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diff --git a/Source/JavaScriptCore/bytecode/ExecutionCounter.h b/Source/JavaScriptCore/bytecode/ExecutionCounter.h
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+/*
+ * Copyright (C) 2012, 2014 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#ifndef ExecutionCounter_h
+#define ExecutionCounter_h
+
+#include "JSGlobalObject.h"
+#include "Options.h"
+#include <wtf/PrintStream.h>
+#include <wtf/SimpleStats.h>
+
+namespace JSC {
+
+class CodeBlock;
+
+enum CountingVariant {
+    CountingForBaseline,
+    CountingForUpperTiers
+};
+
+double applyMemoryUsageHeuristics(int32_t value, CodeBlock*);
+int32_t applyMemoryUsageHeuristicsAndConvertToInt(int32_t value, CodeBlock*);
+
+inline int32_t formattedTotalExecutionCount(float value)
+{
+    union {
+        int32_t i;
+        float f;
+    } u;
+    u.f = value;
+    return u.i;
+}
+    
+template<CountingVariant countingVariant>
+class ExecutionCounter {
+public:
+    ExecutionCounter();
+    void forceSlowPathConcurrently(); // If you use this, checkIfThresholdCrossedAndSet() may still return false.
+    bool checkIfThresholdCrossedAndSet(CodeBlock*);
+    void setNewThreshold(int32_t threshold, CodeBlock*);
+    void deferIndefinitely();
+    double count() const { return static_cast<double>(m_totalCount) + m_counter; }
+    void dump(PrintStream&) const;
+    
+    static int32_t maximumExecutionCountsBetweenCheckpoints()
+    {
+        switch (countingVariant) {
+        case CountingForBaseline:
+            return Options::maximumExecutionCountsBetweenCheckpointsForBaseline();
+        case CountingForUpperTiers:
+            return Options::maximumExecutionCountsBetweenCheckpointsForUpperTiers();
+        default:
+            RELEASE_ASSERT_NOT_REACHED();
+            return 0;
+        }
+    }
+    
+    template<typename T>
+    static T clippedThreshold(JSGlobalObject* globalObject, T threshold)
+    {
+        int32_t maxThreshold;
+        if (Options::randomizeExecutionCountsBetweenCheckpoints())
+            maxThreshold = globalObject->weakRandomInteger() % maximumExecutionCountsBetweenCheckpoints();
+        else
+            maxThreshold = maximumExecutionCountsBetweenCheckpoints();
+        if (threshold > maxThreshold)
+            threshold = maxThreshold;
+        return threshold;
+    }
+
+private:
+    bool hasCrossedThreshold(CodeBlock*) const;
+    bool setThreshold(CodeBlock*);
+    void reset();
+
+public:
+    // NB. These are intentionally public because it will be modified from machine code.
+    
+    // This counter is incremented by the JIT or LLInt. It starts out negative and is
+    // counted up until it becomes non-negative. At the start of a counting period,
+    // the threshold we wish to reach is m_totalCount + m_counter, in the sense that
+    // we will add X to m_totalCount and subtract X from m_counter.
+    int32_t m_counter;
+
+    // Counts the total number of executions we have seen plus the ones we've set a
+    // threshold for in m_counter. Because m_counter's threshold is negative, the
+    // total number of actual executions can always be computed as m_totalCount +
+    // m_counter.
+    float m_totalCount;
+
+    // This is the threshold we were originally targeting, without any correction for
+    // the memory usage heuristics.
+    int32_t m_activeThreshold;
+};
+
+typedef ExecutionCounter<CountingForBaseline> BaselineExecutionCounter;
+typedef ExecutionCounter<CountingForUpperTiers> UpperTierExecutionCounter;
+
+} // namespace JSC
+
+#endif // ExecutionCounter_h
+