--- /dev/null	2020-01-17 11:46:19.065201212 +0100
+++ new/src/hotspot/share/gc/shared/markBitMap.hpp	2020-01-17 17:15:15.675113641 +0100
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2015, 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_VM_GC_SHARED_CMBITMAP_HPP
+#define SHARE_VM_GC_SHARED_CMBITMAP_HPP
+
+#include "memory/memRegion.hpp"
+#include "utilities/bitMap.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+// A generic CM bit map.  This is essentially a wrapper around the BitMap
+// class, with one bit per (1<<_shifter) HeapWords.
+
+class MarkBitMapRO {
+ protected:
+  MemRegion _covered;      // The heap area covered by this bitmap.
+  HeapWord* _bmStartWord;  // base address of range covered by map
+  size_t    _bmWordSize;   // map size (in #HeapWords covered)
+  const int _shifter;      // map to char or bit
+  BitMapView _bm;          // the bit map itself
+
+ public:
+  // constructor
+  MarkBitMapRO(int shifter);
+
+  // inquiries
+  HeapWord* startWord()   const { return _bmStartWord; }
+  // the following is one past the last word in space
+  HeapWord* endWord()     const { return _bmStartWord + _bmWordSize; }
+
+  // read marks
+
+  bool isMarked(HeapWord* addr) const {
+    assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+           "outside underlying space?");
+    return _bm.at(heapWordToOffset(addr));
+  }
+
+  // iteration
+  inline bool iterate(BitMapClosure* cl, MemRegion mr);
+
+  // Return the address corresponding to the next marked bit at or after
+  // "addr", and before "limit", if "limit" is non-NULL.  If there is no
+  // such bit, returns "limit" if that is non-NULL, or else "endWord()".
+  inline HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
+                                     const HeapWord* limit = NULL) const;
+
+  // conversion utilities
+  HeapWord* offsetToHeapWord(size_t offset) const {
+    return _bmStartWord + (offset << _shifter);
+  }
+  size_t heapWordToOffset(const HeapWord* addr) const {
+    return pointer_delta(addr, _bmStartWord) >> _shifter;
+  }
+
+  // The argument addr should be the start address of a valid object
+  inline HeapWord* nextObject(HeapWord* addr);
+
+  void print_on_error(outputStream* st, const char* prefix) const;
+
+  // debugging
+  NOT_PRODUCT(bool covers(MemRegion rs) const;)
+};
+
+class MarkBitMap : public MarkBitMapRO {
+ private:
+  // Clear bitmap range
+  void do_clear(MemRegion mr, bool large);
+
+ public:
+  static size_t compute_size(size_t heap_size);
+  // Returns the amount of bytes on the heap between two marks in the bitmap.
+  static size_t mark_distance();
+  // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
+  // mark bitmap corresponds to. This is the same as the mark distance above.  static size_t heap_map_factor() {
+  static size_t heap_map_factor() {
+    return mark_distance();
+  }
+
+  MarkBitMap() : MarkBitMapRO(LogMinObjAlignment) {}
+
+  // Initializes the underlying BitMap to cover the given area.
+  void initialize(MemRegion heap, MemRegion bitmap);
+
+  // Write marks.
+  inline void mark(HeapWord* addr);
+  inline void clear(HeapWord* addr);
+  inline bool parMark(HeapWord* addr);
+
+  // Clear range. For larger regions, use *_large.
+  void clear()                         { do_clear(_covered, true); }
+  void clear_range(MemRegion mr)       { do_clear(mr, false);      }
+  void clear_range_large(MemRegion mr) { do_clear(mr, true);       }
+};
+
+#endif // SHARE_VM_GC_SHARED_CMBITMAP_HPP