include "Clight/Csyntax.ma".

definition add_cost_before : statement → universe CostTag → statement × (universe CostTag) ≝
λs,gen.
  let 〈l,gen〉 ≝ fresh … gen in
  〈Scost l s, gen〉.

definition add_cost_after : statement → universe CostTag → statement × (universe CostTag) ≝
λs,gen.
  let 〈l,gen〉 ≝ fresh … gen in
  〈Ssequence s (Scost l Sskip), gen〉.

definition add_cost_expr : expr → universe CostTag → expr × (universe CostTag) ≝
λe,gen.
  let 〈l,gen〉 ≝ fresh … gen in
  〈Expr (Ecost l e) (typeof e), gen〉.

let rec label_expr (e:expr) (costgen:universe CostTag)
        on e : expr × (universe CostTag) ≝
match e with
[ Expr ed ty ⇒ let 〈ed,costgen〉 ≝ label_expr_descr ed costgen in
               〈Expr ed ty, costgen〉
]
and label_expr_descr (e:expr_descr) (costgen:universe CostTag)
    on e : expr_descr × (universe CostTag) ≝
match e with
[ Ederef e' ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Ederef e', costgen〉
| Eaddrof e' ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Eaddrof e', costgen〉
| Eunop op e' ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Eunop op e', costgen〉
| Ebinop op e1 e2 ⇒
    let 〈e1,costgen〉 ≝ label_expr e1 costgen in 
    let 〈e2,costgen〉 ≝ label_expr e2 costgen in 
    〈Ebinop op e1 e2, costgen〉
| Ecast ty e' ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Ecast ty e', costgen〉
| Econdition e' e1 e2 ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    let 〈e1,costgen〉 ≝ label_expr e1 costgen in 
    let 〈e1,costgen〉 ≝ add_cost_expr e1 costgen in 
    let 〈e2,costgen〉 ≝ label_expr e2 costgen in 
    let 〈e2,costgen〉 ≝ add_cost_expr e2 costgen in 
    〈Econdition e' e1 e2, costgen〉
(* andbool and orbool are changed to conditionals to capture their
   short-circuiting cost difference *)
| Eandbool e1 e2 ⇒
    let 〈e1,costgen〉 ≝ label_expr e1 costgen in 
    let 〈e2,costgen〉 ≝ label_expr e2 costgen in 
    let 〈e2,costgen〉 ≝ add_cost_expr e2 costgen in 
    let 〈ef,costgen〉 ≝ add_cost_expr (Expr (Econst_int I32 (zero ?)) (Tint I32 Signed)) costgen in
    〈Econdition e1 e2 ef, costgen〉
| Eorbool e1 e2 ⇒
    let 〈e1,costgen〉 ≝ label_expr e1 costgen in 
    let 〈et,costgen〉 ≝ add_cost_expr (Expr (Econst_int I32 (repr ? 1)) (Tint I32 Signed)) costgen in
    let 〈e2,costgen〉 ≝ label_expr e2 costgen in 
    let 〈e2,costgen〉 ≝ add_cost_expr e2 costgen in 
    〈Econdition e1 et e2, costgen〉

| Efield e' id ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Efield e' id, costgen〉
(* The prototype asserts on preexisting cost labels, but I'd quite like to
   keep them. *)
| Ecost l e' ⇒
    let 〈e',costgen〉 ≝ label_expr e' costgen in 
    〈Ecost l e', costgen〉

(* The remaining expressions don't have subexpressions. *)
| _ ⇒ 〈e,costgen〉
].

let rec label_exprs (l:list expr) (costgen:universe CostTag)
        on l : list expr × (universe CostTag) ≝
match l with
[ nil ⇒ 〈nil ?,costgen〉
| cons e es ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in
    let 〈es,costgen〉 ≝ label_exprs es costgen in
    〈e::es,costgen〉
].

definition label_opt_expr ≝
λoe,costgen. match oe with
[ None ⇒ 〈None ?, costgen〉
| Some e ⇒ let 〈e,costgen〉 ≝ label_expr e costgen in 〈Some ? e,costgen〉
].


