87 lines
2.1 KiB
C++
Executable File
87 lines
2.1 KiB
C++
Executable File
/* 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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#define CARD_POINTS_TO_NURSERY 0x80
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#define CARD_POINTS_TO_AGING 0x40
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#define CARD_MARK_MASK (CARD_POINTS_TO_NURSERY | CARD_POINTS_TO_AGING)
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typedef u8 card;
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#define CARD_BITS 8
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#define CARD_SIZE (1<<CARD_BITS)
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#define 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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#define DECK_BITS (CARD_BITS + 10)
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#define DECK_SIZE (1<<DECK_BITS)
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#define 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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#define INVALID_ALLOT_MARKER 0xff
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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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