lib/Analysis/RegionInfo.cpp

   1 //===- RegionInfo.cpp - SESE region detection analysis --------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 // Detects single entry single exit regions in the control flow graph.
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "llvm/Analysis/RegionInfo.h"
  13 #include "llvm/Analysis/RegionIterator.h"
  14
  15 #include "llvm/ADT/PostOrderIterator.h"
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/Support/CommandLine.h"
  18 #include "llvm/Support/ErrorHandling.h"
  19 #include "llvm/Support/raw_ostream.h"
  20 #include "llvm/Analysis/LoopInfo.h"
  21
  22 #define DEBUG_TYPE "region"
  23 #include "llvm/Support/Debug.h"
  24
  25 #include <set>
  26 #include <algorithm>
  27
  28 using namespace llvm;
  29
  30 // Always verify if expensive checking is enabled.
  31 #ifdef XDEBUG
  32 static bool VerifyRegionInfo = true;
  33 #else
  34 static bool VerifyRegionInfo = false;
  35 #endif
  36
  37 static cl::opt<bool,true>
  38 VerifyRegionInfoX("verify-region-info", cl::location(VerifyRegionInfo),
  39                 cl::desc("Verify region info (time consuming)"));
  40
  41 STATISTIC(numRegions,       "The # of regions");
  42 STATISTIC(numSimpleRegions, "The # of simple regions");
  43
  44 //===----------------------------------------------------------------------===//
  45 /// PrintStyle - Print region in difference ways.
  46 enum PrintStyle { PrintNone, PrintBB, PrintRN  };
  47
  48 static cl::opt<enum PrintStyle> printStyle("print-region-style", cl::Hidden,
  49   cl::desc("style of printing regions"),
  50   cl::values(
  51     clEnumValN(PrintNone, "none",  "print no details"),
  52     clEnumValN(PrintBB, "bb",  "print regions in detail with block_iterator"),
  53     clEnumValN(PrintRN, "rn",  "print regions in detail with element_iterator"),
  54     clEnumValEnd));
  55 //===----------------------------------------------------------------------===//
  56 /// Region Implementation
  57 Region::Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RInfo,
  58                DominatorTree *dt, Region *Parent)
  59                : RegionNode(Parent, Entry, 1), RI(RInfo), DT(dt), exit(Exit) {}
  60
  61 Region::~Region() {
  62   // Free the cached nodes.
  63   for (BBNodeMapT::iterator it = BBNodeMap.begin(),
  64          ie = BBNodeMap.end(); it != ie; ++it)
  65     delete it->second;
  66
  67   // Only clean the cache for this Region. Caches of child Regions will be
  68   // cleaned when the child Regions are deleted.
  69   BBNodeMap.clear();
  70
  71   for (iterator I = begin(), E = end(); I != E; ++I)
  72     delete *I;
  73 }
  74
  75 void Region::replaceEntry(BasicBlock *BB) {
  76   entry.setPointer(BB);
  77 }
  78
  79 void Region::replaceExit(BasicBlock *BB) {
  80   assert(exit && "No exit to replace!");
  81   exit = BB;
  82 }
  83
  84 bool Region::contains(const BasicBlock *B) const {
  85   BasicBlock *BB = const_cast<BasicBlock*>(B);
  86
  87   assert(DT->getNode(BB) && "BB not part of the dominance tree");
  88
  89   BasicBlock *entry = getEntry(), *exit = getExit();
  90
  91   // Toplevel region.
  92   if (!exit)
  93     return true;
  94
  95   return (DT->dominates(entry, BB)
  96     && !(DT->dominates(exit, BB) && DT->dominates(entry, exit)));
  97 }
  98
  99 bool Region::contains(const Loop *L) const {
 100   // BBs that are not part of any loop are element of the Loop
 101   // described by the NULL pointer. This loop is not part of any region,
 102   // except if the region describes the whole function.
