--- /dev/null	2018-03-12 09:19:30.040007636 +0100
+++ new/src/hotspot/share/oops/compressedOops.inline.hpp	2018-03-22 16:37:51.080885238 +0100
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2017, 2018, 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_OOPS_COMPRESSEDOOPS_INLINE_HPP
+#define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP
+
+#include "gc/shared/collectedHeap.hpp"
+#include "memory/universe.hpp"
+#include "oops/oop.hpp"
+
+// Functions for encoding and decoding compressed oops.
+// If the oops are compressed, the type passed to these overloaded functions
+// is narrowOop.  All functions are overloaded so they can be called by
+// template functions without conditionals (the compiler instantiates via
+// the right type and inlines the appropriate code).
+
+// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
+// offset from the heap base.  Saving the check for null can save instructions
+// in inner GC loops so these are separated.
+
+namespace CompressedOops {
+  inline bool is_null(oop obj)       { return obj == NULL; }
+  inline bool is_null(narrowOop obj) { return obj == 0; }
+
+  inline oop decode_not_null(narrowOop v) {
+    assert(!is_null(v), "narrow oop value can never be zero");
+    address base = Universe::narrow_oop_base();
+    int    shift = Universe::narrow_oop_shift();
+    oop result = (oop)(void*)((uintptr_t)base + ((uintptr_t)v << shift));
+    assert(check_obj_alignment(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));
+    return result;
+  }
+
+  inline oop decode(narrowOop v) {
+    return is_null(v) ? (oop)NULL : decode_not_null(v);
+  }
+
+  inline narrowOop encode_not_null(oop v) {
+    assert(!is_null(v), "oop value can never be zero");
+    assert(check_obj_alignment(v), "Address not aligned");
+    assert(Universe::heap()->is_in_reserved(v), "Address not in heap");
+    address base = Universe::narrow_oop_base();
+    int    shift = Universe::narrow_oop_shift();
+    uint64_t  pd = (uint64_t)(pointer_delta((void*)v, (void*)base, 1));
+    assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
+    uint64_t result = pd >> shift;
+    assert((result & CONST64(0xffffffff00000000)) == 0, "narrow oop overflow");
+    assert(decode(result) == v, "reversibility");
+    return (narrowOop)result;
+  }
+
+  inline narrowOop encode(oop v) {
+    return is_null(v) ? (narrowOop)0 : encode_not_null(v);
+  }
+
+  // No conversions needed for these overloads
+  inline oop decode_not_null(oop v)             { return v; }
+  inline oop decode(oop v)                      { return v; }
+  inline narrowOop encode_not_null(narrowOop v) { return v; }
+  inline narrowOop encode(narrowOop v)          { return v; }
+}
+
+#endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP