[Bug bootstrap/54876] New: [4.8 Regression] LTO bootstrap broken, streaming garbage-collected BLOCK

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54876



             Bug #: 54876

           Summary: [4.8 Regression] LTO bootstrap broken, streaming

                    garbage-collected BLOCK

    Classification: Unclassified

           Product: gcc

           Version: 4.8.0

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: bootstrap

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: rgue...@gcc.gnu.org

                CC: de...@gcc.gnu.org, jamb...@gcc.gnu.org





We are streaming a GCed TREE_BLOCK of



(gdb) p expr->base.code

$5 = MEM_REF

(gdb) p expr->base.code

$6 = ADDR_EXPR



from output_node_opt_summary here:



      /* At the moment we assume all old trees to be PARM_DECLs, because we

have no

         mechanism to store function local declarations into summaries.  */

      gcc_assert (parm);

      streamer_write_uhwi (ob, parm_num);

      gcc_assert (EXPR_LOCATION (map->new_tree) == UNKNOWN_LOCATION);

      stream_write_tree (ob, map->new_tree, true);



we need to clear all TREE_BLOCKs from this.  Not sure if new_tree originates

from a tree that eventually comes along prune_expression_for_jf, but



static tree

prune_expression_for_jf (tree exp)

{

  if (EXPR_P (exp))

    {

      exp = unshare_expr (exp);

      SET_EXPR_LOCATION (exp, UNKNOWN_LOCATION);

    }

  return exp;

}



is not enough.  You need to walk_tree exp, as in this case it is &MEM_REF

and all sub-expressions can contain a location.