bytecode/ExecutionCounter.h

   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
  34 namespace JSC {
  35
  36 class CodeBlock;
  37
  38 class ExecutionCounter {
  39 public:
  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
  71 private:
  72     bool hasCrossedThreshold(CodeBlock*) const;
  73     bool setThreshold(CodeBlock*);
  74     void reset();
  75
  76 public:
  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