMetaType::Short:
+    case QMetaType::UShort:
+    case QMetaType::LongLong:
+    case QMetaType::ULongLong:
+        return true;
+    default:
+        return false;
+    }
 }
 
 /*!
@@ -294,9 +271,11 @@ bool QJSValue::isNumber() const
 */
 bool QJSValue::isNull() const
 {
-    if (d->persistent.valueRef())
-        return d->persistent.valueRef()->isNull();
-    return (int)d->unboundData.type() == QMetaType::VoidStar;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val)
+        return val->isNull();
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    return variant && variant->userType() == QMetaType::VoidStar;
 }
 
 /*!
@@ -307,9 +286,11 @@ bool QJSValue::isNull() const
 */
 bool QJSValue::isString() const
 {
-    if (d->persistent.valueRef())
-        return d->persistent.valueRef()->isString();
-    return (int)d->unboundData.type() == QMetaType::QString;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val)
+        return val->isString();
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    return variant && variant->userType() == QMetaType::QString;
 }
 
 /*!
@@ -318,9 +299,11 @@ bool QJSValue::isString() const
 */
 bool QJSValue::isUndefined() const
 {
-    if (d->persistent.valueRef())
-        return d->persistent.valueRef()->isUndefined();
-    return (int)d->unboundData.type() == QMetaType::UnknownType || (int)d->unboundData.type() == QMetaType::Void;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val)
+        return val->isUndefined();
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    return !variant || variant->userType() == QMetaType::UnknownType || variant->userType() == QMetaType::Void;
 }
 
 /*!
@@ -329,9 +312,10 @@ bool QJSValue::isUndefined() const
 */
 bool QJSValue::isError() const
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return false;
-    Object *o = d->persistent.valueRef()->asObject();
+    Object *o = val->asObject();
     return o && o->asErrorObject();
 }
 
@@ -343,9 +327,10 @@ bool QJSValue::isError() const
 */
 bool QJSValue::isArray() const
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return false;
-    return d->persistent.valueRef()->asArrayObject();
+    return val->asArrayObject();
 }
 
 /*!
@@ -359,9 +344,10 @@ bool QJSValue::isArray() const
 */
 bool QJSValue::isObject() const
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return false;
-    return d->persistent.valueRef()->asObject();
+    return val->asObject();
 }
 
 /*!
@@ -372,9 +358,10 @@ bool QJSValue::isObject() const
 */
 bool QJSValue::isCallable() const
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return false;
-    return d->persistent.valueRef()->asFunctionObject();
+    return val->asFunctionObject();
 }
 
 /*!
@@ -385,9 +372,10 @@ bool QJSValue::isCallable() const
 */
 bool QJSValue::isVariant() const
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return false;
-    return d->persistent.valueRef()->as<QV4::VariantObject>();
+    return val->as<QV4::VariantObject>();
 }
 
 /*!
@@ -405,13 +393,15 @@ bool QJSValue::isVariant() const
 QString QJSValue::toString() const
 {
     QV4::Value scratch;
-    QV4::Value *val = d->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
 
     if (!val) {
-        if (d->unboundData.type() == QVariant::Map)
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        Q_ASSERT(variant);
+        if (variant->type() == QVariant::Map)
             return QStringLiteral("[object Object]");
-        else if (d->unboundData.type() == QVariant::List) {
-            const QVariantList list = d->unboundData.toList();
+        else if (variant->type() == QVariant::List) {
+            const QVariantList list = variant->toList();
             QString result;
             for (int i = 0; i < list.count(); ++i) {
                 if (i > 0)
@@ -420,7 +410,7 @@ QString QJSValue::toString() const
             }
             return result;
         }
-        return d->unboundData.toString();
+        return variant->toString();
     }
     return val->toQStringNoThrow();
 }
@@ -440,19 +430,22 @@ QString QJSValue::toString() const
 double QJSValue::toNumber() const
 {
     QV4::Value scratch;
-    QV4::Value *val = d->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
 
     if (!val) {
-        if (d->unboundData.type() == QVariant::String)
-            return RuntimeHelpers::stringToNumber(d->unboundData.toString());
-        else if (d->unboundData.canConvert<double>())
-            return d->unboundData.value<double>();
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        Q_ASSERT(variant);
+
+        if (variant->type() == QVariant::String)
+            return RuntimeHelpers::stringToNumber(variant->toString());
+        else if (variant->canConvert<double>())
+            return variant->value<double>();
         else
             return std::numeric_limits<double>::quiet_NaN();
     }
 
     double dbl = val->toNumber();
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (engine && engine->hasException) {
         engine->catchException();
         return 0;
@@ -475,17 +468,18 @@ double QJSValue::toNumber() const
 bool QJSValue::toBool() const
 {
     QV4::Value scratch;
-    QV4::Value *val = d->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
 
     if (!val) {
-        if (d->unboundData.userType() == QMetaType::QString)
-            return d->unboundData.toString().length() > 0;
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        if (variant->userType() == QMetaType::QString)
+            return variant->toString().length() > 0;
         else
-            return d->unboundData.toBool();
+            return variant->toBool();
     }
 
