Better inheritance structure for functions

Give Arrow functions their own representation. This also prepares
for further optimizations especially for the instanceof operator.

Change-Id: I1f70c0271169a237e1acdeb7fe855be957ba2ea5
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

6 files changed, 63 insertions, 33 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index 672196dd3f..bf8a91f6e1 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -347,10 +347,11 @@ ExecutionEngine::ExecutionEngine(QJSEngine *jsEngine)
     ic = newInternalClass(FunctionObject::staticVTable(), functionPrototype());
     classes[Class_FunctionObject] = ic->d();
     ic = ic->addMember(id_name()->propertyKey(), Attr_ReadOnly, &index);
-    Q_ASSERT(index == Heap::ScriptFunction::Index_Name);
-    ic = ic->changeVTable(ScriptFunction::staticVTable());
+    Q_ASSERT(index == Heap::ArrowFunction::Index_Name);
     ic = ic->addMember(id_length()->propertyKey(), Attr_ReadOnly_ButConfigurable, &index);
-    Q_ASSERT(index == Heap::ScriptFunction::Index_Length);
+    Q_ASSERT(index == Heap::ArrowFunction::Index_Length);
+    classes[Class_ArrowFunction] = ic->changeVTable(ArrowFunction::staticVTable());
+    ic = ic->changeVTable(ScriptFunction::staticVTable());
     classes[Class_ScriptFunction] = ic->d();
     ic = ic->changeVTable(ConstructorFunction::staticVTable());
     classes[Class_ConstructorFunction] = ic->d();
diff --git a/src/qml/jsruntime/qv4enginebase_p.h b/src/qml/jsruntime/qv4enginebase_p.h
index 789ec5d970..b5cfea8863 100644
--- a/src/qml/jsruntime/qv4enginebase_p.h
+++ b/src/qml/jsruntime/qv4enginebase_p.h
@@ -99,6 +99,7 @@ struct Q_QML_EXPORT EngineBase {
         Class_Object,
         Class_ArrayObject,
         Class_FunctionObject,
+        Class_ArrowFunction,
         Class_GeneratorFunction,
         Class_GeneratorObject,
         Class_StringObject,
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 8a674bc7fa..6fc2d45630 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -168,6 +168,8 @@ ReturnedValue FunctionObject::virtualCall(const FunctionObject *, const Value *,
 
 Heap::FunctionObject *FunctionObject::createScriptFunction(ExecutionContext *scope, Function *function)
 {
+    if (function->isArrowFunction())
+        return scope->engine()->memoryManager->allocate<ArrowFunction>(scope, function);
     return scope->engine()->memoryManager->allocate<ScriptFunction>(scope, function);
 }
 
@@ -213,6 +215,17 @@ bool FunctionObject::isBoundFunction() const
     return d()->vtable() == BoundFunction::staticVTable();
 }
 
+ReturnedValue FunctionObject::getHomeObject() const
+{
+    const MemberFunction *m = as<MemberFunction>();
+    if (m)
+        return m->d()->homeObject->asReturnedValue();
+    const ConstructorFunction *c = as<ConstructorFunction>();
+    if (c)
+        return c->d()->homeObject->asReturnedValue();
+    return Encode::undefined();
+}
+
 QQmlSourceLocation FunctionObject::sourceLocation() const
 {
     return d()->function->sourceLocation();
@@ -489,7 +502,9 @@ ReturnedValue ScriptFunction::virtualCallAsConstructor(const FunctionObject *fo,
     return result;
 }
 
-ReturnedValue ScriptFunction::virtualCall(const FunctionObject *fo, const Value *thisObject, const Value *argv, int argc)
+DEFINE_OBJECT_VTABLE(ArrowFunction);
+
+ReturnedValue ArrowFunction::virtualCall(const FunctionObject *fo, const Value *thisObject, const Value *argv, int argc)
 {
     ExecutionEngine *engine = fo->engine();
     CppStackFrame frame;
@@ -508,7 +523,7 @@ ReturnedValue ScriptFunction::virtualCall(const FunctionObject *fo, const Value
     return result;
 }
 
