C++ oop::oop_iterate_backwards方法代码示例

oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
  assert(_g1h->obj_in_cs(old),
         err_msg("Object " PTR_FORMAT " should be in the CSet", p2i(old)));

  oop forward_ptr = old->forward_to_atomic(old);
  if (forward_ptr == NULL) {
    // Forward-to-self succeeded. We are the "owner" of the object.
    HeapRegion* r = _g1h->heap_region_containing(old);

    if (!r->evacuation_failed()) {
      r->set_evacuation_failed(true);
     _g1h->hr_printer()->evac_failure(r);
    }

    _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);

    _scanner.set_region(r);
    old->oop_iterate_backwards(&_scanner);

    return old;
  } else {
    // Forward-to-self failed. Either someone else managed to allocate
    // space for this object (old != forward_ptr) or they beat us in
    // self-forwarding it (old == forward_ptr).
    assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
           err_msg("Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
                   "should not be in the CSet",
                   p2i(old), p2i(forward_ptr)));
    return forward_ptr;
  }
}

oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
                                                 oop const old,
                                                 markOop const old_mark) {
  const size_t word_sz = old->size();
  HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
  // +1 to make the -1 indexes valid...
  const int young_index = from_region->young_index_in_cset()+1;
  assert( (from_region->is_young() && young_index >  0) ||
         (!from_region->is_young() && young_index == 0), "invariant" );
  const AllocationContext_t context = from_region->allocation_context();

  uint age = 0;
  InCSetState dest_state = next_state(state, old_mark, age);
  HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);

  // PLAB allocations should succeed most of the time, so we'll
  // normally check against NULL once and that's it.
  if (obj_ptr == NULL) {
    obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context);
    if (obj_ptr == NULL) {
      obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context);
      if (obj_ptr == NULL) {
        // This will either forward-to-self, or detect that someone else has
        // installed a forwarding pointer.
        return handle_evacuation_failure_par(old, old_mark);
      }
    }
  }

  assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
  assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");

#ifndef PRODUCT
  // Should this evacuation fail?
  if (_g1h->evacuation_should_fail()) {
    // Doing this after all the allocation attempts also tests the
    // undo_allocation() method too.
    _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
    return handle_evacuation_failure_par(old, old_mark);
  }
#endif // !PRODUCT

  // We're going to allocate linearly, so might as well prefetch ahead.
  Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);

  const oop obj = oop(obj_ptr);
  const oop forward_ptr = old->forward_to_atomic(obj);
  if (forward_ptr == NULL) {
    Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);

    if (dest_state.is_young()) {
      if (age < markOopDesc::max_age) {
        age++;
      }
      if (old_mark->has_displaced_mark_helper()) {
        // In this case, we have to install the mark word first,
        // otherwise obj looks to be forwarded (the old mark word,
        // which contains the forward pointer, was copied)
        obj->set_mark(old_mark);
        markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
        old_mark->set_displaced_mark_helper(new_mark);
      } else {
        obj->set_mark(old_mark->set_age(age));
      }
      age_table()->add(age, word_sz);
    } else {
      obj->set_mark(old_mark);
    }

    if (G1StringDedup::is_enabled()) {
      const bool is_from_young = state.is_young();
      const bool is_to_young = dest_state.is_young();
      assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
             "sanity");
      assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
             "sanity");
      G1StringDedup::enqueue_from_evacuation(is_from_young,
                                             is_to_young,
                                             _worker_id,
                                             obj);
    }

    size_t* const surv_young_words = surviving_young_words();
    surv_young_words[young_index] += word_sz;

    if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
      // We keep track of the next start index in the length field of
      // the to-space object. The actual length can be found in the
      // length field of the from-space object.
      arrayOop(obj)->set_length(0);
      oop* old_p = set_partial_array_mask(old);
      push_on_queue(old_p);
    } else {
      HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
      _scanner.set_region(to_region);
      obj->oop_iterate_backwards(&_scanner);
    }
    return obj;
  } else {
    _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
//.........这里部分代码省略.........