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
|
/* Post reload partially redundant load elimination
Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010, 2011
Free Software Foundation, Inc.
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 "diagnostic-core.h"
#include "rtl.h"
#include "tree.h"
#include "tm_p.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
#include "insn-config.h"
#include "recog.h"
#include "basic-block.h"
#include "output.h"
#include "function.h"
#include "expr.h"
#include "except.h"
#include "intl.h"
#include "obstack.h"
#include "hashtab.h"
#include "params.h"
#include "target.h"
#include "timevar.h"
#include "tree-pass.h"
#include "dbgcnt.h"
/* The following code implements gcse after reload, the purpose of this
pass is to cleanup redundant loads generated by reload and other
optimizations that come after gcse. It searches for simple inter-block
redundancies and tries to eliminate them by adding moves and loads
in cold places.
Perform partially redundant load elimination, try to eliminate redundant
loads created by the reload pass. We try to look for full or partial
redundant loads fed by one or more loads/stores in predecessor BBs,
and try adding loads to make them fully redundant. We also check if
it's worth adding loads to be able to delete the redundant load.
Algorithm:
1. Build available expressions hash table:
For each load/store instruction, if the loaded/stored memory didn't
change until the end of the basic block add this memory expression to
the hash table.
2. Perform Redundancy elimination:
For each load instruction do the following:
perform partial redundancy elimination, check if it's worth adding
loads to make the load fully redundant. If so add loads and
register copies and delete the load.
3. Delete instructions made redundant in step 2.
Future enhancement:
If the loaded register is used/defined between load and some store,
look for some other free register between load and all its stores,
and replace the load with a copy from this register to the loaded
register.
*/
/* Keep statistics of this pass. */
static struct
{
int moves_inserted;
int copies_inserted;
int insns_deleted;
} stats;
/* We need to keep a hash table of expressions. The table entries are of
type 'struct expr', and for each expression there is a single linked
list of occurrences. */
/* The table itself. */
static htab_t expr_table;
/* Expression elements in the hash table. */
struct expr
{
/* The expression (SET_SRC for expressions, PATTERN for assignments). */
rtx expr;
/* The same hash for this entry. */
hashval_t hash;
/* List of available occurrence in basic blocks in the function. */
struct occr *avail_occr;
};
static struct obstack expr_obstack;
/* Occurrence of an expression.
There is at most one occurrence per basic block. If a pattern appears
more than once, the last appearance is used. */
struct occr
{
/* Next occurrence of this expression. */
struct occr *next;
/* The insn that computes the expression. */
rtx insn;
/* Nonzero if this [anticipatable] occurrence has been deleted. */
char deleted_p;
};
static struct obstack occr_obstack;
/* The following structure holds the information about the occurrences of
the redundant instructions. */
struct unoccr
{
struct unoccr *next;
edge pred;
rtx insn;
};
static struct obstack unoccr_obstack;
/* Array where each element is the CUID if the insn that last set the hard
register with the number of the element, since the start of the current
basic block.
This array is used during the building of the hash table (step 1) to
determine if a reg is killed before the end of a basic block.
It is also used when eliminating partial redundancies (step 2) to see
if a reg was modified since the start of a basic block. */
static int *reg_avail_info;
/* A list of insns that may modify memory within the current basic block. */
struct modifies_mem
{
rtx insn;
struct modifies_mem *next;
};
static struct modifies_mem *modifies_mem_list;
/* The modifies_mem structs also go on an obstack, only this obstack is
freed each time after completing the analysis or transformations on
a basic block. So we allocate a dummy modifies_mem_obstack_bottom
object on the obstack to keep track of the bottom of the obstack. */
static struct obstack modifies_mem_obstack;
static struct modifies_mem *modifies_mem_obstack_bottom;
/* Mapping of insn UIDs to CUIDs.
