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/Analysis/LoopInfo.h"
  20 #include "llvm/Assembly/Writer.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 static cl::opt<enum Region::PrintStyle> printStyle("print-region-style",
  45   cl::Hidden,
  46   cl::desc("style of printing regions"),
  47   cl::values(
  48     clEnumValN(Region::PrintNone, "none",  "print no details"),
  49     clEnumValN(Region::PrintBB, "bb",
  50                "print regions in detail with block_iterator"),
  51     clEnumValN(Region::PrintRN, "rn",
  52                "print regions in detail with element_iterator"),
  53     clEnumValEnd));
  54 //===----------------------------------------------------------------------===//
  55 /// Region Implementation
  56 Region::Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RInfo,
  57                DominatorTree *dt, Region *Parent)
  58                : RegionNode(Parent, Entry, 1), RI(RInfo), DT(dt), exit(Exit) {}
  59
  60 Region::~Region() {
  61   // Free the cached nodes.
  62   for (BBNodeMapT::iterator it = BBNodeMap.begin(),
  63          ie = BBNodeMap.end(); it != ie; ++it)
  64     delete it->second;
  65
  66   // Only clean the cache for this Region. Caches of child Regions will be
  67   // cleaned when the child Regions are deleted.
  68   BBNodeMap.clear();
  69
  70   for (iterator I = begin(), E = end(); I != E; ++I)
  71     delete *I;
  72 }
  73
  74 void Region::replaceEntry(BasicBlock *BB) {
  75   entry.setPointer(BB);
  76 }
  77
  78 void Region::replaceExit(BasicBlock *BB) {
  79   assert(exit && "No exit to replace!");
  80   exit = BB;
  81 }
  82
  83 bool Region::contains(const BasicBlock *B) const {
  84   BasicBlock *BB = const_cast<BasicBlock*>(B);
  85
  86   assert(DT->getNode(BB) && "BB not part of the dominance tree");
  87
  88   BasicBlock *entry = getEntry(), *exit = getExit();
  89
  90   // Toplevel region.
  91   if (!exit)
  92     return true;
  93
  94   return (DT->dominates(entry, BB)
  95     && !(DT->dominates(exit, BB) && DT->dominates(entry, exit)));
  96 }
  97
  98 bool Region::contains(const Loop *L) const {
  99   // BBs that are not part of any loop are element of the Loop
 100   // described by the NULL pointer. This loop is not part of any region,
 101   // except if the region describes the whole function.
 102   if (L == 0)
 103     return getExit() == 0;
 104
 105   if (!contains(L->getHeader()))
 106     return false;
 107
 108   SmallVector<BasicBlock *, 8> ExitingBlocks;
 109   L->getExitingBlocks(ExitingBlocks);
 110
 111   for (SmallVectorImpl<BasicBlock*>::iterator BI = ExitingBlocks.begin(),
 112        BE = ExitingBlocks.end(); BI != BE; ++BI)
 113     if (!contains(*BI))
 114       return false;
 115
 116   return true;
 117 }
 118
 119 Loop *Region::outermostLoopInRegion(Loop *L) const {
 120   if (!contains(L))
 121     return 0;
 122
 123   while (L && contains(L->getParentLoop())) {
 124     L = L->getParentLoop();
 125   }
 126
 127   return L;
 128 }
 129
 130 Loop *Region::outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const {
 131   assert(LI && BB && "LI and BB cannot be null!");
 132   Loop *L = LI->getLoopFor(BB);
 133   return outermostLoopInRegion(L);
 134 }
 135
 136 BasicBlock *Region::getEnteringBlock() const {
 137   BasicBlock *entry = getEntry();
 138   BasicBlock *Pred;
 139   BasicBlock *enteringBlock = 0;
 140
 141   for (pred_iterator PI = pred_begin(entry), PE = pred_end(entry); PI != PE;
 142        ++PI) {
 143     Pred = *PI;
 144     if (DT->getNode(Pred) && !contains(Pred)) {
 145       if (enteringBlock)
 146         return 0;
 147
 148       enteringBlock = Pred;
 149     }
 150   }
 151
 152   return enteringBlock;
 153 }
 154
 155 BasicBlock *Region::getExitingBlock() const {
 156   BasicBlock *exit = getExit();
 157   BasicBlock *Pred;
 158   BasicBlock *exitingBlock = 0;
 159
 160   if (!exit)
