void
MR_new_trail_segment(void)
{
MR_MemoryZones *list;
MR_MemoryZone *new_zone;
MR_TrailEntry *old_trail_ptr;
old_trail_ptr = MR_trail_ptr;
/*
** We perform explicit overflow checks so redzones just waste space.
*/
new_zone = MR_create_or_reuse_zone("trail_segment", MR_trail_size, 0,
0, MR_default_handler);
list = MR_GC_malloc_uncollectable_attrib(sizeof(MR_MemoryZones),
MR_ALLOC_SITE_RUNTIME);
#if defined(MR_DEBUG_TRAIL_SEGMENTS)
printf("create new trail segment: old zone: %p, old trail_ptr %p\n",
MR_TRAIL_ZONE, MR_trail_ptr);
#endif
list->MR_zones_head = MR_TRAIL_ZONE;
list->MR_zones_tail = MR_PREV_TRAIL_ZONES;
MR_PREV_TRAIL_ZONES = list;
MR_TRAIL_ZONE = new_zone;
MR_trail_ptr = (MR_TrailEntry *) MR_TRAIL_ZONE->MR_zone_min;
#if defined(MR_DEBUG_TRAIL_SEGMENTS)
printf("create new trail segment: new zone: %p, new trail_ptr %p\n",
MR_TRAIL_ZONE, MR_trail_ptr);
#endif
}
MR_Word *
MR_new_detstack_segment(MR_Word *sp, int n)
{
MR_Word *old_sp;
MR_MemoryZones *list;
MR_MemoryZone *new_zone;
old_sp = sp;
// We perform explicit overflow checks so redzones just waste space.
new_zone = MR_create_or_reuse_zone("detstack_segment",
MR_detstack_size, 0, 0, MR_default_handler);
list = MR_GC_malloc_uncollectable_attrib(sizeof(MR_MemoryZones),
MR_ALLOC_SITE_RUNTIME);
#ifdef MR_DEBUG_STACK_SEGMENTS
// If you ever need to debug this again, you will probably want to
// change this debugging code to include the information printed out
// by MR_new_nondetstack_segment() below.
MR_debug_log_message(
"create new det segment: old zone: %p, old sp %p, old succip %p",
MR_CONTEXT(MR_ctxt_detstack_zone), old_sp, MR_succip);
#endif
list->MR_zones_head = MR_CONTEXT(MR_ctxt_detstack_zone);
list->MR_zones_tail = MR_CONTEXT(MR_ctxt_prev_detstack_zones);
MR_CONTEXT(MR_ctxt_prev_detstack_zones) = list;
MR_CONTEXT(MR_ctxt_detstack_zone) = new_zone;
MR_CONTEXT(MR_ctxt_sp) = MR_CONTEXT(MR_ctxt_detstack_zone)->MR_zone_min;
MR_sp_word = (MR_Word) MR_CONTEXT(MR_ctxt_sp);
MR_incr_sp_leaf(2);
MR_stackvar(1) = (MR_Word) old_sp;
MR_stackvar(2) = (MR_Word) MR_succip;
// This may not be for a leaf procedure; we abuse the macro to avoid
// a check for whether we have run out of the new detstack segment.
//
// XXX It is *theoretically* possible for a single stack frame to need
// more memory than is available in the whole of the new segment.
// However, if this is true, then the program is screwed anyway.
// We cannot save it, though we *could* give a meaningful error message
// instead of just leaving the program to crash.
MR_incr_sp_leaf(n);
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message(
"create new det segment: new zone: %p, new sp %p new succip: %p",
MR_CONTEXT(MR_ctxt_detstack_zone), MR_sp,
MR_ENTRY(MR_pop_detstack_segment));
#endif
return MR_sp;
}
MR_Word *
MR_new_nondetstack_segment(MR_Word *maxfr, int incr)
{
MR_Word *sentinel_maxfr;
MR_Word *old_maxfr;
MR_Word *old_curfr;
MR_MemoryZone *new_cur_zone;
MR_MemoryZones *new_prev_zones;
old_maxfr = maxfr;
old_curfr = MR_curfr;
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("\nadding new nondet stack segment");
printf("\ncontext: %p", &MR_ENGINE(MR_eng_context));
printf("\nold maxfr: ");
MR_printnondetstack(stdout, old_maxfr);
printf("\nold curfr: ");
MR_printnondetstack(stdout, old_curfr);
printf("\n");
#endif
new_cur_zone = MR_rewind_nondetstack_segments(maxfr);
if (new_cur_zone == NULL) {
// There is no old segment to reuse in the nondet stack itself,
// so allocate a new one (possibly one that was freed earlier).