CUIDs are like UIDs except they increase monotonically in each basic
block, have no gaps, and only apply to real insns. */
static int *uid_cuid;
#define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
/* Helpers for memory allocation/freeing. */
static void alloc_mem (void);
static void free_mem (void);
/* Support for hash table construction and transformations. */
static bool oprs_unchanged_p (rtx, rtx, bool);
static void record_last_reg_set_info (rtx, rtx);
static void record_last_reg_set_info_regno (rtx, int);
static void record_last_mem_set_info (rtx);
static void record_last_set_info (rtx, const_rtx, void *);
static void record_opr_changes (rtx);
static void find_mem_conflicts (rtx, const_rtx, void *);
static int load_killed_in_block_p (int, rtx, bool);
static void reset_opr_set_tables (void);
/* Hash table support. */
static hashval_t hash_expr (rtx, int *);
static hashval_t hash_expr_for_htab (const void *);
static int expr_equiv_p (const void *, const void *);
static void insert_expr_in_table (rtx, rtx);
static struct expr *lookup_expr_in_table (rtx);
static int dump_hash_table_entry (void **, void *);
static void dump_hash_table (FILE *);
/* Helpers for eliminate_partially_redundant_load. */
static bool reg_killed_on_edge (rtx, edge);
static bool reg_used_on_edge (rtx, edge);
static rtx get_avail_load_store_reg (rtx);
static bool bb_has_well_behaved_predecessors (basic_block);
static struct occr* get_bb_avail_insn (basic_block, struct occr *);
static void hash_scan_set (rtx);
static void compute_hash_table (void);
/* The work horses of this pass. */
static void eliminate_partially_redundant_load (basic_block,
rtx,
struct expr *);
static void eliminate_partially_redundant_loads (void);
/* Allocate memory for the CUID mapping array and register/memory
tracking tables. */
static void
alloc_mem (void)
{
int i;
basic_block bb;
rtx insn;
/* Find the largest UID and create a mapping from UIDs to CUIDs. */
uid_cuid = XCNEWVEC (int, get_max_uid () + 1);
i = 1;
FOR_EACH_BB (bb)
FOR_BB_INSNS (bb, insn)
{
if (INSN_P (insn))
uid_cuid[INSN_UID (insn)] = i++;
else
uid_cuid[INSN_UID (insn)] = i;
}
/* Allocate the available expressions hash table. We don't want to
make the hash table too small, but unnecessarily making it too large
also doesn't help. The i/4 is a gcse.c relic, and seems like a
reasonable choice. */
expr_table = htab_create (MAX (i / 4, 13),
hash_expr_for_htab, expr_equiv_p, NULL);
/* We allocate everything on obstacks because we often can roll back
the whole obstack to some point. Freeing obstacks is very fast. */
gcc_obstack_init (&expr_obstack);
gcc_obstack_init (&occr_obstack);
gcc_obstack_init (&unoccr_obstack);
gcc_obstack_init (&modifies_mem_obstack);
/* Working array used to track the last set for each register
in the current block. */
reg_avail_info = (int *) xmalloc (FIRST_PSEUDO_REGISTER * sizeof (int));
/* Put a dummy modifies_mem object on the modifies_mem_obstack, so we
can roll it back in reset_opr_set_tables. */
modifies_mem_obstack_bottom =
(struct modifies_mem *) obstack_alloc (&modifies_mem_obstack,
sizeof (struct modifies_mem));
}
/* Free memory allocated by alloc_mem. */
static void
free_mem (void)
{
free (uid_cuid);
htab_delete (expr_table);
obstack_free (&expr_obstack, NULL);
obstack_free (&occr_obstack, NULL);
obstack_free (&unoccr_obstack, NULL);
obstack_free (&modifies_mem_obstack, NULL);
free (reg_avail_info);
}
/* Hash expression X.
DO_NOT_RECORD_P is a boolean indicating if a volatile operand is found
or if the expression contains something we don't want to insert in the
table. */
static hashval_t
hash_expr (rtx x, int *do_not_record_p)
{
*do_not_record_p = 0;
return hash_rtx (x, GET_MODE (x), do_not_record_p,
NULL, /*have_reg_qty=*/false);
}
/* Callback for hashtab.
Return the hash value for expression EXP. We don't actually hash
here, we just return the cached hash value. */
static hashval_t
hash_expr_for_htab (const void *expp)
{
const struct expr *const exp = (const struct expr *) expp;
return exp->hash;
}
/* Callback for hashtab.
Return nonzero if exp1 is equivalent to exp2. */
static int
expr_equiv_p (const void *exp1p, const void *exp2p)
{
const struct expr *const exp1 = (const struct expr *) exp1p;
const struct expr *const exp2 = (const struct expr *) exp2p;
int equiv_p = exp_equiv_p (exp1->expr, exp2->expr, 0, true);
gcc_assert (!equiv_p || exp1->hash == exp2->hash);
return equiv_p;
}
/* Insert expression X in INSN in the hash TABLE.
If it is already present, record it as the last occurrence in INSN's
basic block. */
static void
insert_expr_in_table (rtx x, rtx insn)
{
int do_not_record_p;
hashval_t hash;
struct expr *cur_expr, **slot;
struct occr *avail_occr, *last_occr = NULL;
hash = hash_expr (x, &do_not_record_p);
/* Do not insert expression in the table if it contains volatile operands,
or if hash_expr determines the expression is something we don't want
to or can't handle. */
if (do_not_record_p)
return;
/* We anticipate that redundant expressions are rare, so for convenience
allocate a new hash table element here already and set its fields.
