jdk-24/src/hotspot/share/gc/shared/cardTableRS.hpp

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#ifndef SHARE_VM_GC_SHARED_CARDTABLERS_HPP
#define SHARE_VM_GC_SHARED_CARDTABLERS_HPP

#include "gc/shared/cardTableModRefBSForCTRS.hpp"
#include "memory/memRegion.hpp"

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 CHeapObj<mtGC> {
  friend class VMStructs;
  // Below are private classes used in impl.
  friend class VerifyCTSpaceClosure;
  friend class ClearNoncleanCardWrapper;

  static jbyte clean_card_val() {
    return CardTableModRefBSForCTRS::clean_card;
  }

  static intptr_t clean_card_row() {
    return CardTableModRefBSForCTRS::clean_card_row;
  }

  static bool
  card_is_dirty_wrt_gen_iter(jbyte cv) {
    return CardTableModRefBSForCTRS::card_is_dirty_wrt_gen_iter(cv);
  }

  CLDRemSet _cld_rem_set;
  BarrierSet* _bs;

  CardTableModRefBSForCTRS* _ct_bs;

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

  enum ExtendedCardValue {
    youngergen_card   = CardTableModRefBSForCTRS::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  = CardTableModRefBSForCTRS::CT_MR_BS_last_reserved + 2,
    youngergenP2_card  = CardTableModRefBSForCTRS::CT_MR_BS_last_reserved + 3,
    youngergenP3_card  = CardTableModRefBSForCTRS::CT_MR_BS_last_reserved + 4,
    cur_youngergen_and_prev_nonclean_card =
      CardTableModRefBSForCTRS::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);
  ~CardTableRS();

  // Return the barrier set associated with "this."
  BarrierSet* bs() { return _bs; }

  // Set the barrier set.
  void set_bs(BarrierSet* bs) { _bs = bs; }

  CLDRemSet* cld_rem_set() { return &_cld_rem_set; }

  CardTableModRefBSForCTRS* ct_bs() { return _ct_bs; }

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

  // 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 = _ct_bs->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);

  void resize_covered_region(MemRegion new_region);

  bool is_aligned(HeapWord* addr) {
    return _ct_bs->is_card_aligned(addr);
  }

  void verify();

  void clear(MemRegion mr) { _ct_bs->clear(mr); }
  void clear_into_younger(Generation* old_gen);

  void invalidate(MemRegion mr) {
    _ct_bs->invalidate(mr);
  }
  void invalidate_or_clear(Generation* old_gen);

  static uintx ct_max_alignment_constraint() {
    return CardTableModRefBSForCTRS::ct_max_alignment_constraint();
  }

  jbyte* byte_for(void* p)     { return _ct_bs->byte_for(p); }
  jbyte* byte_after(void* p)   { return _ct_bs->byte_after(p); }
  HeapWord* addr_for(jbyte* p) { return _ct_bs->addr_for(p); }

  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;
  }

};

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);
};

#endif // SHARE_VM_GC_SHARED_CARDTABLERS_HPP