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>

12 files changed, 70 insertions, 22 deletions

diff --git a/src/qml/compiler/qqmlirbuilder.cpp b/src/qml/compiler/qqmlirbuilder.cpp
index 59b9968bf6..4b4d3c27e8 100644
--- a/src/qml/compiler/qqmlirbuilder.cpp
+++ b/src/qml/compiler/qqmlirbuilder.cpp
@@ -2228,7 +2228,8 @@ void JSCodeGen::beginFunctionBodyHook()
 QV4::Compiler::Codegen::Reference JSCodeGen::fallbackNameLookup(const QString &name)
 {
 #ifndef V4_BOOTSTRAP
-    if (_disableAcceleratedLookups)
+    // FIXME: Remove this function.
+    if (_disableAcceleratedLookups || true)
         return Reference();
 
     // Implement QML lookup semantics in the current file context.
diff --git a/src/qml/compiler/qv4bytecodehandler.cpp b/src/qml/compiler/qv4bytecodehandler.cpp
index af86b70014..a34472010b 100644
--- a/src/qml/compiler/qv4bytecodehandler.cpp
+++ b/src/qml/compiler/qv4bytecodehandler.cpp
@@ -192,6 +192,9 @@ std::vector<int> ByteCodeHandler::collectLabelsInBytecode(const char *code, uint
         COLLECTOR_BEGIN_INSTR(LoadGlobalLookup)
         COLLECTOR_END_INSTR(LoadGlobalLookup)
 
+        COLLECTOR_BEGIN_INSTR(LoadQmlContextPropertyLookup)
+        COLLECTOR_END_INSTR(LoadQmlContextPropertyLookup)
+
         COLLECTOR_BEGIN_INSTR(StoreNameSloppy)
         COLLECTOR_END_INSTR(StoreNameSloppy)
 
@@ -270,6 +273,9 @@ std::vector<int> ByteCodeHandler::collectLabelsInBytecode(const char *code, uint
         COLLECTOR_BEGIN_INSTR(CallGlobalLookup)
         COLLECTOR_END_INSTR(CallGlobalLookup)
 
+        COLLECTOR_BEGIN_INSTR(CallQmlContextPropertyLookup)
+        COLLECTOR_END_INSTR(CallQmlContextPropertyLookup)
+
         COLLECTOR_BEGIN_INSTR(CallScopeObjectProperty)
         COLLECTOR_END_INSTR(CallScopeObjectProperty)
 
diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 66c334d197..de87d6d48c 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -1982,11 +1982,19 @@ void Codegen::handleCall(Reference &base, Arguments calldata, int slotForFunctio
             call.argv = calldata.argv;
             bytecodeGenerator->addInstruction(call);
         } else if (!disable_lookups && useFastLookups && base.global) {
-            Instruction::CallGlobalLookup call;
-            call.index = registerGlobalGetterLookup(base.nameAsIndex());
-            call.argc = calldata.argc;
-            call.argv = calldata.argv;
-            bytecodeGenerator->addInstruction(call);
+            if (base.qmlGlobal) {
+                Instruction::CallQmlContextPropertyLookup call;
+                call.index = registerQmlContextPropertyGetterLookup(base.nameAsIndex());
+                call.argc = calldata.argc;
+                call.argv = calldata.argv;
+                bytecodeGenerator->addInstruction(call);
+            } else {
+                Instruction::CallGlobalLookup call;
+                call.index = registerGlobalGetterLookup(base.nameAsIndex());
+                call.argc = calldata.argc;
+                call.argv = calldata.argv;
+                bytecodeGenerator->addInstruction(call);
+            }
         } else {
             Instruction::CallName call;
             call.name = base.nameAsIndex();
@@ -2361,8 +2369,9 @@ Codegen::Reference Codegen::referenceForName(const QString &name, bool isLhs, co
         return fallback;
 
