X64: Convert smis to holding 32 bits of payload.

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 100 matching lines @@
 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 are after the captures so we can omit them on
-# results returned from global searches.  Beware - these evaluate their
-# arguments twice.
+# 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;