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#ifndef SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP

#define SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP

#include "gc/g1/g1RegionToSpaceMapper.hpp"

#include "gc/shared/blockOffsetTable.hpp"

#include "memory/memRegion.hpp"

#include "memory/virtualspace.hpp"

#include "utilities/globalDefinitions.hpp"

// Forward declarations

class G1BlockOffsetTable;

class G1ContiguousSpace;

// This implementation of "G1BlockOffsetTable" divides the covered region

// into "N"-word subregions (where "N" = 2^"LogN".  An array with an entry

// for each such subregion indicates how far back one must go to find the

// start of the chunk that includes the first word of the subregion.

//

// Each G1BlockOffsetTablePart is owned by a G1ContiguousSpace.

class G1BlockOffsetTable: public CHeapObj<mtGC> {

  friend class G1BlockOffsetTablePart;

  friend class VMStructs;

private:

  // The reserved region covered by the table.

  MemRegion _reserved;

  // Array for keeping offsets for retrieving object start fast given an

  // address.

  u_char* _offset_array;          // byte array keeping backwards offsets

  void check_offset(size_t offset, const char* msg) const {

    assert(offset <= BOTConstants::N_words,

           "%s - offset: " SIZE_FORMAT ", N_words: %u",

           msg, offset, BOTConstants::N_words);

  }

  // Bounds checking accessors:

  // For performance these have to devolve to array accesses in product builds.

  inline u_char offset_array(size_t index) const;

  void set_offset_array_raw(size_t index, u_char offset) {

    _offset_array[index] = offset;

  }

  inline void set_offset_array(size_t index, u_char offset);

  inline void set_offset_array(size_t index, HeapWord* high, HeapWord* low);

  inline void set_offset_array(size_t left, size_t right, u_char offset);

  bool is_card_boundary(HeapWord* p) const;

  void check_index(size_t index, const char* msg) const NOT_DEBUG_RETURN;

public:

  // Return the number of slots needed for an offset array

  // that covers mem_region_words words.

  static size_t compute_size(size_t mem_region_words) {

    size_t number_of_slots = (mem_region_words / BOTConstants::N_words);

    return ReservedSpace::allocation_align_size_up(number_of_slots);

  }

  // Returns how many bytes of the heap a single byte of the BOT corresponds to.

  static size_t heap_map_factor() {

    return BOTConstants::N_bytes;

  }

  // Initialize the Block Offset Table to cover the memory region passed

  // in the heap parameter.

  G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage);

  // Return the appropriate index into "_offset_array" for "p".

  inline size_t index_for(const void* p) const;

  inline size_t index_for_raw(const void* p) const;

  // Return the address indicating the start of the region corresponding to

  // "index" in "_offset_array".

  inline HeapWord* address_for_index(size_t index) const;

  // Variant of address_for_index that does not check the index for validity.

  inline HeapWord* address_for_index_raw(size_t index) const {

    return _reserved.start() + (index << BOTConstants::LogN_words);

  }

};

class G1BlockOffsetTablePart {

  friend class G1BlockOffsetTable;

  friend class VMStructs;

private:

  // allocation boundary at which offset array must be updated

  HeapWord* _next_offset_threshold;

  size_t    _next_offset_index;      // index corresponding to that boundary

  // Indicates if an object can span into this G1BlockOffsetTablePart.

  debug_only(bool _object_can_span;)

  // This is the global BlockOffsetTable.

  G1BlockOffsetTable* _bot;

  // The space that owns this subregion.

  G1ContiguousSpace* _space;

  // Sets the entries

  // corresponding to the cards starting at "start" and ending at "end"

  // to point back to the card before "start": the interval [start, end)

  // is right-open.

  void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);

  // Same as above, except that the args here are a card _index_ interval

  // that is closed: [start_index, end_index]

  void set_remainder_to_point_to_start_incl(size_t start, size_t end);

  // Zero out the entry for _bottom (offset will be zero). Does not check for availability of the

  // memory first.

  void zero_bottom_entry_raw();

  // Variant of initialize_threshold that does not check for availability of the

  // memory first.

  HeapWord* initialize_threshold_raw();

  inline size_t block_size(const HeapWord* p) const;

  // Returns the address of a block whose start is at most "addr".

  // If "has_max_index" is true, "assumes "max_index" is the last valid one

  // in the array.

  inline HeapWord* block_at_or_preceding(const void* addr,

                                         bool has_max_index,

                                         size_t max_index) const;

  // "q" is a block boundary that is <= "addr"; "n" is the address of the

  // next block (or the end of the space.)  Return the address of the

  // beginning of the block that contains "addr".  Does so without side

  // effects (see, e.g., spec of  block_start.)

  inline HeapWord* forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,

                                                          const void* addr) const;

  // "q" is a block boundary that is <= "addr"; return the address of the

  // beginning of the block that contains "addr".  May have side effects

  // on "this", by updating imprecise entries.

  inline HeapWord* forward_to_block_containing_addr(HeapWord* q,

                                                    const void* addr);

  // "q" is a block boundary that is <= "addr"; "n" is the address of the

  // next block (or the end of the space.)  Return the address of the

  // beginning of the block that contains "addr".  May have side effects

  // on "this", by updating imprecise entries.

  HeapWord* forward_to_block_containing_addr_slow(HeapWord* q,

                                                  HeapWord* n,

                                                  const void* addr);

  // Requires that "*threshold_" be the first array entry boundary at or

  // above "blk_start", and that "*index_" be the corresponding array

  // index.  If the block starts at or crosses "*threshold_", records

  // "blk_start" as the appropriate block start for the array index

  // starting at "*threshold_", and for any other indices crossed by the

  // block.  Updates "*threshold_" and "*index_" to correspond to the first

  // index after the block end.

  void alloc_block_work(HeapWord** threshold_, size_t* index_,

                        HeapWord* blk_start, HeapWord* blk_end);

  void check_all_cards(size_t left_card, size_t right_card) const;

public:

  //  The elements of the array are initialized to zero.

  G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp);

  void verify() const;

  // Returns the address of the start of the block containing "addr", or

  // else "null" if it is covered by no block.  (May have side effects,

  // namely updating of shared array entries that "point" too far

  // backwards.  This can occur, for example, when lab allocation is used

  // in a space covered by the table.)

  inline HeapWord* block_start(const void* addr);

  // Same as above, but does not have any of the possible side effects

  // discussed above.

  inline HeapWord* block_start_const(const void* addr) const;

  // Initialize the threshold to reflect the first boundary after the

  // bottom of the covered region.

  HeapWord* initialize_threshold();

  void reset_bot() {

    zero_bottom_entry_raw();

    initialize_threshold_raw();

  }

  // Return the next threshold, the point at which the table should be

  // updated.

  HeapWord* threshold() const { return _next_offset_threshold; }

  // These must be guaranteed to work properly (i.e., do nothing)

  // when "blk_start" ("blk" for second version) is "NULL".  In this

  // implementation, that's true because NULL is represented as 0, and thus

  // never exceeds the "_next_offset_threshold".

  void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {

    if (blk_end > _next_offset_threshold) {

      alloc_block_work(&_next_offset_threshold, &_next_offset_index, blk_start, blk_end);

    }

  }

  void alloc_block(HeapWord* blk, size_t size) {

    alloc_block(blk, blk+size);

  }

  void set_for_starts_humongous(HeapWord* obj_top, size_t fill_size);

  void set_object_can_span(bool can_span) NOT_DEBUG_RETURN;

  void print_on(outputStream* out) PRODUCT_RETURN;

};

#endif // SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP