/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * 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/shared/cardTable.hpp"

#include "memory/memRegion.hpp"

#include "oops/oop.hpp"

class DirtyCardToOopClosure;

class Generation;

class Space;

class OopsInGenClosure;

// Helper to remember modified oops in all clds.

class CLDRemSet {

  bool _accumulate_modified_oops;

 public:

  CLDRemSet() : _accumulate_modified_oops(false) {}

  void set_accumulate_modified_oops(bool value) { _accumulate_modified_oops = value; }

  bool accumulate_modified_oops() { return _accumulate_modified_oops; }

  bool mod_union_is_clear();

  void clear_mod_union();

};

// This RemSet uses a card table both as shared data structure

// for a mod ref barrier set and for the rem set information.

class CardTableRS: public CardTable {

  friend class VMStructs;

  // Below are private classes used in impl.

  friend class VerifyCTSpaceClosure;

  friend class ClearNoncleanCardWrapper;

  CLDRemSet _cld_rem_set;

  void verify_space(Space* s, HeapWord* gen_start);

  enum ExtendedCardValue {

    youngergen_card   = CT_MR_BS_last_reserved + 1,

    // These are for parallel collection.

    // There are three P (parallel) youngergen card values.  In general, this

    // needs to be more than the number of generations (including the perm

    // gen) that might have younger_refs_do invoked on them separately.  So

    // if we add more gens, we have to add more values.

    youngergenP1_card  = CT_MR_BS_last_reserved + 2,

    youngergenP2_card  = CT_MR_BS_last_reserved + 3,

    youngergenP3_card  = CT_MR_BS_last_reserved + 4,

    cur_youngergen_and_prev_nonclean_card =

      CT_MR_BS_last_reserved + 5

  };

  // An array that contains, for each generation, the card table value last

  // used as the current value for a younger_refs_do iteration of that

  // portion of the table. The perm gen is index 0. The young gen is index 1,

  // but will always have the value "clean_card". The old gen is index 2.

  jbyte* _last_cur_val_in_gen;

  jbyte _cur_youngergen_card_val;

  // Number of generations, plus one for lingering PermGen issues in CardTableRS.

  static const int _regions_to_iterate = 3;

  jbyte cur_youngergen_card_val() {

    return _cur_youngergen_card_val;

  }

  void set_cur_youngergen_card_val(jbyte v) {

    _cur_youngergen_card_val = v;

  }

  bool is_prev_youngergen_card_val(jbyte v) {

    return

      youngergen_card <= v &&

      v < cur_youngergen_and_prev_nonclean_card &&

      v != _cur_youngergen_card_val;

  }

  // Return a youngergen_card_value that is not currently in use.

  jbyte find_unused_youngergenP_card_value();

public:

  CardTableRS(MemRegion whole_heap, bool scanned_concurrently);

  ~CardTableRS();

  CLDRemSet* cld_rem_set() { return &_cld_rem_set; }

  void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl, uint n_threads);

  virtual void verify_used_region_at_save_marks(Space* sp) const NOT_DEBUG_RETURN;

  // Override.

  void prepare_for_younger_refs_iterate(bool parallel);

  // Card table entries are cleared before application; "blk" is

  // responsible for dirtying if the oop is still older-to-younger after

  // closure application.

  void younger_refs_iterate(Generation* g, OopsInGenClosure* blk, uint n_threads);

  void inline_write_ref_field_gc(void* field, oop new_val) {

    jbyte* byte = byte_for(field);

    *byte = youngergen_card;

  }

  void write_ref_field_gc_work(void* field, oop new_val) {

    inline_write_ref_field_gc(field, new_val);

  }

  // Override.  Might want to devirtualize this in the same fashion as

  // above.  Ensures that the value of the card for field says that it's

  // a younger card in the current collection.

  virtual void write_ref_field_gc_par(void* field, oop new_val);

  bool is_aligned(HeapWord* addr) {

    return is_card_aligned(addr);

  }

  void verify();

  void initialize();

  void clear_into_younger(Generation* old_gen);

  void invalidate_or_clear(Generation* old_gen);

  bool is_prev_nonclean_card_val(jbyte v) {

    return

      youngergen_card <= v &&

      v <= cur_youngergen_and_prev_nonclean_card &&

      v != _cur_youngergen_card_val;

  }

  static bool youngergen_may_have_been_dirty(jbyte cv) {

    return cv == CardTableRS::cur_youngergen_and_prev_nonclean_card;

  }

  // *** Support for parallel card scanning.

  // dirty and precleaned are equivalent wrt younger_refs_iter.

  static bool card_is_dirty_wrt_gen_iter(jbyte cv) {

    return cv == dirty_card || cv == precleaned_card;

  }

  // Returns "true" iff the value "cv" will cause the card containing it

  // to be scanned in the current traversal.  May be overridden by

  // subtypes.

  bool card_will_be_scanned(jbyte cv);

  // Returns "true" iff the value "cv" may have represented a dirty card at

  // some point.

  bool card_may_have_been_dirty(jbyte cv);

  // Iterate over the portion of the card-table which covers the given

  // region mr in the given space and apply cl to any dirty sub-regions

  // of mr. Clears the dirty cards as they are processed.

  void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,

                                                OopsInGenClosure* cl, CardTableRS* ct,

                                                uint n_threads);

  // Work method used to implement non_clean_card_iterate_possibly_parallel()

  // above in the parallel case.

  virtual void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,

                                                    OopsInGenClosure* cl, CardTableRS* ct,

                                                    uint n_threads);

  // This is an array, one element per covered region of the card table.

  // Each entry is itself an array, with one element per chunk in the

  // covered region.  Each entry of these arrays is the lowest non-clean

  // card of the corresponding chunk containing part of an object from the

  // previous chunk, or else NULL.

  typedef jbyte*  CardPtr;

  typedef CardPtr* CardArr;

  CardArr* _lowest_non_clean;

  size_t*  _lowest_non_clean_chunk_size;

  uintptr_t* _lowest_non_clean_base_chunk_index;

  volatile int* _last_LNC_resizing_collection;

  virtual bool is_in_young(oop obj) const;

};

class ClearNoncleanCardWrapper: public MemRegionClosure {

  DirtyCardToOopClosure* _dirty_card_closure;

  CardTableRS* _ct;

  bool _is_par;

private:

  // Clears the given card, return true if the corresponding card should be

  // processed.

  inline bool clear_card(jbyte* entry);

  // Work methods called by the clear_card()

  inline bool clear_card_serial(jbyte* entry);

  inline bool clear_card_parallel(jbyte* entry);

  // check alignment of pointer

  bool is_word_aligned(jbyte* entry);

public:

  ClearNoncleanCardWrapper(DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct, bool is_par);

  void do_MemRegion(MemRegion mr);

};