/*

 * Copyright (c) 2015, 2018, Red Hat, Inc. All rights reserved.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "gc/shenandoah/shenandoahAsserts.hpp"

#include "gc/shenandoah/shenandoahBrooksPointer.hpp"

#include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"

#include "gc/shenandoah/shenandoahConcurrentMark.hpp"

#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"

#include "gc/shenandoah/shenandoahStringDedup.hpp"

#include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"

#include "memory/iterator.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/prefetch.inline.hpp"

template <class T>

void ShenandoahConcurrentMark::do_task(ShenandoahObjToScanQueue* q, T* cl, jushort* live_data, ShenandoahMarkTask* task) {

  oop obj = task->obj();

  shenandoah_assert_not_forwarded_except(NULL, obj, _heap->is_concurrent_traversal_in_progress() && _heap->cancelled_gc());

  shenandoah_assert_marked(NULL, obj);

  shenandoah_assert_not_in_cset_except(NULL, obj, _heap->cancelled_gc());

  if (task->is_not_chunked()) {

    if (obj->is_instance()) {

      // Case 1: Normal oop, process as usual.

      obj->oop_iterate(cl);

    } else if (obj->is_objArray()) {

      // Case 2: Object array instance and no chunk is set. Must be the first

      // time we visit it, start the chunked processing.

      do_chunked_array_start<T>(q, cl, obj);

    } else {

      // Case 3: Primitive array. Do nothing, no oops there. We use the same

      // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:

      // We skip iterating over the klass pointer since we know that

      // Universe::TypeArrayKlass never moves.

      assert (obj->is_typeArray(), "should be type array");

    }

    // Count liveness the last: push the outstanding work to the queues first

    count_liveness(live_data, obj);

  } else {

    // Case 4: Array chunk, has sensible chunk id. Process it.

    do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow());

  }

}

inline void ShenandoahConcurrentMark::count_liveness(jushort* live_data, oop obj) {

  size_t region_idx = _heap->heap_region_index_containing(obj);

  ShenandoahHeapRegion* region = _heap->get_region(region_idx);

  size_t size = obj->size() + ShenandoahBrooksPointer::word_size();

  if (!region->is_humongous_start()) {

    assert(!region->is_humongous(), "Cannot have continuations here");

    size_t max = (1 << (sizeof(jushort) * 8)) - 1;

    if (size >= max) {

      // too big, add to region data directly

      region->increase_live_data_gc_words(size);

    } else {

      jushort cur = live_data[region_idx];

      size_t new_val = cur + size;

      if (new_val >= max) {

        // overflow, flush to region data

        region->increase_live_data_gc_words(new_val);

        live_data[region_idx] = 0;

      } else {

        // still good, remember in locals

        live_data[region_idx] = (jushort) new_val;

      }

    }

  } else {

    shenandoah_assert_in_correct_region(NULL, obj);

    size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);

    for (size_t i = region_idx; i < region_idx + num_regions; i++) {

      ShenandoahHeapRegion* chain_reg = _heap->get_region(i);

      assert(chain_reg->is_humongous(), "Expecting a humongous region");

      chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);

    }

  }

}

template <class T>

inline void ShenandoahConcurrentMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj) {

  assert(obj->is_objArray(), "expect object array");

  objArrayOop array = objArrayOop(obj);

  int len = array->length();

  if (len <= (int) ObjArrayMarkingStride*2) {

    // A few slices only, process directly

    array->oop_iterate_range(cl, 0, len);

  } else {

    int bits = log2_long((size_t) len);

    // Compensate for non-power-of-two arrays, cover the array in excess:

    if (len != (1 << bits)) bits++;

    // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to

    // boundaries against array->length(), touching the array header on every chunk.

    //

    // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.

    // If the array is not divided in chunk sizes, then there would be an irregular tail,

    // which we will process separately.

    int last_idx = 0;

    int chunk = 1;

    int pow = bits;

    // Handle overflow

    if (pow >= 31) {

      assert (pow == 31, "sanity");

      pow--;

      chunk = 2;

      last_idx = (1 << pow);

      bool pushed = q->push(ShenandoahMarkTask(array, 1, pow));

      assert(pushed, "overflow queue should always succeed pushing");

    }

    // Split out tasks, as suggested in ObjArrayChunkedTask docs. Record the last

    // successful right boundary to figure out the irregular tail.

