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

src/regexp-delay.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 122 matching lines @@
     DoConstructRegExp(this, pattern, flags, false);
   }
 }
 
 
 function DoRegExpExec(regexp, string, index) {
   return %_RegExpExec(regexp, string, index, lastMatchInfo);
 }
 
 
+var regExpExecCacheResult;
+var regExpExecCacheInput;
+var regExpExecCacheId;
+var regExpExecCacheIndex;
+
 function RegExpExec(string) {
   if (!IS_REGEXP(this)) {
     throw MakeTypeError('method_called_on_incompatible',
                         ['RegExp.prototype.exec', this]);
   }
   if (%_ArgumentsLength() == 0) {
-    var regExpInput = LAST_INPUT(lastMatchInfo);
-    if (IS_UNDEFINED(regExpInput)) {
+    string = LAST_INPUT(lastMatchInfo);
+    if (IS_UNDEFINED(string)) {
       throw MakeError('no_input_to_regexp', [this]);
     }
-    string = regExpInput;
   }
+
+  var lastIndex = this.lastIndex;
+  if (%_IsIdentical(regExpExecCacheInput, string) &&
+      %_IsIdentical(regExpExecCacheId, %_RegExpId(this)) &&
+      %_IsIdentical(regExpExecCacheIndex, lastIndex)) {
+    var cachedResult = regExpExecCacheResult;  // Cached result.
+    if (cachedResult) {
+      // If non-null, don't return the same array as last time.
+      var newArray = ArraySlice.call(cachedResult, 0, cachedResult.length);
+      newArray.input = cachedResult.input; 
+      newArray.index = cachedResult.index;
+      cachedResult = newArray;
+    }
+    %_Log("regexp", "regexp-exec-cache-hit", []);
+    return cachedResult;
+  }
+  %_Log("regexp", "regexp-exec-cache-miss", []);
+
+  var i = this.global ? TO_INTEGER(lastIndex) : 0;
   var s = ToString(string);
   var length = s.length;
-  var lastIndex = this.lastIndex;
-  var i = this.global ? TO_INTEGER(lastIndex) : 0;
 
   if (i < 0 || i > s.length) {
     this.lastIndex = 0;
     return null;
   }
 
   %_Log('regexp', 'regexp-exec,%0r,%1S,%2i', [this, s, lastIndex]);
   // matchIndices is either null or the lastMatchInfo array.
   var matchIndices = %_RegExpExec(this, s, i, lastMatchInfo);
 
+  var result;
   if (matchIndices == null) {
     if (this.global) this.lastIndex = 0;
-    return matchIndices; // no match
+    result = matchIndices; // no match
+  } else {
+    var numResults = NUMBER_OF_CAPTURES(lastMatchInfo) >> 1;
+    result = new $Array(numResults);
+    for (var i = 0; i < numResults; i++) {
+      var matchStart = lastMatchInfo[CAPTURE(i << 1)];
+      var matchEnd = lastMatchInfo[CAPTURE((i << 1) + 1)];
+      if (matchStart != -1 && matchEnd != -1) {
+        result[i] = SubString(s, matchStart, matchEnd);
+      } else {
+        // Make sure the element is present. Avoid reading the undefined
+        // property from the global object since this may change.
+        result[i] = void 0;
+      }
+    }
+    if (this.global) this.lastIndex = lastMatchInfo[CAPTURE1];
+    result.index = lastMatchInfo[CAPTURE0];
+    result.input = s;
   }
-
-  var numResults = NUMBER_OF_CAPTURES(lastMatchInfo) >> 1;
-  var result = new $Array(numResults);
-  for (var i = 0; i < numResults; i++) {
-    var matchStart = lastMatchInfo[CAPTURE(i << 1)];
-    var matchEnd = lastMatchInfo[CAPTURE((i << 1) + 1)];
-    if (matchStart != -1 && matchEnd != -1) {
-      result[i] = SubString(s, matchStart, matchEnd);
-    } else {
-      // Make sure the element is present. Avoid reading the undefined
-      // property from the global object since this may change.
-      result[i] = void 0;
-    }
-  }
-
-  if (this.global)
-    this.lastIndex = lastMatchInfo[CAPTURE1];
-  result.index = lastMatchInfo[CAPTURE0];
-  result.input = s;
+  regExpExecCacheResult = result;
+  regExpExecCacheInput = string;
+  regExpExecCacheId = %_RegExpId(this);  // May have changed.
+  regExpExecCacheIndex = lastIndex;
   return result;
 }
 
