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diff --git a/Source/JavaScriptCore/bytecode/Watchpoint.h b/Source/JavaScriptCore/bytecode/Watchpoint.h
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+/*
+ * Copyright (C) 2012-2015 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 Watchpoint_h
+#define Watchpoint_h
+
+#include <wtf/Atomics.h>
+#include <wtf/FastMalloc.h>
+#include <wtf/Noncopyable.h>
+#include <wtf/PrintStream.h>
+#include <wtf/SentinelLinkedList.h>
+#include <wtf/ThreadSafeRefCounted.h>
+
+namespace JSC {
+
+class FireDetail {
+    void* operator new(size_t) = delete;
+    
+public:
+    FireDetail()
+    {
+    }
+    
+    virtual ~FireDetail()
+    {
+    }
+    
+    virtual void dump(PrintStream&) const = 0;
+};
+
+class StringFireDetail : public FireDetail {
+public:
+    StringFireDetail(const char* string)
+        : m_string(string)
+    {
+    }
+    
+    virtual void dump(PrintStream& out) const override;
+
+private:
+    const char* m_string;
+};
+
+class WatchpointSet;
+
+class Watchpoint : public BasicRawSentinelNode<Watchpoint> {
+    WTF_MAKE_NONCOPYABLE(Watchpoint);
+    WTF_MAKE_FAST_ALLOCATED;
+public:
+    Watchpoint()
+    {
+    }
+    
+    virtual ~Watchpoint();
+
+protected:
+    virtual void fireInternal(const FireDetail&) = 0;
+
+private:
+    friend class WatchpointSet;
+    void fire(const FireDetail&);
+};
+
+enum WatchpointState {
+    ClearWatchpoint,
+    IsWatched,
+    IsInvalidated
+};
+
+class InlineWatchpointSet;
+
+class WatchpointSet : public ThreadSafeRefCounted<WatchpointSet> {
+    friend class LLIntOffsetsExtractor;
+public:
+    JS_EXPORT_PRIVATE WatchpointSet(WatchpointState);
+    JS_EXPORT_PRIVATE ~WatchpointSet(); // Note that this will not fire any of the watchpoints; if you need to know when a WatchpointSet dies then you need a separate mechanism for this.
+    
+    // Fast way of getting the state, which only works from the main thread.
+    WatchpointState stateOnJSThread() const
+    {
+        return static_cast<WatchpointState>(m_state);
+    }
+    
+    // It is safe to call this from another thread. It may return an old
+    // state. Guarantees that if *first* read the state() of the thing being
+    // watched and it returned IsWatched and *second* you actually read its
+    // value then it's safe to assume that if the state being watched changes
+    // then also the watchpoint state() will change to IsInvalidated.
+    WatchpointState state() const
+    {
+        WTF::loadLoadFence();
+        WatchpointState result = static_cast<WatchpointState>(m_state);
+        WTF::loadLoadFence();
+        return result;
+    }
+    
+    // It is safe to call this from another thread.  It may return true
+    // even if the set actually had been invalidated, but that ought to happen
+    // only in the case of races, and should be rare. Guarantees that if you
+    // call this after observing something that must imply that the set is
+    // invalidated, then you will see this return false. This is ensured by
+    // issuing a load-load fence prior to querying the state.
+    bool isStillValid() const
+    {
+        return state() != IsInvalidated;
+    }
+    // Like isStillValid(), may be called from another thread.
+    bool hasBeenInvalidated() const { return !isStillValid(); }
+    
+    // As a convenience, this will ignore 0. That's because code paths in the DFG
+    // that create speculation watchpoints may choose to bail out if speculation
+    // had already been terminated.
+    void add(Watchpoint*);
+    
+    // Force the watchpoint set to behave as if it was being watched even if no
+    // watchpoints have been installed. This will result in invalidation if the
+    // watchpoint would have fired. That's a pretty good indication that you
+    // probably don't want to set watchpoints, since we typically don't want to
+    // set watchpoints that we believe will actually be fired.
