bytecode/VariableWatchpointSet.h

   1 /*
   2  * Copyright (C) 2012-2014 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef VariableWatchpointSet_h
  27 #define VariableWatchpointSet_h
  28
  29 #include "Watchpoint.h"
  30 #include "WriteBarrier.h"
  31
  32 namespace JSC {
  33
  34 class SymbolTable;
  35
  36 class VariableWatchpointSet : public WatchpointSet {
  37     friend class LLIntOffsetsExtractor;
  38 public:
  39     VariableWatchpointSet(SymbolTable& symbolTable)
  40         : WatchpointSet(ClearWatchpoint)
  41         , m_symbolTable(symbolTable)
  42     {
  43     }
  44
  45     ~VariableWatchpointSet() { }
  46
  47     // For the purpose of deciding whether or not to watch this variable, you only need
  48     // to inspect inferredValue(). If this returns something other than the empty
  49     // value, then it means that at all future safepoints, this watchpoint set will be
  50     // in one of these states:
  51     //
  52     //    IsWatched: in this case, the variable's value must still be the
  53     //        inferredValue.
  54     //
  55     //    IsInvalidated: in this case the variable's value may be anything but you'll
  56     //        either notice that it's invalidated and not install the watchpoint, or
  57     //        you will have been notified that the watchpoint was fired.
  58     JSValue inferredValue() const { return m_inferredValue.get(); }
  59
  60     inline void notifyWrite(VM&, JSValue);
  61
  62     void invalidate()
  63     {
  64         m_inferredValue.clear();
  65         WatchpointSet::invalidate();
  66     }
  67
  68     void finalizeUnconditionally()
  69     {
  70         ASSERT(!!m_inferredValue == (state() == IsWatched));
  71         if (!m_inferredValue)
  72             return;
  73         JSValue inferredValue = m_inferredValue.get();
  74         if (!inferredValue.isCell())
  75             return;
  76         JSCell* cell = inferredValue.asCell();
  77         if (Heap::isMarked(cell))
  78             return;
  79         invalidate();
  80     }
  81
  82     WriteBarrier<Unknown>* addressOfInferredValue() { return &m_inferredValue; }
  83
  84 private:
  85     SymbolTable& m_symbolTable;
  86     WriteBarrier<Unknown> m_inferredValue;
  87 };
  88
  89 } // namespace JSC
  90
  91 #endif // VariableWatchpointSet_h
  92