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diff --git a/Source/JavaScriptCore/b3/air/AirPadInterference.h b/Source/JavaScriptCore/b3/air/AirPadInterference.h
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+++ b/Source/JavaScriptCore/b3/air/AirPadInterference.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)
+
+namespace JSC { namespace B3 { namespace Air {
+
+class Code;
+
+// This isn't a phase - it's meant to be a utility that other phases use. Air reasons about liveness by
+// reasoning about interference at boundaries between instructions. This can go wrong - for example, a
+// late use in one instruction doesn't actually interfere with an early def of the next instruction, but
+// Air thinks that it does. This is convenient because it works great in the most common case: early uses
+// and late defs. In practice, only the register allocators need to use this, since only they need to be
+// able to color the interference graph using a bounded number of colors.
+//
+// See https://bugs.webkit.org/show_bug.cgi?id=163548#c2 for more info.
+
+void padInterference(Code&);
+
+} } } // namespace JSC::B3::Air
+
+#endif // ENABLE(B3_JIT)
+