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, 5 insertions, 4 deletions

diff --git a/src/qml/qml/qqmlexpression.cpp b/src/qml/qml/qqmlexpression.cpp
index d48b6ad1d3..6afbd05e3e 100644
--- a/src/qml/qml/qqmlexpression.cpp
+++ b/src/qml/qml/qqmlexpression.cpp
@@ -245,14 +245,15 @@ void QQmlExpression::setExpression(const QString &expression)
 }
 
 // Must be called with a valid handle scope
-QV4::ReturnedValue QQmlExpressionPrivate::v4value(bool *isUndefined)
+void QQmlExpressionPrivate::v4value(bool *isUndefined, QV4::Scope &scope)
 {
     if (!expressionFunctionValid) {
         createQmlBinding(context(), scopeObject(), expression, url, line);
         expressionFunctionValid = true;
     }
 
-    return evaluate(isUndefined);
+    QV4::ScopedCallData callData(scope);
+    evaluate(callData, isUndefined, scope);
 }
 
 QVariant QQmlExpressionPrivate::value(bool *isUndefined)
@@ -271,9 +272,9 @@ QVariant QQmlExpressionPrivate::value(bool *isUndefined)
 
     {
         QV4::Scope scope(QV8Engine::getV4(ep->v8engine()));
-        QV4::ScopedValue result(scope, v4value(isUndefined));
+        v4value(isUndefined, scope);
         if (!hasError())
-            rv = scope.engine->toVariant(result, -1);
+            rv = scope.engine->toVariant(scope.result, -1);
     }
 
     ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.