 103   if (L == 0)
 104     return getExit() == 0;
 105
 106   if (!contains(L->getHeader()))
 107     return false;
 108
 109   SmallVector<BasicBlock *, 8> ExitingBlocks;
 110   L->getExitingBlocks(ExitingBlocks);
 111
 112   for (SmallVectorImpl<BasicBlock*>::iterator BI = ExitingBlocks.begin(),
 113        BE = ExitingBlocks.end(); BI != BE; ++BI)
 114     if (!contains(*BI))
 115       return false;
 116
 117   return true;
 118 }
 119
 120 Loop *Region::outermostLoopInRegion(Loop *L) const {
 121   if (!contains(L))
 122     return 0;
 123
 124   while (L && contains(L->getParentLoop())) {
 125     L = L->getParentLoop();
 126   }
 127
 128   return L;
 129 }
 130
 131 Loop *Region::outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const {
 132   assert(LI && BB && "LI and BB cannot be null!");
 133   Loop *L = LI->getLoopFor(BB);
 134   return outermostLoopInRegion(L);
 135 }
 136
 137 bool Region::isSimple() const {
 138   bool isSimple = true;
 139   bool found = false;
 140
 141   BasicBlock *entry = getEntry(), *exit = getExit();
 142
 143   if (isTopLevelRegion())
 144     return false;
 145
 146   for (pred_iterator PI = pred_begin(entry), PE = pred_end(entry); PI != PE;
 147        ++PI) {
 148     BasicBlock *Pred = *PI;
 149     if (DT->getNode(Pred) && !contains(Pred)) {
 150       if (found) {
 151         isSimple = false;
 152         break;
 153       }
 154       found = true;
 155     }
 156   }
 157
 158   found = false;
 159
 160   for (pred_iterator PI = pred_begin(exit), PE = pred_end(exit); PI != PE;
 161        ++PI)
 162     if (contains(*PI)) {
 163       if (found) {
 164         isSimple = false;
 165         break;
 166       }
 167       found = true;
 168     }
 169
 170   return isSimple;
 171 }
 172
 173 std::string Region::getNameStr() const {
 174   std::string exitName;
 175   std::string entryName;
 176
 177   if (getEntry()->getName().empty()) {
 178     raw_string_ostream OS(entryName);
 179
 180     WriteAsOperand(OS, getEntry(), false);
 181     entryName = OS.str();
 182   } else
 183     entryName = getEntry()->getNameStr();
 184
 185   if (getExit()) {
 186     if (getExit()->getName().empty()) {
 187       raw_string_ostream OS(exitName);
 188
 189       WriteAsOperand(OS, getExit(), false);
 190       exitName = OS.str();
 191     } else
 192       exitName = getExit()->getNameStr();
 193   } else
 194     exitName = "<Function Return>";
 195
 196   return entryName + " => " + exitName;
 197 }
 198
 199 void Region::verifyBBInRegion(BasicBlock *BB) const {
 200   if (!contains(BB))
 201     llvm_unreachable("Broken region found!");
 202
 203   BasicBlock *entry = getEntry(), *exit = getExit();
 204
 205   for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
 206     if (!contains(*SI) && exit != *SI)
 207       llvm_unreachable("Broken region found!");
 208
 209   if (entry != BB)
 210     for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB); SI != SE; ++SI)
 211       if (!contains(*SI))
 212         llvm_unreachable("Broken region found!");
 213 }
 214
 215 void Region::verifyWalk(BasicBlock *BB, std::set<BasicBlock*> *visited) const {
 216   BasicBlock *exit = getExit();
 217
 218   visited->insert(BB);
 219
 220   verifyBBInRegion(BB);
 221
 222   for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
 223     if (*SI != exit && visited->find(*SI) == visited->end())
 224         verifyWalk(*SI, visited);
 225 }
 226
 227 void Region::verifyRegion() const {
 228   // Only do verification when user wants to, otherwise this expensive
 229   // check will be invoked by PassManager.
