Cache regular expressions used in String.search.

src/string.js

 // 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 503 matching lines @@
   var parameters = $Array(m + 2);
   for (var j = 0; j < m; j++) {
     parameters[j] = CaptureString(subject, matchInfo, j);
   }
   parameters[j] = index;
   parameters[j + 1] = subject;
   return replace.apply(null, parameters);
 }
 
 
+var re_cache = {}
+
+
 // ECMA-262 section 15.5.4.12
 function StringSearch(re) {
-  var regexp = new $RegExp(re);
+  var regexp = re_cache[re];
+  if (IS_UNDEFINED(regexp)) {

[sandholm, 2010/03/25 05:36:24]

Maybe reset cache at size 10, 100 or 1000 to avoid large memory increase and
longer lookup times. 

+    regexp = new $RegExp(re);
+    re_cache[re] = regexp;
+  }
   var s = TO_STRING_INLINE(this);
   var last_idx = regexp.lastIndex; // keep old lastIndex

[Lasse Reichstein, 2010/03/25 08:05:13]

Use:
  var match = DoRegExpExec(regexp, s, 0);
  if (match) {
    lastMatchInfo = match;
    return match[CAPTURE0];
  }
  return -1;

This avoids building the result of the exec call, it avoids calling exec
(depending on RegExp.prototype.exec not being changed), and it avoids hitting
the regexp exec cache (which may or may not be a good thing).

[Lasse Reichstein, 2010/03/25 08:53:11]

I'll just make a changelist for this on its own.

   regexp.lastIndex = 0;            // ignore re.global property
   var result = regexp.exec(s);
   regexp.lastIndex = last_idx;     // restore lastIndex
   if (result == null)
     return -1;
   else
     return result.index;
 }
 
 
@@ skipping 447 matching lines @@
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup,
     "toJSON", StringToJSON
   ));
 }
 
 
 SetupString();