Dominators.h revision 70b2bee8e7dda22d70475bf748385654559a0ef8
1//===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- C++ -*-===// 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// 10// This file defines the following classes: 11// 1. DominatorTree: Represent dominators as an explicit tree structure. 12// 2. DominanceFrontier: Calculate and hold the dominance frontier for a 13// function. 14// 15// These data structures are listed in increasing order of complexity. It 16// takes longer to calculate the dominator frontier, for example, than the 17// DominatorTree mapping. 18// 19//===----------------------------------------------------------------------===// 20 21#ifndef LLVM_ANALYSIS_DOMINATORS_H 22#define LLVM_ANALYSIS_DOMINATORS_H 23 24#include "llvm/Pass.h" 25#include "llvm/Function.h" 26#include "llvm/Instructions.h" 27#include "llvm/ADT/DenseMap.h" 28#include "llvm/ADT/DepthFirstIterator.h" 29#include "llvm/ADT/GraphTraits.h" 30#include "llvm/ADT/SmallPtrSet.h" 31#include "llvm/ADT/SmallVector.h" 32#include "llvm/Assembly/Writer.h" 33#include "llvm/Support/CFG.h" 34#include "llvm/Support/Compiler.h" 35#include "llvm/Support/raw_ostream.h" 36#include <algorithm> 37#include <map> 38#include <set> 39 40namespace llvm { 41 42//===----------------------------------------------------------------------===// 43/// DominatorBase - Base class that other, more interesting dominator analyses 44/// inherit from. 45/// 46template <class NodeT> 47class DominatorBase { 48protected: 49 std::vector<NodeT*> Roots; 50 const bool IsPostDominators; 51 inline explicit DominatorBase(bool isPostDom) : 52 Roots(), IsPostDominators(isPostDom) {} 53public: 54 55 /// getRoots - Return the root blocks of the current CFG. This may include 56 /// multiple blocks if we are computing post dominators. For forward 57 /// dominators, this will always be a single block (the entry node). 58 /// 59 inline const std::vector<NodeT*> &getRoots() const { return Roots; } 60 61 /// isPostDominator - Returns true if analysis based of postdoms 62 /// 63 bool isPostDominator() const { return IsPostDominators; } 64}; 65 66 67//===----------------------------------------------------------------------===// 68// DomTreeNode - Dominator Tree Node 69template<class NodeT> class DominatorTreeBase; 70struct PostDominatorTree; 71class MachineBasicBlock; 72 73template <class NodeT> 74class DomTreeNodeBase { 75 NodeT *TheBB; 76 DomTreeNodeBase<NodeT> *IDom; 77 std::vector<DomTreeNodeBase<NodeT> *> Children; 78 int DFSNumIn, DFSNumOut; 79 80 template<class N> friend class DominatorTreeBase; 81 friend struct PostDominatorTree; 82public: 83 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator; 84 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator 85 const_iterator; 86 87 iterator begin() { return Children.begin(); } 88 iterator end() { return Children.end(); } 89 const_iterator begin() const { return Children.begin(); } 90 const_iterator end() const { return Children.end(); } 91 92 NodeT *getBlock() const { return TheBB; } 93 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; } 94 const std::vector<DomTreeNodeBase<NodeT>*> &getChildren() const { 95 return Children; 96 } 97 98 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom) 99 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { } 100 101 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) { 102 Children.push_back(C); 103 return C; 104 } 105 106 size_t getNumChildren() const { 107 return Children.size(); 108 } 109 110 void clearAllChildren() { 111 Children.clear(); 112 } 113 114 bool compare(DomTreeNodeBase<NodeT> *Other) { 115 if (getNumChildren() != Other->getNumChildren()) 116 return true; 117 118 SmallPtrSet<NodeT *, 4> OtherChildren; 119 for(iterator I = Other->begin(), E = Other->end(); I != E; ++I) { 120 NodeT *Nd = (*I)->getBlock(); 121 OtherChildren.insert(Nd); 122 } 123 124 for(iterator I = begin(), E = end(); I != E; ++I) { 125 NodeT *N = (*I)->getBlock(); 126 if (OtherChildren.count(N) == 0) 127 return true; 128 } 129 return false; 130 } 131 132 void setIDom(DomTreeNodeBase<NodeT> *NewIDom) { 133 assert(IDom && "No immediate dominator?"); 134 if (IDom != NewIDom) { 135 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I = 136 std::find(IDom->Children.begin(), IDom->Children.end(), this); 137 assert(I != IDom->Children.end() && 138 "Not in immediate dominator children set!"); 139 // I am no longer your child... 