 230   if (!VerifyRegionInfo) return;
 231
 232   std::set<BasicBlock*> visited;
 233   verifyWalk(getEntry(), &visited);
 234 }
 235
 236 void Region::verifyRegionNest() const {
 237   for (Region::const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
 238     (*RI)->verifyRegionNest();
 239
 240   verifyRegion();
 241 }
 242
 243 Region::block_iterator Region::block_begin() {
 244   return GraphTraits<FlatIt<Region*> >::nodes_begin(this);
 245 }
 246
 247 Region::block_iterator Region::block_end() {
 248   return GraphTraits<FlatIt<Region*> >::nodes_end(this);
 249 }
 250
 251 Region::const_block_iterator Region::block_begin() const {
 252   return GraphTraits<FlatIt<const Region*> >::nodes_begin(this);
 253 }
 254
 255 Region::const_block_iterator Region::block_end() const {
 256   return GraphTraits<FlatIt<const Region*> >::nodes_end(this);
 257 }
 258
 259 Region::element_iterator Region::element_begin() {
 260   return GraphTraits<Region*>::nodes_begin(this);
 261 }
 262
 263 Region::element_iterator Region::element_end() {
 264   return GraphTraits<Region*>::nodes_end(this);
 265 }
 266
 267 Region::const_element_iterator Region::element_begin() const {
 268   return GraphTraits<const Region*>::nodes_begin(this);
 269 }
 270
 271 Region::const_element_iterator Region::element_end() const {
 272   return GraphTraits<const Region*>::nodes_end(this);
 273 }
 274
 275 Region* Region::getSubRegionNode(BasicBlock *BB) const {
 276   Region *R = RI->getRegionFor(BB);
 277
 278   if (!R || R == this)
 279     return 0;
 280
 281   // If we pass the BB out of this region, that means our code is broken.
 282   assert(contains(R) && "BB not in current region!");
 283
 284   while (contains(R->getParent()) && R->getParent() != this)
 285     R = R->getParent();
 286
 287   if (R->getEntry() != BB)
 288     return 0;
 289
 290   return R;
 291 }
 292
 293 RegionNode* Region::getBBNode(BasicBlock *BB) const {
 294   assert(contains(BB) && "Can get BB node out of this region!");
 295
 296   BBNodeMapT::const_iterator at = BBNodeMap.find(BB);
 297
 298   if (at != BBNodeMap.end())
 299     return at->second;
 300
 301   RegionNode *NewNode = new RegionNode(const_cast<Region*>(this), BB);
 302   BBNodeMap.insert(std::make_pair(BB, NewNode));
 303   return NewNode;
 304 }
 305
 306 RegionNode* Region::getNode(BasicBlock *BB) const {
 307   assert(contains(BB) && "Can get BB node out of this region!");
 308   if (Region* Child = getSubRegionNode(BB))
 309     return Child->getNode();
 310
 311   return getBBNode(BB);
 312 }
 313
 314 void Region::transferChildrenTo(Region *To) {
 315   for (iterator I = begin(), E = end(); I != E; ++I) {
 316     (*I)->parent = To;
 317     To->children.push_back(*I);
 318   }
 319   children.clear();
 320 }
 321
 322 void Region::addSubRegion(Region *SubRegion, bool moveChildren) {
 323   assert(SubRegion->parent == 0 && "SubRegion already has a parent!");
 324   assert(std::find(begin(), end(), SubRegion) == children.end()
 325          && "Subregion already exists!");
 326
 327   SubRegion->parent = this;
 328   children.push_back(SubRegion);
 329
 330   if (!moveChildren)
 331     return;
 332
 333   assert(SubRegion->children.size() == 0
 334          && "SubRegions that contain children are not supported");
 335
 336   for (element_iterator I = element_begin(), E = element_end(); I != E; ++I)
 337     if (!(*I)->isSubRegion()) {
 338       BasicBlock *BB = (*I)->getNodeAs<BasicBlock>();
 339
 340       if (SubRegion->contains(BB))
 341         RI->setRegionFor(BB, SubRegion);
 342     }
 343
 344   std::vector<Region*> Keep;
 345   for (iterator I = begin(), E = end(); I != E; ++I)
 346     if (SubRegion->contains(*I) && *I != SubRegion) {
 347       SubRegion->children.push_back(*I);
 348       (*I)->parent = SubRegion;
 349     } else
 350       Keep.push_back(*I);
 351
 352   children.clear();
 353   children.insert(children.begin(), Keep.begin(), Keep.end());
 354 }
 355
 356
 357 Region *Region::removeSubRegion(Region *Child) {
 358   assert(Child->parent == this && "Child is not a child of this region!");
 359   Child->parent = 0;
