Corollary agree_set_mreg_parallel:
  forall ms sp rs r v v',
  agree ms sp rs ->
  Val.lessdef v v' ->
  agree (Regmap.set r v ms) sp (Pregmap.set (preg_of r) v' rs).

Lemma extcall_args_match: forall ms sp rs m m', agree ms sp rs -> Mem.extends m m' -> forall ll vl, list_forall2 (Mach.extcall_arg_pair ms m sp) ll vl -> exists vl', list_forall2 (Asm.extcall_arg_pair rs m') ll vl' /\ Val.lessdef_list vl vl'.