140 IDom->Children.erase(I); 141 142 // Switch to new dominator 143 IDom = NewIDom; 144 IDom->Children.push_back(this); 145 } 146 } 147 148 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do 149 /// not call them. 150 unsigned getDFSNumIn() const { return DFSNumIn; } 151 unsigned getDFSNumOut() const { return DFSNumOut; } 152private: 153 // Return true if this node is dominated by other. Use this only if DFS info 154 // is valid. 155 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const { 156 return this->DFSNumIn >= other->DFSNumIn && 157 this->DFSNumOut <= other->DFSNumOut; 158 } 159}; 160 161EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<BasicBlock>); 162EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<MachineBasicBlock>); 163 164template<class NodeT> 165static raw_ostream &operator<<(raw_ostream &o, 166 const DomTreeNodeBase<NodeT> *Node) { 167 if (Node->getBlock()) 168 WriteAsOperand(o, Node->getBlock(), false); 169 else 170 o << " <<exit node>>"; 171 172 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}"; 173 174 return o << "\n"; 175} 176 177template<class NodeT> 178static void PrintDomTree(const DomTreeNodeBase<NodeT> *N, raw_ostream &o, 179 unsigned Lev) { 180 o.indent(2*Lev) << "[" << Lev << "] " << N; 181 for (typename DomTreeNodeBase<NodeT>::const_iterator I = N->begin(), 182 E = N->end(); I != E; ++I) 183 PrintDomTree<NodeT>(*I, o, Lev+1); 184} 185 186typedef DomTreeNodeBase<BasicBlock> DomTreeNode; 187 188//===----------------------------------------------------------------------===// 189/// DominatorTree - Calculate the immediate dominator tree for a function. 190/// 191 192template<class FuncT, class N> 193void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT, 194 FuncT& F); 195 196template<class NodeT> 197class DominatorTreeBase : public DominatorBase<NodeT> { 198protected: 199 typedef DenseMap<NodeT*, DomTreeNodeBase<NodeT>*> DomTreeNodeMapType; 200 DomTreeNodeMapType DomTreeNodes; 201 DomTreeNodeBase<NodeT> *RootNode; 202 203 bool DFSInfoValid; 204 unsigned int SlowQueries; 205 // Information record used during immediate dominators computation. 206 struct InfoRec { 207 unsigned DFSNum; 208 unsigned Semi; 209 unsigned Size; 210 NodeT *Label, *Child; 211 unsigned Parent, Ancestor; 212 213 std::vector<NodeT*> Bucket; 214 215 InfoRec() : DFSNum(0), Semi(0), Size(0), Label(0), Child(0), Parent(0), 216 Ancestor(0) {} 217 }; 218 219 DenseMap<NodeT*, NodeT*> IDoms; 220 221 // Vertex - Map the DFS number to the BasicBlock* 222 std::vector<NodeT*> Vertex; 223 224 // Info - Collection of information used during the computation of idoms. 225 DenseMap<NodeT*, InfoRec> Info; 226 227 void reset() { 228 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(), 229 E = DomTreeNodes.end(); I != E; ++I) 230 delete I->second; 231 DomTreeNodes.clear(); 232 IDoms.clear(); 233 this->Roots.clear(); 234 Vertex.clear(); 235 RootNode = 0; 236 } 237 238 // NewBB is split and now it has one successor. Update dominator tree to 239 // reflect this change. 