summaryrefslogtreecommitdiffstats
path: root/decompile.c
blob: 1b0fbdab1c113baca3f15f762d549eac6ef32076 (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
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
/******************************************************************************
  Copyright (c) 1995, 1996 Xerox Corporation.  All rights reserved.
  Portions of this code were written by Stephen White, aka ghond.
  Use and copying of this software and preparation of derivative works based
  upon this software are permitted.  Any distribution of this software or
  derivative works must comply with all applicable United States export
  control laws.  This software is made available AS IS, and Xerox Corporation
  makes no warranty about the software, its performance or its conformity to
  any specification.  Any person obtaining a copy of this software is requested
  to send their name and post office or electronic mail address to:
    Pavel Curtis
    Xerox PARC
    3333 Coyote Hill Rd.
    Palo Alto, CA 94304
    Pavel@Xerox.Com
 *****************************************************************************/

#include "ast.h"
#include "decompile.h"
#include "exceptions.h"
#include "opcode.h"
#include "program.h"
#include "storage.h"
#include "utils.h"

static Program *program;
static Expr **expr_stack;
static int top_expr_stack;

static Byte *hot_byte;
static void *hot_node;
static enum {
    TOP, ENDBODY, BOTTOM, DONE
} hot_position;

static int lineno;

static void
push_expr(Expr * expr)
{
    expr_stack[top_expr_stack++] = expr;
}

static Expr *
pop_expr(void)
{
    if (!top_expr_stack)
	panic("Empty expr stack in DECOMPILE!");
    return expr_stack[--top_expr_stack];
}

#define ADD_STMT(stmt)		\
do {				\
    Stmt *temp = stmt;		\
				\
    *stmt_sink = temp;		\
    stmt_sink = &(temp->next);	\
    stmt_start = ptr - bc.vector;\
} while (0);

#define ADD_ARM(arm)		\
do {				\
    Cond_Arm *temp = arm;	\
				\
    *arm_sink = temp;		\
    arm_sink = &(temp->next);	\
} while (0);

#define SKIP_BYTES(n)  ((void)(ptr += n))
#define READ_BYTES(n)			\
  (ptr += n,				\
   (n == 1				\
    ? ptr[-1]				\
    : (n == 2				\
       ? ((unsigned) ptr[-2] << 8)	\
         + ptr[-1]			\
       : ((unsigned) ptr[-4] << 24)	\
         + ((unsigned) ptr[-3] << 16)	\
         + ((unsigned) ptr[-2] << 8)	\
         + ptr[-1])))

#define READ_LABEL()	READ_BYTES(bc.numbytes_label)
#define READ_LITERAL()	program->literals[READ_BYTES(bc.numbytes_literal)]
#define READ_FORK()	program->fork_vectors[READ_BYTES(bc.numbytes_fork)]
#define READ_ID()	READ_BYTES(bc.numbytes_var_name)
#define READ_STACK()	SKIP_BYTES(bc.numbytes_stack)

#define READ_JUMP(is_hot)	read_jump(bc.numbytes_label, &ptr, &is_hot)

static unsigned
read_jump(unsigned numbytes_label, Byte ** p, int *is_hot)
{
    Byte *ptr = *p;
    unsigned label;

    *is_hot = (ptr == hot_byte);
    if (*ptr++ != OP_JUMP)
	panic("Missing JUMP in DECOMPILE!");

    label = READ_BYTES(numbytes_label);
    *p = ptr;

    return label;
}

#define HOT(is_hot, n)		(node = n, is_hot ? (hot_node = node) : node)
#define HOT1(is_hot, kid, n)	HOT(is_hot || hot_node == kid, n)
#define HOT2(is_hot, kid1, kid2, n) \
				HOT1(is_hot || hot_node == kid1, kid2, n)
#define HOT3(is_hot, kid1, kid2, kid3, n) \
				HOT2(is_hot || hot_node == kid1, kid2, kid3, n)
#define HOT4(is_hot, kid1, kid2, kid3, kid4, n) \
			HOT3(is_hot || hot_node == kid1, kid2, kid3, kid4, n)

#define HOT_OP(n)		HOT(op_hot, n)
#define HOT_OP1(kid, n)		HOT1(op_hot, kid, n)
#define HOT_OP2(kid1, kid2, n)	HOT2(op_hot, kid1, kid2, n)
#define HOT_OP3(kid1, kid2, kid3, n)	\
				HOT3(op_hot, kid1, kid2, kid3, n)

#define HOT_POS(is_hot, n, pos)	\
		if (is_hot) { hot_node = n; hot_position = pos; }
#define HOT_BOTTOM(is_hot, n)	HOT_POS(is_hot, n, BOTTOM)

#define DECOMPILE(bc, start, end, stmt_sink, arm_sink)	\
	    (ptr = decompile(bc, start, end, stmt_sink, arm_sink))

static Byte *
decompile(Bytecodes bc, Byte * start, Byte * end, Stmt ** stmt_sink,
	  Cond_Arm ** arm_sink)
{
    /*** The reader will likely find it useful to consult the file
     *** `MOOCodeSequences.txt' in this directory while reading this function.
     ***/

