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diff --git a/Source/JavaScriptCore/dfg/DFGCombinedLiveness.h b/Source/JavaScriptCore/dfg/DFGCombinedLiveness.h
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+/*
+ * Copyright (C) 2015-2016 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. 
+ */
+
+#pragma once
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBlockMap.h"
+#include "DFGGraph.h"
+
+namespace JSC { namespace DFG {
+
+// Returns the set of nodes live at tail, both due to due DFG and due to bytecode (i.e. OSR exit).
+HashSet<Node*> liveNodesAtHead(Graph&, BasicBlock*);
+
+// WARNING: This currently does not reason about the liveness of shadow values. The execution
+// semantics of DFG SSA are that an Upsilon stores to the shadow value of a Phi, and the Phi loads
+// from that shadow value. Hence, the shadow values are like variables, and have liveness. The normal
+// liveness analysis will tell you about the liveness of shadow values. It's OK to ignore shadow
+// values if you treat Upsilon as an opaque escape, and all of the clients of CombinedLiveness do so.
+struct CombinedLiveness {
+    CombinedLiveness() { }
+    
+    CombinedLiveness(Graph&);
+    
+    BlockMap<HashSet<Node*>> liveAtHead;
+    BlockMap<HashSet<Node*>> liveAtTail;
+};
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)