240 template<class N, class GraphT> 241 void Split(DominatorTreeBase<typename GraphT::NodeType>& DT, 242 typename GraphT::NodeType* NewBB) { 243 assert(std::distance(GraphT::child_begin(NewBB), GraphT::child_end(NewBB)) == 1 244 && "NewBB should have a single successor!"); 245 typename GraphT::NodeType* NewBBSucc = *GraphT::child_begin(NewBB); 246 247 std::vector<typename GraphT::NodeType*> PredBlocks; 248 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI = 249 GraphTraits<Inverse<N> >::child_begin(NewBB), 250 PE = GraphTraits<Inverse<N> >::child_end(NewBB); PI != PE; ++PI) 251 PredBlocks.push_back(*PI); 252 253 assert(!PredBlocks.empty() && "No predblocks??"); 254 255 bool NewBBDominatesNewBBSucc = true; 256 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI = 257 GraphTraits<Inverse<N> >::child_begin(NewBBSucc), 258 E = GraphTraits<Inverse<N> >::child_end(NewBBSucc); PI != E; ++PI) 259 if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI) && 260 DT.isReachableFromEntry(*PI)) { 261 NewBBDominatesNewBBSucc = false; 262 break; 263 } 264 265 // Find NewBB's immediate dominator and create new dominator tree node for 266 // NewBB. 267 NodeT *NewBBIDom = 0; 268 unsigned i = 0; 269 for (i = 0; i < PredBlocks.size(); ++i) 270 if (DT.isReachableFromEntry(PredBlocks[i])) { 271 NewBBIDom = PredBlocks[i]; 272 break; 273 } 274 275 // It's possible that none of the predecessors of NewBB are reachable; 276 // in that case, NewBB itself is unreachable, so nothing needs to be 277 // changed. 278 if (!NewBBIDom) 279 return; 280 281 for (i = i + 1; i < PredBlocks.size(); ++i) { 282 if (DT.isReachableFromEntry(PredBlocks[i])) 283 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]); 284 } 285 286 // Create the new dominator tree node... and set the idom of NewBB. 287 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom); 288 289 // If NewBB strictly dominates other blocks, then it is now the immediate 290 // dominator of NewBBSucc. Update the dominator tree as appropriate. 291 if (NewBBDominatesNewBBSucc) { 292 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc); 293 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode); 294 } 295 } 296 297public: 298 explicit DominatorTreeBase(bool isPostDom) 299 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {} 300 virtual ~DominatorTreeBase() { reset(); } 301 302 // FIXME: Should remove this 303 virtual bool runOnFunction(Function &F) { return false; } 304 305 /// compare - Return false if the other dominator tree base matches this 306 /// dominator tree base. Otherwise return true. 307 bool compare(DominatorTreeBase &Other) const { 308 309 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes; 310 if (DomTreeNodes.size() != OtherDomTreeNodes.size()) 311 return true; 312 313 SmallPtrSet<const NodeT *,4> MyBBs; 314 for (typename DomTreeNodeMapType::const_iterator 315 I = this->DomTreeNodes.begin(), 316 E = this->DomTreeNodes.end(); I != E; ++I) { 317 NodeT *BB = I->first; 318 typename DomTreeNodeMapType::const_iterator OI = OtherDomTreeNodes.find(BB); 319 if (OI == OtherDomTreeNodes.end()) 320 return true; 321 322 DomTreeNodeBase<NodeT>* MyNd = I->second; 323 DomTreeNodeBase<NodeT>* OtherNd = OI->second; 324 325 if (MyNd->compare(OtherNd)) 326 return true; 327 } 328 329 return false; 330 } 331 332 virtual void releaseMemory() { reset(); } 333 334 /// getNode - return the (Post)DominatorTree node for the specified basic 335 /// block. This is the same as using operator[] on this class. 336 /// 337 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const { 338 typename DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB); 339 return I != DomTreeNodes.end() ? I->second : 0; 340 } 341 342 /// getRootNode - This returns the entry node for the CFG of the function. If 343 /// this tree represents the post-dominance relations for a function, however, 344 /// this root may be a node with the block == NULL. This is the case when 345 /// there are multiple exit nodes from a particular function. Consumers of 346 /// post-dominance information must be capable of dealing with this 347 /// possibility. 348 /// 349 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; } 350 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; } 351 352 /// properlyDominates - Returns true iff this dominates N and this != N. 353 /// Note that this is not a constant time operation! 