    while ((1 << pow) > (int)ObjArrayMarkingStride &&

           (chunk*2 < ShenandoahMarkTask::chunk_size())) {

      pow--;

      int left_chunk = chunk*2 - 1;

      int right_chunk = chunk*2;

      int left_chunk_end = left_chunk * (1 << pow);

      if (left_chunk_end < len) {

        bool pushed = q->push(ShenandoahMarkTask(array, left_chunk, pow));

        assert(pushed, "overflow queue should always succeed pushing");

        chunk = right_chunk;

        last_idx = left_chunk_end;

      } else {

        chunk = left_chunk;

      }

    }

    // Process the irregular tail, if present

    int from = last_idx;

    if (from < len) {

      array->oop_iterate_range(cl, from, len);

    }

  }

}

template <class T>

inline void ShenandoahConcurrentMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow) {

  assert(obj->is_objArray(), "expect object array");

  objArrayOop array = objArrayOop(obj);

  assert (ObjArrayMarkingStride > 0, "sanity");

  // Split out tasks, as suggested in ObjArrayChunkedTask docs. Avoid pushing tasks that

  // are known to start beyond the array.

  while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {

    pow--;

    chunk *= 2;

    bool pushed = q->push(ShenandoahMarkTask(array, chunk - 1, pow));

    assert(pushed, "overflow queue should always succeed pushing");

  }

  int chunk_size = 1 << pow;

  int from = (chunk - 1) * chunk_size;

  int to = chunk * chunk_size;

#ifdef ASSERT

  int len = array->length();

  assert (0 <= from && from < len, "from is sane: %d/%d", from, len);

  assert (0 < to && to <= len, "to is sane: %d/%d", to, len);

#endif

  array->oop_iterate_range(cl, from, to);

}

class ShenandoahSATBBufferClosure : public SATBBufferClosure {

private:

  ShenandoahObjToScanQueue* _queue;

  ShenandoahHeap* _heap;

  ShenandoahMarkingContext* const _mark_context;

public:

  ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q) :

    _queue(q),

    _heap(ShenandoahHeap::heap()),

    _mark_context(_heap->marking_context())

  {

  }

  void do_buffer(void **buffer, size_t size) {

    if (_heap->has_forwarded_objects()) {

      if (ShenandoahStringDedup::is_enabled()) {

        do_buffer_impl<RESOLVE, ENQUEUE_DEDUP>(buffer, size);

      } else {

        do_buffer_impl<RESOLVE, NO_DEDUP>(buffer, size);

      }

    } else {

      if (ShenandoahStringDedup::is_enabled()) {

        do_buffer_impl<NONE, ENQUEUE_DEDUP>(buffer, size);

      } else {

        do_buffer_impl<NONE, NO_DEDUP>(buffer, size);

      }

    }

  }

  template<UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>

  void do_buffer_impl(void **buffer, size_t size) {

    for (size_t i = 0; i < size; ++i) {

      oop *p = (oop *) &buffer[i];

      ShenandoahConcurrentMark::mark_through_ref<oop, UPDATE_REFS, STRING_DEDUP>(p, _heap, _queue, _mark_context);

    }

  }

};

template<class T, UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>

inline void ShenandoahConcurrentMark::mark_through_ref(T *p, ShenandoahHeap* heap, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context) {

  T o = RawAccess<>::oop_load(p);

  if (!CompressedOops::is_null(o)) {

    oop obj = CompressedOops::decode_not_null(o);

    switch (UPDATE_REFS) {

    case NONE:

      break;

    case RESOLVE:

      obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);

      break;

    case SIMPLE:

      // We piggy-back reference updating to the marking tasks.

      obj = heap->update_with_forwarded_not_null(p, obj);

      break;

    case CONCURRENT:

      obj = heap->maybe_update_with_forwarded_not_null(p, obj);

      break;

    default:

      ShouldNotReachHere();

    }

    // Note: Only when concurrently updating references can obj become NULL here.

    // It happens when a mutator thread beats us by writing another value. In that

    // case we don't need to do anything else.

    if (UPDATE_REFS != CONCURRENT || !CompressedOops::is_null(obj)) {

      shenandoah_assert_not_forwarded(p, obj);

      shenandoah_assert_not_in_cset_except(p, obj, heap->cancelled_gc());

      if (mark_context->mark(obj)) {

        bool pushed = q->push(ShenandoahMarkTask(obj));

        assert(pushed, "overflow queue should always succeed pushing");

        if ((STRING_DEDUP == ENQUEUE_DEDUP) && ShenandoahStringDedup::is_candidate(obj)) {

          assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");

          ShenandoahStringDedup::enqueue_candidate(obj);

        }

      }

      shenandoah_assert_marked(p, obj);

    }

  }

}