JavaScriptCore-7600.1.4.9.tar.gz

[apple/javascriptcore.git] / bytecode / VariableWatchpointSet.h

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+/*
+ * Copyright (C) 2012-2014 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 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
+