diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/toid.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/toid.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+function f(arr, index) {
+    for (var i=0; i<100; i++) {
+        arr[index]++;
+        ++arr[index];
+    }
+}
+var arr = [1, 2, 3];
+f(arr, "1");
+f(arr, 1);
+assertEq(arr[1], 402);