Hint Resolve regs_valid_nil: rtlg.

(* Specifications: *)
Lemma regs_valid_cons:
forall r1 rl s,
reg_valid r1 s -> regs_valid rl s -> regs_valid (r1 :: rl) s.
Lemma regs_valid_incr:
forall s1 s2 rl, state_incr s1 s2 -> regs_valid rl s1 -> regs_valid rl s2.