ES7: Detect Tail Position Calls and pass that to the runtime

Doing the tail call in the runtime will come in a follow-up patch

Change-Id: I8224aac0edbdc765ee9b97703948edd52fd33f3e
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 16 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 7b1a38ff06..470629bd1f 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -1061,8 +1061,6 @@ ReturnedValue Runtime::method_loadSuperConstructor(ExecutionEngine *engine, cons
     return c->asReturnedValue();
 }
 
-
-
 #endif // V4_BOOTSTRAP
 
 uint RuntimeHelpers::equalHelper(const Value &x, const Value &y)
@@ -1538,6 +1536,15 @@ ReturnedValue Runtime::method_constructWithSpread(ExecutionEngine *engine, const
     return static_cast<const FunctionObject &>(function).callAsConstructor(arguments.argv, arguments.argc, &newTarget);
 }
 
+ReturnedValue Runtime::method_tailCall(ExecutionEngine *engine, const Value &function, const Value &thisObject, Value *argv, int argc)
+{
+    //### unwinding the stack, etc, is done in a subsequent patch
+    if (!function.isFunctionObject())
+        return engine->throwTypeError();
+
+    return static_cast<const FunctionObject &>(function).call(&thisObject, argv, argc);
+}
+
 void Runtime::method_throwException(ExecutionEngine *engine, const Value &value)
 {
     if (!value.isEmpty())
diff --git a/src/qml/jsruntime/qv4runtimeapi_p.h b/src/qml/jsruntime/qv4runtimeapi_p.h
index 34b04929af..826b371c1d 100644
--- a/src/qml/jsruntime/qv4runtimeapi_p.h
+++ b/src/qml/jsruntime/qv4runtimeapi_p.h
@@ -101,6 +101,7 @@ struct ExceptionCheck<void (*)(QV4::NoThrowEngine *, A, B, C)> {
     F(ReturnedValue, callWithReceiver, (ExecutionEngine *engine, const Value &func, const Value *thisObject, Value *argv, int argc)) \
     F(ReturnedValue, callPossiblyDirectEval, (ExecutionEngine *engine, Value *argv, int argc)) \
     F(ReturnedValue, callWithSpread, (ExecutionEngine *engine, const Value &func, const Value &thisObject, Value *argv, int argc)) \
+    F(ReturnedValue, tailCall, (ExecutionEngine *engine, const Value &func, const Value &thisObject, Value *argv, int argc)) \
     \
     /* construct */ \
     F(ReturnedValue, construct, (ExecutionEngine *engine, const Value &func, const Value &newTarget, Value *argv, int argc)) \
diff --git a/src/qml/jsruntime/qv4vme_moth.cpp b/src/qml/jsruntime/qv4vme_moth.cpp
index f81c8438ce..7fd7be8e38 100644
--- a/src/qml/jsruntime/qv4vme_moth.cpp
+++ b/src/qml/jsruntime/qv4vme_moth.cpp
@@ -776,6 +776,12 @@ QV4::ReturnedValue VME::interpret(CppStackFrame *frame, ExecutionEngine *engine,
         CHECK_EXCEPTION;
     MOTH_END_INSTR(CallWithSpread)
 
+    MOTH_BEGIN_INSTR(TailCall)
+        STORE_IP();
+        acc = Runtime::method_tailCall(engine, STACK_VALUE(func), STACK_VALUE(thisObject), stack + argv, argc);
+        CHECK_EXCEPTION;
+    MOTH_END_INSTR(TailCall)
+
     MOTH_BEGIN_INSTR(Construct)
         STORE_IP();
         acc = Runtime::method_construct(engine, STACK_VALUE(func), ACC, stack + argv, argc);