    Byte *ptr = start;
    unsigned stmt_start = start - bc.vector;
    unsigned jump_len = bc.numbytes_label + 1;
    Stmt *s;
    Expr *e;
    enum Expr_Kind kind;
    void *node;
    int asgn_hot = 0;

    if (stmt_sink)
	*stmt_sink = 0;
    if (arm_sink)
	*arm_sink = 0;

    while (ptr < end) {
	int op_hot = (ptr == hot_byte);
	Opcode op = *ptr++;

	if (IS_PUSH_n(op)) {
	    e = alloc_expr(EXPR_ID);
	    e->e.id = PUSH_n_INDEX(op);
	    push_expr(HOT_OP(e));
	    continue;
#ifdef BYTECODE_REDUCE_REF
	} else if (IS_PUSH_CLEAR_n(op)) {
	    e = alloc_expr(EXPR_ID);
	    e->e.id = PUSH_CLEAR_n_INDEX(op);
	    push_expr(HOT_OP(e));
	    continue;
#endif				/* BYTECODE_REDUCE_REF */
	} else if (IS_PUT_n(op)) {
	    e = alloc_expr(EXPR_ID);
	    e->e.id = PUT_n_INDEX(op);
	    e = alloc_binary(EXPR_ASGN, e, pop_expr());
	    push_expr(HOT_OP1(e->e.bin.rhs, e));
	    continue;
	} else if (IS_OPTIM_NUM_OPCODE(op)) {
	    e = alloc_var(TYPE_INT);
	    e->e.var.v.num = OPCODE_TO_OPTIM_NUM(op);
	    push_expr(HOT_OP(e));
	    continue;
	}
	switch (op) {
	case OP_IF:
	    {
		unsigned next = READ_LABEL();
		Expr *condition = pop_expr();
		Stmt *arm_stmts;
		Cond_Arm *arm;
		unsigned done;
		int jump_hot;

		s = alloc_stmt(STMT_COND);
		DECOMPILE(bc, ptr, bc.vector + next - jump_len, &arm_stmts, 0);
		arm = s->s.cond.arms = alloc_cond_arm(condition, arm_stmts);
		HOT_OP1(condition, arm);
		done = READ_JUMP(jump_hot);
		HOT_BOTTOM(jump_hot, arm);
		DECOMPILE(bc, ptr, bc.vector + done, &(s->s.cond.otherwise),
			  &(arm->next));

		ADD_STMT(s);
	    }
	    break;
	case OP_EIF:
	    {
		unsigned next = READ_LABEL();
		Expr *condition = pop_expr();
		Stmt *arm_stmts;
		Cond_Arm *arm;
		unsigned done;
		int jump_hot;

		DECOMPILE(bc, ptr, bc.vector + next - jump_len, &arm_stmts, 0);
		ADD_ARM(arm = alloc_cond_arm(condition, arm_stmts));
		HOT_OP1(condition, arm);
		done = READ_JUMP(jump_hot);
		HOT_BOTTOM(jump_hot, arm);
		if (bc.vector + done != end)
		    panic("ELSEIF jumps to wrong place in DECOMPILE!");
		stmt_start = ptr - bc.vector;
	    }
	    break;
	case OP_FOR_LIST:
	    {
		unsigned top = (ptr - 1) - bc.vector;
		int id = READ_ID();
		unsigned done = READ_LABEL();
		Expr *one = pop_expr();
		Expr *list = pop_expr();
		int jump_hot;

		if (one->kind != EXPR_VAR
		    || one->e.var.type != TYPE_INT
		    || one->e.var.v.num != 1)
		    panic("Not a literal one in DECOMPILE!");
		else
		    dealloc_node(one);
		s = alloc_stmt(STMT_LIST);
		s->s.list.id = id;
		s->s.list.expr = list;
		DECOMPILE(bc, ptr, bc.vector + done - jump_len,
			  &(s->s.list.body), 0);
		if (top != READ_JUMP(jump_hot))
		    panic("FOR_LIST jumps to wrong place in DECOMPILE!");
		HOT_BOTTOM(jump_hot, s);
		ADD_STMT(HOT_OP2(one, list, s));
	    }
	    break;
	case OP_FOR_RANGE:
	    {
		unsigned top = (ptr - 1) - bc.vector;
		int id = READ_ID();
		unsigned done = READ_LABEL();
		Expr *to = pop_expr();
		Expr *from = pop_expr();
		int jump_hot;

