(* XXX NB: I haven't checked all of these semantics against the prototype
           compilers yet! *)

include "RTLabs/RTLabs-syntax.ma".

include "common/Errors.ma".
include "common/Globalenvs.ma".
include "common/IO.ma".
include "common/SmallstepExec.ma".

definition genv ≝ (genv_t Genv) (fundef internal_function).

record frame : Type[0] ≝
{ func   : internal_function
; locals : register_env split_val
; next   : label
; sp     : block
; retdst : registers (* XXX: not optional? *)
}.

definition adv : label → frame → frame ≝
λl,f. mk_frame (func f) (locals f) l (sp f) (retdst f).

inductive state : Type[0] ≝
| State : 
   ∀   f : frame.
   ∀  fs : list frame.
   ∀   m : mem.
   state
| Callstate :
   ∀  fd : fundef internal_function.
   ∀args : list val.
   ∀ dst : registers.
   ∀ stk : list frame.
   ∀   m : mem.
   state
| Returnstate :
   ∀ rtv : val.
   ∀ dst : registers.
   ∀ stk : list frame.
   ∀   m : mem.
   state.

definition mem_of_state : state → mem ≝
λs. match s with [ State _ _ m ⇒ m | Callstate _ _ _ _ m ⇒ m | Returnstate _ _ _ m ⇒ m ].

definition build_state ≝ λf.λfs.λm.λn. State (adv n f) fs m.

definition reg_store ≝
λrs,v,locals. match rs with [ dp n regs ⇒
  do vs ← break n v;
  OK ? (fold_right2_i ??? (λ_.λr,v,lcls. add RegisterTag ? lcls r v) locals n regs vs)
].

let rec params_store (rs:list registers) (vs:list val) (locals : register_env split_val) : res (register_env split_val) ≝
match rs with
[ nil ⇒ match vs with [ nil ⇒ OK ? locals | _ ⇒ Error ? ]
| cons r rst ⇒ match vs with [ nil ⇒ Error ? | cons v vst ⇒
  do locals' ← reg_store r v locals;
  params_store rst vst locals'
] ].

definition reg_retrieve : register_env ? → registers → res val ≝
λlocals,rs. match rs with [ dp n regs ⇒
  do vs ← fold_right_i ??? (λm,r,vs. do vs' ← vs; do v ← opt_to_res … (lookup ?? locals r); OK ? (v:::vs')) (OK ? [[ ]]) regs;
  merge n vs
].

(* TODO: maybe should make immediate = int or offset; val seems like a cheat here - not a real runtime value *)

definition eval_addr : genv → frame → ∀m:addressing. Vector registers (addr_mode_args m) → res val ≝
λge,f,m. match m return λm'.Vector registers (addr_mode_args m') → ? with
[ Aindexed i ⇒ λargs.
    do v ← reg_retrieve (locals f) ((args !!! 0) ?);
    opt_to_res … (ev_add v (Vint i))
| Aindexed2 ⇒ λargs.
    do v1 ← reg_retrieve (locals f) ((args !!! 0) ?);
    do v2 ← reg_retrieve (locals f) ((args !!! 1) ?);
    opt_to_res … (ev_add v1 v2)
| Aglobal id off ⇒ λargs.
    do loc ← opt_to_res … (find_symbol ?? ge id);
    OK ? (Vptr Any loc ? (shift_offset zero_offset off))
| Abased id off ⇒ λargs.
    do loc ← opt_to_res … (find_symbol ?? ge id);
    do v ← reg_retrieve (locals f) ((args !!! 0) ?);
    opt_to_res … (ev_add (Vptr Any loc ? zero_offset) v)
| Ainstack off ⇒ λargs.
    OK ? (Vptr Any (sp f) ? (shift_offset zero_offset off))
]
. /2/ [ 1,2: cases loc | cases (sp f) ] // qed.

definition is_true_val : val → res bool ≝
λv. match v with
[ Vint i ⇒ OK ? (notb (eq i zero))
| Vnull _ ⇒ OK ? false
| Vptr _ _ _ _ ⇒ OK ? true
| _ ⇒ Error ?
].