     bool b = val->toBoolean();
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (engine && engine->hasException) {
         engine->catchException();
         return false;
@@ -508,17 +502,18 @@ bool QJSValue::toBool() const
 qint32 QJSValue::toInt() const
 {
     QV4::Value scratch;
-    QV4::Value *val = d->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
 
     if (!val) {
-        if (d->unboundData.userType() == QMetaType::QString)
-            return QV4::Primitive::toInt32(RuntimeHelpers::stringToNumber(d->unboundData.toString()));
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        if (variant->userType() == QMetaType::QString)
+            return QV4::Primitive::toInt32(RuntimeHelpers::stringToNumber(variant->toString()));
         else
-            return d->unboundData.toInt();
+            return variant->toInt();
     }
 
     qint32 i = val->toInt32();
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (engine && engine->hasException) {
         engine->catchException();
         return 0;
@@ -541,17 +536,18 @@ qint32 QJSValue::toInt() const
 quint32 QJSValue::toUInt() const
 {
     QV4::Value scratch;
-    QV4::Value *val = d->valueForData(&scratch);
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
 
     if (!val) {
-        if (d->unboundData.userType() == QMetaType::QString)
-            return QV4::Primitive::toUInt32(RuntimeHelpers::stringToNumber(d->unboundData.toString()));
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        if (variant->userType() == QMetaType::QString)
+            return QV4::Primitive::toUInt32(RuntimeHelpers::stringToNumber(variant->toString()));
         else
-            return d->unboundData.toUInt();
+            return variant->toUInt();
     }
 
     quint32 u = val->toUInt32();
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (engine && engine->hasException) {
         engine->catchException();
         return 0;
@@ -583,24 +579,29 @@ quint32 QJSValue::toUInt() const
 */
 QVariant QJSValue::toVariant() const
 {
-    if (d->persistent.isEmpty())
-        return d->unboundData;
-
-    if (Object *o = d->persistent.valueRef()->asObject())
-        return o->engine()->toVariant(*d->persistent.valueRef(), /*typeHint*/ -1, /*createJSValueForObjects*/ false);
-
-    if (d->persistent.valueRef()->isString())
-        return QVariant(d->persistent.valueRef()->stringValue()->toQString());
-    if (d->persistent.valueRef()->isBoolean())
-        return QVariant(d->persistent.valueRef()->booleanValue());
-    if (d->persistent.valueRef()->isNumber()) {
-        if (d->persistent.valueRef()->isInt32())
-            return QVariant(d->persistent.valueRef()->integerValue());
-        return QVariant(d->persistent.valueRef()->asDouble());
+    QVariant *variant = QJSValuePrivate::getVariant(this);
+    if (variant)
+        return *variant;
+
+    QV4::Value scratch;
+    QV4::Value *val = QJSValuePrivate::valueForData(this, &scratch);
+    Q_ASSERT(val);
+
+    if (Object *o = val->asObject())
+        return o->engine()->toVariant(*val, /*typeHint*/ -1, /*createJSValueForObjects*/ false);
+
+    if (val->isString())
+        return QVariant(val->stringValue()->toQString());
+    if (val->isBoolean())
+        return QVariant(val->booleanValue());
+    if (val->isNumber()) {
+        if (val->isInt32())
+            return QVariant(val->integerValue());
+        return QVariant(val->asDouble());
     }
-    if (d->persistent.valueRef()->isNull())
+    if (val->isNull())
         return QVariant(QMetaType::VoidStar, 0);
-    Q_ASSERT(d->persistent.valueRef()->isUndefined());
+    Q_ASSERT(val->isUndefined());
     return QVariant();
 }
 
@@ -621,25 +622,26 @@ QVariant QJSValue::toVariant() const
 */
 QJSValue QJSValue::call(const QJSValueList &args)
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return QJSValue();
 
-    FunctionObject *f = d->persistent.valueRef()->asFunctionObject();
+    FunctionObject *f = val->asFunctionObject();
     if (!f)
         return QJSValue();
 
-    ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     Q_ASSERT(engine);
 
     Scope scope(engine);
     ScopedCallData callData(scope, args.length());
     callData->thisObject = engine->globalObject()->asReturnedValue();
     for (int i = 0; i < args.size(); ++i) {
-        if (!args.at(i).d->checkEngine(engine)) {
+        if (!QJSValuePrivate::checkEngine(engine, args.at(i))) {
             qWarning("QJSValue::call() failed: cannot call function with argument created in a different engine");
             return QJSValue();
         }
-        callData->args[i] = args.at(i).d->getValue(engine);
+        callData->args[i] = QJSValuePrivate::convertedToValue(engine, args.at(i));
     }
 
     ScopedValue result(scope, f->call(callData));
@@ -671,30 +673,31 @@ QJSValue QJSValue::call(const QJSValueList &args)
 */
 QJSValue QJSValue::callWithInstance(const QJSValue &instance, const QJSValueList &args)
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return QJSValue();
 
