Ltac InvEval :=
  match goal with
  | [ H: None = Some _ |- _ ] => discriminate
  | [ H: Some _ = Some _ |- _ ] => inv H; InvEval
  | [ H: match ?x with Some _ => _ | None => _ end = Some _ |- _ ] => destruct x eqn:?; InvEval
  | [ H: match ?x with true => _ | false => _ end = Some _ |- _ ] => destruct x eqn:?; InvEval
  | _ => idtac
  end.

Lemma make_absfloat_correct: forall a tya c va v e le m, sem_absfloat va tya = Some v -> make_absfloat a tya = OK c -> eval_expr ge e le m a va -> eval_expr ge e le m c v.