(* *********************************************************************)
(*                                                                     *)
(*              The Compcert verified compiler                         *)
(*                                                                     *)
(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
(*           Prashanth Mundkur, SRI International                      *)
(*                                                                     *)
(*  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.     *)
(*                                                                     *)
(*  The contributions by Prashanth Mundkur are reused and adapted      *)
(*  under the terms of a Contributor License Agreement between         *)
(*  SRI International and INRIA.                                       *)
(*                                                                     *)
(* *********************************************************************)
(** Neededness analysis for RISC-V operators *)
Definition op1 (nv: nval) := nv :: nil.
Definition op2 (nv: nval) := nv :: nv :: nil.
Definition needs_of_condition (cond: condition): list nval := nil.
Definition needs_of_operation (op: operation) (nv: nval): list nval :=
match op with
| Omove => op1 nv
| Ointconst n => nil
| Olongconst n => nil
| Ofloatconst n => nil
| Osingleconst n => nil
| Oaddrsymbol id ofs => nil
| Oaddrstack ofs => nil
| Ocast8signed => op1 (sign_ext 8 nv)
| Ocast16signed => op1 (sign_ext 16 nv)
| Oadd => op2 (modarith nv)
| Oaddimm n => op1 (modarith nv)
| Oneg => op1 (modarith nv)
| Osub => op2 (default nv)
| Omul => op2 (modarith nv)
| Omulhs | Omulhu | Odiv | Odivu | Omod | Omodu => op2 (default nv)
| Oand => op2 (bitwise nv)
| Oandimm n => op1 (andimm nv n)
| Oor => op2 (bitwise nv)
| Oorimm n => op1 (orimm nv n)
| Oxor => op2 (bitwise nv)
| Oxorimm n => op1 (bitwise nv)
| Oshl | Oshr | Oshru => op2 (default nv)
| Oshlimm n => op1 (shlimm nv n)
| Oshrimm n => op1 (shrimm nv n)
| Oshruimm n => op1 (shruimm nv n)
| Oshrximm n => op1 (default nv)
| Omakelong => op2 (default nv)
| Olowlong | Ohighlong => op1 (default nv)
| Ocast32signed => op1 (default nv)
| Ocast32unsigned => op1 (default nv)
| Oaddl => op2 (default nv)
| Oaddlimm n => op1 (default nv)
| Onegl => op1 (default nv)
| Osubl => op2 (default nv)
| Omull => op2 (default nv)
| Omullhs | Omullhu | Odivl | Odivlu | Omodl | Omodlu => op2 (default nv)
| Oandl => op2 (default nv)
| Oandlimm n => op1 (default nv)
| Oorl => op2 (default nv)
| Oorlimm n => op1 (default nv)
| Oxorl => op2 (default nv)
| Oxorlimm n => op1 (default nv)
| Oshll | Oshrl | Oshrlu => op2 (default nv)
| Oshllimm n => op1 (default nv)
| Oshrlimm n => op1 (default nv)
| Oshrluimm n => op1 (default nv)
| Oshrxlimm n => op1 (default nv)
| Onegf | Oabsf => op1 (default nv)
| Oaddf | Osubf | Omulf | Odivf => op2 (default nv)
| Onegfs | Oabsfs => op1 (default nv)
| Oaddfs | Osubfs | Omulfs | Odivfs => op2 (default nv)
| Ofloatofsingle | Osingleoffloat => op1 (default nv)
| Ointoffloat | Ointuoffloat | Ofloatofint | Ofloatofintu => op1 (default nv)
| Olongoffloat | Olonguoffloat | Ofloatoflong | Ofloatoflongu => op1 (default nv)
| Ointofsingle | Ointuofsingle | Osingleofint | Osingleofintu => op1 (default nv)
| Olongofsingle | Olonguofsingle | Osingleoflong | Osingleoflongu => op1 (default nv)
| Ocmp c => needs_of_condition c
end.
Definition operation_is_redundant (op: operation) (nv: nval): bool :=
match op with
| Ocast8signed => sign_ext_redundant 8 nv
| Ocast16signed => sign_ext_redundant 16 nv
| Oandimm n => andimm_redundant nv n
| Oorimm n => orimm_redundant nv n
| _ => false
end.
Ltac InvAgree :=
match goal with
| [H: vagree_list nil _ _ |- _ ] => inv H; InvAgree
| [H: vagree_list (_::_) _ _ |- _ ] => inv H; InvAgree
| _ => idtac
end.
Ltac TrivialExists :=
match goal with
| [ |- exists v, Some ?x = Some v /\ _ ] => exists x; split; auto
| _ => idtac
end.
Section SOUNDNESS.
Variable ge: genv.
Variable sp: block.
Variables m m': mem.
Hypothesis PERM: forall b ofs k p, Mem.perm m b ofs k p -> Mem.perm m' b ofs k p.

Lemma needs_of_operation_sound:
forall op args v nv args',
eval_operation ge (Vptr sp Ptrofs.zero) op args m = Some v ->
vagree_list args args' (needs_of_operation op nv) ->
nv <> Nothing ->
exists v',
eval_operation ge (Vptr sp Ptrofs.zero) op args' m' = Some v'
/\ vagree v v' nv.