(* XXX put somewhere sensible *)
let rec nth_opt (A:Type[0]) (n:nat) (l:list A) on l : option A ≝
match l with
[ nil ⇒ None ?
| cons h t ⇒ match n with [ O ⇒ Some ? h | S m ⇒ nth_opt A m t ]
].

definition eval_statement : genv → state → IO io_out io_in (trace × state) ≝
λge,st.
match st with
[ State f fs m ⇒
  ! s ← lookup ?? (f_graph (func f)) (next f);
  match s with
  [ St_skip l ⇒ ret ? 〈E0, build_state f fs m l〉
  | St_cost cl l ⇒ ret ? 〈Echarge cl, build_state f fs m l〉
  | St_const rs cst l ⇒
      ! v ← opt_to_res … (eval_constant (find_symbol … ge) (sp f) cst);
      ! locals ← reg_store rs v (locals f);
      ret ? 〈E0, State (mk_frame (func f) locals l (sp f) (retdst f)) fs m〉
  | St_op1 op dst src l ⇒
      ! v ← reg_retrieve (locals f) src;
      ! v' ← opt_to_res … (eval_unop op v);
      ! locals ← reg_store dst v' (locals f);
      ret ? 〈E0, State (mk_frame (func f) locals l (sp f) (retdst f)) fs m〉
  | St_op2 op dst src1 src2 l ⇒
      ! v1 ← reg_retrieve (locals f) src1;
      ! v2 ← reg_retrieve (locals f) src2;
      ! v' ← opt_to_res … (eval_binop op v1 v2);
      ! locals ← reg_store dst v' (locals f);
      ret ? 〈E0, State (mk_frame (func f) locals l (sp f) (retdst f)) fs m〉
  | St_load chunk mode args dst l ⇒
      ! vaddr ← eval_addr ge f mode args;
      ! v ← opt_to_res … (loadv chunk m vaddr);
      ! locals ← reg_store dst v (locals f);
      ret ? 〈E0, State (mk_frame (func f) locals l (sp f) (retdst f)) fs m〉
  | St_store chunk mode args src l ⇒
      ! vaddr ← eval_addr ge f mode args;
      ! v ← reg_retrieve (locals f) src;
      ! m' ← opt_to_res … (storev chunk m vaddr v);
      ret ? 〈E0, build_state f fs m' l〉

  | St_call_id id args dst sig l ⇒ (* XXX: haven't used sig *)
      ! b ← opt_to_res … (find_symbol ?? ge id);
      ! fd ← opt_to_res … (find_funct_ptr ?? ge b);
      ! vs ← mmap ?? (reg_retrieve (locals f)) args;
      ret ? 〈E0, Callstate fd vs dst (adv l f::fs) m〉
  | St_call_ptr frs args dst sig l ⇒  (* XXX: haven't used sig *)
      ! fv ← reg_retrieve (locals f) frs;
      ! fd ← opt_to_res … (find_funct ?? ge fv);
      ! vs ← mmap ?? (reg_retrieve (locals f)) args;
      ret ? 〈E0, Callstate fd vs dst (adv l f::fs) m〉
  | St_tailcall_id id args sig ⇒ (* XXX: haven't used sig *)
      ! b ← opt_to_res … (find_symbol ?? ge id);
      ! fd ← opt_to_res … (find_funct_ptr ?? ge b);
      ! vs ← mmap ?? (reg_retrieve (locals f)) args;
      ret ? 〈E0, Callstate fd vs (retdst f) fs (free m (sp f))〉
  | St_tailcall_ptr frs args sig ⇒  (* XXX: haven't used sig *)
      ! fv ← reg_retrieve (locals f) frs;
      ! fd ← opt_to_res … (find_funct ?? ge fv);
      ! vs ← mmap ?? (reg_retrieve (locals f)) args;
      ret ? 〈E0, Callstate fd vs (retdst f) fs (free m (sp f))〉