-    FunctionObject *f = d->persistent.valueRef()->asFunctionObject();
+    FunctionObject *f = val->asFunctionObject();
     if (!f)
         return QJSValue();
 
-    ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     Q_ASSERT(engine);
     Scope scope(engine);
 
-    if (!instance.d->checkEngine(engine)) {
+    if (!QJSValuePrivate::checkEngine(engine, instance)) {
         qWarning("QJSValue::call() failed: cannot call function with thisObject created in a different engine");
         return QJSValue();
     }
 
     ScopedCallData callData(scope, args.size());
-    callData->thisObject = instance.d->getValue(engine);
+    callData->thisObject = QJSValuePrivate::convertedToValue(engine, instance);
     for (int i = 0; i < args.size(); ++i) {
-        if (!args.at(i).d->checkEngine(engine)) {
+        if (!QJSValuePrivate::checkEngine(engine, args.at(i))) {
             qWarning("QJSValue::call() failed: cannot call function with argument created in a different engine");
             return QJSValue();
         }
-        callData->args[i] = args.at(i).d->getValue(engine);
+        callData->args[i] = QJSValuePrivate::convertedToValue(engine, args.at(i));
     }
 
     ScopedValue result(scope, f->call(callData));
@@ -724,24 +727,25 @@ QJSValue QJSValue::callWithInstance(const QJSValue &instance, const QJSValueList
 */
 QJSValue QJSValue::callAsConstructor(const QJSValueList &args)
 {
-    if (d->persistent.isEmpty())
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (!val)
         return QJSValue();
 
-    FunctionObject *f = d->persistent.valueRef()->asFunctionObject();
+    FunctionObject *f = val->asFunctionObject();
     if (!f)
         return QJSValue();
 
-    ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     Q_ASSERT(engine);
 
     Scope scope(engine);
     ScopedCallData callData(scope, args.size());
     for (int i = 0; i < args.size(); ++i) {
-        if (!args.at(i).d->checkEngine(engine)) {
+        if (!QJSValuePrivate::checkEngine(engine, args.at(i))) {
             qWarning("QJSValue::callAsConstructor() failed: cannot construct function with argument created in a different engine");
             return QJSValue();
         }
-        callData->args[i] = args.at(i).d->getValue(engine);
+        callData->args[i] = QJSValuePrivate::convertedToValue(engine, args.at(i));
     }
 
     ScopedValue result(scope, f->construct(callData));
@@ -762,7 +766,7 @@ QJSValue QJSValue::callAsConstructor(const QJSValueList &args)
 */
 QJSEngine* QJSValue::engine() const
 {
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (engine)
         return engine->jsEngine();
     return 0;
@@ -779,11 +783,11 @@ QJSEngine* QJSValue::engine() const
 */
 QJSValue QJSValue::prototype() const
 {
-    QV4::ExecutionEngine *engine = d->persistent.engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return QJSValue();
     QV4::Scope scope(engine);
-    ScopedObject o(scope, d->persistent.valueRef()->asObject());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this)->asObject());
     if (!o)
         return QJSValue();
     ScopedObject p(scope, o->prototype());
@@ -806,20 +810,23 @@ QJSValue QJSValue::prototype() const
 */
 void QJSValue::setPrototype(const QJSValue& prototype)
 {
-    ExecutionEngine *v4 = d->persistent.engine();
-    if (!v4)
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
+    if (!engine)
         return;
-    Scope scope(v4);
-    ScopedObject o(scope, d->persistent.value());
+    Scope scope(engine);
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return;
-    prototype.d->getValue(v4);
-    if (prototype.d->persistent.valueRef()->isNull()) {
+    QV4::Value scratch;
+    QV4::Value *val = QJSValuePrivate::valueForData(&prototype, &scratch);
+    if (!val)
+        return;
+    if (val->isNull()) {
         o->setPrototype(0);
         return;
     }
 
-    ScopedObject p(scope, prototype.d->persistent.value());
+    ScopedObject p(scope, val);
     if (!p)
         return;
     if (o->engine() != p->engine()) {
@@ -839,10 +846,17 @@ void QJSValue::setPrototype(const QJSValue& prototype)
 */
 QJSValue& QJSValue::operator=(const QJSValue& other)
 {
-    if (d != other.d) {
-        d->deref();
-        d = other.d;
-        d->ref();
+    if (d == other.d)
+        return *this;
+
+    QJSValuePrivate::free(this);
+    d = 0;
+
+    QV4::Value *v = QJSValuePrivate::getValue(&other);
+    if (v) {
+        QJSValuePrivate::setValue(this, QJSValuePrivate::engine(&other), v);
+    } else if (QVariant *v = QJSValuePrivate::getVariant(&other)) {
+        QJSValuePrivate::setVariant(this, *v);
     }
     return *this;
 }
@@ -890,15 +904,17 @@ static bool js_equal(const QString &string, QV4::ValueRef value)
 bool QJSValue::equals(const QJSValue& other) const
 {
     QV4::Value s1, s2;
-    QV4::Value *v = d->valueForData(&s1);
-    QV4::Value *ov = other.d->valueForData(&s2);
+    QV4::Value *v = QJSValuePrivate::valueForData(this, &s1);
+    QV4::Value *ov = QJSValuePrivate::valueForData(&other, &s2);
 
