--- /dev/null	2018-11-30 10:10:44.238550338 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahHeapRegionSet.hpp	2018-11-30 10:22:49.228379646 +0100
@@ -0,0 +1,98 @@
+/*
+ * 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_SHENANDOAHHEAPREGIONSET_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAPREGIONSET_HPP
+
+#include "memory/allocation.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+
+class ShenandoahHeapRegionSet;
+
+class ShenandoahHeapRegionSetIterator : public StackObj {
+private:
+  const ShenandoahHeapRegionSet* _set;
+  ShenandoahHeap* const _heap;
+
+  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile jint));
+  volatile jint _current_index;
+  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
+
+  // No implicit copying: iterators should be passed by reference to capture the state
+  ShenandoahHeapRegionSetIterator(const ShenandoahHeapRegionSetIterator& that);
+  ShenandoahHeapRegionSetIterator& operator=(const ShenandoahHeapRegionSetIterator& o);
+
+public:
+  ShenandoahHeapRegionSetIterator(const ShenandoahHeapRegionSet* const set);
+
+  // Reset existing iterator to new set
+  void reset(const ShenandoahHeapRegionSet* const set);
+
+  // MT version
+  ShenandoahHeapRegion* claim_next();
+
+  // Single-thread version
+  ShenandoahHeapRegion* next();
+};
+
+class ShenandoahHeapRegionSet : public CHeapObj<mtGC> {
+  friend class ShenandoahHeap;
+private:
+  ShenandoahHeap* const _heap;
+  size_t const          _map_size;
+  size_t const          _region_size_bytes_shift;
+  jbyte* const          _set_map;
+  // Bias set map's base address for fast test if an oop is in set
+  jbyte* const          _biased_set_map;
+  size_t                _region_count;
+
+public:
+  ShenandoahHeapRegionSet();
+  ~ShenandoahHeapRegionSet();
+
+  // Add region to set
+  void add_region(ShenandoahHeapRegion* r);
+  bool add_region_check_for_duplicates(ShenandoahHeapRegion* r);
+
+  // Remove region from set
+  void remove_region(ShenandoahHeapRegion* r);
+
+  size_t count()  const { return _region_count; }
+  bool is_empty() const { return _region_count == 0; }
+
+  inline bool is_in(ShenandoahHeapRegion* r) const;
+  inline bool is_in(size_t region_number)    const;
+  inline bool is_in(HeapWord* p)             const;
+
+  void print_on(outputStream* out) const;
+
+  void clear();
+
+private:
+  jbyte* biased_map_address() const {
+    return _biased_set_map;
+  }
+};
+
+#endif //SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAPREGIONSET_HPP