[project @ 2001-07-30 12:57:01 by simonmar]

Small perf. improvement: use the next bit in the bitmap to indicate
whether the current object needs to be pushed into the next block
during compaction.  This saves having to do the double traversal of
the threaded info pointer list during the second pass in most cases.

diff --git a/ghc/rts/GCCompact.c b/ghc/rts/GCCompact.c
index b3f4fb7..9ddd414 100644 (file)
--- a/ghc/rts/GCCompact.c
+++ b/ghc/rts/GCCompact.c
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: GCCompact.c,v 1.4 2001/07/25 11:55:57 simonmar Exp $
+ * $Id: GCCompact.c,v 1.5 2001/07/30 12:57:01 simonmar Exp $
  *
  * (c) The GHC Team 2001
  *
@@ -723,8 +723,15 @@ update_fwd_compact( bdescr *blocks )
 
            size = p - q;
            if (free + size > free_bd->start + BLOCK_SIZE_W) {
+               // unset the next bit in the bitmap to indicate that
+               // this object needs to be pushed into the next
+               // block.  This saves us having to run down the
+               // threaded info pointer list twice during the next pass.
+               unmark(q+1,bd);
                free_bd = free_bd->link;
                free = free_bd->start;
+           } else {
+               ASSERT(is_marked(q+1,bd));
            }
 
            unthread(q,free);
@@ -784,15 +791,7 @@ update_bkwd_compact( step *stp )
            }
 #endif
 
-           // must unthread before we look at the info ptr...
-           info = get_threaded_info(p);
-
-           ASSERT(p && (LOOKS_LIKE_GHC_INFO(info)
-                        || IS_HUGS_CONSTR_INFO(info)));
-
-           size = obj_sizeW((StgClosure *)p,info);
-
-           if (free + size > free_bd->start + BLOCK_SIZE_W) {
+           if (!is_marked(p+1,bd)) {
                // don't forget to update the free ptr in the block desc.
                free_bd->free = free;
                free_bd = free_bd->link;
@@ -801,6 +800,12 @@ update_bkwd_compact( step *stp )
            }
 
            unthread(p,free);
+           info = get_itbl((StgClosure *)p);
+           size = obj_sizeW((StgClosure *)p,info);
+
+           ASSERT(p && (LOOKS_LIKE_GHC_INFO(info)
+                        || IS_HUGS_CONSTR_INFO(info)));
+
            if (free != p) {
                move(free,p,size);
            }