     if (!v) {
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        Q_ASSERT(variant);
         if (!ov)
-            return d->unboundData == other.d->unboundData;
-        if (d->unboundData.type() == QVariant::Map || d->unboundData.type() == QVariant::List)
+            return *variant == *QJSValuePrivate::getVariant(&other);
+        if (variant->type() == QVariant::Map || variant->type() == QVariant::List)
             return false;
-        return js_equal(d->unboundData.toString(), *ov);
+        return js_equal(variant->toString(), *ov);
         }
     if (!ov)
         return other.equals(*this);
@@ -931,16 +947,18 @@ bool QJSValue::equals(const QJSValue& other) const
 bool QJSValue::strictlyEquals(const QJSValue& other) const
 {
     QV4::Value s1, s2;
-    QV4::Value *v = d->valueForData(&s1);
-    QV4::Value *ov = other.d->valueForData(&s2);
+    QV4::Value *v = QJSValuePrivate::valueForData(this, &s1);
+    QV4::Value *ov = QJSValuePrivate::valueForData(&other, &s2);
 
     if (!v) {
+        QVariant *variant = QJSValuePrivate::getVariant(this);
+        Q_ASSERT(variant);
         if (!ov)
-            return d->unboundData == other.d->unboundData;
-        if (d->unboundData.type() == QVariant::Map || d->unboundData.type() == QVariant::List)
+            return *variant == *QJSValuePrivate::getVariant(&other);
+        if (variant->type() == QVariant::Map || variant->type() == QVariant::List)
             return false;
         if (ov->isString())
-            return d->unboundData.toString() == ov->stringValue()->toQString();
+            return variant->toString() == ov->stringValue()->toQString();
         return false;
     }
     if (!ov)
@@ -964,12 +982,12 @@ bool QJSValue::strictlyEquals(const QJSValue& other) const
 */
 QJSValue QJSValue::property(const QString& name) const
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return QJSValue();
 
     QV4::Scope scope(engine);
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return QJSValue();
 
@@ -1000,12 +1018,12 @@ QJSValue QJSValue::property(const QString& name) const
 */
 QJSValue QJSValue::property(quint32 arrayIndex) const
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return QJSValue();
 
     QV4::Scope scope(engine);
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return QJSValue();
 
@@ -1028,16 +1046,16 @@ QJSValue QJSValue::property(quint32 arrayIndex) const
 */
 void QJSValue::setProperty(const QString& name, const QJSValue& value)
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return;
     Scope scope(engine);
 
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return;
 
-    if (!value.d->checkEngine(o->engine())) {
+    if (!QJSValuePrivate::checkEngine(engine, value)) {
         qWarning("QJSValue::setProperty(%s) failed: cannot set value created in a different engine", name.toUtf8().constData());
         return;
     }
@@ -1050,7 +1068,7 @@ void QJSValue::setProperty(const QString& name, const QJSValue& value)
     }
 
     s->makeIdentifier(scope.engine);
-    QV4::ScopedValue v(scope, value.d->getValue(engine));
+    QV4::ScopedValue v(scope, QJSValuePrivate::convertedToValue(engine, value));
     o->put(s, v);
     if (engine->hasException)
         engine->catchException();
@@ -1070,16 +1088,21 @@ void QJSValue::setProperty(const QString& name, const QJSValue& value)
 */
 void QJSValue::setProperty(quint32 arrayIndex, const QJSValue& value)
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return;
     Scope scope(engine);
 
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return;
 
-    QV4::ScopedValue v(scope, value.d->getValue(engine));
+    if (!QJSValuePrivate::checkEngine(engine, value)) {
+        qWarning("QJSValue::setProperty(%d) failed: cannot set value created in a different engine", arrayIndex);
+        return;
+    }
+
+    QV4::ScopedValue v(scope, QJSValuePrivate::convertedToValue(engine, value));
     if (arrayIndex != UINT_MAX)
         o->putIndexed(arrayIndex, v);
     else
@@ -1110,9 +1133,9 @@ void QJSValue::setProperty(quint32 arrayIndex, const QJSValue& value)
 */
 bool QJSValue::deleteProperty(const QString &name)
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     Scope scope(engine);
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return false;
 
@@ -1131,12 +1154,12 @@ bool QJSValue::deleteProperty(const QString &name)
 */
 bool QJSValue::hasProperty(const QString &name) const
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return false;
 
     Scope scope(engine);
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return false;
 
@@ -1152,12 +1175,12 @@ bool QJSValue::hasProperty(const QString &name) const
 */
 bool QJSValue::hasOwnProperty(const QString &name) const
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return false;
 
