summaryrefslogtreecommitdiff
path: root/gcc/tree-ssa-reassoc.c
blob: 19e10398168b7e2910c5fa35cca220b09951ac5b (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
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
/* Reassociation for trees.
   Copyright (C) 2005, 2007 Free Software Foundation, Inc.
   Contributed by Daniel Berlin <dan@dberlin.org>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "errors.h"
#include "ggc.h"
#include "tree.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "tree-inline.h"
#include "tree-flow.h"
#include "tree-gimple.h"
#include "tree-dump.h"
#include "timevar.h"
#include "tree-iterator.h"
#include "tree-pass.h"
#include "alloc-pool.h"
#include "vec.h"
#include "langhooks.h"
#include "pointer-set.h"
#include "cfgloop.h"
#include "flags.h"

/*  This is a simple global reassociation pass.  It is, in part, based
    on the LLVM pass of the same name (They do some things more/less
    than we do, in different orders, etc).

    It consists of five steps:

    1. Breaking up subtract operations into addition + negate, where
    it would promote the reassociation of adds.

    2. Left linearization of the expression trees, so that (A+B)+(C+D)
    becomes (((A+B)+C)+D), which is easier for us to rewrite later.
    During linearization, we place the operands of the binary
    expressions into a vector of operand_entry_t

    3. Optimization of the operand lists, eliminating things like a +
    -a, a & a, etc.

    4. Rewrite the expression trees we linearized and optimized so
    they are in proper rank order.

    5. Repropagate negates, as nothing else will clean it up ATM.

    A bit of theory on #4, since nobody seems to write anything down
    about why it makes sense to do it the way they do it:

    We could do this much nicer theoretically, but don't (for reasons
    explained after how to do it theoretically nice :P).

    In order to promote the most redundancy elimination, you want
    binary expressions whose operands are the same rank (or
    preferably, the same value) exposed to the redundancy eliminator,
    for possible elimination.

    So the way to do this if we really cared, is to build the new op
    tree from the leaves to the roots, merging as you go, and putting the
    new op on the end of the worklist, until you are left with one
    thing on the worklist.

    IE if you have to rewrite the following set of operands (listed with
    rank in parentheses), with opcode PLUS_EXPR:

    a (1),  b (1),  c (1),  d (2), e (2)


    We start with our merge worklist empty, and the ops list with all of
    those on it.

    You want to first merge all leaves of the same rank, as much as
    possible.

    So first build a binary op of

    mergetmp = a + b, and put "mergetmp" on the merge worklist.

    Because there is no three operand form of PLUS_EXPR, c is not going to
    be exposed to redundancy elimination as a rank 1 operand.

    So you might as well throw it on the merge worklist (you could also
    consider it to now be a rank two operand, and merge it with d and e,
    but in this case, you then have evicted e from a binary op. So at
    least in this situation, you can't win.)

    Then build a binary op of d + e
    mergetmp2 = d + e

    and put mergetmp2 on the merge worklist.
    
    so merge worklist = {mergetmp, c, mergetmp2}
    
    Continue building binary ops of these operations until you have only
    one operation left on the worklist.
    
    So we have
    
    build binary op
    mergetmp3 = mergetmp + c
    
    worklist = {mergetmp2, mergetmp3}
    
    mergetmp4 = mergetmp2 + mergetmp3
    
    worklist = {mergetmp4}
    
    because we have one operation left, we can now just set the original
    statement equal to the result of that operation.
    
    This will at least expose a + b  and d + e to redundancy elimination
    as binary operations.
    
    For extra points, you can reuse the old statements to build the
    mergetmps, since you shouldn't run out.

    So why don't we do this?
    
    Because it's expensive, and rarely will help.  Most trees we are
    reassociating have 3 or less ops.  If they have 2 ops, they already
    will be written into a nice single binary op.  If you have 3 ops, a
    single simple check suffices to tell you whether the first two are of the
    same rank.  If so, you know to order it

    mergetmp = op1 + op2
    newstmt = mergetmp + op3
    
    instead of
    mergetmp = op2 + op3
    newstmt = mergetmp + op1
    
    If all three are of the same rank, you can't expose them all in a
    single binary operator anyway, so the above is *still* the best you
    can do.
    
    Thus, this is what we do.  When we have three ops left, we check to see
    what order to put them in, and call it a day.  As a nod to vector sum
    reduction, we check if any of ops are a really a phi node that is a
    destructive update for the associating op, and keep the destructive
    update together for vector sum reduction recognition.  */


/* Statistics */
static struct
{
  int linearized;
  int constants_eliminated;
  int ops_eliminated;
  int rewritten;
} reassociate_stats;

/* Operator, rank pair.  */
typedef struct operand_entry
{
  unsigned int rank;
  tree op;
} *operand_entry_t;

static alloc_pool operand_entry_pool;


/* Starting rank number for a given basic block, so that we can rank
   operations using unmovable instructions in that BB based on the bb
   depth.  */
static long *bb_rank;

/* Operand->rank hashtable.  */
static struct pointer_map_t *operand_rank;


/* Look up the operand rank structure for expression E.  */

static inline long
find_operand_rank (tree e)
{
  void **slot = pointer_map_contains (operand_rank, e);
  return slot ? (long) *slot : -1;
}

/* Insert {E,RANK} into the operand rank hashtable.  */

static inline void
insert_operand_rank (tree e, long rank)
{
  void **slot;
  gcc_assert (rank > 0);
  slot = pointer_map_insert (operand_rank, e);
  gcc_assert (!*slot);
  *slot = (void *) rank;
}

/* Given an expression E, return the rank of the expression.  */

static long
get_rank (tree e)
{
  /* Constants have rank 0.  */
  if (is_gimple_min_invariant (e))
    return 0;