 161     return 0;
 162
 163   for (pred_iterator PI = pred_begin(exit), PE = pred_end(exit); PI != PE;
 164        ++PI) {
 165     Pred = *PI;
 166     if (contains(Pred)) {
 167       if (exitingBlock)
 168         return 0;
 169
 170       exitingBlock = Pred;
 171     }
 172   }
 173
 174   return exitingBlock;
 175 }
 176
 177 bool Region::isSimple() const {
 178   return !isTopLevelRegion() && getEnteringBlock() && getExitingBlock();
 179 }
 180
 181 std::string Region::getNameStr() const {
 182   std::string exitName;
 183   std::string entryName;
 184
 185   if (getEntry()->getName().empty()) {
 186     raw_string_ostream OS(entryName);
 187
 188     WriteAsOperand(OS, getEntry(), false);
 189     entryName = OS.str();
 190   } else
 191     entryName = getEntry()->getNameStr();
 192
 193   if (getExit()) {
 194     if (getExit()->getName().empty()) {
 195       raw_string_ostream OS(exitName);
 196
 197       WriteAsOperand(OS, getExit(), false);
 198       exitName = OS.str();
 199     } else
 200       exitName = getExit()->getNameStr();
 201   } else
 202     exitName = "<Function Return>";
 203
 204   return entryName + " => " + exitName;
 205 }
 206
 207 void Region::verifyBBInRegion(BasicBlock *BB) const {
 208   if (!contains(BB))
 209     llvm_unreachable("Broken region found!");
 210
 211   BasicBlock *entry = getEntry(), *exit = getExit();
 212
 213   for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
 214     if (!contains(*SI) && exit != *SI)
 215       llvm_unreachable("Broken region found!");
 216
 217   if (entry != BB)
 218     for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB); SI != SE; ++SI)
 219       if (!contains(*SI))
 220         llvm_unreachable("Broken region found!");
 221 }
 222
 223 void Region::verifyWalk(BasicBlock *BB, std::set<BasicBlock*> *visited) const {
 224   BasicBlock *exit = getExit();
 225
 226   visited->insert(BB);
 227
 228   verifyBBInRegion(BB);
 229
 230   for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
 231     if (*SI != exit && visited->find(*SI) == visited->end())
 232         verifyWalk(*SI, visited);
 233 }
 234
 235 void Region::verifyRegion() const {
 236   // Only do verification when user wants to, otherwise this expensive
 237   // check will be invoked by PassManager.
 238   if (!VerifyRegionInfo) return;
 239
 240   std::set<BasicBlock*> visited;
 241   verifyWalk(getEntry(), &visited);
 242 }
 243
 244 void Region::verifyRegionNest() const {
 245   for (Region::const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
 246     (*RI)->verifyRegionNest();
 247
 248   verifyRegion();
 249 }
 250
 251 Region::block_iterator Region::block_begin() {
 252   return GraphTraits<FlatIt<Region*> >::nodes_begin(this);
 253 }
 254
 255 Region::block_iterator Region::block_end() {
 256   return GraphTraits<FlatIt<Region*> >::nodes_end(this);
 257 }
 258
 259 Region::const_block_iterator Region::block_begin() const {
 260   return GraphTraits<FlatIt<const Region*> >::nodes_begin(this);
 261 }
 262
 263 Region::const_block_iterator Region::block_end() const {
 264   return GraphTraits<FlatIt<const Region*> >::nodes_end(this);
 265 }
 266
 267 Region::element_iterator Region::element_begin() {
 268   return GraphTraits<Region*>::nodes_begin(this);
 269 }
 270
 271 Region::element_iterator Region::element_end() {
 272   return GraphTraits<Region*>::nodes_end(this);
 273 }
 274
 275 Region::const_element_iterator Region::element_begin() const {
 276   return GraphTraits<const Region*>::nodes_begin(this);
 277 }
 278
 279 Region::const_element_iterator Region::element_end() const {
 280   return GraphTraits<const Region*>::nodes_end(this);
 281 }
 282
 283 Region* Region::getSubRegionNode(BasicBlock *BB) const {
 284   Region *R = RI->getRegionFor(BB);
 285
 286   if (!R || R == this)
 287     return 0;
 288
 289   // If we pass the BB out of this region, that means our code is broken.