If we don't do this, we need a hack with a static struct expr. Anyway,
obstack_free is really fast and one more obstack_alloc doesn't hurt if
we're going to see more expressions later on. */
cur_expr = (struct expr *) obstack_alloc (&expr_obstack,
sizeof (struct expr));
cur_expr->expr = x;
cur_expr->hash = hash;
cur_expr->avail_occr = NULL;
slot = (struct expr **) htab_find_slot_with_hash (expr_table, cur_expr,
hash, INSERT);
if (! (*slot))
/* The expression isn't found, so insert it. */
*slot = cur_expr;
else
{
/* The expression is already in the table, so roll back the
obstack and use the existing table entry. */
obstack_free (&expr_obstack, cur_expr);
cur_expr = *slot;
}
/* Search for another occurrence in the same basic block. */
avail_occr = cur_expr->avail_occr;
while (avail_occr
&& BLOCK_FOR_INSN (avail_occr->insn) != BLOCK_FOR_INSN (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = avail_occr;
avail_occr = avail_occr->next;
}
if (avail_occr)
/* Found another instance of the expression in the same basic block.
Prefer this occurrence to the currently recorded one. We want
the last one in the block and the block is scanned from start
to end. */
avail_occr->insn = insn;
else
{
/* First occurrence of this expression in this basic block. */
avail_occr = (struct occr *) obstack_alloc (&occr_obstack,
sizeof (struct occr));
/* First occurrence of this expression in any block? */
if (cur_expr->avail_occr == NULL)
cur_expr->avail_occr = avail_occr;
else
last_occr->next = avail_occr;
avail_occr->insn = insn;
avail_occr->next = NULL;
avail_occr->deleted_p = 0;
}
}
/* Lookup pattern PAT in the expression hash table.
The result is a pointer to the table entry, or NULL if not found. */
static struct expr *
lookup_expr_in_table (rtx pat)
{
int do_not_record_p;
struct expr **slot, *tmp_expr;
hashval_t hash = hash_expr (pat, &do_not_record_p);
if (do_not_record_p)
return NULL;
tmp_expr = (struct expr *) obstack_alloc (&expr_obstack,
sizeof (struct expr));
tmp_expr->expr = pat;
tmp_expr->hash = hash;
tmp_expr->avail_occr = NULL;
slot = (struct expr **) htab_find_slot_with_hash (expr_table, tmp_expr,
hash, INSERT);
obstack_free (&expr_obstack, tmp_expr);
if (!slot)
return NULL;
else
return (*slot);
}
/* Dump all expressions and occurrences that are currently in the
expression hash table to FILE. */
/* This helper is called via htab_traverse. */
static int
dump_hash_table_entry (void **slot, void *filep)
{
struct expr *expr = (struct expr *) *slot;
FILE *file = (FILE *) filep;
struct occr *occr;
fprintf (file, "expr: ");
print_rtl (file, expr->expr);
fprintf (file,"\nhashcode: %u\n", expr->hash);
fprintf (file,"list of occurrences:\n");
occr = expr->avail_occr;
while (occr)
{
rtx insn = occr->insn;
print_rtl_single (file, insn);
fprintf (file, "\n");
occr = occr->next;
}
fprintf (file, "\n");
return 1;
}
static void
dump_hash_table (FILE *file)
{
fprintf (file, "\n\nexpression hash table\n");
fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
(long) htab_size (expr_table),
(long) htab_elements (expr_table),
htab_collisions (expr_table));
if (htab_elements (expr_table) > 0)
{
fprintf (file, "\n\ntable entries:\n");
htab_traverse (expr_table, dump_hash_table_entry, file);
}
fprintf (file, "\n");
}
/* Return true if register X is recorded as being set by an instruction
whose CUID is greater than the one given. */
static bool
reg_changed_after_insn_p (rtx x, int cuid)
{
unsigned int regno, end_regno;
regno = REGNO (x);
end_regno = END_HARD_REGNO (x);
do
if (reg_avail_info[regno] > cuid)
return true;
while (++regno < end_regno);
return false;
}
/* Return nonzero if the operands of expression X are unchanged
1) from the start of INSN's basic block up to but not including INSN
if AFTER_INSN is false, or
2) from INSN to the end of INSN's basic block if AFTER_INSN is true. */
static bool
oprs_unchanged_p (rtx x, rtx insn, bool after_insn)
{
int i, j;
enum rtx_code code;
const char *fmt;
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case REG:
/* We are called after register allocation. */
gcc_assert (REGNO (x) < FIRST_PSEUDO_REGISTER);
if (after_insn)
return !reg_changed_after_insn_p (x, INSN_CUID (insn) - 1);
else
return !reg_changed_after_insn_p (x, 0);
case MEM:
if (load_killed_in_block_p (INSN_CUID (insn), x, after_insn))
return 0;
else
return oprs_unchanged_p (XEXP (x, 0), insn, after_insn);
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case CONST_FIXED:
case CONST_VECTOR:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 1;
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
case PRE_MODIFY:
case POST_MODIFY:
if (after_insn)
return 0;
break;
default:
break;
}
for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
{
if (fmt[i] == 'e')
{
if (! oprs_unchanged_p (XEXP (x, i), insn, after_insn))
return 0;
}
else if (fmt[i] == 'E')
for (j = 0; j < XVECLEN (x, i); j++)
if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, after_insn))
return 0;
}
return 1;
}
/* Used for communication between find_mem_conflicts and
load_killed_in_block_p. Nonzero if find_mem_conflicts finds a
conflict between two memory references.
