summaryrefslogtreecommitdiff
path: root/ia32/Asmgenproof.v
blob: ca0fd18221d6c813d35245c02c194aedede1b1f5 (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
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
(* *********************************************************************)
(*                                                                     *)
(*              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.     *)
(*                                                                     *)
(* *********************************************************************)

(** Correctness proof for x86 generation: main proof. *)

Require Import Coqlib.
Require Import Errors.
Require Import AST.
Require Import Integers.
Require Import Floats.
Require Import Values.
Require Import Memory.
Require Import Events.
Require Import Globalenvs.
Require Import Smallstep.
Require Import Op.
Require Import Locations.
Require Import Mach.
Require Import Conventions.
Require Import Asm.
Require Import Asmgen.
Require Import Asmgenproof0.
Require Import Asmgenproof1.

Section PRESERVATION.

Variable prog: Mach.program.
Variable tprog: Asm.program.
Hypothesis TRANSF: transf_program prog = Errors.OK tprog.

Let ge := Genv.globalenv prog.
Let tge := Genv.globalenv tprog.

Lemma symbols_preserved:
  forall id, Genv.find_symbol tge id = Genv.find_symbol ge id.
Proof.
  intros. unfold ge, tge. 
  apply Genv.find_symbol_transf_partial with transf_fundef.
  exact TRANSF. 
Qed.

Lemma functions_translated:
  forall b f,
  Genv.find_funct_ptr ge b = Some f ->
  exists tf, Genv.find_funct_ptr tge b = Some tf /\ transf_fundef f = Errors.OK tf.
Proof
  (Genv.find_funct_ptr_transf_partial transf_fundef _ TRANSF).

Lemma functions_transl:
  forall fb f tf,
  Genv.find_funct_ptr ge fb = Some (Internal f) ->
  transf_function f = OK tf ->
  Genv.find_funct_ptr tge fb = Some (Internal tf).
Proof.
  intros. exploit functions_translated; eauto. intros [tf' [A B]].
  monadInv B. rewrite H0 in EQ; inv EQ; auto. 
Qed.

Lemma varinfo_preserved:
  forall b, Genv.find_var_info tge b = Genv.find_var_info ge b.
Proof.
  intros. unfold ge, tge. 
  apply Genv.find_var_info_transf_partial with transf_fundef.
  exact TRANSF. 
Qed.

(** * Properties of control flow *)

Lemma transf_function_no_overflow:
  forall f tf,
  transf_function f = OK tf -> list_length_z tf <= Int.max_unsigned.
Proof.
  intros. monadInv H. destruct (zlt (list_length_z x) Int.max_unsigned); monadInv EQ0.
  rewrite list_length_z_cons. omega. 
Qed.

Lemma exec_straight_exec:
  forall fb f c ep tf tc c' rs m rs' m',
  transl_code_at_pc ge (rs PC) fb f c ep tf tc ->
  exec_straight tge tf tc rs m c' rs' m' ->
  plus step tge (State rs m) E0 (State rs' m').
Proof.
  intros. inv H.
  eapply exec_straight_steps_1; eauto.
  eapply transf_function_no_overflow; eauto.
  eapply functions_transl; eauto. 
Qed.

Lemma exec_straight_at:
  forall fb f c ep tf tc c' ep' tc' rs m rs' m',
  transl_code_at_pc ge (rs PC) fb f c ep tf tc ->
  transl_code f c' ep' = OK tc' ->
  exec_straight tge tf tc rs m tc' rs' m' ->
  transl_code_at_pc ge (rs' PC) fb f c' ep' tf tc'.
Proof.
  intros. inv H. 
  exploit exec_straight_steps_2; eauto. 
  eapply transf_function_no_overflow; eauto.
  eapply functions_transl; eauto.
  intros [ofs' [PC' CT']].
  rewrite PC'. constructor; auto.
Qed.

(** The following lemmas show that the translation from Mach to Asm
  preserves labels, in the sense that the following diagram commutes:
<<
                          translation
        Mach code ------------------------ Asm instr sequence
            |                                          |
            | Mach.find_label lbl       find_label lbl |
            |                                          |
            v                                          v
        Mach code tail ------------------- Asm instr seq tail
                          translation
>>
  The proof demands many boring lemmas showing that Asm constructor
  functions do not introduce new labels.

  In passing, we also prove a "is tail" property of the generated Asm code.
*)

Section TRANSL_LABEL.

Remark mk_mov_label:
  forall rd rs k c, mk_mov rd rs k = OK c -> tail_nolabel k c.
Proof.
  unfold mk_mov; intros. 
  destruct rd; try discriminate; destruct rs; TailNoLabel.
Qed.
Hint Resolve mk_mov_label: labels.

Remark mk_shrximm_label:
  forall n k c, mk_shrximm n k = OK c -> tail_nolabel k c.
Proof.
  intros. monadInv H; TailNoLabel.
Qed.
Hint Resolve mk_shrximm_label: labels.

Remark mk_intconv_label:
  forall f r1 r2 k c, mk_intconv f r1 r2 k = OK c -> 
  (forall r r', nolabel (f r r')) ->
  tail_nolabel k c.
Proof.
  unfold mk_intconv; intros. TailNoLabel. 
Qed.
Hint Resolve mk_intconv_label: labels.

