Proof-of-concept RegExp-cache for exec, test, replace.

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 144 matching lines @@
 // do anything locale specific.
 function StringLocaleCompare(other) {
   if (%_ArgumentsLength() === 0) return 0;
 
   var this_str = TO_STRING_INLINE(this);
   var other_str = TO_STRING_INLINE(other);
   return %StringLocaleCompare(this_str, other_str);
 }
 
 
+var stringMatchCacheInput;
+var stringMatchCacheId;
+var stringMatchCacheResult;
+
 // ECMA-262 section 15.5.4.10
 function StringMatch(regexp) {
   if (!IS_REGEXP(regexp)) regexp = new ORIGINAL_REGEXP(regexp);
   var subject = TO_STRING_INLINE(this);
 
-  if (!regexp.global) return regexp.exec(subject);
+  if (!regexp.global) return RegExpExec.call(regexp, subject);
   %_Log('regexp', 'regexp-match,%0S,%1r', [subject, regexp]);
+  
+  var reid = %_RegExpId(regexp);
+  if (%_IsIdentical(reid, stringMatchCacheId) &&
+      %_IsIdentical(this, stringMatchCacheInput)) {
+    %_Log("regexp", "regexp-match-cache-hit", []);
+    var cachedResult = stringMatchCacheResult;
+    if (cachedResult) {
+      cachedResult = ArraySlice.call(cachedResult, 0, cachedResult.length);
+    }
+    return cachedResult;
+  }
+  %_Log("regexp", "regexp-match-cache-miss", []);
+  
   // lastMatchInfo is defined in regexp-delay.js.
-  return %StringMatch(subject, regexp, lastMatchInfo);
+  var result = %StringMatch(subject, regexp, lastMatchInfo);
+  stringMatchCacheInput = this;
+  stringMatchCacheId = reid;
+  stringMatchCacheResult = result;
+  return result;
 }
 
 
 // SubString is an internal function that returns the sub string of 'string'.
 // If resulting string is of length 1, we use the one character cache
 // otherwise we call the runtime system.
 function SubString(string, start, end) {
   // Use the one character string cache.
   if (start + 1 == end) {
     var char_code = %_FastCharCodeAt(string, start);
@@ skipping 48 matching lines @@
     ExpandReplacement(replace, subject, reusableMatchInfo, builder);
   }
 
   // suffix
   builder.addSpecialSlice(end, subject.length);
 
   return builder.generate();
 }
 
 
+var stringReplaceRegExpCacheInput;
+var stringReplaceRegExpCacheId;
+var stringReplaceRegExpCacheIndex;
+var stringReplaceRegExpCacheReplace;
+var stringReplaceRegExpCacheResult;
 // Helper function for regular expressions in String.prototype.replace.
 function StringReplaceRegExp(subject, regexp, replace) {
+  if (%_IsIdentical(%_RegExpId(regexp), stringReplaceRegExpCacheId) &&
+      %_IsIdentical(subject, stringReplaceRegExpCacheInput) &&
+      %_IsIdentical(replace, stringReplaceRegExpCacheReplace) &&
+      (!regexp.global || 
+        %_IsIdentical(regexp.lastIndex, stringReplaceRegExpCacheIndex))) {
+    %_Log("regexp", "regexp-replace-cache-hit", []);
+    return stringReplaceRegExpCacheResult;
+  }
+  %_Log("regexp", "regexp-replace-cache-miss", []);
+  stringReplaceRegExpCacheId = %_RegExpId(regexp);
+  stringReplaceRegExpCacheInput = subject;
+  stringReplaceRegExpCacheIndex = regexp.lastIndex;
+  stringReplaceRegExpCacheReplace = replace;
   replace = TO_STRING_INLINE(replace);
-  return %StringReplaceRegExpWithString(subject,
-                                        regexp,
-                                        replace,
-                                        lastMatchInfo);
+  var result = %StringReplaceRegExpWithString(subject,
+                                              regexp,
+                                              replace,
+                                              lastMatchInfo);
+  stringReplaceRegExpCacheResult = result;
+  return result;
 };
 
 
 // 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 645 matching lines @@
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup,
     "toJSON", StringToJSON
   ));
 }
 
 
 SetupString();