  /* SSA_NAME's have the rank of the expression they are the result
     of.
     For globals and uninitialized values, the rank is 0.
     For function arguments, use the pre-setup rank.
     For PHI nodes, stores, asm statements, etc, we use the rank of
     the BB.
     For simple operations, the rank is the maximum rank of any of
     its operands, or the bb_rank, whichever is less.
     I make no claims that this is optimal, however, it gives good
     results.  */

  if (TREE_CODE (e) == SSA_NAME)
    {
      tree stmt;
      tree rhs;
      long rank, maxrank;
      int i;
      int n;

      if (TREE_CODE (SSA_NAME_VAR (e)) == PARM_DECL
	  && SSA_NAME_IS_DEFAULT_DEF (e))
	return find_operand_rank (e);

      stmt = SSA_NAME_DEF_STMT (e);
      if (bb_for_stmt (stmt) == NULL)
	return 0;

      if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
	  || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS))
	return bb_rank[bb_for_stmt (stmt)->index];

      /* If we already have a rank for this expression, use that.  */
      rank = find_operand_rank (e);
      if (rank != -1)
	return rank;

      /* Otherwise, find the maximum rank for the operands, or the bb
	 rank, whichever is less.   */
      rank = 0;
      maxrank = bb_rank[bb_for_stmt(stmt)->index];
      rhs = GIMPLE_STMT_OPERAND (stmt, 1);
      n = TREE_OPERAND_LENGTH (rhs);
      if (n == 0)
	rank = MAX (rank, get_rank (rhs));
      else
	{
	  for (i = 0;
	       i < n
		 && TREE_OPERAND (rhs, i)
		 && rank != maxrank;
	       i++)
	    rank = MAX(rank, get_rank (TREE_OPERAND (rhs, i)));
	}

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "Rank for ");
	  print_generic_expr (dump_file, e, 0);
	  fprintf (dump_file, " is %ld\n", (rank + 1));
	}

      /* Note the rank in the hashtable so we don't recompute it.  */
      insert_operand_rank (e, (rank + 1));
      return (rank + 1);
    }

  /* Globals, etc,  are rank 0 */
  return 0;
}

DEF_VEC_P(operand_entry_t);
DEF_VEC_ALLOC_P(operand_entry_t, heap);

/* We want integer ones to end up last no matter what, since they are
   the ones we can do the most with.  */
#define INTEGER_CONST_TYPE 1 << 3
#define FLOAT_CONST_TYPE 1 << 2
#define OTHER_CONST_TYPE 1 << 1

/* Classify an invariant tree into integer, float, or other, so that
   we can sort them to be near other constants of the same type.  */
static inline int
constant_type (tree t)
{
  if (INTEGRAL_TYPE_P (TREE_TYPE (t)))
    return INTEGER_CONST_TYPE;
  else if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (t)))
    return FLOAT_CONST_TYPE;
  else
    return OTHER_CONST_TYPE;
}

/* qsort comparison function to sort operand entries PA and PB by rank
   so that the sorted array is ordered by rank in decreasing order.  */
static int
sort_by_operand_rank (const void *pa, const void *pb)
{
  const operand_entry_t oea = *(const operand_entry_t *)pa;
  const operand_entry_t oeb = *(const operand_entry_t *)pb;

  /* It's nicer for optimize_expression if constants that are likely
     to fold when added/multiplied//whatever are put next to each
     other.  Since all constants have rank 0, order them by type.  */
  if (oeb->rank == 0 &&  oea->rank == 0)
    return constant_type (oeb->op) - constant_type (oea->op);

  /* Lastly, make sure the versions that are the same go next to each
     other.  We use SSA_NAME_VERSION because it's stable.  */
  if ((oeb->rank - oea->rank == 0)
      && TREE_CODE (oea->op) == SSA_NAME
      && TREE_CODE (oeb->op) == SSA_NAME)
    return SSA_NAME_VERSION (oeb->op) - SSA_NAME_VERSION (oea->op);

  return oeb->rank - oea->rank;
}

/* Add an operand entry to *OPS for the tree operand OP.  */

static void
add_to_ops_vec (VEC(operand_entry_t, heap) **ops, tree op)
{
  operand_entry_t oe = (operand_entry_t) pool_alloc (operand_entry_pool);

  oe->op = op;
  oe->rank = get_rank (op);
  VEC_safe_push (operand_entry_t, heap, *ops, oe);
}

/* Return true if STMT is reassociable operation containing a binary
   operation with tree code CODE, and is inside LOOP.  */

static bool
is_reassociable_op (tree stmt, enum tree_code code, struct loop *loop)
{
  basic_block bb;

  if (IS_EMPTY_STMT (stmt))
    return false;

  bb = bb_for_stmt (stmt);
  if (!flow_bb_inside_loop_p (loop, bb))
    return false;

  if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
      && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == code
      && has_single_use (GIMPLE_STMT_OPERAND (stmt, 0)))
    return true;
  return false;
}


/* Given NAME, if NAME is defined by a unary operation OPCODE, return the
   operand of the negate operation.  Otherwise, return NULL.  */

static tree
get_unary_op (tree name, enum tree_code opcode)
{
  tree stmt = SSA_NAME_DEF_STMT (name);
  tree rhs;

  if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT)
    return NULL_TREE;

  rhs = GIMPLE_STMT_OPERAND (stmt, 1);
  if (TREE_CODE (rhs) == opcode)
    return TREE_OPERAND (rhs, 0);
  return NULL_TREE;
}

/* If CURR and LAST are a pair of ops that OPCODE allows us to
   eliminate through equivalences, do so, remove them from OPS, and
   return true.  Otherwise, return false.  */

static bool
eliminate_duplicate_pair (enum tree_code opcode,
			  VEC (operand_entry_t, heap) **ops,
			  bool *all_done,
			  unsigned int i,
			  operand_entry_t curr,
			  operand_entry_t last)
{

  /* If we have two of the same op, and the opcode is & |, min, or max,
     we can eliminate one of them.
     If we have two of the same op, and the opcode is ^, we can
     eliminate both of them.  */

  if (last && last->op == curr->op)
    {
      switch (opcode)
	{
	case MAX_EXPR:
	case MIN_EXPR:
	case BIT_IOR_EXPR:
	case BIT_AND_EXPR:
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "Equivalence: ");
	      print_generic_expr (dump_file, curr->op, 0);
	      fprintf (dump_file, " [&|minmax] ");
	      print_generic_expr (dump_file, last->op, 0);
	      fprintf (dump_file, " -> ");
	      print_generic_stmt (dump_file, last->op, 0);
	    }

