/* -----------------------------------------------------------------------------
- * $Id: Stable.c,v 1.2 1999/02/05 16:02:55 simonm Exp $
+ * $Id: Stable.c,v 1.11 2000/04/24 22:05:08 panne Exp $
*
* (c) The GHC Team, 1998-1999
*
snEntry *p;
for (p = table + n - 1; p >= table; p--) {
- p->addr = (P_)free;
+ p->addr = (P_)free;
+ p->weight = 0;
+ p->sn_obj = NULL;
free = p;
}
stable_ptr_free = table;
SPT_size = 0;
}
+/*
+ * get at the real stuff...remove indirections.
+ *
+ * ToDo: move to a better home.
+ */
+static
+StgClosure*
+removeIndirections(StgClosure* p)
+{
+ StgClosure* q = p;
+
+ while (get_itbl(q)->type == IND ||
+ get_itbl(q)->type == IND_STATIC ||
+ get_itbl(q)->type == IND_OLDGEN ||
+ get_itbl(q)->type == IND_PERM ||
+ get_itbl(q)->type == IND_OLDGEN_PERM ) {
+ q = ((StgInd *)q)->indirectee;
+ }
+ return q;
+}
+
StgWord
lookupStableName(StgPtr p)
{
if (stable_ptr_free == NULL) {
enlargeStablePtrTable();
}
-
+
+ /* removing indirections increases the likelihood
+ * of finding a match in the stable name
+ * hash table.
+ */
+ p = (StgPtr)removeIndirections((StgClosure*)p);
+
(void *)sn = lookupHashTable(addrToStableHash,(W_)p);
if (sn != 0) {
(P_)stable_ptr_free = stable_ptr_free->addr;
stable_ptr_table[sn].weight = 0;
stable_ptr_table[sn].addr = p;
+ stable_ptr_table[sn].sn_obj = NULL;
/* IF_DEBUG(stable,fprintf(stderr,"new stable name %d at
%p\n",sn,p)); */
static inline void
freeStableName(snEntry *sn)
{
+ ASSERT(sn->sn_obj == NULL);
+ if (sn->addr != NULL) {
+ removeHashTable(addrToStableHash, (W_)sn->addr, NULL);
+ }
sn->addr = (P_)stable_ptr_free;
stable_ptr_free = sn;
}
{
StgWord sn = lookupStableName(p);
StgWord weight, weight_2;
-
weight = stable_ptr_table[sn].weight;
if (weight == 0) {
- weight = 1 << (BITS_IN(StgWord)-1);
+ weight = (StgWord)1 << (BITS_IN(StgWord)-1);
stable_ptr_table[sn].weight = weight;
return (StgStablePtr)(sn + ((BITS_IN(StgWord)-1) << STABLEPTR_WEIGHT_SHIFT));
}
stable_ptr_table = stgMallocWords(SPT_size * sizeof(snEntry),
"initStablePtrTable");
+ /* we don't use index 0 in the stable name table, because that
+ * would conflict with the hash table lookup operations which
+ * return NULL if an entry isn't found in the hash table.
+ */
initFreeList(stable_ptr_table+1,INIT_SPT_SIZE-1,NULL);
addrToStableHash = allocHashTable();
}
end_stable_ptr_table = &stable_ptr_table[SPT_size];
- /* Mark all the stable *pointers* (not stable names)
+ /* Mark all the stable *pointers* (not stable names).
+ * _starting_ at index 1; index 0 is unused.
*/
- for (p = stable_ptr_table; p < end_stable_ptr_table; p++) {
+ for (p = stable_ptr_table+1; p < end_stable_ptr_table; p++) {
q = p->addr;
- /* internal pointers or NULL are free slots */
+ /* internal pointers or NULL are free slots
+ */
if (q && (q < (P_)stable_ptr_table || q >= (P_)end_stable_ptr_table)) {
if (p->weight != 0) {
new = MarkRoot((StgClosure *)q);
/* Update the hash table */
if (full) {
- insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+ insertHashTable(addrToStableHash, (W_)new,
+ (void *)(p - stable_ptr_table));
(StgClosure *)p->addr = new;
} else if ((P_)new != q) {
removeHashTable(addrToStableHash, (W_)q, NULL);
- insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+ if (!lookupHashTable(addrToStableHash, (W_)new)) {
+ insertHashTable(addrToStableHash, (W_)new,
+ (void *)(p - stable_ptr_table));
+ }
(StgClosure *)p->addr = new;
}
- /* IF_DEBUG(stable, fprintf(stderr,"Stable ptr %d still alive
- at %p, weight %d\n", p - stable_ptr_table, new,
- p->weight)); */
- }
- else {
- /* reset the keep flag */
- p->keep = rtsFalse;
+ IF_DEBUG(stable, fprintf(stderr,"Stable ptr %d still alive at %p, weight %d\n", p - stable_ptr_table, new, p->weight));
}
}
}
* A dead entry has:
*
* - a weight of zero (i.e. 2^32)
- * - a false keep flag
+ * - a dead sn_obj
*
- * The keep flag is set by the garbage collector whenever it
- * encounters a StableName object on the heap.
+ * Both of these conditions must be true in order to re-use the stable
+ * name table entry. We can re-use stable name table entries for live
+ * heap objects, as long as the program has no StableName objects that
+ * refer to the entry.
*
* The boolean argument 'full' indicates that a major collection is
* being done, so we might as well throw away the hash table and build
end_stable_ptr_table = &stable_ptr_table[SPT_size];
- for (p = stable_ptr_table; p < end_stable_ptr_table; p++) {
- q = p->addr;
+ /* NOTE: _starting_ at index 1; index 0 is unused. */
+ for (p = stable_ptr_table + 1; p < end_stable_ptr_table; p++) {
+
+ /* Update the pointer to the StableName object, if there is one */
+ if (p->sn_obj != NULL) {
+ p->sn_obj = isAlive(p->sn_obj);
+ }
+ q = p->addr;
if (q && (q < (P_)stable_ptr_table || q >= (P_)end_stable_ptr_table)) {
- /* We're only interested in Stable Names here. */
+ /* We're only interested in Stable Names here. The weight != 0
+ * case is handled in markStablePtrTable above.
+ */
if (p->weight == 0) {
- if (((StgClosure *)new = isAlive((StgClosure *)q))) {
+ if (p->sn_obj == NULL) {
+ /* StableName object is dead */
+ freeStableName(p);
+ IF_DEBUG(stable, fprintf(stderr,"GC'd Stable name %d\n", p - stable_ptr_table));
+ }
+ else {
+ (StgClosure *)new = isAlive((StgClosure *)q);
IF_DEBUG(stable, fprintf(stderr,"Stable name %d still alive at %p, weight %d\n", p - stable_ptr_table, new, p->weight));
- p->addr = new;
- /* Re-hash this stable name */
- if (full) {
- insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
- } else if (new != q) {
+ if (new == NULL) {
+ /* The target has been garbage collected. Remove its
+ * entry from the hash table.
+ */
removeHashTable(addrToStableHash, (W_)q, NULL);
- insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+
+ } else {
+ /* Target still alive, Re-hash this stable name
+ */
+ if (full) {
+ insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+ } else if (new != q) {
+ removeHashTable(addrToStableHash, (W_)q, NULL);
+ insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+ }
}
- }
- else {
- /* If there are still StableName objects in the heap
- * pointing to this entry (p->keep == rtsTrue), then
- * don't free the entry just yet.
+ /* finally update the address of the target to point to its
+ * new location.
*/
- if (p->keep)
- p->addr = NULL;
- else
- freeStableName(p);
+ p->addr = new;
}
}
}
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