		s = alloc_stmt(STMT_RANGE);
		s->s.range.id = id;
		s->s.range.from = from;
		s->s.range.to = to;
		DECOMPILE(bc, ptr, bc.vector + done - jump_len,
			  &(s->s.range.body), 0);
		if (top != READ_JUMP(jump_hot))
		    panic("FOR_RANGE jumps to wrong place in DECOMPILE!");
		HOT_BOTTOM(jump_hot, s);
		ADD_STMT(HOT_OP2(from, to, s));
	    }
	    break;
	case OP_WHILE:
	    s = alloc_stmt(STMT_WHILE);
	    s->s.loop.id = -1;
	  finish_while:
	    {
		unsigned top = stmt_start;
		unsigned done = READ_LABEL();
		Expr *condition = pop_expr();
		int jump_hot;

		s->s.loop.condition = condition;
		DECOMPILE(bc, ptr, bc.vector + done - jump_len,
			  &(s->s.loop.body), 0);
		if (top != READ_JUMP(jump_hot))
		    panic("WHILE jumps to wrong place in DECOMPILE!");
		HOT_BOTTOM(jump_hot, s);
		ADD_STMT(HOT_OP1(condition, s));
	    }
	    break;
	case OP_FORK:
	case OP_FORK_WITH_ID:
	    {
		Bytecodes fbc;
		int id;
		Expr *time = pop_expr();

		fbc = READ_FORK();
		id = (op == OP_FORK ? -1 : READ_ID());
		s = alloc_stmt(STMT_FORK);
		s->s.fork.id = id;
		s->s.fork.time = time;
		(void) decompile(fbc, fbc.vector, fbc.vector + fbc.size,
				 &(s->s.fork.body), 0);
		HOT_BOTTOM(hot_byte == fbc.vector + fbc.size - 1, s);
		ADD_STMT(HOT_OP1(time, s));
	    }
	    break;
	case OP_POP:
	    s = alloc_stmt(STMT_EXPR);
	    e = s->s.expr = pop_expr();
	    ADD_STMT(HOT_OP1(e, s));
	    break;
	case OP_RETURN:
	case OP_RETURN0:
	    s = alloc_stmt(STMT_RETURN);
	    e = s->s.expr = (op == OP_RETURN ? pop_expr() : 0);
	    ADD_STMT(HOT(op_hot || (e && e == hot_node), s));
	    break;
	case OP_DONE:
	    if (ptr != end)
		panic("DONE not at end in DECOMPILE!");
	    break;
	case OP_IMM:
	    e = alloc_expr(EXPR_VAR);
	    e->e.var = var_ref(READ_LITERAL());
	    push_expr(HOT_OP(e));
	    break;
	case OP_G_PUSH:
	    e = alloc_expr(EXPR_ID);
	    e->e.id = READ_ID();
	    push_expr(HOT_OP(e));
	    break;
	case OP_AND:
	case OP_OR:
	    {
		unsigned done = READ_LABEL();

		e = pop_expr();
		DECOMPILE(bc, ptr, bc.vector + done, 0, 0);
		if (ptr != bc.vector + done)
		    panic("AND/OR jumps to wrong place in DECOMPILE!");
		e = alloc_binary(op == OP_AND ? EXPR_AND : EXPR_OR,
				 e, pop_expr());
		push_expr(HOT_OP2(e->e.bin.lhs, e->e.bin.rhs, e));
	    }
	    break;
	case OP_UNARY_MINUS:
	case OP_NOT:
	    e = alloc_expr(op == OP_NOT ? EXPR_NOT : EXPR_NEGATE);
	    e->e.expr = pop_expr();
	    push_expr(HOT_OP1(e->e.expr, e));
	    break;
	case OP_GET_PROP:
	case OP_PUSH_GET_PROP:
	    kind = EXPR_PROP;
	    goto finish_binary;
	case OP_EQ:
	    kind = EXPR_EQ;
	    goto finish_binary;
	case OP_NE:
	    kind = EXPR_NE;
	    goto finish_binary;
	case OP_LT:
	    kind = EXPR_LT;
	    goto finish_binary;
	case OP_LE:
	    kind = EXPR_LE;
	    goto finish_binary;
	case OP_GT:
	    kind = EXPR_GT;
	    goto finish_binary;
	case OP_GE:
	    kind = EXPR_GE;
	    goto finish_binary;
	case OP_IN:
	    kind = EXPR_IN;
	    goto finish_binary;
	case OP_ADD:
	    kind = EXPR_PLUS;
	    goto finish_binary;
	case OP_MINUS:
	    kind = EXPR_MINUS;
	    goto finish_binary;
	case OP_MULT:
	    kind = EXPR_TIMES;
	    goto finish_binary;
	case OP_DIV:
	    kind = EXPR_DIVIDE;
	    goto finish_binary;
	case OP_MOD:
	    kind = EXPR_MOD;
	    goto finish_binary;
	case OP_REF:
	case OP_PUSH_REF:
	    kind = EXPR_INDEX;
	  finish_binary:
	    e = pop_expr();
	    e = alloc_binary(kind, pop_expr(), e);
	    push_expr(HOT_OP2(e->e.bin.lhs, e->e.bin.rhs, e));
	    break;
	case OP_RANGE_REF:
	    {
		Expr *e1 = pop_expr();
		Expr *e2 = pop_expr();