     Scope scope(engine);
-    ScopedObject o(scope, d->persistent.value());
+    ScopedObject o(scope, QJSValuePrivate::getValue(this));
     if (!o)
         return false;
 
@@ -1177,11 +1200,11 @@ bool QJSValue::hasOwnProperty(const QString &name) const
  */
 QObject *QJSValue::toQObject() const
 {
-    ExecutionEngine *engine = d->engine();
+    QV4::ExecutionEngine *engine = QJSValuePrivate::engine(this);
     if (!engine)
         return 0;
     QV4::Scope scope(engine);
-    QV4::Scoped<QV4::QObjectWrapper> wrapper(scope, d->persistent.value());
+    QV4::Scoped<QV4::QObjectWrapper> wrapper(scope, QJSValuePrivate::getValue(this));
     if (!wrapper)
         return 0;
 
@@ -1197,8 +1220,9 @@ QObject *QJSValue::toQObject() const
 */
 QDateTime QJSValue::toDateTime() const
 {
-    if (!d->persistent.isEmpty()) {
-        QV4::DateObject *date = d->persistent.valueRef()->asDateObject();
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    if (val) {
+        QV4::DateObject *date = val->asDateObject();
         if (date)
             return date->toQDateTime();
     }
@@ -1211,7 +1235,8 @@ QDateTime QJSValue::toDateTime() const
 */
 bool QJSValue::isDate() const
 {
-    return !d->persistent.isEmpty() && d->persistent.valueRef()->asDateObject();
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    return val && val->asDateObject();
 }
 
 /*!
@@ -1220,7 +1245,8 @@ bool QJSValue::isDate() const
 */
 bool QJSValue::isRegExp() const
 {
-    return !d->persistent.isEmpty() && d->persistent.valueRef()->as<RegExpObject>();
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    return val && val->as<RegExpObject>();
 }
 
 /*!
@@ -1234,7 +1260,8 @@ bool QJSValue::isRegExp() const
 */
 bool QJSValue::isQObject() const
 {
-    return !d->persistent.isEmpty() && d->persistent.valueRef()->as<QV4::QObjectWrapper>() != 0;
+    QV4::Value *val = QJSValuePrivate::getValue(this);
+    return val && val->as<QV4::QObjectWrapper>() != 0;
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsapi/qjsvalue.h b/src/qml/jsapi/qjsvalue.h
index 4ff86b1edc..19736803c1 100644
--- a/src/qml/jsapi/qjsvalue.h
+++ b/src/qml/jsapi/qjsvalue.h
@@ -49,7 +49,6 @@ struct QMetaObject;
 class QDateTime;
 
 typedef QList<QJSValue> QJSValueList;
-class QJSValuePrivate;
 namespace QV4 {
     struct ExecutionEngine;
     struct Value;
@@ -140,7 +139,7 @@ private:
     // force compile error, prevent QJSValue(bool) to be called
     QJSValue(void *) Q_DECL_EQ_DELETE;
 
-    QJSValuePrivate *d;
+    mutable quintptr d;
 };
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsapi/qjsvalue_p.h b/src/qml/jsapi/qjsvalue_p.h
index 3d7afdbd75..83dbe82f76 100644
--- a/src/qml/jsapi/qjsvalue_p.h
+++ b/src/qml/jsapi/qjsvalue_p.h
@@ -57,64 +57,117 @@
 
 QT_BEGIN_NAMESPACE
 
-/*!
-  \internal
-  \class QJSValuePrivate
-*/
-class Q_QML_PRIVATE_EXPORT QJSValuePrivate
+class QJSValuePrivate
 {
 public:
-    QJSValuePrivate()
-        : refcount(1)
-    {}
-    QJSValuePrivate(QV4::ExecutionEngine *e, const QV4::ValueRef v)
-        : refcount(1),
-          persistent(e, v)
+    static inline QV4::Value *getValue(const QJSValue *jsval)
     {
-        Q_ASSERT(!v->isEmpty());
+        if (jsval->d & 3)
+            return 0;
+        return reinterpret_cast<QV4::Value *>(jsval->d);
     }
-    QJSValuePrivate(QV4::ExecutionEngine *e, QV4::ReturnedValue v)
-        : refcount(1),
-          persistent(e, v)
+
+    static inline QVariant *getVariant(const QJSValue *jsval)
     {
+        if (jsval->d & 1)
+            return reinterpret_cast<QVariant *>(jsval->d & ~3);
+        return 0;
     }
-    explicit QJSValuePrivate(const QVariant &v)
-        : refcount(1),
-          unboundData(v)
-    {
+
+    static inline void setVariant(QJSValue *jsval, const QVariant &v) {
+        QVariant *val = new QVariant(v);
+        jsval->d = reinterpret_cast<quintptr>(val) | 1;
     }
 