  | St_condcst cst ltrue lfalse ⇒
      ! v ← opt_to_res … (eval_constant (find_symbol … ge) (sp f) cst);
      ! b ← is_true_val v;
      ret ? 〈E0, build_state f fs m (if b then ltrue else lfalse)〉
  | St_cond1 op src ltrue lfalse ⇒
      ! v ← reg_retrieve (locals f) src;
      ! v' ← opt_to_res … (eval_unop op v);
      ! b ← is_true_val v';
      ret ? 〈E0, build_state f fs m (if b then ltrue else lfalse)〉
  | St_cond2 op src1 src2 ltrue lfalse ⇒
      ! v1 ← reg_retrieve (locals f) src1;
      ! v2 ← reg_retrieve (locals f) src2;
      ! v' ← opt_to_res … (eval_binop op v1 v2);
      ! b ← is_true_val v';
      ret ? 〈E0, build_state f fs m (if b then ltrue else lfalse)〉

  | St_jumptable rs ls ⇒
      ! v ← reg_retrieve (locals f) rs;
      match v with
      [ Vint i ⇒
          ! l ← nth_opt ? (nat_of_bitvector ? i) ls;
          ret ? 〈E0, build_state f fs m l〉
      | _ ⇒ Wrong ???
      ]

  | St_return src ⇒
      ! v ← reg_retrieve (locals f) src;
      ret ? 〈E0, Returnstate v (retdst f) fs (free m (sp f))〉
  ]
| Callstate fd params dst fs m ⇒
    match fd with
    [ Internal fn ⇒
        ! locals ← params_store (f_params fn) params (empty_map RegisterTag ?);
        let 〈m', sp〉 ≝ alloc m 0 (f_stacksize fn) Any in
        ret ? 〈E0, State (mk_frame fn locals (f_entry fn) sp dst) fs m'〉
    | External fn ⇒
        ! evargs ← check_eventval_list params (sig_args (ef_sig fn));
        ! evres ← do_io (ef_id fn) evargs (match (sig_res (ef_sig fn)) with [ None ⇒ ASTint | Some t ⇒ t ]);  (* XXX hack, should allow none *)
        ret ? 〈Eextcall (ef_id fn) evargs (mk_eventval ? evres), Returnstate (mk_val ? evres) dst fs m〉

    ]
| Returnstate v dst fs m ⇒
    match fs with
    [ nil ⇒ Error ? (* Already in final state *)
    | cons f fs' ⇒
        ! locals ← reg_store dst v (locals f);
        ret ? 〈E0, State (mk_frame (func f) locals (next f) (sp f) (retdst f)) fs' m〉
    ]
].

definition is_final : state → option int ≝
λs. match s with
[ State _ _ _ ⇒ None ?
| Callstate _ _ _ _ _ ⇒ None ?
| Returnstate v _ fs _ ⇒
    match fs with [ nil ⇒ match v with [ Vint i ⇒ Some ? i | _ ⇒ None ? ] | cons _ _ ⇒ None ? ]
].

definition RTLabs_exec : execstep io_out io_in ≝
  mk_execstep … ? is_final mem_of_state eval_statement.

definition make_initial_state : RTLabs_program → res (genv × state) ≝
λp.
  do ge ← globalenv Genv ?? p;
  do m ← init_mem Genv ?? p;
  do b ← opt_to_res ? (find_symbol ? ? ge (prog_main ?? p));
  do f ← opt_to_res ? (find_funct_ptr ? ? ge b);
  OK ? 〈ge,Callstate f (nil ?) (dp ??? [[ ]]) (nil ?) m〉.

definition RTLabs_fullexec : fullexec io_out io_in ≝
  mk_fullexec … RTLabs_exec ? make_initial_state.