summaryrefslogtreecommitdiff
path: root/ir_reader.cpp
blob: 23981a0f51402952291e7a7b36f0b1a8e25da0cf (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
/*
 * Copyright © 2010 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */
#include <cstdio>
#include <cstdarg>
#include "ir_reader.h"
#include "glsl_parser_extras.h"
#include "glsl_types.h"
#include "s_expression.h"

static void ir_read_error(_mesa_glsl_parse_state *, s_expression *,
			  const char *fmt, ...);
static const glsl_type *read_type(_mesa_glsl_parse_state *, s_expression *);

static void scan_for_prototypes(_mesa_glsl_parse_state *, exec_list *,
			        s_expression *);
static ir_function *read_function(_mesa_glsl_parse_state *, s_list *,
				  bool skip_body);
static void read_function_sig(_mesa_glsl_parse_state *, ir_function *,
			      s_list *, bool skip_body);

static void read_instructions(_mesa_glsl_parse_state *, exec_list *,
			      s_expression *, ir_loop *);
static ir_instruction *read_instruction(_mesa_glsl_parse_state *,
				        s_expression *, ir_loop *);
static ir_variable *read_declaration(_mesa_glsl_parse_state *, s_list *);
static ir_if *read_if(_mesa_glsl_parse_state *, s_list *, ir_loop *);
static ir_loop *read_loop(_mesa_glsl_parse_state *st, s_list *list);
static ir_return *read_return(_mesa_glsl_parse_state *, s_list *);

static ir_rvalue *read_rvalue(_mesa_glsl_parse_state *, s_expression *);
static ir_assignment *read_assignment(_mesa_glsl_parse_state *, s_list *);
static ir_expression *read_expression(_mesa_glsl_parse_state *, s_list *);
static ir_call *read_call(_mesa_glsl_parse_state *, s_list *);
static ir_swizzle *read_swizzle(_mesa_glsl_parse_state *, s_list *);
static ir_constant *read_constant(_mesa_glsl_parse_state *, s_list *);
static ir_texture *read_texture(_mesa_glsl_parse_state *, s_list *);

static ir_dereference *read_dereference(_mesa_glsl_parse_state *,
				        s_expression *);
static ir_dereference *read_var_ref(_mesa_glsl_parse_state *, s_list *);
static ir_dereference *read_array_ref(_mesa_glsl_parse_state *, s_list *);
static ir_dereference *read_record_ref(_mesa_glsl_parse_state *, s_list *);

void
_mesa_glsl_read_ir(_mesa_glsl_parse_state *state, exec_list *instructions,
		   const char *src)
{
   s_expression *expr = s_expression::read_expression(src);
   if (expr == NULL) {
      ir_read_error(state, NULL, "couldn't parse S-Expression.");
      return;
   }
   
   scan_for_prototypes(state, instructions, expr);
   if (state->error)
      return;

   read_instructions(state, instructions, expr, NULL);
}

static void
ir_read_error(_mesa_glsl_parse_state *state, s_expression *expr,
	      const char *fmt, ...)
{
   va_list ap;

   state->error = true;

   printf("error: ");

   va_start(ap, fmt);
   vprintf(fmt, ap);
   va_end(ap);
   printf("\n");

   if (expr != NULL) {
      printf("...in this context:\n   ");
      expr->print();
      printf("\n\n");
   }
}

static const glsl_type *
read_type(_mesa_glsl_parse_state *st, s_expression *expr)
{
   s_list *list = SX_AS_LIST(expr);
   if (list != NULL) {
      s_symbol *type_sym = SX_AS_SYMBOL(list->subexpressions.get_head());
      if (type_sym == NULL) {
	 ir_read_error(st, expr, "expected type (array ...) or (struct ...)");
	 return NULL;
      }
      if (strcmp(type_sym->value(), "array") == 0) {
	 if (list->length() != 3) {
	    ir_read_error(st, expr, "expected type (array <type> <int>)");
	    return NULL;
	 }

	 // Read base type
	 s_expression *base_expr = (s_expression*) type_sym->next;
	 const glsl_type *base_type = read_type(st, base_expr);
	 if (base_type == NULL) {
	    ir_read_error(st, NULL, "when reading base type of array");
	    return NULL;
	 }

