Add 1-element caches to RegExp.exec and String.replace. We...

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 221 matching lines @@
     ExpandReplacement(replace, subject, reusableMatchInfo, builder);
   }
 
   // suffix
   builder.addSpecialSlice(end, subject.length);
 
   return builder.generate();
 }
 
 
+var cachedReplaceSubject;
+var cachedReplaceRegexp;
+var cachedReplaceReplacement;
+var cachedReplaceAnswer;
+
 // Helper function for regular expressions in String.prototype.replace.
 function StringReplaceRegExp(subject, regexp, replace) {
+  if (replace === cachedReplaceReplacement &&
+      subject === cachedReplaceSubject &&

[Mads Ager (chromium), 2010/03/10 08:12:22]

%_ObjectEquals for these?

[Lasse Reichstein, 2010/03/10 08:53:24]

Test FixedArray of subject.

+      regexp === cachedReplaceRegexp) {
+    return cachedReplaceAnswer;
+  }
   replace = TO_STRING_INLINE(replace);
-  return %StringReplaceRegExpWithString(subject,
-                                        regexp,
-                                        replace,
-                                        lastMatchInfo);
-};
+  var answer = %StringReplaceRegExpWithString(subject,
+                                              regexp,
+                                              replace,
+                                              lastMatchInfo);
+  cachedReplaceSubject = subject;
+  cachedReplaceRegexp = regexp;
+  cachedReplaceReplacement = replace;
+  cachedReplaceAnswer = answer;
+  return answer;
+}
 
 
 // Expand the $-expressions in the string and return a new string with
 // the result.
 function ExpandReplacement(string, subject, matchInfo, builder) {
   var next = %StringIndexOf(string, '$', 0);
   if (next < 0) {
     builder.add(string);
     return;
   }
@@ skipping 640 matching lines @@
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup,
     "toJSON", StringToJSON
   ));
 }
 
 
 SetupString();