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_arguments_match: forall ms m m' sp rs sg args, agree ms sp rs -> Mem.extends m m' -> Mach.extcall_arguments ms m sp sg args -> exists args', Asm.extcall_arguments rs m' sg args' /\ Val.lessdef_list args args'.