	 // Read array size
	 s_int *size = SX_AS_INT(base_expr->next);
	 if (size == NULL) {
	    ir_read_error(st, expr, "found non-integer array size");
	    return NULL;
	 }

	 return glsl_type::get_array_instance(base_type, size->value());
      } else if (strcmp(type_sym->value(), "struct") == 0) {
	 assert(false); // FINISHME
      } else {
	 ir_read_error(st, expr, "expected (array ...) or (struct ...); "
				 "found (%s ...)", type_sym->value());
	 return NULL;
      }
   }
   
   s_symbol *type_sym = SX_AS_SYMBOL(expr);
   if (type_sym == NULL) {
      ir_read_error(st, expr, "expected <type> (symbol or list)");
      return NULL;
   }

   const glsl_type *type = st->symbols->get_type(type_sym->value());
   if (type == NULL)
      ir_read_error(st, expr, "invalid type: %s", type_sym->value());

   return type;
}


static void
scan_for_prototypes(_mesa_glsl_parse_state *st, exec_list *instructions,
		    s_expression *expr)
{
   s_list *list = SX_AS_LIST(expr);
   if (list == NULL) {
      ir_read_error(st, expr, "Expected (<instruction> ...); found an atom.");
      return;
   }

   foreach_iter(exec_list_iterator, it, list->subexpressions) {
      s_list *sub = SX_AS_LIST(it.get());
      if (sub == NULL)
	 continue; // not a (function ...); ignore it.

      s_symbol *tag = SX_AS_SYMBOL(sub->subexpressions.get_head());
      if (tag == NULL || strcmp(tag->value(), "function") != 0)
	 continue; // not a (function ...); ignore it.

      ir_function *f = read_function(st, sub, true);
      if (f == NULL)
	 return;
      instructions->push_tail(f);
   }
}

static ir_function *
read_function(_mesa_glsl_parse_state *st, s_list *list, bool skip_body)
{
   if (list->length() < 3) {
      ir_read_error(st, list, "Expected (function <name> (signature ...) ...)");
      return NULL;
   }

   s_symbol *name = SX_AS_SYMBOL(list->subexpressions.head->next);
   if (name == NULL) {
      ir_read_error(st, list, "Expected (function <name> ...)");
      return NULL;
   }

   ir_function *f = st->symbols->get_function(name->value());
   if (f == NULL) {
      f = new ir_function(name->value());
      bool added = st->symbols->add_function(name->value(), f);
      assert(added);
   }

   exec_list_iterator it = list->subexpressions.iterator();
   it.next(); // skip "function" tag
   it.next(); // skip function name
   for (/* nothing */; it.has_next(); it.next()) {
      s_list *siglist = SX_AS_LIST(it.get());
      if (siglist == NULL) {
	 ir_read_error(st, list, "Expected (function (signature ...) ...)");
	 return NULL;
      }

      s_symbol *tag = SX_AS_SYMBOL(siglist->subexpressions.get_head());
      if (tag == NULL || strcmp(tag->value(), "signature") != 0) {
	 ir_read_error(st, siglist, "Expected (signature ...)");
	 return NULL;
      }

      read_function_sig(st, f, siglist, skip_body);
   }
   return f;
}

static void
read_function_sig(_mesa_glsl_parse_state *st, ir_function *f, s_list *list,
		  bool skip_body)
{
   if (list->length() != 4) {
      ir_read_error(st, list, "Expected (signature <type> (parameters ...) "
			      "(<instruction> ...))");
      return;
   }

   s_expression *type_expr = (s_expression*) list->subexpressions.head->next;
   const glsl_type *return_type = read_type(st, type_expr);
   if (return_type == NULL)
      return;

   s_list *paramlist = SX_AS_LIST(type_expr->next);
   s_list *body_list = SX_AS_LIST(paramlist->next);
   if (paramlist == NULL || body_list == NULL) {
      ir_read_error(st, list, "Expected (signature <type> (parameters ...) "
			      "(<instruction> ...))");
      return;
   }
   s_symbol *paramtag = SX_AS_SYMBOL(paramlist->subexpressions.get_head());
   if (paramtag == NULL || strcmp(paramtag->value(), "parameters") != 0) {
      ir_read_error(st, paramlist, "Expected (parameters ...)");
      return;
   }