		e = alloc_expr(EXPR_RANGE);
		e->e.range.base = pop_expr();
		e->e.range.from = e2;
		e->e.range.to = e1;
		push_expr(HOT_OP3(e1, e2, e->e.range.base, e));
	    }
	    break;
	case OP_BI_FUNC_CALL:
	    {
		Expr *a = pop_expr();

		if (a->kind != EXPR_LIST)
		    panic("Missing arglist for BI_FUNC_CALL in DECOMPILE!");
		e = alloc_expr(EXPR_CALL);
		e->e.call.args = a->e.list;
		dealloc_node(a);
		e->e.call.func = READ_BYTES(1);
		push_expr(HOT_OP1(a, e));
	    }
	    break;
	case OP_CALL_VERB:
	    {
		Expr *a = pop_expr();
		Expr *e2 = pop_expr();

		if (a->kind != EXPR_LIST)
		    panic("Missing arglist for CALL_VERB in DECOMPILE!");
		e = alloc_verb(pop_expr(), e2, a->e.list);
		dealloc_node(a);
		push_expr(HOT_OP3(e->e.verb.obj, a, e2, e));
	    }
	    break;
	case OP_IF_QUES:
	    {
		unsigned label = READ_LABEL();
		int jump_hot;

		e = alloc_expr(EXPR_COND);
		e->e.cond.condition = pop_expr();
		DECOMPILE(bc, ptr, bc.vector + label - jump_len, 0, 0);
		label = READ_JUMP(jump_hot);
		e->e.cond.consequent = pop_expr();
		DECOMPILE(bc, ptr, bc.vector + label, 0, 0);
		if (ptr != bc.vector + label)
		    panic("THEN jumps to wrong place in DECOMPILE!");
		e->e.cond.alternate = pop_expr();
		push_expr(HOT3(op_hot || jump_hot, e->e.cond.condition,
			       e->e.cond.consequent, e->e.cond.alternate,
			       e));
	    }
	    break;
	case OP_PUT_TEMP:
	    /* Ignore; following RANGESET or INDEXSET does the work */
	    if (op_hot)
		asgn_hot = 1;
	    break;
	case OP_INDEXSET:
	    /* Most of the lvalue has already been constructed on the stack.
	     * Add the final indexing.
	     */
	    {
		Expr *rvalue = pop_expr();
		Expr *index = pop_expr();

		e = alloc_binary(EXPR_INDEX, pop_expr(), index);
		push_expr(HOT3(op_hot || asgn_hot,
			       e->e.bin.lhs, index, rvalue,
			       alloc_binary(EXPR_ASGN, e, rvalue)));
	    }
	  finish_indexed_assignment:
	    /* The remainder of this complex assignment code sequence is
	     * useless for the purpose of decompilation.
	     */
	    asgn_hot = 0;
	    while (*ptr != OP_PUSH_TEMP) {
		if (ptr == hot_byte)	/* it's our assignment expression */
		    hot_node = expr_stack[top_expr_stack];
		ptr++;
	    }
	    ptr++;
	    break;
	case OP_G_PUT:
	    e = alloc_expr(EXPR_ID);
	    e->e.id = READ_ID();
	    e = alloc_binary(EXPR_ASGN, e, pop_expr());
	    push_expr(HOT_OP1(e->e.bin.rhs, e));
	    break;
	case OP_PUT_PROP:
	    {
		Expr *rvalue = pop_expr();

		e = pop_expr();
		e = alloc_binary(EXPR_PROP, pop_expr(), e);
		push_expr(HOT_OP3(e->e.bin.lhs, e->e.bin.rhs, rvalue,
				  alloc_binary(EXPR_ASGN, e, rvalue)));
	    }
	    break;
	case OP_MAKE_EMPTY_LIST:
	    e = alloc_expr(EXPR_LIST);
	    e->e.list = 0;
	    push_expr(HOT_OP(e));
	    break;
	case OP_MAKE_SINGLETON_LIST:
	    e = alloc_expr(EXPR_LIST);
	    e->e.list = alloc_arg_list(ARG_NORMAL, pop_expr());
	    push_expr(HOT_OP1(e->e.list->expr, e));
	    break;
	case OP_CHECK_LIST_FOR_SPLICE:
	    e = alloc_expr(EXPR_LIST);
	    e->e.list = alloc_arg_list(ARG_SPLICE, pop_expr());
	    push_expr(HOT_OP1(e->e.list->expr, e));
	    break;
	case OP_LIST_ADD_TAIL:
	case OP_LIST_APPEND:
	    {
		Expr *list;
		Arg_List *a;

