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diff --git a/Source/JavaScriptCore/ftl/FTLSlowPathCallKey.h b/Source/JavaScriptCore/ftl/FTLSlowPathCallKey.h
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+++ b/Source/JavaScriptCore/ftl/FTLSlowPathCallKey.h
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+/*
+ * Copyright (C) 2013 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 FTLSlowPathCallKey_h
+#define FTLSlowPathCallKey_h
+
+#if ENABLE(FTL_JIT)
+
+#include "RegisterSet.h"
+
+namespace JSC { namespace FTL {
+
+// This is used for creating some sanity in slow-path calls out of the FTL's inline
+// caches. The idea is that we don't want all of the register save/restore stuff to
+// be generated at each IC site. Instead, the IC slow path call site will just save
+// the registers needed for the arguments. It will arrange for there to be enough
+// space on top of stack to save the remaining registers and the return PC. Then it
+// will call a shared thunk that will save the remaining registers. That thunk needs
+// to know the stack offset at which things get saved along with the call target.
+
+// Note that the offset is *not including* the return PC that would be pushed on X86.
+
+class SlowPathCallKey {
+public:
+    SlowPathCallKey()
+        : m_callTarget(0)
+        , m_offset(0)
+    {
+    }
+    
+    SlowPathCallKey(
+        const RegisterSet& set, void* callTarget, const RegisterSet& argumentRegisters,
+        ptrdiff_t offset)
+        : m_usedRegisters(set)
+        , m_callTarget(callTarget)
+        , m_argumentRegisters(argumentRegisters)
+        , m_offset(offset)
+    {
+    }
+    
+    const RegisterSet& usedRegisters() const { return m_usedRegisters; }
+    void* callTarget() const { return m_callTarget; }
+    const RegisterSet& argumentRegisters() const { return m_argumentRegisters; }
+    ptrdiff_t offset() const { return m_offset; }
+    
+    SlowPathCallKey withCallTarget(void* callTarget)
+    {
+        return SlowPathCallKey(usedRegisters(), callTarget, argumentRegisters(), offset());
+    }
+    
+    void dump(PrintStream&) const;
+    
+    enum EmptyValueTag { EmptyValue };
+    enum DeletedValueTag { DeletedValue };
+    
+    SlowPathCallKey(EmptyValueTag)
+        : m_usedRegisters(RegisterSet::EmptyValue)
+        , m_callTarget(0)
+        , m_offset(0)
+    {
+    }
+    
+    SlowPathCallKey(DeletedValueTag)
+        : m_usedRegisters(RegisterSet::DeletedValue)
+        , m_callTarget(0)
+        , m_offset(0)
+    {
+    }
+    
+    bool isEmptyValue() const { return m_usedRegisters.isEmptyValue(); }
+    bool isDeletedValue() const { return m_usedRegisters.isDeletedValue(); }
+    
+    bool operator==(const SlowPathCallKey& other) const
+    {
+        return m_usedRegisters == other.m_usedRegisters
+            && m_callTarget == other.m_callTarget
+            && m_offset == other.m_offset;
+    }
+    unsigned hash() const
+    {
+        return m_usedRegisters.hash() + PtrHash<void*>::hash(m_callTarget) + m_offset;
+    }
+
+private:
+    RegisterSet m_usedRegisters;
+    void* m_callTarget;
+    RegisterSet m_argumentRegisters;
+    ptrdiff_t m_offset;
+};
+
+struct SlowPathCallKeyHash {
+    static unsigned hash(const SlowPathCallKey& key) { return key.hash(); }
+    static bool equal(const SlowPathCallKey& a, const SlowPathCallKey& b) { return a == b; }
+    static const bool safeToCompareToEmptyOrDeleted = false;
+};
+
+} } // namespace JSC::FTL
+
+namespace WTF {
+
+template<typename T> struct DefaultHash;
+template<> struct DefaultHash<JSC::FTL::SlowPathCallKey> {
+    typedef JSC::FTL::SlowPathCallKeyHash Hash;
+};
+
+template<typename T> struct HashTraits;
+template<> struct HashTraits<JSC::FTL::SlowPathCallKey> : public CustomHashTraits<JSC::FTL::SlowPathCallKey> { };
+
+} // namespace WTF
+
+#endif // ENABLE(FTL_JIT)
+
+#endif // FTLSlowPathCallKey_h
+