Remark mk_smallstore_label:
  forall f addr r k c, mk_smallstore f addr r k = OK c -> 
  (forall r addr, nolabel (f r addr)) ->
  tail_nolabel k c.
Proof.
  unfold mk_smallstore; intros. TailNoLabel. 
Qed.
Hint Resolve mk_smallstore_label: labels.

Remark loadind_label:
  forall base ofs ty dst k c,
  loadind base ofs ty dst k = OK c ->
  tail_nolabel k c.
Proof.
  unfold loadind; intros. destruct ty.
  TailNoLabel.
  destruct (preg_of dst); TailNoLabel.
  discriminate.
Qed.

Remark storeind_label:
  forall base ofs ty src k c,
  storeind src base ofs ty k = OK c ->
  tail_nolabel k c.
Proof.
  unfold storeind; intros. destruct ty.
  TailNoLabel.
  destruct (preg_of src); TailNoLabel.
  discriminate.
Qed.

Remark mk_setcc_base_label:
  forall xc rd k,
  tail_nolabel k (mk_setcc_base xc rd k).
Proof.
  intros. destruct xc; simpl; destruct (ireg_eq rd EAX); TailNoLabel.
Qed.

Remark mk_setcc_label:
  forall xc rd k,
  tail_nolabel k (mk_setcc xc rd k).
Proof.
  intros. unfold mk_setcc. destruct (low_ireg rd).
  apply mk_setcc_base_label.
  eapply tail_nolabel_trans. apply mk_setcc_base_label. TailNoLabel.
Qed.

Remark mk_jcc_label:
  forall xc lbl' k,
  tail_nolabel k (mk_jcc xc lbl' k).
Proof.
  intros. destruct xc; simpl; TailNoLabel.
Qed.

Remark transl_cond_label:
  forall cond args k c,
  transl_cond cond args k = OK c ->
  tail_nolabel k c.
Proof.
  unfold transl_cond; intros.
  destruct cond; TailNoLabel.
  destruct (Int.eq_dec i Int.zero); TailNoLabel.
  destruct c0; simpl; TailNoLabel.
  destruct c0; simpl; TailNoLabel.
Qed.

Remark transl_op_label:
  forall op args r k c,
  transl_op op args r k = OK c ->
  tail_nolabel k c.
Proof.
  unfold transl_op; intros. destruct op; TailNoLabel.
  destruct (Int.eq_dec i Int.zero); TailNoLabel.
  destruct (Float.eq_dec f Float.zero); TailNoLabel.
  eapply tail_nolabel_trans. eapply transl_cond_label; eauto. eapply mk_setcc_label.  
Qed.

Remark transl_load_label:
  forall chunk addr args dest k c,
  transl_load chunk addr args dest k = OK c ->
  tail_nolabel k c.
Proof.
  intros. monadInv H. destruct chunk; TailNoLabel.
Qed.

Remark transl_store_label:
  forall chunk addr args src k c,
  transl_store chunk addr args src k = OK c ->
  tail_nolabel k c.
Proof.
  intros. monadInv H. destruct chunk; TailNoLabel.
Qed.

Lemma transl_instr_label:
  forall f i ep k c,
  transl_instr f i ep k = OK c ->
  match i with Mlabel lbl => c = Plabel lbl :: k | _ => tail_nolabel k c end.
Proof.
Opaque loadind.
  unfold transl_instr; intros; destruct i; TailNoLabel.
  eapply loadind_label; eauto.
  eapply storeind_label; eauto.
  eapply loadind_label; eauto.
  eapply tail_nolabel_trans; eapply loadind_label; eauto. 
  eapply transl_op_label; eauto.
  eapply transl_load_label; eauto.
  eapply transl_store_label; eauto.
  destruct s0; TailNoLabel.
  destruct s0; TailNoLabel.
  eapply tail_nolabel_trans. eapply transl_cond_label; eauto. eapply mk_jcc_label.  
Qed.

Lemma transl_instr_label':
  forall lbl f i ep k c,
  transl_instr f i ep k = OK c ->
  find_label lbl c = if Mach.is_label lbl i then Some k else find_label lbl k.
Proof.
  intros. exploit transl_instr_label; eauto.
  destruct i; try (intros [A B]; apply B). 
  intros. subst c. simpl. auto.
Qed.

Lemma transl_code_label:
  forall lbl f c ep tc,
  transl_code f c ep = OK tc ->
  match Mach.find_label lbl c with
  | None => find_label lbl tc = None
  | Some c' => exists tc', find_label lbl tc = Some tc' /\ transl_code f c' false = OK tc'
  end.
Proof.
  induction c; simpl; intros.
  inv H. auto.
  monadInv H. rewrite (transl_instr_label' lbl _ _ _ _ _ EQ0).
  generalize (Mach.is_label_correct lbl a). 
  destruct (Mach.is_label lbl a); intros.
  subst a. simpl in EQ. exists x; auto.
  eapply IHc; eauto.
Qed.

Lemma transl_find_label:
  forall lbl f tf,
  transf_function f = OK tf ->
  match Mach.find_label lbl f.(Mach.fn_code) with
  | None => find_label lbl tf = None
  | Some c => exists tc, find_label lbl tf = Some tc /\ transl_code f c false = OK tc
  end.
Proof.
  intros. monadInv H. destruct (zlt (list_length_z x) Int.max_unsigned); inv EQ0.
  simpl. eapply transl_code_label; eauto. rewrite transl_code'_transl_code in EQ; eauto. 
Qed.

