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

src/string.js

Index: src/string.js
===================================================================
--- src/string.js	(revision 4060)
+++ src/string.js	(working copy)
@@ -239,14 +239,29 @@
 }
 
 
+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