factor/vm/write_barrier.hpp

30 lines
926 B
C++
Executable File

/* 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. */
static const cell card_points_to_nursery = 0x80;
static const cell card_points_to_aging = 0x40;
static const cell card_mark_mask = (card_points_to_nursery | card_points_to_aging);
typedef u8 card;
static const cell card_bits = 8;
static const cell card_size = (1<<card_bits);
static const cell addr_card_mask = (card_size-1);
typedef u8 card_deck;
static const cell deck_bits = (card_bits + 10);
static const cell deck_size = (1<<deck_bits);
static const cell addr_deck_mask = (deck_size-1);
static const cell invalid_allot_marker = 0xff;
}