--- /dev/null	2020-01-17 11:46:19.065201212 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.hpp	2020-01-17 17:10:06.161130697 +0100
@@ -0,0 +1,98 @@
+
+/*
+ * Copyright (c) 2016, 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_SHENANDOAHFREESET_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHFREESET_HPP
+
+#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+
+class ShenandoahFreeSet : public CHeapObj<mtGC> {
+private:
+  ShenandoahHeap* const _heap;
+  CHeapBitMap _mutator_free_bitmap;
+  CHeapBitMap _collector_free_bitmap;
+  size_t _max;
+
+  // Left-most and right-most region indexes. There are no free regions outside
+  // of [left-most; right-most] index intervals
+  size_t _mutator_leftmost, _mutator_rightmost;
+  size_t _collector_leftmost, _collector_rightmost;
+
+  size_t _capacity;
+  size_t _used;
+
+  void assert_bounds() const NOT_DEBUG_RETURN;
+  void assert_heaplock_owned_by_current_thread() const NOT_DEBUG_RETURN;
+  void assert_heaplock_not_owned_by_current_thread() const NOT_DEBUG_RETURN;
+
+  bool is_mutator_free(size_t idx) const;
+  bool is_collector_free(size_t idx) const;
+
+  HeapWord* try_allocate_in(ShenandoahHeapRegion* region, ShenandoahAllocRequest& req, bool& in_new_region);
+  HeapWord* allocate_single(ShenandoahAllocRequest& req, bool& in_new_region);
+  HeapWord* allocate_contiguous(ShenandoahAllocRequest& req);
+
+  void flip_to_gc(ShenandoahHeapRegion* r);
+
+  void recompute_bounds();
+  void adjust_bounds();
+  bool touches_bounds(size_t num) const;
+
+  void increase_used(size_t amount);
+  void clear_internal();
+
+  size_t collector_count() const { return _collector_free_bitmap.count_one_bits(); }
+  size_t mutator_count()   const { return _mutator_free_bitmap.count_one_bits();   }
+
+  void try_recycle_trashed(ShenandoahHeapRegion *r);
+
+  bool is_empty_or_trash(ShenandoahHeapRegion *r);
+  size_t alloc_capacity(ShenandoahHeapRegion *r);
+  bool has_no_alloc_capacity(ShenandoahHeapRegion *r);
+
+public:
+  ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions);
+
+  void clear();
+  void rebuild();
+
+  void recycle_trash();
+
+  void log_status();
+
+  size_t capacity()  const { return _capacity; }
+  size_t used()      const { return _used;     }
+  size_t available() const {
+    assert(_used <= _capacity, "must use less than capacity");
+    return _capacity - _used;
+  }
+
+  HeapWord* allocate(ShenandoahAllocRequest& req, bool& in_new_region);
+  size_t unsafe_peek_free() const;
+
+  void print_on(outputStream* out) const;
+};
+
+#endif //SHARE_VM_GC_SHENANDOAH_SHENANDOAHFREESET_HPP