QmlCompiler: Implement ConvertThisToObject and basic DTZ

We know that 'this' is a QObject* since the metatypes stack frame
mandates it. Whenever you pass 'this' to anything it's loaded from the
special 'This' stack slot which then triggers a DTZ check. A DTZ check
is a noop if we can prove that the type is statically known, though.

In QmlCompiler, if we have a valid register content, then the register
has been set in all code paths that lead to the instruction in question.

Fixes: QTBUG-111439
Change-Id: I81d1cd140eea63f85628c3bef3a8f6db0a12096d
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/qml/qml/qqml.cpp b/src/qml/qml/qqml.cpp
index d258ace774..7bbfe39ae9 100644
--- a/src/qml/qml/qqml.cpp
+++ b/src/qml/qml/qqml.cpp
@@ -804,6 +804,12 @@ void qmlRegisterTypeAndRevisions<QQmlTypeNotAvailable, void>(
     qmlregister(TypeAndRevisionsRegistration, &type);
 }
 
+QObject *AOTCompiledContext::thisObject() const
+{
+    return static_cast<QV4::MetaTypesStackFrame *>(engine->handle()->currentStackFrame)
+            ->thisObject();
+}
+
 QQmlEngine *AOTCompiledContext::qmlEngine() const
 {
     return qmlContext ? qmlContext->engine() : nullptr;