-void Heap::ScriptFunction::initNoConstructor(QV4::ExecutionContext *scope, Function *function, QV4::String *n)
+void Heap::ArrowFunction::init(QV4::ExecutionContext *scope, Function *function, QV4::String *n)
 {
     FunctionObject::init();
     this->scope.set(scope->engine(), scope->d());
@@ -529,9 +544,8 @@ void Heap::ScriptFunction::initNoConstructor(QV4::ExecutionContext *scope, Funct
 
 void Heap::ScriptFunction::init(QV4::ExecutionContext *scope, Function *function)
 {
-    initNoConstructor(scope, function, nullptr);
-    if (function->isArrowFunction())
-        return;
+    ArrowFunction::init(scope, function);
+    Q_ASSERT(!function->isArrowFunction());
 
     Scope s(scope);
     ScopedFunctionObject f(s, this);
diff --git a/src/qml/jsruntime/qv4functionobject_p.h b/src/qml/jsruntime/qv4functionobject_p.h
index 908a9fcb1e..11ddd9a211 100644
--- a/src/qml/jsruntime/qv4functionobject_p.h
+++ b/src/qml/jsruntime/qv4functionobject_p.h
@@ -109,32 +109,42 @@ struct IndexedBuiltinFunction : FunctionObject {
     uint index;
 };
 
+struct ArrowFunction : FunctionObject {
+    enum {
+        Index_Name,
+        Index_Length
+    };
+    void init(QV4::ExecutionContext *scope, Function *function, QV4::String *name = nullptr);
+};
+
 #define ScriptFunctionMembers(class, Member) \
     Member(class, Pointer, InternalClass *, cachedClassForConstructor)
 
-DECLARE_HEAP_OBJECT(ScriptFunction, FunctionObject) {
+DECLARE_HEAP_OBJECT(ScriptFunction, ArrowFunction) {
     DECLARE_MARKOBJECTS(ScriptFunction)
     enum {
         Index_Name,
         Index_Length
     };
-    void initNoConstructor(QV4::ExecutionContext *scope, Function *function, QV4::String *name = nullptr);
     void init(QV4::ExecutionContext *scope, Function *function);
 };
 
 #define MemberFunctionMembers(class, Member) \
     Member(class, Pointer, Object *, homeObject)
 
-DECLARE_HEAP_OBJECT(MemberFunction, ScriptFunction) {
+DECLARE_HEAP_OBJECT(MemberFunction, ArrowFunction) {
     DECLARE_MARKOBJECTS(MemberFunction)
 
     void init(QV4::ExecutionContext *scope, Function *function, QV4::String *name = nullptr) {
-        ScriptFunction::initNoConstructor(scope, function, name);
+        ArrowFunction::init(scope, function, name);
     }
 };
 
-struct ConstructorFunction : MemberFunction
-{
+#define ConstructorFunctionMembers(class, Member) \
+    Member(class, Pointer, Object *, homeObject)
+
+DECLARE_HEAP_OBJECT(ConstructorFunction, ScriptFunction) {
+    DECLARE_MARKOBJECTS(ConstructorFunction)
     bool isDerivedConstructor;
 };
 
@@ -205,6 +215,8 @@ struct Q_QML_EXPORT FunctionObject: Object {
         return d()->isConstructor();
     }
 
+    ReturnedValue getHomeObject() const;
+
     ReturnedValue protoProperty() const { return get(engine()->id_prototype()); }
 
 
@@ -256,25 +268,30 @@ void Heap::IndexedBuiltinFunction::init(QV4::ExecutionContext *scope, uint index
     this->index = index;
 }
 
+struct ArrowFunction : FunctionObject {
+    V4_OBJECT2(ArrowFunction, FunctionObject)
+    V4_INTERNALCLASS(ArrowFunction)
+    enum { NInlineProperties = 3 };
+
+    static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
+};
 
-struct ScriptFunction : FunctionObject {
-    V4_OBJECT2(ScriptFunction, FunctionObject)
+struct ScriptFunction : ArrowFunction {
+    V4_OBJECT2(ScriptFunction, ArrowFunction)
     V4_INTERNALCLASS(ScriptFunction)
-    enum { NInlineProperties = 3 };
 
     static ReturnedValue virtualCallAsConstructor(const FunctionObject *, const Value *argv, int argc, const Value *);
-    static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
 
