8332961: Parallel: Limit PSParallelCompact::verify_complete range

Reviewed-by: tschatzl, gli

src/hotspot/share/gc/parallel/psParallelCompact.cpp

@@ -2130,14 +2130,14 @@ void PSParallelCompact::verify_filler_in_dense_prefix() {
 }
 
 void PSParallelCompact::verify_complete(SpaceId space_id) {
-  // All Regions between space bottom() to new_top() should be marked as filled
-  // and all Regions between new_top() and top() should be available (i.e.,
-  // should have been emptied).
+  // All Regions served as compaction targets, from dense_prefix() to
+  // new_top(), should be marked as filled and all Regions between new_top()
+  // and top() should be available (i.e., should have been emptied).
   ParallelCompactData& sd = summary_data();
   SpaceInfo si = _space_info[space_id];
   HeapWord* new_top_addr = sd.region_align_up(si.new_top());
   HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
-  const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
+  const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
   const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
   const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);