Use GetProperty for getting elements.

test/mjsunit/regress/regress-581.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 17 matching lines @@
 var pow30 = Math.pow(2, 30);
 var pow31 = Math.pow(2, 31);
 
 var a = [];
 a[pow31] = 31;
 
 assertEquals(pow31 + 1, a.length);
 assertThrows(function() { a.concat(a); }, RangeError);
 
 var b = [];
-b[pow31 - 2] = 32;
+b[pow31 - 3] = 32;
+b[pow31 - 2] = "out_of_bounds";
 var ab = a.concat(b);
 assertEquals(2 * pow31 - 1, ab.length);
 assertEquals(31, ab[pow31]);
-assertEquals(32, ab[2 * pow31 - 1]);
+assertEquals(32, ab[2 * pow31 - 2]);
+assertEquals(undefined, ab[2 * pow31 - 1]);
 
 var c = [];
 c[pow30] = 30;
 assertThrows(function() { c.concat(c, a); }, RangeError);