--- /dev/null	2018-04-03 12:55:20.301839954 +0200
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZBarrier.java	2018-06-06 00:42:34.353446469 +0200
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 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.
+ *
+ */
+
+package sun.jvm.hotspot.gc.z;
+
+import sun.jvm.hotspot.debugger.Address;
+import sun.jvm.hotspot.runtime.VM;
+
+class ZBarrier {
+    private static boolean is_weak_good_or_null_fast_path(Address addr) {
+        return ZAddress.is_weak_good_or_null(addr);
+    }
+
+    private static Address weak_load_barrier_on_oop_slow_path(Address addr) {
+        return ZAddress.is_weak_good(addr) ? ZAddress.good(addr) : relocate_or_remap(addr);
+    }
+
+    private static boolean during_relocate() {
+        return ZGlobals.ZGlobalPhase() == ZGlobals.ZPhaseRelocate;
+    }
+
+    private static Address relocate(Address addr) {
+        ZHeap heap = zheap();
+        if (heap.is_relocating(addr)) {
+            // Forward
+            return heap.relocate_object(addr);
+        }
+
+        // Remap
+        return ZAddress.good(addr);
+    }
+
+    private static ZHeap zheap() {
+        ZCollectedHeap zCollectedHeap = (ZCollectedHeap)VM.getVM().getUniverse().heap();
+        return zCollectedHeap.heap();
+    }
+
+    private static Address remap(Address addr) {
+        ZHeap heap = zheap();
+        if (heap.is_relocating(addr)) {
+            // Forward
+            return heap.forward_object(addr);
+        }
+
+        // Remap
+        return ZAddress.good(addr);
+    }
+
+    private static Address relocate_or_remap(Address addr) {
+        return during_relocate() ? relocate(addr) : remap(addr);
+    }
+
+    static Address weak_barrier(Address o) {
+        // Fast path
+        if (is_weak_good_or_null_fast_path(o)) {
+            // Return the good address instead of the weak good address
+            // to ensure that the currently active heap view is used.
+            return ZAddress.good_or_null(o);
+        }
+
+        // Slow path
+        return weak_load_barrier_on_oop_slow_path(o);
+    }
+}