#include "gc_implementation/shared/liveRange.hpp"

#include "gc_implementation/shared/markSweep.inline.hpp"

#include "gc_implementation/shared/spaceDecorator.hpp"

template <class SpaceType>

inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {

  // Compute the new addresses for the live objects and store it in the mark

  // Used by universe::mark_sweep_phase2()

  HeapWord* compact_top; // This is where we are currently compacting to.

  // We're sure to be here before any objects are compacted into this

  // space, so this is a good time to initialize this:

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

  if (cp->space == NULL) {

    assert(cp->gen != NULL, "need a generation");

    assert(cp->threshold == NULL, "just checking");

    assert(cp->gen->first_compaction_space() == space, "just checking");

    cp->space = cp->gen->first_compaction_space();

    compact_top = cp->space->bottom();

    cp->space->set_compaction_top(compact_top);

    cp->threshold = cp->space->initialize_threshold();

  } else {

    compact_top = cp->space->compaction_top();

  }

  // 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.

  uint invocations = MarkSweep::total_invocations();

  bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);

  size_t allowed_deadspace = 0;

  if (skip_dead) {

    const size_t ratio = space->allowed_dead_ratio();

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

  }

  HeapWord* q = space->bottom();

  HeapWord* t = space->scan_limit();

  HeapWord*  end_of_live= q;            // One byte beyond the last byte of the last

                                        // live object.

  HeapWord*  first_dead = space->end(); // The first dead object.

  LiveRange* liveRange  = NULL;         // The current live range, recorded in the

                                        // first header of preceding free area.

  space->_first_dead = first_dead;

  const intx interval = PrefetchScanIntervalInBytes;

  while (q < t) {

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

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

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

           "these are the only valid states during a mark sweep");

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

      // prefetch beyond q

      Prefetch::write(q, interval);

      size_t size = space->scanned_block_size(q);

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

      q += size;

      end_of_live = q;

    } else {

      // run over all the contiguous dead objects

      HeapWord* end = q;

      do {

        // prefetch beyond end

        Prefetch::write(end, interval);

        end += space->scanned_block_size(end);

      } while (end < t && (!space->scanned_block_is_obj(end) || !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 (space->insert_deadspace(allowed_deadspace, q, sz)) {

          compact_top = cp->space->forward(oop(q), sz, cp, compact_top);

          q = end;

          end_of_live = end;

          continue;

        }

      }

      // otherwise, it really is a free region.

      // 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);

  }

  space->_end_of_live = end_of_live;

  if (end_of_live < first_dead) {

    first_dead = end_of_live;

  }

  space->_first_dead = first_dead;

  // save the compaction_top of the compaction space.

  cp->space->set_compaction_top(compact_top);

}

template <class SpaceType>

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

  // adjust all the interior pointers to point at the new locations of objects

  // Used by MarkSweep::mark_sweep_phase3()

  HeapWord* q = space->bottom();

  HeapWord* t = space->_end_of_live;  // Established by "prepare_for_compaction".

  assert(space->_first_dead <= space->_end_of_live, "Stands to reason, no?");

  if (q < t && space->_first_dead > q && !oop(q)->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* end = space->_first_dead;

    while (q < end) {

      // I originally tried to conjoin "block_start(q) == q" to the

      // assertion below, but that doesn't work, because you can't

      // accurately traverse previous objects to get to the current one

      // after their pointers have been

      // updated, until the actual compaction is done.  dld, 4/00

      assert(space->block_is_obj(q), "should be at block boundaries, and should be looking at objs");

      // point all the oops to the new location

      size_t size = oop(q)->adjust_pointers();

      size = space->adjust_obj_size(size);

      q += size;

    }

    if (space->_first_dead == t) {

      q = t;

    } else {

      // $$$ This is funky.  Using this to read the previously written

      // LiveRange.  See also use below.

      q = (HeapWord*)oop(space->_first_dead)->mark()->decode_pointer();

    }

  }

  const intx interval = PrefetchScanIntervalInBytes;

  debug_only(HeapWord* prev_q = NULL);

  while (q < t) {

    // prefetch beyond q

    Prefetch::write(q, interval);

    if (oop(q)->is_gc_marked()) {

      // q is alive

      // point all the oops to the new location

      size_t size = oop(q)->adjust_pointers();

      size = space->adjust_obj_size(size);

      debug_only(prev_q = q);

      q += size;

    } else {

      // q is not a live object, so its mark should point at the next

      // live object

      debug_only(prev_q = q);

      q = (HeapWord*) oop(q)->mark()->decode_pointer();

      assert(q > prev_q, "we should be moving forward through memory");

    }

  }

  assert(q == t, "just checking");

}

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()

  HeapWord*       q = space->bottom();

  HeapWord* const t = space->_end_of_live;

  debug_only(HeapWord* prev_q = NULL);

  if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {

    #ifdef ASSERT // Debug only

      // 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* const end = space->_first_dead;

      while (q < end) {

        size_t size = space->obj_size(q);

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

        prev_q = q;

        q += size;

      }

    #endif

    if (space->_first_dead == t) {

      q = t;

    } else {

      // $$$ Funky

      q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer();

    }

  }

  const intx scan_interval = PrefetchScanIntervalInBytes;

  const intx copy_interval = PrefetchCopyIntervalInBytes;

  while (q < t) {

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

      // mark is pointer to next marked oop

      debug_only(prev_q = q);

      q = (HeapWord*) oop(q)->mark()->decode_pointer();

      assert(q > prev_q, "we should be moving forward through memory");

    } else {

      // prefetch beyond q

      Prefetch::read(q, scan_interval);

      // size and destination

      size_t size = space->obj_size(q);

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

      // prefetch beyond compaction_top

      Prefetch::write(compaction_top, copy_interval);

      // copy object and reinit its mark

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

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

      oop(compaction_top)->init_mark();

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

      debug_only(prev_q = q);

      q += size;

    }

  }

  // Let's remember if we were empty before we did the compaction.

  bool was_empty = space->used_region().is_empty();

  // Reset space after compaction is complete

  space->reset_after_compaction();

  // We do this clear, below, since it has overloaded meanings for some

  // space subtypes.  For example, OffsetTableContigSpace's that were

  // compacted into will have had their offset table thresholds updated

  // continuously, but those that weren't need to have their thresholds

  // re-initialized.  Also mangles unused area for debugging.

  if (space->used_region().is_empty()) {

    if (!was_empty) space->clear(SpaceDecorator::Mangle);

  } else {

    if (ZapUnusedHeapArea) space->mangle_unused_area();

  }

}