This is a bit of a hack to work around the limitations of note_stores. */
static int mems_conflict_p;
/* DEST is the output of an instruction. If it is a memory reference, and
possibly conflicts with the load found in DATA, then set mems_conflict_p
to a nonzero value. */
static void
find_mem_conflicts (rtx dest, const_rtx setter ATTRIBUTE_UNUSED,
void *data)
{
rtx mem_op = (rtx) data;
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
/* If DEST is not a MEM, then it will not conflict with the load. Note
that function calls are assumed to clobber memory, but are handled
elsewhere. */
if (! MEM_P (dest))
return;
if (true_dependence (dest, GET_MODE (dest), mem_op,
rtx_addr_varies_p))
mems_conflict_p = 1;
}
/* Return nonzero if the expression in X (a memory reference) is killed
in the current basic block before (if AFTER_INSN is false) or after
(if AFTER_INSN is true) the insn with the CUID in UID_LIMIT.
This function assumes that the modifies_mem table is flushed when
the hash table construction or redundancy elimination phases start
processing a new basic block. */
static int
load_killed_in_block_p (int uid_limit, rtx x, bool after_insn)
{
struct modifies_mem *list_entry = modifies_mem_list;
while (list_entry)
{
rtx setter = list_entry->insn;
/* Ignore entries in the list that do not apply. */
if ((after_insn
&& INSN_CUID (setter) < uid_limit)
|| (! after_insn
&& INSN_CUID (setter) > uid_limit))
{
list_entry = list_entry->next;
continue;
}
/* If SETTER is a call everything is clobbered. Note that calls
to pure functions are never put on the list, so we need not
worry about them. */
if (CALL_P (setter))
return 1;
/* SETTER must be an insn of some kind that sets memory. Call
note_stores to examine each hunk of memory that is modified.
It will set mems_conflict_p to nonzero if there may be a
conflict between X and SETTER. */
mems_conflict_p = 0;
note_stores (PATTERN (setter), find_mem_conflicts, x);
if (mems_conflict_p)
return 1;
list_entry = list_entry->next;
}
return 0;
}
/* Record register first/last/block set information for REGNO in INSN. */
static inline void
record_last_reg_set_info (rtx insn, rtx reg)
{
unsigned int regno, end_regno;
regno = REGNO (reg);
end_regno = END_HARD_REGNO (reg);
do
reg_avail_info[regno] = INSN_CUID (insn);
while (++regno < end_regno);
}
static inline void
record_last_reg_set_info_regno (rtx insn, int regno)
{
reg_avail_info[regno] = INSN_CUID (insn);
}
/* Record memory modification information for INSN. We do not actually care
about the memory location(s) that are set, or even how they are set (consider
a CALL_INSN). We merely need to record which insns modify memory. */
static void
record_last_mem_set_info (rtx insn)
{
struct modifies_mem *list_entry;
list_entry = (struct modifies_mem *) obstack_alloc (&modifies_mem_obstack,
sizeof (struct modifies_mem));
list_entry->insn = insn;
list_entry->next = modifies_mem_list;
modifies_mem_list = list_entry;
}
/* Called from compute_hash_table via note_stores to handle one
SET or CLOBBER in an insn. DATA is really the instruction in which
the SET is taking place. */
static void
record_last_set_info (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data)
{
rtx last_set_insn = (rtx) data;
if (GET_CODE (dest) == SUBREG)
dest = SUBREG_REG (dest);
if (REG_P (dest))
record_last_reg_set_info (last_set_insn, dest);
else if (MEM_P (dest))
{
/* Ignore pushes, they don't clobber memory. They may still
clobber the stack pointer though. Some targets do argument
pushes without adding REG_INC notes. See e.g. PR25196,
where a pushsi2 on i386 doesn't have REG_INC notes. Note
such changes here too. */
if (! push_operand (dest, GET_MODE (dest)))
record_last_mem_set_info (last_set_insn);
else
record_last_reg_set_info_regno (last_set_insn, STACK_POINTER_REGNUM);
}
}
/* Reset tables used to keep track of what's still available since the
start of the block. */
static void
reset_opr_set_tables (void)
{
memset (reg_avail_info, 0, FIRST_PSEUDO_REGISTER * sizeof (int));
obstack_free (&modifies_mem_obstack, modifies_mem_obstack_bottom);
modifies_mem_list = NULL;
}
/* Record things set by INSN.
