Remark decompose_cmpl_eq_zero:
forall h l,
Int64.eq (Int64.ofwords h l) Int64.zero = Int.eq (Int.or h l) Int.zero.

Lemma eval_cmpl_eq_zero:
forall le a x,
eval_expr ge sp e m le a (Vlong x) ->
eval_expr ge sp e m le (cmpl_eq_zero a) (Val.of_bool (Int64.eq x Int64.zero)).