   // Read the parameters list into a temporary place.
   exec_list hir_parameters;
   st->symbols->push_scope();

   exec_list_iterator it = paramlist->subexpressions.iterator();
   for (it.next() /* skip "parameters" */; it.has_next(); it.next()) {
      s_list *decl = SX_AS_LIST(it.get());
      ir_variable *var = read_declaration(st, decl);
      if (var == NULL)
	 return;

      hir_parameters.push_tail(var);
   }

   ir_function_signature *sig = f->exact_matching_signature(&hir_parameters);
   if (sig != NULL) {
      const char *badvar = sig->qualifiers_match(&hir_parameters);
      if (badvar != NULL) {
	 ir_read_error(st, list, "function `%s' parameter `%s' qualifiers "
		       "don't match prototype", f->name, badvar);
	 return;
      }

      if (sig->return_type != return_type) {
	 ir_read_error(st, list, "function `%s' return type doesn't "
		       "match prototype", f->name);
	 return;
      }
   } else {
      sig = new ir_function_signature(return_type);
      f->add_signature(sig);
   }

   sig->replace_parameters(&hir_parameters);

   if (!skip_body) {
      if (sig->is_defined) {
	 ir_read_error(st, list, "function %s redefined", f->name);
	 return;
      }
      read_instructions(st, &sig->body, body_list, NULL);
      sig->is_defined = true;
   }

   st->symbols->pop_scope();
}

static void
read_instructions(_mesa_glsl_parse_state *st, exec_list *instructions,
		  s_expression *expr, ir_loop *loop_ctx)
{
   // Read in a list of instructions
   s_list *list = SX_AS_LIST(expr);
   if (list == NULL) {
      ir_read_error(st, expr, "Expected (<instruction> ...); found an atom.");
      return;
   }

   foreach_iter(exec_list_iterator, it, list->subexpressions) {
      s_expression *sub = (s_expression*) it.get();
      ir_instruction *ir = read_instruction(st, sub, loop_ctx);
      if (ir == NULL) {
	 ir_read_error(st, sub, "Invalid instruction.\n");
	 return;
      }
      instructions->push_tail(ir);
   }
}


static ir_instruction *
read_instruction(_mesa_glsl_parse_state *st, s_expression *expr,
	         ir_loop *loop_ctx)
{
   s_symbol *symbol = SX_AS_SYMBOL(expr);
   if (symbol != NULL) {
      if (strcmp(symbol->value(), "break") == 0 && loop_ctx != NULL)
	 return new ir_loop_jump(loop_ctx, ir_loop_jump::jump_break);
      if (strcmp(symbol->value(), "continue") == 0 && loop_ctx != NULL)
	 return new ir_loop_jump(loop_ctx, ir_loop_jump::jump_continue);
   }

   s_list *list = SX_AS_LIST(expr);
   if (list == NULL || list->subexpressions.is_empty())
      return NULL;

   s_symbol *tag = SX_AS_SYMBOL(list->subexpressions.get_head());
   if (tag == NULL) {
      ir_read_error(st, expr, "expected instruction tag");
      return NULL;
   }

   ir_instruction *inst = NULL;
   if (strcmp(tag->value(), "declare") == 0) {
      inst = read_declaration(st, list);
   } else if (strcmp(tag->value(), "if") == 0) {
      inst = read_if(st, list, loop_ctx);
   } else if (strcmp(tag->value(), "loop") == 0) {
      inst = read_loop(st, list);
   } else if (strcmp(tag->value(), "return") == 0) {
      inst = read_return(st, list);
   } else if (strcmp(tag->value(), "function") == 0) {
      inst = read_function(st, list, false);
   } else {
      inst = read_rvalue(st, list);
      if (inst == NULL)
	 ir_read_error(st, NULL, "when reading instruction");
   }
   return inst;
}


static ir_variable *
read_declaration(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 4) {
      ir_read_error(st, list, "expected (declare (<qualifiers>) <type> "
			      "<name>)");
      return NULL;
   }

   s_list *quals = SX_AS_LIST(list->subexpressions.head->next);
   if (quals == NULL) {
      ir_read_error(st, list, "expected a list of variable qualifiers");
      return NULL;
   }

   s_expression *type_expr = (s_expression*) quals->next;
   const glsl_type *type = read_type(st, type_expr);
   if (type == NULL)
      return NULL;

   s_symbol *var_name = SX_AS_SYMBOL(type_expr->next);
   if (var_name == NULL) {
      ir_read_error(st, list, "expected variable name, found non-symbol");
      return NULL;
   }

   ir_variable *var = new ir_variable(type, var_name->value());

   foreach_iter(exec_list_iterator, it, quals->subexpressions) {
      s_symbol *qualifier = SX_AS_SYMBOL(it.get());
      if (qualifier == NULL) {
	 ir_read_error(st, list, "qualifier list must contain only symbols");
	 delete var;
	 return NULL;
      }

      // FINISHME: Check for duplicate/conflicting qualifiers.
      if (strcmp(qualifier->value(), "centroid") == 0) {
	 var->centroid = 1;
      } else if (strcmp(qualifier->value(), "invariant") == 0) {
	 var->invariant = 1;
      } else if (strcmp(qualifier->value(), "uniform") == 0) {
	 var->mode = ir_var_uniform;
      } else if (strcmp(qualifier->value(), "auto") == 0) {
	 var->mode = ir_var_auto;
      } else if (strcmp(qualifier->value(), "in") == 0) {
	 var->mode = ir_var_in;
      } else if (strcmp(qualifier->value(), "out") == 0) {
	 var->mode = ir_var_out;
      } else if (strcmp(qualifier->value(), "inout") == 0) {
	 var->mode = ir_var_inout;
      } else if (strcmp(qualifier->value(), "smooth") == 0) {
	 var->interpolation = ir_var_smooth;
      } else if (strcmp(qualifier->value(), "flat") == 0) {
	 var->interpolation = ir_var_flat;
      } else if (strcmp(qualifier->value(), "noperspective") == 0) {
	 var->interpolation = ir_var_noperspective;
      } else {
	 ir_read_error(st, list, "unknown qualifier: %s", qualifier->value());
	 delete var;
	 return NULL;
      }
   }

   // Add the variable to the symbol table
   st->symbols->add_variable(var_name->value(), var);

   return var;
}


static ir_if *
read_if(_mesa_glsl_parse_state *st, s_list *list, ir_loop *loop_ctx)
{
   if (list->length() != 4) {
      ir_read_error(st, list, "expected (if <condition> (<then> ...) "
                          "(<else> ...))");
      return NULL;
   }

   s_expression *cond_expr = (s_expression*) list->subexpressions.head->next;
   ir_rvalue *condition = read_rvalue(st, cond_expr);
   if (condition == NULL) {
      ir_read_error(st, NULL, "when reading condition of (if ...)");
      return NULL;
   }

   s_expression *then_expr = (s_expression*) cond_expr->next;
   s_expression *else_expr = (s_expression*) then_expr->next;

   ir_if *iff = new ir_if(condition);

   read_instructions(st, &iff->then_instructions, then_expr, loop_ctx);
   read_instructions(st, &iff->else_instructions, else_expr, loop_ctx);
   if (st->error) {
      delete iff;
      iff = NULL;
   }
   return iff;
}


static ir_loop *
read_loop(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 6) {
      ir_read_error(st, list, "expected (loop <counter> <from> <to> "
			      "<increment> <body>)");
      return NULL;
   }

   s_expression *count_expr = (s_expression*) list->subexpressions.head->next;
   s_expression *from_expr  = (s_expression*) count_expr->next;
   s_expression *to_expr    = (s_expression*) from_expr->next;
   s_expression *inc_expr   = (s_expression*) to_expr->next;
   s_expression *body_expr  = (s_expression*) inc_expr->next;

   // FINISHME: actually read the count/from/to fields.

   ir_loop *loop = new ir_loop;
   read_instructions(st, &loop->body_instructions, body_expr, loop);
   if (st->error) {
      delete loop;
      loop = NULL;
   }
   return loop;
}


static ir_return *
read_return(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 2) {
      ir_read_error(st, list, "expected (return <rvalue>)");
      return NULL;
   }

   s_expression *expr = (s_expression*) list->subexpressions.head->next;

   ir_rvalue *retval = read_rvalue(st, expr);
   if (retval == NULL) {
      ir_read_error(st, NULL, "when reading return value");
      return NULL;
   }

   return new ir_return(retval);
}


static ir_rvalue *
read_rvalue(_mesa_glsl_parse_state *st, s_expression *expr)
{
   s_list *list = SX_AS_LIST(expr);
   if (list == NULL || list->subexpressions.is_empty())
      return NULL;

   s_symbol *tag = SX_AS_SYMBOL(list->subexpressions.get_head());
   if (tag == NULL) {
      ir_read_error(st, expr, "expected rvalue tag");
      return NULL;
   }

   ir_rvalue *rvalue = read_dereference(st, list);
   if (rvalue != NULL || st->error)
      return rvalue;
   else if (strcmp(tag->value(), "swiz") == 0) {
      rvalue = read_swizzle(st, list);
   } else if (strcmp(tag->value(), "assign") == 0) {
      rvalue = read_assignment(st, list);
   } else if (strcmp(tag->value(), "expression") == 0) {
      rvalue = read_expression(st, list);
   } else if (strcmp(tag->value(), "call") == 0) {
      rvalue = read_call(st, list);
   } else if (strcmp(tag->value(), "constant") == 0) {
      rvalue = read_constant(st, list);
   } else {
      rvalue = read_texture(st, list);
      if (rvalue == NULL && !st->error)
	 ir_read_error(st, expr, "unrecognized rvalue tag: %s", tag->value());
   }

   return rvalue;
}

static ir_assignment *
read_assignment(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 4) {
      ir_read_error(st, list, "expected (assign <condition> <lhs> <rhs>)");
      return NULL;
   }

   s_expression *cond_expr = (s_expression*) list->subexpressions.head->next;
   s_expression *lhs_expr  = (s_expression*) cond_expr->next;
   s_expression *rhs_expr  = (s_expression*) lhs_expr->next;

   // FINISHME: Deal with "true" condition
   ir_rvalue *condition = read_rvalue(st, cond_expr);
   if (condition == NULL) {
      ir_read_error(st, NULL, "when reading condition of assignment");
      return NULL;
   }

   ir_rvalue *lhs = read_rvalue(st, lhs_expr);
   if (lhs == NULL) {
      ir_read_error(st, NULL, "when reading left-hand side of assignment");
      return NULL;
   }

   ir_rvalue *rhs = read_rvalue(st, rhs_expr);
   if (rhs == NULL) {
      ir_read_error(st, NULL, "when reading right-hand side of assignment");
      return NULL;
   }

   return new ir_assignment(lhs, rhs, condition);
}

static ir_call *
read_call(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 3) {
      ir_read_error(st, list, "expected (call <name> (<param> ...))");
      return NULL;
   }

   s_symbol *name = SX_AS_SYMBOL(list->subexpressions.head->next);
   s_list *params = SX_AS_LIST(name->next);
   if (name == NULL || params == NULL) {
      ir_read_error(st, list, "expected (call <name> (<param> ...))");
      return NULL;
   }

   exec_list parameters;

   foreach_iter(exec_list_iterator, it, params->subexpressions) {
      s_expression *expr = (s_expression*) it.get();
      ir_rvalue *param = read_rvalue(st, expr);
      if (param == NULL) {
	 ir_read_error(st, list, "when reading parameter to function call");
	 return NULL;
      }
      parameters.push_tail(param);
   }

   ir_function *f = st->symbols->get_function(name->value());
   if (f == NULL) {
      ir_read_error(st, list, "found call to undefined function %s",
		    name->value());
      return NULL;
   }

   const ir_function_signature *callee = f->matching_signature(&parameters);
   if (callee == NULL) {
      ir_read_error(st, list, "couldn't find matching signature for function "
                    "%s", name->value());
      return NULL;
   }

   return new ir_call(callee, &parameters);
}

static ir_expression *
read_expression(_mesa_glsl_parse_state *st, s_list *list)
{
   const unsigned list_length = list->length();
   if (list_length < 4) {
      ir_read_error(st, list, "expected (expression <type> <operator> "
			      "<operand> [<operand>])");
      return NULL;
   }

   s_expression *type_expr = (s_expression*) list->subexpressions.head->next;
   const glsl_type *type = read_type(st, type_expr);
   if (type == NULL)
      return NULL;

