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, 67 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4runtime_p.h b/src/qml/jsruntime/qv4runtime_p.h
index d9b46606c9..ffae55995f 100644
--- a/src/qml/jsruntime/qv4runtime_p.h
+++ b/src/qml/jsruntime/qv4runtime_p.h
@@ -56,8 +56,12 @@
 #include "qv4engine_p.h"
 #include "qv4math_p.h"
 #include "qv4runtimeapi_p.h"
-#include <QtCore/qnumeric.h>
+#ifndef V4_BOOTSTRAP
+#include <private/qqmlaccessors_p.h>
+#include <private/qqmlcontextwrapper_p.h>
+#endif
 
+#include <QtCore/qnumeric.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -417,6 +421,68 @@ inline Bool Runtime::method_toBoolean(const Value &value)
     return value.toBoolean();
 }
 
+inline ReturnedValue Runtime::method_accessQmlScopeObjectQRealProperty(const Value &context,
+                                                                       QQmlAccessors *accessors)
+{
+#ifndef V4_BOOTSTRAP
+    const QmlContext &c = static_cast<const QmlContext &>(context);
+    qreal rv = 0;
+    accessors->read(c.d()->qml->scopeObject, &rv);
+    return QV4::Encode(rv);
+#else
+    Q_UNUSED(context);
+    Q_UNUSED(accessors);
+    return QV4::Encode::undefined();
+#endif
+}
+
+inline ReturnedValue Runtime::method_accessQmlScopeObjectIntProperty(const Value &context,
+                                                                     QQmlAccessors *accessors)
+{
+#ifndef V4_BOOTSTRAP
+    const QmlContext &c = static_cast<const QmlContext &>(context);
+    int rv = 0;
+    accessors->read(c.d()->qml->scopeObject, &rv);
+    return QV4::Encode(rv);
+#else
+    Q_UNUSED(context);
+    Q_UNUSED(accessors);
+    return QV4::Encode::undefined();
+#endif
+}
+
+inline ReturnedValue Runtime::method_accessQmlScopeObjectBoolProperty(const Value &context,
+                                                                      QQmlAccessors *accessors)
+{
+#ifndef V4_BOOTSTRAP
+    const QmlContext &c = static_cast<const QmlContext &>(context);
+    bool rv = false;
+    accessors->read(c.d()->qml->scopeObject, &rv);
+    return QV4::Encode(rv);
+#else
+    Q_UNUSED(context);
+    Q_UNUSED(accessors);
+    return QV4::Encode::undefined();
+#endif
+}
+
+inline ReturnedValue Runtime::method_accessQmlScopeObjectQStringProperty(ExecutionEngine *engine,
+                                                                         const Value &context,
+                                                                         QQmlAccessors *accessors)
+{
+#ifndef V4_BOOTSTRAP
+    const QmlContext &c = static_cast<const QmlContext &>(context);
+    QString rv;
+    accessors->read(c.d()->qml->scopeObject, &rv);
+    return QV4::Encode(engine->newString(rv));
+#else
+    Q_UNUSED(engine);
+    Q_UNUSED(context);
+    Q_UNUSED(accessors);
+    return QV4::Encode::undefined();
+#endif
+}
+
 } // namespace QV4
 
 QT_END_NAMESPACE