--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/shenandoahBrooksPointer.hpp	Mon Dec 10 15:47:44 2018 +0100
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2013, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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_SHENANDOAH_SHENANDOAHBROOKSPOINTER_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHBROOKSPOINTER_HPP
+
+#include "oops/oop.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+class ShenandoahBrooksPointer {
+  /*
+   * Notes:
+   *
+   *  a. It is important to have byte_offset and word_offset return constant
+   *     expressions, because that will allow to constant-fold forwarding ptr
+   *     accesses. This is not a problem in JIT compilers that would generate
+   *     the code once, but it is problematic in GC hotpath code.
+   *
+   *  b. With filler object mechanics, we may need to allocate more space for
+   *     the forwarding ptr to meet alignment requirements for objects. This
+   *     means *_offset and *_size calls are NOT interchangeable. The accesses
+   *     to forwarding ptrs should always be via *_offset. Storage size
+   *     calculations should always be via *_size.
+   */
+
+public:
+  /* Offset from the object start, in HeapWords. */
+  static inline int word_offset() {
+    return -1; // exactly one HeapWord
+  }
+
+  /* Offset from the object start, in bytes. */
+  static inline int byte_offset() {
+    return -HeapWordSize; // exactly one HeapWord
+  }
+
+  /* Allocated size, in HeapWords. */
+  static inline uint word_size() {
+    return (uint) MinObjAlignment;
+  }
+
+  /* Allocated size, in bytes */
+  static inline uint byte_size() {
+    return (uint) MinObjAlignmentInBytes;
+  }
+
+  /* Assert basic stuff once at startup. */
+  static void initial_checks() {
+    guarantee (MinObjAlignment > 0, "sanity, word_size is correct");
+    guarantee (MinObjAlignmentInBytes > 0, "sanity, byte_size is correct");
+  }
+
+  /* Initializes Brooks pointer (to self).
+   */
+  static inline void initialize(oop obj);
+
+  /* Gets forwardee from the given object.
+   */
+  static inline oop forwardee(oop obj);
+
+  /* Tries to atomically update forwardee in $holder object to $update.
+   * Assumes $holder points at itself.
+   * Asserts $holder is in from-space.
+   * Asserts $update is in to-space.
+   */
+  static inline oop try_update_forwardee(oop obj, oop update);
+
+  /* Sets raw value for forwardee slot.
+   * THIS IS DANGEROUS: USERS HAVE TO INITIALIZE/SET FORWARDEE BACK AFTER THEY ARE DONE.
+   */
+  static inline void set_raw(oop obj, HeapWord* update);
+
+  /* Returns the raw value from forwardee slot.
+   */
+  static inline HeapWord* get_raw(oop obj);
+
+  /* Returns the raw value from forwardee slot without any checks.
+   * Used for quick verification.
+   */
+  static inline HeapWord* get_raw_unchecked(oop obj);
+
+private:
+  static inline HeapWord** brooks_ptr_addr(oop obj);
+};
+
+#endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHBROOKSPOINTER_HPP