From 0cae9f87c8ed351f605ccb31e3dda3143028a484 Mon Sep 17 00:00:00 2001
From: Thomas McGuire <thomas.mcguire.qnx@kdab.com>
Date: Fri, 24 Aug 2012 15:28:46 +0200
Subject: [PATCH] Reduce memory usage of QV4Bindings::Subscription by 8 bytes.

There is no need to store the method, as it can be calculated via
pointer arithmetic.
That leaves the active flag, which now is the last bit of the bindings
pointer.

Change-Id: I17b443e63be2d950aa80ad15cc76372b415c3dd6
Reviewed-by: Matthew Vogt <matthew.vogt@nokia.com>
---
 src/qml/qml/v4/qv4bindings.cpp | 52 ++++++++++++++++++++++++++++++------------
 src/qml/qml/v4/qv4bindings_p.h | 16 +++++++++----
 2 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/src/qml/qml/v4/qv4bindings.cpp b/src/qml/qml/v4/qv4bindings.cpp
index 7d64de7..68e9a1a 100644
--- a/src/qml/qml/v4/qv4bindings.cpp
+++ b/src/qml/qml/v4/qv4bindings.cpp
@@ -434,8 +434,8 @@ void QV4Bindings::Binding::disconnect()
             Binding * const binding = parent->bindings + bindingRef->binding;
             if (binding == this) {
                 Subscription * const sub = parent->subscriptions + subIndex;
-                if (sub->active) {
-                    sub->active = false;
+                if (sub->active()) {
+                    sub->setActive(false);
                     sub->disconnect();
                 }
             }
@@ -444,15 +444,42 @@ void QV4Bindings::Binding::disconnect()
 }
 
 QV4Bindings::Subscription::Subscription()
-    : bindings(0), method(-1), active(false)
+    : m_bindings(0)
 {
     setCallback(QQmlNotifierEndpoint::QV4BindingsSubscription);
 }
 
+int QV4Bindings::Subscription::method() const
+{
+    Q_ASSERT(bindings() != 0);
+    return (this - bindings()->subscriptions);
+}
+
+void QV4Bindings::Subscription::setBindings(QV4Bindings *bindings)
+{
+    m_bindings = bindings;
+}
+
+QV4Bindings *QV4Bindings::Subscription::bindings() const
+{
+    return *m_bindings;
+}
+
+bool QV4Bindings::Subscription::active() const
+{
+    return m_bindings.flag();
+}
+
+void QV4Bindings::Subscription::setActive(bool active)
+{
+    m_bindings.setFlagValue(active);
+}
+
 void QV4BindingsSubscription_callback(QQmlNotifierEndpoint *e, void **)
 {
     QV4Bindings::Subscription *s = static_cast<QV4Bindings::Subscription *>(e);
-    s->bindings->subscriptionNotify(s->method);
+    Q_ASSERT(s->bindings());
+    s->bindings()->subscriptionNotify(s->method());
 }
 
 void QV4Bindings::subscriptionNotify(int id)
@@ -558,12 +585,11 @@ void QV4Bindings::subscribeId(QQmlContextData *p, int idIndex, int subIndex)
     sub->disconnect();
 
     if (p->idValues[idIndex]) {
-        sub->bindings = this;
-        sub->method = subIndex;
+        sub->setBindings(this);
         sub->connect(&p->idValues[idIndex].bindings);
-        sub->active = true;
+        sub->setActive(true);
     } else {
-        sub->active = false;
+        sub->setActive(false);
     }
 }
 
@@ -572,14 +598,13 @@ void QV4Bindings::subscribe(QObject *o, int notifyIndex, int subIndex, QQmlEngin
     Subscription *sub = (subscriptions + subIndex);
     if (sub->isConnected(o, notifyIndex))
         return;
-    sub->bindings = this;
-    sub->method = subIndex;
+    sub->setBindings(this);
     if (o) {
         sub->connect(o, notifyIndex, e);
-        sub->active = true;
+        sub->setActive(true);
     } else {
         sub->disconnect();
-        sub->active = false;
+        sub->setActive(false);
     }
 }
 
@@ -992,8 +1017,7 @@ void QV4Bindings::run(int instrIndex, quint32 &executedBlocks,
                     Subscription *sub = 0;
                     if (subIdx != -1) {
                         sub = (subscriptions + subIdx);
-                        sub->bindings = this;
-                        sub->method = subIdx;
+                        sub->setBindings(this);
                     }
                     sub->connect(notifier);
                 }
diff --git a/src/qml/qml/v4/qv4bindings_p.h b/src/qml/qml/v4/qv4bindings_p.h
index 04fca85..4053c47 100644
--- a/src/qml/qml/v4/qv4bindings_p.h
+++ b/src/qml/qml/v4/qv4bindings_p.h
@@ -122,11 +122,19 @@ private:
     {
     public:
         inline Subscription();
-        QV4Bindings *bindings;
-        int method:31;
 
-        // Subscriptions are not shared between bindings (anymore), so this can be a simple bool flag
-        bool active:1;
+        // Index of this Subscription into the QV4Bindings::subscriptions array.
+        // This may not be used before setBindings() was called.
+        inline int method() const;
+
+        inline void setBindings(QV4Bindings *bindings);
+        inline QV4Bindings *bindings() const;
+
+        inline bool active() const;
+        inline void setActive(bool active);
+
+        // Pointer to the parent QV4Bindings. The flag is used as the 'active' value.
+        QFlagPointer<QV4Bindings> m_bindings;
     };
     friend void QV4BindingsSubscription_callback(QQmlNotifierEndpoint *e, void **);
 
-- 
2.7.4