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(*              The Compcert verified compiler                         *)
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(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
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(*  Copyright Institut National de Recherche en Informatique et en     *)
(*  Automatique.  All rights reserved.  This file is distributed       *)
(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
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(** Abstract domain for neededness analysis *)
(** * Neededness for values *)
Inductive nval : Type :=
| Nothing              (**r value is entirely unused *)
| I (m: int)           (**r only need the bits that are 1 in [m] *)
| All.                 (**r every bit of the value is used *)
Definition eq_nval (x y: nval) : {x=y} + {x<>y}.
Hint Resolve vagree_same vagree_lessdef lessdef_vagree: na.
Inductive vagree_list: list val -> list val -> list nval -> Prop :=
| vagree_list_nil: forall nvl,
vagree_list nil nil nvl
| vagree_list_default: forall v1 vl1 v2 vl2,
vagree v1 v2 All -> vagree_list vl1 vl2 nil ->
vagree_list (v1 :: vl1) (v2 :: vl2) nil
| vagree_list_cons: forall v1 vl1 v2 vl2 nv1 nvl,
vagree v1 v2 nv1 -> vagree_list vl1 vl2 nvl ->
vagree_list (v1 :: vl1) (v2 :: vl2) (nv1 :: nvl).

Lemma lessdef_vagree_list:
forall vl1 vl2, vagree_list vl1 vl2 nil -> Val.lessdef_list vl1 vl2.