summaryrefslogtreecommitdiff
path: root/kernel/vm.ml
blob: 9ff369e592a68c524935c745b0b3ee0ca0aabc00 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2014     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Names
open Term
open Conv_oracle
open Cbytecodes

external set_drawinstr : unit -> unit = "coq_set_drawinstr"

(******************************************)
(* Utility Functions about Obj ************)
(******************************************)

external offset_closure : Obj.t -> int -> Obj.t = "coq_offset_closure"
external offset : Obj.t -> int = "coq_offset"

let accu_tag = 0

(*******************************************)
(* Initalization of the abstract machine ***)
(*******************************************)

external init_vm : unit -> unit = "init_coq_vm"

let _ = init_vm ()

external transp_values : unit -> bool = "get_coq_transp_value"
external set_transp_values : bool -> unit = "coq_set_transp_value"

(*******************************************)
(* Machine code *** ************************)
(*******************************************)

type tcode
let tcode_of_obj v = ((Obj.obj v):tcode)
let fun_code v = tcode_of_obj (Obj.field (Obj.repr v) 0)

external mkAccuCode : int -> tcode = "coq_makeaccu"
external mkPopStopCode : int -> tcode = "coq_pushpop"
external mkAccuCond : int -> tcode = "coq_accucond"

external offset_tcode : tcode -> int -> tcode = "coq_offset_tcode"
external int_tcode : tcode -> int -> int = "coq_int_tcode"

external accumulate : unit -> tcode = "accumulate_code"
let accumulate = accumulate ()

external is_accumulate : tcode -> bool = "coq_is_accumulate_code"

let popstop_tbl =  ref (Array.init 30 mkPopStopCode)

let popstop_code i =
  let len = Array.length !popstop_tbl in
  if i < len then !popstop_tbl.(i)
  else
    begin
      popstop_tbl :=
	Array.init (i+10)
	  (fun j -> if j < len then !popstop_tbl.(j) else mkPopStopCode j);
      !popstop_tbl.(i)
    end

let stop = popstop_code 0

(******************************************************)
(* Abstract data types and utility functions **********)
(******************************************************)

(* Values of the abstract machine *)
let val_of_obj v = ((Obj.obj v):values)
let crazy_val = (val_of_obj (Obj.repr 0))

(* Abstract data *)
type vprod
type vfun
type vfix
type vcofix
type vblock
type arguments

type vm_env
type vstack = values array

type vswitch = {
    sw_type_code : tcode;
    sw_code : tcode;
    sw_annot : annot_switch;
    sw_stk : vstack;
    sw_env : vm_env
  }

(* Representation of values *)
(* + Products : *)
(*   -   vprod = 0_[ dom | codom]                                         *)
(*             dom : values, codom : vfun                                 *)
(*                                                                        *)
(* + Functions have two representations :                                 *)
(*   - unapplied fun :  vf = Ct_[ C | fv1 | ... | fvn]                    *)
(*                                       C:tcode, fvi : values            *)
(*     Remark : a function and its environment is the same value.         *)
(*   - partially applied fun : Ct_[Restart:C| vf | arg1 | ... argn]       *)
(*                                                                        *)
(* + Fixpoints :                                                          *)
(*   -        Ct_[C1|Infix_t|C2|...|Infix_t|Cn|fv1|...|fvn]               *)
(*     One single block to represent all of the fixpoints, each fixpoint  *)
(*     is the pointer to the field holding the pointer to its code, and   *)
(*     the infix tag is used to know where the block starts.              *)
(*   - Partial application follows the scheme of partially applied        *)
(*     functions. Note: only fixpoints not having been applied to its     *)
(*     recursive argument are coded this way. When the rec. arg. is       *)
(*     applied, either it's a constructor and the fix reduces, or it's    *)
(*     and the fix is coded as an accumulator.                            *)
(*                                                                        *)
(* + Cofixpoints : see cbytegen.ml                                        *)
(*                                                                        *)
(* + vblock's encode (non constant) constructors as in Ocaml, but         *)
(*   starting from 0 up. tag 0 ( = accu_tag) is reserved for              *)
(*   accumulators.                                                        *)
(*                                                                        *)
(* + vm_env is the type of the machine environments (i.e. a function or   *)
(*   a fixpoint)                                                          *)
(*                                                                        *)
(* + Accumulators : At_[accumulate| accu | arg1 | ... | argn ]            *)
(*   - representation of [accu] : tag_[....]                              *)
(*     -- tag <= 2 : encoding atom type (sorts, free vars, etc.)          *)
(*     -- 3_[accu|fix_app] : a fixpoint blocked by an accu                *)
(*     -- 4_[accu|vswitch] : a match blocked by an accu                   *)
(*     -- 5_[fcofix]       : a cofix function                             *)
(*     -- 6_[fcofix|val]   : a cofix function, val represent the value    *)
(*        of the function applied to arg1 ... argn                        *)
(* The [arguments] type, which is abstracted as an array, represents :    *)
(*          tag[ _ | _ |v1|... | vn]                                      *)
(* Generally the first field is a code pointer.                           *)

(* Do not edit this type without editing C code, especially "coq_values.h" *)
type atom =
  | Aid of id_key
  | Aiddef of id_key * values
  | Aind of inductive

(* Zippers *)

type zipper =
  | Zapp of arguments
  | Zfix of vfix*arguments  (* Possibly empty *)
  | Zswitch of vswitch

type stack = zipper list

type to_up = values

type whd =
  | Vsort of sorts
  | Vprod of vprod
  | Vfun of vfun
  | Vfix of vfix * arguments option
  | Vcofix of vcofix * to_up * arguments option
  | Vconstr_const of int
  | Vconstr_block of vblock
  | Vatom_stk of atom * stack

(*************************************************)
(* Destructors ***********************************)
(*************************************************)

let rec whd_accu a stk =
  let stk =
    if Obj.size a = 2 then stk
    else Zapp (Obj.obj a) :: stk in
  let at = Obj.field a 1 in
  match Obj.tag at with
  | i when i <= 2 ->
      Vatom_stk(Obj.magic at, stk)
  | 3 (* fix_app tag *) ->
      let fa = Obj.field at 1 in
      let zfix  =
	Zfix (Obj.obj (Obj.field fa 1), Obj.obj fa) in
      whd_accu (Obj.field at 0) (zfix :: stk)
  | 4 (* switch tag  *) ->
      let zswitch = Zswitch (Obj.obj (Obj.field at 1)) in
      whd_accu (Obj.field at 0) (zswitch :: stk)
  | 5 (* cofix_tag *) ->
      let vcfx = Obj.obj (Obj.field at 0) in
      let to_up = Obj.obj a in
      begin match stk with
      | []          -> Vcofix(vcfx, to_up, None)
      | [Zapp args] -> Vcofix(vcfx, to_up, Some args)
      | _           -> assert false
      end
  | 6 (* cofix_evaluated_tag *) ->
      let vcofix = Obj.obj (Obj.field at 0) in
      let res = Obj.obj a in
      begin match stk with
      | []          -> Vcofix(vcofix, res, None)
      | [Zapp args] -> Vcofix(vcofix, res, Some args)
      | _           -> assert false
      end
  | _ -> assert false

external kind_of_closure : Obj.t -> int = "coq_kind_of_closure"

let whd_val : values -> whd =
  fun v ->
    let o = Obj.repr v in
    if Obj.is_int o then Vconstr_const (Obj.obj o)
    else
      let tag = Obj.tag o in
      if tag = accu_tag then
	(
	if Obj.size o = 1 then Obj.obj o (* sort *)
	else
	  if is_accumulate (fun_code o) then whd_accu o []
	  else (Vprod(Obj.obj o)))
      else
	if tag = Obj.closure_tag || tag = Obj.infix_tag then
	  (	   match kind_of_closure o with
	   | 0 -> Vfun(Obj.obj o)
	   | 1 -> Vfix(Obj.obj o, None)
	   | 2 -> Vfix(Obj.obj (Obj.field o 1), Some (Obj.obj o))
	   | 3 -> Vatom_stk(Aid(RelKey(int_tcode (fun_code o) 1)), [])
	   | _ -> Util.anomaly "Vm.whd : kind_of_closure does not work")
	else Vconstr_block(Obj.obj o)



(************************************************)
(* Abstrct machine ******************************)
(************************************************)

(* gestion de la pile *)
external push_ra : tcode -> unit = "coq_push_ra"
external push_val : values -> unit = "coq_push_val"
external push_arguments : arguments -> unit = "coq_push_arguments"
external push_vstack : vstack -> unit = "coq_push_vstack"


(* interpreteur *)
external interprete : tcode -> values -> vm_env -> int -> values =
  "coq_interprete_ml"



