C++ LiveRange::set_start方法代码示例

//.........这里部分代码省略.........
    } else {
      /* run over all the contiguous dead objects */
      HeapWord* end = q;
      do {
        /* prefetch beyond end */
        Prefetch::write(end, interval);
        end += oop(end)->size();
      } while (end < t && (!oop(end)->is_gc_marked()));

      /* see if we might want to pretend this object is alive so that
       * we don't have to compact quite as often.
       */
      if (allowed_deadspace > 0 && q == compact_top) {
        size_t sz = pointer_delta(end, q);
        if (insert_deadspace(allowed_deadspace, q, sz)) {
          size_t compaction_max_size = pointer_delta(compact_end, compact_top);

          // This should only happen if a space in the young gen overflows the
          // old gen. If that should happen, we null out the start_array, because
          // the young spaces are not covered by one.
          while (sz > compaction_max_size) {
            // First record the last compact_top
            dest->set_compaction_top(compact_top);

            // Advance to the next compaction decorator
            advance_destination_decorator();
            dest = destination_decorator();

            // Update compaction info
            start_array = dest->start_array();
            compact_top = dest->compaction_top();
            compact_end = dest->space()->end();
            assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");
            assert(compact_end > compact_top, "Must always be space remaining");
            compaction_max_size =
              pointer_delta(compact_end, compact_top);
          }

          // store the forwarding pointer into the mark word
          if (q != compact_top) {
            oop(q)->forward_to(oop(compact_top));
            assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark");
          } else {
            // if the object isn't moving we can just set the mark to the default
            // mark and handle it specially later on.
            oop(q)->init_mark();
            assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL");
          }

          // Update object start array
          if (start_array) {
            start_array->allocate_block(compact_top);
          }

          VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(oop(q), sz));
          compact_top += sz;
          assert(compact_top <= dest->space()->end(),
            "Exceeding space in destination");

          q = end;
          end_of_live = end;
          continue;
        }
      }

      /* for the previous LiveRange, record the end of the live objects. */
      if (liveRange) {
        liveRange->set_end(q);
      }

      /* record the current LiveRange object.
       * liveRange->start() is overlaid on the mark word.
       */
      liveRange = (LiveRange*)q;
      liveRange->set_start(end);
      liveRange->set_end(end);

      /* see if this is the first dead region. */
      if (q < first_dead) {
        first_dead = q;
      }

      /* move on to the next object */
      q = end;
    }
  }

  assert(q == t, "just checking");
  if (liveRange != NULL) {
    liveRange->set_end(q);
  }
  _end_of_live = end_of_live;
  if (end_of_live < first_dead) {
    first_dead = end_of_live;
  }
  _first_dead = first_dead;

  // Update compaction top
  dest->set_compaction_top(compact_top);
}