Do a fast check for undefined values when comparing.

bleeding_edge/src/runtime.js

 // Copyright 2006-2008 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 104 matching lines @@
 // the result when either (or both) the operands are NaN.
 function COMPARE(x, ncr) {
   // Fast case for numbers and strings.
   if (IS_NUMBER(this) && IS_NUMBER(x)) {
     return %NumberCompare(this, x, ncr);
   }
   if (IS_STRING(this) && IS_STRING(x)) {
     return %StringCompare(this, x);
   }
 
+  // If one of the operands is undefined, it will convert to NaN and
+  // thus the result should be as if one of the operands was NaN.
+  if (IS_UNDEFINED(this) || IS_UNDEFINED(x)) {
+    return ncr;
+  }
+
   // Default implementation.
   var a = %ToPrimitive(this, NUMBER_HINT);
   var b = %ToPrimitive(x, NUMBER_HINT);
   if (IS_STRING(a) && IS_STRING(b)) {
     return %StringCompare(a, b);
   } else {
     var a_number = %ToNumber(a);
     var b_number = %ToNumber(b);
     if (NUMBER_IS_NAN(a_number) || NUMBER_IS_NAN(b_number)) return ncr;
     return %NumberCompare(a_number, b_number, ncr);
@@ skipping 462 matching lines @@
   throw %MakeTypeError('cannot_convert_to_primitive', []);
 }
 
 
 // NOTE: Setting the prototype for Array must take place as early as
 // possible due to code generation for array literals.  When
 // generating code for a array literal a boilerplate array is created
 // that is cloned when running the code.  It is essiential that the
 // boilerplate gets the right prototype.
 %FunctionSetPrototype($Array, new $Array(0));