template <class T>
inline void UpdateRSOrPushRefOopClosure::do_oop_work(T* p) {

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

      oop obj = oopDesc::load_decode_heap_oop(p);

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

    #ifdef ASSERT
      // can't do because of races
      // assert(obj == NULL || obj->is_oop(), "expected an oop");

      // Do the safe subset of is_oop
      if (obj != NULL) {
    #ifdef CHECK_UNHANDLED_OOPS
        oopDesc* o = obj.obj();
    #else
        oopDesc* o = obj;
    #endif // CHECK_UNHANDLED_OOPS
        assert((intptr_t)o % MinObjAlignmentInBytes == 0, "not oop aligned");
        assert(Universe::heap()->is_in_reserved(obj), "must be in heap");
      }
    #endif // ASSERT

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

      assert(_from != NULL, "from region must be non-NULL");

  {- -------------------------------------------
  (1) (処理対象のオブジェクトに対応する HeapRegion が見つからなければ何もしない.
       また, 参照元と参照先が同じ HeapRegion だった場合も何もしない.)
      ---------------------------------------- -}

      HeapRegion* to = _g1->heap_region_containing(obj);
      if (to != NULL && _from != to) {

  {- -------------------------------------------
  (1) _record_refs_into_cset フラグが true で, かつポインタが collection set 内を差していれば (?? #TODO), 
      _push_ref_cl フィールドの...に対して do_oop() を呼び出す.
      (<= ここで _push_ref_cl フィールドに入っているのは G1ParPushHeapRSClosure??)
      そうでない場合は, G1RemSet::par_write_ref() を呼び出す (なお, この呼び出し時には worker 番号も指定).

      (なお, _record_refs_into_cset フラグが true になるのは, evacuation pause 中で RSet update を行っている間だけ.
       また, この場合でも, 既に self_forwarded されているなら処理はしない.)
      ---------------------------------------- -}

        // The _record_refs_into_cset flag is true during the RSet
        // updating part of an evacuation pause. It is false at all
        // other times:
        //  * rebuilding the rembered sets after a full GC
        //  * during concurrent refinement.
        //  * updating the remembered sets of regions in the collection
        //    set in the event of an evacuation failure (when deferred
        //    updates are enabled).

        if (_record_refs_into_cset && to->in_collection_set()) {
          // We are recording references that point into the collection
          // set and this particular reference does exactly that...
          // If the referenced object has already been forwarded
          // to itself, we are handling an evacuation failure and
          // we have already visited/tried to copy this object
          // there is no need to retry.
          if (!self_forwarded(obj)) {
            assert(_push_ref_cl != NULL, "should not be null");
            // Push the reference in the refs queue of the G1ParScanThreadState
            // instance for this worker thread.
            _push_ref_cl->do_oop(p);
          }

          // Deferred updates to the CSet are either discarded (in the normal case),
          // or processed (if an evacuation failure occurs) at the end
          // of the collection.
          // See G1RemSet::cleanup_after_oops_into_collection_set_do().
        } else {
          // We either don't care about pushing references that point into the
          // collection set (i.e. we're not during an evacuation pause) _or_
          // the reference doesn't point into the collection set. Either way
          // we add the reference directly to the RSet of the region containing
          // the referenced object.
          _g1_rem_set->par_write_ref(_from, p, _worker_i);
        }
      }
    }