(** 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.

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.