-    bool checkEngine(QV4::ExecutionEngine *e) {
-        if (persistent.isEmpty())
-            getValue(e);
-        return persistent.engine() == e;
+    static inline void setValue(QJSValue *jsval, QV4::ExecutionEngine *engine, QV4::ValueRef v) {
+        QV4::Value *value = engine->memoryManager->m_persistentValues->allocate();
+        *value = v;
+        jsval->d = reinterpret_cast<quintptr>(value);
     }
 
-    QV4::ReturnedValue getValue(QV4::ExecutionEngine *e);
+    static inline void setValue(QJSValue *jsval, QV4::ExecutionEngine *engine, QV4::ReturnedValue v) {
+        QV4::Value *value = engine->memoryManager->m_persistentValues->allocate();
+        *value = v;
+        jsval->d = reinterpret_cast<quintptr>(value);
+    }
 
-    static QJSValuePrivate *get(const QJSValue &v) { return v.d; }
-    QV4::ExecutionEngine *engine() const { return persistent.engine(); }
+    static QV4::ReturnedValue convertedToValue(QV4::ExecutionEngine *e, const QJSValue &jsval)
+    {
+        QV4::Value *v = getValue(&jsval);
+        if (!v) {
+            QVariant *variant = getVariant(&jsval);
+            v = e->memoryManager->m_persistentValues->allocate();
+            *v = variant ? e->fromVariant(*variant) : QV4::Encode::undefined();
+            jsval.d = reinterpret_cast<quintptr>(v);
+            delete variant;
+        }
+
+        if (QV4::PersistentValueStorage::getEngine(v) != e) {
+            qWarning("JSValue can't be reassigned to another engine.");
+            return QV4::Encode::undefined();
+        }
 
-    void ref() { ++refcount; }
-    void deref() {
-        if (!--refcount)
-            delete this;
+        return v->asReturnedValue();
     }
 
-    QV4::Value *valueForData(QV4::Value *scratch) const {
-        QV4::Value *v = persistent.valueRef();
+    static QV4::Value *valueForData(const QJSValue *jsval, QV4::Value *scratch)
+    {
+        QV4::Value *v = getValue(jsval);
         if (v)
             return v;
-        *scratch = primitiveValueForUnboundData();
-        return (scratch->isEmpty() ? 0 : scratch);
+        v = scratch;
+        QVariant *variant = getVariant(jsval);
+        if (!variant) {
+            *v = QV4::Encode::undefined();
+            return v;
+        }
+
+        switch (variant->userType()) {
+        case QMetaType::UnknownType:
+        case QMetaType::Void:
+            *v = QV4::Encode::undefined();
+            break;
+        case QMetaType::VoidStar:
+            *v = QV4::Encode::null();
+            break;
+        case QMetaType::Bool:
+            *v = QV4::Encode(variant->toBool());
+            break;
+        case QMetaType::Double:
+            *v = QV4::Encode(variant->toDouble());
+            break;
+        case QMetaType::Int:
+        case QMetaType::Short:
+        case QMetaType::UShort:
+        case QMetaType::Char:
+        case QMetaType::UChar:
+            *v = QV4::Encode(variant->toInt());
+            break;
+        case QMetaType::UInt:
+            *v = QV4::Encode(variant->toUInt());
+            break;
+        default:
+            return 0;
+        }
+        return v;
+    }
+
+    static QV4::ExecutionEngine *engine(const QJSValue *jsval) {
+        QV4::Value *v = getValue(jsval);
+        return v ? QV4::PersistentValueStorage::getEngine(v) : 0;
     }
-    QV4::Value primitiveValueForUnboundData() const;
 
-    int refcount;
-    QV4::PersistentValue persistent;
-    QVariant unboundData;
-private:
-    QJSValuePrivate(QV4::ReturnedValue v) Q_DECL_EQ_DELETE;
+    static inline bool checkEngine(QV4::ExecutionEngine *e, const QJSValue &jsval) {
+        QV4::ExecutionEngine *v4 = engine(&jsval);
+        return !v4 || v4 == e;
+    }
+
+    static inline void free(QJSValue *jsval) {
+        if (QV4::Value *v = QJSValuePrivate::getValue(jsval))
+            QV4::PersistentValueStorage::free(v);
+        else if (QVariant *v = QJSValuePrivate::getVariant(jsval))
+            delete v;
+    }
 };
 
 QT_END_NAMESPACE
diff --git a/src/qml/jsapi/qjsvalueiterator.cpp b/src/qml/jsapi/qjsvalueiterator.cpp
index 2b27f655c8..6f78f71f48 100644
--- a/src/qml/jsapi/qjsvalueiterator.cpp
+++ b/src/qml/jsapi/qjsvalueiterator.cpp
@@ -45,13 +45,12 @@ QJSValueIteratorPrivate::QJSValueIteratorPrivate(const QJSValue &v)
     , currentIndex(UINT_MAX)
     , nextIndex(UINT_MAX)
 {
-    QJSValuePrivate *jsp = QJSValuePrivate::get(value);
-    QV4::ExecutionEngine *e = jsp->persistent.engine();
+    QV4::ExecutionEngine *e = QJSValuePrivate::engine(&v);
     if (!e)
         return;
 
