1/*
2 * Copyright (C) 2011 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef WriteBarrierSupport_h
27#define WriteBarrierSupport_h
28
29#include "SamplingCounter.h"
30#include <wtf/Assertions.h>
31
32namespace JSC {
33
34// This allows the JIT to distinguish between uses of the barrier for different
35// kinds of writes. This is used by the JIT for profiling, and may be appropriate
36// for allowing the GC implementation to specialize the JIT's write barrier code
37// for different kinds of target objects.
38enum WriteBarrierUseKind {
39    // This allows specialization for access to the property storage (either
40    // array element or property), but not for any other kind of property
41    // accesses (such as writes that are a consequence of setter execution).
42    WriteBarrierForPropertyAccess,
43
44    // This allows specialization for variable accesses (such as global or
45    // scoped variables).
46    WriteBarrierForVariableAccess,
47
48    // This captures all other forms of write barriers. It should always be
49    // correct to use a generic access write barrier, even when storing to
50    // properties. Hence, if optimization is not necessary, it is preferable
51    // to just use a generic access.
52    WriteBarrierForGenericAccess
53};
54
55class WriteBarrierCounters {
56private:
57    WriteBarrierCounters() { }
58
59public:
60#if ENABLE(WRITE_BARRIER_PROFILING)
61    static GlobalSamplingCounter usesWithBarrierFromCpp;
62    static GlobalSamplingCounter usesWithoutBarrierFromCpp;
63    static GlobalSamplingCounter usesWithBarrierFromJit;
64    static GlobalSamplingCounter usesForPropertiesFromJit;
65    static GlobalSamplingCounter usesForVariablesFromJit;
66    static GlobalSamplingCounter usesWithoutBarrierFromJit;
67
68    static void initialize();
69
70    static GlobalSamplingCounter& jitCounterFor(WriteBarrierUseKind useKind)
71    {
72        switch (useKind) {
73        case WriteBarrierForPropertyAccess:
74            return usesForPropertiesFromJit;
75        case WriteBarrierForVariableAccess:
76            return usesForVariablesFromJit;
77        default:
78            ASSERT(useKind == WriteBarrierForGenericAccess);
79            return usesWithBarrierFromJit;
80        }
81    }
82#else
83    // These are necessary to work around not having conditional exports.
84    JS_EXPORTDATA static char usesWithBarrierFromCpp;
85    JS_EXPORTDATA static char usesWithoutBarrierFromCpp;
86#endif // ENABLE(WRITE_BARRIER_PROFILING)
87
88    static void countWriteBarrier()
89    {
90#if ENABLE(WRITE_BARRIER_PROFILING)
91        WriteBarrierCounters::usesWithBarrierFromCpp.count();
92#endif
93    }
94};
95
96} // namespace JSC
97
98#endif // WriteBarrierSupport_h
99
100