diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug855514.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug855514.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+var b = 1.5;
+var arr;
+function f_int(arr, index) {
+    for (var i=0; i<100; i++) {
+        arr[index]++;
+    }
+}
+arr = [1, 2, 3];
+f_int(arr, "1");
+assertEq(arr[1], 102);
+arr = [1, 2, 3];
+f_int(arr, 1);
+assertEq(arr[1], 102);
+
+function f_double(arr, index) {
+    for (var i=0; i<100; i++) {
+        arr[+Math.pow(index,1.0)*1.5/b]++;
+    }
+}
+arr = [1, 2, 3];
+f_double(arr, 1.0);
+assertEq(arr[1], 102);
+arr = [1, 2, 3];
+f_double(arr, NaN);
+assertEq(arr[1], 2);