 360   RegionSet::iterator I = std::find(children.begin(), children.end(), Child);
 361   assert(I != children.end() && "Region does not exit. Unable to remove.");
 362   children.erase(children.begin()+(I-begin()));
 363   return Child;
 364 }
 365
 366 unsigned Region::getDepth() const {
 367   unsigned Depth = 0;
 368
 369   for (Region *R = parent; R != 0; R = R->parent)
 370     ++Depth;
 371
 372   return Depth;
 373 }
 374
 375 Region *Region::getExpandedRegion() const {
 376   unsigned NumSuccessors = exit->getTerminator()->getNumSuccessors();
 377
 378   if (NumSuccessors == 0)
 379     return NULL;
 380
 381   for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
 382        PI != PE; ++PI)
 383     if (!DT->dominates(getEntry(), *PI))
 384       return NULL;
 385
 386   Region *R = RI->getRegionFor(exit);
 387
 388   if (R->getEntry() != exit) {
 389     if (exit->getTerminator()->getNumSuccessors() == 1)
 390       return new Region(getEntry(), *succ_begin(exit), RI, DT);
 391     else
 392       return NULL;
 393   }
 394
 395   while (R->getParent() && R->getParent()->getEntry() == exit)
 396     R = R->getParent();
 397
 398   if (!DT->dominates(getEntry(), R->getExit()))
 399     for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
 400          PI != PE; ++PI)
 401     if (!DT->dominates(R->getExit(), *PI))
 402       return NULL;
 403
 404   return new Region(getEntry(), R->getExit(), RI, DT);
 405 }
 406
 407 void Region::print(raw_ostream &OS, bool print_tree, unsigned level) const {
 408   if (print_tree)
 409     OS.indent(level*2) << "[" << level << "] " << getNameStr();
 410   else
 411     OS.indent(level*2) << getNameStr();
 412
 413   OS << "\n";
 414
 415
 416   if (printStyle != PrintNone) {
 417     OS.indent(level*2) << "{\n";
 418     OS.indent(level*2 + 2);
 419
 420     if (printStyle == PrintBB) {
 421       for (const_block_iterator I = block_begin(), E = block_end(); I!=E; ++I)
 422         OS << **I << ", "; // TODO: remove the last ","
 423     } else if (printStyle == PrintRN) {
 424       for (const_element_iterator I = element_begin(), E = element_end(); I!=E; ++I)
 425         OS << **I << ", "; // TODO: remove the last ",
 426     }
 427
 428     OS << "\n";
 429   }
 430
 431   if (print_tree)
 432     for (const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
 433       (*RI)->print(OS, print_tree, level+1);
 434
 435   if (printStyle != PrintNone)
 436     OS.indent(level*2) << "} \n";
 437 }
 438
 439 void Region::dump() const {
 440   print(dbgs(), true, getDepth());
 441 }
 442
 443 void Region::clearNodeCache() {
 444   // Free the cached nodes.
 445   for (BBNodeMapT::iterator I = BBNodeMap.begin(),
 446        IE = BBNodeMap.end(); I != IE; ++I)
 447     delete I->second;
 448
 449   BBNodeMap.clear();
 450   for (Region::iterator RI = begin(), RE = end(); RI != RE; ++RI)
 451     (*RI)->clearNodeCache();
 452 }
 453
 454 //===----------------------------------------------------------------------===//
 455 // RegionInfo implementation
 456 //
 457
 458 bool RegionInfo::isCommonDomFrontier(BasicBlock *BB, BasicBlock *entry,
 459                                      BasicBlock *exit) const {
 460   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
 461     BasicBlock *P = *PI;
 462     if (DT->dominates(entry, P) && !DT->dominates(exit, P))
 463       return false;
 464   }
 465   return true;
 466 }
 467
 468 bool RegionInfo::isRegion(BasicBlock *entry, BasicBlock *exit) const {
 469   assert(entry && exit && "entry and exit must not be null!");
 470   typedef DominanceFrontier::DomSetType DST;
 471
 472   DST *entrySuccs = &DF->find(entry)->second;
 473
 474   // Exit is the header of a loop that contains the entry. In this case,
 475   // the dominance frontier must only contain the exit.
 476   if (!DT->dominates(entry, exit)) {
 477     for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
 478          SI != SE; ++SI)
 479       if (*SI != exit && *SI != entry)
 480         return false;
 481
 482     return true;
 483   }
 484
 485   DST *exitSuccs = &DF->find(exit)->second;
 486
 487   // Do not allow edges leaving the region.