     QV4::Scope scope(e);
-    QV4::ScopedObject o(scope, jsp->persistent.value());
+    QV4::ScopedObject o(scope, QJSValuePrivate::getValue(&v));
     iterator.set(e, e->newForEachIteratorObject(o));
 
     currentName = (QV4::String *)0;
@@ -123,7 +122,7 @@ QJSValueIterator::~QJSValueIterator()
 */
 bool QJSValueIterator::hasNext() const
 {
-    QV4::Value *val = QJSValuePrivate::get(d_ptr->value)->persistent.valueRef();
+    QV4::Value *val = QJSValuePrivate::getValue(&d_ptr->value);
     if (!val || !val->isObject())
         return false;
     return !!d_ptr->nextName || d_ptr->nextIndex != UINT_MAX;
@@ -139,7 +138,7 @@ bool QJSValueIterator::hasNext() const
 */
 bool QJSValueIterator::next()
 {
-    QV4::Value *val = QJSValuePrivate::get(d_ptr->value)->persistent.valueRef();
+    QV4::Value *val = QJSValuePrivate::getValue(&d_ptr->value);
     if (!val || !val->isObject())
         return false;
     d_ptr->currentName = d_ptr->nextName;
@@ -166,7 +165,7 @@ bool QJSValueIterator::next()
 */
 QString QJSValueIterator::name() const
 {
-    QV4::Value *val = QJSValuePrivate::get(d_ptr->value)->persistent.valueRef();
+    QV4::Value *val = QJSValuePrivate::getValue(&d_ptr->value);
     if (!val || !val->isObject())
         return QString();
     if (!!d_ptr->currentName)
@@ -189,7 +188,7 @@ QJSValue QJSValueIterator::value() const
     if (!engine)
         return QJSValue();
     QV4::Scope scope(engine);
-    QV4::ScopedObject obj(scope, QJSValuePrivate::get(d_ptr->value)->persistent.value());
+    QV4::ScopedObject obj(scope, QJSValuePrivate::getValue(&d_ptr->value));
     if (!obj)
         return QJSValue();
 
@@ -223,9 +222,8 @@ QJSValueIterator& QJSValueIterator::operator=(QJSValue& object)
         return *this;
     }
 
-    QJSValuePrivate *jsp = QJSValuePrivate::get(object);
     QV4::Scope scope(v4);
-    QV4::ScopedObject o(scope, jsp->persistent.value());
+    QV4::ScopedObject o(scope, QJSValuePrivate::getValue(&object));
     d_ptr->iterator.set(v4, v4->newForEachIteratorObject(o));
     QV4::Scoped<QV4::ForEachIteratorObject> it(scope, d_ptr->iterator.value());
     it->d()->it.flags =  QV4::ObjectIterator::NoFlags;
diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index 359b24d5ab..366e5c7603 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -1433,8 +1433,7 @@ QV4::ReturnedValue QV4::ExecutionEngine::fromVariant(const QVariant &variant)
             }
         } else if (type == qMetaTypeId<QJSValue>()) {
             const QJSValue *value = reinterpret_cast<const QJSValue *>(ptr);
-            QJSValuePrivate *valuep = QJSValuePrivate::get(*value);
-            return valuep->getValue(this);
+            return QJSValuePrivate::convertedToValue(this, *value);
         } else if (type == qMetaTypeId<QList<QObject *> >()) {
             // XXX Can this be made more by using Array as a prototype and implementing
             // directly against QList<QObject*>?
@@ -1586,7 +1585,7 @@ QV4::ReturnedValue ExecutionEngine::metaTypeToJS(int type, const void *data)
         return QV4::JsonObject::fromJsonArray(this, *reinterpret_cast<const QJsonArray *>(data));
     default:
         if (type == qMetaTypeId<QJSValue>()) {
-            return QJSValuePrivate::get(*reinterpret_cast<const QJSValue*>(data))->getValue(this);
+            return QJSValuePrivate::convertedToValue(this, *reinterpret_cast<const QJSValue*>(data));
         } else {
             QByteArray typeName = QMetaType::typeName(type);
             if (typeName.endsWith('*') && !*reinterpret_cast<void* const *>(data)) {
diff --git a/src/qml/jsruntime/qv4qobjectwrapper.cpp b/src/qml/jsruntime/qv4qobjectwrapper.cpp
index 3bacba117e..9fb7ad96fa 100644
--- a/src/qml/jsruntime/qv4qobjectwrapper.cpp
+++ b/src/qml/jsruntime/qv4qobjectwrapper.cpp
@@ -194,7 +194,7 @@ static QV4::ReturnedValue LoadProperty(QV4::ExecutionEngine *v4, QObject *object
     } else if (property.propType == qMetaTypeId<QJSValue>()) {
         QJSValue v;
         ReadFunction(object, property, &v, notifier);
-        return QJSValuePrivate::get(v)->getValue(v4);
+        return QJSValuePrivate::convertedToValue(v4, v);
     } else if (property.isQVariant()) {
         QVariant v;
         ReadFunction(object, property, &v, notifier);
@@ -1680,7 +1680,7 @@ QV4::ReturnedValue CallArgument::toValue(QV4::ExecutionEngine *engine)
     QV4::Scope scope(engine);
 
