diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/arguments/access-formals.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/arguments/access-formals.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,44 @@
+function g1(x, args) {
+    args[0] = 88;
+}
+
+// We assume we can optimize arguments access in |f|.
+//
+// Then the apply-call invalidates the arguments optimization,
+// and creates a real arguments object.
+//
+// Test that x and y fetch the values from the args object when
+// that happens.
+function f1(x, y, o) {
+    var res = 0;
+    for (var i=0; i<50; i++) {
+	res += x + y;
+	if (i > 10)
+	    o.apply(null, arguments);
+    }
+    return res;
+}
+
+var o1 = {apply: g1};
+assertEq(f1(3, 5, o1), 3630);
+assertEq(f1(3, 5, o1), 3630);
+
+// In strict mode, the arguments object does not alias formals.
+function g2(x, args) {
+    args[0] = 88;
+}
+
+function f2(x, y, o) {
+    "use strict";
+    var res = 0;
+    for (var i=0; i<50; i++) {
+	res += x + y;
+	if (i > 10)
+	    o.apply(null, arguments);
+    }
+    return res;
+}
+
+var o2 = {apply: g2};
+assertEq(f2(3, 5, o2), 400);
+assertEq(f2(3, 5, o2), 400);