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diff --git a/Source/JavaScriptCore/dfg/DFGPrePostNumbering.h b/Source/JavaScriptCore/dfg/DFGPrePostNumbering.h
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+++ b/Source/JavaScriptCore/dfg/DFGPrePostNumbering.h
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+/*
+ * Copyright (C) 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 DFGPrePostNumbering_h
+#define DFGPrePostNumbering_h
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlock.h"
+#include "DFGBlockMap.h"
+#include <wtf/FastMalloc.h>
+#include <wtf/Noncopyable.h>
+
+namespace JSC { namespace DFG {
+
+enum EdgeKind {
+    ForwardEdge,
+    CrossEdge,
+    BackEdge
+};
+
+class PrePostNumbering {
+    WTF_MAKE_NONCOPYABLE(PrePostNumbering);
+    WTF_MAKE_FAST_ALLOCATED;
+public:
+    PrePostNumbering(Graph&);
+    ~PrePostNumbering();
+
+    unsigned preNumber(BasicBlock* block) const { return m_map[block].m_preNumber; }
+    unsigned postNumber(BasicBlock* block) const { return m_map[block].m_postNumber; }
+    
+    // Is from a strict ancestor of to?
+    bool isStrictAncestorOf(BasicBlock* from, BasicBlock* to) const
+    {
+        return preNumber(from) < preNumber(to)
+            && postNumber(from) > postNumber(to);
+    }
+    
+    bool isAncestorOf(BasicBlock* from, BasicBlock* to) const
+    {
+        return from == to || isStrictAncestorOf(from, to);
+    }
+    
+    bool isStrictDescendantOf(BasicBlock* from, BasicBlock* to) const
+    {
+        return isStrictAncestorOf(to, from);
+    }
+    
+    bool isDescendantOf(BasicBlock* from, BasicBlock* to) const
+    {
+        return isAncestorOf(to, from);
+    }
+    
+    // This will give a bogus answer if there is actually no such edge. If you want to determine
+    // if there is any such edge, you have to do it yourself.
+    EdgeKind edgeKind(BasicBlock* from, BasicBlock* to) const
+    {
+        if (isStrictDescendantOf(to, from))
+            return ForwardEdge;
+        
+        if (isAncestorOf(to, from))
+            return BackEdge;
+        
+        return CrossEdge;
+    }
+    
+private:
+    struct Numbering {
+        unsigned m_preNumber;
+        unsigned m_postNumber;
+    };
+
+    BlockMap<Numbering> m_map;
+};
+
+} } // namespace JSC::DFG
+
+namespace WTF {
+
+void printInternal(PrintStream&, JSC::DFG::EdgeKind);
+
+} // namespace WTF
+
+#endif // ENABLE(DFG_JIT)
+
+#endif // DFGPrePostNumbering_h
+