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
|
/* High-level loop manipulation functions.
Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010
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 "tree.h"
#include "tm_p.h"
#include "basic-block.h"
#include "output.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "timevar.h"
#include "cfgloop.h"
#include "tree-pass.h"
#include "tree-scalar-evolution.h"
#include "params.h"
#include "tree-inline.h"
#include "langhooks.h"
/* Creates an induction variable with value BASE + STEP * iteration in LOOP.
It is expected that neither BASE nor STEP are shared with other expressions
(unless the sharing rules allow this). Use VAR as a base var_decl for it
(if NULL, a new temporary will be created). The increment will occur at
INCR_POS (after it if AFTER is true, before it otherwise). INCR_POS and
AFTER can be computed using standard_iv_increment_position. The ssa versions
of the variable before and after increment will be stored in VAR_BEFORE and
VAR_AFTER (unless they are NULL). */
void
create_iv (tree base, tree step, tree var, struct loop *loop,
gimple_stmt_iterator *incr_pos, bool after,
tree *var_before, tree *var_after)
{
gimple stmt;
tree initial, step1;
gimple_seq stmts;
tree vb, va;
enum tree_code incr_op = PLUS_EXPR;
edge pe = loop_preheader_edge (loop);
if (!var)
{
var = create_tmp_var (TREE_TYPE (base), "ivtmp");
add_referenced_var (var);
}
vb = make_ssa_name (var, NULL);
if (var_before)
*var_before = vb;
va = make_ssa_name (var, NULL);
if (var_after)
*var_after = va;
/* For easier readability of the created code, produce MINUS_EXPRs
when suitable. */
if (TREE_CODE (step) == INTEGER_CST)
{
if (TYPE_UNSIGNED (TREE_TYPE (step)))
{
step1 = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
if (tree_int_cst_lt (step1, step))
{
incr_op = MINUS_EXPR;
step = step1;
}
}
else
{
bool ovf;
if (!tree_expr_nonnegative_warnv_p (step, &ovf)
&& may_negate_without_overflow_p (step))
{
incr_op = MINUS_EXPR;
step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
}
}
}
if (POINTER_TYPE_P (TREE_TYPE (base)))
{
if (TREE_CODE (base) == ADDR_EXPR)
mark_addressable (TREE_OPERAND (base, 0));
step = convert_to_ptrofftype (step);
if (incr_op == MINUS_EXPR)
step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
incr_op = POINTER_PLUS_EXPR;
}
/* Gimplify the step if necessary. We put the computations in front of the
loop (i.e. the step should be loop invariant). */
step = force_gimple_operand (step, &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (pe, stmts);
stmt = gimple_build_assign_with_ops (incr_op, va, vb, step);
if (after)
gsi_insert_after (incr_pos, stmt, GSI_NEW_STMT);
else
gsi_insert_before (incr_pos, stmt, GSI_NEW_STMT);
initial = force_gimple_operand (base, &stmts, true, var);
if (stmts)
gsi_insert_seq_on_edge_immediate (pe, stmts);
stmt = create_phi_node (vb, loop->header);
SSA_NAME_DEF_STMT (vb) = stmt;
add_phi_arg (stmt, initial, loop_preheader_edge (loop), UNKNOWN_LOCATION);
add_phi_arg (stmt, va, loop_latch_edge (loop), UNKNOWN_LOCATION);
}
/* Add exit phis for the USE on EXIT. */
static void
add_exit_phis_edge (basic_block exit, tree use)
{
gimple phi, def_stmt = SSA_NAME_DEF_STMT (use);
basic_block def_bb = gimple_bb (def_stmt);
struct loop *def_loop;
edge e;
edge_iterator ei;
/* Check that some of the edges entering the EXIT block exits a loop in
that USE is defined. */
FOR_EACH_EDGE (e, ei, exit->preds)
{
def_loop = find_common_loop (def_bb->loop_father, e->src->loop_father);
if (!flow_bb_inside_loop_p (def_loop, e->dest))
break;
}
if (!e)
return;
phi = create_phi_node (use, exit);
create_new_def_for (gimple_phi_result (phi), phi,
gimple_phi_result_ptr (phi));
FOR_EACH_EDGE (e, ei, exit->preds)
add_phi_arg (phi, use, e, UNKNOWN_LOCATION);
}
/* Add exit phis for VAR that is used in LIVEIN.
Exits of the loops are stored in EXITS. */
static void
add_exit_phis_var (tree var, bitmap livein, bitmap exits)
{
bitmap def;
unsigned index;
basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (var));
bitmap_iterator bi;
if (is_gimple_reg (var))
bitmap_clear_bit (livein, def_bb->index);
else
bitmap_set_bit (livein, def_bb->index);
def = BITMAP_ALLOC (NULL);
bitmap_set_bit (def, def_bb->index);
compute_global_livein (livein, def);
BITMAP_FREE (def);
EXECUTE_IF_AND_IN_BITMAP (exits, livein, 0, index, bi)
{
add_exit_phis_edge (BASIC_BLOCK (index), var);
}
}
/* Add exit phis for the names marked in NAMES_TO_RENAME.
