--- /dev/null	2018-04-03 12:55:20.301839954 +0200
+++ new/src/hotspot/share/gc/z/zForwardingTable.cpp	2018-06-01 22:30:31.309479445 +0200
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2015, 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.
+ */
+
+#include "precompiled.hpp"
+#include "gc/z/zForwardingTable.inline.hpp"
+#include "gc/z/zUtils.inline.hpp"
+#include "memory/allocation.inline.hpp"
+#include "utilities/debug.hpp"
+
+void ZForwardingTable::setup(size_t live_objects) {
+  assert(is_null(), "Should be empty");
+  assert(live_objects > 0, "Invalid size");
+
+  // Allocate table for linear probing. The size of the table must be
+  // a power of two to allow for quick and inexpensive indexing/masking.
+  // The table is sized to have a load factor of 50%, i.e. sized to have
+  // double the number of entries actuallly inserted.
+  _size = ZUtils::round_up_power_of_2(live_objects * 2);
+  _table = MallocArrayAllocator<ZForwardingTableEntry>::allocate(_size, mtGC);
+
+  // Clear table
+  memset(_table, ZForwardingTableEntry::empty(), _size * sizeof(ZForwardingTableEntry));
+}
+
+void ZForwardingTable::reset() {
+  // Free table
+  MallocArrayAllocator<ZForwardingTableEntry>::free(_table);
+  _table = NULL;
+  _size = 0;
+}
+
+void ZForwardingTable::verify(size_t object_max_count, size_t live_objects) const {
+  size_t count = 0;
+
+  for (size_t i = 0; i < _size; i++) {
+    const ZForwardingTableEntry entry = _table[i];
+    if (entry.is_empty()) {
+      // Skip empty entries
+      continue;
+    }
+
+    // Check from index
+    guarantee(entry.from_index() < object_max_count, "Invalid from index");
+
+    // Check for duplicates
+    for (size_t j = i + 1; j < _size; j++) {
+      const ZForwardingTableEntry other = _table[j];
+      guarantee(entry.from_index() != other.from_index(), "Duplicate from");
+      guarantee(entry.to_offset() != other.to_offset(), "Duplicate to");
+    }
+
+    count++;
+  }
+
+  // Check number of non-null entries
+  guarantee(live_objects == count, "Count mismatch");
+}