[Bug c/87868] testsuite/c-c++-common/pr60101.c with -O3 and ubsan

[hubicka at ucw dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87868

--- Comment #2 from Jan Hubicka <hubicka at ucw dot cz> ---
I am attaching testcase and patch I am lto-botstrapping now.  It copies
canonical from original type which is important for us to not lose TBAA
during ealry opts as well. 

typedef struct rtx_def *rtx;
typedef struct cselib_val_struct
{
  union
  {
  } u;
  struct elt_loc_list *locs;
}
cselib_val;
struct elt_loc_list
{
  struct elt_loc_list *next;
  rtx loc;
};
static int n_useless_values;
unchain_one_elt_loc_list (pl)
     struct elt_loc_list **pl;
{
  struct elt_loc_list *l = *pl;
  *pl = l->next;
}

discard_useless_locs (x, info)
     void **x;
{
  cselib_val *v = (cselib_val *) * x;
  struct elt_loc_list **p = &v->locs;
  int had_locs = v->locs != 0;
  while (*p)
    {
      unchain_one_elt_loc_list (p);
      p = &(*p)->next;
    }
  if (had_locs && v->locs == 0)
    {
      n_useless_values++;
    }
}
        * tree.c (fld_incomplete_type_of): Copy type_canonical.
Index: tree.c
===================================================================
--- tree.c      (revision 265712)
+++ tree.c      (working copy)
@@ -5146,6 +5146,7 @@ fld_incomplete_type_of (tree t, struct f
          else
            first = build_reference_type_for_mode (t2, TYPE_MODE (t),
                                                TYPE_REF_CAN_ALIAS_ALL (t));
+         TYPE_CANONICAL (first) = TYPE_CANONICAL (TYPE_MAIN_VARIANT (t));
          add_tree_to_fld_list (first, fld);
          return fld_type_variant (first, t, fld);
        }