 488   for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
 489        SI != SE; ++SI) {
 490     if (*SI == exit || *SI == entry)
 491       continue;
 492     if (exitSuccs->find(*SI) == exitSuccs->end())
 493       return false;
 494     if (!isCommonDomFrontier(*SI, entry, exit))
 495       return false;
 496   }
 497
 498   // Do not allow edges pointing into the region.
 499   for (DST::iterator SI = exitSuccs->begin(), SE = exitSuccs->end();
 500        SI != SE; ++SI)
 501     if (DT->properlyDominates(entry, *SI) && *SI != exit)
 502       return false;
 503
 504
 505   return true;
 506 }
 507
 508 void RegionInfo::insertShortCut(BasicBlock *entry, BasicBlock *exit,
 509                              BBtoBBMap *ShortCut) const {
 510   assert(entry && exit && "entry and exit must not be null!");
 511
 512   BBtoBBMap::iterator e = ShortCut->find(exit);
 513
 514   if (e == ShortCut->end())
 515     // No further region at exit available.
 516     (*ShortCut)[entry] = exit;
 517   else {
 518     // We found a region e that starts at exit. Therefore (entry, e->second)
 519     // is also a region, that is larger than (entry, exit). Insert the
 520     // larger one.
 521     BasicBlock *BB = e->second;
 522     (*ShortCut)[entry] = BB;
 523   }
 524 }
 525
 526 DomTreeNode* RegionInfo::getNextPostDom(DomTreeNode* N,
 527                                         BBtoBBMap *ShortCut) const {
 528   BBtoBBMap::iterator e = ShortCut->find(N->getBlock());
 529
 530   if (e == ShortCut->end())
 531     return N->getIDom();
 532
 533   return PDT->getNode(e->second)->getIDom();
 534 }
 535
 536 bool RegionInfo::isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const {
 537   assert(entry && exit && "entry and exit must not be null!");
 538
 539   unsigned num_successors = succ_end(entry) - succ_begin(entry);
 540
 541   if (num_successors <= 1 && exit == *(succ_begin(entry)))
 542     return true;
 543
 544   return false;
 545 }
 546
 547 void RegionInfo::updateStatistics(Region *R) {
 548   ++numRegions;
 549
 550   // TODO: Slow. Should only be enabled if -stats is used.
 551   if (R->isSimple()) ++numSimpleRegions;
 552 }
 553
 554 Region *RegionInfo::createRegion(BasicBlock *entry, BasicBlock *exit) {
 555   assert(entry && exit && "entry and exit must not be null!");
 556
 557   if (isTrivialRegion(entry, exit))
 558     return 0;
 559
 560   Region *region = new Region(entry, exit, this, DT);
 561   BBtoRegion.insert(std::make_pair(entry, region));
 562
 563  #ifdef XDEBUG
 564     region->verifyRegion();
 565  #else
 566     DEBUG(region->verifyRegion());
 567  #endif
 568
 569   updateStatistics(region);
 570   return region;
 571 }
 572
 573 void RegionInfo::findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut) {
 574   assert(entry);
 575
 576   DomTreeNode *N = PDT->getNode(entry);
 577
 578   if (!N)
 579     return;
 580
 581   Region *lastRegion= 0;
 582   BasicBlock *lastExit = entry;
 583
 584   // As only a BasicBlock that postdominates entry can finish a region, walk the
 585   // post dominance tree upwards.
 586   while ((N = getNextPostDom(N, ShortCut))) {
 587     BasicBlock *exit = N->getBlock();
 588
 589     if (!exit)
 590       break;
 591
 592     if (isRegion(entry, exit)) {
 593       Region *newRegion = createRegion(entry, exit);
 594
 595       if (lastRegion)
 596         newRegion->addSubRegion(lastRegion);
 597
 598       lastRegion = newRegion;
 599       lastExit = exit;
 600     }
 601
 602     // This can never be a region, so stop the search.
 603     if (!DT->dominates(entry, exit))
 604       break;
 605   }
 606
 607   // Tried to create regions from entry to lastExit.  Next time take a
 608   // shortcut from entry to lastExit.