 290   assert(contains(R) && "BB not in current region!");
 291
 292   while (contains(R->getParent()) && R->getParent() != this)
 293     R = R->getParent();
 294
 295   if (R->getEntry() != BB)
 296     return 0;
 297
 298   return R;
 299 }
 300
 301 RegionNode* Region::getBBNode(BasicBlock *BB) const {
 302   assert(contains(BB) && "Can get BB node out of this region!");
 303
 304   BBNodeMapT::const_iterator at = BBNodeMap.find(BB);
 305
 306   if (at != BBNodeMap.end())
 307     return at->second;
 308
 309   RegionNode *NewNode = new RegionNode(const_cast<Region*>(this), BB);
 310   BBNodeMap.insert(std::make_pair(BB, NewNode));
 311   return NewNode;
 312 }
 313
 314 RegionNode* Region::getNode(BasicBlock *BB) const {
 315   assert(contains(BB) && "Can get BB node out of this region!");
 316   if (Region* Child = getSubRegionNode(BB))
 317     return Child->getNode();
 318
 319   return getBBNode(BB);
 320 }
 321
 322 void Region::transferChildrenTo(Region *To) {
 323   for (iterator I = begin(), E = end(); I != E; ++I) {
 324     (*I)->parent = To;
 325     To->children.push_back(*I);
 326   }
 327   children.clear();
 328 }
 329
 330 void Region::addSubRegion(Region *SubRegion, bool moveChildren) {
 331   assert(SubRegion->parent == 0 && "SubRegion already has a parent!");
 332   assert(std::find(begin(), end(), SubRegion) == children.end()
 333          && "Subregion already exists!");
 334
 335   SubRegion->parent = this;
 336   children.push_back(SubRegion);
 337
 338   if (!moveChildren)
 339     return;
 340
 341   assert(SubRegion->children.size() == 0
 342          && "SubRegions that contain children are not supported");
 343
 344   for (element_iterator I = element_begin(), E = element_end(); I != E; ++I)
 345     if (!(*I)->isSubRegion()) {
 346       BasicBlock *BB = (*I)->getNodeAs<BasicBlock>();
 347
 348       if (SubRegion->contains(BB))
 349         RI->setRegionFor(BB, SubRegion);
 350     }
 351
 352   std::vector<Region*> Keep;
 353   for (iterator I = begin(), E = end(); I != E; ++I)
 354     if (SubRegion->contains(*I) && *I != SubRegion) {
 355       SubRegion->children.push_back(*I);
 356       (*I)->parent = SubRegion;
 357     } else
 358       Keep.push_back(*I);
 359
 360   children.clear();
 361   children.insert(children.begin(), Keep.begin(), Keep.end());
 362 }
 363
 364
 365 Region *Region::removeSubRegion(Region *Child) {
 366   assert(Child->parent == this && "Child is not a child of this region!");
 367   Child->parent = 0;
 368   RegionSet::iterator I = std::find(children.begin(), children.end(), Child);
 369   assert(I != children.end() && "Region does not exit. Unable to remove.");
 370   children.erase(children.begin()+(I-begin()));
 371   return Child;
 372 }
 373
 374 unsigned Region::getDepth() const {
 375   unsigned Depth = 0;
 376
 377   for (Region *R = parent; R != 0; R = R->parent)
 378     ++Depth;
 379
 380   return Depth;
 381 }
 382
 383 Region *Region::getExpandedRegion() const {
 384   unsigned NumSuccessors = exit->getTerminator()->getNumSuccessors();
 385
 386   if (NumSuccessors == 0)
 387     return NULL;
 388
 389   for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
 390        PI != PE; ++PI)
 391     if (!DT->dominates(getEntry(), *PI))
 392       return NULL;
 393
 394   Region *R = RI->getRegionFor(exit);
 395
 396   if (R->getEntry() != exit) {
 397     if (exit->getTerminator()->getNumSuccessors() == 1)
 398       return new Region(getEntry(), *succ_begin(exit), RI, DT);
 399     else
 400       return NULL;
 401   }
 402