+    void startWatching()
+    {
+        ASSERT(m_state != IsInvalidated);
+        if (m_state == IsWatched)
+            return;
+        WTF::storeStoreFence();
+        m_state = IsWatched;
+        WTF::storeStoreFence();
+    }
+    
+    void fireAll(const FireDetail& detail)
+    {
+        if (LIKELY(m_state != IsWatched))
+            return;
+        fireAllSlow(detail);
+    }
+    
+    void fireAll(const char* reason)
+    {
+        if (LIKELY(m_state != IsWatched))
+            return;
+        fireAllSlow(reason);
+    }
+    
+    void touch(const FireDetail& detail)
+    {
+        if (state() == ClearWatchpoint)
+            startWatching();
+        else
+            fireAll(detail);
+    }
+    
+    void touch(const char* reason)
+    {
+        touch(StringFireDetail(reason));
+    }
+    
+    void invalidate(const FireDetail& detail)
+    {
+        if (state() == IsWatched)
+            fireAll(detail);
+        m_state = IsInvalidated;
+    }
+    
+    void invalidate(const char* reason)
+    {
+        invalidate(StringFireDetail(reason));
+    }
+    
+    bool isBeingWatched() const
+    {
+        return m_setIsNotEmpty;
+    }
+    
+    int8_t* addressOfState() { return &m_state; }
+    int8_t* addressOfSetIsNotEmpty() { return &m_setIsNotEmpty; }
+    
+    JS_EXPORT_PRIVATE void fireAllSlow(const FireDetail&); // Call only if you've checked isWatched.
+    JS_EXPORT_PRIVATE void fireAllSlow(const char* reason); // Ditto.
+    
+private:
+    void fireAllWatchpoints(const FireDetail&);
+    
+    friend class InlineWatchpointSet;
+
+    int8_t m_state;
+    int8_t m_setIsNotEmpty;
+
+    SentinelLinkedList<Watchpoint, BasicRawSentinelNode<Watchpoint>> m_set;
+};
+
+// InlineWatchpointSet is a low-overhead, non-copyable watchpoint set in which
+// it is not possible to quickly query whether it is being watched in a single
+// branch. There is a fairly simple tradeoff between WatchpointSet and
+// InlineWatchpointSet:
+//
+// Do you have to emit JIT code that rapidly tests whether the watchpoint set
+// is being watched?  If so, use WatchpointSet.
+//
+// Do you need multiple parties to have pointers to the same WatchpointSet?
+// If so, use WatchpointSet.
+//
+// Do you have to allocate a lot of watchpoint sets?  If so, use
+// InlineWatchpointSet unless you answered "yes" to the previous questions.
+//
+// InlineWatchpointSet will use just one pointer-width word of memory unless
+// you actually add watchpoints to it, in which case it internally inflates
+// to a pointer to a WatchpointSet, and transfers its state to the
+// WatchpointSet.
+
+class InlineWatchpointSet {
+    WTF_MAKE_NONCOPYABLE(InlineWatchpointSet);
+public:
+    InlineWatchpointSet(WatchpointState state)
+        : m_data(encodeState(state))
+    {
+    }
+    
+    ~InlineWatchpointSet()
+    {
+        if (isThin())
+            return;
+        freeFat();
+    }
+    
+    // Fast way of getting the state, which only works from the main thread.
+    WatchpointState stateOnJSThread() const
+    {
+        uintptr_t data = m_data;
+        if (isFat(data))
+            return fat(data)->stateOnJSThread();
+        return decodeState(data);
+    }
+
+    // It is safe to call this from another thread. It may return a prior state,
+    // but that should be fine since you should only perform actions based on the
+    // state if you also add a watchpoint.