Exits of the loops are stored in EXITS. Sets of blocks where the ssa
names are used are stored in USE_BLOCKS. */
static void
add_exit_phis (bitmap names_to_rename, bitmap *use_blocks, bitmap loop_exits)
{
unsigned i;
bitmap_iterator bi;
EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi)
{
add_exit_phis_var (ssa_name (i), use_blocks[i], loop_exits);
}
}
/* Returns a bitmap of all loop exit edge targets. */
static bitmap
get_loops_exits (void)
{
bitmap exits = BITMAP_ALLOC (NULL);
basic_block bb;
edge e;
edge_iterator ei;
FOR_EACH_BB (bb)
{
FOR_EACH_EDGE (e, ei, bb->preds)
if (e->src != ENTRY_BLOCK_PTR
&& !flow_bb_inside_loop_p (e->src->loop_father, bb))
{
bitmap_set_bit (exits, bb->index);
break;
}
}
return exits;
}
/* For USE in BB, if it is used outside of the loop it is defined in,
mark it for rewrite. Record basic block BB where it is used
to USE_BLOCKS. Record the ssa name index to NEED_PHIS bitmap. */
static void
find_uses_to_rename_use (basic_block bb, tree use, bitmap *use_blocks,
bitmap need_phis)
{
unsigned ver;
basic_block def_bb;
struct loop *def_loop;
if (TREE_CODE (use) != SSA_NAME)
return;
/* We don't need to keep virtual operands in loop-closed form. */
if (!is_gimple_reg (use))
return;
ver = SSA_NAME_VERSION (use);
def_bb = gimple_bb (SSA_NAME_DEF_STMT (use));
if (!def_bb)
return;
def_loop = def_bb->loop_father;
/* If the definition is not inside a loop, it is not interesting. */
if (!loop_outer (def_loop))
return;
/* If the use is not outside of the loop it is defined in, it is not
interesting. */
if (flow_bb_inside_loop_p (def_loop, bb))
return;
if (!use_blocks[ver])
use_blocks[ver] = BITMAP_ALLOC (NULL);
bitmap_set_bit (use_blocks[ver], bb->index);
bitmap_set_bit (need_phis, ver);
}
/* For uses in STMT, mark names that are used outside of the loop they are
defined to rewrite. Record the set of blocks in that the ssa
names are defined to USE_BLOCKS and the ssa names themselves to
NEED_PHIS. */
static void
find_uses_to_rename_stmt (gimple stmt, bitmap *use_blocks, bitmap need_phis)
{
ssa_op_iter iter;
tree var;
basic_block bb = gimple_bb (stmt);
if (is_gimple_debug (stmt))
return;
FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_ALL_USES)
find_uses_to_rename_use (bb, var, use_blocks, need_phis);
}
/* Marks names that are used in BB and outside of the loop they are
defined in for rewrite. Records the set of blocks in that the ssa
names are defined to USE_BLOCKS. Record the SSA names that will
need exit PHIs in NEED_PHIS. */
static void
find_uses_to_rename_bb (basic_block bb, bitmap *use_blocks, bitmap need_phis)
{
gimple_stmt_iterator bsi;
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
for (bsi = gsi_start_phis (e->dest); !gsi_end_p (bsi); gsi_next (&bsi))
find_uses_to_rename_use (bb, PHI_ARG_DEF_FROM_EDGE (gsi_stmt (bsi), e),
use_blocks, need_phis);
for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
find_uses_to_rename_stmt (gsi_stmt (bsi), use_blocks, need_phis);
}
/* Marks names that are used outside of the loop they are defined in
for rewrite. Records the set of blocks in that the ssa
names are defined to USE_BLOCKS. If CHANGED_BBS is not NULL,
scan only blocks in this set. */
static void
find_uses_to_rename (bitmap changed_bbs, bitmap *use_blocks, bitmap need_phis)
{
basic_block bb;
unsigned index;
bitmap_iterator bi;
if (changed_bbs && !bitmap_empty_p (changed_bbs))
{
EXECUTE_IF_SET_IN_BITMAP (changed_bbs, 0, index, bi)
{
find_uses_to_rename_bb (BASIC_BLOCK (index), use_blocks, need_phis);
}
}
else
{
FOR_EACH_BB (bb)
{
find_uses_to_rename_bb (bb, use_blocks, need_phis);
}
}
}
/* Rewrites the program into a loop closed ssa form -- i.e. inserts extra
phi nodes to ensure that no variable is used outside the loop it is
defined in.
This strengthening of the basic ssa form has several advantages:
1) Updating it during unrolling/peeling/versioning is trivial, since
we do not need to care about the uses outside of the loop.