     Heap::InternalClass *classForConstructor() const;
 };
 
-struct MemberFunction : ScriptFunction {
-    V4_OBJECT2(MemberFunction, ScriptFunction)
+struct MemberFunction : ArrowFunction {
+    V4_OBJECT2(MemberFunction, ArrowFunction)
     V4_INTERNALCLASS(MemberFunction)
 };
 
-struct ConstructorFunction : MemberFunction {
-    V4_OBJECT2(ConstructorFunction, MemberFunction)
+struct ConstructorFunction : ScriptFunction {
+    V4_OBJECT2(ConstructorFunction, ScriptFunction)
     V4_INTERNALCLASS(ConstructorFunction)
     static ReturnedValue virtualCallAsConstructor(const FunctionObject *, const Value *argv, int argc, const Value *);
     static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
diff --git a/src/qml/jsruntime/qv4generatorobject_p.h b/src/qml/jsruntime/qv4generatorobject_p.h
index ad0929987d..366319723d 100644
--- a/src/qml/jsruntime/qv4generatorobject_p.h
+++ b/src/qml/jsruntime/qv4generatorobject_p.h
@@ -72,9 +72,9 @@ struct GeneratorFunctionCtor : FunctionObject {
     void init(QV4::ExecutionContext *scope);
 };
 
-struct GeneratorFunction : ScriptFunction {
+struct GeneratorFunction : ArrowFunction {
     void init(QV4::ExecutionContext *scope, Function *function, QV4::String *name = nullptr) {
-        ScriptFunction::initNoConstructor(scope, function, name);
+        ArrowFunction::init(scope, function, name);
     }
 };
 
@@ -106,13 +106,12 @@ struct GeneratorFunctionCtor : FunctionCtor
     static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
 };
 
-struct GeneratorFunction : ScriptFunction
+struct GeneratorFunction : ArrowFunction
 {
-    V4_OBJECT2(GeneratorFunction, ScriptFunction)
+    V4_OBJECT2(GeneratorFunction, ArrowFunction)
     V4_INTERNALCLASS(GeneratorFunction)
 
     static Heap::FunctionObject *create(ExecutionContext *scope, Function *function);
-    static constexpr VTable::CallAsConstructor virtualCallAsConstructor = nullptr;
     static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
 };
 
@@ -122,7 +121,6 @@ struct MemberGeneratorFunction : MemberFunction
     V4_INTERNALCLASS(MemberGeneratorFunction)
 
     static Heap::FunctionObject *create(ExecutionContext *scope, Function *function, Object *homeObject, String *name);
-    static constexpr VTable::CallAsConstructor virtualCallAsConstructor = nullptr;
     static ReturnedValue virtualCall(const FunctionObject *f, const Value *thisObject, const Value *argv, int argc);
 };
 
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 8f529cea76..0a098ff7ef 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -987,8 +987,8 @@ static Object *getSuperBase(Scope &scope)
     }
 
     ScopedFunctionObject f(scope, scope.engine->currentStackFrame->jsFrame->function);
-    MemberFunction *m = f->as<MemberFunction>();
-    if (!m) {
+    ScopedObject homeObject(scope, f->getHomeObject());
+    if (!homeObject) {
         ScopedContext ctx(scope, static_cast<ExecutionContext *>(&scope.engine->currentStackFrame->jsFrame->context));
         Q_ASSERT(ctx);
         while (ctx) {
@@ -1000,13 +1000,12 @@ static Object *getSuperBase(Scope &scope)
             }
             ctx = ctx->d()->outer;
         }
-        m = f->as<MemberFunction>();
+        homeObject = f->getHomeObject();
     }
-    if (!m) {
+    if (!homeObject) {
         scope.engine->throwTypeError();
         return nullptr;
     }
-    ScopedObject homeObject(scope, m->d()->homeObject);
     Q_ASSERT(homeObject);
     ScopedObject proto(scope, homeObject->getPrototypeOf());
     if (!proto) {