This data is used by oprs_unchanged_p. */
static void
record_opr_changes (rtx insn)
{
rtx note;
/* Find all stores and record them. */
note_stores (PATTERN (insn), record_last_set_info, insn);
/* Also record autoincremented REGs for this insn as changed. */
for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
if (REG_NOTE_KIND (note) == REG_INC)
record_last_reg_set_info (insn, XEXP (note, 0));
/* Finally, if this is a call, record all call clobbers. */
if (CALL_P (insn))
{
unsigned int regno;
rtx link, x;
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
if (TEST_HARD_REG_BIT (regs_invalidated_by_call, regno))
record_last_reg_set_info_regno (insn, regno);
for (link = CALL_INSN_FUNCTION_USAGE (insn); link; link = XEXP (link, 1))
if (GET_CODE (XEXP (link, 0)) == CLOBBER)
{
x = XEXP (XEXP (link, 0), 0);
if (REG_P (x))
{
gcc_assert (HARD_REGISTER_P (x));
record_last_reg_set_info (insn, x);
}
}
if (! RTL_CONST_OR_PURE_CALL_P (insn))
record_last_mem_set_info (insn);
}
}
/* Scan the pattern of INSN and add an entry to the hash TABLE.
After reload we are interested in loads/stores only. */
static void
hash_scan_set (rtx insn)
{
rtx pat = PATTERN (insn);
rtx src = SET_SRC (pat);
rtx dest = SET_DEST (pat);
/* We are only interested in loads and stores. */
if (! MEM_P (src) && ! MEM_P (dest))
return;
/* Don't mess with jumps and nops. */
if (JUMP_P (insn) || set_noop_p (pat))
return;
if (REG_P (dest))
{
if (/* Don't CSE something if we can't do a reg/reg copy. */
can_copy_p (GET_MODE (dest))
/* Is SET_SRC something we want to gcse? */
&& general_operand (src, GET_MODE (src))
#ifdef STACK_REGS
/* Never consider insns touching the register stack. It may
create situations that reg-stack cannot handle (e.g. a stack
register live across an abnormal edge). */
&& (REGNO (dest) < FIRST_STACK_REG || REGNO (dest) > LAST_STACK_REG)
#endif
/* An expression is not available if its operands are
subsequently modified, including this insn. */
&& oprs_unchanged_p (src, insn, true))
{
insert_expr_in_table (src, insn);
}
}
else if (REG_P (src))
{
/* Only record sets of pseudo-regs in the hash table. */
if (/* Don't CSE something if we can't do a reg/reg copy. */
can_copy_p (GET_MODE (src))
/* Is SET_DEST something we want to gcse? */
&& general_operand (dest, GET_MODE (dest))
#ifdef STACK_REGS
/* As above for STACK_REGS. */
&& (REGNO (src) < FIRST_STACK_REG || REGNO (src) > LAST_STACK_REG)
#endif
&& ! (flag_float_store && FLOAT_MODE_P (GET_MODE (dest)))
/* Check if the memory expression is killed after insn. */
&& ! load_killed_in_block_p (INSN_CUID (insn) + 1, dest, true)
&& oprs_unchanged_p (XEXP (dest, 0), insn, true))
{
insert_expr_in_table (dest, insn);
}
}
}
/* Create hash table of memory expressions available at end of basic
blocks. Basically you should think of this hash table as the
representation of AVAIL_OUT. This is the set of expressions that
is generated in a basic block and not killed before the end of the
same basic block. Notice that this is really a local computation. */
static void
compute_hash_table (void)
{
basic_block bb;
FOR_EACH_BB (bb)
{
rtx insn;
/* First pass over the instructions records information used to
determine when registers and memory are last set.
