VariableWatchpointSet.h   [plain text]

/*
 * Copyright (C) 2012-2014 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 *    notice, this list of conditions and the following disclaimer in the
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 *
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#ifndef VariableWatchpointSet_h
#define VariableWatchpointSet_h

#include "Watchpoint.h"
#include "WriteBarrier.h"

namespace JSC {

class SymbolTable;

class VariableWatchpointSet : public WatchpointSet {
    friend class LLIntOffsetsExtractor;
public:
    VariableWatchpointSet(SymbolTable& symbolTable)
        : WatchpointSet(ClearWatchpoint)
        , m_symbolTable(symbolTable)
    {
    }
    
    ~VariableWatchpointSet() { }
    
    // For the purpose of deciding whether or not to watch this variable, you only need
    // to inspect inferredValue(). If this returns something other than the empty
    // value, then it means that at all future safepoints, this watchpoint set will be
    // in one of these states:
    //
    //    IsWatched: in this case, the variable's value must still be the
    //        inferredValue.
    //
    //    IsInvalidated: in this case the variable's value may be anything but you'll
    //        either notice that it's invalidated and not install the watchpoint, or
    //        you will have been notified that the watchpoint was fired.
    JSValue inferredValue() const { return m_inferredValue.get(); }
    
    inline void notifyWrite(VM&, JSValue);
    
    void invalidate()
    {
        m_inferredValue.clear();
        WatchpointSet::invalidate();
    }
    
    void finalizeUnconditionally()
    {
        ASSERT(!!m_inferredValue == (state() == IsWatched));
        if (!m_inferredValue)
            return;
        JSValue inferredValue = m_inferredValue.get();
        if (!inferredValue.isCell())
            return;
        JSCell* cell = inferredValue.asCell();
        if (Heap::isMarked(cell))
            return;
        invalidate();
    }

    WriteBarrier<Unknown>* addressOfInferredValue() { return &m_inferredValue; }
    
private:
    SymbolTable& m_symbolTable;
    WriteBarrier<Unknown> m_inferredValue;
};

} // namespace JSC

#endif // VariableWatchpointSet_h