Definition sintv (v: aval) : Z * Z :=
match v with
| I n => (Int.signed n, Int.signed n)
| Uns _ n =>
if zlt n Int.zwordsize then (0, two_p n - 1) else (Int.min_signed, Int.max_signed)
| Sgn _ n =>
if zlt n Int.zwordsize
then (let x := two_p (n-1) in (-x, x-1))
else (Int.min_signed, Int.max_signed)
| _ => (Int.min_signed, Int.max_signed)
end.

Lemma sintv_sound:
forall n v, vmatch (Vint n) v -> fst (sintv v) <= Int.signed n <= snd (sintv v).