/* card marking write barrier. a card is a byte storing a mark flag, and the offset (in cells) of the first object in the card. the mark flag is set by the write barrier when an object in the card has a slot written to. the offset of the first object is set by the allocator. */ namespace factor { /* if CARD_POINTS_TO_NURSERY is set, CARD_POINTS_TO_AGING must also be set. */ #define CARD_POINTS_TO_NURSERY 0x80 #define CARD_POINTS_TO_AGING 0x40 #define CARD_MARK_MASK (CARD_POINTS_TO_NURSERY | CARD_POINTS_TO_AGING) typedef u8 card; #define CARD_BITS 8 #define CARD_SIZE (1<> CARD_BITS) + cards_offset); } inline static cell card_to_addr(card *c) { return ((cell)c - cards_offset) << CARD_BITS; } inline static cell card_offset(card *c) { return *(c - (cell)data->cards + (cell)data->allot_markers); } typedef u8 card_deck; #define DECK_BITS (CARD_BITS + 10) #define DECK_SIZE (1<> DECK_BITS) + decks_offset); } inline static cell deck_to_addr(card_deck *c) { return ((cell)c - decks_offset) << DECK_BITS; } inline static card *deck_to_card(card_deck *d) { return (card *)((((cell)d - decks_offset) << (DECK_BITS - CARD_BITS)) + cards_offset); } #define INVALID_ALLOT_MARKER 0xff VM_C_API cell allot_markers_offset; inline static card *addr_to_allot_marker(object *a) { return (card *)(((cell)a >> CARD_BITS) + allot_markers_offset); } /* the write barrier must be called any time we are potentially storing a pointer from an older generation to a younger one */ inline static void write_barrier(object *obj) { *addr_to_card((cell)obj) = CARD_MARK_MASK; *addr_to_deck((cell)obj) = CARD_MARK_MASK; } /* we need to remember the first object allocated in the card */ inline static void allot_barrier(object *address) { card *ptr = addr_to_allot_marker(address); if(*ptr == INVALID_ALLOT_MARKER) *ptr = ((cell)address & ADDR_CARD_MASK); } }