Optimize testing for an index's existence in packed Arrays

src/macros.py

Index: src/macros.py
diff --git a/src/macros.py b/src/macros.py
index e8572e660e4e072ed6612944099723c91a566ba6..1571144f9bcef87d5f236d6b4726b703affdce79 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -168,6 +168,7 @@ macro TO_OBJECT_INLINE(arg) = (IS_SPEC_OBJECT(%IS_VAR(arg)) ? arg : ToObject(arg
 macro JSON_NUMBER_TO_STRING(arg) = ((%_IsSmi(%IS_VAR(arg)) || arg - arg == 0) ? %_NumberToString(arg) : "null");
 macro HAS_OWN_PROPERTY(obj, index) = (%_CallFunction(obj, index, ObjectHasOwnProperty));
 macro SHOULD_CREATE_WRAPPER(functionName, receiver) = (!IS_SPEC_OBJECT(receiver) && %IsSloppyModeFunction(functionName));
+macro HAS_INDEX(array, index, is_array) = ((is_array && %_HasFastPackedElements(%IS_VAR(array))) ? (index < array.length) : (index in array));
 
 # Private names.
 # GET_PRIVATE should only be used if the property is known to exists on obj