scheme48/c/bibop/area_roots.h

/*
 * Part of Scheme 48 1.9.  See file COPYING for notices and license.
 *
 * Authors: David Frese
 */

#ifndef __S48_AREA_ROOTS
#define __S48_AREA_ROOTS

#include "data.h"
#include "areas.h"
#include "memory.h"
#include "memory_map.h"
#include "scheme48.h"
#include "measure.h"

/* Cards & Dirty Vector */

#define S48_CARD_SIZE (1 << S48_LOG_CARD_SIZE)

void s48_init_dirty_vector(Area* area);
void s48_deinit_dirty_vector(Area* area);

void s48_trace_areas_roots(Area* areas);

/* implementation of the write-barrier */

void s48_set_dirty_vector(Area* area, s48_address addr, long stob,
			  Area* maybe_to_area);

/* Marks the card containing addr as dirty. called from
   s48_write_barrier and s48_internal_write_barrier */ 
inline static void s48_set_dirty_vector_inline(Area* area, s48_address addr,
					       long stob, Area* maybe_to_area)
{
#if S48_DIRTY_VECTOR_METHOD==S48_ADDRESS_DIRTY_VECTORS
  unsigned long area_offset = addr - area->start;
  unsigned int card_number = area_offset >> S48_LOG_CARD_SIZE ;
  s48_address current_dirty_address = area->dirty_vector.items[card_number];
  assert(card_number < area->dirty_vector.length);
  /* Only update if Nullpointer or smaller than current_dirty_address */
  if ((current_dirty_address == NULL) || (addr < current_dirty_address))
    area->dirty_vector.items[card_number] = addr;
#endif
}

S48_EXTERN void s48_write_barrier(long stob, s48_address address, long value);
S48_EXTERN char s48_stob_in_heapP(s48_value);

/* the value VALUE will be written at location ADDRESS which is within the stob STOB */
inline static void s48_write_barrier_inline(long stob, s48_address address,
					    long value) {
  /* The area of the stob */
  Area* area = s48_memory_map_ref(address);
#if (MEASURE_GC)
  if (S48_STOB_P(value)) {
    Area* meas_to_area  = s48_memory_map_ref(S48_ADDRESS_AT_HEADER(value)); 
    if (area->generation_index > meas_to_area->generation_index) {
      measure_write_barrier(1);
    } else {
      measure_write_barrier(0);
    }
  }
#endif
  /* Detect errors early... */
  if (S48_STOB_P(value)) {
    assert(s48_stob_in_heapP(value));
  }

  /* somehow the write_barrier gets called from some strange places --
     e.g. in read_image, that's why area can get NULL. */
  if (area == NULL)
    return;

  assert(address < area->frontier);

  if (area->generation_index == 0)
    return;
  
#if S48_WRITE_BARRIER_COMPLEXITY == S48_MUTATED_LOCATION
  s48_set_dirty_vector(area, address, value, NULL);
#else
    if (S48_STOB_P(value)) {
#if S48_WRITE_BARRIER_COMPLEXITY == S48_STOB_LOCATION
      s48_set_dirty_vector(area, address, value, NULL);
#elif S48_WRITE_BARRIER_COMPLEXITY == S48_INTERGEN_STOB_LOCATION
      Area* to_area = s48_memory_map_ref(S48_ADDRESS_AT_HEADER(value)); 
      
      if (area->generation_index > to_area->generation_index)
	s48_set_dirty_vector_inline(area, address, value, to_area); 
#endif
    }
#endif
}

/* called after a stob in AREA, stored at ADDR pointing into TO_AREA, has
   been updated, either because the object has been copied to a new
   area, a large area has been linked into a new list, or the object
   has been traced but ignored. */

inline static void s48_internal_write_barrier(Area* area, s48_address addr,
					      long value, Area* to_area) {
  /* we're not interested in locations in an other-space area. This
     test should be sufficient. This happens because of root-set
     functions, that trace a stob inside an area that is beeing
     collected (other-space). */
  if (area->action != GC_ACTION_IGNORE)
    return;
#if (S48_HAVE_TRANSPORT_LINK_CELLS)
  /* We could ignore the key field here for optimization, but maybe
     it's not worth the test. */
#endif
  /* We're only interested in pointers from old to young */
  if (area->generation_index > to_area->generation_index) {
#if (MEASURE_GC)
    measure_gc_write_barrier();
#endif
#if (S48_USE_REMEMBERED_SETS)
    /* if the rememberd-set can store this pointer, then we're done,
       otherwise mark the card anyway */
    if (s48_remset_add(addr, to_area->remset))
      return;
#endif
    s48_set_dirty_vector_inline(area, addr, value, to_area);
  }
}

#endif