354 /// 355 bool properlyDominates(const DomTreeNodeBase<NodeT> *A, 356 const DomTreeNodeBase<NodeT> *B) const { 357 if (A == 0 || B == 0) return false; 358 return dominatedBySlowTreeWalk(A, B); 359 } 360 361 inline bool properlyDominates(NodeT *A, NodeT *B) { 362 return properlyDominates(getNode(A), getNode(B)); 363 } 364 365 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A, 366 const DomTreeNodeBase<NodeT> *B) const { 367 const DomTreeNodeBase<NodeT> *IDom; 368 if (A == 0 || B == 0) return false; 369 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B) 370 B = IDom; // Walk up the tree 371 return IDom != 0; 372 } 373 374 375 /// isReachableFromEntry - Return true if A is dominated by the entry 376 /// block of the function containing it. 377 bool isReachableFromEntry(NodeT* A) { 378 assert (!this->isPostDominator() 379 && "This is not implemented for post dominators"); 380 return dominates(&A->getParent()->front(), A); 381 } 382 383 /// dominates - Returns true iff A dominates B. Note that this is not a 384 /// constant time operation! 385 /// 386 inline bool dominates(const DomTreeNodeBase<NodeT> *A, 387 const DomTreeNodeBase<NodeT> *B) { 388 if (B == A) 389 return true; // A node trivially dominates itself. 390 391 if (A == 0 || B == 0) 392 return false; 393 394 if (DFSInfoValid) 395 return B->DominatedBy(A); 396 397 // If we end up with too many slow queries, just update the 398 // DFS numbers on the theory that we are going to keep querying. 399 SlowQueries++; 400 if (SlowQueries > 32) { 401 updateDFSNumbers(); 402 return B->DominatedBy(A); 403 } 404 405 return dominatedBySlowTreeWalk(A, B); 406 } 407 408 inline bool dominates(const NodeT *A, const NodeT *B) { 409 if (A == B) 410 return true; 411 412 // Cast away the const qualifiers here. This is ok since 413 // this function doesn't actually return the values returned 414 // from getNode. 415 return dominates(getNode(const_cast<NodeT *>(A)), 416 getNode(const_cast<NodeT *>(B))); 417 } 418 419 NodeT *getRoot() const { 420 assert(this->Roots.size() == 1 && "Should always have entry node!"); 421 return this->Roots[0]; 422 } 423 424 /// findNearestCommonDominator - Find nearest common dominator basic block 425 /// for basic block A and B. If there is no such block then return NULL. 426 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) { 427 428 assert (!this->isPostDominator() 429 && "This is not implemented for post dominators"); 430 assert (A->getParent() == B->getParent() 431 && "Two blocks are not in same function"); 432 433 // If either A or B is a entry block then it is nearest common dominator. 434 NodeT &Entry = A->getParent()->front(); 435 if (A == &Entry || B == &Entry) 436 return &Entry; 437 438 // If B dominates A then B is nearest common dominator. 439 if (dominates(B, A)) 440 return B; 441 442 // If A dominates B then A is nearest common dominator. 443 if (dominates(A, B)) 444 return A; 445 446 DomTreeNodeBase<NodeT> *NodeA = getNode(A); 447 DomTreeNodeBase<NodeT> *NodeB = getNode(B); 448 449 // Collect NodeA dominators set. 450 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms; 451 NodeADoms.insert(NodeA); 452 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom(); 453 while (IDomA) { 454 NodeADoms.insert(IDomA); 455 IDomA = IDomA->getIDom(); 456 } 457 458 // Walk NodeB immediate dominators chain and find common dominator node. 459 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom(); 460 while(IDomB) { 461 if (NodeADoms.count(IDomB) != 0) 462 return IDomB->getBlock(); 463 464 IDomB = IDomB->getIDom(); 465 } 466 467 return NULL; 468 } 469 470 //===--------------------------------------------------------------------===// 471 // API to update (Post)DominatorTree information based on modifications to 472 // the CFG... 473 474 /// addNewBlock - Add a new node to the dominator tree information. This 475 /// creates a new node as a child of DomBB dominator node,linking it into 476 /// the children list of the immediate dominator. 