   /* Read the operator */
   s_symbol *op_sym = SX_AS_SYMBOL(type_expr->next);
   if (op_sym == NULL) {
      ir_read_error(st, list, "expected operator, found non-symbol");
      return NULL;
   }

   ir_expression_operation op = ir_expression::get_operator(op_sym->value());
   if (op == (ir_expression_operation) -1) {
      ir_read_error(st, list, "invalid operator: %s", op_sym->value());
      return NULL;
   }
    
   /* Now that we know the operator, check for the right number of operands */ 
   if (ir_expression::get_num_operands(op) == 2) {
      if (list_length != 5) {
	 ir_read_error(st, list, "expected (expression <type> %s <operand> "
				 " <operand>)", op_sym->value());
	 return NULL;
      }
   } else {
      if (list_length != 4) {
	 ir_read_error(st, list, "expected (expression <type> %s <operand>)",
		       op_sym->value());
	 return NULL;
      }
   }

   s_expression *exp1 = (s_expression*) (op_sym->next);
   ir_rvalue *arg1 = read_rvalue(st, exp1);
   if (arg1 == NULL) {
      ir_read_error(st, NULL, "when reading first operand of %s",
		    op_sym->value());
      return NULL;
   }

   ir_rvalue *arg2 = NULL;
   if (ir_expression::get_num_operands(op) == 2) {
      s_expression *exp2 = (s_expression*) (exp1->next);
      arg2 = read_rvalue(st, exp2);
      if (arg2 == NULL) {
	 ir_read_error(st, NULL, "when reading second operand of %s",
		       op_sym->value());
	 return NULL;
      }
   }

   return new ir_expression(op, type, arg1, arg2);
}

static ir_swizzle *
read_swizzle(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 3) {
      ir_read_error(st, list, "expected (swiz <swizzle> <rvalue>)");
      return NULL;
   }

   s_symbol *swiz = SX_AS_SYMBOL(list->subexpressions.head->next);
   if (swiz == NULL) {
      ir_read_error(st, list, "expected a valid swizzle; found non-symbol");
      return NULL;
   }

   if (strlen(swiz->value()) > 4) {
      ir_read_error(st, list, "expected a valid swizzle; found %s",
		    swiz->value());
      return NULL;
   }

   s_expression *sub = (s_expression*) swiz->next;
   if (sub == NULL) {
      ir_read_error(st, list, "expected rvalue: (swizzle %s <rvalue>)",
		    swiz->value());
      return NULL;
   }

   ir_rvalue *rvalue = read_rvalue(st, sub);
   if (rvalue == NULL)
      return NULL;

   ir_swizzle *ir = ir_swizzle::create(rvalue, swiz->value(),
				       rvalue->type->vector_elements);
   if (ir == NULL)
      ir_read_error(st, list, "invalid swizzle");

   return ir;
}

static ir_constant *
read_constant(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 3) {
      ir_read_error(st, list, "expected (constant <type> (<num> ... <num>))");
      return NULL;
   }

   s_expression *type_expr = (s_expression*) list->subexpressions.head->next;
   const glsl_type *type = read_type(st, type_expr);
   if (type == NULL)
      return NULL;

   s_list *values = SX_AS_LIST(type_expr->next);
   if (values == NULL) {
      ir_read_error(st, list, "expected (constant <type> (<num> ... <num>))");
      return NULL;
   }

   const glsl_type *const base_type = type->get_base_type();

   ir_constant_data data;

   // Read in list of values (at most 16).
   int k = 0;
   foreach_iter(exec_list_iterator, it, values->subexpressions) {
      if (k >= 16) {
	 ir_read_error(st, values, "expected at most 16 numbers");
	 return NULL;
      }

      s_expression *expr = (s_expression*) it.get();

      if (base_type->base_type == GLSL_TYPE_FLOAT) {
	 s_number *value = SX_AS_NUMBER(expr);
	 if (value == NULL) {
	    ir_read_error(st, values, "expected numbers");
	    return NULL;
	 }
	 data.f[k] = value->fvalue();
      } else {
	 s_int *value = SX_AS_INT(expr);
	 if (value == NULL) {
	    ir_read_error(st, values, "expected integers");
	    return NULL;
	 }

