Avoid needless construction and destruction of return values

In most cases the AOT compiled function will successfully placement-new
the return value. Therefore, we can provide uninitialized space. Only do
the construct/destruct dance in the cases when it's already slow.

Change-Id: Ia339774fde03e459f290f167ddadd1c47a644b8e
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlvmemetaobject.cpp b/src/qml/qml/qqmlvmemetaobject.cpp
index 7580d45104..7e6e4b1ef3 100644
--- a/src/qml/qml/qqmlvmemetaobject.cpp
+++ b/src/qml/qml/qqmlvmemetaobject.cpp
@@ -1002,10 +1002,14 @@ int QQmlVMEMetaObject::metaCall(QObject *o, QMetaObject::Call c, int _id, void *
                 if (arguments && arguments->names) {
                     const auto parameterCount = arguments->names->count();
                     Q_ASSERT(parameterCount == function->formalParameterCount());
+                    if (void *result = a[0])
+                        arguments->types[0].destruct(result);
                     function->call(v4->globalObject, a, arguments->types, parameterCount);
                 } else {
                     Q_ASSERT(function->formalParameterCount() == 0);
                     const QMetaType returnType = methodData->propType();
+                    if (void *result = a[0])
+                        returnType.destruct(result);
                     function->call(v4->globalObject, a, &returnType, 0);
                 }