2) The behavior of all uses of an induction variable is the same.
Without this, you need to distinguish the case when the variable
is used outside of the loop it is defined in, for example
for (i = 0; i < 100; i++)
{
for (j = 0; j < 100; j++)
{
k = i + j;
use1 (k);
}
use2 (k);
}
Looking from the outer loop with the normal SSA form, the first use of k
is not well-behaved, while the second one is an induction variable with
base 99 and step 1.
If CHANGED_BBS is not NULL, we look for uses outside loops only in
the basic blocks in this set.
UPDATE_FLAG is used in the call to update_ssa. See
TODO_update_ssa* for documentation. */
void
rewrite_into_loop_closed_ssa (bitmap changed_bbs, unsigned update_flag)
{
bitmap loop_exits;
bitmap *use_blocks;
unsigned i, old_num_ssa_names;
bitmap names_to_rename;
loops_state_set (LOOP_CLOSED_SSA);
if (number_of_loops () <= 1)
return;
loop_exits = get_loops_exits ();
names_to_rename = BITMAP_ALLOC (NULL);
/* If the pass has caused the SSA form to be out-of-date, update it
now. */
update_ssa (update_flag);
old_num_ssa_names = num_ssa_names;
use_blocks = XCNEWVEC (bitmap, old_num_ssa_names);
/* Find the uses outside loops. */
find_uses_to_rename (changed_bbs, use_blocks, names_to_rename);
/* Add the PHI nodes on exits of the loops for the names we need to
rewrite. */
add_exit_phis (names_to_rename, use_blocks, loop_exits);
for (i = 0; i < old_num_ssa_names; i++)
BITMAP_FREE (use_blocks[i]);
free (use_blocks);
BITMAP_FREE (loop_exits);
BITMAP_FREE (names_to_rename);
/* Fix up all the names found to be used outside their original
loops. */
update_ssa (TODO_update_ssa);
}
/* Check invariants of the loop closed ssa form for the USE in BB. */
static void
check_loop_closed_ssa_use (basic_block bb, tree use)
{
gimple def;
basic_block def_bb;
if (TREE_CODE (use) != SSA_NAME || !is_gimple_reg (use))
return;
def = SSA_NAME_DEF_STMT (use);
def_bb = gimple_bb (def);
gcc_assert (!def_bb
|| flow_bb_inside_loop_p (def_bb->loop_father, bb));
}
/* Checks invariants of loop closed ssa form in statement STMT in BB. */
static void
check_loop_closed_ssa_stmt (basic_block bb, gimple stmt)
{
ssa_op_iter iter;
tree var;
if (is_gimple_debug (stmt))
return;
FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_ALL_USES)
check_loop_closed_ssa_use (bb, var);
}
/* Checks that invariants of the loop closed ssa form are preserved.
Call verify_ssa when VERIFY_SSA_P is true. */
DEBUG_FUNCTION void
verify_loop_closed_ssa (bool verify_ssa_p)
{
basic_block bb;
gimple_stmt_iterator bsi;
gimple phi;
edge e;
edge_iterator ei;
if (number_of_loops () <= 1)
return;
if (verify_ssa_p)
verify_ssa (false);
timevar_push (TV_VERIFY_LOOP_CLOSED);
FOR_EACH_BB (bb)
{
for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
{
phi = gsi_stmt (bsi);
FOR_EACH_EDGE (e, ei, bb->preds)
check_loop_closed_ssa_use (e->src,
PHI_ARG_DEF_FROM_EDGE (phi, e));
}
for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
check_loop_closed_ssa_stmt (bb, gsi_stmt (bsi));
}
timevar_pop (TV_VERIFY_LOOP_CLOSED);
}
/* Split loop exit edge EXIT. The things are a bit complicated by a need to
preserve the loop closed ssa form. The newly created block is returned. */
basic_block
split_loop_exit_edge (edge exit)
{
basic_block dest = exit->dest;
basic_block bb = split_edge (exit);
gimple phi, new_phi;
tree new_name, name;
use_operand_p op_p;
gimple_stmt_iterator psi;
source_location locus;
for (psi = gsi_start_phis (dest); !gsi_end_p (psi); gsi_next (&psi))
{
phi = gsi_stmt (psi);
op_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, single_succ_edge (bb));
locus = gimple_phi_arg_location_from_edge (phi, single_succ_edge (bb));
name = USE_FROM_PTR (op_p);
/* If the argument of the PHI node is a constant, we do not need
to keep it inside loop. */
if (TREE_CODE (name) != SSA_NAME)
continue;
/* Otherwise create an auxiliary phi node that will copy the value
of the SSA name out of the loop. */
new_name = duplicate_ssa_name (name, NULL);
new_phi = create_phi_node (new_name, bb);
SSA_NAME_DEF_STMT (new_name) = new_phi;
add_phi_arg (new_phi, name, exit, locus);
SET_USE (op_p, new_name);
}
return bb;
}
/* Returns the basic block in that statements should be emitted for induction
variables incremented at the end of the LOOP. */
basic_block
ip_end_pos (struct loop *loop)
{
return loop->latch;
}
/* Returns the basic block in that statements should be emitted for induction
