static MR_MemoryZone *
MR_rewind_nondetstack_segments(MR_Word *maxfr)
{
MR_MemoryZone *zone_to_reuse;
MR_MemoryZone *zone;
MR_Word *limit;
MR_MemoryZones *list;
zone_to_reuse = NULL;
for (;;) {
zone = MR_CONTEXT(MR_ctxt_nondetstack_zone);
limit = (MR_Word *) zone->MR_zone_end;
if (maxfr >= zone->MR_zone_min && maxfr < limit) {
break;
}
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("\nfreeing zone\n");
MR_print_zone(stdout, zone);
#endif
// If there are several currently unneeded segments, this algorithm
// reuses the zone of the topmost segment (the first segment in the
// list from the top), since its contents are more likely to have been
// recently referred to, and thus more likely to be in the cache.
//
// However, reusing the zone of the bottom-most unneeded segment
// would look conceptually a bit neater in that it would preserve
// the follows/precedes relationship between the zones.
if (zone_to_reuse == NULL) {
zone_to_reuse = zone;
} else {
MR_release_zone(zone);
}
list = MR_CONTEXT(MR_ctxt_prev_nondetstack_zones);
assert(list != NULL);
MR_CONTEXT(MR_ctxt_nondetstack_zone) = list->MR_zones_head;
MR_CONTEXT(MR_ctxt_prev_nondetstack_zones) = list->MR_zones_tail;
MR_GC_free_attrib(list);
}
#ifdef MR_DEBUG_STACK_SEGMENTS
if (zone_to_reuse == NULL) {
printf("\nno old nondet segment zone available for reuse\n");
} else {
printf("\nreturning zone of old nondet segment for reuse: %p\n",
zone_to_reuse);
}
#endif
return zone_to_reuse;
}
static void
MR_pop_trail_segment(void)
{
MR_MemoryZones *list;
#if defined(MR_DEBUG_TRAIL_SEGMENTS)
printf("restore old trail segment: old zone %p, old trail_ptr %p\n",
MR_TRAIL_ZONE, MR_trail_ptr);
#endif
MR_release_zone(MR_TRAIL_ZONE);
list = MR_PREV_TRAIL_ZONES;
MR_TRAIL_ZONE = list->MR_zones_head;
MR_PREV_TRAIL_ZONES = list->MR_zones_tail;
MR_trail_ptr = (MR_TrailEntry *) MR_TRAIL_ZONE->MR_zone_end;
MR_GC_free(list);
#if defined(MR_DEBUG_TRAIL_SEGMENTS)
printf("restore old trail segment: new zone %p, new trail_ptr %p\n",
MR_TRAIL_ZONE, MR_trail_ptr);
#endif
}
