llvm.org GIT mirror llvm / 58bfcdb lib / Analysis / RegionInfo.cpp
58bfcdb

Tree @58bfcdb (Download .tar.gz)

RegionInfo.cpp @58bfcdbraw · history · blame

  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
//===- RegionInfo.cpp - SESE region detection analysis --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Detects single entry single exit regions in the control flow graph.
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/RegionInfo.h"
#include "llvm/Analysis/RegionIterator.h"

#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Assembly/Writer.h"

#define DEBUG_TYPE "region"
#include "llvm/Support/Debug.h"

#include <set>
#include <algorithm>

using namespace llvm;

// Always verify if expensive checking is enabled.
#ifdef XDEBUG
static bool VerifyRegionInfo = true;
#else
static bool VerifyRegionInfo = false;
#endif

static cl::opt<bool,true>
VerifyRegionInfoX("verify-region-info", cl::location(VerifyRegionInfo),
                cl::desc("Verify region info (time consuming)"));

STATISTIC(numRegions,       "The # of regions");
STATISTIC(numSimpleRegions, "The # of simple regions");

//===----------------------------------------------------------------------===//
/// PrintStyle - Print region in difference ways.
enum PrintStyle { PrintNone, PrintBB, PrintRN  };

static cl::opt<enum PrintStyle> printStyle("print-region-style", cl::Hidden,
  cl::desc("style of printing regions"),
  cl::values(
    clEnumValN(PrintNone, "none",  "print no details"),
    clEnumValN(PrintBB, "bb",  "print regions in detail with block_iterator"),
    clEnumValN(PrintRN, "rn",  "print regions in detail with element_iterator"),
    clEnumValEnd));
//===----------------------------------------------------------------------===//
/// Region Implementation
Region::Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RInfo,
               DominatorTree *dt, Region *Parent)
               : RegionNode(Parent, Entry, 1), RI(RInfo), DT(dt), exit(Exit) {}

Region::~Region() {
  // Free the cached nodes.
  for (BBNodeMapT::iterator it = BBNodeMap.begin(),
         ie = BBNodeMap.end(); it != ie; ++it)
    delete it->second;

  // Only clean the cache for this Region. Caches of child Regions will be
  // cleaned when the child Regions are deleted.
  BBNodeMap.clear();

  for (iterator I = begin(), E = end(); I != E; ++I)
    delete *I;
}

void Region::replaceEntry(BasicBlock *BB) {
  entry.setPointer(BB);
}

void Region::replaceExit(BasicBlock *BB) {
  assert(exit && "No exit to replace!");
  exit = BB;
}

bool Region::contains(const BasicBlock *B) const {
  BasicBlock *BB = const_cast<BasicBlock*>(B);

  assert(DT->getNode(BB) && "BB not part of the dominance tree");

  BasicBlock *entry = getEntry(), *exit = getExit();

  // Toplevel region.
  if (!exit)
    return true;

  return (DT->dominates(entry, BB)
    && !(DT->dominates(exit, BB) && DT->dominates(entry, exit)));
}

bool Region::contains(const Loop *L) const {
  // BBs that are not part of any loop are element of the Loop
  // described by the NULL pointer. This loop is not part of any region,
  // except if the region describes the whole function.
  if (L == 0)
    return getExit() == 0;

  if (!contains(L->getHeader()))
    return false;

  SmallVector<BasicBlock *, 8> ExitingBlocks;
  L->getExitingBlocks(ExitingBlocks);

  for (SmallVectorImpl<BasicBlock*>::iterator BI = ExitingBlocks.begin(),
       BE = ExitingBlocks.end(); BI != BE; ++BI)
    if (!contains(*BI))
      return false;

  return true;
}

Loop *Region::outermostLoopInRegion(Loop *L) const {
  if (!contains(L))
    return 0;

  while (L && contains(L->getParentLoop())) {
    L = L->getParentLoop();
  }

  return L;
}

Loop *Region::outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const {
  assert(LI && BB && "LI and BB cannot be null!");
  Loop *L = LI->getLoopFor(BB);
  return outermostLoopInRegion(L);
}