(* Functions over arguments *)
let nargs : arguments -> int = fun args -> (Obj.size (Obj.repr args)) - 2
let arg args i =
  if  0 <= i && i < (nargs args) then
    val_of_obj (Obj.field (Obj.repr args) (i+2))
  else raise (Invalid_argument
		("Vm.arg size = "^(string_of_int (nargs args))^
		 " acces "^(string_of_int i)))

let apply_arguments vf vargs =
  let n = nargs vargs in
  if n = 0 then vf
  else
   begin
     push_ra stop;
     push_arguments vargs;
     interprete (fun_code vf) vf (Obj.magic vf) (n - 1)
   end

let apply_vstack vf vstk =
  let n = Array.length vstk in
  if n = 0 then vf
  else
    begin
      push_ra stop;
      push_vstack vstk;
      interprete (fun_code vf) vf (Obj.magic vf) (n - 1)
    end

(**********************************************)
(* Constructors *******************************)
(**********************************************)

let obj_of_atom : atom -> Obj.t =
  fun a ->
    let res = Obj.new_block accu_tag 2 in
    Obj.set_field res 0 (Obj.repr accumulate);
    Obj.set_field res 1 (Obj.repr a);
    res

(* obj_of_str_const : structured_constant -> Obj.t *)
let rec obj_of_str_const str =
  match str with
  | Const_sorts s -> Obj.repr (Vsort s)
  | Const_ind ind -> obj_of_atom (Aind ind)
  | Const_b0 tag -> Obj.repr tag
  | Const_bn(tag, args) ->
      let len = Array.length args in
      let res = Obj.new_block tag len in
      for i = 0 to len - 1 do
	Obj.set_field res i (obj_of_str_const args.(i))
      done;
      res

let val_of_obj o = ((Obj.obj o) : values)

let val_of_str_const str = val_of_obj (obj_of_str_const str)

let val_of_atom a = val_of_obj (obj_of_atom a)

let idkey_tbl = Hashtbl.create 31

let val_of_idkey key =
  try Hashtbl.find idkey_tbl key
  with Not_found ->
    let v = val_of_atom (Aid key) in
    Hashtbl.add idkey_tbl key v;
    v

let val_of_rel k = val_of_idkey (RelKey k)
let val_of_rel_def k v = val_of_atom(Aiddef(RelKey k, v))

let val_of_named id = val_of_idkey (VarKey id)
let val_of_named_def id v = val_of_atom(Aiddef(VarKey id, v))

let val_of_constant c = val_of_idkey (ConstKey c)
let val_of_constant_def n c v =
  let res = Obj.new_block accu_tag 2 in
  Obj.set_field res 0 (Obj.repr (mkAccuCond n));
  Obj.set_field res 1 (Obj.repr (Aiddef(ConstKey c, v)));
  val_of_obj res

external val_of_annot_switch : annot_switch -> values = "%identity"

let mkrel_vstack k arity =
  let max = k + arity - 1 in
  Array.init arity (fun i -> val_of_rel (max - i))


(*************************************************)
(** Operations manipulating data types ***********)
(*************************************************)

(* Functions over products *)

let dom : vprod -> values = fun p -> val_of_obj (Obj.field (Obj.repr p) 0)
let codom : vprod -> vfun = fun p -> (Obj.obj (Obj.field (Obj.repr p) 1))

(* Functions over vfun *)

external closure_arity : vfun -> int = "coq_closure_arity"

let body_of_vfun k vf =
  let vargs = mkrel_vstack k 1 in
  apply_vstack (Obj.magic vf) vargs

let decompose_vfun2 k vf1 vf2 =
  let arity = min (closure_arity vf1) (closure_arity vf2) in
  assert (0 < arity && arity < Sys.max_array_length);
  let vargs = mkrel_vstack k arity in
  let v1 = apply_vstack (Obj.magic vf1) vargs in
  let v2 = apply_vstack (Obj.magic vf2) vargs in
  arity, v1, v2

(* Functions over fixpoint *)

let first o = (offset_closure o (offset o))
let last o = (Obj.field o (Obj.size o - 1))

let current_fix vf = - (offset (Obj.repr vf) / 2)

let unsafe_fb_code fb i = tcode_of_obj (Obj.field (Obj.repr fb) (2 * i))

let unsafe_rec_arg fb i = int_tcode (unsafe_fb_code fb i) 1

let rec_args vf =
  let fb = first (Obj.repr vf) in
  let size = Obj.size (last fb) in
  Array.init size (unsafe_rec_arg fb)

exception FALSE

let check_fix f1 f2 =
  let i1, i2 = current_fix f1, current_fix f2 in
  (* Checking starting point *)
  if i1 = i2 then
    let fb1,fb2 = first (Obj.repr f1), first (Obj.repr f2) in
    let n = Obj.size (last fb1) in
    (* Checking number of definitions *)
    if n = Obj.size (last fb2) then
      (* Checking recursive arguments *)
      try
	for i = 0 to n - 1 do
	  if unsafe_rec_arg fb1 i <> unsafe_rec_arg fb2 i
	  then raise FALSE
	done;
	true
      with FALSE -> false
    else false
  else false