 
+var regExpTestCacheResult;
+var regExpTestCacheId;
+var regExpTestCacheIndex;
+var regExpTestCacheInput;
+
 // Section 15.10.6.3 doesn't actually make sense, but the intention seems to be
 // that test is defined in terms of String.prototype.exec. However, it probably
 // means the original value of String.prototype.exec, which is what everybody
 // else implements.
 function RegExpTest(string) {
   if (!IS_REGEXP(this)) {
     throw MakeTypeError('method_called_on_incompatible',
                         ['RegExp.prototype.test', this]);
   }
   if (%_ArgumentsLength() == 0) {
-    var regExpInput = LAST_INPUT(lastMatchInfo);
-    if (IS_UNDEFINED(regExpInput)) {
+    string = LAST_INPUT(lastMatchInfo);
+    if (IS_UNDEFINED(string)) {
       throw MakeError('no_input_to_regexp', [this]);
     }
-    string = regExpInput;
   }
+
+  var lastIndex = this.lastIndex;
+  if (%_IsIdentical(regExpTestCacheInput, string) &&
+      %_IsIdentical(regExpTestCacheId, %_RegExpId(this)) &&
+      %_IsIdentical(regExpTestCacheIndex, lastIndex)) {
+    %_Log("regexp", "regexp-test-cache-hit", []);
+    return regExpTestCacheResult;  // Always true or false.
+  }
+  %_Log("regexp", "regexp-test-cache-miss", []);
+
+  var i = this.global ? TO_INTEGER(lastIndex) : 0;
   var s = ToString(string);
   var length = s.length;
-  var lastIndex = this.lastIndex;
-  var i = this.global ? TO_INTEGER(lastIndex) : 0;
 
+  var result;
   if (i < 0 || i > s.length) {
     this.lastIndex = 0;
-    return false;
+    result = false;
+  } else {
+    %_Log('regexp', 'regexp-exec,%0r,%1S,%2i', [this, s, lastIndex]);
+    // matchIndices is either null or the lastMatchInfo array.
+    var matchIndices = %_RegExpExec(this, s, i, lastMatchInfo);
+
+    if (matchIndices == null) {
+      if (this.global) this.lastIndex = 0;
+      result = false;
+    } else {
+    if (this.global) this.lastIndex = lastMatchInfo[CAPTURE1];
+    result = true;
+    }
   }
-
-  %_Log('regexp', 'regexp-exec,%0r,%1S,%2i', [this, s, lastIndex]);
-  // matchIndices is either null or the lastMatchInfo array.
-  var matchIndices = %_RegExpExec(this, s, i, lastMatchInfo);
-
-  if (matchIndices == null) {
-    if (this.global) this.lastIndex = 0;
-    return false;
-  }
-
-  if (this.global) this.lastIndex = lastMatchInfo[CAPTURE1];
-  return true;
+  regExpTestCacheResult = result;
+  regExpTestCacheInput = string;
+  regExpTestCacheId = %_RegExpId(this);
+  regExpTestCacheIndex = lastIndex;
+  return result;
 }
 
 
 function RegExpToString() {
   // If this.source is an empty string, output /(?:)/.
   // http://bugzilla.mozilla.org/show_bug.cgi?id=225550
   // ecma_2/RegExp/properties-001.js.
   var src = this.source ? this.source : '(?:)';
   var result = '/' + src + '/';
   if (this.global)
@@ skipping 90 matching lines @@
     "exec", RegExpExec,
     "test", RegExpTest,
     "toString", RegExpToString,
     "compile", CompileRegExp
   ));
 
   // The length of compile is 1 in SpiderMonkey.
   %FunctionSetLength($RegExp.prototype.compile, 1);
 
   // The properties input, $input, and $_ are aliases for each other.  When this
-  // value is set the value it is set to is coerced to a string. 
+  // value is set the value it is set to is coerced to a string.
   // Getter and setter for the input.
   function RegExpGetInput() {
     var regExpInput = LAST_INPUT(lastMatchInfo);
     return IS_UNDEFINED(regExpInput) ? "" : regExpInput;
   }
   function RegExpSetInput(string) {
     LAST_INPUT(lastMatchInfo) = ToString(string);
   };
 
   %DefineAccessor($RegExp, 'input', GETTER, RegExpGetInput, DONT_DELETE);
@@ skipping 43 matching lines @@
   %DefineAccessor($RegExp, "$'", SETTER, NoOpSetter, DONT_ENUM | DONT_DELETE);
 
   for (var i = 1; i < 10; ++i) {
     %DefineAccessor($RegExp, '$' + i, GETTER, RegExpMakeCaptureGetter(i), DONT_DELETE);
     %DefineAccessor($RegExp, '$' + i, SETTER, NoOpSetter, DONT_DELETE);
   }
 }
 
 
 SetupRegExp();