BasicBlock *Region::getEnteringBlock() const {
  BasicBlock *entry = getEntry();
  BasicBlock *Pred;
  BasicBlock *enteringBlock = 0;

  for (pred_iterator PI = pred_begin(entry), PE = pred_end(entry); PI != PE;
       ++PI) {
    Pred = *PI;
    if (DT->getNode(Pred) && !contains(Pred)) {
      if (enteringBlock)
        return 0;

      enteringBlock = Pred;
    }
  }

  return enteringBlock;
}

BasicBlock *Region::getExitingBlock() const {
  BasicBlock *exit = getExit();
  BasicBlock *Pred;
  BasicBlock *exitingBlock = 0;

  if (!exit)
    return 0;

  for (pred_iterator PI = pred_begin(exit), PE = pred_end(exit); PI != PE;
       ++PI) {
    Pred = *PI;
    if (contains(Pred)) {
      if (exitingBlock)
        return 0;

      exitingBlock = Pred;
    }
  }

  return exitingBlock;
}

bool Region::isSimple() const {
  return !isTopLevelRegion() && getEnteringBlock() && getExitingBlock();
}

std::string Region::getNameStr() const {
  std::string exitName;
  std::string entryName;

  if (getEntry()->getName().empty()) {
    raw_string_ostream OS(entryName);

    WriteAsOperand(OS, getEntry(), false);
    entryName = OS.str();
  } else
    entryName = getEntry()->getNameStr();

  if (getExit()) {
    if (getExit()->getName().empty()) {
      raw_string_ostream OS(exitName);

      WriteAsOperand(OS, getExit(), false);
      exitName = OS.str();
    } else
      exitName = getExit()->getNameStr();
  } else
    exitName = "<Function Return>";

  return entryName + " => " + exitName;
}

void Region::verifyBBInRegion(BasicBlock *BB) const {
  if (!contains(BB))
    llvm_unreachable("Broken region found!");

  BasicBlock *entry = getEntry(), *exit = getExit();

  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
    if (!contains(*SI) && exit != *SI)
      llvm_unreachable("Broken region found!");

  if (entry != BB)
    for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB); SI != SE; ++SI)
      if (!contains(*SI))
        llvm_unreachable("Broken region found!");
}

void Region::verifyWalk(BasicBlock *BB, std::set<BasicBlock*> *visited) const {
  BasicBlock *exit = getExit();

  visited->insert(BB);

  verifyBBInRegion(BB);

  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
    if (*SI != exit && visited->find(*SI) == visited->end())
        verifyWalk(*SI, visited);
}

void Region::verifyRegion() const {
  // Only do verification when user wants to, otherwise this expensive
  // check will be invoked by PassManager.
  if (!VerifyRegionInfo) return;

  std::set<BasicBlock*> visited;
  verifyWalk(getEntry(), &visited);
}

void Region::verifyRegionNest() const {
  for (Region::const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
    (*RI)->verifyRegionNest();

  verifyRegion();
}

Region::block_iterator Region::block_begin() {
  return GraphTraits<FlatIt<Region*> >::nodes_begin(this);
}

Region::block_iterator Region::block_end() {
  return GraphTraits<FlatIt<Region*> >::nodes_end(this);
}

Region::const_block_iterator Region::block_begin() const {
  return GraphTraits<FlatIt<const Region*> >::nodes_begin(this);
}

Region::const_block_iterator Region::block_end() const {
  return GraphTraits<FlatIt<const Region*> >::nodes_end(this);
}

Region::element_iterator Region::element_begin() {
  return GraphTraits<Region*>::nodes_begin(this);
}

Region::element_iterator Region::element_end() {
  return GraphTraits<Region*>::nodes_end(this);
}

Region::const_element_iterator Region::element_begin() const {
  return GraphTraits<const Region*>::nodes_begin(this);
}

Region::const_element_iterator Region::element_end() const {
  return GraphTraits<const Region*>::nodes_end(this);
}

Region* Region::getSubRegionNode(BasicBlock *BB) const {
  Region *R = RI->getRegionFor(BB);

  if (!R || R == this)
    return 0;