Since we compute a "local" AVAIL_OUT, reset the tables that
help us keep track of what has been modified since the start
of the block. */
reset_opr_set_tables ();
FOR_BB_INSNS (bb, insn)
{
if (INSN_P (insn))
record_opr_changes (insn);
}
/* The next pass actually builds the hash table. */
FOR_BB_INSNS (bb, insn)
if (INSN_P (insn) && GET_CODE (PATTERN (insn)) == SET)
hash_scan_set (insn);
}
}
/* Check if register REG is killed in any insn waiting to be inserted on
edge E. This function is required to check that our data flow analysis
is still valid prior to commit_edge_insertions. */
static bool
reg_killed_on_edge (rtx reg, edge e)
{
rtx insn;
for (insn = e->insns.r; insn; insn = NEXT_INSN (insn))
if (INSN_P (insn) && reg_set_p (reg, insn))
return true;
return false;
}
/* Similar to above - check if register REG is used in any insn waiting
to be inserted on edge E.
Assumes no such insn can be a CALL_INSN; if so call reg_used_between_p
with PREV(insn),NEXT(insn) instead of calling reg_overlap_mentioned_p. */
static bool
reg_used_on_edge (rtx reg, edge e)
{
rtx insn;
for (insn = e->insns.r; insn; insn = NEXT_INSN (insn))
if (INSN_P (insn) && reg_overlap_mentioned_p (reg, PATTERN (insn)))
return true;
return false;
}
/* Return the loaded/stored register of a load/store instruction. */
static rtx
get_avail_load_store_reg (rtx insn)
{
if (REG_P (SET_DEST (PATTERN (insn))))
/* A load. */
return SET_DEST(PATTERN(insn));
else
{
/* A store. */
gcc_assert (REG_P (SET_SRC (PATTERN (insn))));
return SET_SRC (PATTERN (insn));
}
}
/* Return nonzero if the predecessors of BB are "well behaved". */
static bool
bb_has_well_behaved_predecessors (basic_block bb)
{
edge pred;
edge_iterator ei;
if (EDGE_COUNT (bb->preds) == 0)
return false;
FOR_EACH_EDGE (pred, ei, bb->preds)
{
if ((pred->flags & EDGE_ABNORMAL) && EDGE_CRITICAL_P (pred))
return false;
if ((pred->flags & EDGE_ABNORMAL_CALL) && cfun->has_nonlocal_label)
return false;
if (JUMP_TABLE_DATA_P (BB_END (pred->src)))
return false;
}
return true;
}
/* Search for the occurrences of expression in BB. */
static struct occr*
get_bb_avail_insn (basic_block bb, struct occr *occr)
{
for (; occr != NULL; occr = occr->next)
if (BLOCK_FOR_INSN (occr->insn) == bb)
return occr;
return NULL;
}
/* This handles the case where several stores feed a partially redundant
load. It checks if the redundancy elimination is possible and if it's
worth it.
Redundancy elimination is possible if,
1) None of the operands of an insn have been modified since the start
of the current basic block.
2) In any predecessor of the current basic block, the same expression
is generated.
See the function body for the heuristics that determine if eliminating
a redundancy is also worth doing, assuming it is possible. */
static void
eliminate_partially_redundant_load (basic_block bb, rtx insn,
struct expr *expr)
{
edge pred;
rtx avail_insn = NULL_RTX;
rtx avail_reg;
rtx dest, pat;
struct occr *a_occr;
struct unoccr *occr, *avail_occrs = NULL;
struct unoccr *unoccr, *unavail_occrs = NULL, *rollback_unoccr = NULL;
int npred_ok = 0;
gcov_type ok_count = 0; /* Redundant load execution count. */
gcov_type critical_count = 0; /* Execution count of critical edges. */
edge_iterator ei;
bool critical_edge_split = false;
/* The execution count of the loads to be added to make the
load fully redundant. */
gcov_type not_ok_count = 0;
basic_block pred_bb;
pat = PATTERN (insn);
dest = SET_DEST (pat);
/* Check that the loaded register is not used, set, or killed from the
beginning of the block. */
if (reg_changed_after_insn_p (dest, 0)
|| reg_used_between_p (dest, PREV_INSN (BB_HEAD (bb)), insn))
return;
/* Check potential for replacing load with copy for predecessors. */
FOR_EACH_EDGE (pred, ei, bb->preds)
{
rtx next_pred_bb_end;
avail_insn = NULL_RTX;
avail_reg = NULL_RTX;
pred_bb = pred->src;
next_pred_bb_end = NEXT_INSN (BB_END (pred_bb));
for (a_occr = get_bb_avail_insn (pred_bb, expr->avail_occr); a_occr;
a_occr = get_bb_avail_insn (pred_bb, a_occr->next))
{