let rec label_statement (s:statement) (costgen:universe CostTag)
        on s : statement × (universe CostTag) ≝
match s with
[ Sskip ⇒ 〈Sskip,costgen〉
| Sassign e1 e2 ⇒
    let 〈e1,costgen〉 ≝ label_expr e1 costgen in 
    let 〈e2,costgen〉 ≝ label_expr e2 costgen in
    〈Sassign e1 e2, costgen〉
| Scall e_ret e_fn e_args ⇒
    let 〈e_ret,costgen〉 ≝ label_opt_expr e_ret costgen in
    let 〈e_fn,costgen〉 ≝ label_expr e_fn costgen in
    let 〈e_args,costgen〉 ≝ label_exprs e_args costgen in
    〈Scall e_ret e_fn e_args, costgen〉
| Ssequence s1 s2 ⇒
    let 〈s1,costgen〉 ≝ label_statement s1 costgen in
    let 〈s2,costgen〉 ≝ label_statement s2 costgen in
    〈Ssequence s1 s2, costgen〉
| Sifthenelse e s1 s2 ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in 
    let 〈s1,costgen〉 ≝ label_statement s1 costgen in
    let 〈s1,costgen〉 ≝ add_cost_before s1 costgen in
    let 〈s2,costgen〉 ≝ label_statement s2 costgen in
    let 〈s2,costgen〉 ≝ add_cost_before s2 costgen in
    〈Sifthenelse e s1 s2, costgen〉
| Swhile e s' ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in 
    let 〈s',costgen〉 ≝ label_statement s' costgen in
    let 〈s',costgen〉 ≝ add_cost_before s' costgen in
    let 〈s,costgen〉 ≝ add_cost_after (Swhile e s') costgen in
    〈s,costgen〉
| Sdowhile e s' ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in 
    let 〈s',costgen〉 ≝ label_statement s' costgen in
    let 〈s',costgen〉 ≝ add_cost_before s' costgen in
    let 〈s,costgen〉 ≝ add_cost_after (Sdowhile e s') costgen in
    〈s,costgen〉
| Sfor s1 e s2 s3 ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in 
    let 〈s1,costgen〉 ≝ label_statement s1 costgen in
    let 〈s2,costgen〉 ≝ label_statement s2 costgen in
    let 〈s3,costgen〉 ≝ label_statement s3 costgen in
    let 〈s3,costgen〉 ≝ add_cost_before s3 costgen in
    let 〈s,costgen〉 ≝ add_cost_after (Sfor s1 e s2 s3) costgen in
    〈s,costgen〉
| Sbreak ⇒ 〈Sbreak,costgen〉
| Scontinue ⇒ 〈Scontinue,costgen〉
| Sreturn opt_e ⇒
    let 〈opt_e,costgen〉 ≝ label_opt_expr opt_e costgen in
    〈Sreturn opt_e,costgen〉
| Sswitch e ls ⇒
    let 〈e,costgen〉 ≝ label_expr e costgen in 
    let 〈ls,costgen〉 ≝ label_lstatements ls costgen in
    〈Sswitch e ls, costgen〉
| Slabel l s' ⇒
    let 〈s',costgen〉 ≝ label_statement s' costgen in
    let 〈s',costgen〉 ≝ add_cost_before s' costgen in
    〈Slabel l s', costgen〉
| Sgoto l ⇒ 〈Sgoto l, costgen〉

(* The prototype asserts on preexisting cost labels, but I'd quite like to
   keep them. *)
| Scost l s' ⇒
    let 〈s',costgen〉 ≝ label_statement s' costgen in
    〈Scost l s', costgen〉
]
and label_lstatements (ls:labeled_statements) (costgen:universe CostTag)
        on ls : labeled_statements × (universe CostTag) ≝
match ls with
[ LSdefault s ⇒
    let 〈s,costgen〉 ≝ label_statement s costgen in
    let 〈s,costgen〉 ≝ add_cost_before s costgen in
    〈LSdefault s, costgen〉
| LScase sz i s ls' ⇒
    let 〈s,costgen〉 ≝ label_statement s costgen in
    let 〈s,costgen〉 ≝ add_cost_before s costgen in
    let 〈ls',costgen〉 ≝ label_lstatements ls' costgen in
    〈LScase sz i s ls', costgen〉
].

definition label_function : function → res function ≝
λf.
  let costgen ≝ new_universe CostTag in
  let 〈body,costgen〉 ≝ label_statement (fn_body f) costgen in
  let 〈body,costgen〉 ≝ add_cost_before body costgen in
  do u ← check_universe_ok ? costgen;
  OK ? (mk_function (fn_return f) (fn_params f) (fn_vars f) body).

definition label_fundef : clight_fundef → res clight_fundef ≝
λf. match f with
[ CL_Internal f ⇒ do f ← label_function f; OK ? (CL_Internal f)
| CL_External id args ty ⇒ OK ? (CL_External id args ty)
].

definition clight_label : clight_program → res clight_program ≝
 λp. transform_partial_program … p label_fundef.