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>

1 files changed, 5 insertions, 7 deletions

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);
     }
 }