	  VEC_ordered_remove (operand_entry_t, *ops, i);
	  reassociate_stats.ops_eliminated ++;

	  return true;

	case BIT_XOR_EXPR:
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "Equivalence: ");
	      print_generic_expr (dump_file, curr->op, 0);
	      fprintf (dump_file, " ^ ");
	      print_generic_expr (dump_file, last->op, 0);
	      fprintf (dump_file, " -> nothing\n");
	    }

	  reassociate_stats.ops_eliminated += 2;

	  if (VEC_length (operand_entry_t, *ops) == 2)
	    {
	      VEC_free (operand_entry_t, heap, *ops);
	      *ops = NULL;
	      add_to_ops_vec (ops, fold_convert (TREE_TYPE (last->op), 
						 integer_zero_node));
	      *all_done = true;
	    }
	  else
	    {
	      VEC_ordered_remove (operand_entry_t, *ops, i-1);
	      VEC_ordered_remove (operand_entry_t, *ops, i-1);
	    }

	  return true;

	default:
	  break;
	}
    }
  return false;
}

/* If OPCODE is PLUS_EXPR, CURR->OP is really a negate expression,
   look in OPS for a corresponding positive operation to cancel it
   out.  If we find one, remove the other from OPS, replace
   OPS[CURRINDEX] with 0, and return true.  Otherwise, return
   false. */

static bool
eliminate_plus_minus_pair (enum tree_code opcode,
			   VEC (operand_entry_t, heap) **ops,
			   unsigned int currindex,
			   operand_entry_t curr)
{
  tree negateop;
  unsigned int i;
  operand_entry_t oe;

  if (opcode != PLUS_EXPR || TREE_CODE (curr->op) != SSA_NAME)
    return false;

  negateop = get_unary_op (curr->op, NEGATE_EXPR);
  if (negateop == NULL_TREE)
    return false;

  /* Any non-negated version will have a rank that is one less than
     the current rank.  So once we hit those ranks, if we don't find
     one, we can stop.  */

  for (i = currindex + 1;
       VEC_iterate (operand_entry_t, *ops, i, oe)
       && oe->rank >= curr->rank - 1 ;
       i++)
    {
      if (oe->op == negateop)
	{

	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "Equivalence: ");
	      print_generic_expr (dump_file, negateop, 0);
	      fprintf (dump_file, " + -");
	      print_generic_expr (dump_file, oe->op, 0);
	      fprintf (dump_file, " -> 0\n");
	    }

	  VEC_ordered_remove (operand_entry_t, *ops, i);
	  add_to_ops_vec (ops, fold_convert(TREE_TYPE (oe->op), 
					    integer_zero_node));
	  VEC_ordered_remove (operand_entry_t, *ops, currindex);
	  reassociate_stats.ops_eliminated ++;

	  return true;
	}
    }

  return false;
}

/* If OPCODE is BIT_IOR_EXPR, BIT_AND_EXPR, and, CURR->OP is really a
   bitwise not expression, look in OPS for a corresponding operand to
   cancel it out.  If we find one, remove the other from OPS, replace
   OPS[CURRINDEX] with 0, and return true.  Otherwise, return
   false. */

static bool
eliminate_not_pairs (enum tree_code opcode,
		     VEC (operand_entry_t, heap) **ops,
		     unsigned int currindex,
		     operand_entry_t curr)
{
  tree notop;
  unsigned int i;
  operand_entry_t oe;

  if ((opcode != BIT_IOR_EXPR && opcode != BIT_AND_EXPR)
      || TREE_CODE (curr->op) != SSA_NAME)
    return false;

  notop = get_unary_op (curr->op, BIT_NOT_EXPR);
  if (notop == NULL_TREE)
    return false;

  /* Any non-not version will have a rank that is one less than
     the current rank.  So once we hit those ranks, if we don't find
     one, we can stop.  */

  for (i = currindex + 1;
       VEC_iterate (operand_entry_t, *ops, i, oe)
       && oe->rank >= curr->rank - 1;
       i++)
    {
      if (oe->op == notop)
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "Equivalence: ");
	      print_generic_expr (dump_file, notop, 0);
	      if (opcode == BIT_AND_EXPR)
		fprintf (dump_file, " & ~");
	      else if (opcode == BIT_IOR_EXPR)
		fprintf (dump_file, " | ~");
	      print_generic_expr (dump_file, oe->op, 0);
	      if (opcode == BIT_AND_EXPR)
		fprintf (dump_file, " -> 0\n");
	      else if (opcode == BIT_IOR_EXPR)
		fprintf (dump_file, " -> -1\n");
	    }

	  if (opcode == BIT_AND_EXPR)
	    oe->op = fold_convert (TREE_TYPE (oe->op), integer_zero_node);
	  else if (opcode == BIT_IOR_EXPR)
	    oe->op = build_low_bits_mask (TREE_TYPE (oe->op),
					  TYPE_PRECISION (TREE_TYPE (oe->op)));

	  reassociate_stats.ops_eliminated 
	    += VEC_length (operand_entry_t, *ops) - 1;
	  VEC_free (operand_entry_t, heap, *ops);
	  *ops = NULL;
	  VEC_safe_push (operand_entry_t, heap, *ops, oe);
	  return true;
	}
    }

  return false;
}

/* Use constant value that may be present in OPS to try to eliminate
   operands.  Note that this function is only really used when we've
   eliminated ops for other reasons, or merged constants.  Across
   single statements, fold already does all of this, plus more.  There
   is little point in duplicating logic, so I've only included the
   identities that I could ever construct testcases to trigger.  */

static void
eliminate_using_constants (enum tree_code opcode,
			   VEC(operand_entry_t, heap) **ops)
{
  operand_entry_t oelast = VEC_last (operand_entry_t, *ops);
  tree type = TREE_TYPE (oelast->op);

  if (oelast->rank == 0
      && (INTEGRAL_TYPE_P (type) || FLOAT_TYPE_P (type)))
    {
      switch (opcode)
	{
	case BIT_AND_EXPR:
	  if (integer_zerop (oelast->op))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found & 0, removing all other ops\n");

		  reassociate_stats.ops_eliminated 
		    += VEC_length (operand_entry_t, *ops) - 1;
		  