     Reference r = Reference::fromName(this, name);
-    r.global = useFastLookups && (resolved.type == Context::ResolvedName::Global);
-    if (!r.global && canAccelerateGlobalLookups() && m_globalNames.contains(name))
+    r.global = useFastLookups && (resolved.type == Context::ResolvedName::Global || resolved.type == Context::ResolvedName::QmlGlobal);
+    r.qmlGlobal = resolved.type == Context::ResolvedName::QmlGlobal;
+    if (!r.global && !r.qmlGlobal && m_globalNames.contains(name))
         r.global = true;
     return r;
 }
@@ -4385,9 +4394,15 @@ QT_WARNING_POP
             }
         }
         if (!disable_lookups && global) {
-            Instruction::LoadGlobalLookup load;
-            load.index = codegen->registerGlobalGetterLookup(nameAsIndex());
-            codegen->bytecodeGenerator->addInstruction(load);
+            if (qmlGlobal) {
+                Instruction::LoadQmlContextPropertyLookup load;
+                load.index = codegen->registerQmlContextPropertyGetterLookup(nameAsIndex());
+                codegen->bytecodeGenerator->addInstruction(load);
+            } else {
+                Instruction::LoadGlobalLookup load;
+                load.index = codegen->registerGlobalGetterLookup(nameAsIndex());
+                codegen->bytecodeGenerator->addInstruction(load);
+            }
         } else {
             Instruction::LoadName load;
             load.name = nameAsIndex();
diff --git a/src/qml/compiler/qv4codegen_p.h b/src/qml/compiler/qv4codegen_p.h
index 0b25d9c53d..b1cc4c090a 100644
--- a/src/qml/compiler/qv4codegen_p.h
+++ b/src/qml/compiler/qv4codegen_p.h
@@ -207,7 +207,8 @@ public:
             subscriptRequiresTDZCheck(false),
             stackSlotIsLocalOrArgument(false),
             isVolatile(false),
-            global(false)
+            global(false),
+            qmlGlobal(false)
         {}
 
         Reference(const Reference &) = default;
@@ -421,6 +422,7 @@ public:
         quint32 stackSlotIsLocalOrArgument:1;
         quint32 isVolatile:1;
         quint32 global:1;
+        quint32 qmlGlobal:1;
 
     private:
         void storeAccumulator() const;
@@ -553,6 +555,7 @@ public:
     int registerGetterLookup(int nameIndex) { return jsUnitGenerator->registerGetterLookup(nameIndex); }
     int registerSetterLookup(int nameIndex) { return jsUnitGenerator->registerSetterLookup(nameIndex); }
     int registerGlobalGetterLookup(int nameIndex) { return jsUnitGenerator->registerGlobalGetterLookup(nameIndex); }
+    int registerQmlContextPropertyGetterLookup(int nameIndex) { return jsUnitGenerator->registerQmlContextPropertyGetterLookup(nameIndex); }
 
     // Returns index in _module->functions
     virtual int defineFunction(const QString &name, AST::Node *ast,
diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index e428340f62..6701443971 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -170,6 +170,8 @@ QV4::Function *CompilationUnit::linkToEngine(ExecutionEngine *engine)
                 l->setter = QV4::Lookup::setterGeneric;
             else if (type == CompiledData::Lookup::Type_GlobalGetter)
                 l->globalGetter = QV4::Lookup::globalGetterGeneric;
+            else if (type == CompiledData::Lookup::Type_QmlContextPropertyGetter)
+                l->qmlContextPropertyGetter = QQmlContextWrapper::resolveQmlContextPropertyLookupGetter;
             l->nameIndex = compiledLookups[i].nameIndex;
         }
     }
diff --git a/src/qml/compiler/qv4compileddata_p.h b/src/qml/compiler/qv4compileddata_p.h
index c4821daa86..d63b1fd2b9 100644
--- a/src/qml/compiler/qv4compileddata_p.h
+++ b/src/qml/compiler/qv4compileddata_p.h
@@ -160,9 +160,10 @@ static_assert(sizeof(RegExp) == 4, "RegExp structure needs to have the expected
 struct Lookup
 {
     enum Type : unsigned int {
-        Type_Getter = 0x0,
-        Type_Setter = 0x1,
-        Type_GlobalGetter = 2
+        Type_Getter = 0,
+        Type_Setter = 1,
+        Type_GlobalGetter = 2,
+        Type_QmlContextPropertyGetter = 3
     };
 
     union {
diff --git a/src/qml/compiler/qv4compiler.cpp b/src/qml/compiler/qv4compiler.cpp
index 3076c6b526..a3c9347c67 100644
--- a/src/qml/compiler/qv4compiler.cpp
+++ b/src/qml/compiler/qv4compiler.cpp
@@ -154,15 +154,19 @@ int QV4::Compiler::JSUnitGenerator::registerSetterLookup(int nameIndex)
     return lookups.size() - 1;
 }
 
