Remark agree_regs_init:
  forall F ctx rs, agree_regs F ctx (Regmap.init Vundef) rs.

Lemma agree_regs_init_regs: forall F ctx rl vl vl', Val.inject_list F vl vl' -> (forall r, In r rl -> Ple r ctx.(mreg)) -> agree_regs F ctx (init_regs vl rl) (init_regs vl' (sregs ctx rl)).