  // If we pass the BB out of this region, that means our code is broken.
  assert(contains(R) && "BB not in current region!");

  while (contains(R->getParent()) && R->getParent() != this)
    R = R->getParent();

  if (R->getEntry() != BB)
    return 0;

  return R;
}

RegionNode* Region::getBBNode(BasicBlock *BB) const {
  assert(contains(BB) && "Can get BB node out of this region!");

  BBNodeMapT::const_iterator at = BBNodeMap.find(BB);

  if (at != BBNodeMap.end())
    return at->second;

  RegionNode *NewNode = new RegionNode(const_cast<Region*>(this), BB);
  BBNodeMap.insert(std::make_pair(BB, NewNode));
  return NewNode;
}

RegionNode* Region::getNode(BasicBlock *BB) const {
  assert(contains(BB) && "Can get BB node out of this region!");
  if (Region* Child = getSubRegionNode(BB))
    return Child->getNode();

  return getBBNode(BB);
}

void Region::transferChildrenTo(Region *To) {
  for (iterator I = begin(), E = end(); I != E; ++I) {
    (*I)->parent = To;
    To->children.push_back(*I);
  }
  children.clear();
}

void Region::addSubRegion(Region *SubRegion, bool moveChildren) {
  assert(SubRegion->parent == 0 && "SubRegion already has a parent!");
  assert(std::find(begin(), end(), SubRegion) == children.end()
         && "Subregion already exists!");

  SubRegion->parent = this;
  children.push_back(SubRegion);

  if (!moveChildren)
    return;

  assert(SubRegion->children.size() == 0
         && "SubRegions that contain children are not supported");

  for (element_iterator I = element_begin(), E = element_end(); I != E; ++I)
    if (!(*I)->isSubRegion()) {
      BasicBlock *BB = (*I)->getNodeAs<BasicBlock>();

      if (SubRegion->contains(BB))
        RI->setRegionFor(BB, SubRegion);
    }

  std::vector<Region*> Keep;
  for (iterator I = begin(), E = end(); I != E; ++I)
    if (SubRegion->contains(*I) && *I != SubRegion) {
      SubRegion->children.push_back(*I);
      (*I)->parent = SubRegion;
    } else
      Keep.push_back(*I);

  children.clear();
  children.insert(children.begin(), Keep.begin(), Keep.end());
}


Region *Region::removeSubRegion(Region *Child) {
  assert(Child->parent == this && "Child is not a child of this region!");
  Child->parent = 0;
  RegionSet::iterator I = std::find(children.begin(), children.end(), Child);
  assert(I != children.end() && "Region does not exit. Unable to remove.");
  children.erase(children.begin()+(I-begin()));
  return Child;
}

unsigned Region::getDepth() const {
  unsigned Depth = 0;

  for (Region *R = parent; R != 0; R = R->parent)
    ++Depth;

  return Depth;
}

Region *Region::getExpandedRegion() const {
  unsigned NumSuccessors = exit->getTerminator()->getNumSuccessors();

  if (NumSuccessors == 0)
    return NULL;

  for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
       PI != PE; ++PI)
    if (!DT->dominates(getEntry(), *PI))
      return NULL;

  Region *R = RI->getRegionFor(exit);

  if (R->getEntry() != exit) {
    if (exit->getTerminator()->getNumSuccessors() == 1)
      return new Region(getEntry(), *succ_begin(exit), RI, DT);
    else
      return NULL;
  }

  while (R->getParent() && R->getParent()->getEntry() == exit)
    R = R->getParent();

  if (!DT->dominates(getEntry(), R->getExit()))
    for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
         PI != PE; ++PI)
    if (!DT->dominates(R->getExit(), *PI))
      return NULL;

  return new Region(getEntry(), R->getExit(), RI, DT);
}

void Region::print(raw_ostream &OS, bool print_tree, unsigned level) const {
  if (print_tree)
    OS.indent(level*2) << "[" << level << "] " << getNameStr();
  else
    OS.indent(level*2) << getNameStr();

  OS << "\n";


  if (printStyle != PrintNone) {
    OS.indent(level*2) << "{\n";
    OS.indent(level*2 + 2);

    if (printStyle == PrintBB) {
      for (const_block_iterator I = block_begin(), E = block_end(); I!=E; ++I)
        OS << **I << ", "; // TODO: remove the last ","
    } else if (printStyle == PrintRN) {
      for (const_element_iterator I = element_begin(), E = element_end(); I!=E; ++I)
        OS << **I << ", "; // TODO: remove the last ",
    }

    OS << "\n";
  }

  if (print_tree)
    for (const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
      (*RI)->print(OS, print_tree, level+1);

  if (printStyle != PrintNone)
    OS.indent(level*2) << "} \n";
}

void Region::dump() const {
  print(dbgs(), true, getDepth());
}

void Region::clearNodeCache() {
  // Free the cached nodes.
  for (BBNodeMapT::iterator I = BBNodeMap.begin(),
       IE = BBNodeMap.end(); I != IE; ++I)
    delete I->second;

  BBNodeMap.clear();
  for (Region::iterator RI = begin(), RE = end(); RI != RE; ++RI)
    (*RI)->clearNodeCache();
}

//===----------------------------------------------------------------------===//
// RegionInfo implementation
//

bool RegionInfo::isCommonDomFrontier(BasicBlock *BB, BasicBlock *entry,
                                     BasicBlock *exit) const {
  for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
    BasicBlock *P = *PI;
    if (DT->dominates(entry, P) && !DT->dominates(exit, P))
      return false;
  }
  return true;
}

bool RegionInfo::isRegion(BasicBlock *entry, BasicBlock *exit) const {
  assert(entry && exit && "entry and exit must not be null!");
  typedef DominanceFrontier::DomSetType DST;

  DST *entrySuccs = &DF->find(entry)->second;

  // Exit is the header of a loop that contains the entry. In this case,
  // the dominance frontier must only contain the exit.
  if (!DT->dominates(entry, exit)) {
    for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
         SI != SE; ++SI)
      if (*SI != exit && *SI != entry)
        return false;

    return true;
  }

  DST *exitSuccs = &DF->find(exit)->second;

  // Do not allow edges leaving the region.
  for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
       SI != SE; ++SI) {
    if (*SI == exit || *SI == entry)
      continue;
    if (exitSuccs->find(*SI) == exitSuccs->end())
      return false;
    if (!isCommonDomFrontier(*SI, entry, exit))
      return false;
  }

  // Do not allow edges pointing into the region.
  for (DST::iterator SI = exitSuccs->begin(), SE = exitSuccs->end();
       SI != SE; ++SI)
    if (DT->properlyDominates(entry, *SI) && *SI != exit)
      return false;


  return true;
}

void RegionInfo::insertShortCut(BasicBlock *entry, BasicBlock *exit,
                             BBtoBBMap *ShortCut) const {
  assert(entry && exit && "entry and exit must not be null!");

  BBtoBBMap::iterator e = ShortCut->find(exit);

  if (e == ShortCut->end())
    // No further region at exit available.
    (*ShortCut)[entry] = exit;
  else {
    // We found a region e that starts at exit. Therefore (entry, e->second)
    // is also a region, that is larger than (entry, exit). Insert the
    // larger one.
    BasicBlock *BB = e->second;
    (*ShortCut)[entry] = BB;
  }
}

DomTreeNode* RegionInfo::getNextPostDom(DomTreeNode* N,
                                        BBtoBBMap *ShortCut) const {
  BBtoBBMap::iterator e = ShortCut->find(N->getBlock());

  if (e == ShortCut->end())
    return N->getIDom();

  return PDT->getNode(e->second)->getIDom();
}

bool RegionInfo::isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const {
  assert(entry && exit && "entry and exit must not be null!");

  unsigned num_successors = succ_end(entry) - succ_begin(entry);

  if (num_successors <= 1 && exit == *(succ_begin(entry)))
    return true;

  return false;
}

void RegionInfo::updateStatistics(Region *R) {
  ++numRegions;

  // TODO: Slow. Should only be enabled if -stats is used.
  if (R->isSimple()) ++numSimpleRegions;
}

Region *RegionInfo::createRegion(BasicBlock *entry, BasicBlock *exit) {
  assert(entry && exit && "entry and exit must not be null!");

  if (isTrivialRegion(entry, exit))
    return 0;

  Region *region = new Region(entry, exit, this, DT);
  BBtoRegion.insert(std::make_pair(entry, region));