 609   if (lastExit != entry)
 610     insertShortCut(entry, lastExit, ShortCut);
 611 }
 612
 613 void RegionInfo::scanForRegions(Function &F, BBtoBBMap *ShortCut) {
 614   BasicBlock *entry = &(F.getEntryBlock());
 615   DomTreeNode *N = DT->getNode(entry);
 616
 617   // Iterate over the dominance tree in post order to start with the small
 618   // regions from the bottom of the dominance tree.  If the small regions are
 619   // detected first, detection of bigger regions is faster, as we can jump
 620   // over the small regions.
 621   for (po_iterator<DomTreeNode*> FI = po_begin(N), FE = po_end(N); FI != FE;
 622     ++FI) {
 623     findRegionsWithEntry(FI->getBlock(), ShortCut);
 624   }
 625 }
 626
 627 Region *RegionInfo::getTopMostParent(Region *region) {
 628   while (region->parent)
 629     region = region->getParent();
 630
 631   return region;
 632 }
 633
 634 void RegionInfo::buildRegionsTree(DomTreeNode *N, Region *region) {
 635   BasicBlock *BB = N->getBlock();
 636
 637   // Passed region exit
 638   while (BB == region->getExit())
 639     region = region->getParent();
 640
 641   BBtoRegionMap::iterator it = BBtoRegion.find(BB);
 642
 643   // This basic block is a start block of a region. It is already in the
 644   // BBtoRegion relation. Only the child basic blocks have to be updated.
 645   if (it != BBtoRegion.end()) {
 646     Region *newRegion = it->second;;
 647     region->addSubRegion(getTopMostParent(newRegion));
 648     region = newRegion;
 649   } else {
 650     BBtoRegion[BB] = region;
 651   }
 652
 653   for (DomTreeNode::iterator CI = N->begin(), CE = N->end(); CI != CE; ++CI)
 654     buildRegionsTree(*CI, region);
 655 }
 656
 657 void RegionInfo::releaseMemory() {
 658   BBtoRegion.clear();
 659   if (TopLevelRegion)
 660     delete TopLevelRegion;
 661   TopLevelRegion = 0;
 662 }
 663
 664 RegionInfo::RegionInfo() : FunctionPass(ID) {
 665   initializeRegionInfoPass(*PassRegistry::getPassRegistry());
 666   TopLevelRegion = 0;
 667 }
 668
 669 RegionInfo::~RegionInfo() {
 670   releaseMemory();
 671 }
 672
 673 void RegionInfo::Calculate(Function &F) {
 674   // ShortCut a function where for every BB the exit of the largest region
 675   // starting with BB is stored. These regions can be threated as single BBS.
 676   // This improves performance on linear CFGs.
 677   BBtoBBMap ShortCut;
 678
 679   scanForRegions(F, &ShortCut);
 680   BasicBlock *BB = &F.getEntryBlock();
 681   buildRegionsTree(DT->getNode(BB), TopLevelRegion);
 682 }
 683
 684 bool RegionInfo::runOnFunction(Function &F) {
 685   releaseMemory();
 686
 687   DT = &getAnalysis<DominatorTree>();
 688   PDT = &getAnalysis<PostDominatorTree>();
 689   DF = &getAnalysis<DominanceFrontier>();
 690
 691   TopLevelRegion = new Region(&F.getEntryBlock(), 0, this, DT, 0);
 692   updateStatistics(TopLevelRegion);
 693
 694   Calculate(F);
 695
 696   return false;
 697 }
 698
 699 void RegionInfo::getAnalysisUsage(AnalysisUsage &AU) const {
 700   AU.setPreservesAll();
 701   AU.addRequiredTransitive<DominatorTree>();
 702   AU.addRequired<PostDominatorTree>();
 703   AU.addRequired<DominanceFrontier>();
 704 }
 705
 706 void RegionInfo::print(raw_ostream &OS, const Module *) const {
 707   OS << "Region tree:\n";
 708   TopLevelRegion->print(OS, true, 0);
 709   OS << "End region tree\n";
 710 }
 711
 712 void RegionInfo::verifyAnalysis() const {
 713   // Only do verification when user wants to, otherwise this expensive check
 714   // will be invoked by PMDataManager::verifyPreservedAnalysis when
 715   // a regionpass (marked PreservedAll) finish.
 716   if (!VerifyRegionInfo) return;
 717
 718   TopLevelRegion->verifyRegionNest();
 719 }
 720
 721 // Region pass manager support.