     if (type == qMetaTypeId<QJSValue>()) {
-        return QJSValuePrivate::get(*qjsValuePtr)->getValue(scope.engine);
+        return QJSValuePrivate::convertedToValue(scope.engine, *qjsValuePtr);
     } else if (type == QMetaType::Int) {
         return QV4::Encode(int(intValue));
     } else if (type == QMetaType::UInt) {
diff --git a/src/qml/qml/qqmlcontextwrapper.cpp b/src/qml/qml/qqmlcontextwrapper.cpp
index 0c16ae18db..29f5152f77 100644
--- a/src/qml/qml/qqmlcontextwrapper.cpp
+++ b/src/qml/qml/qqmlcontextwrapper.cpp
@@ -416,7 +416,7 @@ ReturnedValue QmlContextWrapper::qmlSingletonWrapper(ExecutionEngine *v4, String
 
     if (QObject *qobjectSingleton = siinfo->qobjectApi(e))
         return QV4::QObjectWrapper::wrap(engine(), qobjectSingleton);
-    return QJSValuePrivate::get(siinfo->scriptApi(e))->getValue(engine());
+    return QJSValuePrivate::convertedToValue(engine(), siinfo->scriptApi(e));
 }
 
 DEFINE_OBJECT_VTABLE(QQmlIdObjectsArray);
diff --git a/src/qml/qml/qqmltypewrapper.cpp b/src/qml/qml/qqmltypewrapper.cpp
index 77d472e0c7..2c0972bced 100644
--- a/src/qml/qml/qqmltypewrapper.cpp
+++ b/src/qml/qml/qqmltypewrapper.cpp
@@ -168,7 +168,7 @@ ReturnedValue QmlTypeWrapper::get(Managed *m, String *name, bool *hasProperty)
                 return QV4::QObjectWrapper::getQmlProperty(v4, context, qobjectSingleton, name, QV4::QObjectWrapper::IgnoreRevision, hasProperty);
             } else if (!siinfo->scriptApi(e).isUndefined()) {
                 // NOTE: if used in a binding, changes will not trigger re-evaluation since non-NOTIFYable.
-                QV4::ScopedObject o(scope, QJSValuePrivate::get(siinfo->scriptApi(e))->getValue(v4));
+                QV4::ScopedObject o(scope, QJSValuePrivate::convertedToValue(v4, siinfo->scriptApi(e)));
                 if (!!o)
                     return o->get(name);
             }
@@ -254,7 +254,7 @@ void QmlTypeWrapper::put(Managed *m, String *name, const ValueRef value)
         if (qobjectSingleton) {
             QV4::QObjectWrapper::setQmlProperty(v4, context, qobjectSingleton, name, QV4::QObjectWrapper::IgnoreRevision, value);
         } else if (!siinfo->scriptApi(e).isUndefined()) {
-            QV4::ScopedObject apiprivate(scope, QJSValuePrivate::get(siinfo->scriptApi(e))->getValue(v4));
+            QV4::ScopedObject apiprivate(scope, QJSValuePrivate::convertedToValue(v4, siinfo->scriptApi(e)));
             if (!apiprivate) {
                 QString error = QLatin1String("Cannot assign to read-only property \"") + name->toQString() + QLatin1Char('\"');
                 v4->throwError(error);
diff --git a/src/qml/qml/v8/qv8engine.cpp b/src/qml/qml/v8/qv8engine.cpp
index ce5d3c8370..73113be9ba 100644
--- a/src/qml/qml/v8/qv8engine.cpp
+++ b/src/qml/qml/v8/qv8engine.cpp
@@ -102,20 +102,18 @@ static void saveJSValue(QDataStream &stream, const void *data)
 static void restoreJSValue(QDataStream &stream, void *data)
 {
     QJSValue *jsv = reinterpret_cast<QJSValue*>(data);
-    QJSValuePrivate *d = QJSValuePrivate::get(*jsv);
 
     quint32 isNullOrUndefined;
     stream >> isNullOrUndefined;
 
-    // ### Optimize for the common case where we have an valid persistent
-    d->persistent.clear();
-
     if (isNullOrUndefined & 0x1) {
-        d->unboundData = QVariant(QMetaType::VoidStar, (void *)0);
+        *jsv = QJSValue(QJSValue::NullValue);
     } else if (isNullOrUndefined & 0x2) {
-        d->unboundData = QVariant();
+        *jsv = QJSValue();
     } else {
-        d->unboundData.load(stream);
+        QVariant v;
+        v.load(stream);
+        QJSValuePrivate::setVariant(jsv, v);
     }
 }