variables incremented just before exit condition of a LOOP. */
basic_block
ip_normal_pos (struct loop *loop)
{
gimple last;
basic_block bb;
edge exit;
if (!single_pred_p (loop->latch))
return NULL;
bb = single_pred (loop->latch);
last = last_stmt (bb);
if (!last
|| gimple_code (last) != GIMPLE_COND)
return NULL;
exit = EDGE_SUCC (bb, 0);
if (exit->dest == loop->latch)
exit = EDGE_SUCC (bb, 1);
if (flow_bb_inside_loop_p (loop, exit->dest))
return NULL;
return bb;
}
/* Stores the standard position for induction variable increment in LOOP
(just before the exit condition if it is available and latch block is empty,
end of the latch block otherwise) to BSI. INSERT_AFTER is set to true if
the increment should be inserted after *BSI. */
void
standard_iv_increment_position (struct loop *loop, gimple_stmt_iterator *bsi,
bool *insert_after)
{
basic_block bb = ip_normal_pos (loop), latch = ip_end_pos (loop);
gimple last = last_stmt (latch);
if (!bb
|| (last && gimple_code (last) != GIMPLE_LABEL))
{
*bsi = gsi_last_bb (latch);
*insert_after = true;
}
else
{
*bsi = gsi_last_bb (bb);
*insert_after = false;
}
}
/* Copies phi node arguments for duplicated blocks. The index of the first
duplicated block is FIRST_NEW_BLOCK. */
static void
copy_phi_node_args (unsigned first_new_block)
{
unsigned i;
for (i = first_new_block; i < (unsigned) last_basic_block; i++)
BASIC_BLOCK (i)->flags |= BB_DUPLICATED;
for (i = first_new_block; i < (unsigned) last_basic_block; i++)
add_phi_args_after_copy_bb (BASIC_BLOCK (i));
for (i = first_new_block; i < (unsigned) last_basic_block; i++)
BASIC_BLOCK (i)->flags &= ~BB_DUPLICATED;
}
/* The same as cfgloopmanip.c:duplicate_loop_to_header_edge, but also
updates the PHI nodes at start of the copied region. In order to
achieve this, only loops whose exits all lead to the same location
are handled.
Notice that we do not completely update the SSA web after
duplication. The caller is responsible for calling update_ssa
after the loop has been duplicated. */
bool
gimple_duplicate_loop_to_header_edge (struct loop *loop, edge e,
unsigned int ndupl, sbitmap wont_exit,
edge orig, VEC (edge, heap) **to_remove,
int flags)
{
unsigned first_new_block;
if (!loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
return false;
if (!loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS))
return false;
#ifdef ENABLE_CHECKING
if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
verify_loop_closed_ssa (true);
#endif
first_new_block = last_basic_block;
if (!duplicate_loop_to_header_edge (loop, e, ndupl, wont_exit,
orig, to_remove, flags))
return false;
/* Readd the removed phi args for e. */
flush_pending_stmts (e);
/* Copy the phi node arguments. */
copy_phi_node_args (first_new_block);
scev_reset ();
return true;
}
/* Returns true if we can unroll LOOP FACTOR times. Number
of iterations of the loop is returned in NITER. */
bool
can_unroll_loop_p (struct loop *loop, unsigned factor,
struct tree_niter_desc *niter)
{
edge exit;
/* Check whether unrolling is possible. We only want to unroll loops
for that we are able to determine number of iterations. We also
want to split the extra iterations of the loop from its end,
therefore we require that the loop has precisely one
exit. */
exit = single_dom_exit (loop);
if (!exit)
return false;
if (!number_of_iterations_exit (loop, exit, niter, false)
|| niter->cmp == ERROR_MARK
/* Scalar evolutions analysis might have copy propagated
the abnormal ssa names into these expressions, hence
emitting the computations based on them during loop
unrolling might create overlapping life ranges for
them, and failures in out-of-ssa. */
|| contains_abnormal_ssa_name_p (niter->may_be_zero)
|| contains_abnormal_ssa_name_p (niter->control.base)
|| contains_abnormal_ssa_name_p (niter->control.step)
|| contains_abnormal_ssa_name_p (niter->bound))
return false;
/* And of course, we must be able to duplicate the loop. */
if (!can_duplicate_loop_p (loop))
return false;
/* The final loop should be small enough. */
if (tree_num_loop_insns (loop, &eni_size_weights) * factor
> (unsigned) PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS))
return false;
return true;
}
/* Determines the conditions that control execution of LOOP unrolled FACTOR
times. DESC is number of iterations of LOOP. ENTER_COND is set to
condition that must be true if the main loop can be entered.