-int QV4::Compiler::JSUnitGenerator::registerGlobalGetterLookup(const QString &name)
+int QV4::Compiler::JSUnitGenerator::registerGlobalGetterLookup(int nameIndex)
 {
-    return registerGlobalGetterLookup(registerString(name));
+    CompiledData::Lookup l;
+    l.type_and_flags = CompiledData::Lookup::Type_GlobalGetter;
+    l.nameIndex = nameIndex;
+    lookups << l;
+    return lookups.size() - 1;
 }
 
-int QV4::Compiler::JSUnitGenerator::registerGlobalGetterLookup(int nameIndex)
+int QV4::Compiler::JSUnitGenerator::registerQmlContextPropertyGetterLookup(int nameIndex)
 {
     CompiledData::Lookup l;
-    l.type_and_flags = CompiledData::Lookup::Type_GlobalGetter;
+    l.type_and_flags = CompiledData::Lookup::Type_QmlContextPropertyGetter;
     l.nameIndex = nameIndex;
     lookups << l;
     return lookups.size() - 1;
diff --git a/src/qml/compiler/qv4compiler_p.h b/src/qml/compiler/qv4compiler_p.h
index 2f5889ab53..49e334bb81 100644
--- a/src/qml/compiler/qv4compiler_p.h
+++ b/src/qml/compiler/qv4compiler_p.h
@@ -118,8 +118,8 @@ struct Q_QML_PRIVATE_EXPORT JSUnitGenerator {
     int registerGetterLookup(int nameIndex);
     int registerSetterLookup(const QString &name);
     int registerSetterLookup(int nameIndex);
-    int registerGlobalGetterLookup(const QString &name);
     int registerGlobalGetterLookup(int nameIndex);
+    int registerQmlContextPropertyGetterLookup(int nameIndex);
 
     int registerRegExp(QQmlJS::AST::RegExpLiteral *regexp);
 
diff --git a/src/qml/compiler/qv4compilercontext.cpp b/src/qml/compiler/qv4compilercontext.cpp
index 5772bff7bf..84c5d67e8d 100644
--- a/src/qml/compiler/qv4compilercontext.cpp
+++ b/src/qml/compiler/qv4compilercontext.cpp
@@ -187,10 +187,13 @@ Context::ResolvedName Context::resolveName(const QString &name, const QQmlJS::AS
     }
 
     // ### can we relax the restrictions here?
-    if (c->contextType == ContextType::Eval || c->contextType == ContextType::Binding)
+    if (c->contextType == ContextType::Eval)
         return result;
 
-    result.type = ResolvedName::Global;
+    if (c->contextType == ContextType::Binding)
+        result.type = ResolvedName::QmlGlobal;
+    else
+        result.type = ResolvedName::Global;
     return result;
 }
 
diff --git a/src/qml/compiler/qv4compilercontext_p.h b/src/qml/compiler/qv4compilercontext_p.h
index 328715da07..c9e54c0d1b 100644
--- a/src/qml/compiler/qv4compilercontext_p.h
+++ b/src/qml/compiler/qv4compilercontext_p.h
@@ -336,6 +336,7 @@ struct Context {
     struct ResolvedName {
         enum Type {
             Unresolved,
+            QmlGlobal,
             Global,
             Local,
             Stack,
diff --git a/src/qml/compiler/qv4instr_moth.cpp b/src/qml/compiler/qv4instr_moth.cpp
index 83aca3a02c..d2e95b83c4 100644
--- a/src/qml/compiler/qv4instr_moth.cpp
+++ b/src/qml/compiler/qv4instr_moth.cpp
@@ -286,6 +286,10 @@ void dumpBytecode(const char *code, int len, int nLocals, int nFormals, int /*st
             d << index;
         MOTH_END_INSTR(LoadGlobalLookup)
 