End TRANSL_LABEL.

(** A valid branch in a piece of Mach code translates to a valid ``go to''
  transition in the generated PPC code. *)

Lemma find_label_goto_label:
  forall f tf lbl rs m c' b ofs,
  Genv.find_funct_ptr ge b = Some (Internal f) ->
  transf_function f = OK tf ->
  rs PC = Vptr b ofs ->
  Mach.find_label lbl f.(Mach.fn_code) = Some c' ->
  exists tc', exists rs',
    goto_label tf lbl rs m = Next rs' m  
  /\ transl_code_at_pc ge (rs' PC) b f c' false tf tc'
  /\ forall r, r <> PC -> rs'#r = rs#r.
Proof.
  intros. exploit (transl_find_label lbl f tf); eauto. rewrite H2. 
  intros [tc [A B]].
  exploit label_pos_code_tail; eauto. instantiate (1 := 0).
  intros [pos' [P [Q R]]].
  exists tc; exists (rs#PC <- (Vptr b (Int.repr pos'))).
  split. unfold goto_label. rewrite P. rewrite H1. auto.
  split. rewrite Pregmap.gss. constructor; auto. 
  rewrite Int.unsigned_repr. replace (pos' - 0) with pos' in Q.
  auto. omega.
  generalize (transf_function_no_overflow _ _ H0). omega.
  intros. apply Pregmap.gso; auto.
Qed.

(** Existence of return addresses *)

Lemma return_address_exists:
  forall f sg ros c, is_tail (Mcall sg ros :: c) f.(Mach.fn_code) ->
  exists ra, return_address_offset f c ra.
Proof.
  intros. eapply Asmgenproof0.return_address_exists; eauto. 
- intros. exploit transl_instr_label; eauto. 
  destruct i; try (intros [A B]; apply A). intros. subst c0. repeat constructor.
- intros. monadInv H0. 
  destruct (zlt (list_length_z x) Int.max_unsigned); inv EQ0.
  rewrite transl_code'_transl_code in EQ.
  exists x; exists true; split; auto. unfold fn_code. repeat constructor.
- exact transf_function_no_overflow.
Qed.

(** * Proof of semantic preservation *)

(** Semantic preservation is proved using simulation diagrams
  of the following form.
<<
           st1 --------------- st2
            |                   |
           t|                  *|t
            |                   |
            v                   v
           st1'--------------- st2'
>>
  The invariant is the [match_states] predicate below, which includes:
- The PPC code pointed by the PC register is the translation of
  the current Mach code sequence.
- Mach register values and PPC register values agree.
*)

Inductive match_states: Mach.state -> Asm.state -> Prop :=
  | match_states_intro:
      forall s fb sp c ep ms m m' rs f tf tc
        (STACKS: match_stack ge s)
        (FIND: Genv.find_funct_ptr ge fb = Some (Internal f))
        (MEXT: Mem.extends m m')
        (AT: transl_code_at_pc ge (rs PC) fb f c ep tf tc)
        (AG: agree ms sp rs)
        (DXP: ep = true -> rs#EDX = parent_sp s),
      match_states (Mach.State s fb sp c ms m)
                   (Asm.State rs m')
  | match_states_call:
      forall s fb ms m m' rs
        (STACKS: match_stack ge s)
        (MEXT: Mem.extends m m')
        (AG: agree ms (parent_sp s) rs)
        (ATPC: rs PC = Vptr fb Int.zero)
        (ATLR: rs RA = parent_ra s),
      match_states (Mach.Callstate s fb ms m)
                   (Asm.State rs m')
  | match_states_return:
      forall s ms m m' rs
        (STACKS: match_stack ge s)
        (MEXT: Mem.extends m m')
        (AG: agree ms (parent_sp s) rs)
        (ATPC: rs PC = parent_ra s),
      match_states (Mach.Returnstate s ms m)
                   (Asm.State rs m').

Lemma exec_straight_steps:
  forall s fb f rs1 i c ep tf tc m1' m2 m2' sp ms2,
  match_stack ge s ->
  Mem.extends m2 m2' ->
  Genv.find_funct_ptr ge fb = Some (Internal f) ->
  transl_code_at_pc ge (rs1 PC) fb f (i :: c) ep tf tc ->
  (forall k c (TR: transl_instr f i ep k = OK c),
   exists rs2,
       exec_straight tge tf c rs1 m1' k rs2 m2'
    /\ agree ms2 sp rs2
    /\ (it1_is_parent ep i = true -> rs2#EDX = parent_sp s)) ->
  exists st',
  plus step tge (State rs1 m1') E0 st' /\
  match_states (Mach.State s fb sp c ms2 m2) st'.
Proof.
  intros. inversion H2. subst. monadInv H7. 
  exploit H3; eauto. intros [rs2 [A [B C]]]. 
  exists (State rs2 m2'); split.
  eapply exec_straight_exec; eauto. 
  econstructor; eauto. eapply exec_straight_at; eauto.
Qed.