		e = pop_expr();
		list = pop_expr();
		if (list->kind != EXPR_LIST)
		    panic("Missing list expression in DECOMPILE!");
		for (a = list->e.list; a->next; a = a->next);
		a->next = alloc_arg_list(op == OP_LIST_APPEND ? ARG_SPLICE
					 : ARG_NORMAL, e);
		push_expr(HOT_OP1(e, list));
	    }
	    break;
	case OP_PUSH_TEMP:
	case OP_JUMP:
	    panic("Unexpected opcode in DECOMPILE!");
	    break;
	case OP_EXTENDED:
	    {
		Extended_Opcode eop = *ptr++;

		switch (eop) {
		case EOP_RANGESET:
		    /* Most of the lvalue has already been constructed on the
		     * stack.  Add the final subranging.
		     */
		    {
			Expr *rvalue = pop_expr();

			e = alloc_expr(EXPR_RANGE);
			e->e.range.to = pop_expr();
			e->e.range.from = pop_expr();
			e->e.range.base = pop_expr();
			push_expr(HOT4(op_hot || asgn_hot,
				       e->e.range.base, e->e.range.from,
				       e->e.range.to, rvalue,
				    alloc_binary(EXPR_ASGN, e, rvalue)));
		    }
		    goto finish_indexed_assignment;
		case EOP_LENGTH:
		    READ_STACK();
		    e = alloc_expr(EXPR_LENGTH);
		    push_expr(HOT_OP(e));
		    break;
		case EOP_EXP:
		    kind = EXPR_EXP;
		    goto finish_binary;
		case EOP_SCATTER:
		    {
			Scatter *sc, **scp;
			int nargs = *ptr++;
			int rest = (ptr++, *ptr++);	/* skip nreq */
			int *next_label = 0;
			int i, done, is_hot = op_hot;

			for (i = 1, scp = &sc;
			     i <= nargs;
			     i++, scp = &((*scp)->next)) {
			    int id = READ_ID();
			    int label = READ_LABEL();

			    *scp = alloc_scatter(i == rest ? SCAT_REST :
					       label == 0 ? SCAT_REQUIRED
						 : SCAT_OPTIONAL,
						 id, 0);
			    if (label > 1) {
				(*scp)->label = label;
				if (next_label)
				    *next_label = label;
				next_label = &((*scp)->next_label);
			    } else
				(*scp)->label = 0;
			}
			done = READ_LABEL();
			if (next_label)
			    *next_label = done;
			e = alloc_expr(EXPR_SCATTER);
			e->e.scatter = sc;
			for (sc = e->e.scatter; sc; sc = sc->next)
			    if (sc->label) {
				Expr *defallt;

				if (ptr != bc.vector + sc->label)
				    panic("Misplaced default in DECOMPILE!");
				DECOMPILE(bc, ptr,
					  bc.vector + sc->next_label - 1,
					  0, 0);
				defallt = pop_expr();
				HOT1(is_hot, defallt, e);
				if (defallt->kind != EXPR_ASGN
				    || defallt->e.bin.lhs->kind != EXPR_ID
				    || defallt->e.bin.lhs->e.id != sc->id)
				    panic("Wrong variable in DECOMPILE!");
				sc->expr = defallt->e.bin.rhs;
				dealloc_node(defallt->e.bin.lhs);
				dealloc_node(defallt);
				is_hot = (is_hot || ptr == hot_byte);
				if (*ptr++ != OP_POP)
				    panic("Missing default POP in DECOMPILE!");
			    }
			e = alloc_binary(EXPR_ASGN, e, pop_expr());
			push_expr(HOT2(is_hot, e->e.bin.lhs, e->e.bin.rhs, e));
			if (ptr != bc.vector + done)
			    panic("Not at end of scatter in DECOMPILE!");
		    }
		    break;
		case EOP_PUSH_LABEL:
		    e = alloc_var(TYPE_INT);
		    e->e.var.v.num = READ_LABEL();
		    push_expr(HOT_OP(e));
		    break;
		case EOP_CATCH:
		    {
			Expr *label_expr = pop_expr();
			Expr *codes = pop_expr();
			Expr *try_expr, *default_expr = 0;
			Arg_List *a = 0;	/* silence warning */
			int label, done;
			int is_hot = op_hot;

