--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/gcThreadLocalData.hpp	Thu Apr 12 08:25:56 2018 +0200
@@ -0,0 +1,45 @@
+/*
+ * 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.
+ */
+
+#ifndef SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP
+#define SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP
+
+#include "utilities/globalDefinitions.hpp"
+
+// Thread local data area for GC-specific information. Each GC
+// is free to decide the internal structure and contents of this
+// area. It is represented as a 64-bit aligned opaque blob to
+// avoid circular dependencies between Thread and all GCs. For
+// the same reason, the size of the data area is hard coded to
+// provide enough space for all current GCs. Adjust the size if
+// needed, but avoid making it excessively large as it adds to
+// the memory overhead of creating a thread.
+//
+// Use Thread::gc_data<T>() to access the data, where T is the
+// GC-specific type describing the structure of the data. GCs
+// should consider placing frequently accessed fields first in
+// T, so that field offsets relative to Thread are small, which
+// often allows for a more compact instruction encoding.
+typedef uint64_t GCThreadLocalData[14]; // 112 bytes
+
+#endif // SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP