vm/write_barrier.h

   1 /* card marking write barrier. a card is a byte storing a mark flag,
   2 and the offset (in cells) of the first object in the card.
   3
   4 the mark flag is set by the write barrier when an object in the
   5 card has a slot written to.
   6
   7 the offset of the first object is set by the allocator. */
   8
   9 /* if CARD_POINTS_TO_NURSERY is set, CARD_POINTS_TO_AGING must also be set. */
  10 #define CARD_POINTS_TO_NURSERY 0x80
  11 #define CARD_POINTS_TO_AGING 0x40
  12 #define CARD_MARK_MASK (CARD_POINTS_TO_NURSERY | CARD_POINTS_TO_AGING)
  13 typedef u8 F_CARD;
  14
  15 #define CARD_BITS 8
  16 #define CARD_SIZE (1<<CARD_BITS)
  17 #define ADDR_CARD_MASK (CARD_SIZE-1)
  18
  19 DLLEXPORT CELL cards_offset;
  20
  21 #define ADDR_TO_CARD(a) (F_CARD*)(((CELL)(a) >> CARD_BITS) + cards_offset)
  22 #define CARD_TO_ADDR(c) (CELL*)(((CELL)(c) - cards_offset)<<CARD_BITS)
  23
  24 typedef u8 F_DECK;
  25
  26 #define DECK_BITS (CARD_BITS + 10)
  27 #define DECK_SIZE (1<<DECK_BITS)
  28 #define ADDR_DECK_MASK (DECK_SIZE-1)
  29
  30 DLLEXPORT CELL decks_offset;
  31
  32 #define ADDR_TO_DECK(a) (F_DECK*)(((CELL)(a) >> DECK_BITS) + decks_offset)
  33 #define DECK_TO_ADDR(c) (CELL*)(((CELL)(c) - decks_offset) << DECK_BITS)
  34
  35 #define DECK_TO_CARD(d) (F_CARD*)((((CELL)(d) - decks_offset) << (DECK_BITS - CARD_BITS)) + cards_offset)
  36
  37 #define ADDR_TO_ALLOT_MARKER(a) (F_CARD*)(((CELL)(a) >> CARD_BITS) + allot_markers_offset)
  38 #define CARD_OFFSET(c) (*((c) - (CELL)data_heap->cards + (CELL)data_heap->allot_markers))
  39
  40 #define INVALID_ALLOT_MARKER 0xff
  41
  42 DLLEXPORT CELL allot_markers_offset;
  43
  44 /* the write barrier must be called any time we are potentially storing a
  45 pointer from an older generation to a younger one */
  46 INLINE void write_barrier(CELL address)
  47 {
  48         *ADDR_TO_CARD(address) = CARD_MARK_MASK;
  49         *ADDR_TO_DECK(address) = CARD_MARK_MASK;
  50 }
  51
  52 #define SLOT(obj,slot) (UNTAG(obj) + (slot) * CELLS)
  53
  54 INLINE void set_slot(CELL obj, CELL slot, CELL value)
  55 {
  56         put(SLOT(obj,slot),value);
  57         write_barrier(obj);
  58 }
  59
  60 /* we need to remember the first object allocated in the card */
  61 INLINE void allot_barrier(CELL address)
  62 {
  63         F_CARD *ptr = ADDR_TO_ALLOT_MARKER(address);
  64         if(*ptr == INVALID_ALLOT_MARKER)
  65                 *ptr = (address & ADDR_CARD_MASK);
  66 }