			if (label_expr->kind != EXPR_VAR
			    || label_expr->e.var.type != TYPE_INT)
			    panic("Not a catch label in DECOMPILE!");
			label = label_expr->e.var.v.num;
			dealloc_node(label_expr);
			if (codes->kind == EXPR_LIST)
			    a = codes->e.list;
			else if (codes->kind == EXPR_VAR
				 && codes->e.var.type == TYPE_INT
				 && codes->e.var.v.num == 0)
			    a = 0;
			else
			    panic("Not a codes expression in DECOMPILE!");
			dealloc_node(codes);
			DECOMPILE(bc, ptr, end, 0, 0);
			is_hot = (is_hot || ptr++ == hot_byte);
			if (*ptr++ != EOP_END_CATCH)
			    panic("Missing END_CATCH in DECOMPILE!");
			done = READ_LABEL();
			try_expr = pop_expr();
			if (ptr != bc.vector + label)
			    panic("Misplaced handler in DECOMPILE!");
			is_hot = (is_hot || ptr == hot_byte);
			op = *ptr++;
			if (op == OPTIM_NUM_TO_OPCODE(1)) {
			    /* No default expression */
			    is_hot = (is_hot || ptr == hot_byte);
			    if (*ptr++ != OP_REF)
				panic("Missing REF in DECOMPILE!");
			    default_expr = 0;
			} else if (op == OP_POP) {
			    /* There's a default expression */
			    DECOMPILE(bc, ptr, bc.vector + done, 0, 0);
			    default_expr = pop_expr();
			} else
			    panic("Bad default expression in DECOMPILE!");
			if (ptr != bc.vector + done)
			    panic("CATCH ends in wrong place in DECOMPILE!");
			e = alloc_expr(EXPR_CATCH);
			e->e.catch.try = try_expr;
			e->e.catch.codes = a;
			e->e.catch.except = default_expr;
			push_expr(HOT3(is_hot || (default_expr
					    && default_expr == hot_node),
				       label_expr, codes, try_expr,
				       e));
		    }
		    break;
		case EOP_END_CATCH:
		    /* Early exit; main logic is in CATCH case, above. */
		    return ptr - 2;
		case EOP_TRY_EXCEPT:
		    {
			Expr *label_expr;
			Except_Arm *ex;
			Arg_List *a = 0;	/* silence warning */
			int count = *ptr++, label;
			unsigned done;

			s = HOT_OP(alloc_stmt(STMT_TRY_EXCEPT));
			s->s.catch.excepts = 0;
			while (count--) {
			    label_expr = pop_expr();
			    if (label_expr->kind != EXPR_VAR
				|| label_expr->e.var.type != TYPE_INT)
				panic("Not an except label in DECOMPILE!");
			    label = label_expr->e.var.v.num;
			    dealloc_node(label_expr);
			    e = pop_expr();
			    if (e->kind == EXPR_LIST)
				a = e->e.list;
			    else if (e->kind == EXPR_VAR
				     && e->e.var.type == TYPE_INT
				     && e->e.var.v.num == 0)
				a = 0;
			    else
				panic("Not a codes expression in DECOMPILE!");
			    dealloc_node(e);
			    ex = alloc_except(-1, a, 0);
			    ex->label = label;
			    ex->next = s->s.catch.excepts;
			    HOT2(0, label_expr, e, ex);
			    s->s.catch.excepts = ex;
			}
			DECOMPILE(bc, ptr, end, &(s->s.catch.body), 0);
			HOT_POS(ptr++ == hot_byte, s, ENDBODY);
			if (*ptr++ != EOP_END_EXCEPT)
			    panic("Missing END_EXCEPT in DECOMPILE!");
			done = READ_LABEL();
			for (ex = s->s.catch.excepts; ex; ex = ex->next) {
			    Byte *stop;
			    int jump_hot = 0;

			    if (ex->label != ptr - bc.vector)
				panic("Not at start of handler in DECOMPILE!");
			    op_hot = (ptr == hot_byte);
			    op = *ptr++;
			    if (op == OP_G_PUT) {
				ex->id = READ_ID();
				op = *ptr++;
			    } else if (IS_PUT_n(op)) {
				ex->id = PUT_n_INDEX(op);
				op = *ptr++;
			    }
			    HOT(op_hot || ptr - 1 == hot_byte, ex);
			    if (op != OP_POP)
				panic("Missing POP in DECOMPILE!");
			    if (ex->next)
				stop = bc.vector + ex->next->label - jump_len;
			    else
				stop = bc.vector + done;
			    DECOMPILE(bc, ptr, stop, &(ex->stmt), 0);
			    if (ex->next && READ_JUMP(jump_hot) != done)
				panic("EXCEPT jumps to wrong place in "
				      "DECOMPILE!");
			    HOT_BOTTOM(jump_hot, ex);
			}
			if (ptr - bc.vector != done)
			    panic("EXCEPTS end in wrong place in DECOMPILE!");
			ADD_STMT(s);
		    }
		    break;
		case EOP_END_EXCEPT:
		    /* Early exit; main logic is in TRY_EXCEPT case, above. */
		    return ptr - 2;
		case EOP_TRY_FINALLY:
		    {
			int label = READ_LABEL();