		  VEC_free (operand_entry_t, heap, *ops);
		  *ops = NULL;
		  VEC_safe_push (operand_entry_t, heap, *ops, oelast);
		  return;
		}
	    }
	  else if (integer_all_onesp (oelast->op))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found & -1, removing\n");
		  VEC_pop (operand_entry_t, *ops);
		  reassociate_stats.ops_eliminated++;
		}
	    }
	  break;
	case BIT_IOR_EXPR:
	  if (integer_all_onesp (oelast->op))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found | -1, removing all other ops\n");

		  reassociate_stats.ops_eliminated 
		    += VEC_length (operand_entry_t, *ops) - 1;
		  
		  VEC_free (operand_entry_t, heap, *ops);
		  *ops = NULL;
		  VEC_safe_push (operand_entry_t, heap, *ops, oelast);
		  return;
		}
	    }	  
	  else if (integer_zerop (oelast->op))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found | 0, removing\n");
		  VEC_pop (operand_entry_t, *ops);
		  reassociate_stats.ops_eliminated++;
		}
	    }
	  break;
	case MULT_EXPR:
	  if (integer_zerop (oelast->op)
	      || (FLOAT_TYPE_P (type)
		  && !HONOR_NANS (TYPE_MODE (type))
		  && !HONOR_SIGNED_ZEROS (TYPE_MODE (type))
		  && real_zerop (oelast->op)))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found * 0, removing all other ops\n");
		  
		  reassociate_stats.ops_eliminated 
		    += VEC_length (operand_entry_t, *ops) - 1;
		  VEC_free (operand_entry_t, heap, *ops);
		  *ops = NULL;
		  VEC_safe_push (operand_entry_t, heap, *ops, oelast);
		  return;
		}
	    }
	  else if (integer_onep (oelast->op)
		   || (FLOAT_TYPE_P (type)
		       && !HONOR_SNANS (TYPE_MODE (type))
		       && real_onep (oelast->op)))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found * 1, removing\n");
		  VEC_pop (operand_entry_t, *ops);
		  reassociate_stats.ops_eliminated++;
		  return;
		}
	    }
	  break;
	case BIT_XOR_EXPR:
	case PLUS_EXPR:
	case MINUS_EXPR:
	  if (integer_zerop (oelast->op)
	      || (FLOAT_TYPE_P (type)
		  && (opcode == PLUS_EXPR || opcode == MINUS_EXPR)
		  && fold_real_zero_addition_p (type, oelast->op,
						opcode == MINUS_EXPR)))
	    {
	      if (VEC_length (operand_entry_t, *ops) != 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    fprintf (dump_file, "Found [|^+] 0, removing\n");
		  VEC_pop (operand_entry_t, *ops);
		  reassociate_stats.ops_eliminated++;
		  return;
		}
	    }
	  break;
	default:
	  break;
	}
    }
}

/* Perform various identities and other optimizations on the list of
   operand entries, stored in OPS.  The tree code for the binary
   operation between all the operands is OPCODE.  */

static void
optimize_ops_list (enum tree_code opcode,
		   VEC (operand_entry_t, heap) **ops)
{
  unsigned int length = VEC_length (operand_entry_t, *ops);
  unsigned int i;
  operand_entry_t oe;
  operand_entry_t oelast = NULL;
  bool iterate = false;

  if (length == 1)
    return;

  oelast = VEC_last (operand_entry_t, *ops);

  /* If the last two are constants, pop the constants off, merge them
     and try the next two.  */
  if (oelast->rank == 0 && is_gimple_min_invariant (oelast->op))
    {
      operand_entry_t oelm1 = VEC_index (operand_entry_t, *ops, length - 2);

      if (oelm1->rank == 0
	  && is_gimple_min_invariant (oelm1->op)
	  && useless_type_conversion_p (TREE_TYPE (oelm1->op),
				       TREE_TYPE (oelast->op)))
	{
	  tree folded = fold_binary (opcode, TREE_TYPE (oelm1->op),
				     oelm1->op, oelast->op);

	  if (folded && is_gimple_min_invariant (folded))
	    {
	      if (dump_file && (dump_flags & TDF_DETAILS))
		fprintf (dump_file, "Merging constants\n");

	      VEC_pop (operand_entry_t, *ops);
	      VEC_pop (operand_entry_t, *ops);

	      add_to_ops_vec (ops, folded);
	      reassociate_stats.constants_eliminated++;

	      optimize_ops_list (opcode, ops);
	      return;
	    }
	}
    }

  eliminate_using_constants (opcode, ops);
  oelast = NULL;

  for (i = 0; VEC_iterate (operand_entry_t, *ops, i, oe);)
    {
      bool done = false;

      if (eliminate_not_pairs (opcode, ops, i, oe))
	return;
      if (eliminate_duplicate_pair (opcode, ops, &done, i, oe, oelast)
	  || (!done && eliminate_plus_minus_pair (opcode, ops, i, oe)))
	{
	  if (done)
	    return;
	  iterate = true;
	  oelast = NULL;
	  continue;
	}
      oelast = oe;
      i++;
    }

  length  = VEC_length (operand_entry_t, *ops);
  oelast = VEC_last (operand_entry_t, *ops);

  if (iterate)
    optimize_ops_list (opcode, ops);
}

/* Return true if OPERAND is defined by a PHI node which uses the LHS
   of STMT in it's operands.  This is also known as a "destructive
   update" operation.  */

static bool
is_phi_for_stmt (tree stmt, tree operand)
{
  tree def_stmt;
  tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
  use_operand_p arg_p;
  ssa_op_iter i;

  if (TREE_CODE (operand) != SSA_NAME)
    return false;

  def_stmt = SSA_NAME_DEF_STMT (operand);
  if (TREE_CODE (def_stmt) != PHI_NODE)
    return false;

  FOR_EACH_PHI_ARG (arg_p, def_stmt, i, SSA_OP_USE)
    if (lhs == USE_FROM_PTR (arg_p))
      return true;
  return false;
}

/* Recursively rewrite our linearized statements so that the operators
   match those in OPS[OPINDEX], putting the computation in rank
   order.  */

static void
rewrite_expr_tree (tree stmt, unsigned int opindex,
		   VEC(operand_entry_t, heap) * ops)
{
  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
  operand_entry_t oe;

  /* If we have three operands left, then we want to make sure the one
     that gets the double binary op are the ones with the same rank.

