87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
/* card marking write barrier. a card is a byte storing a mark flag,
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and the offset (in cells) of the first object in the card.
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the mark flag is set by the write barrier when an object in the
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card has a slot written to.
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the offset of the first object is set by the allocator. */
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VM_C_API factor::cell cards_offset;
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VM_C_API factor::cell decks_offset;
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namespace factor
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{
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/* if card_points_to_nursery is set, card_points_to_aging must also be set. */
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static const cell card_points_to_nursery = 0x80;
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static const cell card_points_to_aging = 0x40;
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static const cell card_mark_mask = (card_points_to_nursery | card_points_to_aging);
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typedef u8 card;
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static const cell card_bits = 8;
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static const cell card_size = (1<<card_bits);
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static const cell addr_card_mask = (card_size-1);
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inline static card *addr_to_card(cell a)
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{
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return (card*)(((cell)(a) >> card_bits) + cards_offset);
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}
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inline static cell card_to_addr(card *c)
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{
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return ((cell)c - cards_offset) << card_bits;
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}
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inline static cell card_offset(card *c)
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{
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return *(c - (cell)data->cards + (cell)data->allot_markers);
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}
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typedef u8 card_deck;
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static const cell deck_bits = (card_bits + 10);
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static const cell deck_size = (1<<deck_bits);
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static const cell addr_deck_mask = (deck_size-1);
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inline static card_deck *addr_to_deck(cell a)
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{
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return (card_deck *)(((cell)a >> deck_bits) + decks_offset);
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}
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inline static cell deck_to_addr(card_deck *c)
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{
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return ((cell)c - decks_offset) << deck_bits;
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}
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inline static card *deck_to_card(card_deck *d)
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{
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return (card *)((((cell)d - decks_offset) << (deck_bits - card_bits)) + cards_offset);
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}
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static const cell invalid_allot_marker = 0xff;
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extern cell allot_markers_offset;
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inline static card *addr_to_allot_marker(object *a)
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{
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return (card *)(((cell)a >> card_bits) + allot_markers_offset);
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}
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/* the write barrier must be called any time we are potentially storing a
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pointer from an older generation to a younger one */
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inline static void write_barrier(object *obj)
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{
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*addr_to_card((cell)obj) = card_mark_mask;
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*addr_to_deck((cell)obj) = card_mark_mask;
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}
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/* we need to remember the first object allocated in the card */
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inline static void allot_barrier(object *address)
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{
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card *ptr = addr_to_allot_marker(address);
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if(*ptr == invalid_allot_marker)
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*ptr = ((cell)address & addr_card_mask);
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}
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}
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