summaryrefslogtreecommitdiff
path: root/gcc/loop-init.c
blob: a9a3d6fa98af46c266e740f7b54fff5cdc380449 (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
/* Loop optimizer initialization routines and RTL loop optimization passes.
   Copyright (C) 2002-2015 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 "backend.h"
#include "cfghooks.h"
#include "tree.h"
#include "rtl.h"
#include "df.h"
#include "alias.h"
#include "regs.h"
#include "cfgcleanup.h"
#include "cfgloop.h"
#include "tree-pass.h"
#include "flags.h"
#include "tree-ssa-loop-niter.h"
#include "loop-unroll.h"
#include "tree-scalar-evolution.h"
#include "target.h"


/* Apply FLAGS to the loop state.  */

static void
apply_loop_flags (unsigned flags)
{
  if (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
    {
      /* If the loops may have multiple latches, we cannot canonicalize
	 them further (and most of the loop manipulation functions will
	 not work).  However, we avoid modifying cfg, which some
	 passes may want.  */
      gcc_assert ((flags & ~(LOOPS_MAY_HAVE_MULTIPLE_LATCHES
			     | LOOPS_HAVE_RECORDED_EXITS)) == 0);
      loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
    }
  else
    disambiguate_loops_with_multiple_latches ();

  /* Create pre-headers.  */
  if (flags & LOOPS_HAVE_PREHEADERS)
    {
      int cp_flags = CP_SIMPLE_PREHEADERS;

      if (flags & LOOPS_HAVE_FALLTHRU_PREHEADERS)
        cp_flags |= CP_FALLTHRU_PREHEADERS;

      create_preheaders (cp_flags);
    }

  /* Force all latches to have only single successor.  */
  if (flags & LOOPS_HAVE_SIMPLE_LATCHES)
    force_single_succ_latches ();

  /* Mark irreducible loops.  */
  if (flags & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
    mark_irreducible_loops ();

  if (flags & LOOPS_HAVE_RECORDED_EXITS)
    record_loop_exits ();
}

/* Initialize loop structures.  This is used by the tree and RTL loop
   optimizers.  FLAGS specify what properties to compute and/or ensure for
   loops.  */

void
loop_optimizer_init (unsigned flags)
{
  timevar_push (TV_LOOP_INIT);

  if (!current_loops)
    {
      gcc_assert (!(cfun->curr_properties & PROP_loops));

      /* Find the loops.  */
      current_loops = flow_loops_find (NULL);
    }
  else
    {
      bool recorded_exits = loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS);
      bool needs_fixup = loops_state_satisfies_p (LOOPS_NEED_FIXUP);

      gcc_assert (cfun->curr_properties & PROP_loops);

      /* Ensure that the dominators are computed, like flow_loops_find does.  */
      calculate_dominance_info (CDI_DOMINATORS);

#ifdef ENABLE_CHECKING
      if (!needs_fixup)
	verify_loop_structure ();
#endif

      /* Clear all flags.  */
      if (recorded_exits)
	release_recorded_exits ();
      loops_state_clear (~0U);

      if (needs_fixup)
	{
	  /* Apply LOOPS_MAY_HAVE_MULTIPLE_LATCHES early as fix_loop_structure
	     re-applies flags.  */
	  loops_state_set (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
	  fix_loop_structure (NULL);
	}
    }

  /* Apply flags to loops.  */
  apply_loop_flags (flags);

  /* Dump loops.  */
  flow_loops_dump (dump_file, NULL, 1);

#ifdef ENABLE_CHECKING
  verify_loop_structure ();
#endif

  timevar_pop (TV_LOOP_INIT);
}

/* Finalize loop structures.  */

void
loop_optimizer_finalize (void)
{
  struct loop *loop;
  basic_block bb;

  timevar_push (TV_LOOP_FINI);

  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
    release_recorded_exits ();

  free_numbers_of_iterations_estimates ();

  /* If we should preserve loop structure, do not free it but clear
     flags that advanced properties are there as we are not preserving
     that in full.  */
  if (cfun->curr_properties & PROP_loops)
    {
      loops_state_clear (LOOP_CLOSED_SSA
			 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
			 | LOOPS_HAVE_PREHEADERS
			 | LOOPS_HAVE_SIMPLE_LATCHES
			 | LOOPS_HAVE_FALLTHRU_PREHEADERS);
      loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
      goto loop_fini_done;
    }

  gcc_assert (current_loops != NULL);

  FOR_EACH_LOOP (loop, 0)
    free_simple_loop_desc (loop);

  /* Clean up.  */
  flow_loops_free (current_loops);
  ggc_free (current_loops);
  current_loops = NULL;

  FOR_ALL_BB_FN (bb, cfun)
    {
      bb->loop_father = NULL;
    }

loop_fini_done:
  timevar_pop (TV_LOOP_FINI);
}

/* The structure of loops might have changed.  Some loops might get removed
   (and their headers and latches were set to NULL), loop exists might get
   removed (thus the loop nesting may be wrong), and some blocks and edges
   were changed (so the information about bb --> loop mapping does not have
   to be correct).  But still for the remaining loops the header dominates
   the latch, and loops did not get new subloops (new loops might possibly
   get created, but we are not interested in them).  Fix up the mess.

   If CHANGED_BBS is not NULL, basic blocks whose loop depth has changed are
   marked in it.

   Returns the number of new discovered loops.  */

unsigned
fix_loop_structure (bitmap changed_bbs)
{
  basic_block bb;
  int record_exits = 0;
  struct loop *loop;
  unsigned old_nloops, i;

  timevar_push (TV_LOOP_INIT);

  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "fix_loop_structure: fixing up loops for function\n");

  /* We need exact and fast dominance info to be available.  */
  gcc_assert (dom_info_state (CDI_DOMINATORS) == DOM_OK);

  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
    {
      release_recorded_exits ();
      record_exits = LOOPS_HAVE_RECORDED_EXITS;
    }

  /* Remember the depth of the blocks in the loop hierarchy, so that we can
     recognize blocks whose loop nesting relationship has changed.  */
  if (changed_bbs)
    FOR_EACH_BB_FN (bb, cfun)
      bb->aux = (void *) (size_t) loop_depth (bb->loop_father);

  /* Remove the dead loops from structures.  We start from the innermost
     loops, so that when we remove the loops, we know that the loops inside
     are preserved, and do not waste time relinking loops that will be
     removed later.  */
  FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
    {
      /* Detect the case that the loop is no longer present even though
         it wasn't marked for removal.
	 ???  If we do that we can get away with not marking loops for
	 removal at all.  And possibly avoid some spurious removals.  */
      if (loop->header
	  && bb_loop_header_p (loop->header))
	continue;

      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "fix_loop_structure: removing loop %d\n",
		 loop->num);

      while (loop->inner)
	{
	  struct loop *ploop = loop->inner;
	  flow_loop_tree_node_remove (ploop);
	  flow_loop_tree_node_add (loop_outer (loop), ploop);
	}

      /* Remove the loop.  */
      if (loop->header)
	loop->former_header = loop->header;
      else
	gcc_assert (loop->former_header != NULL);
      loop->header = NULL;
      flow_loop_tree_node_remove (loop);
    }

  /* Remember the number of loops so we can return how many new loops
     flow_loops_find discovered.  */
  old_nloops = number_of_loops (cfun);

  /* Re-compute loop structure in-place.  */
  flow_loops_find (current_loops);

  /* Mark the blocks whose loop has changed.  */
  if (changed_bbs)
    {
      FOR_EACH_BB_FN (bb, cfun)
	{
	  if ((void *) (size_t) loop_depth (bb->loop_father) != bb->aux)
	    bitmap_set_bit (changed_bbs, bb->index);

    	  bb->aux = NULL;
	}
    }

  /* Finally free deleted loops.  */
  bool any_deleted = false;
  FOR_EACH_VEC_ELT (*get_loops (cfun), i, loop)
    if (loop && loop->header == NULL)
      {
	if (dump_file
	    && ((unsigned) loop->former_header->index
		< basic_block_info_for_fn (cfun)->length ()))
	  {
	    basic_block former_header
	      = BASIC_BLOCK_FOR_FN (cfun, loop->former_header->index);
	    /* If the old header still exists we want to check if the
	       original loop is re-discovered or the old header is now
	       part of a newly discovered loop.
	       In both cases we should have avoided removing the loop.  */
	    if (former_header == loop->former_header)
	      {
		if (former_header->loop_father->header == former_header)
		  fprintf (dump_file, "fix_loop_structure: rediscovered "
			   "removed loop %d as loop %d with old header %d\n",
			   loop->num, former_header->loop_father->num,
			   former_header->index);
		else if ((unsigned) former_header->loop_father->num
			 >= old_nloops)
		  fprintf (dump_file, "fix_loop_structure: header %d of "
			   "removed loop %d is part of the newly "
			   "discovered loop %d with header %d\n",
			   former_header->index, loop->num,
			   former_header->loop_father->num,
			   former_header->loop_father->header->index);
	      }
	  }
	(*get_loops (cfun))[i] = NULL;
	flow_loop_free (loop);
	any_deleted = true;
      }

  /* If we deleted loops then the cached scalar evolutions refering to
     those loops become invalid.  */
  if (any_deleted && scev_initialized_p ())
    scev_reset_htab ();

  loops_state_clear (LOOPS_NEED_FIXUP);

  /* Apply flags to loops.  */
  apply_loop_flags (current_loops->state | record_exits);

#ifdef ENABLE_CHECKING
  verify_loop_structure ();
#endif

  timevar_pop (TV_LOOP_INIT);

  return number_of_loops (cfun) - old_nloops;
}

/* The RTL loop superpass.  The actual passes are subpasses.  See passes.c for
   more on that.  */

namespace {

const pass_data pass_data_loop2 =
{
  RTL_PASS, /* type */
  "loop2", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_loop2 : public rtl_opt_pass
{
public:
  pass_loop2 (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_loop2, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *);

}; // class pass_loop2

bool
pass_loop2::gate (function *fun)
{
  if (optimize > 0
      && (flag_move_loop_invariants
	  || flag_unswitch_loops
	  || flag_unroll_loops
	  || (flag_branch_on_count_reg
	      && targetm.have_doloop_end ())))
    return true;
  else
    {
      /* No longer preserve loops, remove them now.  */
      fun->curr_properties &= ~PROP_loops;
      if (current_loops)
	loop_optimizer_finalize ();
      return false;
    } 
}

} // anon namespace

rtl_opt_pass *
make_pass_loop2 (gcc::context *ctxt)
{
  return new pass_loop2 (ctxt);
}


/* Initialization of the RTL loop passes.  */
static unsigned int
rtl_loop_init (void)
{
  gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT);

  if (dump_file)
    {
      dump_reg_info (dump_file);
      dump_flow_info (dump_file, dump_flags);
    }

  loop_optimizer_init (LOOPS_NORMAL);
  return 0;
}

namespace {

const pass_data pass_data_rtl_loop_init =
{
  RTL_PASS, /* type */
  "loop2_init", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_rtl_loop_init : public rtl_opt_pass
{
public:
  pass_rtl_loop_init (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_rtl_loop_init, ctxt)
  {}

  /* opt_pass methods: */
  virtual unsigned int execute (function *) { return rtl_loop_init (); }

}; // class pass_rtl_loop_init

} // anon namespace

rtl_opt_pass *
make_pass_rtl_loop_init (gcc::context *ctxt)
{
  return new pass_rtl_loop_init (ctxt);
}