EXIT_BASE, EXIT_STEP, EXIT_CMP and EXIT_BOUND are set to values describing
how the exit from the unrolled loop should be controlled. */
static void
determine_exit_conditions (struct loop *loop, struct tree_niter_desc *desc,
unsigned factor, tree *enter_cond,
tree *exit_base, tree *exit_step,
enum tree_code *exit_cmp, tree *exit_bound)
{
gimple_seq stmts;
tree base = desc->control.base;
tree step = desc->control.step;
tree bound = desc->bound;
tree type = TREE_TYPE (step);
tree bigstep, delta;
tree min = lower_bound_in_type (type, type);
tree max = upper_bound_in_type (type, type);
enum tree_code cmp = desc->cmp;
tree cond = boolean_true_node, assum;
/* For pointers, do the arithmetics in the type of step. */
base = fold_convert (type, base);
bound = fold_convert (type, bound);
*enter_cond = boolean_false_node;
*exit_base = NULL_TREE;
*exit_step = NULL_TREE;
*exit_cmp = ERROR_MARK;
*exit_bound = NULL_TREE;
gcc_assert (cmp != ERROR_MARK);
/* We only need to be correct when we answer question
"Do at least FACTOR more iterations remain?" in the unrolled loop.
Thus, transforming BASE + STEP * i <> BOUND to
BASE + STEP * i < BOUND is ok. */
if (cmp == NE_EXPR)
{
if (tree_int_cst_sign_bit (step))
cmp = GT_EXPR;
else
cmp = LT_EXPR;
}
else if (cmp == LT_EXPR)
{
gcc_assert (!tree_int_cst_sign_bit (step));
}
else if (cmp == GT_EXPR)
{
gcc_assert (tree_int_cst_sign_bit (step));
}
else
gcc_unreachable ();
/* The main body of the loop may be entered iff:
1) desc->may_be_zero is false.
2) it is possible to check that there are at least FACTOR iterations
of the loop, i.e., BOUND - step * FACTOR does not overflow.
3) # of iterations is at least FACTOR */
if (!integer_zerop (desc->may_be_zero))
cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
invert_truthvalue (desc->may_be_zero),
cond);
bigstep = fold_build2 (MULT_EXPR, type, step,
build_int_cst_type (type, factor));
delta = fold_build2 (MINUS_EXPR, type, bigstep, step);
if (cmp == LT_EXPR)
assum = fold_build2 (GE_EXPR, boolean_type_node,
bound,
fold_build2 (PLUS_EXPR, type, min, delta));
else
assum = fold_build2 (LE_EXPR, boolean_type_node,
bound,
fold_build2 (PLUS_EXPR, type, max, delta));
cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
bound = fold_build2 (MINUS_EXPR, type, bound, delta);
assum = fold_build2 (cmp, boolean_type_node, base, bound);
cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
cond = force_gimple_operand (unshare_expr (cond), &stmts, false, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
/* cond now may be a gimple comparison, which would be OK, but also any
other gimple rhs (say a && b). In this case we need to force it to
operand. */
if (!is_gimple_condexpr (cond))
{
cond = force_gimple_operand (cond, &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
}
*enter_cond = cond;
base = force_gimple_operand (unshare_expr (base), &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
bound = force_gimple_operand (unshare_expr (bound), &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
*exit_base = base;
*exit_step = bigstep;
*exit_cmp = cmp;
*exit_bound = bound;
}
/* Scales the frequencies of all basic blocks in LOOP that are strictly
dominated by BB by NUM/DEN. */
static void
scale_dominated_blocks_in_loop (struct loop *loop, basic_block bb,
int num, int den)
{
basic_block son;
if (den == 0)
return;
for (son = first_dom_son (CDI_DOMINATORS, bb);
son;
son = next_dom_son (CDI_DOMINATORS, son))
{
if (!flow_bb_inside_loop_p (loop, son))
continue;
scale_bbs_frequencies_int (&son, 1, num, den);
scale_dominated_blocks_in_loop (loop, son, num, den);
}
}
/* Unroll LOOP FACTOR times. DESC describes number of iterations of LOOP.
EXIT is the exit of the loop to that DESC corresponds.
If N is number of iterations of the loop and MAY_BE_ZERO is the condition
under that loop exits in the first iteration even if N != 0,
while (1)
{
x = phi (init, next);
pre;
if (st)
break;
post;
}
becomes (with possibly the exit conditions formulated a bit differently,
avoiding the need to create a new iv):
if (MAY_BE_ZERO || N < FACTOR)
goto rest;
do
{
x = phi (init, next);
pre;
post;
pre;
post;
...