 #ifdef XDEBUG
    region->verifyRegion();
 #else
    DEBUG(region->verifyRegion());
 #endif

  updateStatistics(region);
  return region;
}

void RegionInfo::findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut) {
  assert(entry);

  DomTreeNode *N = PDT->getNode(entry);

  if (!N)
    return;

  Region *lastRegion= 0;
  BasicBlock *lastExit = entry;

  // As only a BasicBlock that postdominates entry can finish a region, walk the
  // post dominance tree upwards.
  while ((N = getNextPostDom(N, ShortCut))) {
    BasicBlock *exit = N->getBlock();

    if (!exit)
      break;

    if (isRegion(entry, exit)) {
      Region *newRegion = createRegion(entry, exit);

      if (lastRegion)
        newRegion->addSubRegion(lastRegion);

      lastRegion = newRegion;
      lastExit = exit;
    }

    // This can never be a region, so stop the search.
    if (!DT->dominates(entry, exit))
      break;
  }

  // Tried to create regions from entry to lastExit.  Next time take a
  // shortcut from entry to lastExit.
  if (lastExit != entry)
    insertShortCut(entry, lastExit, ShortCut);
}

void RegionInfo::scanForRegions(Function &F, BBtoBBMap *ShortCut) {
  BasicBlock *entry = &(F.getEntryBlock());
  DomTreeNode *N = DT->getNode(entry);

  // Iterate over the dominance tree in post order to start with the small
  // regions from the bottom of the dominance tree.  If the small regions are
  // detected first, detection of bigger regions is faster, as we can jump
  // over the small regions.
  for (po_iterator<DomTreeNode*> FI = po_begin(N), FE = po_end(N); FI != FE;
    ++FI) {
    findRegionsWithEntry(FI->getBlock(), ShortCut);
  }
}

Region *RegionInfo::getTopMostParent(Region *region) {
  while (region->parent)
    region = region->getParent();

  return region;
}

void RegionInfo::buildRegionsTree(DomTreeNode *N, Region *region) {
  BasicBlock *BB = N->getBlock();

  // Passed region exit
  while (BB == region->getExit())
    region = region->getParent();

  BBtoRegionMap::iterator it = BBtoRegion.find(BB);

  // This basic block is a start block of a region. It is already in the
  // BBtoRegion relation. Only the child basic blocks have to be updated.
  if (it != BBtoRegion.end()) {
    Region *newRegion = it->second;;
    region->addSubRegion(getTopMostParent(newRegion));
    region = newRegion;
  } else {
    BBtoRegion[BB] = region;
  }

  for (DomTreeNode::iterator CI = N->begin(), CE = N->end(); CI != CE; ++CI)
    buildRegionsTree(*CI, region);
}

void RegionInfo::releaseMemory() {
  BBtoRegion.clear();
  if (TopLevelRegion)
    delete TopLevelRegion;
  TopLevelRegion = 0;
}

RegionInfo::RegionInfo() : FunctionPass(ID) {
  initializeRegionInfoPass(*PassRegistry::getPassRegistry());
  TopLevelRegion = 0;
}

RegionInfo::~RegionInfo() {
  releaseMemory();
}

void RegionInfo::Calculate(Function &F) {
  // ShortCut a function where for every BB the exit of the largest region
  // starting with BB is stored. These regions can be threated as single BBS.
  // This improves performance on linear CFGs.
  BBtoBBMap ShortCut;

  scanForRegions(F, &ShortCut);
  BasicBlock *BB = &F.getEntryBlock();
  buildRegionsTree(DT->getNode(BB), TopLevelRegion);
}

bool RegionInfo::runOnFunction(Function &F) {
  releaseMemory();

  DT = &getAnalysis<DominatorTree>();
  PDT = &getAnalysis<PostDominatorTree>();
  DF = &getAnalysis<DominanceFrontier>();

  TopLevelRegion = new Region(&F.getEntryBlock(), 0, this, DT, 0);
  updateStatistics(TopLevelRegion);

