[regexp] Don't cache exec method in Regexp.proto[@@split]

src/js/regexp.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 'use strict';
 
 %CheckIsBootstrapping();
 
@@ skipping 326 matching lines @@
   if (!IS_RECEIVER(this)) {
     throw %make_type_error(kIncompatibleMethodReceiver,
                         "RegExp.prototype.@@split", this);
   }
   string = TO_STRING(string);
   var constructor = SpeciesConstructor(this, GlobalRegExp);
   var flags = TO_STRING(this.flags);
 
   // TODO(adamk): this fast path is wrong as we doesn't ensure that 'exec'
   // is actually a data property on RegExp.prototype.
-  var exec;
   if (IS_REGEXP(this) && constructor === GlobalRegExp) {
-    exec = this.exec;
+    var exec = this.exec;
     if (exec === RegExpExecJS) {
       return %_Call(RegExpSplit, this, string, limit);
     }
   }
 
   var unicode = %StringIndexOf(flags, 'u', 0) >= 0;
   var sticky = %StringIndexOf(flags, 'y', 0) >= 0;
   var newFlags = sticky ? flags : flags + "y";
   var splitter = new constructor(this, newFlags);
   var array = new GlobalArray();
   var arrayIndex = 0;
   var lim = (IS_UNDEFINED(limit)) ? kMaxUint32 : TO_UINT32(limit);
   var size = string.length;
   var prevStringIndex = 0;
   if (lim === 0) return array;
   var result;
   if (size === 0) {
     result = RegExpSubclassExec(splitter, string);
     if (IS_NULL(result)) %AddElement(array, 0, string);
     return array;
   }
   var stringIndex = prevStringIndex;
   while (stringIndex < size) {
     splitter.lastIndex = stringIndex;
-    result = RegExpSubclassExec(splitter, string, exec);
-    // Ensure exec will be read again on the next loop through.
-    exec = UNDEFINED;
+    result = RegExpSubclassExec(splitter, string);
     if (IS_NULL(result)) {
       stringIndex += AdvanceStringIndex(string, stringIndex, unicode);
     } else {
       var end = MinSimple(TO_LENGTH(splitter.lastIndex), size);
       if (end === prevStringIndex) {
         stringIndex += AdvanceStringIndex(string, stringIndex, unicode);
       } else {
         %AddElement(
             array, arrayIndex,
             %_SubString(string, prevStringIndex, stringIndex));
@@ skipping 741 matching lines @@
   to.GetSubstitution = GetSubstitution;
   to.InternalRegExpMatch = InternalRegExpMatch;
   to.InternalRegExpReplace = InternalRegExpReplace;
   to.IsRegExp = IsRegExp;
   to.RegExpExec = DoRegExpExec;
   to.RegExpInitialize = RegExpInitialize;
   to.RegExpLastMatchInfo = RegExpLastMatchInfo;
 });
 
 })