Using array index hash code for string-to-number conversion.

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 484 matching lines @@
   if (IS_STRING(x)) return x.length != 0;
   if (x == null) return false;
   if (IS_NUMBER(x)) return !((x == 0) || NUMBER_IS_NAN(x));
   return true;
 }
 
 
 // ECMA-262, section 9.3, page 31.
 function ToNumber(x) {
   if (IS_NUMBER(x)) return x;
-  if (IS_STRING(x)) return %StringToNumber(x);
+  if (IS_STRING(x)) {
+    return %_HasCachedArrayIndex(x) ? %_GetCachedArrayIndex(x)
+                                    : %StringToNumber(x);
+  }
   if (IS_BOOLEAN(x)) return x ? 1 : 0;
   if (IS_UNDEFINED(x)) return $NaN;
   return (IS_NULL(x)) ? 0 : ToNumber(%DefaultNumber(x));
 }
 
 
 // ECMA-262, section 9.8, page 35.
 function ToString(x) {
   if (IS_STRING(x)) return x;
   if (IS_NUMBER(x)) return %_NumberToString(x);
@@ skipping 104 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));