X64: Fix bug in left-shift.

test/mjsunit/regress/regress-244.js

 // Copyright 2009 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 39 matching lines @@
     var decoded = String.fromCharCode(kLegalPairs[i][0]);
     var encoded = kLegalPairs[i][1];
     assertEquals(decodeURI(encoded), decoded);
     assertEquals(encodeURI(decoded), encoded);
   }
   for (var i = 0; i < kIllegalEncoded.length; i++) {
     var value = kIllegalEncoded[i];
     var threw = false;
     try {
       decodeURI(value);
-      fail(value);
+      assertUnreachable(value);
     } catch (e) {
       assertInstanceof(e, URIError);
     }
   }
 }
 
 run();