unfold P in d_Si_eq_r_Si_eq. tauto. Qed.

(* Specifications: *)
Lemma r_Si_eq_lit :
_Z r_Si = (d_Si + l mod 2 ^ p) mod 2 ^ w.
Lemma r_Si_eq_a :
_Z r_Si = ( d_Si + (h mod M * 2 ^ w + l) mod 2 ^ p) mod 2 ^ w.