Module NeedOp

Require Import Coqlib.
Require Import AST.
Require Import Integers.
Require Import Floats.
Require Import Values.
Require Import Memory.
Require Import Globalenvs.
Require Import Op.
Require Import NeedDomain.
Require Import RTL.

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)
  | 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 needs_of_condition_sound:
  forall cond args b args',
  eval_condition cond args m = Some b ->
  vagree_list args args' (needs_of_condition cond) ->
  eval_condition cond args' m' = Some b.
Proof.
  intros. destruct cond; simpl in H;
  try (eapply default_needs_of_condition_sound; eauto; fail);
  simpl in *; FuncInv; InvAgree.
- eapply maskzero_sound; eauto.
- destruct (Val.maskzero_bool v i) as [b'|] eqn:MZ; try discriminate.
  erewrite maskzero_sound; eauto.
Qed.

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.
Proof.
  unfold needs_of_operation; intros; destruct op; try (eapply default_needs_of_operation_sound; eauto; fail);
  simpl in *; FuncInv; InvAgree; TrivialExists.
- apply sign_ext_sound; auto. compute; auto.
- apply sign_ext_sound; auto. compute; auto.
- apply add_sound; auto.
- apply add_sound; auto with na.
- apply add_sound; auto with na.
- apply mul_sound; auto.
- apply mul_sound; auto with na.
- apply and_sound; auto.
- apply andimm_sound; auto.
- apply or_sound; auto.
- apply orimm_sound; auto.
- apply xor_sound; auto.
- apply xor_sound; auto with na.
- apply notint_sound; auto.
- apply notint_sound. apply and_sound; rewrite bitwise_idem; auto.
- apply notint_sound. apply or_sound; rewrite bitwise_idem; auto.
- apply notint_sound. apply xor_sound; rewrite bitwise_idem; auto.
- apply and_sound; auto. apply notint_sound; rewrite bitwise_idem; auto.
- apply or_sound; auto. apply notint_sound; rewrite bitwise_idem; auto.
- apply shrimm_sound; auto.
- apply rolm_sound; auto.
- destruct (eval_condition c args m) as [b|] eqn:EC; simpl in H2.
  erewrite needs_of_condition_sound by eauto.
  subst v; simpl. auto with na.
  subst v; auto with na.
Qed.

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.
Proof.
  intros. destruct op; simpl in *; try discriminate; inv H1; FuncInv; subst.
- apply sign_ext_redundant_sound; auto. omega.
- apply sign_ext_redundant_sound; auto. omega.
- apply andimm_redundant_sound; auto.
- apply orimm_redundant_sound; auto.
- apply rolm_redundant_sound; auto.
Qed.

End SOUNDNESS.