JavaScriptCore-1097.3.tar.gz

[apple/javascriptcore.git] / bytecode / ExecutionCounter.h

diff --git a/bytecode/ExecutionCounter.h b/bytecode/ExecutionCounter.h
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+/*
+ * Copyright (C) 2012 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 <wtf/SimpleStats.h>
+
+namespace JSC {
+
+class CodeBlock;
+
+class ExecutionCounter {
+public:
+    ExecutionCounter();
+    bool checkIfThresholdCrossedAndSet(CodeBlock*);
+    void setNewThreshold(int32_t threshold, CodeBlock*);
+    void deferIndefinitely();
+    static double applyMemoryUsageHeuristics(int32_t value, CodeBlock*);
+    static int32_t applyMemoryUsageHeuristicsAndConvertToInt(int32_t value, CodeBlock*);
+
+    static int32_t formattedTotalCount(float value)
+    {
+        union {
+            int32_t i;
+            float f;
+        } u;
+        u.f = value;
+        return u.i;
+    }
+    
+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 targetting, without any correction for
+    // the memory usage heuristics.
+    int32_t m_activeThreshold;
+};
+
+} // namespace JSC
+
+#endif // ExecutionCounter_h
+