 403   while (R->getParent() && R->getParent()->getEntry() == exit)
 404     R = R->getParent();
 405
 406   if (!DT->dominates(getEntry(), R->getExit()))
 407     for (pred_iterator PI = pred_begin(getExit()), PE = pred_end(getExit());
 408          PI != PE; ++PI)
 409     if (!DT->dominates(R->getExit(), *PI))
 410       return NULL;
 411
 412   return new Region(getEntry(), R->getExit(), RI, DT);
 413 }
 414
 415 void Region::print(raw_ostream &OS, bool print_tree, unsigned level,
 416                    enum PrintStyle Style) const {
 417   if (print_tree)
 418     OS.indent(level*2) << "[" << level << "] " << getNameStr();
 419   else
 420     OS.indent(level*2) << getNameStr();
 421
 422   OS << "\n";
 423
 424
 425   if (Style != PrintNone) {
 426     OS.indent(level*2) << "{\n";
 427     OS.indent(level*2 + 2);
 428
 429     if (Style == PrintBB) {
 430       for (const_block_iterator I = block_begin(), E = block_end(); I!=E; ++I)
 431         OS << **I << ", "; // TODO: remove the last ","
 432     } else if (Style == PrintRN) {
 433       for (const_element_iterator I = element_begin(), E = element_end(); I!=E; ++I)
 434         OS << **I << ", "; // TODO: remove the last ",
 435     }
 436
 437     OS << "\n";
 438   }
 439
 440   if (print_tree)
 441     for (const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
 442       (*RI)->print(OS, print_tree, level+1, Style);
 443
 444   if (Style != PrintNone)
 445     OS.indent(level*2) << "} \n";
 446 }
 447
 448 void Region::dump() const {
 449   print(dbgs(), true, getDepth(), printStyle.getValue());
 450 }
 451
 452 void Region::clearNodeCache() {
 453   // Free the cached nodes.
 454   for (BBNodeMapT::iterator I = BBNodeMap.begin(),
 455        IE = BBNodeMap.end(); I != IE; ++I)
 456     delete I->second;
 457
 458   BBNodeMap.clear();
 459   for (Region::iterator RI = begin(), RE = end(); RI != RE; ++RI)
 460     (*RI)->clearNodeCache();
 461 }
 462
 463 //===----------------------------------------------------------------------===//
 464 // RegionInfo implementation
 465 //
 466
 467 bool RegionInfo::isCommonDomFrontier(BasicBlock *BB, BasicBlock *entry,
 468                                      BasicBlock *exit) const {
 469   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
 470     BasicBlock *P = *PI;
 471     if (DT->dominates(entry, P) && !DT->dominates(exit, P))
 472       return false;
 473   }
 474   return true;
 475 }
 476
 477 bool RegionInfo::isRegion(BasicBlock *entry, BasicBlock *exit) const {
 478   assert(entry && exit && "entry and exit must not be null!");
 479   typedef DominanceFrontier::DomSetType DST;
 480
 481   DST *entrySuccs = &DF->find(entry)->second;
 482
 483   // Exit is the header of a loop that contains the entry. In this case,
 484   // the dominance frontier must only contain the exit.
 485   if (!DT->dominates(entry, exit)) {
 486     for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
 487          SI != SE; ++SI)
 488       if (*SI != exit && *SI != entry)
 489         return false;
 490
 491     return true;
 492   }
 493
 494   DST *exitSuccs = &DF->find(exit)->second;
 495
 496   // Do not allow edges leaving the region.
 497   for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
 498        SI != SE; ++SI) {
 499     if (*SI == exit || *SI == entry)
 500       continue;
 501     if (exitSuccs->find(*SI) == exitSuccs->end())
 502       return false;
 503     if (!isCommonDomFrontier(*SI, entry, exit))
 504       return false;
 505   }
 506
 507   // Do not allow edges pointing into the region.
