Simplify the code required for switching the current sender

Squeezes another percent of performance out of
QMetaObject::activate().

Change-Id: I620b8c578681280efcc9bec50cfb1020d2afc928
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/kernel/qobject.cpp

@@ -166,39 +166,6 @@ extern "C" Q_CORE_EXPORT void qt_removeObject(QObject *)
 {}
 #endif
 
-struct QConnectionSenderSwitcher {
-    QObject *receiver;
-    QObjectPrivate::Sender *previousSender;
-    QObjectPrivate::Sender currentSender;
-    bool switched;
-
-    inline QConnectionSenderSwitcher() : switched(false) {}
-
-    inline QConnectionSenderSwitcher(QObject *receiver, QObject *sender, int signal_absolute_id)
-    {
-        switchSender(receiver, sender, signal_absolute_id);
-    }
-
-    inline void switchSender(QObject *receiver, QObject *sender, int signal_absolute_id)
-    {
-        this->receiver = receiver;
-        currentSender.sender = sender;
-        currentSender.signal = signal_absolute_id;
-        currentSender.ref = 1;
-        previousSender = QObjectPrivate::setCurrentSender(receiver, &currentSender);
-        switched = true;
-    }
-
-    inline ~QConnectionSenderSwitcher()
-    {
-        if (switched)
-            QObjectPrivate::resetCurrentSender(receiver, &currentSender, previousSender);
-    }
-private:
-    Q_DISABLE_COPY(QConnectionSenderSwitcher)
-};
-
-
 void (*QAbstractDeclarativeData::destroyed)(QAbstractDeclarativeData *, QObject *) = 0;
 void (*QAbstractDeclarativeData::destroyed_qml1)(QAbstractDeclarativeData *, QObject *) = 0;
 void (*QAbstractDeclarativeData::parentChanged)(QAbstractDeclarativeData *, QObject *, QObject *) = 0;
@@ -938,10 +905,10 @@ QObject::~QObject()
         }
     }
 
-    // set ref to zero to indicate that this object has been deleted
+    if (d->currentSender) {
-    if (d->currentSender != 0)
+        d->currentSender->receiverDeleted();
-        d->currentSender->ref = 0;
+        d->currentSender = nullptr;
-    d->currentSender = 0;
+    }
 
     if (d->connectionLists || d->senders) {
         QMutex *signalSlotMutex = signalSlotLock(this);
@@ -1272,7 +1239,7 @@ bool QObject::event(QEvent *e)
         {
             QMetaCallEvent *mce = static_cast<QMetaCallEvent*>(e);
 
-            QConnectionSenderSwitcher sw(this, const_cast<QObject*>(mce->sender()), mce->signalId());
+            QObjectPrivate::Sender sender(this, const_cast<QObject*>(mce->sender()), mce->signalId());
 
             mce->placeMetaCall(this);
             break;
@@ -1576,9 +1543,10 @@ void QObjectPrivate::setThreadData_helper(QThreadData *currentData, QThreadData
     }
 
     // the current emitting thread shouldn't restore currentSender after calling moveToThread()
-    if (currentSender)
+    if (currentSender) {
-        currentSender->ref = 0;
+        currentSender->receiverDeleted();
-    currentSender = 0;
+        currentSender = nullptr;
+    }
 
     // set new thread data
     targetData->ref();
@@ -3755,11 +3723,8 @@ void doActivate(QObject *sender, int signal_index, void **argv)
 #endif
             }
 
-            QConnectionSenderSwitcher sw;
+            QObjectPrivate::Sender senderData(receiverInSameThread ? receiver : nullptr, sender, signal_index);
 
-            if (receiverInSameThread) {
-                sw.switchSender(receiver, sender, signal_index);
-            }
             if (c->isSlotObject) {
                 c->slotObj->ref();
                 QScopedPointer<QtPrivate::QSlotObjectBase, QSlotObjectBaseDeleter> obj(c->slotObj);

src/corelib/kernel/qobject_p.h

@@ -167,9 +167,31 @@ public:
 
     struct Sender
     {
+        Sender(QObject *receiver, QObject *sender, int signal)
+            : receiver(receiver), sender(sender), signal(signal)
+        {
+            if (receiver) {
+                previous = receiver->d_func()->currentSender;
+                receiver->d_func()->currentSender = this;
+            }
+        }
+        ~Sender()
+        {
+            if (receiver)
+                receiver->d_func()->currentSender = previous;
+        }
+        void receiverDeleted()
+        {
+            Sender *s = this;
+            while (s) {
+                s->receiver = nullptr;
+                s = s->previous;
+            }
+        }
+        Sender *previous;
+        QObject *receiver;
         QObject *sender;
         int signal;
-        int ref;
     };
 
 
@@ -189,12 +211,6 @@ public:
     void addConnection(int signal, Connection *c);
     void cleanConnectionLists();
 
-    static inline Sender *setCurrentSender(QObject *receiver,
-                                    Sender *sender);
-    static inline void resetCurrentSender(QObject *receiver,
-                                   Sender *currentSender,
-                                   Sender *previousSender);
-
     static QObjectPrivate *get(QObject *o) {
         return o->d_func();
     }
@@ -251,26 +267,6 @@ inline bool QObjectPrivate::isDeclarativeSignalConnected(uint signal_index) cons
             && QAbstractDeclarativeData::isSignalConnected(declarativeData, q_func(), signal_index);
 }
 
-inline QObjectPrivate::Sender *QObjectPrivate::setCurrentSender(QObject *receiver,
-                                                         Sender *sender)
-{
-    Sender *previousSender = receiver->d_func()->currentSender;
-    receiver->d_func()->currentSender = sender;
-    return previousSender;
-}
-
-inline void QObjectPrivate::resetCurrentSender(QObject *receiver,
-                                        Sender *currentSender,
-                                        Sender *previousSender)
-{
-    // ref is set to zero when this object is deleted during the metacall
-    if (currentSender->ref == 1)
-        receiver->d_func()->currentSender = previousSender;
-    // if we've recursed, we need to tell the caller about the objects deletion
-    if (previousSender)
-        previousSender->ref = currentSender->ref;
-}
-
 inline void QObjectPrivate::connectNotify(const QMetaMethod &signal)
 {
     q_ptr->connectNotify(signal);