Lemma exec_straight_steps_goto:
  forall s fb f rs1 i c ep tf tc m1' m2 m2' sp ms2 lbl c',
  match_stack ge s ->
  Mem.extends m2 m2' ->
  Genv.find_funct_ptr ge fb = Some (Internal f) ->
  Mach.find_label lbl f.(Mach.fn_code) = Some c' ->
  transl_code_at_pc ge (rs1 PC) fb f (i :: c) ep tf tc ->
  it1_is_parent ep i = false ->
  (forall k c (TR: transl_instr f i ep k = OK c),
   exists jmp, exists k', exists rs2,
       exec_straight tge tf c rs1 m1' (jmp :: k') rs2 m2'
    /\ agree ms2 sp rs2
    /\ exec_instr tge tf jmp rs2 m2' = goto_label tf lbl rs2 m2') ->
  exists st',
  plus step tge (State rs1 m1') E0 st' /\
  match_states (Mach.State s fb sp c' ms2 m2) st'.
Proof.
  intros. inversion H3. subst. monadInv H9.
  exploit H5; eauto. intros [jmp [k' [rs2 [A [B C]]]]].
  generalize (functions_transl _ _ _ H7 H8); intro FN.
  generalize (transf_function_no_overflow _ _ H8); intro NOOV.
  exploit exec_straight_steps_2; eauto. 
  intros [ofs' [PC2 CT2]].
  exploit find_label_goto_label; eauto. 
  intros [tc' [rs3 [GOTO [AT' OTH]]]].
  exists (State rs3 m2'); split.
  eapply plus_right'.
  eapply exec_straight_steps_1; eauto. 
  econstructor; eauto.
  eapply find_instr_tail. eauto. 
  rewrite C. eexact GOTO.
  traceEq.
  econstructor; eauto.
  apply agree_exten with rs2; auto with asmgen.
  congruence.
Qed.

(** We need to show that, in the simulation diagram, we cannot
  take infinitely many Mach transitions that correspond to zero
  transitions on the PPC side.  Actually, all Mach transitions
  correspond to at least one Asm transition, except the
  transition from [Mach.Returnstate] to [Mach.State].
  So, the following integer measure will suffice to rule out
  the unwanted behaviour. *)

Definition measure (s: Mach.state) : nat :=
  match s with
  | Mach.State _ _ _ _ _ _ => 0%nat
  | Mach.Callstate _ _ _ _ => 0%nat
  | Mach.Returnstate _ _ _ => 1%nat
  end.

(** This is the simulation diagram.  We prove it by case analysis on the Mach transition. *)

Theorem step_simulation:
  forall S1 t S2, Mach.step return_address_offset ge S1 t S2 ->
  forall S1' (MS: match_states S1 S1'),
  (exists S2', plus step tge S1' t S2' /\ match_states S2 S2')
  \/ (measure S2 < measure S1 /\ t = E0 /\ match_states S2 S1')%nat.
Proof.
  induction 1; intros; inv MS.

- (* Mlabel *)
  left; eapply exec_straight_steps; eauto; intros. 
  monadInv TR. econstructor; split. apply exec_straight_one. simpl; eauto. auto. 
  split. apply agree_nextinstr; auto. simpl; congruence.

- (* Mgetstack *)
  unfold load_stack in H.
  exploit Mem.loadv_extends; eauto. intros [v' [A B]].
  rewrite (sp_val _ _ _ AG) in A.
  left; eapply exec_straight_steps; eauto. intros. simpl in TR.
  exploit loadind_correct; eauto. intros [rs' [P [Q R]]].
  exists rs'; split. eauto.
  split. eapply agree_set_mreg; eauto. congruence.
  simpl; congruence.

- (* Msetstack *)
  unfold store_stack in H.
  assert (Val.lessdef (rs src) (rs0 (preg_of src))). eapply preg_val; eauto.
  exploit Mem.storev_extends; eauto. intros [m2' [A B]]. 
  left; eapply exec_straight_steps; eauto.
  rewrite (sp_val _ _ _ AG) in A. intros. simpl in TR.
  exploit storeind_correct; eauto. intros [rs' [P Q]].
  exists rs'; split. eauto.
  split. eapply agree_undef_regs; eauto. 
  simpl; intros. rewrite Q; auto with asmgen.

- (* Mgetparam *)
  assert (f0 = f) by congruence; subst f0.
  unfold load_stack in *. 
  exploit Mem.loadv_extends. eauto. eexact H0. auto. 
  intros [parent' [A B]]. rewrite (sp_val _ _ _ AG) in A.
  exploit lessdef_parent_sp; eauto. clear B; intros B; subst parent'.
  exploit Mem.loadv_extends. eauto. eexact H1. auto. 
  intros [v' [C D]].
Opaque loadind.
  left; eapply exec_straight_steps; eauto; intros. 
  assert (DIFF: negb (mreg_eq dst DX) = true -> IR EDX <> preg_of dst).
    intros. change (IR EDX) with (preg_of DX). red; intros. 
    unfold proj_sumbool in H1. destruct (mreg_eq dst DX); try discriminate.
    elim n. eapply preg_of_injective; eauto.
  destruct ep; simpl in TR.
(* EDX contains parent *)
  exploit loadind_correct. eexact TR.
  instantiate (2 := rs0). rewrite DXP; eauto.  
  intros [rs1 [P [Q R]]].
  exists rs1; split. eauto. 
  split. eapply agree_set_mreg. eapply agree_set_mreg; eauto. congruence. auto.
  simpl; intros. rewrite R; auto.
(* EDX does not contain parent *)
  monadInv TR.
  exploit loadind_correct. eexact EQ0. eauto. intros [rs1 [P [Q R]]]. simpl in Q.
  exploit loadind_correct. eexact EQ. instantiate (2 := rs1). rewrite Q. eauto.
  intros [rs2 [S [T U]]]. 
  exists rs2; split. eapply exec_straight_trans; eauto.
  split. eapply agree_set_mreg. eapply agree_set_mreg; eauto. congruence. auto.
  simpl; intros. rewrite U; auto.