	 switch (base_type->base_type) {
	 case GLSL_TYPE_UINT: {
	    data.u[k] = value->value();
	    break;
	 }
	 case GLSL_TYPE_INT: {
	    data.i[k] = value->value();
	    break;
	 }
	 case GLSL_TYPE_BOOL: {
	    data.b[k] = value->value();
	    break;
	 }
	 default:
	    ir_read_error(st, values, "unsupported constant type");
	    return NULL;
	 }
      }
      ++k;
   }

   return new ir_constant(type, &data);
}

static ir_dereference *
read_dereference(_mesa_glsl_parse_state *st, s_expression *expr)
{
   s_list *list = SX_AS_LIST(expr);
   if (list == NULL || list->subexpressions.is_empty())
      return NULL;

   s_symbol *tag = SX_AS_SYMBOL(list->subexpressions.head);
   assert(tag != NULL);

   if (strcmp(tag->value(), "var_ref") == 0)
      return read_var_ref(st, list);
   if (strcmp(tag->value(), "array_ref") == 0)
      return read_array_ref(st, list);
   if (strcmp(tag->value(), "record_ref") == 0)
      return read_record_ref(st, list);
   return NULL;
}

static ir_dereference *
read_var_ref(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 2) {
      ir_read_error(st, list, "expected (var_ref <variable name>)");
      return NULL;
   }
   s_symbol *var_name = SX_AS_SYMBOL(list->subexpressions.head->next);
   if (var_name == NULL) {
      ir_read_error(st, list, "expected (var_ref <variable name>)");
      return NULL;
   }

   ir_variable *var = st->symbols->get_variable(var_name->value());
   if (var == NULL) {
      ir_read_error(st, list, "undeclared variable: %s", var_name->value());
      return NULL;
   }

   return new ir_dereference_variable(var);
}

static ir_dereference *
read_array_ref(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 3) {
      ir_read_error(st, list, "expected (array_ref <rvalue> <index>)");
      return NULL;
   }

   s_expression *subj_expr = (s_expression*) list->subexpressions.head->next;
   ir_rvalue *subject = read_rvalue(st, subj_expr);
   if (subject == NULL) {
      ir_read_error(st, NULL, "when reading the subject of an array_ref");
      return NULL;
   }

   s_expression *idx_expr = (s_expression*) subj_expr->next;
   ir_rvalue *idx = read_rvalue(st, idx_expr);
   return new ir_dereference_array(subject, idx);
}

static ir_dereference *
read_record_ref(_mesa_glsl_parse_state *st, s_list *list)
{
   if (list->length() != 3) {
      ir_read_error(st, list, "expected (record_ref <rvalue> <field>)");
      return NULL;
   }

   s_expression *subj_expr = (s_expression*) list->subexpressions.head->next;
   ir_rvalue *subject = read_rvalue(st, subj_expr);
   if (subject == NULL) {
      ir_read_error(st, NULL, "when reading the subject of a record_ref");
      return NULL;
   }

   s_symbol *field = SX_AS_SYMBOL(subj_expr->next);
   if (field == NULL) {
      ir_read_error(st, list, "expected (record_ref ... <field name>)");
      return NULL;
   }
   return new ir_dereference_record(subject, field->value());
}

static bool
valid_texture_list_length(ir_texture_opcode op, s_list *list)
{
   unsigned required_length = 7;
   if (op == ir_txf)
      required_length = 5;
   else if (op == ir_tex)
      required_length = 6;

   return list->length() == required_length;
}

static ir_texture *
read_texture(_mesa_glsl_parse_state *st, s_list *list)
{
   s_symbol *tag = SX_AS_SYMBOL(list->subexpressions.head);
   assert(tag != NULL);

   ir_texture_opcode op = ir_texture::get_opcode(tag->value());
   if (op == (ir_texture_opcode) -1)
      return NULL;

   if (!valid_texture_list_length(op, list)) {
      ir_read_error(st, NULL, "invalid list size in (%s ...)", tag->value());
      return NULL;
   }

   ir_texture *tex = new ir_texture(op);

   // Read sampler (must be a deref)
   s_expression *sampler_expr = (s_expression *) tag->next;
   ir_dereference *sampler = read_dereference(st, sampler_expr);
   if (sampler == NULL) {
      ir_read_error(st, NULL, "when reading sampler in (%s ...)", tag->value());
      return NULL;
   }
   tex->set_sampler(sampler);

