Avoid calling the builtin String.prototype.split in Intl

src/js/i18n.js

 // Copyright 2013 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.
 
 // ECMAScript 402 API implementation.
 
 /**
  * Intl object is a single object that has some named properties,
  * all of which are constructors.
  */
@@ skipping 23 matching lines @@
 var MakeError;
 var MakeRangeError;
 var MakeTypeError;
 var ObjectHasOwnProperty = utils.ImportNow("ObjectHasOwnProperty");
 var OverrideFunction = utils.OverrideFunction;
 var patternSymbol = utils.ImportNow("intl_pattern_symbol");
 var resolvedSymbol = utils.ImportNow("intl_resolved_symbol");
 var SetFunctionName = utils.SetFunctionName;
 var StringIndexOf;
 var StringLastIndexOf;
-var StringSplit;
 var StringSubstr;
 var StringSubstring;
 
 utils.Import(function(from) {
   ArrayIndexOf = from.ArrayIndexOf;
   ArrayJoin = from.ArrayJoin;
   ArrayPush = from.ArrayPush;
   IsNaN = from.IsNaN;
   MakeError = from.MakeError;
   MakeRangeError = from.MakeRangeError;
   MakeTypeError = from.MakeTypeError;
   InternalRegExpMatch = from.InternalRegExpMatch;
   InternalRegExpReplace = from.InternalRegExpReplace;
   StringIndexOf = from.StringIndexOf;
   StringLastIndexOf = from.StringLastIndexOf;
-  StringSplit = from.StringSplit;
   StringSubstr = from.StringSubstr;
   StringSubstring = from.StringSubstring;
 });
 
 utils.ImportFromExperimental(function(from) {
   FLAG_intl_extra = from.FLAG_intl_extra;
 });
 
 // Utilities for definitions
 
@@ skipping 47 matching lines @@
       this[internalName] = boundMethod;
     }
     return this[internalName];
   });
 
   %FunctionRemovePrototype(getter);
   %DefineGetterPropertyUnchecked(obj.prototype, methodName, getter, DONT_ENUM);
   %SetNativeFlag(getter);
 }
 
+// Special StringSplit function for this file; does not work with RegExps
+// or access Symbol.split, but per spec, is just for strings.
+function StringSplit(separator, limit) {
+  var subject = TO_STRING(this);
+  var separator_string = TO_STRING(separator);
+  limit = (IS_UNDEFINED(limit)) ? kMaxUint32 : TO_UINT32(limit);

[Yang, 2016/07/07 09:13:01]

I don't think StringSplit is used with the optional limit argument at all in
this file.
Also, can we figure out whether TO_STRING is necessary at all? If not, we could
simply call %StringSplit at all call sites, or some form of
%StringSplit(TO_STRING(a), TO_STRING(b), kMaxUint32), instead of using %_Call.

[Dan Ehrenberg, 2016/07/07 18:35:42]

That's true; I don't see a real need to call TO_STRING at all, except as
defensive programming. I initially prototyped it with just calling %StringSplit
all over the place, but I was thinking we might want to limit the number of
callsites to a runtime function and reduce the number of variables changed in
this patch. The new version just calls %StringSplit.

+  return %StringSplit(this, separator, limit);
+}
+
 // -------------------------------------------------------------------
 
 var Intl = {};
 
 %AddNamedProperty(global, "Intl", Intl, DONT_ENUM);
 
 /**
  * Caches available locales for each service.
  */
 var AVAILABLE_LOCALES = {
@@ skipping 2113 matching lines @@
   }
 );
 
 utils.Export(function(to) {
   to.AddBoundMethod = AddBoundMethod;
   to.IntlParseDate = IntlParseDate;
   to.IntlParseNumber = IntlParseNumber;
 });
 
 })