(* Functions over vfix *)
external atom_rel : unit -> atom array = "get_coq_atom_tbl"
external realloc_atom_rel : int -> unit = "realloc_coq_atom_tbl"

let relaccu_tbl =
  let atom_rel = atom_rel() in
  let len = Array.length atom_rel in
  for i = 0 to len - 1 do atom_rel.(i) <- Aid (RelKey i) done;
  ref (Array.init len mkAccuCode)

let relaccu_code i =
  let len = Array.length !relaccu_tbl in
  if i < len then !relaccu_tbl.(i)
  else
    begin
      realloc_atom_rel i;
      let atom_rel = atom_rel () in
      let nl = Array.length atom_rel in
      for j = len to nl - 1 do atom_rel.(j) <- Aid(RelKey j) done;
      relaccu_tbl :=
	Array.init nl
	  (fun j -> if j < len then !relaccu_tbl.(j) else mkAccuCode j);
      !relaccu_tbl.(i)
    end

let reduce_fix k vf =
  let fb = first (Obj.repr vf) in
  (* computing types *)
  let fc_typ = ((Obj.obj (last fb)) : tcode array) in
  let ndef = Array.length fc_typ in
  let et = offset_closure fb (2*(ndef - 1)) in
  let ftyp =
    Array.map
      (fun c -> interprete c crazy_val (Obj.magic et) 0) fc_typ in
  (* Construction of the environment of fix bodies *)
  let e = Obj.dup fb in
  for i = 0 to ndef - 1 do
    Obj.set_field e (2 * i) (Obj.repr (relaccu_code (k + i)))
  done;
  let fix_body i =
    let jump_grabrec c = offset_tcode c 2 in
    let c = jump_grabrec (unsafe_fb_code fb i)  in
    let res = Obj.new_block Obj.closure_tag 2 in
    Obj.set_field res 0 (Obj.repr c);
    Obj.set_field res 1 (offset_closure e (2*i));
    ((Obj.obj res) : vfun)  in
  (Array.init ndef fix_body, ftyp)

(* Functions over vcofix *)

let get_fcofix vcf i =
  match whd_val (Obj.obj (Obj.field (Obj.repr vcf) (i+1))) with
  | Vcofix(vcfi, _, _) -> vcfi
  | _ -> assert false

let current_cofix vcf =
  let ndef = Obj.size (last (Obj.repr vcf)) in
  let rec find_cofix pos =
    if pos < ndef then
      if get_fcofix vcf pos == vcf then pos
      else find_cofix (pos+1)
    else raise Not_found in
  try find_cofix 0
  with Not_found -> assert false

let check_cofix vcf1 vcf2 =
  (current_cofix vcf1 = current_cofix vcf2) &&
  (Obj.size (last (Obj.repr vcf1)) = Obj.size (last (Obj.repr vcf2)))

let reduce_cofix k vcf =
  let fc_typ = ((Obj.obj (last (Obj.repr vcf))) : tcode array) in
  let ndef = Array.length fc_typ in
  let ftyp =
    (* Evaluate types *)
    Array.map (fun c -> interprete c crazy_val (Obj.magic vcf) 0) fc_typ in

  (* Construction of the environment of cofix bodies *)
  let e = Obj.dup (Obj.repr vcf) in
  for i = 0 to ndef - 1 do
    Obj.set_field e (i+1) (Obj.repr (val_of_rel (k+i)))
  done;

  let cofix_body i =
    let vcfi = get_fcofix vcf i in
    let c = Obj.field (Obj.repr vcfi) 0 in
    Obj.set_field e 0 c;
    let atom = Obj.new_block cofix_tag 1 in
    let self = Obj.new_block accu_tag 2 in
    Obj.set_field self 0 (Obj.repr accumulate);
    Obj.set_field self 1 (Obj.repr atom);
    apply_vstack (Obj.obj e) [|Obj.obj self|] in
  (Array.init ndef cofix_body, ftyp)


(* Functions over vblock *)

let btag : vblock -> int = fun b -> Obj.tag (Obj.repr b)
let bsize : vblock -> int = fun b -> Obj.size (Obj.repr b)
let bfield b i =
  if 0 <= i && i < (bsize b) then val_of_obj (Obj.field (Obj.repr b) i)
  else raise (Invalid_argument "Vm.bfield")


