1/*
2 * Copyright (C) 2012 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. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef ExecutionCounter_h
27#define ExecutionCounter_h
28
29#include "JSGlobalObject.h"
30#include "Options.h"
31#include <wtf/PrintStream.h>
32#include <wtf/SimpleStats.h>
33
34namespace JSC {
35
36class CodeBlock;
37
38class ExecutionCounter {
39public:
40    ExecutionCounter();
41    bool checkIfThresholdCrossedAndSet(CodeBlock*);
42    void setNewThreshold(int32_t threshold, CodeBlock*);
43    void deferIndefinitely();
44    double count() const { return static_cast<double>(m_totalCount) + m_counter; }
45    void dump(PrintStream&) const;
46    static double applyMemoryUsageHeuristics(int32_t value, CodeBlock*);
47    static int32_t applyMemoryUsageHeuristicsAndConvertToInt(int32_t value, CodeBlock*);
48    template<typename T>
49    static T clippedThreshold(JSGlobalObject* globalObject, T threshold)
50    {
51        int32_t maxThreshold;
52        if (Options::randomizeExecutionCountsBetweenCheckpoints())
53            maxThreshold = globalObject->weakRandomInteger() % Options::maximumExecutionCountsBetweenCheckpoints();
54        else
55            maxThreshold = Options::maximumExecutionCountsBetweenCheckpoints();
56        if (threshold > maxThreshold)
57            threshold = maxThreshold;
58        return threshold;
59    }
60
61    static int32_t formattedTotalCount(float value)
62    {
63        union {
64            int32_t i;
65            float f;
66        } u;
67        u.f = value;
68        return u.i;
69    }
70
71private:
72    bool hasCrossedThreshold(CodeBlock*) const;
73    bool setThreshold(CodeBlock*);
74    void reset();
75
76public:
77
78    // NB. These are intentionally public because it will be modified from machine code.
79
80    // This counter is incremented by the JIT or LLInt. It starts out negative and is
81    // counted up until it becomes non-negative. At the start of a counting period,
82    // the threshold we wish to reach is m_totalCount + m_counter, in the sense that
83    // we will add X to m_totalCount and subtract X from m_counter.
84    int32_t m_counter;
85
86    // Counts the total number of executions we have seen plus the ones we've set a
87    // threshold for in m_counter. Because m_counter's threshold is negative, the
88    // total number of actual executions can always be computed as m_totalCount +
89    // m_counter.
90    float m_totalCount;
91
92    // This is the threshold we were originally targetting, without any correction for
93    // the memory usage heuristics.
94    int32_t m_activeThreshold;
95};
96
97} // namespace JSC
98
99#endif // ExecutionCounter_h
100
101