Improve performance of Array.prototype.join and String.prototype.substring...

src/macros.py

 # Copyright 2006-2009 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 79 matching lines @@
 macro IS_BOOLEAN_WRAPPER(arg)   = (%_ClassOf(arg) === 'Boolean');
 macro IS_ERROR(arg)             = (%_ClassOf(arg) === 'Error');
 macro IS_SCRIPT(arg)            = (%_ClassOf(arg) === 'Script');
 macro IS_ARGUMENTS(arg)         = (%_ClassOf(arg) === 'Arguments');
 macro IS_GLOBAL(arg)            = (%_ClassOf(arg) === 'global');
 macro FLOOR(arg)                = $floor(arg);
 
 # Inline macros. Use %IS_VAR to make sure arg is evaluated only once.
 macro NUMBER_IS_NAN(arg) = (!%_IsSmi(%IS_VAR(arg)) && !(arg == arg));
 macro TO_INTEGER(arg)    = (%_IsSmi(%IS_VAR(arg)) ? arg : ToInteger(arg));
-macro TO_INT32(arg)      = (%_IsSmi(%IS_VAR(arg)) ? arg : ToInt32(arg));
+macro TO_INT32(arg)      = (%_IsSmi(%IS_VAR(arg)) ? arg : (arg >> 0));
+macro TO_UINT32(arg)     = (arg >>> 0);
 
 # Macros implemented in Python.
 python macro CHAR_CODE(str) = ord(str[1]);
 
 # Accessors for original global properties that ensure they have been loaded.
 const ORIGINAL_REGEXP = (global.RegExp, $RegExp);
 const ORIGINAL_DATE   = (global.Date, $Date);
 
 # Constants used on an array to implement the properties of the RegExp object.
 const REGEXP_NUMBER_OF_CAPTURES = 0;
 const REGEXP_FIRST_CAPTURE = 3;
 
 # We can't put macros in macros so we use constants here.
 # REGEXP_NUMBER_OF_CAPTURES
 macro NUMBER_OF_CAPTURES(array) = ((array)[0]);
 
 # Gets the value of a Date object. If arg is not a Date object
 # a type error is thrown.
 macro DATE_VALUE(arg) = (%_ClassOf(arg) === 'Date' ? %_ValueOf(arg) : ThrowDateTypeError());
 
 # Last input and last subject of regexp matches.
 macro LAST_SUBJECT(array) = ((array)[1]);
 macro LAST_INPUT(array) = ((array)[2]);
 
 # REGEXP_FIRST_CAPTURE
 macro CAPTURE(index) = (3 + (index));
 const CAPTURE0 = 3;
 const CAPTURE1 = 4;