//
// Note that we perform explicit overflow checks, so redzones
// would just waste space.
new_cur_zone = MR_create_or_reuse_zone("nondetstack_segment",
MR_nondetstack_size, 0, 0, MR_default_handler);
}
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("\nbefore creating new nondet segment:\n");
MR_print_zone(stdout, MR_CONTEXT(MR_ctxt_nondetstack_zone));
printf("\n");
#endif
new_prev_zones = MR_GC_malloc_uncollectable_attrib(sizeof(MR_MemoryZones),
MR_ALLOC_SITE_RUNTIME);
new_prev_zones->MR_zones_head = MR_CONTEXT(MR_ctxt_nondetstack_zone);
new_prev_zones->MR_zones_tail = MR_CONTEXT(MR_ctxt_prev_nondetstack_zones);
MR_CONTEXT(MR_ctxt_prev_nondetstack_zones) = new_prev_zones;
MR_CONTEXT(MR_ctxt_nondetstack_zone) = new_cur_zone;
MR_CONTEXT(MR_ctxt_maxfr) = new_cur_zone->MR_zone_min;
MR_maxfr_word = (MR_Word) MR_CONTEXT(MR_ctxt_maxfr);
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("\nafter creating new nondet segment\n");
printf("new maxfr: ");
MR_printnondetstack(stdout, MR_maxfr);
printf("\nnew cur zone:\n");
MR_print_zone(stdout, MR_CONTEXT(MR_ctxt_nondetstack_zone));
printf("new prev zones:\n");
MR_print_zones(stdout, MR_CONTEXT(MR_ctxt_prev_nondetstack_zones));
printf("\n");
fflush(stdout);
#endif
// The stack trace tracing code needs to know the size of each nondet
// stack frame, since it uses the size to classify frames as temp or
// ordinary. The size is given by the difference in address between
// the address of the frame and the address of the previous frame.
// This difference would yield an incorrect size and hence an incorrect
// frame classification if a temp frame were allowed to have a frame
// on a different segment as its immediate predecessor.
//
// We prevent this by putting an ordinary (i.e. non-temp) frame at the
// bottom of every new nondet stack segment as a sentinel. We hand-build
// this frame, since it is not an "ordinary" ordinary frame. It is not
// created by a call, so it has no meaningful success continuation,
// and since it does not make any calls, no other frame's success
// continuation can point to it either.
//
// We store three pieces of information in the sentinel frame.
//
// - The maxfr at the time the sentinel frame was created, which we store
// in the prevfr slot. This is actually the address of the logically
// previous frame, so we are using the slot for its intended purpose,
// but the difference between the addresses of the two frames is NOT
// the size of the sentinel frame.
//
// - The curfr at the time the sentinel frame was created, which we store
// in the succfr slot. This is NOT actually the frame of the success
// continuation; we can store it there because this frame HAS no
// meaningful success continuation, so the slot is not needed for its
// intended purpose.
//
// - The address of the MR_MemoryZone structure of the zone containing
// the sentinel frame, which we store in framevar 1. This is used by
// the code of MR_pop_nondetstack_segment.
sentinel_maxfr = MR_maxfr + (MR_NONDET_FIXED_SIZE + 1);
MR_prevfr_slot_word(sentinel_maxfr) = (MR_Word) old_maxfr;
MR_succfr_slot_word(sentinel_maxfr) = (MR_Word) old_curfr;
MR_succip_slot_word(sentinel_maxfr) =
(MR_Word) MR_ENTRY(MR_do_not_reached);
MR_redofr_slot_word(sentinel_maxfr) = (MR_Word) sentinel_maxfr;
MR_redoip_slot_word(sentinel_maxfr) =
(MR_Word) MR_ENTRY(MR_pop_nondetstack_segment);
MR_based_framevar(sentinel_maxfr, 1) = (MR_Word) new_cur_zone;
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("creating sentinel frame:\n");
printf("sentinel_maxfr: ");
MR_printnondetstack(stdout, sentinel_maxfr);
printf("\nsentinel frame's prevfr slot: ");
MR_printnondetstack(stdout, MR_prevfr_slot(sentinel_maxfr));
printf("\nsentinel frame's succfr slot: ");
MR_printnondetstack(stdout, MR_succfr_slot(sentinel_maxfr));
printf("\nsentinel frame's redofr slot: ");
MR_printnondetstack(stdout, MR_redofr_slot(sentinel_maxfr));
printf("\n");
#endif
// Reserve space for the new nondet stack frame on top of the
// sentinel frame.
MR_maxfr_word = (MR_Word) (sentinel_maxfr + incr);
#ifdef MR_DEBUG_STACK_SEGMENTS
printf("after creating sentinel frame and reserving %d words:\n", incr);
printf("new maxfr: ");
MR_printnondetstack(stdout, MR_maxfr);
printf("\n");
fflush(stdout);
#endif
return MR_maxfr;
}