pre;
post;
N -= FACTOR;
} while (N >= FACTOR);
rest:
init' = phi (init, x);
while (1)
{
x = phi (init', next);
pre;
if (st)
break;
post;
}
Before the loop is unrolled, TRANSFORM is called for it (only for the
unrolled loop, but not for its versioned copy). DATA is passed to
TRANSFORM. */
/* Probability in % that the unrolled loop is entered. Just a guess. */
#define PROB_UNROLLED_LOOP_ENTERED 90
void
tree_transform_and_unroll_loop (struct loop *loop, unsigned factor,
edge exit, struct tree_niter_desc *desc,
transform_callback transform,
void *data)
{
gimple exit_if;
tree ctr_before, ctr_after;
tree enter_main_cond, exit_base, exit_step, exit_bound;
enum tree_code exit_cmp;
gimple phi_old_loop, phi_new_loop, phi_rest;
gimple_stmt_iterator psi_old_loop, psi_new_loop;
tree init, next, new_init, var;
struct loop *new_loop;
basic_block rest, exit_bb;
edge old_entry, new_entry, old_latch, precond_edge, new_exit;
edge new_nonexit, e;
gimple_stmt_iterator bsi;
use_operand_p op;
bool ok;
unsigned est_niter, prob_entry, scale_unrolled, scale_rest, freq_e, freq_h;
unsigned new_est_niter, i, prob;
unsigned irr = loop_preheader_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP;
sbitmap wont_exit;
VEC (edge, heap) *to_remove = NULL;
est_niter = expected_loop_iterations (loop);
determine_exit_conditions (loop, desc, factor,
&enter_main_cond, &exit_base, &exit_step,
&exit_cmp, &exit_bound);
/* Let us assume that the unrolled loop is quite likely to be entered. */
if (integer_nonzerop (enter_main_cond))
prob_entry = REG_BR_PROB_BASE;
else
prob_entry = PROB_UNROLLED_LOOP_ENTERED * REG_BR_PROB_BASE / 100;
/* The values for scales should keep profile consistent, and somewhat close
to correct.
TODO: The current value of SCALE_REST makes it appear that the loop that
is created by splitting the remaining iterations of the unrolled loop is
executed the same number of times as the original loop, and with the same
frequencies, which is obviously wrong. This does not appear to cause
problems, so we do not bother with fixing it for now. To make the profile
correct, we would need to change the probability of the exit edge of the
loop, and recompute the distribution of frequencies in its body because
of this change (scale the frequencies of blocks before and after the exit
by appropriate factors). */
scale_unrolled = prob_entry;
scale_rest = REG_BR_PROB_BASE;
new_loop = loop_version (loop, enter_main_cond, NULL,
prob_entry, scale_unrolled, scale_rest, true);
gcc_assert (new_loop != NULL);
update_ssa (TODO_update_ssa);
/* Determine the probability of the exit edge of the unrolled loop. */
new_est_niter = est_niter / factor;
/* Without profile feedback, loops for that we do not know a better estimate
are assumed to roll 10 times. When we unroll such loop, it appears to
roll too little, and it may even seem to be cold. To avoid this, we
ensure that the created loop appears to roll at least 5 times (but at
most as many times as before unrolling). */
if (new_est_niter < 5)
{
if (est_niter < 5)
new_est_niter = est_niter;
else
new_est_niter = 5;
}
/* Prepare the cfg and update the phi nodes. Move the loop exit to the
loop latch (and make its condition dummy, for the moment). */
rest = loop_preheader_edge (new_loop)->src;
precond_edge = single_pred_edge (rest);
split_edge (loop_latch_edge (loop));
exit_bb = single_pred (loop->latch);
/* Since the exit edge will be removed, the frequency of all the blocks
in the loop that are dominated by it must be scaled by
1 / (1 - exit->probability). */
scale_dominated_blocks_in_loop (loop, exit->src,
REG_BR_PROB_BASE,
REG_BR_PROB_BASE - exit->probability);
bsi = gsi_last_bb (exit_bb);
exit_if = gimple_build_cond (EQ_EXPR, integer_zero_node,
integer_zero_node,
NULL_TREE, NULL_TREE);
gsi_insert_after (&bsi, exit_if, GSI_NEW_STMT);
new_exit = make_edge (exit_bb, rest, EDGE_FALSE_VALUE | irr);
rescan_loop_exit (new_exit, true, false);
/* Set the probability of new exit to the same of the old one. Fix
the frequency of the latch block, by scaling it back by
1 - exit->probability. */
new_exit->count = exit->count;
new_exit->probability = exit->probability;
new_nonexit = single_pred_edge (loop->latch);
new_nonexit->probability = REG_BR_PROB_BASE - exit->probability;
new_nonexit->flags = EDGE_TRUE_VALUE;
new_nonexit->count -= exit->count;
if (new_nonexit->count < 0)
new_nonexit->count = 0;
scale_bbs_frequencies_int (&loop->latch, 1, new_nonexit->probability,
REG_BR_PROB_BASE);
old_entry = loop_preheader_edge (loop);
new_entry = loop_preheader_edge (new_loop);
old_latch = loop_latch_edge (loop);
for (psi_old_loop = gsi_start_phis (loop->header),
psi_new_loop = gsi_start_phis (new_loop->header);
!gsi_end_p (psi_old_loop);
gsi_next (&psi_old_loop), gsi_next (&psi_new_loop))
{
phi_old_loop = gsi_stmt (psi_old_loop);
phi_new_loop = gsi_stmt (psi_new_loop);
init = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_entry);
op = PHI_ARG_DEF_PTR_FROM_EDGE (phi_new_loop, new_entry);
gcc_assert (operand_equal_for_phi_arg_p (init, USE_FROM_PTR (op)));
next = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_latch);
/* Prefer using original variable as a base for the new ssa name.
This is necessary for virtual ops, and useful in order to avoid
losing debug info for real ops. */
if (TREE_CODE (next) == SSA_NAME
&& useless_type_conversion_p (TREE_TYPE (next),
TREE_TYPE (init)))
var = SSA_NAME_VAR (next);
else if (TREE_CODE (init) == SSA_NAME
&& useless_type_conversion_p (TREE_TYPE (init),
TREE_TYPE (next)))
var = SSA_NAME_VAR (init);
else if (useless_type_conversion_p (TREE_TYPE (next), TREE_TYPE (init)))
{
var = create_tmp_var (TREE_TYPE (next), "unrinittmp");
add_referenced_var (var);
}
else
{
var = create_tmp_var (TREE_TYPE (init), "unrinittmp");
add_referenced_var (var);
}
new_init = make_ssa_name (var, NULL);
phi_rest = create_phi_node (new_init, rest);
SSA_NAME_DEF_STMT (new_init) = phi_rest;
add_phi_arg (phi_rest, init, precond_edge, UNKNOWN_LOCATION);
add_phi_arg (phi_rest, next, new_exit, UNKNOWN_LOCATION);
SET_USE (op, new_init);
}
remove_path (exit);
/* Transform the loop. */
if (transform)
(*transform) (loop, data);
/* Unroll the loop and remove the exits in all iterations except for the
last one. */
wont_exit = sbitmap_alloc (factor);
sbitmap_ones (wont_exit);
RESET_BIT (wont_exit, factor - 1);
ok = gimple_duplicate_loop_to_header_edge
(loop, loop_latch_edge (loop), factor - 1,
wont_exit, new_exit, &to_remove, DLTHE_FLAG_UPDATE_FREQ);
free (wont_exit);
gcc_assert (ok);
FOR_EACH_VEC_ELT (edge, to_remove, i, e)
{
ok = remove_path (e);
gcc_assert (ok);
}
VEC_free (edge, heap, to_remove);
update_ssa (TODO_update_ssa);
/* Ensure that the frequencies in the loop match the new estimated
number of iterations, and change the probability of the new
exit edge. */
freq_h = loop->header->frequency;
freq_e = EDGE_FREQUENCY (loop_preheader_edge (loop));
if (freq_h != 0)
scale_loop_frequencies (loop, freq_e * (new_est_niter + 1), freq_h);
exit_bb = single_pred (loop->latch);
new_exit = find_edge (exit_bb, rest);
new_exit->count = loop_preheader_edge (loop)->count;
new_exit->probability = REG_BR_PROB_BASE / (new_est_niter + 1);
rest->count += new_exit->count;
rest->frequency += EDGE_FREQUENCY (new_exit);
new_nonexit = single_pred_edge (loop->latch);
prob = new_nonexit->probability;
new_nonexit->probability = REG_BR_PROB_BASE - new_exit->probability;
new_nonexit->count = exit_bb->count - new_exit->count;
if (new_nonexit->count < 0)
new_nonexit->count = 0;
if (prob > 0)
scale_bbs_frequencies_int (&loop->latch, 1, new_nonexit->probability,
prob);
/* Finally create the new counter for number of iterations and add the new
exit instruction. */
bsi = gsi_last_nondebug_bb (exit_bb);
exit_if = gsi_stmt (bsi);
create_iv (exit_base, exit_step, NULL_TREE, loop,
&bsi, false, &ctr_before, &ctr_after);
gimple_cond_set_code (exit_if, exit_cmp);
gimple_cond_set_lhs (exit_if, ctr_after);
gimple_cond_set_rhs (exit_if, exit_bound);
update_stmt (exit_if);
#ifdef ENABLE_CHECKING
verify_flow_info ();
verify_loop_structure ();
verify_loop_closed_ssa (true);
#endif
}
/* Wrapper over tree_transform_and_unroll_loop for case we do not
want to transform the loop before unrolling. The meaning
of the arguments is the same as for tree_transform_and_unroll_loop. */
void
tree_unroll_loop (struct loop *loop, unsigned factor,
edge exit, struct tree_niter_desc *desc)
{
tree_transform_and_unroll_loop (loop, factor, exit, desc,
NULL, NULL);
}
/* Rewrite the phi node at position PSI in function of the main
induction variable MAIN_IV and insert the generated code at GSI. */
static void
rewrite_phi_with_iv (loop_p loop,
gimple_stmt_iterator *psi,
gimple_stmt_iterator *gsi,
tree main_iv)
{
affine_iv iv;
gimple stmt, phi = gsi_stmt (*psi);
tree atype, mtype, val, res = PHI_RESULT (phi);
