dep question in sched-deps.c

[p z]

Hello, 
 
    I am confused by following piece of code in sched-deps.c. My understanding 
is the last_pending_memory_flush only holds jumps, calls and memory write. So I 
think the two invocations of add_dependence should build true dependence, not 
anti. 
 
 
 
    for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
       {
  if (! NON_FLUSH_JUMP_P (u))
    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);     
<-----------------------
  else if (deps_may_trap_p (x))
    {
      if ((sched_deps_info->generate_spec_deps)
   && sel_sched_p () && (spec_info->mask & BEGIN_CONTROL))
        {
   ds_t ds = set_dep_weak (DEP_ANTI, BEGIN_CONTROL,
      MAX_DEP_WEAK);
   note_dep (XEXP (u, 0), ds);
        }
      else
        add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);   
<---------------------------
    }
       }
 
 
also, can you explain following comments in sched-deps.c. I don't quite 
understand what is means and what NON_FLUSH_JUMP_KIND is for.
 
/* In deps->last_pending_memory_flush marks JUMP_INSNs that weren't
   added to the list because of flush_pending_lists, stands just
   for itself and not for any other pending memory reads/writes.  */
 
 
 
I also need more dicussion about DEPS_LIST and INSN_LIST. Maxim once kindly 
explained to me,
"DEPS_LIST is a super-set of INSN_LIST. I kept INSN_LIST-style dependencies to 
avoid overhead on targets that don't need additional features of DEPS_LIST. Now 
that I look back at it, I should have removed INSN_LIST-style dependencies; I 
still hope to find time and clean that up (remove support for INSN_LIST-style 
dependencies).". But it is still over my head. my question is what is 
INSN_list-style dependencies? what is the extra feature of DEPS_LIST as a 
super-set of INSN_list?
 
thanks