void add_reference_work(OopOrNarrowOopStar from, bool par) {

  {- -------------------------------------------
  (1) 
      ---------------------------------------- -}

        // Must make this robust in case "from" is not in "_hr", because of
        // concurrency.

  {- -------------------------------------------
  (1) (トレース出力)
      ---------------------------------------- -}

    #if HRRS_VERBOSE
        gclog_or_tty->print_cr("    PRT::Add_reference_work(" PTR_FORMAT "->" PTR_FORMAT").",
                               from, *from);
    #endif

  {- -------------------------------------------
  (1) (変数宣言など)
      ---------------------------------------- -}

        HeapRegion* loc_hr = hr();

  {- -------------------------------------------
  (1) PerRegionTable::add_card_work() を呼んで記録処理を行う.
      (ただし, from 引数の指すアドレスが
       この PerRegionTable が表す HeapRegion 内にない場合は
       (= is_in_reserved() が false であれば),
       記録する必要は無いので, 何もしない)
      ---------------------------------------- -}

        // If the test below fails, then this table was reused concurrently
        // with this operation.  This is OK, since the old table was coarsened,
        // and adding a bit to the new table is never incorrect.
        if (loc_hr->is_in_reserved(from)) {
          size_t hw_offset = pointer_delta((HeapWord*)from, loc_hr->bottom());
          CardIdx_t from_card = (CardIdx_t)
              hw_offset >> (CardTableModRefBS::card_shift - LogHeapWordSize);

          assert(0 <= from_card && from_card < HeapRegion::CardsPerRegion,
                 "Must be in range.");
          add_card_work(from_card, par);
        }
      }