     The alternative we try is to see if this is a destructive
     update style statement, which is like:
     b = phi (a, ...)
     a = c + b;
     In that case, we want to use the destructive update form to
     expose the possible vectorizer sum reduction opportunity.
     In that case, the third operand will be the phi node.

     We could, of course, try to be better as noted above, and do a
     lot of work to try to find these opportunities in >3 operand
     cases, but it is unlikely to be worth it.  */
  if (opindex + 3 == VEC_length (operand_entry_t, ops))
    {
      operand_entry_t oe1, oe2, oe3;

      oe1 = VEC_index (operand_entry_t, ops, opindex);
      oe2 = VEC_index (operand_entry_t, ops, opindex + 1);
      oe3 = VEC_index (operand_entry_t, ops, opindex + 2);

      if ((oe1->rank == oe2->rank
	   && oe2->rank != oe3->rank)
	  || (is_phi_for_stmt (stmt, oe3->op)
	      && !is_phi_for_stmt (stmt, oe1->op)
	      && !is_phi_for_stmt (stmt, oe2->op)))
	{
	  struct operand_entry temp = *oe3;
	  oe3->op = oe1->op;
	  oe3->rank = oe1->rank;
	  oe1->op = temp.op;
	  oe1->rank= temp.rank;
	}
      else if ((oe1->rank == oe3->rank
		&& oe2->rank != oe3->rank)
	       || (is_phi_for_stmt (stmt, oe2->op)
		   && !is_phi_for_stmt (stmt, oe1->op)
		   && !is_phi_for_stmt (stmt, oe3->op)))
	{
	  struct operand_entry temp = *oe2;
	  oe2->op = oe1->op;
	  oe2->rank = oe1->rank;
	  oe1->op = temp.op;
	  oe1->rank= temp.rank;
	}
    }

  /* The final recursion case for this function is that you have
     exactly two operations left.
     If we had one exactly one op in the entire list to start with, we
     would have never called this function, and the tail recursion
     rewrites them one at a time.  */
  if (opindex + 2 == VEC_length (operand_entry_t, ops))
    {
      operand_entry_t oe1, oe2;

      oe1 = VEC_index (operand_entry_t, ops, opindex);
      oe2 = VEC_index (operand_entry_t, ops, opindex + 1);

      if (TREE_OPERAND (rhs, 0) != oe1->op
	  || TREE_OPERAND (rhs, 1) != oe2->op)
	{

	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "Transforming ");
	      print_generic_expr (dump_file, rhs, 0);
	    }

	  TREE_OPERAND (rhs, 0) = oe1->op;
	  TREE_OPERAND (rhs, 1) = oe2->op;
	  update_stmt (stmt);

	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, " into ");
	      print_generic_stmt (dump_file, rhs, 0);
	    }

	}
      return;
    }

  /* If we hit here, we should have 3 or more ops left.  */
  gcc_assert (opindex + 2 < VEC_length (operand_entry_t, ops));

  /* Rewrite the next operator.  */
  oe = VEC_index (operand_entry_t, ops, opindex);

  if (oe->op != TREE_OPERAND (rhs, 1))
    {

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "Transforming ");
	  print_generic_expr (dump_file, rhs, 0);
	}

      TREE_OPERAND (rhs, 1) = oe->op;
      update_stmt (stmt);

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, " into ");
	  print_generic_stmt (dump_file, rhs, 0);
	}
    }
  /* Recurse on the LHS of the binary operator, which is guaranteed to
     be the non-leaf side.  */
  rewrite_expr_tree (SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0)),
		     opindex + 1, ops);
}

/* Transform STMT, which is really (A +B) + (C + D) into the left
   linear form, ((A+B)+C)+D.
   Recurse on D if necessary.  */

static void
linearize_expr (tree stmt)
{
  block_stmt_iterator bsinow, bsirhs;
  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
  enum tree_code rhscode = TREE_CODE (rhs);
  tree binrhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1));
  tree binlhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
  tree newbinrhs = NULL_TREE;
  struct loop *loop = loop_containing_stmt (stmt);

  gcc_assert (is_reassociable_op (binlhs, TREE_CODE (rhs), loop)
	      && is_reassociable_op (binrhs, TREE_CODE (rhs), loop));

  bsinow = bsi_for_stmt (stmt);
  bsirhs = bsi_for_stmt (binrhs);
  bsi_move_before (&bsirhs, &bsinow);

  TREE_OPERAND (rhs, 1) = TREE_OPERAND (GIMPLE_STMT_OPERAND (binrhs, 1), 0);
  if (TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME)
    newbinrhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1));
  TREE_OPERAND (GIMPLE_STMT_OPERAND (binrhs, 1), 0)
    = GIMPLE_STMT_OPERAND (binlhs, 0);
  TREE_OPERAND (rhs, 0) = GIMPLE_STMT_OPERAND (binrhs, 0);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Linearized: ");
      print_generic_stmt (dump_file, rhs, 0);
    }

  reassociate_stats.linearized++;
  update_stmt (binrhs);
  update_stmt (binlhs);
  update_stmt (stmt);
  TREE_VISITED (binrhs) = 1;
  TREE_VISITED (binlhs) = 1;
  TREE_VISITED (stmt) = 1;

  /* Tail recurse on the new rhs if it still needs reassociation.  */
  if (newbinrhs && is_reassociable_op (newbinrhs, rhscode, loop))
    linearize_expr (stmt);
}

