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diff --git a/Source/JavaScriptCore/bytecode/DFGExitProfile.h b/Source/JavaScriptCore/bytecode/DFGExitProfile.h
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+++ b/Source/JavaScriptCore/bytecode/DFGExitProfile.h
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+/*
+ * Copyright (C) 2011, 2012, 2013, 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 DFGExitProfile_h
+#define DFGExitProfile_h
+
+#if ENABLE(DFG_JIT)
+
+#include "ConcurrentJITLock.h"
+#include "ExitKind.h"
+#include "ExitingJITType.h"
+#include <wtf/HashSet.h>
+#include <wtf/Vector.h>
+
+namespace JSC { namespace DFG {
+
+class FrequentExitSite {
+public:
+    FrequentExitSite()
+        : m_bytecodeOffset(0) // 0 = empty value
+        , m_kind(ExitKindUnset)
+        , m_jitType(ExitFromAnything)
+    {
+    }
+    
+    FrequentExitSite(WTF::HashTableDeletedValueType)
+        : m_bytecodeOffset(1) // 1 = deleted value
+        , m_kind(ExitKindUnset)
+        , m_jitType(ExitFromAnything)
+    {
+    }
+    
+    explicit FrequentExitSite(unsigned bytecodeOffset, ExitKind kind, ExitingJITType jitType = ExitFromAnything)
+        : m_bytecodeOffset(bytecodeOffset)
+        , m_kind(kind)
+        , m_jitType(jitType)
+    {
+        if (m_kind == ArgumentsEscaped) {
+            // Count this one globally. It doesn't matter where in the code block the arguments excaped;
+            // the fact that they did is not associated with any particular instruction.
+            m_bytecodeOffset = 0;
+        }
+    }
+    
+    // Use this constructor if you wish for the exit site to be counted globally within its
+    // code block.
+    explicit FrequentExitSite(ExitKind kind, ExitingJITType jitType = ExitFromAnything)
+        : m_bytecodeOffset(0)
+        , m_kind(kind)
+        , m_jitType(jitType)
+    {
+    }
+    
+    bool operator!() const
+    {
+        return m_kind == ExitKindUnset;
+    }
+    
+    bool operator==(const FrequentExitSite& other) const
+    {
+        return m_bytecodeOffset == other.m_bytecodeOffset
+            && m_kind == other.m_kind
+            && m_jitType == other.m_jitType;
+    }
+    
+    bool subsumes(const FrequentExitSite& other) const
+    {
+        if (m_bytecodeOffset != other.m_bytecodeOffset)
+            return false;
+        if (m_kind != other.m_kind)
+            return false;
+        if (m_jitType == ExitFromAnything)
+            return true;
+        return m_jitType == other.m_jitType;
+    }
+    
+    unsigned hash() const
+    {
+        return WTF::intHash(m_bytecodeOffset) + m_kind + m_jitType * 7;
+    }
+    
+    unsigned bytecodeOffset() const { return m_bytecodeOffset; }
+    ExitKind kind() const { return m_kind; }
+    ExitingJITType jitType() const { return m_jitType; }
+    
+    FrequentExitSite withJITType(ExitingJITType jitType) const
+    {
+        FrequentExitSite result = *this;
+        result.m_jitType = jitType;
+        return result;
+    }
+
+    bool isHashTableDeletedValue() const
+    {
+        return m_kind == ExitKindUnset && m_bytecodeOffset;
+    }
+
+private:
+    unsigned m_bytecodeOffset;
+    ExitKind m_kind;
+    ExitingJITType m_jitType;
+};
+
+struct FrequentExitSiteHash {
+    static unsigned hash(const FrequentExitSite& key) { return key.hash(); }
+    static bool equal(const FrequentExitSite& a, const FrequentExitSite& b) { return a == b; }
+    static const bool safeToCompareToEmptyOrDeleted = true;
+};
+
+} } // namespace JSC::DFG
+
+
+namespace WTF {
+
+template<typename T> struct DefaultHash;
+template<> struct DefaultHash<JSC::DFG::FrequentExitSite> {
+    typedef JSC::DFG::FrequentExitSiteHash Hash;
+};
+
+template<typename T> struct HashTraits;
+template<> struct HashTraits<JSC::DFG::FrequentExitSite> : SimpleClassHashTraits<JSC::DFG::FrequentExitSite> { };
+
+} // namespace WTF
+
+namespace JSC { namespace DFG {
+
+class QueryableExitProfile;
+
+class ExitProfile {
+public:
+    ExitProfile();
+    ~ExitProfile();
+    
+    // Add a new frequent exit site. Return true if this is a new one, or false
+    // if we already knew about it. This is an O(n) operation, because it errs
+    // on the side of keeping the data structure compact. Also, this will only
+    // be called a fixed number of times per recompilation. Recompilation is
+    // rare to begin with, and implies doing O(n) operations on the CodeBlock
+    // anyway.
+    bool add(const ConcurrentJITLocker&, const FrequentExitSite&);
+    
+    // Get the frequent exit sites for a bytecode index. This is O(n), and is
+    // meant to only be used from debugging/profiling code.
+    Vector<FrequentExitSite> exitSitesFor(unsigned bytecodeIndex);
+    
+    // This is O(n) and should be called on less-frequently executed code paths
+    // in the compiler. It should be strictly cheaper than building a
+    // QueryableExitProfile, if you really expect this to be called infrequently
+    // and you believe that there are few exit sites.
+    bool hasExitSite(const ConcurrentJITLocker&, const FrequentExitSite&) const;
+    bool hasExitSite(const ConcurrentJITLocker& locker, ExitKind kind) const
+    {
+        return hasExitSite(locker, FrequentExitSite(kind));
+    }
+    bool hasExitSite(const ConcurrentJITLocker& locker, unsigned bytecodeIndex, ExitKind kind) const
+    {
+        return hasExitSite(locker, FrequentExitSite(bytecodeIndex, kind));
+    }
+    
+private:
+    friend class QueryableExitProfile;
+    
+    std::unique_ptr<Vector<FrequentExitSite>> m_frequentExitSites;
+};
+
+class QueryableExitProfile {
+public:
+    QueryableExitProfile();
+    ~QueryableExitProfile();
+    
+    void initialize(const ConcurrentJITLocker&, const ExitProfile&);
+
+    bool hasExitSite(const FrequentExitSite& site) const
+    {
+        if (site.jitType() == ExitFromAnything) {
+            return hasExitSite(site.withJITType(ExitFromDFG))
+                || hasExitSite(site.withJITType(ExitFromFTL));
+        }
+        return m_frequentExitSites.find(site) != m_frequentExitSites.end();
+    }
+    
+    bool hasExitSite(ExitKind kind) const
+    {
+        return hasExitSite(FrequentExitSite(kind));
+    }
+    
+    bool hasExitSite(unsigned bytecodeIndex, ExitKind kind) const
+    {
+        return hasExitSite(FrequentExitSite(bytecodeIndex, kind));
+    }
+private:
+    HashSet<FrequentExitSite> m_frequentExitSites;
+};
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+
+#endif // DFGExitProfile_h