Microoptimization to regexps.

src/regexp.js

 // Copyright 2012 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 122 matching lines @@
   var end = lastMatchInfo[CAPTURE1];
   var result = %_RegExpConstructResult(numResults, start, s);
   if (start + 1 == end) {
     result[0] = %_StringCharAt(s, start);
   } else {
     result[0] = %_SubString(s, start, end);
   }
   var j = REGEXP_FIRST_CAPTURE + 2;
   for (var i = 1; i < numResults; i++) {
     start = lastMatchInfo[j++];
-    end = lastMatchInfo[j++];
-    if (end != -1) {
+    if (start != -1) {
+      end = lastMatchInfo[j];
       if (start + 1 == end) {
         result[i] = %_StringCharAt(s, start);
       } else {
         result[i] = %_SubString(s, start, end);
       }
-    } else {
-      // Make sure the element is present. Avoid reading the undefined
-      // property from the global object since this may change.
-      result[i] = void 0;
     }
+    j++;
   }
   return result;
 }
 
 
 function RegExpExecNoTests(regexp, string, start) {
   // Must be called with RegExp, string and positive integer as arguments.
   var matchInfo = %_RegExpExec(regexp, string, start, lastMatchInfo);
   if (matchInfo !== null) {
     lastMatchInfoOverride = null;
@@ skipping 314 matching lines @@
 
   for (var i = 1; i < 10; ++i) {
     %DefineOrRedefineAccessorProperty($RegExp, '$' + i,
                                       RegExpMakeCaptureGetter(i), NoOpSetter,
                                       DONT_DELETE);
   }
   %ToFastProperties($RegExp);
 }
 
 SetUpRegExp();