V4: Pass scope around as parameters inside the runtime.

The implementation of many (or all) runtime functions consist of first
creating a QV4::Scope, which saves and restores the JS stack pointer.
It also prevents tail-calls because of that restoring behavior. In many
cases it suffices to do that at the entry-point of the runtime.

The return value of a JS function call is now also stored in the scope.
Previously, all return values were stored in a ScopedValue, got loaded
on return, and immediately stored in another ScopedValue in the caller.
This resulted in a lot of stores, where now there is only one store
needed, and no extra ScopedValue for every function.

Change-Id: I13d80fc0ce72c5702ef1536d41d12f710c5914fa
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/qml/qml/qqmlvmemetaobject.cpp b/src/qml/qml/qqmlvmemetaobject.cpp
index 6907b26cd8..a9aec4cded 100644
--- a/src/qml/qml/qqmlvmemetaobject.cpp
+++ b/src/qml/qml/qqmlvmemetaobject.cpp
@@ -945,15 +945,14 @@ int QQmlVMEMetaObject::metaCall(QObject *o, QMetaObject::Call c, int _id, void *
                 for (uint ii = 0; ii < parameterCount; ++ii)
                     callData->args[ii] = scope.engine->fromVariant(*(QVariant *)a[ii + 1]);
 
-                QV4::ScopedValue result(scope);
-                result = function->call(callData);
+                function->call(scope, callData);
                 if (scope.hasException()) {
                     QQmlError error = scope.engine->catchExceptionAsQmlError();
                     if (error.isValid())
                         ep->warning(error);
                     if (a[0]) *(QVariant *)a[0] = QVariant();
                 } else {
-                    if (a[0]) *(QVariant *)a[0] = scope.engine->toVariant(result, 0);
+                    if (a[0]) *(QVariant *)a[0] = scope.engine->toVariant(scope.result, 0);
                 }
 
                 ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.