QML: When available, use QQmlAccessors to read properties.

When a property is read from a QObject or the QML scope object, and we
can statically resolve the type to qreal/QObject/int/bool/QString, and
the property has an accessor declared for it, then use that accessor to
do the read.

This collapses the path of e.g.:
  Runtime::getQmlScopeObjectProperty
    -> QObjectWrapper::getProperty
      -> QObjectWrapper::getProperty
        -> LoadProperty
          -> QQmlAccessor::read
(all of which do various checks for all the stuff mentioned above) to:
  Runtime::accessQmlScopeObjectQRealProperty
    -> QQmlAccessor::read
which is a simple 4-line function, and doesn't need to do any check.

According to valgrind, this saves 170 instructions on x86 for the
simple binding:

Item {
    width: height
}

Change-Id: I0761d01e8f1a3c13ecbffe2d8e0317ce9c0a4db0
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/tests/benchmarks/qml/creation/tst_creation.cpp b/tests/benchmarks/qml/creation/tst_creation.cpp
index 224732913c..2c8aa04a6a 100644
--- a/tests/benchmarks/qml/creation/tst_creation.cpp
+++ b/tests/benchmarks/qml/creation/tst_creation.cpp
@@ -68,6 +68,12 @@ private slots:
     void itemtests_qml_data();
     void itemtests_qml();
 
+    void bindings_cpp();
+    void bindings_cpp2();
+    void bindings_qml();
+
+    void bindings_parent_qml();
+
 private:
     QQmlEngine engine;
 };
@@ -373,6 +379,89 @@ void tst_creation::itemtests_qml()
     QBENCHMARK { delete component.create(); }
 }
 
+void tst_creation::bindings_cpp()
+{
+    QQuickItem item;
+    QMetaProperty widthProp = item.metaObject()->property(item.metaObject()->indexOfProperty("width"));
+    QMetaProperty heightProp = item.metaObject()->property(item.metaObject()->indexOfProperty("height"));
+    connect(&item, &QQuickItem::heightChanged, [&item, &widthProp, &heightProp](){
+        QVariant height = heightProp.read(&item);
+        widthProp.write(&item, height);
+    });
+
+    int height = 0;
+    QBENCHMARK {
+        item.setHeight(++height);
+    }
+}
+
+void tst_creation::bindings_cpp2()
+{
+    QQuickItem item;
+    int widthProp = item.metaObject()->indexOfProperty("width");
+    int heightProp = item.metaObject()->indexOfProperty("height");
+    connect(&item, &QQuickItem::heightChanged, [&item, widthProp, heightProp](){
+
+        qreal height = -1;
+        void *args[] = { &height, 0 };
+        QMetaObject::metacall(&item, QMetaObject::ReadProperty, heightProp, args);
+
+        int flags = 0;
+        int status = -1;
+        void *argv[] = { &height, 0, &status, &flags };
+        QMetaObject::metacall(&item, QMetaObject::WriteProperty, widthProp, argv);
+    });
+
+    int height = 0;
+    QBENCHMARK {
+        item.setHeight(++height);
+    }
+}
+
+void tst_creation::bindings_qml()
+{
+    QByteArray data = "import QtQuick 2.0\nItem { width: height }";
+
+    QQmlComponent component(&engine);
+    component.setData(data, QUrl());
+    if (!component.isReady()) {
+        qWarning() << "Unable to create component: " << component.errorString();
+        return;
+    }
+
+    QQuickItem *obj = dynamic_cast<QQuickItem *>(component.create());
+    QVERIFY(obj != nullptr);
+
+    int height = 0;
+    QBENCHMARK {
+        obj->setHeight(++height);
+    }
+
+    delete obj;
+}
+
+void tst_creation::bindings_parent_qml()
+{
+    QByteArray data = "import QtQuick 2.0\nItem { Item { width: parent.height }}";
+
+    QQmlComponent component(&engine);
+    component.setData(data, QUrl());
+    if (!component.isReady()) {
+        qWarning() << "Unable to create component: " << component.errorString();
+        return;
+    }
+
+    QQuickItem *obj = dynamic_cast<QQuickItem *>(component.create());
+    QVERIFY(obj != nullptr);
+
+    int height = 0;
+    QBENCHMARK {
+        obj->setHeight(++height);
+    }
+
+    delete obj;
+}
+
 QTEST_MAIN(tst_creation)
 
 #include "tst_creation.moc"