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diff --git a/Source/JavaScriptCore/b3/air/AirEmitShuffle.h b/Source/JavaScriptCore/b3/air/AirEmitShuffle.h
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+/*
+ * Copyright (C) 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(B3_JIT)
+
+#include "AirArg.h"
+#include "AirInst.h"
+#include <wtf/Vector.h>
+
+namespace JSC { namespace B3 {
+
+class Value;
+
+namespace Air {
+
+class Code;
+
+class ShufflePair {
+public:
+    ShufflePair()
+    {
+    }
+    
+    ShufflePair(const Arg& src, const Arg& dst, Arg::Width width)
+        : m_src(src)
+        , m_dst(dst)
+        , m_width(width)
+    {
+    }
+
+    const Arg& src() const { return m_src; }
+    const Arg& dst() const { return m_dst; }
+
+    // The width determines the kind of move we do. You can only choose Width32 or Width64 right now.
+    // For GP, it picks between Move32 and Move. For FP, it picks between MoveFloat and MoveDouble.
+    Arg::Width width() const { return m_width; }
+
+    void dump(PrintStream&) const;
+    
+private:
+    Arg m_src;
+    Arg m_dst;
+    Arg::Width m_width { Arg::Width8 };
+};
+
+// Create a Shuffle instruction.
+Inst createShuffle(Value* origin, const Vector<ShufflePair>&);
+
+// Perform a shuffle of a given type. The scratch argument is mandatory. You should pass it as
+// follows: If you know that you have scratch registers or temporaries available - that is, they're
+// registers that are not mentioned in the shuffle, have the same type as the shuffle, and are not
+// live at the shuffle - then you can pass them. If you don't have scratch registers available or if
+// you don't feel like looking for them, you can pass memory locations. It's always safe to pass a
+// pair of memory locations, and replacing either memory location with a register can be viewed as an
+// optimization. It's a pretty important optimization. Some more notes:
+//
+// - We define scratch registers as things that are not live before the shuffle and are not one of
+//   the destinations of the shuffle. Not being live before the shuffle also means that they cannot
+//   be used for any of the sources of the shuffle.
+//
+// - A second scratch location is only needed when you have shuffle pairs where memory is used both
+//   as source and destination.
+//
+// - You're guaranteed not to need any scratch locations if there is a Swap instruction available for
+//   the type and you don't have any memory locations that are both the source and the destination of
+//   some pairs. GP supports Swap on x86 while FP never supports Swap.
+//
+// - Passing memory locations as scratch if are running emitShuffle() before register allocation is
+//   silly, since that will cause emitShuffle() to pick some specific registers when it does need
+//   scratch. One easy way to avoid that predicament is to ensure that you call emitShuffle() after
+//   register allocation. For this reason we could add a Shuffle instruction so that we can defer
+//   shufflings until after regalloc.
+//
+// - Shuffles with memory=>memory pairs are not very well tuned. You should avoid them if you want
+//   performance. If you need to do them, then making sure that you reserve a temporary is one way to
+//   get acceptable performance.
+//
+// NOTE: Use this method (and its friend below) to emit shuffles after register allocation. Before
+// register allocation it is much better to simply use the Shuffle instruction.
+Vector<Inst> emitShuffle(
+    Code& code, Vector<ShufflePair>, std::array<Arg, 2> scratch, Arg::Type, Value* origin);
+
+// Perform a shuffle that involves any number of types. Pass scratch registers or memory locations
+// for each type according to the rules above.
+Vector<Inst> emitShuffle(
+    Code& code, const Vector<ShufflePair>&,
+    const std::array<Arg, 2>& gpScratch, const std::array<Arg, 2>& fpScratch,
+    Value* origin);
+
+} } } // namespace JSC::B3::Air
+
+#endif // ENABLE(B3_JIT)