--- old/src/share/vm/gc/g1/concurrentMark.cpp	2015-10-08 22:15:41.123460305 +0200
+++ new/src/share/vm/gc/g1/concurrentMark.cpp	2015-10-08 22:15:41.068461618 +0200
@@ -58,81 +58,9 @@
 #include "runtime/prefetch.inline.hpp"
 #include "services/memTracker.hpp"
 
-// Concurrent marking bit map wrapper
+void G1CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
 
-CMBitMapRO::CMBitMapRO(int shifter) :
-  _bm(),
-  _shifter(shifter) {
-  _bmStartWord = 0;
-  _bmWordSize = 0;
-}
-
-HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
-                                               const HeapWord* limit) const {
-  // First we must round addr *up* to a possible object boundary.
-  addr = (HeapWord*)align_size_up((intptr_t)addr,
-                                  HeapWordSize << _shifter);
-  size_t addrOffset = heapWordToOffset(addr);
-  if (limit == NULL) {
-    limit = _bmStartWord + _bmWordSize;
-  }
-  size_t limitOffset = heapWordToOffset(limit);
-  size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
-  HeapWord* nextAddr = offsetToHeapWord(nextOffset);
-  assert(nextAddr >= addr, "get_next_one postcondition");
-  assert(nextAddr == limit || isMarked(nextAddr),
-         "get_next_one postcondition");
-  return nextAddr;
-}
-
-HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr,
-                                                 const HeapWord* limit) const {
-  size_t addrOffset = heapWordToOffset(addr);
-  if (limit == NULL) {
-    limit = _bmStartWord + _bmWordSize;
-  }
-  size_t limitOffset = heapWordToOffset(limit);
-  size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
-  HeapWord* nextAddr = offsetToHeapWord(nextOffset);
-  assert(nextAddr >= addr, "get_next_one postcondition");
-  assert(nextAddr == limit || !isMarked(nextAddr),
-         "get_next_one postcondition");
-  return nextAddr;
-}
-
-int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
-  assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
-  return (int) (diff >> _shifter);
-}
-
-#ifndef PRODUCT
-bool CMBitMapRO::covers(MemRegion heap_rs) const {
-  // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
-  assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
-         "size inconsistency");
-  return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
-         _bmWordSize  == heap_rs.word_size();
-}
-#endif
-
-void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
-  _bm.print_on_error(st, prefix);
-}
-
-size_t CMBitMap::compute_size(size_t heap_size) {
-  return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
-}
-
-size_t CMBitMap::mark_distance() {
-  return MinObjAlignmentInBytes * BitsPerByte;
-}
-
-void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
-  _bmStartWord = heap.start();
-  _bmWordSize = heap.word_size();
-
-  _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
-  _bm.set_size(_bmWordSize >> _shifter);
+  CMBitMap::initialize(heap, storage->reserved());
 
   storage->set_mapping_changed_listener(&_listener);
 }
@@ -200,7 +128,7 @@
   }
 };
 
-void CMBitMap::clearAll() {
+void G1CMBitMap::clearAll() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   ClearBitmapHRClosure cl(NULL, this, false /* may_yield */);
   uint n_workers = g1h->workers()->active_workers();
@@ -210,39 +138,6 @@
   return;
 }
 
-void CMBitMap::markRange(MemRegion mr) {
-  mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
-  assert(!mr.is_empty(), "unexpected empty region");
-  assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
-          ((HeapWord *) mr.end())),
-         "markRange memory region end is not card aligned");
-  // convert address range into offset range
-  _bm.at_put_range(heapWordToOffset(mr.start()),
-                   heapWordToOffset(mr.end()), true);
-}
-
-void CMBitMap::clearRange(MemRegion mr) {
-  mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
-  assert(!mr.is_empty(), "unexpected empty region");
-  // convert address range into offset range
-  _bm.at_put_range(heapWordToOffset(mr.start()),
-                   heapWordToOffset(mr.end()), false);
-}
-
-MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
-                                            HeapWord* end_addr) {
-  HeapWord* start = getNextMarkedWordAddress(addr);
-  start = MIN2(start, end_addr);
-  HeapWord* end   = getNextUnmarkedWordAddress(start);
-  end = MIN2(end, end_addr);
-  assert(start <= end, "Consistency check");
-  MemRegion mr(start, end);
-  if (!mr.is_empty()) {
-    clearRange(mr);
-  }
-  return mr;
-}
-
 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
   _base(NULL), _cm(cm)
 #ifdef ASSERT