Some smaller optimizations for indexed property access

Saves around 1% of instructions on crypto.js

Change-Id: Iccef08b204e6e752d827242baf156efd9a4d58a7
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/qml/jsruntime/qv4lookup.cpp

@@ -118,7 +118,8 @@ ReturnedValue Lookup::lookup(const Object *thisObject, PropertyAttributes *attrs
 
 ReturnedValue Lookup::indexedGetterGeneric(Lookup *l, const Value &object, const Value &index)
 {
-    if (object.isObject() && index.asArrayIndex() < UINT_MAX) {
+    uint idx;
+    if (object.isObject() && index.asArrayIndex(idx)) {
         l->indexedGetter = indexedGetterObjectInt;
         return indexedGetterObjectInt(l, object, index);
     }
@@ -129,11 +130,12 @@ ReturnedValue Lookup::indexedGetterFallback(Lookup *l, const Value &object, cons
 {
     Q_UNUSED(l);
     Scope scope(l->engine);
-    uint idx = index.asArrayIndex();
+    uint idx;
+    bool isInt = index.asArrayIndex(idx);
 
     ScopedObject o(scope, object);
     if (!o) {
-        if (idx < UINT_MAX) {
+        if (isInt) {
             if (const String *str = object.as<String>()) {
                 if (idx >= (uint)str->toQString().length()) {
                     return Encode::undefined();
@@ -153,7 +155,7 @@ ReturnedValue Lookup::indexedGetterFallback(Lookup *l, const Value &object, cons
             return Encode::undefined();
     }
 
-    if (idx < UINT_MAX) {
+    if (isInt) {
         if (o->d()->arrayData && !o->d()->arrayData->attrs) {
             ScopedValue v(scope, Scoped<ArrayData>(scope, o->arrayData())->get(idx));
             if (!v->isEmpty())
@@ -173,14 +175,17 @@ ReturnedValue Lookup::indexedGetterFallback(Lookup *l, const Value &object, cons
 
 ReturnedValue Lookup::indexedGetterObjectInt(Lookup *l, const Value &object, const Value &index)
 {
-    uint idx = index.asArrayIndex();
+    uint idx;
-    if (idx != UINT_MAX) {
+    if (index.asArrayIndex(idx)) {
-        if (Object *o = object.objectValue()) {
+        if (Heap::Base *b = object.heapObject()) {
-            if (o->d()->arrayData && o->d()->arrayData->type == Heap::ArrayData::Simple) {
+            if (b->vtable()->isObject) {
-                Heap::SimpleArrayData *s = o->d()->arrayData.cast<Heap::SimpleArrayData>();
+                Heap::Object *o = static_cast<Heap::Object *>(b);
-                if (idx < s->len)
+                if (o->arrayData && o->arrayData->type == Heap::ArrayData::Simple) {
-                    if (!s->data(idx).isEmpty())
+                    Heap::SimpleArrayData *s = o->arrayData.cast<Heap::SimpleArrayData>();
-                        return s->data(idx).asReturnedValue();
+                    if (idx < s->len)
+                        if (!s->data(idx).isEmpty())
+                            return s->data(idx).asReturnedValue();
+                }
             }
         }
     }
@@ -191,7 +196,8 @@ ReturnedValue Lookup::indexedGetterObjectInt(Lookup *l, const Value &object, con
 void Lookup::indexedSetterGeneric(Lookup *l, const Value &object, const Value &index, const Value &v)
 {
     if (Object *o = object.objectValue()) {
-        if (o->d()->arrayData && o->d()->arrayData->type == Heap::ArrayData::Simple && index.asArrayIndex() < UINT_MAX) {
+        uint idx;
+        if (o->d()->arrayData && o->d()->arrayData->type == Heap::ArrayData::Simple && index.asArrayIndex(idx)) {
             l->indexedSetter = indexedSetterObjectInt;
             indexedSetterObjectInt(l, object, index, v);
             return;
@@ -207,8 +213,8 @@ void Lookup::indexedSetterFallback(Lookup *l, const Value &object, const Value &
     if (scope.engine->hasException)
         return;
 
-    uint idx = index.asArrayIndex();
+    uint idx;
-    if (idx < UINT_MAX) {
+    if (index.asArrayIndex(idx)) {
         if (o->d()->arrayData && o->d()->arrayData->type == Heap::ArrayData::Simple) {
             Heap::SimpleArrayData *s = o->d()->arrayData.cast<Heap::SimpleArrayData>();
             if (idx < s->len) {
@@ -226,14 +232,17 @@ void Lookup::indexedSetterFallback(Lookup *l, const Value &object, const Value &
 
 void Lookup::indexedSetterObjectInt(Lookup *l, const Value &object, const Value &index, const Value &v)
 {
-    uint idx = index.asArrayIndex();
+    uint idx;
-    if (idx != UINT_MAX) {
+    if (index.asArrayIndex(idx)) {
-        if (Object *o = object.objectValue()) {
+        if (Heap::Base *b = object.heapObject()) {
-            if (o->d()->arrayData && o->d()->arrayData->type == Heap::ArrayData::Simple) {
+            if (b->vtable()->isObject) {
-                Heap::SimpleArrayData *s = o->d()->arrayData.cast<Heap::SimpleArrayData>();
+                Heap::Object *o = static_cast<Heap::Object *>(b);
-                if (idx < s->len) {
+                if (o->arrayData && o->arrayData->type == Heap::ArrayData::Simple) {
-                    s->data(idx) = v;
+                    Heap::SimpleArrayData *s = o->arrayData.cast<Heap::SimpleArrayData>();
-                    return;
+                    if (idx < s->len) {
+                        s->data(idx) = v;
+                        return;
+                    }
                 }
             }
         }

src/qml/jsruntime/qv4value_p.h

@@ -453,6 +453,7 @@ public:
     }
 
     inline uint asArrayIndex() const;
+    inline bool asArrayIndex(uint &idx) const;
 #ifndef V4_BOOTSTRAP
     uint asArrayLength(bool *ok) const;
 #endif
@@ -531,6 +532,20 @@ inline uint Value::asArrayIndex() const
         return UINT_MAX;
     return idx;
 }
+
+inline bool Value::asArrayIndex(uint &idx) const
+{
+    if (!isDouble()) {
+        if (isInteger() && int_32() >= 0) {
+            idx = (uint)int_32();
+            return true;
+        }
+        return false;
+    }
+    double d = doubleValue();
+    idx = (uint)d;
+    return (idx == d);
+}
 #endif
 
 inline