+        MOTH_BEGIN_INSTR(LoadQmlContextPropertyLookup)
+            d << index;
+        MOTH_END_INSTR(LoadQmlContextPropertyLookup)
+
         MOTH_BEGIN_INSTR(StoreNameSloppy)
             d << name;
         MOTH_END_INSTR(StoreNameSloppy)
@@ -388,6 +392,10 @@ void dumpBytecode(const char *code, int len, int nLocals, int nFormals, int /*st
             d << index << dumpArguments(argc, argv, nFormals);
         MOTH_END_INSTR(CallGlobalLookup)
 
+        MOTH_BEGIN_INSTR(CallQmlContextPropertyLookup)
+            d << index << dumpArguments(argc, argv, nFormals);
+        MOTH_END_INSTR(CallQmlContextPropertyLookup)
+
         MOTH_BEGIN_INSTR(CallScopeObjectProperty)
             d << dumpRegister(base, nFormals) << "." << name << dumpArguments(argc, argv, nFormals);
         MOTH_END_INSTR(CallScopeObjectProperty)
diff --git a/src/qml/compiler/qv4instr_moth_p.h b/src/qml/compiler/qv4instr_moth_p.h
index 2ca8f692b8..1c77e6050c 100644
--- a/src/qml/compiler/qv4instr_moth_p.h
+++ b/src/qml/compiler/qv4instr_moth_p.h
@@ -86,6 +86,7 @@ QT_BEGIN_NAMESPACE
 #define INSTR_LoadClosure(op) INSTRUCTION(op, LoadClosure, 1, value)
 #define INSTR_LoadName(op) INSTRUCTION(op, LoadName, 1, name)
 #define INSTR_LoadGlobalLookup(op) INSTRUCTION(op, LoadGlobalLookup, 1, index)
+#define INSTR_LoadQmlContextPropertyLookup(op) INSTRUCTION(op, LoadQmlContextPropertyLookup, 1, index)
 #define INSTR_StoreNameSloppy(op) INSTRUCTION(op, StoreNameSloppy, 1, name)
 #define INSTR_StoreNameStrict(op) INSTRUCTION(op, StoreNameStrict, 1, name)
 #define INSTR_LoadProperty(op) INSTRUCTION(op, LoadProperty, 1, name)
@@ -113,6 +114,7 @@ QT_BEGIN_NAMESPACE
 #define INSTR_CallName(op) INSTRUCTION(op, CallName, 3, name, argc, argv)
 #define INSTR_CallPossiblyDirectEval(op) INSTRUCTION(op, CallPossiblyDirectEval, 2, argc, argv)
 #define INSTR_CallGlobalLookup(op) INSTRUCTION(op, CallGlobalLookup, 3, index, argc, argv)
+#define INSTR_CallQmlContextPropertyLookup(op) INSTRUCTION(op, CallQmlContextPropertyLookup, 3, index, argc, argv)
 #define INSTR_CallScopeObjectProperty(op) INSTRUCTION(op, CallScopeObjectProperty, 4, name, base, argc, argv)
 #define INSTR_CallContextObjectProperty(op) INSTRUCTION(op, CallContextObjectProperty, 4, name, base, argc, argv)
 #define INSTR_CallWithSpread(op) INSTRUCTION(op, CallWithSpread, 4, func, thisObject, argc, argv)
@@ -228,6 +230,7 @@ QT_BEGIN_NAMESPACE
     F(LoadClosure) \
     F(LoadName) \
     F(LoadGlobalLookup) \
+    F(LoadQmlContextPropertyLookup) \
     F(StoreNameSloppy) \
     F(StoreNameStrict) \
     F(LoadElement) \
@@ -296,6 +299,7 @@ QT_BEGIN_NAMESPACE
     F(CallName) \
     F(CallPossiblyDirectEval) \
     F(CallGlobalLookup) \
+    F(CallQmlContextPropertyLookup) \
     F(CallScopeObjectProperty) \
     F(CallContextObjectProperty) \
     F(CallWithSpread) \