- (* Mop *)
  assert (eval_operation tge sp op rs##args m = Some v). 
    rewrite <- H. apply eval_operation_preserved. exact symbols_preserved.
  exploit eval_operation_lessdef. eapply preg_vals; eauto. eauto. eexact H0.
  intros [v' [A B]]. rewrite (sp_val _ _ _ AG) in A. 
  left; eapply exec_straight_steps; eauto; intros. simpl in TR.
  exploit transl_op_correct; eauto. intros [rs2 [P [Q R]]]. 
  assert (S: Val.lessdef v (rs2 (preg_of res))) by (eapply Val.lessdef_trans; eauto).
  exists rs2; split. eauto.
  split. eapply agree_set_undef_mreg; eauto.
  simpl; congruence.

- (* Mload *)
  assert (eval_addressing tge sp addr rs##args = Some a). 
    rewrite <- H. apply eval_addressing_preserved. exact symbols_preserved.
  exploit eval_addressing_lessdef. eapply preg_vals; eauto. eexact H1.
  intros [a' [A B]]. rewrite (sp_val _ _ _ AG) in A.
  exploit Mem.loadv_extends; eauto. intros [v' [C D]].
  left; eapply exec_straight_steps; eauto; intros. simpl in TR.
  exploit transl_load_correct; eauto. intros [rs2 [P [Q R]]]. 
  exists rs2; split. eauto.
  split. eapply agree_set_undef_mreg; eauto. congruence.
  simpl; congruence.

- (* Mstore *)
  assert (eval_addressing tge sp addr rs##args = Some a). 
    rewrite <- H. apply eval_addressing_preserved. exact symbols_preserved.
  exploit eval_addressing_lessdef. eapply preg_vals; eauto. eexact H1.
  intros [a' [A B]]. rewrite (sp_val _ _ _ AG) in A.
  assert (Val.lessdef (rs src) (rs0 (preg_of src))). eapply preg_val; eauto.
  exploit Mem.storev_extends; eauto. intros [m2' [C D]].
  left; eapply exec_straight_steps; eauto.
  intros. simpl in TR. 
  exploit transl_store_correct; eauto. intros [rs2 [P Q]]. 
  exists rs2; split. eauto.
  split. eapply agree_undef_regs; eauto.  
  simpl; congruence.

- (* Mcall *)
  assert (f0 = f) by congruence.  subst f0.
  inv AT. 
  assert (NOOV: list_length_z tf <= Int.max_unsigned).
    eapply transf_function_no_overflow; eauto.
  destruct ros as [rf|fid]; simpl in H; monadInv H5.
+ (* Indirect call *)
  assert (rs rf = Vptr f' Int.zero).
    destruct (rs rf); try discriminate.
    revert H; predSpec Int.eq Int.eq_spec i Int.zero; intros; congruence.
  assert (rs0 x0 = Vptr f' Int.zero).
    exploit ireg_val; eauto. rewrite H5; intros LD; inv LD; auto.
  generalize (code_tail_next_int _ _ _ _ NOOV H6). intro CT1.
  assert (TCA: transl_code_at_pc ge (Vptr fb (Int.add ofs Int.one)) fb f c false tf x).
    econstructor; eauto.
  exploit return_address_offset_correct; eauto. intros; subst ra.
  left; econstructor; split.
  apply plus_one. eapply exec_step_internal. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. eauto. 
  econstructor; eauto. 
  econstructor; eauto.
  eapply agree_sp_def; eauto.
  simpl. eapply agree_exten; eauto. intros. Simplifs.
  Simplifs. rewrite <- H2. auto. 
+ (* Direct call *)
  generalize (code_tail_next_int _ _ _ _ NOOV H6). intro CT1.
  assert (TCA: transl_code_at_pc ge (Vptr fb (Int.add ofs Int.one)) fb f c false tf x).
    econstructor; eauto.
  exploit return_address_offset_correct; eauto. intros; subst ra.
  left; econstructor; split.
  apply plus_one. eapply exec_step_internal. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. unfold symbol_offset. rewrite symbols_preserved. rewrite H. eauto.
  econstructor; eauto. 
  econstructor; eauto.
  eapply agree_sp_def; eauto.
  simpl. eapply agree_exten; eauto. intros. Simplifs.
  Simplifs. rewrite <- H2. auto.

