diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug809021.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug809021.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,73 @@
+// nactuals > nformals
+function testOverflow() {
+    var called = false;
+    function f(a) {
+        assertEq(a, 173);
+        assertEq(arguments.length, 2);
+        assertEq(arguments[0], a);
+        assertEq(arguments[1], a);
+        called = true;
+    }
+
+    for (var i=0; i<10; i++)
+        [173, 173, 173].sort(f);
+    assertEq(called, true);
+}
+testOverflow();
+
+// nactuals == nformals
+function testEqual() {
+    var called = false;
+    function f(a, b) {
+        assertEq(a, 173);
+        assertEq(arguments.length, 2);
+        assertEq(arguments[0], a);
+        assertEq(arguments[1], b);
+        called = true;
+    }
+
+    for (var i=0; i<10; i++)
+        [173, 173, 173].sort(f);
+    assertEq(called, true);
+}
+testEqual();
+
+// nactuals < nformals
+function testUnderflow() {
+    var called = false;
+    function f(a, b, c) {
+        assertEq(a, 173);
+        assertEq(c, undefined);
+        assertEq(arguments.length, 2);
+        assertEq(arguments[0], a);
+        assertEq(arguments[1], b);
+        called = true;
+    }
+
+    for (var i=0; i<10; i++)
+        [173, 173, 173].sort(f);
+    assertEq(called, true);
+}
+testUnderflow();
+
+function testUnderflowMany() {
+    var called = 0;
+    function f(a, b, c, d, e, f, g, h) {
+        assertEq(a, 173);
+        assertEq(arguments.length, 3);
+        assertEq(arguments[0], a);
+        assertEq(arguments[1] < 3, true);
+        assertEq(c.length, 3);
+        assertEq(d, undefined);
+        assertEq(e, undefined);
+        assertEq(f, undefined);
+        assertEq(g, undefined);
+        assertEq(h, undefined);
+        called += 1;
+    }
+
+    for (var i=0; i<10; i++)
+        [173, 173, 173].map(f);
+    assertEq(called, 30);
+}
+testUnderflowMany();