(* Functions over vswitch *)

let check_switch sw1 sw2 = sw1.sw_annot.rtbl = sw2.sw_annot.rtbl

let case_info sw = sw.sw_annot.ci

let type_of_switch sw =
  push_vstack sw.sw_stk;
  interprete sw.sw_type_code crazy_val sw.sw_env 0

let branch_arg k (tag,arity) =
  if arity = 0 then  ((Obj.magic tag):values)
  else
    let b = Obj.new_block tag arity in
    for i = 0 to arity - 1 do
      Obj.set_field b i (Obj.repr (val_of_rel (k+i)))
    done;
    val_of_obj b

let apply_switch sw arg =
  let tc = sw.sw_annot.tailcall in
  if tc then
    (push_ra stop;push_vstack sw.sw_stk)
  else
    (push_vstack sw.sw_stk; push_ra (popstop_code (Array.length sw.sw_stk)));
  interprete sw.sw_code arg sw.sw_env 0

let branch_of_switch k sw =
  let eval_branch (_,arity as ta) =
    let arg = branch_arg k ta in
    let v = apply_switch sw arg in
    (arity, v)
  in
  Array.map eval_branch sw.sw_annot.rtbl



(* Evaluation *)

let rec whd_stack v stk =
  match stk with
  | [] -> whd_val v
  | Zapp args :: stkt -> whd_stack (apply_arguments v args) stkt
  | Zfix (f,args) :: stkt ->
      let o = Obj.repr v in
      if Obj.is_block o && Obj.tag o = accu_tag then
	whd_accu (Obj.repr v) stk
      else
	let v', stkt =
	  match stkt with
	  | Zapp args' :: stkt ->
	      push_ra stop;
	      push_arguments args';
	      push_val v;
	      push_arguments args;
	      let v' =
		interprete (fun_code f) (Obj.magic f) (Obj.magic f)
		  (nargs args+ nargs args') in
	      v', stkt
	  | _ ->
	      push_ra stop;
	      push_val v;
	      push_arguments args;
	      let v' =
		interprete (fun_code f) (Obj.magic f) (Obj.magic f)
		  (nargs args) in
	      v', stkt
	in
	whd_stack v' stkt
  | Zswitch sw :: stkt ->
      let o = Obj.repr v in
      if Obj.is_block o && Obj.tag o = accu_tag then
	if Obj.tag (Obj.field o 1) < cofix_tag then whd_accu (Obj.repr v) stk
	else
	  let to_up =
	    match whd_accu (Obj.repr v) [] with
	    | Vcofix (_, to_up, _) -> to_up
	    | _ -> assert false in
	  whd_stack (apply_switch sw to_up) stkt
      else whd_stack (apply_switch sw v) stkt

let rec force_whd v stk =
  match whd_stack v stk with
  | Vatom_stk(Aiddef(_,v),stk) -> force_whd v stk
  | res -> res


let rec eta_stack a stk v =
  match stk with
  | [] -> apply_vstack a [|v|]
  | Zapp args :: stk -> eta_stack (apply_arguments a args) stk v
  | Zfix(f,args) :: stk ->
      let a,stk = 
	match stk with
	| Zapp args' :: stk ->
	    push_ra stop;
	    push_arguments args';
	    push_val a;
	    push_arguments args;
	    let a =
	      interprete (fun_code f) (Obj.magic f) (Obj.magic f)
		(nargs args+ nargs args') in
	    a, stk
	| _ -> 
	    push_ra stop;
	    push_val a;
	    push_arguments args;
	    let a =
	      interprete (fun_code f) (Obj.magic f) (Obj.magic f)
		(nargs args) in
	    a, stk in
      eta_stack a stk v
  | Zswitch sw :: stk ->
      eta_stack (apply_switch sw a) stk v

let eta_whd k whd =
  let v = val_of_rel k in
  match whd with
  | Vsort _ | Vprod _ | Vconstr_const _ | Vconstr_block _ -> assert false
  | Vfun f -> body_of_vfun k f
  | Vfix(f, None) -> 
      push_ra stop;
      push_val v;
      interprete (fun_code f) (Obj.magic f) (Obj.magic f) 0
  | Vfix(f, Some args) ->
      push_ra stop;
      push_val v;
      push_arguments args;
      interprete (fun_code f) (Obj.magic f) (Obj.magic f) (nargs args) 
  | Vcofix(_,to_up,_) ->
      push_ra stop;
      push_val v;
      interprete (fun_code to_up) (Obj.magic to_up) (Obj.magic to_up) 0
  | Vatom_stk(a,stk) ->
      eta_stack (val_of_atom a) stk v