#include "oops/oopsHierarchy.hpp"

class DeadSpacer : StackObj {

  size_t _allowed_deadspace_words;

  bool _active;

  CompactibleSpace* _space;

public:

  DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) {

    size_t ratio = _space->allowed_dead_ratio();

    _active = ratio > 0;

    if (_active) {

      assert(!UseG1GC, "G1 should not be using dead space");

      // We allow some amount of garbage towards the bottom of the space, so

      // we don't start compacting before there is a significant gain to be made.

      // Occasionally, we want to ensure a full compaction, which is determined

      // by the MarkSweepAlwaysCompactCount parameter.

      if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) {

        _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;

      } else {

        _active = false;

      }

    }

  }

  bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {

    if (!_active) {

      return false;

    }

    size_t dead_length = pointer_delta(dead_end, dead_start);

    if (_allowed_deadspace_words >= dead_length) {

      _allowed_deadspace_words -= dead_length;

      CollectedHeap::fill_with_object(dead_start, dead_length);

      oop obj = oop(dead_start);

      obj->set_mark(obj->mark()->set_marked());

      assert(dead_length == (size_t)obj->size(), "bad filler object size");

      log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",

          p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);

      return true;

    } else {

      _active = false;

      return false;

    }

  }

};

    cp->space->set_compaction_top(cp->space->bottom());

  HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.

  DeadSpacer dead_spacer(space);

  HeapWord*  end_of_live = space->bottom();  // One byte beyond the last byte of the last live object.

  HeapWord*  first_dead = NULL; // The first dead object.

  HeapWord* cur_obj = space->bottom();

  HeapWord* scan_limit = space->scan_limit();

  while (cur_obj < scan_limit) {

    assert(!space->scanned_block_is_obj(cur_obj) ||

           oop(cur_obj)->mark()->is_marked() || oop(cur_obj)->mark()->is_unlocked() ||

           oop(cur_obj)->mark()->has_bias_pattern(),

    if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) {

      // prefetch beyond cur_obj

      Prefetch::write(cur_obj, interval);

      size_t size = space->scanned_block_size(cur_obj);

      compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top);

      cur_obj += size;

      end_of_live = cur_obj;

      HeapWord* end = cur_obj;

      } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));

      if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {

        oop obj = oop(cur_obj);

        compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);

        end_of_live = end;

      } else {

        // otherwise, it really is a free region.

        // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.

        *(HeapWord**)cur_obj = end;

        // see if this is the first dead region.

        if (first_dead == NULL) {

          first_dead = cur_obj;

      cur_obj = end;

  assert(cur_obj == scan_limit, "just checking");

  if (first_dead != NULL) {

    space->_first_dead = first_dead;

  } else {

    space->_first_dead = end_of_live;

  HeapWord* cur_obj = space->bottom();

  HeapWord* const end_of_live = space->_end_of_live;  // Established by "scan_and_forward".

  HeapWord* const first_dead = space->_first_dead;    // Established by "scan_and_forward".

  assert(first_dead <= end_of_live, "Stands to reason, no?");

  debug_only(HeapWord* prev_obj = NULL);

  while (cur_obj < end_of_live) {

    Prefetch::write(cur_obj, interval);

    if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) {

      // cur_obj is alive

      size_t size = MarkSweep::adjust_pointers(oop(cur_obj));

      debug_only(prev_obj = cur_obj);

      cur_obj += size;

      debug_only(prev_obj = cur_obj);

      // cur_obj is not a live object, instead it points at the next live object

      cur_obj = *(HeapWord**)cur_obj;

      assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj));

  assert(cur_obj == end_of_live, "just checking");

#ifdef ASSERT

template <class SpaceType>

inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) {

  HeapWord* cur_obj = space->bottom();

  if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {

     // we have a chunk of the space which hasn't moved and we've reinitialized

     // the mark word during the previous pass, so we can't use is_gc_marked for

     // the traversal.

     HeapWord* prev_obj = NULL;

     while (cur_obj < space->_first_dead) {

       size_t size = space->obj_size(cur_obj);

       assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)");

       prev_obj = cur_obj;

       cur_obj += size;

     }

  }

}

#endif

inline void CompactibleSpace::clear_empty_region(SpaceType* space) {

template <class SpaceType>

inline void CompactibleSpace::scan_and_compact(SpaceType* space) {

  // Copy all live objects to their new location

  // Used by MarkSweep::mark_sweep_phase4()

  verify_up_to_first_dead(space);

  HeapWord* const end_of_live = space->_end_of_live;

  assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live));

  if (space->_first_dead == end_of_live && !oop(space->bottom())->is_gc_marked()) {

    // Nothing to compact. The space is either empty or all live object should be left in place.

    clear_empty_region(space);

    return;

  }

  const intx scan_interval = PrefetchScanIntervalInBytes;

  const intx copy_interval = PrefetchCopyIntervalInBytes;

  assert(space->bottom() < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(space->bottom()), p2i(end_of_live));

  HeapWord* cur_obj = space->bottom();

  if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {

    // All object before _first_dead can be skipped. They should not be moved.

    // A pointer to the first live object is stored at the memory location for _first_dead.

    cur_obj = *(HeapWord**)(space->_first_dead);

  }

  debug_only(HeapWord* prev_obj = NULL);

  while (cur_obj < end_of_live) {

    if (!oop(cur_obj)->is_gc_marked()) {

      debug_only(prev_obj = cur_obj);

      // The first word of the dead object contains a pointer to the next live object or end of space.

      cur_obj = *(HeapWord**)cur_obj;

      assert(cur_obj > prev_obj, "we should be moving forward through memory");

    } else {

      // prefetch beyond q

      Prefetch::read(cur_obj, scan_interval);

      // size and destination

      size_t size = space->obj_size(cur_obj);

      HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee();

      // prefetch beyond compaction_top

      Prefetch::write(compaction_top, copy_interval);

      // copy object and reinit its mark

      assert(cur_obj != compaction_top, "everything in this pass should be moving");

      Copy::aligned_conjoint_words(cur_obj, compaction_top, size);

      oop(compaction_top)->init_mark();

      assert(oop(compaction_top)->klass() != NULL, "should have a class");

      debug_only(prev_obj = cur_obj);

      cur_obj += size;

    }

  }

  clear_empty_region(space);

}