477 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) { 478 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 479 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB); 480 assert(IDomNode && "Not immediate dominator specified for block!"); 481 DFSInfoValid = false; 482 return DomTreeNodes[BB] = 483 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode)); 484 } 485 486 /// changeImmediateDominator - This method is used to update the dominator 487 /// tree information when a node's immediate dominator changes. 488 /// 489 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N, 490 DomTreeNodeBase<NodeT> *NewIDom) { 491 assert(N && NewIDom && "Cannot change null node pointers!"); 492 DFSInfoValid = false; 493 N->setIDom(NewIDom); 494 } 495 496 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) { 497 changeImmediateDominator(getNode(BB), getNode(NewBB)); 498 } 499 500 /// eraseNode - Removes a node from the dominator tree. Block must not 501 /// domiante any other blocks. Removes node from its immediate dominator's 502 /// children list. Deletes dominator node associated with basic block BB. 503 void eraseNode(NodeT *BB) { 504 DomTreeNodeBase<NodeT> *Node = getNode(BB); 505 assert (Node && "Removing node that isn't in dominator tree."); 506 assert (Node->getChildren().empty() && "Node is not a leaf node."); 507 508 // Remove node from immediate dominator's children list. 509 DomTreeNodeBase<NodeT> *IDom = Node->getIDom(); 510 if (IDom) { 511 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I = 512 std::find(IDom->Children.begin(), IDom->Children.end(), Node); 513 assert(I != IDom->Children.end() && 514 "Not in immediate dominator children set!"); 515 // I am no longer your child... 516 IDom->Children.erase(I); 517 } 518 519 DomTreeNodes.erase(BB); 520 delete Node; 521 } 522 523 /// removeNode - Removes a node from the dominator tree. Block must not 524 /// dominate any other blocks. Invalidates any node pointing to removed 525 /// block. 526 void removeNode(NodeT *BB) { 527 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 528 DomTreeNodes.erase(BB); 529 } 530 531 /// splitBlock - BB is split and now it has one successor. Update dominator 532 /// tree to reflect this change. 533 void splitBlock(NodeT* NewBB) { 534 if (this->IsPostDominators) 535 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB); 536 else 537 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB); 538 } 539 540 /// print - Convert to human readable form 541 /// 542 void print(raw_ostream &o) const { 543 o << "=============================--------------------------------\n"; 544 if (this->isPostDominator()) 545 o << "Inorder PostDominator Tree: "; 546 else 547 o << "Inorder Dominator Tree: "; 548 if (this->DFSInfoValid) 549 o << "DFSNumbers invalid: " << SlowQueries << " slow queries."; 550 o << "\n"; 551 552 // The postdom tree can have a null root if there are no returns. 553 if (getRootNode()) 554 PrintDomTree<NodeT>(getRootNode(), o, 1); 555 } 556 557protected: 558 template<class GraphT> 559 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT, 560 typename GraphT::NodeType* VIn); 561 562 template<class GraphT> 563 friend typename GraphT::NodeType* Eval( 564 DominatorTreeBase<typename GraphT::NodeType>& DT, 565 typename GraphT::NodeType* V); 566 567 template<class GraphT> 568 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT, 569 unsigned DFSNumV, typename GraphT::NodeType* W, 570 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo); 571 572 template<class GraphT> 573 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT, 574 typename GraphT::NodeType* V, 575 unsigned N); 576 577 template<class FuncT, class N> 578 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT, 579 FuncT& F); 580 581 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking 582 /// dominator tree in dfs order. 