(** ** Properties of [load]. *)

(* Specifications: *)
(** A load succeeds if and only if the access is valid for reading *)
Axiom valid_access_load:
forall m chunk b ofs,
valid_access m chunk b ofs Readable ->
exists v, load chunk m b ofs = Some v.
Axiom load_valid_access:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
valid_access m chunk b ofs Readable.
(** The value returned by [load] belongs to the type of the memory quantity accessed: [Vundef], [Vint] or [Vptr] for an integer quantity, [Vundef] or [Vfloat] for a float quantity. *)
Axiom load_type:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
Val.has_type v (type_of_chunk chunk).
(** For a small integer or float type, the value returned by [load] is invariant under the corresponding cast. *)
Axiom load_cast:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
match chunk with
| Mint8signed => v = Val.sign_ext 8 v
| Mint8unsigned => v = Val.zero_ext 8 v
| Mint16signed => v = Val.sign_ext 16 v
| Mint16unsigned => v = Val.zero_ext 16 v
| _ => True
end.
Axiom load_int8_signed_unsigned:
forall m b ofs,
load Mint8signed m b ofs = option_map (Val.sign_ext 8) (load Mint8unsigned m b ofs).
Axiom load_int16_signed_unsigned:
forall m b ofs,
load Mint16signed m b ofs = option_map (Val.sign_ext 16) (load Mint16unsigned m b ofs).
(** A load succeeds if and only if the access is valid for reading *)
Axiom valid_access_load:
forall m chunk b ofs,
valid_access m chunk b ofs Readable ->
exists v, load chunk m b ofs = Some v.
Axiom load_valid_access:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
valid_access m chunk b ofs Readable.
(** The value returned by [load] belongs to the type of the memory quantity accessed: [Vundef], [Vint] or [Vptr] for an integer quantity, [Vundef] or [Vfloat] for a float quantity. *)
Axiom load_type:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
Val.has_type v (type_of_chunk chunk).
(** For a small integer or float type, the value returned by [load] is invariant under the corresponding cast. *)
Axiom load_cast:
forall m chunk b ofs v,
load chunk m b ofs = Some v ->
match chunk with
| Mint8signed => v = Val.sign_ext 8 v
| Mint8unsigned => v = Val.zero_ext 8 v
| Mint16signed => v = Val.sign_ext 16 v
| Mint16unsigned => v = Val.zero_ext 16 v
| _ => True
end.
Axiom load_int8_signed_unsigned:
forall m b ofs,
load Mint8signed m b ofs = option_map (Val.sign_ext 8) (load Mint8unsigned m b ofs).
Axiom load_int16_signed_unsigned:
forall m b ofs,
load Mint16signed m b ofs = option_map (Val.sign_ext 16) (load Mint16unsigned m b ofs).