void PSParallelCompact::enqueue_region_stealing_tasks(
                                     GCTaskQueue* q,
                                     ParallelTaskTerminator* terminator_ptr,
                                     uint parallel_gc_threads) {

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

      TraceTime tm("steal task setup", print_phases(), true, gclog_or_tty);

  {- -------------------------------------------
  (1) 引数で指定された個数分(以下 parallel_gc_threads 個分)だけ StealRegionCompactionTask を追加.
      ---------------------------------------- -}

      // Once a thread has drained it's stack, it should try to steal regions from
      // other threads.
      if (parallel_gc_threads > 1) {
        for (uint j = 0; j < parallel_gc_threads; j++) {
          q->enqueue(new StealRegionCompactionTask(terminator_ptr));
        }
      }
    }