--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/accessBarrierSupport.hpp	Mon Nov 20 13:07:44 2017 +0100
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_SHARED_ACCESSBARRIERSUPPORT_HPP
+#define SHARE_VM_GC_SHARED_ACCESSBARRIERSUPPORT_HPP
+
+#include "memory/allocation.hpp"
+#include "oops/access.hpp"
+
+class AccessBarrierSupport: AllStatic {
+private:
+  static DecoratorSet resolve_unknown_oop_ref_strength(DecoratorSet decorators, oop base, ptrdiff_t offset);
+
+public:
+  // Some collectors, like G1, needs to keep referents alive when loading them.
+  // Therefore, for APIs that accept unknown oop ref strength (e.g. unsafe),
+  // we need to dynamically find out if a given field is on a java.lang.ref.Reference object.
+  // and in that case what strength it has.
+  template<DecoratorSet decorators>
+  static DecoratorSet resolve_possibly_unknown_oop_ref_strength(oop base, ptrdiff_t offset);
+};
+
+#endif // SHARE_VM_GC_SHARED_ACCESSBARRIERSUPPORT_HPP