[project @ 1999-06-29 12:00:42 by simonmar]

[ghc-hetmet.git] / ghc / rts / Stable.c

diff --git a/ghc/rts/Stable.c b/ghc/rts/Stable.c
index b4021b6..4244bca 100644 (file)
--- a/ghc/rts/Stable.c
+++ b/ghc/rts/Stable.c
@@ -1,7 +1,7 @@
 /* -----------------------------------------------------------------------------
- * $Id: Stable.c,v 1.1 1999/01/27 10:11:27 simonm Exp $
+ * $Id: Stable.c,v 1.4 1999/03/08 16:41:24 sof Exp $
  *
- * (c) The GHC Team 1998-1999
+ * (c) The GHC Team, 1998-1999
  *
  * Stable names and stable pointers.
  *
@@ -133,7 +133,9 @@ initFreeList(snEntry *table, nat n, snEntry *free)
   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;
@@ -170,6 +172,7 @@ lookupStableName(StgPtr p)
     (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)); */
     
@@ -183,6 +186,7 @@ lookupStableName(StgPtr p)
 static inline void
 freeStableName(snEntry *sn)
 {
+  ASSERT(sn->sn_obj == NULL);
   sn->addr = (P_)stable_ptr_free;
   stable_ptr_free = sn;
 }
@@ -224,7 +228,7 @@ enlargeStablePtrTable(void)
     stable_ptr_table = stgMallocWords(SPT_size * sizeof(snEntry), 
                                      "initStablePtrTable");
     
-    initFreeList(stable_ptr_table+1,INIT_SPT_SIZE-1,NULL);
+    initFreeList(stable_ptr_table,INIT_SPT_SIZE,NULL);
     addrToStableHash = allocHashTable();
   }
   else {
@@ -266,26 +270,23 @@ markStablePtrTable(rtsBool full)
    */
   for (p = stable_ptr_table; 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));
+         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));
       }
     }
   }
@@ -297,10 +298,12 @@ markStablePtrTable(rtsBool full)
  * 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
@@ -321,36 +324,40 @@ gcStablePtrTable(rtsBool full)
   end_stable_ptr_table = &stable_ptr_table[SPT_size];
 
   for (p = stable_ptr_table; p < end_stable_ptr_table; p++) {
-    q = p->addr;
 
+    /* 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) {
-           removeHashTable(addrToStableHash, (W_)q, NULL);
-           insertHashTable(addrToStableHash, (W_)new, (void *)(p - stable_ptr_table));
+         if (new != NULL) {
+           /* 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.
-          */
-         if (p->keep)
-           p->addr = NULL;
-         else
-           freeStableName(p);
-       }
       }
     }
   }