/* Finalization of the RTL loop passes.  */

namespace {

const pass_data pass_data_rtl_loop_done =
{
  RTL_PASS, /* type */
  "loop2_done", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  PROP_loops, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_rtl_loop_done : public rtl_opt_pass
{
public:
  pass_rtl_loop_done (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_rtl_loop_done, ctxt)
  {}

  /* opt_pass methods: */
  virtual unsigned int execute (function *);

}; // class pass_rtl_loop_done

unsigned int
pass_rtl_loop_done::execute (function *fun)
{
  /* No longer preserve loops, remove them now.  */
  fun->curr_properties &= ~PROP_loops;
  loop_optimizer_finalize ();
  free_dominance_info (CDI_DOMINATORS);

  cleanup_cfg (0);
  if (dump_file)
    {
      dump_reg_info (dump_file);
      dump_flow_info (dump_file, dump_flags);
    }

  return 0;
}

} // anon namespace

rtl_opt_pass *
make_pass_rtl_loop_done (gcc::context *ctxt)
{
  return new pass_rtl_loop_done (ctxt);
}


/* Loop invariant code motion.  */

namespace {

const pass_data pass_data_rtl_move_loop_invariants =
{
  RTL_PASS, /* type */
  "loop2_invariant", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP_MOVE_INVARIANTS, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  ( TODO_df_verify | TODO_df_finish ), /* todo_flags_finish */
};

class pass_rtl_move_loop_invariants : public rtl_opt_pass
{
public:
  pass_rtl_move_loop_invariants (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_rtl_move_loop_invariants, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *) { return flag_move_loop_invariants; }
  virtual unsigned int execute (function *fun)
    {
      if (number_of_loops (fun) > 1)
	move_loop_invariants ();
      return 0;
    }

}; // class pass_rtl_move_loop_invariants

} // anon namespace

rtl_opt_pass *
make_pass_rtl_move_loop_invariants (gcc::context *ctxt)
{
  return new pass_rtl_move_loop_invariants (ctxt);
}


namespace {

const pass_data pass_data_rtl_unroll_loops =
{
  RTL_PASS, /* type */
  "loop2_unroll", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP_UNROLL, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_rtl_unroll_loops : public rtl_opt_pass
{
public:
  pass_rtl_unroll_loops (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_rtl_unroll_loops, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *)
    {
      return (flag_peel_loops || flag_unroll_loops || flag_unroll_all_loops);
    }

  virtual unsigned int execute (function *);

}; // class pass_rtl_unroll_loops

unsigned int
pass_rtl_unroll_loops::execute (function *fun)
{
  if (number_of_loops (fun) > 1)
    {
      int flags = 0;
      if (dump_file)
	df_dump (dump_file);

      if (flag_unroll_loops)
	flags |= UAP_UNROLL;
      if (flag_unroll_all_loops)
	flags |= UAP_UNROLL_ALL;

      unroll_loops (flags);
    }
  return 0;
}

} // anon namespace

rtl_opt_pass *
make_pass_rtl_unroll_loops (gcc::context *ctxt)
{
  return new pass_rtl_unroll_loops (ctxt);
}


namespace {

const pass_data pass_data_rtl_doloop =
{
  RTL_PASS, /* type */
  "loop2_doloop", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_LOOP_DOLOOP, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_rtl_doloop : public rtl_opt_pass
{
public:
  pass_rtl_doloop (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_rtl_doloop, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *);
  virtual unsigned int execute (function *);

}; // class pass_rtl_doloop

bool
pass_rtl_doloop::gate (function *)
{
  return (flag_branch_on_count_reg && targetm.have_doloop_end ());
}

unsigned int
pass_rtl_doloop::execute (function *fun)
{
  if (number_of_loops (fun) > 1)
    doloop_optimize_loops ();
  return 0;
}

} // anon namespace

rtl_opt_pass *
make_pass_rtl_doloop (gcc::context *ctxt)
{
  return new pass_rtl_doloop (ctxt);
}