- (* Mtailcall *)
  assert (f0 = f) by congruence.  subst f0.
  inv AT. 
  assert (NOOV: list_length_z tf <= Int.max_unsigned).
    eapply transf_function_no_overflow; eauto.
  rewrite (sp_val _ _ _ AG) in *. unfold load_stack in *.
  exploit Mem.loadv_extends. eauto. eexact H1. auto. simpl. intros [parent' [A B]].
  exploit Mem.loadv_extends. eauto. eexact H2. auto. simpl. intros [ra' [C D]].
  exploit lessdef_parent_sp; eauto. intros. subst parent'. clear B.
  exploit lessdef_parent_ra; eauto. intros. subst ra'. clear D.
  exploit Mem.free_parallel_extends; eauto. intros [m2' [E F]]. 
  destruct ros as [rf|fid]; simpl in H; monadInv H7.
+ (* Indirect call *)
  assert (rs rf = Vptr f' Int.zero).
    destruct (rs rf); try discriminate.
    revert H; predSpec Int.eq Int.eq_spec i Int.zero; intros; congruence.
  assert (rs0 x0 = Vptr f' Int.zero).
    exploit ireg_val; eauto. rewrite H7; intros LD; inv LD; auto.
  generalize (code_tail_next_int _ _ _ _ NOOV H8). intro CT1.
  left; econstructor; split.
  eapply plus_left. eapply exec_step_internal. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. rewrite C. rewrite A. rewrite <- (sp_val _ _ _ AG). rewrite E. eauto.
  apply star_one. eapply exec_step_internal. 
  transitivity (Val.add rs0#PC Vone). auto. rewrite <- H4. simpl. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. eauto. traceEq.
  econstructor; eauto.
  apply agree_set_other; auto. apply agree_nextinstr. apply agree_set_other; auto.
  eapply agree_change_sp; eauto. eapply parent_sp_def; eauto.
  Simplifs. rewrite Pregmap.gso; auto. 
  generalize (preg_of_not_SP rf). rewrite (ireg_of_eq _ _ EQ1). congruence.
+ (* Direct call *)
  generalize (code_tail_next_int _ _ _ _ NOOV H8). intro CT1.
  left; econstructor; split.
  eapply plus_left. eapply exec_step_internal. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. rewrite C. rewrite A. rewrite <- (sp_val _ _ _ AG). rewrite E. eauto.
  apply star_one. eapply exec_step_internal. 
  transitivity (Val.add rs0#PC Vone). auto. rewrite <- H4. simpl. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. eauto. traceEq.
  econstructor; eauto.
  apply agree_set_other; auto. apply agree_nextinstr. apply agree_set_other; auto.
  eapply agree_change_sp; eauto. eapply parent_sp_def; eauto.
  rewrite Pregmap.gss. unfold symbol_offset. rewrite symbols_preserved. rewrite H. auto.

- (* Mbuiltin *)
  inv AT. monadInv H3. 
  exploit functions_transl; eauto. intro FN.
  generalize (transf_function_no_overflow _ _ H2); intro NOOV.
  exploit external_call_mem_extends'; eauto. eapply preg_vals; eauto.
  intros [vres' [m2' [A [B [C D]]]]].
  left. econstructor; split. apply plus_one. 
  eapply exec_step_builtin. eauto. eauto.
  eapply find_instr_tail; eauto.
  eapply external_call_symbols_preserved'; eauto.
  exact symbols_preserved. exact varinfo_preserved.
  eauto.
  econstructor; eauto.
  instantiate (2 := tf); instantiate (1 := x).
  unfold nextinstr_nf, nextinstr. rewrite Pregmap.gss.
  rewrite undef_regs_other. rewrite set_pregs_other_2. rewrite undef_regs_other_2.
  rewrite <- H0. simpl. econstructor; eauto.
  eapply code_tail_next_int; eauto.
  rewrite preg_notin_charact. intros. auto with asmgen.
  rewrite preg_notin_charact. intros. auto with asmgen.
  auto with asmgen.
  simpl; intros. intuition congruence.
  apply agree_nextinstr_nf. eapply agree_set_mregs; auto.
  eapply agree_undef_regs; eauto. intros; apply undef_regs_other_2; auto. 
  congruence.

- (* Mannot *)
  inv AT. monadInv H4. 
  exploit functions_transl; eauto. intro FN.
  generalize (transf_function_no_overflow _ _ H3); intro NOOV.
  exploit annot_arguments_match; eauto. intros [vargs' [P Q]]. 
  exploit external_call_mem_extends'; eauto.
  intros [vres' [m2' [A [B [C D]]]]].
  left. econstructor; split. apply plus_one. 
  eapply exec_step_annot. eauto. eauto.
  eapply find_instr_tail; eauto. eauto.
  eapply external_call_symbols_preserved'; eauto.
  exact symbols_preserved. exact varinfo_preserved.
  eapply match_states_intro with (ep := false); eauto with coqlib.
  unfold nextinstr. rewrite Pregmap.gss. 
  rewrite <- H1; simpl. econstructor; eauto.
  eapply code_tail_next_int; eauto. 
  apply agree_nextinstr. auto.
  congruence.

- (* Mgoto *)
  assert (f0 = f) by congruence. subst f0.
  inv AT. monadInv H4. 
  exploit find_label_goto_label; eauto. intros [tc' [rs' [GOTO [AT2 INV]]]].
  left; exists (State rs' m'); split.
  apply plus_one. econstructor; eauto.
  eapply functions_transl; eauto.
  eapply find_instr_tail; eauto.
  simpl; eauto.
  econstructor; eauto.
  eapply agree_exten; eauto with asmgen.
  congruence.