 508   for (DST::iterator SI = exitSuccs->begin(), SE = exitSuccs->end();
 509        SI != SE; ++SI)
 510     if (DT->properlyDominates(entry, *SI) && *SI != exit)
 511       return false;
 512
 513
 514   return true;
 515 }
 516
 517 void RegionInfo::insertShortCut(BasicBlock *entry, BasicBlock *exit,
 518                              BBtoBBMap *ShortCut) const {
 519   assert(entry && exit && "entry and exit must not be null!");
 520
 521   BBtoBBMap::iterator e = ShortCut->find(exit);
 522
 523   if (e == ShortCut->end())
 524     // No further region at exit available.
 525     (*ShortCut)[entry] = exit;
 526   else {
 527     // We found a region e that starts at exit. Therefore (entry, e->second)
 528     // is also a region, that is larger than (entry, exit). Insert the
 529     // larger one.
 530     BasicBlock *BB = e->second;
 531     (*ShortCut)[entry] = BB;
 532   }
 533 }
 534
 535 DomTreeNode* RegionInfo::getNextPostDom(DomTreeNode* N,
 536                                         BBtoBBMap *ShortCut) const {
 537   BBtoBBMap::iterator e = ShortCut->find(N->getBlock());
 538
 539   if (e == ShortCut->end())
 540     return N->getIDom();
 541
 542   return PDT->getNode(e->second)->getIDom();
 543 }
 544
 545 bool RegionInfo::isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const {
 546   assert(entry && exit && "entry and exit must not be null!");
 547
 548   unsigned num_successors = succ_end(entry) - succ_begin(entry);
 549
 550   if (num_successors <= 1 && exit == *(succ_begin(entry)))
 551     return true;
 552
 553   return false;
 554 }
 555
 556 void RegionInfo::updateStatistics(Region *R) {
 557   ++numRegions;
 558
 559   // TODO: Slow. Should only be enabled if -stats is used.
 560   if (R->isSimple()) ++numSimpleRegions;
 561 }
 562
 563 Region *RegionInfo::createRegion(BasicBlock *entry, BasicBlock *exit) {
 564   assert(entry && exit && "entry and exit must not be null!");
 565
 566   if (isTrivialRegion(entry, exit))
 567     return 0;
 568
 569   Region *region = new Region(entry, exit, this, DT);
 570   BBtoRegion.insert(std::make_pair(entry, region));
 571
 572  #ifdef XDEBUG
 573     region->verifyRegion();
 574  #else
 575     DEBUG(region->verifyRegion());
 576  #endif
 577
 578   updateStatistics(region);
 579   return region;
 580 }
 581
 582 void RegionInfo::findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut) {
 583   assert(entry);
 584
 585   DomTreeNode *N = PDT->getNode(entry);
 586
 587   if (!N)
 588     return;
 589
 590   Region *lastRegion= 0;
 591   BasicBlock *lastExit = entry;
 592
 593   // As only a BasicBlock that postdominates entry can finish a region, walk the
 594   // post dominance tree upwards.
 595   while ((N = getNextPostDom(N, ShortCut))) {
 596     BasicBlock *exit = N->getBlock();
 597
 598     if (!exit)
 599       break;
 600
 601     if (isRegion(entry, exit)) {
 602       Region *newRegion = createRegion(entry, exit);
 603
 604       if (lastRegion)
 605         newRegion->addSubRegion(lastRegion);
 606
 607       lastRegion = newRegion;
 608       lastExit = exit;
 609     }
 610
 611     // This can never be a region, so stop the search.
 612     if (!DT->dominates(entry, exit))
 613       break;
 614   }
 615
 616   // Tried to create regions from entry to lastExit.  Next time take a
 617   // shortcut from entry to lastExit.
 618   if (lastExit != entry)
 619     insertShortCut(entry, lastExit, ShortCut);
 620 }
 621
 622 void RegionInfo::scanForRegions(Function &F, BBtoBBMap *ShortCut) {
 623   BasicBlock *entry = &(F.getEntryBlock());
 624   DomTreeNode *N = DT->getNode(entry);
 625
 626   // Iterate over the dominance tree in post order to start with the small
 627   // regions from the bottom of the dominance tree.  If the small regions are
 628   // detected first, detection of bigger regions is faster, as we can jump
 629   // over the small regions.
