Implement dummy QML lookups for "global" variables

When resolving names in the context of QML bindings, we now direct
runtime access to QQmlContextWrapper::resolveQmlPropertyLookupGetter. At the
moment this does basically the same as Runtime::method_loadName, which
we called earlier. However this now provides the opportunity to optimize
lookups in the QML context in a central place.

When performing a call on a scope or context object property, we also
did not use a CallName() instruction - which would have gotten the
thisObject wrong - but instead we use a dedicated
CallScopeObjectProperty and CallContextObjectProperty instruction. These
rely on identifying these properties at compile time, which goes away
with lookups (and also doesn't work when using ahead-of-time
compilation). Therefore the qml context property lookup is using a
getPropertyAndBase style signature and
Runtime::method_callQmlContextPropertyLookup uses that.

For the tests to pass, some error expectations need adjusting. In
particular the compile-time detection of write attempts to id objects is
now delayed to the run-time.

The old code path is still there and will be removed separately in the
next commit (as it is massive).

Task-number: QTBUG-69898
Change-Id: Iad1ff93d3758c4db984a7c2d003beee21ed2275c
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

4 files changed, 31 insertions, 0 deletions

diff --git a/src/qml/jit/qv4baselinejit.cpp b/src/qml/jit/qv4baselinejit.cpp
index 098bbfc6c6..47cef3b3bd 100644
--- a/src/qml/jit/qv4baselinejit.cpp
+++ b/src/qml/jit/qv4baselinejit.cpp
@@ -213,6 +213,16 @@ void BaselineJIT::generate_LoadGlobalLookup(int index)
     as->checkException();
 }
 
+void BaselineJIT::generate_LoadQmlContextPropertyLookup(int index)
+{
+    as->prepareCallWithArgCount(3);
+    as->passInt32AsArg(index, 2);
+    as->passEngineAsArg(1);
+    as->passFunctionAsArg(0);
+    BASELINEJIT_GENERATE_RUNTIME_CALL(Helpers::loadQmlContextPropertyLookup, CallResultDestination::InAccumulator);
+    as->checkException();
+}
+
 void BaselineJIT::generate_StoreNameSloppy(int name)
 {
     STORE_IP();
@@ -514,6 +524,18 @@ void BaselineJIT::generate_CallGlobalLookup(int index, int argc, int argv)
     as->checkException();
 }
 
+void BaselineJIT::generate_CallQmlContextPropertyLookup(int index, int argc, int argv)
+{
+    STORE_IP();
+    as->prepareCallWithArgCount(4);
+    as->passInt32AsArg(argc, 3);
+    as->passJSSlotAsArg(argv, 2);
+    as->passInt32AsArg(index, 1);
+    as->passEngineAsArg(0);
+    BASELINEJIT_GENERATE_RUNTIME_CALL(Runtime::method_callQmlContextPropertyLookup, CallResultDestination::InAccumulator);
+    as->checkException();
+}
+
 void BaselineJIT::generate_CallScopeObjectProperty(int propIdx, int base, int argc, int argv)
 {
     STORE_IP();
diff --git a/src/qml/jit/qv4baselinejit_p.h b/src/qml/jit/qv4baselinejit_p.h
index 98d23f4517..4db1eb1806 100644
--- a/src/qml/jit/qv4baselinejit_p.h
+++ b/src/qml/jit/qv4baselinejit_p.h
@@ -97,6 +97,7 @@ public:
     void generate_LoadClosure(int value) override;
     void generate_LoadName(int name) override;
     void generate_LoadGlobalLookup(int index) override;
+    void generate_LoadQmlContextPropertyLookup(int index) override;
     void generate_StoreNameSloppy(int name) override;
     void generate_StoreNameStrict(int name) override;
     void generate_LoadElement(int base) override;
@@ -128,6 +129,7 @@ public:
     void generate_CallName(int name, int argc, int argv) override;
     void generate_CallPossiblyDirectEval(int argc, int argv) override;
     void generate_CallGlobalLookup(int index, int argc, int argv) override;
+    void generate_CallQmlContextPropertyLookup(int index, int argc, int argv) override;
     void generate_CallScopeObjectProperty(int propIdx, int base, int argc, int argv) override;
     void generate_CallContextObjectProperty(int propIdx, int base, int argc, int argv) override;
     void generate_CallWithSpread(int func, int thisObject, int argc, int argv) override;
diff --git a/src/qml/jit/qv4jithelpers.cpp b/src/qml/jit/qv4jithelpers.cpp
index f43f37ad70..674fd8c8c8 100644
--- a/src/qml/jit/qv4jithelpers.cpp
+++ b/src/qml/jit/qv4jithelpers.cpp
@@ -70,6 +70,12 @@ ReturnedValue loadGlobalLookup(Function *f, ExecutionEngine *engine, int index)
     return l->globalGetter(l, engine);
 }
 
+ReturnedValue loadQmlContextPropertyLookup(Function *f, ExecutionEngine *engine, int index)
+{
+    Lookup *l = f->compilationUnit->runtimeLookups + index;
+    return l->qmlContextPropertyGetter(l, engine, nullptr);
+}
+
 ReturnedValue toObject(ExecutionEngine *engine, const Value &obj)
 {
     if (obj.isObject())
diff --git a/src/qml/jit/qv4jithelpers_p.h b/src/qml/jit/qv4jithelpers_p.h
index bd5f65034d..d9abfc071e 100644
--- a/src/qml/jit/qv4jithelpers_p.h
+++ b/src/qml/jit/qv4jithelpers_p.h
@@ -66,6 +66,7 @@ namespace Helpers {
 
 void convertThisToObject(ExecutionEngine *engine, Value *t);
 ReturnedValue loadGlobalLookup(Function *f, ExecutionEngine *engine, int index);
+ReturnedValue loadQmlContextPropertyLookup(Function *f, ExecutionEngine *engine, int index);
 ReturnedValue toObject(ExecutionEngine *engine, const Value &obj);
 ReturnedValue exp(const Value &base, const Value &exp);
 ReturnedValue getLookup(Function *f, ExecutionEngine *engine, const Value &base, int index);