583 void updateDFSNumbers() { 584 unsigned DFSNum = 0; 585 586 SmallVector<std::pair<DomTreeNodeBase<NodeT>*, 587 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack; 588 589 for (unsigned i = 0, e = (unsigned)this->Roots.size(); i != e; ++i) { 590 DomTreeNodeBase<NodeT> *ThisRoot = getNode(this->Roots[i]); 591 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin())); 592 ThisRoot->DFSNumIn = DFSNum++; 593 594 while (!WorkStack.empty()) { 595 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first; 596 typename DomTreeNodeBase<NodeT>::iterator ChildIt = 597 WorkStack.back().second; 598 599 // If we visited all of the children of this node, "recurse" back up the 600 // stack setting the DFOutNum. 601 if (ChildIt == Node->end()) { 602 Node->DFSNumOut = DFSNum++; 603 WorkStack.pop_back(); 604 } else { 605 // Otherwise, recursively visit this child. 606 DomTreeNodeBase<NodeT> *Child = *ChildIt; 607 ++WorkStack.back().second; 608 609 WorkStack.push_back(std::make_pair(Child, Child->begin())); 610 Child->DFSNumIn = DFSNum++; 611 } 612 } 613 } 614 615 SlowQueries = 0; 616 DFSInfoValid = true; 617 } 618 619 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) { 620 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB); 621 if (I != this->DomTreeNodes.end() && I->second) 622 return I->second; 623 624 // Haven't calculated this node yet? Get or calculate the node for the 625 // immediate dominator. 626 NodeT *IDom = getIDom(BB); 627 628 assert(IDom || this->DomTreeNodes[NULL]); 629 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom); 630 631 // Add a new tree node for this BasicBlock, and link it as a child of 632 // IDomNode 633 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode); 634 return this->DomTreeNodes[BB] = IDomNode->addChild(C); 635 } 636 637 inline NodeT *getIDom(NodeT *BB) const { 638 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB); 639 return I != IDoms.end() ? I->second : 0; 640 } 641 642 inline void addRoot(NodeT* BB) { 643 this->Roots.push_back(BB); 644 } 645 646public: 647 /// recalculate - compute a dominator tree for the given function 648 template<class FT> 649 void recalculate(FT& F) { 650 if (!this->IsPostDominators) { 651 reset(); 652 653 // Initialize roots 654 this->Roots.push_back(&F.front()); 655 this->IDoms[&F.front()] = 0; 656 this->DomTreeNodes[&F.front()] = 0; 657 this->Vertex.push_back(0); 658 659 Calculate<FT, NodeT*>(*this, F); 660 661 updateDFSNumbers(); 662 } else { 663 reset(); // Reset from the last time we were run... 664 665 // Initialize the roots list 666 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) { 667 if (std::distance(GraphTraits<FT*>::child_begin(I), 668 GraphTraits<FT*>::child_end(I)) == 0) 669 addRoot(I); 670 671 // Prepopulate maps so that we don't get iterator invalidation issues later. 672 this->IDoms[I] = 0; 673 this->DomTreeNodes[I] = 0; 674 } 675 676 this->Vertex.push_back(0); 677 678 Calculate<FT, Inverse<NodeT*> >(*this, F); 679 } 680 } 681}; 682 683EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>); 684 685//===------------------------------------- 686/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 687/// compute a normal dominator tree. 688/// 689class DominatorTree : public FunctionPass { 690public: 691 static char ID; // Pass ID, replacement for typeid 692 DominatorTreeBase<BasicBlock>* DT; 693 694 DominatorTree() : FunctionPass(&ID) { 695 DT = new DominatorTreeBase<BasicBlock>(false); 696 } 697 698 ~DominatorTree() { 699 DT->releaseMemory(); 700 delete DT; 701 } 702 703 DominatorTreeBase<BasicBlock>& getBase() { return *DT; } 704 705 /// getRoots - Return the root blocks of the current CFG. This may include 706 /// multiple blocks if we are computing post dominators. For forward 707 /// dominators, this will always be a single block (the entry node). 