- (* Mcond true *)
  assert (f0 = f) by congruence. subst f0.
  exploit eval_condition_lessdef. eapply preg_vals; eauto. eauto. eauto. intros EC.
  left; eapply exec_straight_steps_goto; eauto.
  intros. simpl in TR.
  destruct (transl_cond_correct tge tf cond args _ _ rs0 m' TR)
  as [rs' [A [B C]]]. 
  rewrite EC in B.
  destruct (testcond_for_condition cond); simpl in *.
(* simple jcc *)
  exists (Pjcc c1 lbl); exists k; exists rs'.
  split. eexact A.
  split. eapply agree_exten; eauto. 
  simpl. rewrite B. auto.
(* jcc; jcc *)
  destruct (eval_testcond c1 rs') as [b1|] eqn:TC1;
  destruct (eval_testcond c2 rs') as [b2|] eqn:TC2; inv B.
  destruct b1.   
  (* first jcc jumps *)
  exists (Pjcc c1 lbl); exists (Pjcc c2 lbl :: k); exists rs'.
  split. eexact A.
  split. eapply agree_exten; eauto. 
  simpl. rewrite TC1. auto.
  (* second jcc jumps *)
  exists (Pjcc c2 lbl); exists k; exists (nextinstr rs').
  split. eapply exec_straight_trans. eexact A. 
  eapply exec_straight_one. simpl. rewrite TC1. auto. auto.
  split. eapply agree_exten; eauto.
  intros; Simplifs.
  simpl. rewrite eval_testcond_nextinstr. rewrite TC2.
  destruct b2; auto || discriminate.
(* jcc2 *)
  destruct (eval_testcond c1 rs') as [b1|] eqn:TC1;
  destruct (eval_testcond c2 rs') as [b2|] eqn:TC2; inv B.
  destruct (andb_prop _ _ H3). subst. 
  exists (Pjcc2 c1 c2 lbl); exists k; exists rs'.
  split. eexact A.
  split. eapply agree_exten; eauto. 
  simpl. rewrite TC1; rewrite TC2; auto.

- (* Mcond false *)
  exploit eval_condition_lessdef. eapply preg_vals; eauto. eauto. eauto. intros EC.
  left; eapply exec_straight_steps; eauto. intros. simpl in TR. 
  destruct (transl_cond_correct tge tf cond args _ _ rs0 m' TR)
  as [rs' [A [B C]]]. 
  rewrite EC in B.
  destruct (testcond_for_condition cond); simpl in *.
(* simple jcc *)
  econstructor; split.
  eapply exec_straight_trans. eexact A. 
  apply exec_straight_one. simpl. rewrite B. eauto. auto. 
  split. apply agree_nextinstr. eapply agree_exten; eauto.
  simpl; congruence.
(* jcc ; jcc *)
  destruct (eval_testcond c1 rs') as [b1|] eqn:TC1;
  destruct (eval_testcond c2 rs') as [b2|] eqn:TC2; inv B.
  destruct (orb_false_elim _ _ H1); subst.
  econstructor; split.
  eapply exec_straight_trans. eexact A. 
  eapply exec_straight_two. simpl. rewrite TC1. eauto. auto. 
  simpl. rewrite eval_testcond_nextinstr. rewrite TC2. eauto. auto. auto.
  split. apply agree_nextinstr. apply agree_nextinstr. eapply agree_exten; eauto.
  simpl; congruence.
(* jcc2 *)
  destruct (eval_testcond c1 rs') as [b1|] eqn:TC1;
  destruct (eval_testcond c2 rs') as [b2|] eqn:TC2; inv B.
  exists (nextinstr rs'); split.
  eapply exec_straight_trans. eexact A. 
  apply exec_straight_one. simpl. 
  rewrite TC1; rewrite TC2. 
  destruct b1. simpl in *. subst b2. auto. auto.
  auto.
  split. apply agree_nextinstr. eapply agree_exten; eauto.
  rewrite H1; congruence.

- (* Mjumptable *)
  assert (f0 = f) by congruence. subst f0.
  inv AT. monadInv H6. 
  exploit functions_transl; eauto. intro FN.
  generalize (transf_function_no_overflow _ _ H5); intro NOOV.
  exploit find_label_goto_label; eauto. 
  intros [tc' [rs' [A [B C]]]].
  exploit ireg_val; eauto. rewrite H. intros LD; inv LD.
  left; econstructor; split.
  apply plus_one. econstructor; eauto. 
  eapply find_instr_tail; eauto. 
  simpl. rewrite <- H9. unfold Mach.label in H0; unfold label; rewrite H0. eauto.
  econstructor; eauto. 
Transparent destroyed_by_jumptable. 
  simpl. eapply agree_exten; eauto. intros. rewrite C; auto with asmgen.
  congruence.