   // Read coordinate (any rvalue)
   s_expression *coordinate_expr = (s_expression *) sampler_expr->next;
   tex->coordinate = read_rvalue(st, coordinate_expr);
   if (tex->coordinate == NULL) {
      ir_read_error(st, NULL, "when reading coordinate in (%s ...)",
		    tag->value());
      return NULL;
   }

   // Read texel offset, i.e. (0 0 0)
   s_list *offset_list = SX_AS_LIST(coordinate_expr->next);
   if (offset_list == NULL || offset_list->length() != 3) {
      ir_read_error(st, offset_list, "expected (<int> <int> <int>)");
      return NULL;
   }
   s_int *offset_x = SX_AS_INT(offset_list->subexpressions.head);
   s_int *offset_y = SX_AS_INT(offset_x->next);
   s_int *offset_z = SX_AS_INT(offset_y->next);
   if (offset_x == NULL || offset_y == NULL || offset_z == NULL) {
      ir_read_error(st, offset_list, "expected (<int> <int> <int>)");
      return NULL;
   }
   tex->offsets[0] = offset_x->value();
   tex->offsets[1] = offset_y->value();
   tex->offsets[2] = offset_z->value();

   if (op == ir_txf) {
      s_expression *lod_expr = (s_expression *) offset_list->next;
      tex->lod_info.lod = read_rvalue(st, lod_expr);
      if (tex->lod_info.lod == NULL) {
	 ir_read_error(st, NULL, "when reading LOD in (txf ...)");
	 return NULL;
      }
   } else {
      s_expression *proj_expr = (s_expression *) offset_list->next;
      s_int *proj_as_int = SX_AS_INT(proj_expr);
      if (proj_as_int && proj_as_int->value() == 1) {
	 tex->projector = NULL;
      } else {
	 tex->projector = read_rvalue(st, proj_expr);
	 if (tex->projector == NULL) {
	    ir_read_error(st, NULL, "when reading projective divide in (%s ..)",
	                  tag->value());
	    return NULL;
	 }
      }

      s_list *shadow_list = SX_AS_LIST(proj_expr->next);
      if (shadow_list == NULL) {
	 ir_read_error(st, NULL, "shadow comparitor must be a list");
	 return NULL;
      }
      if (shadow_list->subexpressions.is_empty()) {
	 tex->shadow_comparitor= NULL;
      } else {
	 tex->shadow_comparitor = read_rvalue(st, shadow_list);
	 if (tex->shadow_comparitor == NULL) {
	    ir_read_error(st, NULL, "when reading shadow comparitor in (%s ..)",
			  tag->value());
	    return NULL;
	 }
      }
      s_expression *lod_expr = (s_expression *) shadow_list->next;

      switch (op) {
      case ir_txb:
	 tex->lod_info.bias = read_rvalue(st, lod_expr);
	 if (tex->lod_info.bias == NULL) {
	    ir_read_error(st, NULL, "when reading LOD bias in (txb ...)");
	    return NULL;
	 }
	 break;
      case ir_txl:
	 tex->lod_info.lod = read_rvalue(st, lod_expr);
	 if (tex->lod_info.lod == NULL) {
	    ir_read_error(st, NULL, "when reading LOD in (txl ...)");
	    return NULL;
	 }
	 break;
      case ir_txd: {
	 s_list *lod_list = SX_AS_LIST(lod_expr);
	 if (lod_list->length() != 2) {
	    ir_read_error(st, lod_expr, "expected (dPdx dPdy) in (txd ...)");
	    return NULL;
	 }
	 s_expression *dx_expr = (s_expression *) lod_list->subexpressions.head;
	 s_expression *dy_expr = (s_expression *) dx_expr->next;

	 tex->lod_info.grad.dPdx = read_rvalue(st, dx_expr);
	 if (tex->lod_info.grad.dPdx == NULL) {
	    ir_read_error(st, NULL, "when reading dPdx in (txd ...)");
	    return NULL;
	 }
	 tex->lod_info.grad.dPdy = read_rvalue(st, dy_expr);
	 if (tex->lod_info.grad.dPdy == NULL) {
	    ir_read_error(st, NULL, "when reading dPdy in (txd ...)");
	    return NULL;
	 }
	 break;
      }
      default:
	 // tex doesn't have any extra parameters and txf was handled earlier.
	 break;
      };
   }
   return tex;
}