gc tweek for lists

[Richard Henderson <rth at cygnus dot com>]

The following allows an Alpha to make it into stage1 with ggc _on_
in the C front end.  This surely isn't the cleanest way to do this,
but it is late.  ;-P

Mark, during testing I would suggest 

@@ -637,7 +642,7 @@ ggc_collect ()
   struct ggc_status *gs;
   int time, n_rtxs, n_trees, n_vecs, n_strings;
 
-#ifndef ENABLE_CHECKING
+#if 0
   /* See if it's even worth our while.  */
   if (ggc_chain->bytes_alloced_since_gc < 64*1024)
     return;

as that does catch all sorts of missing roots that might 
ordinarily slip by.


r~


        * lists.c: Include ggc.h.
        (zap_lists): New.
        (init_EXPR_INSN_LIST_cache): Install it.

Index: lists.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/lists.c,v
retrieving revision 1.2
retrieving revision 1.3
diff -c -p -d -r1.2 -r1.3
*** lists.c	1999/09/04 15:08:55	1.2
--- lists.c	1999/09/08 11:46:28	1.3
*************** Boston, MA 02111-1307, USA.  */
*** 22,27 ****
--- 22,28 ----
  #include "system.h"
  #include "toplev.h"
  #include "rtl.h"
+ #include "ggc.h"
  
  /* Functions for maintaining cache-able lists of EXPR_LIST and INSN_LISTs.  */
  
*************** alloc_EXPR_LIST (kind, val, next)
*** 104,112 ****
--- 105,129 ----
  }
  
  /* This function will initialize the EXPR_LIST and INSN_LIST caches.  */
+ 
+ static void
+ zap_lists (dummy)
+      void *dummy ATTRIBUTE_UNUSED;
+ {
+   unused_expr_list = NULL;
+   unused_insn_list = NULL;
+ }
+ 
  void 
  init_EXPR_INSN_LIST_cache ()
  {
+   static int initialized;
+   if (!initialized)
+     {
+       initialized = 1;
+       ggc_add_root (&unused_expr_list, 1, 1, zap_lists);
+     }
+     
    unused_expr_list = NULL;
    unused_insn_list = NULL;
  }