(** * Properties of compile-time approximations of values *)
Definition val_match_approx (a: approx) (v: val) : Prop :=
match a with
| Int1 => v = Val.zero_ext 1 v
| Int7 => v = Val.zero_ext 8 v /\ v = Val.sign_ext 8 v
| Int8u => v = Val.zero_ext 8 v
| Int8s => v = Val.sign_ext 8 v
| Int15 => v = Val.zero_ext 16 v /\ v = Val.sign_ext 16 v
| Int16u => v = Val.zero_ext 16 v
| Int16s => v = Val.sign_ext 16 v
| Float32 => v = Val.singleoffloat v
| Any => True
end.
Remark undef_match_approx: forall a, val_match_approx a Vundef.

Lemma approx_unop_is_redundant_sound:
forall op a v,
Approx.unop_is_redundant op a = true ->
val_match_approx a v ->
eval_unop op v = Some v.