(** Neededness analysis for PowerPC operators *)
Definition op1 (nv: nval) := nv :: nil.
Definition op2 (nv: nval) := nv :: nv :: nil.
Definition needs_of_condition (cond: condition): list nval :=
match cond with
| Cmaskzero n | Cmasknotzero n => op1 (maskzero n)
| _ => nil
end.
Definition needs_of_operation (op: operation) (nv: nval): list nval :=
match op with
| Omove => op1 nv
| Ointconst 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)
| Oaddsymbol id ofs => op1 (modarith nv)
| Osub => op2 (default nv)
| Osubimm n => op1 (default nv)
| Omul => op2 (modarith nv)
| Omulimm n => op1 (modarith nv)
| Omulhs | Omulhu | Odiv | Odivu => 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)
| Onot => op1 (bitwise nv)
| Onand | Onor | Onxor | Oandc | Oorc => op2 (bitwise nv)
| Oshl | Oshr | Oshru => op2 (default nv)
| Oshrimm n => op1 (shrimm nv n)
| Oshrximm n => op1 (default nv)
| Orolm amount mask => op1 (rolm nv amount mask)
| Oroli amount mask => op1 (default nv)
| Olongconst n => nil
| Ocast32signed | Ocast32unsigned | Onegl | Onotl => op1 (default nv)
| Oaddl | Osubl | Omull | Omullhs | Omullhu | Odivl | Odivlu | Oandl | Oorl | Oxorl | Oshll | Oshrl | Oshrlu => op2 (default nv)
| Oaddlimm _ | Oandlimm _ | Oorlimm _ | Oxorlimm _ | Oshrlimm _ | Oshrxlimm _=> op1 (default nv)
| Orolml _ _ | Olongoffloat | Ofloatoflong => 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)
| Osingleoffloat | Ofloatofsingle => op1 (default nv)
| Ointoffloat | Ointuoffloat | Ofloatofint | Ofloatofintu => op1 (default nv)
| Ofloatofwords | Omakelong => op2 (default nv)
| Olowlong | Ohighlong => 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
| Orolm amount mask => rolm_redundant nv amount mask
| _ => 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 operation_is_redundant_sound:
forall op nv arg1 args v arg1' args',
operation_is_redundant op nv = true ->
eval_operation ge (Vptr sp Ptrofs.zero) op (arg1 :: args) m = Some v ->
vagree_list (arg1 :: args) (arg1' :: args') (needs_of_operation op nv) ->
vagree v arg1' nv.