source: webkit/trunk/JavaScriptCore/runtime/StringObjectThatMasqueradesAsUndefined.h@ 47620

Last change on this file since 47620 was 47267, checked in by [email protected], 16 years ago

Devirtualise marking
https://bugs.webkit.org/show_bug.cgi?id=28294

Reviewed by Maciej Stachowiak.

Add a bit to TypeInfo to indicate that an object uses the standard
JSObject::markChildren method. This allows us to devirtualise marking
of most objects (though a branch is still needed). We also add a branch
to identify arrays thus devirtualising marking in that case as well.

In order to make the best use of this devirtualisation I've also reworked
the MarkStack::drain() logic to make the iteration more efficient.

  • Property svn:eol-style set to native
File size: 2.0 KB
Line 
1/*
2 * Copyright (C) 1999-2000 Harri Porten ([email protected])
3 * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 */
20
21#ifndef StringObjectThatMasqueradesAsUndefined_h
22#define StringObjectThatMasqueradesAsUndefined_h
23
24#include "JSGlobalObject.h"
25#include "StringObject.h"
26#include "UString.h"
27
28namespace JSC {
29
30 // WebCore uses this to make style.filter undetectable
31 class StringObjectThatMasqueradesAsUndefined : public StringObject {
32 public:
33 static StringObjectThatMasqueradesAsUndefined* create(ExecState* exec, const UString& string)
34 {
35 return new (exec) StringObjectThatMasqueradesAsUndefined(exec,
36 createStructure(exec->lexicalGlobalObject()->stringPrototype()), string);
37 }
38
39 private:
40 StringObjectThatMasqueradesAsUndefined(ExecState* exec, PassRefPtr<Structure> structure, const UString& string)
41 : StringObject(exec, structure, string)
42 {
43 }
44
45 static PassRefPtr<Structure> createStructure(JSValue proto)
46 {
47 return Structure::create(proto, TypeInfo(ObjectType, MasqueradesAsUndefined | HasDefaultMark));
48 }
49
50 virtual bool toBoolean(ExecState*) const { return false; }
51 };
52
53} // namespace JSC
54
55#endif // StringObjectThatMasqueradesAsUndefined_h
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