/* If LHS has a single immediate use that is a GIMPLE_MODIFY_STMT, return
   it.  Otherwise, return NULL.  */

static tree
get_single_immediate_use (tree lhs)
{
  use_operand_p immuse;
  tree immusestmt;

  if (TREE_CODE (lhs) == SSA_NAME
      && single_imm_use (lhs, &immuse, &immusestmt))
    {
      if (TREE_CODE (immusestmt) == RETURN_EXPR)
	immusestmt = TREE_OPERAND (immusestmt, 0);
      if (TREE_CODE (immusestmt) == GIMPLE_MODIFY_STMT)
	return immusestmt;
    }
  return NULL_TREE;
}
static VEC(tree, heap) *broken_up_subtracts;


/* Recursively negate the value of TONEGATE, and return the SSA_NAME
   representing the negated value.  Insertions of any necessary
   instructions go before BSI.
   This function is recursive in that, if you hand it "a_5" as the
   value to negate, and a_5 is defined by "a_5 = b_3 + b_4", it will
   transform b_3 + b_4 into a_5 = -b_3 + -b_4.  */

static tree
negate_value (tree tonegate, block_stmt_iterator *bsi)
{
  tree negatedef = tonegate;
  tree resultofnegate;

  if (TREE_CODE (tonegate) == SSA_NAME)
    negatedef = SSA_NAME_DEF_STMT (tonegate);

  /* If we are trying to negate a name, defined by an add, negate the
     add operands instead.  */
  if (TREE_CODE (tonegate) == SSA_NAME
      && TREE_CODE (negatedef) == GIMPLE_MODIFY_STMT
      && TREE_CODE (GIMPLE_STMT_OPERAND (negatedef, 0)) == SSA_NAME
      && has_single_use (GIMPLE_STMT_OPERAND (negatedef, 0))
      && TREE_CODE (GIMPLE_STMT_OPERAND (negatedef, 1)) == PLUS_EXPR)
    {
      block_stmt_iterator bsi;
      tree binop = GIMPLE_STMT_OPERAND (negatedef, 1);

      bsi = bsi_for_stmt (negatedef);
      TREE_OPERAND (binop, 0) = negate_value (TREE_OPERAND (binop, 0),
					      &bsi);
      bsi = bsi_for_stmt (negatedef);
      TREE_OPERAND (binop, 1) = negate_value (TREE_OPERAND (binop, 1),
					      &bsi);
      update_stmt (negatedef);
      return GIMPLE_STMT_OPERAND (negatedef, 0);
    }

  tonegate = fold_build1 (NEGATE_EXPR, TREE_TYPE (tonegate), tonegate);
  resultofnegate = force_gimple_operand_bsi (bsi, tonegate, true,
					     NULL_TREE, true, BSI_SAME_STMT);
  VEC_safe_push (tree, heap, broken_up_subtracts, resultofnegate);
  return resultofnegate;

}

/* Return true if we should break up the subtract in STMT into an add
   with negate.  This is true when we the subtract operands are really
   adds, or the subtract itself is used in an add expression.  In
   either case, breaking up the subtract into an add with negate
   exposes the adds to reassociation.  */

static bool
should_break_up_subtract (tree stmt)
{

  tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
  tree binlhs = TREE_OPERAND (rhs, 0);
  tree binrhs = TREE_OPERAND (rhs, 1);
  tree immusestmt;
  struct loop *loop = loop_containing_stmt (stmt);

  if (TREE_CODE (binlhs) == SSA_NAME
      && is_reassociable_op (SSA_NAME_DEF_STMT (binlhs), PLUS_EXPR, loop))
    return true;

  if (TREE_CODE (binrhs) == SSA_NAME
      && is_reassociable_op (SSA_NAME_DEF_STMT (binrhs), PLUS_EXPR, loop))
    return true;

  if (TREE_CODE (lhs) == SSA_NAME
      && (immusestmt = get_single_immediate_use (lhs))
      && TREE_CODE (GIMPLE_STMT_OPERAND (immusestmt, 1)) == PLUS_EXPR)
    return true;
  return false;

}

/* Transform STMT from A - B into A + -B.  */

static void
break_up_subtract (tree stmt, block_stmt_iterator *bsi)
{
  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Breaking up subtract ");
      print_generic_stmt (dump_file, stmt, 0);
    }

  TREE_SET_CODE (GIMPLE_STMT_OPERAND (stmt, 1), PLUS_EXPR);
  TREE_OPERAND (rhs, 1) = negate_value (TREE_OPERAND (rhs, 1), bsi);

  update_stmt (stmt);
}

/* Recursively linearize a binary expression that is the RHS of STMT.
   Place the operands of the expression tree in the vector named OPS.  */

static void
linearize_expr_tree (VEC(operand_entry_t, heap) **ops, tree stmt)
{
  block_stmt_iterator bsinow, bsilhs;
  tree rhs = GENERIC_TREE_OPERAND (stmt, 1);
  tree binrhs = TREE_OPERAND (rhs, 1);
  tree binlhs = TREE_OPERAND (rhs, 0);
  tree binlhsdef, binrhsdef;
  bool binlhsisreassoc = false;
  bool binrhsisreassoc = false;
  enum tree_code rhscode = TREE_CODE (rhs);
  struct loop *loop = loop_containing_stmt (stmt);

  TREE_VISITED (stmt) = 1;

  if (TREE_CODE (binlhs) == SSA_NAME)
    {
      binlhsdef = SSA_NAME_DEF_STMT (binlhs);
      binlhsisreassoc = is_reassociable_op (binlhsdef, rhscode, loop);
    }

  if (TREE_CODE (binrhs) == SSA_NAME)
    {
      binrhsdef = SSA_NAME_DEF_STMT (binrhs);
      binrhsisreassoc = is_reassociable_op (binrhsdef, rhscode, loop);
    }

  /* If the LHS is not reassociable, but the RHS is, we need to swap
     them.  If neither is reassociable, there is nothing we can do, so
     just put them in the ops vector.  If the LHS is reassociable,
     linearize it.  If both are reassociable, then linearize the RHS
     and the LHS.  */

  if (!binlhsisreassoc)
    {
      tree temp;

      if (!binrhsisreassoc)
	{
	  add_to_ops_vec (ops, binrhs);
	  add_to_ops_vec (ops, binlhs);
	  return;
	}