 722 Region *RegionInfo::getRegionFor(BasicBlock *BB) const {
 723   BBtoRegionMap::const_iterator I=
 724     BBtoRegion.find(BB);
 725   return I != BBtoRegion.end() ? I->second : 0;
 726 }
 727
 728 void RegionInfo::setRegionFor(BasicBlock *BB, Region *R) {
 729   BBtoRegion[BB] = R;
 730 }
 731
 732 Region *RegionInfo::operator[](BasicBlock *BB) const {
 733   return getRegionFor(BB);
 734 }
 735
 736 BasicBlock *RegionInfo::getMaxRegionExit(BasicBlock *BB) const {
 737   BasicBlock *Exit = NULL;
 738
 739   while (true) {
 740     // Get largest region that starts at BB.
 741     Region *R = getRegionFor(BB);
 742     while (R && R->getParent() && R->getParent()->getEntry() == BB)
 743       R = R->getParent();
 744
 745     // Get the single exit of BB.
 746     if (R && R->getEntry() == BB)
 747       Exit = R->getExit();
 748     else if (++succ_begin(BB) == succ_end(BB))
 749       Exit = *succ_begin(BB);
 750     else // No single exit exists.
 751       return Exit;
 752
 753     // Get largest region that starts at Exit.
 754     Region *ExitR = getRegionFor(Exit);
 755     while (ExitR && ExitR->getParent()
 756            && ExitR->getParent()->getEntry() == Exit)
 757       ExitR = ExitR->getParent();
 758
 759     for (pred_iterator PI = pred_begin(Exit), PE = pred_end(Exit); PI != PE;
 760          ++PI)
 761       if (!R->contains(*PI) && !ExitR->contains(*PI))
 762         break;
 763
 764     // This stops infinite cycles.
 765     if (DT->dominates(Exit, BB))
 766       break;
 767
 768     BB = Exit;
 769   }
 770
 771   return Exit;
 772 }
 773
 774 Region*
 775 RegionInfo::getCommonRegion(Region *A, Region *B) const {
 776   assert (A && B && "One of the Regions is NULL");
 777
 778   if (A->contains(B)) return A;
 779
 780   while (!B->contains(A))
 781     B = B->getParent();
 782
 783   return B;
 784 }
 785
 786 Region*
 787 RegionInfo::getCommonRegion(SmallVectorImpl<Region*> &Regions) const {
 788   Region* ret = Regions.back();
 789   Regions.pop_back();
 790
 791   for (SmallVectorImpl<Region*>::const_iterator I = Regions.begin(),
 792        E = Regions.end(); I != E; ++I)
 793       ret = getCommonRegion(ret, *I);
 794
 795   return ret;
 796 }
 797
 798 Region*
 799 RegionInfo::getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const {
 800   Region* ret = getRegionFor(BBs.back());
 801   BBs.pop_back();
 802
 803   for (SmallVectorImpl<BasicBlock*>::const_iterator I = BBs.begin(),
 804        E = BBs.end(); I != E; ++I)
 805       ret = getCommonRegion(ret, getRegionFor(*I));
 806
 807   return ret;
 808 }
 809
 810 void RegionInfo::splitBlock(BasicBlock* NewBB, BasicBlock *OldBB)
 811 {
 812   Region *R = getRegionFor(OldBB);
 813
 814   setRegionFor(NewBB, R);
 815
 816   while (R->getEntry() == OldBB && !R->isTopLevelRegion()) {
 817     R->replaceEntry(NewBB);
 818     R = R->getParent();
 819   }
 820
 821   setRegionFor(OldBB, R);
 822 }
 823
 824 char RegionInfo::ID = 0;
 825 INITIALIZE_PASS_BEGIN(RegionInfo, "regions",
 826                 "Detect single entry single exit regions", true, true)
 827 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
 828 INITIALIZE_PASS_DEPENDENCY(PostDominatorTree)
 829 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
 830 INITIALIZE_PASS_END(RegionInfo, "regions",
 831                 "Detect single entry single exit regions", true, true)
 832
 833 // Create methods available outside of this file, to use them
 834 // "include/llvm/LinkAllPasses.h". Otherwise the pass would be deleted by
 835 // the link time optimization.
 836
 837 namespace llvm {
 838   FunctionPass *createRegionInfoPass() {
 839     return new RegionInfo();
 840   }
 841 }
 842