/* Check if the loaded register is not used. */
avail_insn = a_occr->insn;
avail_reg = get_avail_load_store_reg (avail_insn);
gcc_assert (avail_reg);
/* Make sure we can generate a move from register avail_reg to
dest. */
extract_insn (gen_move_insn (copy_rtx (dest),
copy_rtx (avail_reg)));
if (! constrain_operands (1)
|| reg_killed_on_edge (avail_reg, pred)
|| reg_used_on_edge (dest, pred))
{
avail_insn = NULL;
continue;
}
if (!reg_set_between_p (avail_reg, avail_insn, next_pred_bb_end))
/* AVAIL_INSN remains non-null. */
break;
else
avail_insn = NULL;
}
if (EDGE_CRITICAL_P (pred))
critical_count += pred->count;
if (avail_insn != NULL_RTX)
{
npred_ok++;
ok_count += pred->count;
if (! set_noop_p (PATTERN (gen_move_insn (copy_rtx (dest),
copy_rtx (avail_reg)))))
{
/* Check if there is going to be a split. */
if (EDGE_CRITICAL_P (pred))
critical_edge_split = true;
}
else /* Its a dead move no need to generate. */
continue;
occr = (struct unoccr *) obstack_alloc (&unoccr_obstack,
sizeof (struct unoccr));
occr->insn = avail_insn;
occr->pred = pred;
occr->next = avail_occrs;
avail_occrs = occr;
if (! rollback_unoccr)
rollback_unoccr = occr;
}
else
{
/* Adding a load on a critical edge will cause a split. */
if (EDGE_CRITICAL_P (pred))
critical_edge_split = true;
not_ok_count += pred->count;
unoccr = (struct unoccr *) obstack_alloc (&unoccr_obstack,
sizeof (struct unoccr));
unoccr->insn = NULL_RTX;
unoccr->pred = pred;
unoccr->next = unavail_occrs;
unavail_occrs = unoccr;
if (! rollback_unoccr)
rollback_unoccr = unoccr;
}
}
if (/* No load can be replaced by copy. */
npred_ok == 0
/* Prevent exploding the code. */
|| (optimize_bb_for_size_p (bb) && npred_ok > 1)
/* If we don't have profile information we cannot tell if splitting
a critical edge is profitable or not so don't do it. */
|| ((! profile_info || ! flag_branch_probabilities
|| targetm.cannot_modify_jumps_p ())
&& critical_edge_split))
goto cleanup;
/* Check if it's worth applying the partial redundancy elimination. */
if (ok_count < GCSE_AFTER_RELOAD_PARTIAL_FRACTION * not_ok_count)
goto cleanup;
if (ok_count < GCSE_AFTER_RELOAD_CRITICAL_FRACTION * critical_count)
goto cleanup;
/* Generate moves to the loaded register from where
the memory is available. */
for (occr = avail_occrs; occr; occr = occr->next)
{
avail_insn = occr->insn;
pred = occr->pred;
/* Set avail_reg to be the register having the value of the
memory. */
avail_reg = get_avail_load_store_reg (avail_insn);
gcc_assert (avail_reg);
insert_insn_on_edge (gen_move_insn (copy_rtx (dest),
copy_rtx (avail_reg)),
pred);
stats.moves_inserted++;
if (dump_file)
fprintf (dump_file,
"generating move from %d to %d on edge from %d to %d\n",
REGNO (avail_reg),
REGNO (dest),
pred->src->index,
pred->dest->index);
}
/* Regenerate loads where the memory is unavailable. */
for (unoccr = unavail_occrs; unoccr; unoccr = unoccr->next)
{
pred = unoccr->pred;
insert_insn_on_edge (copy_insn (PATTERN (insn)), pred);
stats.copies_inserted++;
if (dump_file)
{
fprintf (dump_file,
"generating on edge from %d to %d a copy of load: ",
pred->src->index,
pred->dest->index);
print_rtl (dump_file, PATTERN (insn));
fprintf (dump_file, "\n");
}
}
/* Delete the insn if it is not available in this block and mark it
for deletion if it is available. If insn is available it may help
discover additional redundancies, so mark it for later deletion. */
for (a_occr = get_bb_avail_insn (bb, expr->avail_occr);
a_occr && (a_occr->insn != insn);
a_occr = get_bb_avail_insn (bb, a_occr->next))
;
if (!a_occr)
{
stats.insns_deleted++;
if (dump_file)
{
fprintf (dump_file, "deleting insn:\n");
print_rtl_single (dump_file, insn);
fprintf (dump_file, "\n");
}
delete_insn (insn);
}
else
a_occr->deleted_p = 1;
cleanup:
if (rollback_unoccr)
obstack_free (&unoccr_obstack, rollback_unoccr);
}
/* Performing the redundancy elimination as described before. */
static void
eliminate_partially_redundant_loads (void)
{
rtx insn;
basic_block bb;
/* Note we start at block 1. */
if (ENTRY_BLOCK_PTR->next_bb == EXIT_BLOCK_PTR)