708 /// 709 inline const std::vector<BasicBlock*> &getRoots() const { 710 return DT->getRoots(); 711 } 712 713 inline BasicBlock *getRoot() const { 714 return DT->getRoot(); 715 } 716 717 inline DomTreeNode *getRootNode() const { 718 return DT->getRootNode(); 719 } 720 721 /// compare - Return false if the other dominator tree matches this 722 /// dominator tree. Otherwise return true. 723 inline bool compare(DominatorTree &Other) const { 724 DomTreeNode *R = getRootNode(); 725 DomTreeNode *OtherR = Other.getRootNode(); 726 727 if (!R || !OtherR || R->getBlock() != OtherR->getBlock()) 728 return true; 729 730 if (DT->compare(Other.getBase())) 731 return true; 732 733 return false; 734 } 735 736 virtual bool runOnFunction(Function &F); 737 738 virtual void verifyAnalysis() const; 739 740 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 741 AU.setPreservesAll(); 742 } 743 744 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const { 745 return DT->dominates(A, B); 746 } 747 748 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const { 749 return DT->dominates(A, B); 750 } 751 752 // dominates - Return true if A dominates B. This performs the 753 // special checks necessary if A and B are in the same basic block. 754 bool dominates(const Instruction *A, const Instruction *B) const; 755 756 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const { 757 return DT->properlyDominates(A, B); 758 } 759 760 bool properlyDominates(BasicBlock *A, BasicBlock *B) const { 761 return DT->properlyDominates(A, B); 762 } 763 764 /// findNearestCommonDominator - Find nearest common dominator basic block 765 /// for basic block A and B. If there is no such block then return NULL. 766 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) { 767 return DT->findNearestCommonDominator(A, B); 768 } 769 770 inline DomTreeNode *operator[](BasicBlock *BB) const { 771 return DT->getNode(BB); 772 } 773 774 /// getNode - return the (Post)DominatorTree node for the specified basic 775 /// block. This is the same as using operator[] on this class. 776 /// 777 inline DomTreeNode *getNode(BasicBlock *BB) const { 778 return DT->getNode(BB); 779 } 780 781 /// addNewBlock - Add a new node to the dominator tree information. This 782 /// creates a new node as a child of DomBB dominator node,linking it into 783 /// the children list of the immediate dominator. 784 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 785 return DT->addNewBlock(BB, DomBB); 786 } 787 788 /// changeImmediateDominator - This method is used to update the dominator 789 /// tree information when a node's immediate dominator changes. 790 /// 791 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) { 792 DT->changeImmediateDominator(N, NewIDom); 793 } 794 795 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) { 796 DT->changeImmediateDominator(N, NewIDom); 797 } 798 799 /// eraseNode - Removes a node from the dominator tree. Block must not 800 /// domiante any other blocks. Removes node from its immediate dominator's 801 /// children list. Deletes dominator node associated with basic block BB. 802 inline void eraseNode(BasicBlock *BB) { 803 DT->eraseNode(BB); 804 } 805 806 /// splitBlock - BB is split and now it has one successor. Update dominator 807 /// tree to reflect this change. 808 inline void splitBlock(BasicBlock* NewBB) { 809 DT->splitBlock(NewBB); 810 } 811 812 bool isReachableFromEntry(BasicBlock* A) { 813 return DT->isReachableFromEntry(A); 814 } 815 816 817 virtual void releaseMemory() { 818 DT->releaseMemory(); 819 } 820 821 virtual void print(raw_ostream &OS, const Module* M= 0) const; 822}; 823 824//===------------------------------------- 825/// DominatorTree GraphTraits specialization so the DominatorTree can be 826/// iterable by generic graph iterators. 827/// 828template <> struct GraphTraits<DomTreeNode*> { 829 typedef DomTreeNode NodeType; 830 typedef NodeType::iterator ChildIteratorType; 831 832 static NodeType *getEntryNode(NodeType *N) { 833 return N; 834 } 835 static inline ChildIteratorType child_begin(NodeType *N) { 836 return N->begin(); 837 } 838 static inline ChildIteratorType child_end(NodeType *N) { 839 return N->end(); 840 } 841 842 typedef df_iterator<DomTreeNode*> nodes_iterator; 843 844 static nodes_iterator nodes_begin(DomTreeNode *N) { 845 return df_begin(getEntryNode(N)); 846 } 847 848 static nodes_iterator nodes_end(DomTreeNode *N) { 849 return df_end(getEntryNode(N)); 