vm/object_start_map.cpp

   1 #include "master.hpp"
   2
   3 namespace factor {
   4
   5 object_start_map::object_start_map(cell size, cell start)
   6     : size(size), start(start) {
   7   cell card_count = size / card_size;
   8   object_start_offsets = new card[card_count];
   9   object_start_offsets_end = object_start_offsets + card_count;
  10   clear_object_start_offsets();
  11 }
  12
  13 object_start_map::~object_start_map() { delete[] object_start_offsets; }
  14
  15 cell object_start_map::find_object_containing_card(cell card_index) {
  16   if (card_index == 0)
  17     return start;
  18   card_index--;
  19
  20   while (object_start_offsets[card_index] == card_starts_inside_object) {
  21     // First card should start with an object
  22     FACTOR_ASSERT(card_index > 0);
  23     card_index--;
  24   }
  25   return start + card_index * card_size + object_start_offsets[card_index];
  26 }
  27
  28 // we need to remember the first object allocated in the card
  29 void object_start_map::record_object_start_offset(object* obj) {
  30   cell idx = addr_to_card((cell)obj - start);
  31   card obj_start = ((cell)obj & addr_card_mask);
  32   object_start_offsets[idx] = std::min(object_start_offsets[idx], obj_start);
  33 }
  34
  35 void object_start_map::clear_object_start_offsets() {
  36   memset(object_start_offsets, card_starts_inside_object, addr_to_card(size));
  37 }
  38
  39 void object_start_map::update_card_for_sweep(cell index, uint16_t mask) {
  40   cell offset = object_start_offsets[index];
  41   if (offset != card_starts_inside_object) {
  42     mask >>= (offset / data_alignment);
  43
  44     if (mask == 0) {
  45       // The rest of the block after the old object start is free
  46       object_start_offsets[index] = card_starts_inside_object;
  47     } else {
  48       // Move the object start forward if necessary
  49       object_start_offsets[index] =
  50           (card)(offset + (rightmost_set_bit(mask) * data_alignment));
  51     }
  52   }
  53 }
  54
  55 void object_start_map::update_for_sweep(mark_bits* state) {
  56   for (cell index = 0; index < state->bits_size; index++) {
  57     cell mask = state->marked[index];
  58 #ifdef FACTOR_64
  59     update_card_for_sweep(index * 4, mask & 0xffff);
  60     update_card_for_sweep(index * 4 + 1, (mask >> 16) & 0xffff);
  61     update_card_for_sweep(index * 4 + 2, (mask >> 32) & 0xffff);
  62     update_card_for_sweep(index * 4 + 3, (mask >> 48) & 0xffff);
  63 #else
  64     update_card_for_sweep(index * 2, mask & 0xffff);
  65     update_card_for_sweep(index * 2 + 1, (mask >> 16) & 0xffff);
  66 #endif
  67   }
  68 }
  69
  70 }