- (* Mreturn *)
  assert (f0 = f) by congruence. subst f0.
  inv AT. 
  assert (NOOV: list_length_z tf <= Int.max_unsigned).
    eapply transf_function_no_overflow; eauto.
  rewrite (sp_val _ _ _ AG) in *. unfold load_stack in *.
  exploit Mem.loadv_extends. eauto. eexact H0. auto. simpl. intros [parent' [A B]]. 
  exploit lessdef_parent_sp; eauto. intros. subst parent'. clear B.
  exploit Mem.loadv_extends. eauto. eexact H1. auto. simpl. intros [ra' [C D]]. 
  exploit lessdef_parent_ra; eauto. intros. subst ra'. clear D.
  exploit Mem.free_parallel_extends; eauto. intros [m2' [E F]].
  monadInv H6.
  exploit code_tail_next_int; eauto. intro CT1.
  left; econstructor; split.
  eapply plus_left. eapply exec_step_internal. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. rewrite C. rewrite A. rewrite <- (sp_val _ _ _ AG). rewrite E. eauto.
  apply star_one. eapply exec_step_internal. 
  transitivity (Val.add rs0#PC Vone). auto. rewrite <- H3. simpl. eauto.
  eapply functions_transl; eauto. eapply find_instr_tail; eauto. 
  simpl. eauto. traceEq.
  constructor; auto.
  apply agree_set_other; auto. apply agree_nextinstr. apply agree_set_other; auto.
  eapply agree_change_sp; eauto. eapply parent_sp_def; eauto.

- (* internal function *)
  exploit functions_translated; eauto. intros [tf [A B]]. monadInv B.
  generalize EQ; intros EQ'. monadInv EQ'. rewrite transl_code'_transl_code in EQ0.
  destruct (zlt (list_length_z x0) Int.max_unsigned); inversion EQ1. clear EQ1.
  unfold store_stack in *. 
  exploit Mem.alloc_extends. eauto. eauto. apply Zle_refl. apply Zle_refl. 
  intros [m1' [C D]].
  exploit Mem.storev_extends. eexact D. eexact H1. eauto. eauto. 
  intros [m2' [F G]].
  exploit Mem.storev_extends. eexact G. eexact H2. eauto. eauto. 
  intros [m3' [P Q]].
  left; econstructor; split.
  apply plus_one. econstructor; eauto. 
  subst x; simpl.
  rewrite Int.unsigned_zero. simpl. eauto.
  simpl. rewrite C. simpl in F. rewrite (sp_val _ _ _ AG) in F. rewrite F.
  simpl in P. rewrite ATLR. rewrite P. eauto.
  econstructor; eauto.
  unfold nextinstr. rewrite Pregmap.gss. repeat rewrite Pregmap.gso; auto with asmgen. 
  rewrite ATPC. simpl. constructor; eauto.
  subst x. unfold fn_code. eapply code_tail_next_int. rewrite list_length_z_cons. omega. 
  constructor. 
  apply agree_nextinstr. eapply agree_change_sp; eauto.
Transparent destroyed_at_function_entry.
  apply agree_undef_regs with rs0; eauto.
  simpl; intros. apply Pregmap.gso; auto with asmgen. tauto. 
  congruence. 
  intros. Simplifs. eapply agree_sp; eauto.

- (* external function *)
  exploit functions_translated; eauto.
  intros [tf [A B]]. simpl in B. inv B.
  exploit extcall_arguments_match; eauto. 
  intros [args' [C D]].
  exploit external_call_mem_extends'; eauto.
  intros [res' [m2' [P [Q [R S]]]]].
  left; econstructor; split.
  apply plus_one. eapply exec_step_external; eauto. 
  eapply external_call_symbols_preserved'; eauto. 
  exact symbols_preserved. exact varinfo_preserved.
  econstructor; eauto.
  unfold loc_external_result.
  apply agree_set_other; auto. apply agree_set_mregs; auto.

- (* return *)
  inv STACKS. simpl in *.
  right. split. omega. split. auto.
  econstructor; eauto. rewrite ATPC; eauto. congruence.
Qed.

Lemma transf_initial_states:
  forall st1, Mach.initial_state prog st1 ->
  exists st2, Asm.initial_state tprog st2 /\ match_states st1 st2.
Proof.
  intros. inversion H. unfold ge0 in *.
  econstructor; split.
  econstructor.
  eapply Genv.init_mem_transf_partial; eauto.
  replace (symbol_offset (Genv.globalenv tprog) (prog_main tprog) Int.zero)
     with (Vptr fb Int.zero).
  econstructor; eauto.
  constructor.
  apply Mem.extends_refl.
  split. auto. simpl. congruence. intros. rewrite Regmap.gi. auto. 
  unfold symbol_offset. 
  rewrite (transform_partial_program_main _ _ TRANSF).
  rewrite symbols_preserved. 
  unfold ge; rewrite H1. auto.
Qed.

Lemma transf_final_states:
  forall st1 st2 r, 
  match_states st1 st2 -> Mach.final_state st1 r -> Asm.final_state st2 r.
Proof.
  intros. inv H0. inv H. constructor. auto. 
  compute in H1. inv H1.  
  generalize (preg_val _ _ _ AX AG). rewrite H2. intros LD; inv LD. auto.
Qed.

Theorem transf_program_correct:
  forward_simulation (Mach.semantics return_address_offset prog) (Asm.semantics tprog).
Proof.
  eapply forward_simulation_star with (measure := measure).
  eexact symbols_preserved.
  eexact transf_initial_states.
  eexact transf_final_states.
  exact step_simulation.
Qed.

End PRESERVATION.