if (!is_gimple_reg (res) || res == main_iv)
{
gsi_next (psi);
return;
}
if (!simple_iv (loop, loop, res, &iv, true))
{
gsi_next (psi);
return;
}
remove_phi_node (psi, false);
atype = TREE_TYPE (res);
mtype = POINTER_TYPE_P (atype) ? sizetype : atype;
val = fold_build2 (MULT_EXPR, mtype, unshare_expr (iv.step),
fold_convert (mtype, main_iv));
val = fold_build2 (POINTER_TYPE_P (atype)
? POINTER_PLUS_EXPR : PLUS_EXPR,
atype, unshare_expr (iv.base), val);
val = force_gimple_operand_gsi (gsi, val, false, NULL_TREE, true,
GSI_SAME_STMT);
stmt = gimple_build_assign (res, val);
gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
SSA_NAME_DEF_STMT (res) = stmt;
}
/* Rewrite all the phi nodes of LOOP in function of the main induction
variable MAIN_IV. */
static void
rewrite_all_phi_nodes_with_iv (loop_p loop, tree main_iv)
{
unsigned i;
basic_block *bbs = get_loop_body_in_dom_order (loop);
gimple_stmt_iterator psi;
for (i = 0; i < loop->num_nodes; i++)
{
basic_block bb = bbs[i];
gimple_stmt_iterator gsi = gsi_after_labels (bb);
if (bb->loop_father != loop)
continue;
for (psi = gsi_start_phis (bb); !gsi_end_p (psi); )
rewrite_phi_with_iv (loop, &psi, &gsi, main_iv);
}
free (bbs);
}
/* Bases all the induction variables in LOOP on a single induction
variable (unsigned with base 0 and step 1), whose final value is
compared with *NIT. When the IV type precision has to be larger
than *NIT type precision, *NIT is converted to the larger type, the
conversion code is inserted before the loop, and *NIT is updated to
the new definition. When BUMP_IN_LATCH is true, the induction
variable is incremented in the loop latch, otherwise it is
incremented in the loop header. Return the induction variable that
was created. */
tree
canonicalize_loop_ivs (struct loop *loop, tree *nit, bool bump_in_latch)
{
unsigned precision = TYPE_PRECISION (TREE_TYPE (*nit));
unsigned original_precision = precision;
tree type, var_before;
gimple_stmt_iterator gsi, psi;
gimple stmt;
edge exit = single_dom_exit (loop);
gimple_seq stmts;
enum machine_mode mode;
bool unsigned_p = false;
for (psi = gsi_start_phis (loop->header);
!gsi_end_p (psi); gsi_next (&psi))
{
gimple phi = gsi_stmt (psi);
tree res = PHI_RESULT (phi);
bool uns;
type = TREE_TYPE (res);
if (!is_gimple_reg (res)
|| (!INTEGRAL_TYPE_P (type)
&& !POINTER_TYPE_P (type))
|| TYPE_PRECISION (type) < precision)
continue;
uns = POINTER_TYPE_P (type) | TYPE_UNSIGNED (type);
if (TYPE_PRECISION (type) > precision)
unsigned_p = uns;
else
unsigned_p |= uns;
precision = TYPE_PRECISION (type);
}
mode = smallest_mode_for_size (precision, MODE_INT);
precision = GET_MODE_PRECISION (mode);
type = build_nonstandard_integer_type (precision, unsigned_p);
if (original_precision != precision)
{
*nit = fold_convert (type, *nit);
*nit = force_gimple_operand (*nit, &stmts, true, NULL_TREE);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
}
if (bump_in_latch)
gsi = gsi_last_bb (loop->latch);
else
gsi = gsi_last_nondebug_bb (loop->header);
create_iv (build_int_cst_type (type, 0), build_int_cst (type, 1), NULL_TREE,
loop, &gsi, bump_in_latch, &var_before, NULL);
rewrite_all_phi_nodes_with_iv (loop, var_before);
stmt = last_stmt (exit->src);
/* Make the loop exit if the control condition is not satisfied. */
if (exit->flags & EDGE_TRUE_VALUE)
{
edge te, fe;
extract_true_false_edges_from_block (exit->src, &te, &fe);
te->flags = EDGE_FALSE_VALUE;
fe->flags = EDGE_TRUE_VALUE;
}
gimple_cond_set_code (stmt, LT_EXPR);
gimple_cond_set_lhs (stmt, var_before);
gimple_cond_set_rhs (stmt, *nit);
update_stmt (stmt);
return var_before;
}
|