 630   for (po_iterator<DomTreeNode*> FI = po_begin(N), FE = po_end(N); FI != FE;
 631     ++FI) {
 632     findRegionsWithEntry(FI->getBlock(), ShortCut);
 633   }
 634 }
 635
 636 Region *RegionInfo::getTopMostParent(Region *region) {
 637   while (region->parent)
 638     region = region->getParent();
 639
 640   return region;
 641 }
 642
 643 void RegionInfo::buildRegionsTree(DomTreeNode *N, Region *region) {
 644   BasicBlock *BB = N->getBlock();
 645
 646   // Passed region exit
 647   while (BB == region->getExit())
 648     region = region->getParent();
 649
 650   BBtoRegionMap::iterator it = BBtoRegion.find(BB);
 651
 652   // This basic block is a start block of a region. It is already in the
 653   // BBtoRegion relation. Only the child basic blocks have to be updated.
 654   if (it != BBtoRegion.end()) {
 655     Region *newRegion = it->second;;
 656     region->addSubRegion(getTopMostParent(newRegion));
 657     region = newRegion;
 658   } else {
 659     BBtoRegion[BB] = region;
 660   }
 661
 662   for (DomTreeNode::iterator CI = N->begin(), CE = N->end(); CI != CE; ++CI)
 663     buildRegionsTree(*CI, region);
 664 }
 665
 666 void RegionInfo::releaseMemory() {
 667   BBtoRegion.clear();
 668   if (TopLevelRegion)
 669     delete TopLevelRegion;
 670   TopLevelRegion = 0;
 671 }
 672
 673 RegionInfo::RegionInfo() : FunctionPass(ID) {
 674   initializeRegionInfoPass(*PassRegistry::getPassRegistry());
 675   TopLevelRegion = 0;
 676 }
 677
 678 RegionInfo::~RegionInfo() {
 679   releaseMemory();
 680 }
 681
 682 void RegionInfo::Calculate(Function &F) {
 683   // ShortCut a function where for every BB the exit of the largest region
 684   // starting with BB is stored. These regions can be threated as single BBS.
 685   // This improves performance on linear CFGs.
 686   BBtoBBMap ShortCut;
 687
 688   scanForRegions(F, &ShortCut);
 689   BasicBlock *BB = &F.getEntryBlock();
 690   buildRegionsTree(DT->getNode(BB), TopLevelRegion);
 691 }
 692
 693 bool RegionInfo::runOnFunction(Function &F) {
 694   releaseMemory();
 695
 696   DT = &getAnalysis<DominatorTree>();
 697   PDT = &getAnalysis<PostDominatorTree>();
 698   DF = &getAnalysis<DominanceFrontier>();
 699
 700   TopLevelRegion = new Region(&F.getEntryBlock(), 0, this, DT, 0);
 701   updateStatistics(TopLevelRegion);
 702
 703   Calculate(F);
 704
 705   return false;
 706 }
 707
 708 void RegionInfo::getAnalysisUsage(AnalysisUsage &AU) const {
 709   AU.setPreservesAll();
 710   AU.addRequiredTransitive<DominatorTree>();
 711   AU.addRequired<PostDominatorTree>();
 712   AU.addRequired<DominanceFrontier>();
 713 }
 714
 715 void RegionInfo::print(raw_ostream &OS, const Module *) const {
 716   OS << "Region tree:\n";
 717   TopLevelRegion->print(OS, true, 0, printStyle.getValue());
 718   OS << "End region tree\n";
 719 }
 720
 721 void RegionInfo::verifyAnalysis() const {
 722   // Only do verification when user wants to, otherwise this expensive check
 723   // will be invoked by PMDataManager::verifyPreservedAnalysis when
 724   // a regionpass (marked PreservedAll) finish.
 725   if (!VerifyRegionInfo) return;
 726
 727   TopLevelRegion->verifyRegionNest();
 728 }
 729
 730 // Region pass manager support.
