(* *********************************************************************)
(*                                                                     *)
(*              The Compcert verified compiler                         *)
(*                                                                     *)
(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
(*                                                                     *)
(*  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.     *)
(*                                                                     *)
(* *********************************************************************)
(** Neededness analysis for ARM operators *)
Definition needs_of_condition (cond: condition): list nval := nil.
Definition needs_of_shift (s: shift) (nv: nval): nval :=
match s with
| Slsl x => shlimm nv x
| Slsr x => shruimm nv x
| Sasr x => shrimm nv x
| Sror x => ror nv x
end.
Definition op1 (nv: nval) := nv :: nil.
Definition op2 (nv: nval) := nv :: nv :: nil.
Definition op2shift (s: shift) (nv: nval) := nv :: needs_of_shift s nv :: nil.
Definition needs_of_operation (op: operation) (nv: nval): list nval :=
match op with
| Omove => nv::nil
| 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)
| Oaddshift s => op2shift s (modarith nv)
| Oaddimm _ => op1 (modarith nv)
| Osub => op2 (default nv)
| Osubshift s => op2shift s (default nv)
| Orsubshift s => op2shift s (default nv)
| Orsubimm _ => op1 (default nv)
| Omul => op2 (modarith nv)
| Omla => let n := modarith nv in let n2 := modarith n in n2::n2::n::nil
| Omulhu | Omulhs | Odiv | Odivu => let n := default nv in n::n::nil
| Oand => op2 (bitwise nv)
| Oandshift s => op2shift s (bitwise nv)
| Oandimm n => op1 (andimm nv n)
| Oor => op2 (bitwise nv)
| Oorshift s => op2shift s (bitwise nv)
| Oorimm n => op1 (orimm nv n)
| Oxor => op2 (bitwise nv)
| Oxorshift s => op2shift s (bitwise nv)
| Oxorimm n => op1 (bitwise nv)
| Obic => let n := bitwise nv in n::bitwise n::nil
| Obicshift s => let n := bitwise nv in n::needs_of_shift s (bitwise n)::nil
| Onot => op1 (bitwise nv)
| Onotshift s => op1 (needs_of_shift s (bitwise nv))
| Oshl | Oshr | Oshru => op2 (default nv)
| Oshift s => op1 (needs_of_shift s nv)
| Oshrximm _ => 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)
| Ointofsingle | Ointuofsingle | Osingleofint | Osingleofintu => op1 (default nv)
| 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
| _ => 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.