return;
FOR_BB_BETWEEN (bb,
ENTRY_BLOCK_PTR->next_bb->next_bb,
EXIT_BLOCK_PTR,
next_bb)
{
/* Don't try anything on basic blocks with strange predecessors. */
if (! bb_has_well_behaved_predecessors (bb))
continue;
/* Do not try anything on cold basic blocks. */
if (optimize_bb_for_size_p (bb))
continue;
/* Reset the table of things changed since the start of the current
basic block. */
reset_opr_set_tables ();
/* Look at all insns in the current basic block and see if there are
any loads in it that we can record. */
FOR_BB_INSNS (bb, insn)
{
/* Is it a load - of the form (set (reg) (mem))? */
if (NONJUMP_INSN_P (insn)
&& GET_CODE (PATTERN (insn)) == SET
&& REG_P (SET_DEST (PATTERN (insn)))
&& MEM_P (SET_SRC (PATTERN (insn))))
{
rtx pat = PATTERN (insn);
rtx src = SET_SRC (pat);
struct expr *expr;
if (!MEM_VOLATILE_P (src)
&& GET_MODE (src) != BLKmode
&& general_operand (src, GET_MODE (src))
/* Are the operands unchanged since the start of the
block? */
&& oprs_unchanged_p (src, insn, false)
&& !(cfun->can_throw_non_call_exceptions && may_trap_p (src))
&& !side_effects_p (src)
/* Is the expression recorded? */
&& (expr = lookup_expr_in_table (src)) != NULL)
{
/* We now have a load (insn) and an available memory at
its BB start (expr). Try to remove the loads if it is
redundant. */
eliminate_partially_redundant_load (bb, insn, expr);
}
}
/* Keep track of everything modified by this insn, so that we
know what has been modified since the start of the current
basic block. */
if (INSN_P (insn))
record_opr_changes (insn);
}
}
commit_edge_insertions ();
}
/* Go over the expression hash table and delete insns that were
marked for later deletion. */
/* This helper is called via htab_traverse. */
static int
delete_redundant_insns_1 (void **slot, void *data ATTRIBUTE_UNUSED)
{
struct expr *expr = (struct expr *) *slot;
struct occr *occr;
for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
{
if (occr->deleted_p && dbg_cnt (gcse2_delete))
{
delete_insn (occr->insn);
stats.insns_deleted++;
if (dump_file)
{
fprintf (dump_file, "deleting insn:\n");
print_rtl_single (dump_file, occr->insn);
fprintf (dump_file, "\n");
}
}
}
return 1;
}
static void
delete_redundant_insns (void)
{
htab_traverse (expr_table, delete_redundant_insns_1, NULL);
if (dump_file)
fprintf (dump_file, "\n");
}
/* Main entry point of the GCSE after reload - clean some redundant loads
due to spilling. */
static void
gcse_after_reload_main (rtx f ATTRIBUTE_UNUSED)
{
memset (&stats, 0, sizeof (stats));
/* Allocate memory for this pass.
Also computes and initializes the insns' CUIDs. */
alloc_mem ();
/* We need alias analysis. */
init_alias_analysis ();
compute_hash_table ();
if (dump_file)
dump_hash_table (dump_file);
if (htab_elements (expr_table) > 0)
{
eliminate_partially_redundant_loads ();
delete_redundant_insns ();
if (dump_file)
{
fprintf (dump_file, "GCSE AFTER RELOAD stats:\n");
fprintf (dump_file, "copies inserted: %d\n", stats.copies_inserted);
fprintf (dump_file, "moves inserted: %d\n", stats.moves_inserted);
fprintf (dump_file, "insns deleted: %d\n", stats.insns_deleted);
fprintf (dump_file, "\n\n");
}
statistics_counter_event (cfun, "copies inserted",
stats.copies_inserted);
statistics_counter_event (cfun, "moves inserted",
stats.moves_inserted);
statistics_counter_event (cfun, "insns deleted",
stats.insns_deleted);
}
/* We are finished with alias. */
end_alias_analysis ();
free_mem ();
}
static bool
gate_handle_gcse2 (void)
{
return (optimize > 0 && flag_gcse_after_reload
&& optimize_function_for_speed_p (cfun));
}
static unsigned int
rest_of_handle_gcse2 (void)
{
gcse_after_reload_main (get_insns ());
rebuild_jump_labels (get_insns ());
return 0;
}
struct rtl_opt_pass pass_gcse2 =
{
{
RTL_PASS,
"gcse2", /* name */
gate_handle_gcse2, /* gate */
rest_of_handle_gcse2, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_GCSE_AFTER_RELOAD, /* tv_id */
0, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_verify_rtl_sharing
| TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */
}
};
|