Improve performance of property binding evaluation

Improves performance of binding evaluation by ~20% for
simple C++ bindings by simplifying and inlining the code
that clears the array of property observers.

Change-Id: I829ac1895f1673367d737944d950360015a5b435
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

3 files changed, 4 insertions, 6 deletions

diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index b362319f22..f62810518b 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -279,8 +279,6 @@ QPropertyObserver::~QPropertyObserver()
     d.unlink();
 }
 
-QPropertyObserver::QPropertyObserver() = default;
-
 QPropertyObserver::QPropertyObserver(QPropertyObserver &&other)
 {
     std::swap(bindingToMarkDirty, other.bindingToMarkDirty);
diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 4a323fe8fe..994eb24cea 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -607,7 +607,7 @@ public:
         ObserverNotifiesAlias,
     };
 
-    QPropertyObserver();
+    QPropertyObserver() = default;
     QPropertyObserver(QPropertyObserver &&other);
     QPropertyObserver &operator=(QPropertyObserver &&other);
     ~QPropertyObserver();
diff --git a/src/corelib/kernel/qpropertybinding_p.h b/src/corelib/kernel/qpropertybinding_p.h
index 151f5543d5..6257e4506e 100644
--- a/src/corelib/kernel/qpropertybinding_p.h
+++ b/src/corelib/kernel/qpropertybinding_p.h
@@ -148,9 +148,9 @@ public:
 
     void clearDependencyObservers() {
         if (!hasStaticObserver) {
-            for (size_t i = 0; i < inlineDependencyObservers.size(); ++i) {
-                QPropertyObserver empty;
-                qSwap(inlineDependencyObservers[i], empty);
+            for (size_t i = 0; i < qMin(dependencyObserverCount, inlineDependencyObservers.size()); ++i) {
+                QPropertyObserverPointer p{&inlineDependencyObservers[i]};
+                p.unlink();
             }
         }
         if (heapObservers)