  Calculate(F);

  return false;
}

void RegionInfo::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.setPreservesAll();
  AU.addRequiredTransitive<DominatorTree>();
  AU.addRequired<PostDominatorTree>();
  AU.addRequired<DominanceFrontier>();
}

void RegionInfo::print(raw_ostream &OS, const Module *) const {
  OS << "Region tree:\n";
  TopLevelRegion->print(OS, true, 0);
  OS << "End region tree\n";
}

void RegionInfo::verifyAnalysis() const {
  // Only do verification when user wants to, otherwise this expensive check
  // will be invoked by PMDataManager::verifyPreservedAnalysis when
  // a regionpass (marked PreservedAll) finish.
  if (!VerifyRegionInfo) return;

  TopLevelRegion->verifyRegionNest();
}

// Region pass manager support.
Region *RegionInfo::getRegionFor(BasicBlock *BB) const {
  BBtoRegionMap::const_iterator I=
    BBtoRegion.find(BB);
  return I != BBtoRegion.end() ? I->second : 0;
}

void RegionInfo::setRegionFor(BasicBlock *BB, Region *R) {
  BBtoRegion[BB] = R;
}

Region *RegionInfo::operator[](BasicBlock *BB) const {
  return getRegionFor(BB);
}

BasicBlock *RegionInfo::getMaxRegionExit(BasicBlock *BB) const {
  BasicBlock *Exit = NULL;

  while (true) {
    // Get largest region that starts at BB.
    Region *R = getRegionFor(BB);
    while (R && R->getParent() && R->getParent()->getEntry() == BB)
      R = R->getParent();

    // Get the single exit of BB.
    if (R && R->getEntry() == BB)
      Exit = R->getExit();
    else if (++succ_begin(BB) == succ_end(BB))
      Exit = *succ_begin(BB);
    else // No single exit exists.
      return Exit;

    // Get largest region that starts at Exit.
    Region *ExitR = getRegionFor(Exit);
    while (ExitR && ExitR->getParent()
           && ExitR->getParent()->getEntry() == Exit)
      ExitR = ExitR->getParent();

    for (pred_iterator PI = pred_begin(Exit), PE = pred_end(Exit); PI != PE;
         ++PI)
      if (!R->contains(*PI) && !ExitR->contains(*PI))
        break;

    // This stops infinite cycles.
    if (DT->dominates(Exit, BB))
      break;

    BB = Exit;
  }

  return Exit;
}

Region*
RegionInfo::getCommonRegion(Region *A, Region *B) const {
  assert (A && B && "One of the Regions is NULL");

  if (A->contains(B)) return A;

  while (!B->contains(A))
    B = B->getParent();

  return B;
}

Region*
RegionInfo::getCommonRegion(SmallVectorImpl<Region*> &Regions) const {
  Region* ret = Regions.back();
  Regions.pop_back();

  for (SmallVectorImpl<Region*>::const_iterator I = Regions.begin(),
       E = Regions.end(); I != E; ++I)
      ret = getCommonRegion(ret, *I);

  return ret;
}

Region*
RegionInfo::getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const {
  Region* ret = getRegionFor(BBs.back());
  BBs.pop_back();

  for (SmallVectorImpl<BasicBlock*>::const_iterator I = BBs.begin(),
       E = BBs.end(); I != E; ++I)
      ret = getCommonRegion(ret, getRegionFor(*I));

  return ret;
}

void RegionInfo::splitBlock(BasicBlock* NewBB, BasicBlock *OldBB)
{
  Region *R = getRegionFor(OldBB);

  setRegionFor(NewBB, R);

  while (R->getEntry() == OldBB && !R->isTopLevelRegion()) {
    R->replaceEntry(NewBB);
    R = R->getParent();
  }

  setRegionFor(OldBB, R);
}

char RegionInfo::ID = 0;
INITIALIZE_PASS_BEGIN(RegionInfo, "regions",
                "Detect single entry single exit regions", true, true)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(PostDominatorTree)
INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
INITIALIZE_PASS_END(RegionInfo, "regions",
                "Detect single entry single exit regions", true, true)

// Create methods available outside of this file, to use them
// "include/llvm/LinkAllPasses.h". Otherwise the pass would be deleted by
// the link time optimization.

namespace llvm {
  FunctionPass *createRegionInfoPass() {
    return new RegionInfo();
  }
}