diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug946284.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug946284.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,5 @@
+function f(x) {
+    return x.length / 2
+}
+f("")
+assertEq(f(undefined + ""), 4.5);