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "swapping operands of ");
	  print_generic_expr (dump_file, stmt, 0);
	}

      swap_tree_operands (stmt, &TREE_OPERAND (rhs, 0),
			  &TREE_OPERAND (rhs, 1));
      update_stmt (stmt);

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, " is now ");
	  print_generic_stmt (dump_file, stmt, 0);
	}

      /* We want to make it so the lhs is always the reassociative op,
	 so swap.  */
      temp = binlhs;
      binlhs = binrhs;
      binrhs = temp;
    }
  else if (binrhsisreassoc)
    {
      linearize_expr (stmt);
      gcc_assert (rhs == GIMPLE_STMT_OPERAND (stmt, 1));
      binlhs = TREE_OPERAND (rhs, 0);
      binrhs = TREE_OPERAND (rhs, 1);
    }

  gcc_assert (TREE_CODE (binrhs) != SSA_NAME
	      || !is_reassociable_op (SSA_NAME_DEF_STMT (binrhs),
				      rhscode, loop));
  bsinow = bsi_for_stmt (stmt);
  bsilhs = bsi_for_stmt (SSA_NAME_DEF_STMT (binlhs));
  bsi_move_before (&bsilhs, &bsinow);
  linearize_expr_tree (ops, SSA_NAME_DEF_STMT (binlhs));
  add_to_ops_vec (ops, binrhs);
}

/* Repropagate the negates back into subtracts, since no other pass
   currently does it.  */

static void
repropagate_negates (void)
{
  unsigned int i = 0;
  tree negate;

  for (i = 0; VEC_iterate (tree, broken_up_subtracts, i, negate); i++)
    {
      tree user = get_single_immediate_use (negate);

      /* The negate operand can be either operand of a PLUS_EXPR
	 (it can be the LHS if the RHS is a constant for example).

	 Force the negate operand to the RHS of the PLUS_EXPR, then
	 transform the PLUS_EXPR into a MINUS_EXPR.  */
      if (user
	  && TREE_CODE (user) == GIMPLE_MODIFY_STMT
	  && TREE_CODE (GIMPLE_STMT_OPERAND (user, 1)) == PLUS_EXPR)
	{
	  tree rhs = GIMPLE_STMT_OPERAND (user, 1);

	  /* If the negated operand appears on the LHS of the
	     PLUS_EXPR, exchange the operands of the PLUS_EXPR
	     to force the negated operand to the RHS of the PLUS_EXPR.  */
	  if (TREE_OPERAND (GIMPLE_STMT_OPERAND (user, 1), 0) == negate)
	    {
	      tree temp = TREE_OPERAND (rhs, 0);
	      TREE_OPERAND (rhs, 0) = TREE_OPERAND (rhs, 1);
	      TREE_OPERAND (rhs, 1) = temp;
	    }

	  /* Now transform the PLUS_EXPR into a MINUS_EXPR and replace
	     the RHS of the PLUS_EXPR with the operand of the NEGATE_EXPR.  */
	  if (TREE_OPERAND (GIMPLE_STMT_OPERAND (user, 1), 1) == negate)
	    {
	      TREE_SET_CODE (rhs, MINUS_EXPR);
	      TREE_OPERAND (rhs, 1) = get_unary_op (negate, NEGATE_EXPR);
	      update_stmt (user);
	    }
	}
    }
}

/* Break up subtract operations in block BB.

   We do this top down because we don't know whether the subtract is
   part of a possible chain of reassociation except at the top.
 
   IE given
   d = f + g
   c = a + e
   b = c - d
   q = b - r
   k = t - q
   
   we want to break up k = t - q, but we won't until we've transformed q
   = b - r, which won't be broken up until we transform b = c - d.  */

static void
break_up_subtract_bb (basic_block bb)
{
  block_stmt_iterator bsi;
  basic_block son;

  for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
    {
      tree stmt = bsi_stmt (bsi);

      if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
	{
	  tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
	  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);

	  TREE_VISITED (stmt) = 0;
	  /* If associative-math we can do reassociation for
	     non-integral types.  Or, we can do reassociation for
	     non-saturating fixed-point types.  */
	  if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs))
	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs)))
	      && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (rhs))
		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(lhs))
		  || !flag_associative_math)
	      && (!NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE (rhs))
		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(lhs))))
	    continue;

	  /* Check for a subtract used only in an addition.  If this
	     is the case, transform it into add of a negate for better
	     reassociation.  IE transform C = A-B into C = A + -B if C
	     is only used in an addition.  */
	  if (TREE_CODE (rhs) == MINUS_EXPR)
	    if (should_break_up_subtract (stmt))
	      break_up_subtract (stmt, &bsi);
	}
    }
  for (son = first_dom_son (CDI_DOMINATORS, bb);
       son;
       son = next_dom_son (CDI_DOMINATORS, son))
    break_up_subtract_bb (son);
}

/* Reassociate expressions in basic block BB and its post-dominator as
   children.  */

static void
reassociate_bb (basic_block bb)
{
  block_stmt_iterator bsi;
  basic_block son;

  for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi))
    {
      tree stmt = bsi_stmt (bsi);

      if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
	{
	  tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
	  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);

	  /* If this was part of an already processed tree, we don't
	     need to touch it again. */
	  if (TREE_VISITED (stmt))
	    continue;

	  /* If associative-math we can do reassociation for
	     non-integral types.  Or, we can do reassociation for
	     non-saturating fixed-point types.  */
	  if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs))
	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs)))
	      && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (rhs))
		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(lhs))
		  || !flag_associative_math)
	      && (!NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE (rhs))
		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(lhs))))
	    continue;

	  if (associative_tree_code (TREE_CODE (rhs)))
	    {
	      VEC(operand_entry_t, heap) *ops = NULL;

	      /* There may be no immediate uses left by the time we
		 get here because we may have eliminated them all.  */
	      if (TREE_CODE (lhs) == SSA_NAME && has_zero_uses (lhs))
		continue;

