--- old/src/hotspot/share/gc/g1/g1RegionToSpaceMapper.cpp	2020-05-03 15:31:17.845998168 +0200
+++ new/src/hotspot/share/gc/g1/g1RegionToSpaceMapper.cpp	2020-05-03 15:31:17.609996998 +0200
@@ -110,8 +110,9 @@
 
   bool is_page_committed(size_t page_idx) {
     size_t region = page_idx * _regions_per_page;
-    // At least one bit must be set if the page is committed.
-    return _region_commit_map.count_one_bits(region, region + _regions_per_page) > 0;
+    size_t region_limit = region + _regions_per_page;
+    // Committed if there is a bit set in the range.
+    return _region_commit_map.get_next_one_offset(region, region_limit) != region_limit;
   }
 
   void numa_request_on_node(size_t page_idx) {
@@ -137,8 +138,9 @@
   }
 
   virtual void commit_regions(uint start_idx, size_t num_regions, WorkGang* pretouch_gang) {
-    assert(_region_commit_map.count_one_bits(start_idx, start_idx + num_regions) == 0,
-           "Should be no commited regions in the range [%u, " SIZE_FORMAT ")",
+    assert(num_regions > 0, "Must commit at least one region");
+    assert(_region_commit_map.get_next_one_offset(start_idx, start_idx + num_regions) == start_idx + num_regions,
+           "Should be no committed regions in the range [%u, " SIZE_FORMAT ")",
            start_idx, start_idx + num_regions);
 
     size_t const NoPage = ~(size_t)0;
@@ -182,8 +184,9 @@
   }
 
   virtual void uncommit_regions(uint start_idx, size_t num_regions) {
-    assert(_region_commit_map.count_one_bits(start_idx, start_idx + num_regions) == num_regions,
-           "Should only be commited regions in the range [%u, " SIZE_FORMAT ")",
+    assert(num_regions > 0, "Must uncommit at least one region");
+    assert(_region_commit_map.get_next_zero_offset(start_idx, start_idx + num_regions) == start_idx + num_regions,
+           "Should only be committed regions in the range [%u, " SIZE_FORMAT ")",
            start_idx, start_idx + num_regions);
 
     size_t start_page = region_idx_to_page_idx(start_idx);