			s = HOT_OP(alloc_stmt(STMT_TRY_FINALLY));
			DECOMPILE(bc, ptr, end, &(s->s.finally.body), 0);
			HOT_POS(ptr++ == hot_byte, s, ENDBODY);
			if (*ptr++ != EOP_END_FINALLY)
			    panic("Missing END_FINALLY in DECOMPILE!");
			if (ptr - bc.vector != label)
			    panic("FINALLY handler in wrong place in "
				  "DECOMPILE!");
			DECOMPILE(bc, ptr, end, &(s->s.finally.handler), 0);
			HOT_BOTTOM(ptr++ == hot_byte, s);
			if (*ptr++ != EOP_CONTINUE)
			    panic("Missing CONTINUE in DECOMPILE!");
			ADD_STMT(s);
		    }
		    break;
		case EOP_END_FINALLY:
		case EOP_CONTINUE:
		    /* Early exit; main logic is in TRY_FINALLY case, above. */
		    return ptr - 2;
		case EOP_WHILE_ID:
		    s = alloc_stmt(STMT_WHILE);
		    s->s.loop.id = READ_ID();
		    goto finish_while;
		case EOP_EXIT:
		case EOP_EXIT_ID:
		    s = alloc_stmt(STMT_BREAK);
		    if (eop == EOP_EXIT_ID)
			s->s.exit = READ_ID();
		    else
			s->s.exit = -1;
		    READ_STACK();
		    if (READ_LABEL() < ptr - bc.vector)
			s->kind = STMT_CONTINUE;
		    ADD_STMT(HOT_OP(s));
		    break;
		default:
		    panic("Unknown extended opcode in DECOMPILE!");
		}
	    }
	    break;
	default:
	    panic("Unknown opcode in DECOMPILE!");
	}
    }

    if (ptr != end)
	panic("Overshot end in DECOMPILE!");

    return ptr;
}

static Stmt *
program_to_tree(Program * prog, int vector, int pc_vector, int pc)
{
    Stmt *result;
    Bytecodes bc;
    int i, sum;

    program = prog;
    bc = (pc_vector == MAIN_VECTOR
	  ? program->main_vector
	  : program->fork_vectors[pc_vector]);

    if (pc < 0)
	hot_byte = 0;
    else if (pc < bc.size)
	hot_byte = bc.vector + pc;
    else
	panic("Illegal PC in FIND_LINE_NUMBER!");

    hot_node = 0;
    hot_position = (pc == bc.size - 1 ? DONE : TOP);

    sum = program->main_vector.max_stack;
    for (i = 0; i < program->fork_vectors_size; i++)
	sum += program->fork_vectors[i].max_stack;
    expr_stack = mymalloc(sum * sizeof(Expr *), M_DECOMPILE);
    top_expr_stack = 0;

    bc = (vector == MAIN_VECTOR
	  ? program->main_vector
	  : program->fork_vectors[vector]);

    begin_code_allocation();
    decompile(bc, bc.vector, bc.vector + bc.size, &result, 0);
    end_code_allocation(0);

    myfree(expr_stack, M_DECOMPILE);

    return result;
}

Stmt *
decompile_program(Program * prog, int vector)
{
    return program_to_tree(prog, vector, MAIN_VECTOR, -1);
}

static int
find_hot_node(Stmt * stmt)
{
    /* Invariants: on entry, lineno is number of first line of STMT
     *                   on exit, if result is true,
     *                            lineno is line number of hot_node/position
     *                      else, lineno is number of first line after STMT
     */

    for (; stmt; stmt = stmt->next) {
	if (stmt == hot_node && hot_position == TOP)
	    return 1;

	switch (stmt->kind) {
	case STMT_COND:
	    {
		Cond_Arm *arm;

		for (arm = stmt->s.cond.arms; arm; arm = arm->next) {
		    if (arm == hot_node && hot_position == TOP)
			return 1;
		    lineno++;	/* advance to arm body */
		    if (find_hot_node(arm->stmt))
			return 1;
		    else if (arm == hot_node && hot_position == BOTTOM) {
			lineno--;	/* Blame last line of arm */
			return 1;
		    }
		}
		if (stmt->s.cond.otherwise) {
		    lineno++;	/* Skip `else' line */
		    if (find_hot_node(stmt->s.cond.otherwise))
			return 1;
		}
	    }
	    break;
	case STMT_LIST:
	    lineno++;		/* Skip `for' line */
	    if (find_hot_node(stmt->s.list.body))
		return 1;
	    break;
	case STMT_RANGE:
	    lineno++;		/* Skip `for' line */
	    if (find_hot_node(stmt->s.range.body))
		return 1;
	    break;
	case STMT_WHILE:
	    lineno++;		/* Skip `while' line */
	    if (find_hot_node(stmt->s.loop.body))
		return 1;
	    break;
	case STMT_FORK:
	    lineno++;		/* Skip `fork' line */
	    if (find_hot_node(stmt->s.fork.body))
		return 1;
	    break;
	case STMT_EXPR:
	case STMT_RETURN:
	case STMT_BREAK:
	case STMT_CONTINUE:
	    /* Nothing more to do */
	    break;
	case STMT_TRY_EXCEPT:
	    {
		Except_Arm *ex;