 731 Region *RegionInfo::getRegionFor(BasicBlock *BB) const {
 732   BBtoRegionMap::const_iterator I=
 733     BBtoRegion.find(BB);
 734   return I != BBtoRegion.end() ? I->second : 0;
 735 }
 736
 737 void RegionInfo::setRegionFor(BasicBlock *BB, Region *R) {
 738   BBtoRegion[BB] = R;
 739 }
 740
 741 Region *RegionInfo::operator[](BasicBlock *BB) const {
 742   return getRegionFor(BB);
 743 }
 744
 745 BasicBlock *RegionInfo::getMaxRegionExit(BasicBlock *BB) const {
 746   BasicBlock *Exit = NULL;
 747
 748   while (true) {
 749     // Get largest region that starts at BB.
 750     Region *R = getRegionFor(BB);
 751     while (R && R->getParent() && R->getParent()->getEntry() == BB)
 752       R = R->getParent();
 753
 754     // Get the single exit of BB.
 755     if (R && R->getEntry() == BB)
 756       Exit = R->getExit();
 757     else if (++succ_begin(BB) == succ_end(BB))
 758       Exit = *succ_begin(BB);
 759     else // No single exit exists.
 760       return Exit;
 761
 762     // Get largest region that starts at Exit.
 763     Region *ExitR = getRegionFor(Exit);
 764     while (ExitR && ExitR->getParent()
 765            && ExitR->getParent()->getEntry() == Exit)
 766       ExitR = ExitR->getParent();
 767
 768     for (pred_iterator PI = pred_begin(Exit), PE = pred_end(Exit); PI != PE;
 769          ++PI)
 770       if (!R->contains(*PI) && !ExitR->contains(*PI))
 771         break;
 772
 773     // This stops infinite cycles.
 774     if (DT->dominates(Exit, BB))
 775       break;
 776
 777     BB = Exit;
 778   }
 779
 780   return Exit;
 781 }
 782
 783 Region*
 784 RegionInfo::getCommonRegion(Region *A, Region *B) const {
 785   assert (A && B && "One of the Regions is NULL");
 786
 787   if (A->contains(B)) return A;
 788
 789   while (!B->contains(A))
 790     B = B->getParent();
 791
 792   return B;
 793 }
 794
 795 Region*
 796 RegionInfo::getCommonRegion(SmallVectorImpl<Region*> &Regions) const {
 797   Region* ret = Regions.back();
 798   Regions.pop_back();
 799
 800   for (SmallVectorImpl<Region*>::const_iterator I = Regions.begin(),
 801        E = Regions.end(); I != E; ++I)
 802       ret = getCommonRegion(ret, *I);
 803
 804   return ret;
 805 }
 806
 807 Region*
 808 RegionInfo::getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const {
 809   Region* ret = getRegionFor(BBs.back());
 810   BBs.pop_back();
 811
 812   for (SmallVectorImpl<BasicBlock*>::const_iterator I = BBs.begin(),
 813        E = BBs.end(); I != E; ++I)
 814       ret = getCommonRegion(ret, getRegionFor(*I));
 815
 816   return ret;
 817 }
 818
 819 void RegionInfo::splitBlock(BasicBlock* NewBB, BasicBlock *OldBB)
 820 {
 821   Region *R = getRegionFor(OldBB);
 822
 823   setRegionFor(NewBB, R);
 824
 825   while (R->getEntry() == OldBB && !R->isTopLevelRegion()) {
 826     R->replaceEntry(NewBB);
 827     R = R->getParent();
 828   }
 829
 830   setRegionFor(OldBB, R);
 831 }
 832
 833 char RegionInfo::ID = 0;
 834 INITIALIZE_PASS_BEGIN(RegionInfo, "regions",
 835                 "Detect single entry single exit regions", true, true)
 836 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
 837 INITIALIZE_PASS_DEPENDENCY(PostDominatorTree)
 838 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
 839 INITIALIZE_PASS_END(RegionInfo, "regions",
 840                 "Detect single entry single exit regions", true, true)
 841
 842 // Create methods available outside of this file, to use them
 843 // "include/llvm/LinkAllPasses.h". Otherwise the pass would be deleted by
 844 // the link time optimization.
 845
 846 namespace llvm {
 847   FunctionPass *createRegionInfoPass() {
 848     return new RegionInfo();
 849   }
 850 }
 851