Store a destination step in the block descriptor

At the moment, this just saves a memory reference in the GC inner loop
(worth a percent or two of GC time).  Later, it will hopefully let me
experiment with partial steps, and simplifying the generation/step
infrastructure.

1 files changed, 1 insertions, 2 deletions

diff --git a/rts/sm/GCUtils.c b/rts/sm/GCUtils.c
index 70c53cb8bf..7e99e29023 100644
--- a/rts/sm/GCUtils.c
+++ b/rts/sm/GCUtils.c
@@ -269,8 +269,7 @@ alloc_todo_block (step_workspace *ws, nat size)
         } else {
             bd = allocBlock_sync();
         }
-        bd->step = ws->step;
-        bd->gen_no = ws->step->gen_no;
+        initBdescr(bd, ws->step);
         bd->flags = BF_EVACUATED;
         bd->u.scan = bd->free = bd->start;
     }