Ltac simpl_of_lu :=
match goal with
| |- context [ of_lu (?f ?x) ] =>
rewrite (of_lu_eqn (f x)); simpl hd; simpl tl
end.

Lemma of_uint_acc_spec n d :
Nat.of_hex_uint_acc d n = of_lu (rev d) + n * 0x10^usize d.