+    WatchpointState state() const
+    {
+        WTF::loadLoadFence();
+        uintptr_t data = m_data;
+        WTF::loadLoadFence();
+        if (isFat(data))
+            return fat(data)->state();
+        return decodeState(data);
+    }
+    
+    // It is safe to call this from another thread.  It may return false
+    // even if the set actually had been invalidated, but that ought to happen
+    // only in the case of races, and should be rare.
+    bool hasBeenInvalidated() const
+    {
+        return state() == IsInvalidated;
+    }
+    
+    // Like hasBeenInvalidated(), may be called from another thread.
+    bool isStillValid() const
+    {
+        return !hasBeenInvalidated();
+    }
+    
+    void add(Watchpoint*);
+    
+    void startWatching()
+    {
+        if (isFat()) {
+            fat()->startWatching();
+            return;
+        }
+        ASSERT(decodeState(m_data) != IsInvalidated);
+        m_data = encodeState(IsWatched);
+    }
+    
+    void fireAll(const FireDetail& detail)
+    {
+        if (isFat()) {
+            fat()->fireAll(detail);
+            return;
+        }
+        if (decodeState(m_data) == ClearWatchpoint)
+            return;
+        m_data = encodeState(IsInvalidated);
+        WTF::storeStoreFence();
+    }
+    
+    void invalidate(const FireDetail& detail)
+    {
+        if (isFat())
+            fat()->invalidate(detail);
+        else
+            m_data = encodeState(IsInvalidated);
+    }
+    
+    JS_EXPORT_PRIVATE void fireAll(const char* reason);
+    
+    void touch(const FireDetail& detail)
+    {
+        if (isFat()) {
+            fat()->touch(detail);
+            return;
+        }
+        uintptr_t data = m_data;
+        if (decodeState(data) == IsInvalidated)
+            return;
+        WTF::storeStoreFence();
+        if (decodeState(data) == ClearWatchpoint)
+            m_data = encodeState(IsWatched);
+        else
+            m_data = encodeState(IsInvalidated);
+        WTF::storeStoreFence();
+    }
+    
+    void touch(const char* reason)
+    {
+        touch(StringFireDetail(reason));
+    }
+    
+    bool isBeingWatched() const
+    {
+        if (isFat())
+            return fat()->isBeingWatched();
+        return false;
+    }
+    
+private:
+    static const uintptr_t IsThinFlag        = 1;
+    static const uintptr_t StateMask         = 6;
+    static const uintptr_t StateShift        = 1;
+    
+    static bool isThin(uintptr_t data) { return data & IsThinFlag; }
+    static bool isFat(uintptr_t data) { return !isThin(data); }
+    
+    static WatchpointState decodeState(uintptr_t data)
+    {
+        ASSERT(isThin(data));
+        return static_cast<WatchpointState>((data & StateMask) >> StateShift);
+    }
+    
+    static uintptr_t encodeState(WatchpointState state)
+    {
+        return (static_cast<uintptr_t>(state) << StateShift) | IsThinFlag;
+    }
+    
+    bool isThin() const { return isThin(m_data); }
+    bool isFat() const { return isFat(m_data); };
+    
+    static WatchpointSet* fat(uintptr_t data)
+    {
+        return bitwise_cast<WatchpointSet*>(data);
+    }
+    
+    WatchpointSet* fat()
+    {
+        ASSERT(isFat());
+        return fat(m_data);
+    }
+    
+    const WatchpointSet* fat() const
+    {
+        ASSERT(isFat());
+        return fat(m_data);
+    }
+    
+    WatchpointSet* inflate()
+    {
+        if (LIKELY(isFat()))
+            return fat();
+        return inflateSlow();
+    }
+    
+    JS_EXPORT_PRIVATE WatchpointSet* inflateSlow();
+    JS_EXPORT_PRIVATE void freeFat();
+    
+    uintptr_t m_data;
+};
+
+} // namespace JSC
+
+#endif // Watchpoint_h
+