		lineno++;	/* Skip `try' line */
		if (find_hot_node(stmt->s.catch.body))
		    return 1;
		if (stmt == hot_node && hot_position == ENDBODY) {
		    lineno--;	/* blame it on last line of body */
		    return 1;
		}
		for (ex = stmt->s.catch.excepts; ex; ex = ex->next) {
		    if (ex == hot_node && hot_position == TOP)
			return 1;
		    lineno++;	/* skip `except' line */
		    if (find_hot_node(ex->stmt))
			return 1;
		    if (ex == hot_node && hot_position == BOTTOM) {
			lineno--;	/* blame last line of handler */
			return 1;
		    }
		}
	    }
	    break;
	case STMT_TRY_FINALLY:
	    lineno++;		/* Skip `try' line */
	    if (find_hot_node(stmt->s.finally.body)
		|| (stmt == hot_node && hot_position == ENDBODY))
		return 1;
	    lineno++;		/* Skip `finally' line */
	    if (find_hot_node(stmt->s.finally.handler))
		return 1;
	    break;
	default:
	    panic("Unknown statement kind in FIND_HOT_NODE!");
	}

	if (stmt == hot_node && hot_position == BOTTOM)
	    return 1;

	lineno++;		/* Count this statement */
    }

    return 0;
}

int
find_line_number(Program * prog, int vector, int pc)
{
    Stmt *tree;

    if (prog->cached_lineno_pc == pc && prog->cached_lineno_vec == vector)
	return prog->cached_lineno;

    tree = program_to_tree(prog, MAIN_VECTOR, vector, pc);

    lineno = prog->first_lineno;
    find_hot_node(tree);
    free_stmt(tree);

    if (!hot_node && hot_position != DONE)
	panic("Can't do job in FIND_LINE_NUMBER!");

    prog->cached_lineno_vec = vector;
    prog->cached_lineno_pc = pc;
    prog->cached_lineno = lineno;
    return lineno;
}

char rcsid_decompile[] = "$Id$";

/* 
 * $Log$
 * Revision 1.7  2006/12/06 23:51:31  wrog
 * Fix compiler warnings about unused values
 *
 * Revision 1.6  2002/09/15 23:21:01  xplat
 * GNU indent normalization.
 *
 * Revision 1.5  1999/08/11 08:23:40  bjj
 * Lineno computation could be wrong for forked vectors.
 *
 * Revision 1.4  1998/12/14 13:17:40  nop
 * Merge UNSAFE_OPTS (ref fixups); fix Log tag placement to fit CVS whims
 *
 * Revision 1.3  1997/07/07 03:24:53  nop
 * Merge UNSAFE_OPTS (r5) after extensive testing.
 * 
 * Revision 1.2.2.2  1997/09/09 07:01:16  bjj
 * Change bytecode generation so that x=f(x) calls f() without holding a ref
 * to the value of x in the variable slot.  See the options.h comment for
 * BYTECODE_REDUCE_REF for more details.
 *
 * This checkin also makes x[y]=z (OP_INDEXSET) take advantage of that (that
 * new code is not conditional and still works either way).
 * 
 * Revision 1.2.2.1  1997/06/05 09:00:00  bjj
 * Cache one pc/lineno pair with each Program.  Hopefully most programs that
 * fail multiple times usually do it on the same line!
 *
 * Revision 1.2  1997/03/03 04:18:32  nop
 * GNU Indent normalization
 *
 * Revision 1.1.1.1  1997/03/03 03:44:59  nop
 * LambdaMOO 1.8.0p5
 *
 * Revision 2.6  1996/03/10  01:17:48  pavel
 * Removed a automatic structure initialization.  Release 1.8.0.
 *
 * Revision 2.5  1996/02/08  07:17:28  pavel
 * Renamed TYPE_NUM to TYPE_INT.  Fixed bug in handling of OP_EIF
 * vs. stmt_start.  Added support for exponentiation expression, named WHILE
 * loop and BREAK and CONTINUE statement.  Updated copyright notice for 1996.
 * Release 1.8.0beta1.
 *
 * Revision 2.4  1996/01/16  07:12:42  pavel
 * Add EOP_SCATTER handling.  Release 1.8.0alpha6.
 *
 * Revision 2.3  1995/12/31  03:11:29  pavel
 * Added support for the `$' expression.  Release 1.8.0alpha4.
 *
 * Revision 2.2  1995/12/28  00:37:38  pavel
 * Fixed line number bug in `if' statements.  Fixed memory leak in line-number
 * finder.  Release 1.8.0alpha3.
 *
 * Revision 2.1  1995/12/11  07:58:23  pavel
 * Fixed bug in decompilation of try-except-endtry.  Added distinction between
 * vector and pc_vector in program_to_tree(), to clear up bugs in
 * forked-program accounting.
 *
 * Release 1.8.0alpha2.
 *
 * Revision 2.0  1995/11/30  04:25:59  pavel
 * New baseline version, corresponding to release 1.8.0alpha1.
 *
 * Revision 1.1  1995/11/30  04:25:40  pavel
 * Initial revision
 */