diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug851064.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug851064.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,13 @@
+var base = "azertyuiopqsdfghjklmwxcvbn";
+function createRopedString() {
+  var test = "";
+  for (var i=0; i<2; i++) {
+    test += base;
+  }
+  return test;
+}
+
+assertEq(createRopedString().substr(0,10), base.substr(0,10));
+assertEq(createRopedString().substr(0,26), base.substr(0,26));
+assertEq(createRopedString().substr(26,10), base.substr(0,10));
+assertEq(createRopedString().substr(24,10), base.substr(24,2) + base.substr(0,8));