	      TREE_VISITED (stmt) = 1;
	      linearize_expr_tree (&ops, stmt);
	      qsort (VEC_address (operand_entry_t, ops),
		     VEC_length (operand_entry_t, ops),
		     sizeof (operand_entry_t),
		     sort_by_operand_rank);
	      optimize_ops_list (TREE_CODE (rhs), &ops);

	      if (VEC_length (operand_entry_t, ops) == 1)
		{
		  if (dump_file && (dump_flags & TDF_DETAILS))
		    {
		      fprintf (dump_file, "Transforming ");
		      print_generic_expr (dump_file, rhs, 0);
		    }
		  GIMPLE_STMT_OPERAND (stmt, 1) 
		    = VEC_last (operand_entry_t, ops)->op;
		  update_stmt (stmt);

		  if (dump_file && (dump_flags & TDF_DETAILS))
		    {
		      fprintf (dump_file, " into ");
		      print_generic_stmt (dump_file,
					  GIMPLE_STMT_OPERAND (stmt, 1), 0);
		    }
		}
	      else
		{
		  rewrite_expr_tree (stmt, 0, ops);
		}

	      VEC_free (operand_entry_t, heap, ops);
	    }
	}
    }
  for (son = first_dom_son (CDI_POST_DOMINATORS, bb);
       son;
       son = next_dom_son (CDI_POST_DOMINATORS, son))
    reassociate_bb (son);
}

void dump_ops_vector (FILE *file, VEC (operand_entry_t, heap) *ops);
void debug_ops_vector (VEC (operand_entry_t, heap) *ops);

/* Dump the operand entry vector OPS to FILE.  */

void
dump_ops_vector (FILE *file, VEC (operand_entry_t, heap) *ops)
{
  operand_entry_t oe;
  unsigned int i;

  for (i = 0; VEC_iterate (operand_entry_t, ops, i, oe); i++)
    {
      fprintf (file, "Op %d -> rank: %d, tree: ", i, oe->rank);
      print_generic_stmt (file, oe->op, 0);
    }
}

/* Dump the operand entry vector OPS to STDERR.  */

void
debug_ops_vector (VEC (operand_entry_t, heap) *ops)
{
  dump_ops_vector (stderr, ops);
}

static void
do_reassoc (void)
{
  break_up_subtract_bb (ENTRY_BLOCK_PTR);
  reassociate_bb (EXIT_BLOCK_PTR);
}

/* Initialize the reassociation pass.  */

static void
init_reassoc (void)
{
  int i;
  long rank = 2;
  tree param;
  int *bbs = XNEWVEC (int, last_basic_block + 1);

  /* Find the loops, so that we can prevent moving calculations in
     them.  */
  loop_optimizer_init (AVOID_CFG_MODIFICATIONS);

  memset (&reassociate_stats, 0, sizeof (reassociate_stats));

  operand_entry_pool = create_alloc_pool ("operand entry pool",
					  sizeof (struct operand_entry), 30);

  /* Reverse RPO (Reverse Post Order) will give us something where
     deeper loops come later.  */
  pre_and_rev_post_order_compute (NULL, bbs, false);
  bb_rank = XCNEWVEC (long, last_basic_block + 1);
  operand_rank = pointer_map_create ();

  /* Give each argument a distinct rank.   */
  for (param = DECL_ARGUMENTS (current_function_decl);
       param;
       param = TREE_CHAIN (param))
    {
      if (gimple_default_def (cfun, param) != NULL)
	{
	  tree def = gimple_default_def (cfun, param);
	  insert_operand_rank (def, ++rank);
	}
    }

  /* Give the chain decl a distinct rank. */
  if (cfun->static_chain_decl != NULL)
    {
      tree def = gimple_default_def (cfun, cfun->static_chain_decl);
      if (def != NULL)
	insert_operand_rank (def, ++rank);
    }

  /* Set up rank for each BB  */
  for (i = 0; i < n_basic_blocks - NUM_FIXED_BLOCKS; i++)
    bb_rank[bbs[i]] = ++rank  << 16;

  free (bbs);
  calculate_dominance_info (CDI_POST_DOMINATORS);
  broken_up_subtracts = NULL;
}

/* Cleanup after the reassociation pass, and print stats if
   requested.  */

static void
fini_reassoc (void)
{
  if (dump_file && (dump_flags & TDF_STATS))
    {
      fprintf (dump_file, "Reassociation stats:\n");
      fprintf (dump_file, "Linearized: %d\n", 
	       reassociate_stats.linearized);
      fprintf (dump_file, "Constants eliminated: %d\n",
	       reassociate_stats.constants_eliminated);
      fprintf (dump_file, "Ops eliminated: %d\n",
	       reassociate_stats.ops_eliminated);
      fprintf (dump_file, "Statements rewritten: %d\n",
	       reassociate_stats.rewritten);
    }

  pointer_map_destroy (operand_rank);
  free_alloc_pool (operand_entry_pool);
  free (bb_rank);
  VEC_free (tree, heap, broken_up_subtracts);
  free_dominance_info (CDI_POST_DOMINATORS);
  loop_optimizer_finalize ();
}

/* Gate and execute functions for Reassociation.  */

static unsigned int
execute_reassoc (void)
{
  init_reassoc ();

  do_reassoc ();
  repropagate_negates ();

  fini_reassoc ();
  return 0;
}

static bool
gate_tree_ssa_reassoc (void)
{
  return flag_tree_reassoc != 0;
}

struct gimple_opt_pass pass_reassoc =
{
 {
  GIMPLE_PASS,
  "reassoc",				/* name */
  gate_tree_ssa_reassoc,		/* gate */
  execute_reassoc,			/* execute */
  NULL,					/* sub */
  NULL,					/* next */
  0,					/* static_pass_number */
  TV_TREE_REASSOC,			/* tv_id */
  PROP_cfg | PROP_ssa | PROP_alias,	/* properties_required */
  0,					/* properties_provided */
  0,					/* properties_destroyed */
  0,					/* todo_flags_start */
  TODO_dump_func | TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
 }
};