Optimize Arguments Object

Avoid creation of the Array in most cases. Fix FunctionObject::method_apply
so that it correctly recognizes this case and does the right thing.
Add a getLength() method to ArgumentsObject to speed up the lookup of that
property.

Improves the RayTrace benchmark by around 15%.

Change-Id: I53eb34a1f9515e59a191ee6f0eb23a3f4c6882d1
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 18 insertions, 3 deletions

diff --git a/src/qml/jsruntime/qv4argumentsobject.cpp b/src/qml/jsruntime/qv4argumentsobject.cpp
index 74fcd30632..5a190d6690 100644
--- a/src/qml/jsruntime/qv4argumentsobject.cpp
+++ b/src/qml/jsruntime/qv4argumentsobject.cpp
@@ -57,8 +57,6 @@ void Heap::ArgumentsObject::init(QV4::CallContext *context)
     Scope scope(v4);
     Scoped<QV4::ArgumentsObject> args(scope, this);
 
-    args->setArrayType(Heap::ArrayData::Complex);
-
     if (context->d()->strictMode) {
         Q_ASSERT(CalleePropertyIndex == args->internalClass()->find(context->d()->engine->id_callee()));
         Q_ASSERT(CallerPropertyIndex == args->internalClass()->find(context->d()->engine->id_caller()));
@@ -246,3 +244,11 @@ void ArgumentsObject::markObjects(Heap::Base *that, ExecutionEngine *e)
 
     Object::markObjects(that, e);
 }
+
+uint ArgumentsObject::getLength(const Managed *m)
+{
+    const ArgumentsObject *a = static_cast<const ArgumentsObject *>(m);
+    if (a->propertyData(Heap::ArgumentsObject::LengthPropertyIndex)->isInteger())
+        return a->propertyData(Heap::ArgumentsObject::LengthPropertyIndex)->integerValue();
+    return Primitive::toUInt32(a->propertyData(Heap::ArgumentsObject::LengthPropertyIndex)->doubleValue());
+}
diff --git a/src/qml/jsruntime/qv4argumentsobject_p.h b/src/qml/jsruntime/qv4argumentsobject_p.h
index 37a8d0a94a..0a2ea3b42a 100644
--- a/src/qml/jsruntime/qv4argumentsobject_p.h
+++ b/src/qml/jsruntime/qv4argumentsobject_p.h
@@ -132,8 +132,10 @@ struct ArgumentsObject: Object {
     static bool deleteIndexedProperty(Managed *m, uint index);
     static PropertyAttributes queryIndexed(const Managed *m, uint index);
     static void markObjects(Heap::Base *that, ExecutionEngine *e);
+    static uint getLength(const Managed *m);
 
     void fullyCreate();
+
 };
 
 }
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 18365e1ce6..2da05f6217 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -47,6 +47,7 @@
 
 #include "qv4arrayobject_p.h"
 #include "qv4scopedvalue_p.h"
+#include "qv4argumentsobject_p.h"
 
 #include <private/qqmljsengine_p.h>
 #include <private/qqmljslexer_p.h>
@@ -301,7 +302,13 @@ ReturnedValue FunctionPrototype::method_apply(CallContext *ctx)
     ScopedCallData callData(scope, len);
 
     if (len) {
-        if (arr->arrayType() == Heap::ArrayData::Simple && !arr->protoHasArray()) {
+        if (ArgumentsObject::isNonStrictArgumentsObject(arr) && !arr->cast<ArgumentsObject>()->fullyCreated()) {
+            QV4::ArgumentsObject *a = arr->cast<ArgumentsObject>();
+            int l = qMin(len, (uint)a->d()->context->callData->argc);
+            memcpy(callData->args, a->d()->context->callData->args, l*sizeof(Value));
+            for (quint32 i = l; i < len; ++i)
+                callData->args[i] = Primitive::undefinedValue();
+        } else if (arr->arrayType() == Heap::ArrayData::Simple && !arr->protoHasArray()) {
             auto sad = static_cast<Heap::SimpleArrayData *>(arr->arrayData());
             uint alen = sad ? sad->len : 0;
             if (alen > len)