850 } 851}; 852 853template <> struct GraphTraits<DominatorTree*> 854 : public GraphTraits<DomTreeNode*> { 855 static NodeType *getEntryNode(DominatorTree *DT) { 856 return DT->getRootNode(); 857 } 858 859 static nodes_iterator nodes_begin(DominatorTree *N) { 860 return df_begin(getEntryNode(N)); 861 } 862 863 static nodes_iterator nodes_end(DominatorTree *N) { 864 return df_end(getEntryNode(N)); 865 } 866}; 867 868 869//===----------------------------------------------------------------------===// 870/// DominanceFrontierBase - Common base class for computing forward and inverse 871/// dominance frontiers for a function. 872/// 873class DominanceFrontierBase : public FunctionPass { 874public: 875 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 876 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 877protected: 878 DomSetMapType Frontiers; 879 std::vector<BasicBlock*> Roots; 880 const bool IsPostDominators; 881 882public: 883 DominanceFrontierBase(void *ID, bool isPostDom) 884 : FunctionPass(ID), IsPostDominators(isPostDom) {} 885 886 /// getRoots - Return the root blocks of the current CFG. This may include 887 /// multiple blocks if we are computing post dominators. For forward 888 /// dominators, this will always be a single block (the entry node). 889 /// 890 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 891 892 /// isPostDominator - Returns true if analysis based of postdoms 893 /// 894 bool isPostDominator() const { return IsPostDominators; } 895 896 virtual void releaseMemory() { Frontiers.clear(); } 897 898 // Accessor interface: 899 typedef DomSetMapType::iterator iterator; 900 typedef DomSetMapType::const_iterator const_iterator; 901 iterator begin() { return Frontiers.begin(); } 902 const_iterator begin() const { return Frontiers.begin(); } 903 iterator end() { return Frontiers.end(); } 904 const_iterator end() const { return Frontiers.end(); } 905 iterator find(BasicBlock *B) { return Frontiers.find(B); } 906 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 907 908 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 909 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 910 return Frontiers.insert(std::make_pair(BB, frontier)).first; 911 } 912 913 /// removeBlock - Remove basic block BB's frontier. 914 void removeBlock(BasicBlock *BB) { 915 assert(find(BB) != end() && "Block is not in DominanceFrontier!"); 916 for (iterator I = begin(), E = end(); I != E; ++I) 917 I->second.erase(BB); 918 Frontiers.erase(BB); 919 } 920 921 void addToFrontier(iterator I, BasicBlock *Node) { 922 assert(I != end() && "BB is not in DominanceFrontier!"); 923 I->second.insert(Node); 924 } 925 926 void removeFromFrontier(iterator I, BasicBlock *Node) { 927 assert(I != end() && "BB is not in DominanceFrontier!"); 928 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 929 I->second.erase(Node); 930 } 931 932 /// compareDomSet - Return false if two domsets match. Otherwise 933 /// return true; 934 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const { 935 std::set<BasicBlock *> tmpSet; 936 for (DomSetType::const_iterator I = DS2.begin(), 937 E = DS2.end(); I != E; ++I) 938 tmpSet.insert(*I); 939 940 for (DomSetType::const_iterator I = DS1.begin(), 941 E = DS1.end(); I != E; ) { 942 BasicBlock *Node = *I++; 943 944 if (tmpSet.erase(Node) == 0) 945 // Node is in DS1 but not in DS2. 946 return true; 947 } 948 949 if(!tmpSet.empty()) 950 // There are nodes that are in DS2 but not in DS1. 951 return true; 952 953 // DS1 and DS2 matches. 954 return false; 955 } 956 957 /// compare - Return true if the other dominance frontier base matches 958 /// this dominance frontier base. Otherwise return false. 959 bool compare(DominanceFrontierBase &Other) const { 960 DomSetMapType tmpFrontiers; 961 for (DomSetMapType::const_iterator I = Other.begin(), 962 E = Other.end(); I != E; ++I) 963 tmpFrontiers.insert(std::make_pair(I->first, I->second)); 964 965 for (DomSetMapType::iterator I = tmpFrontiers.begin(), 966 E = tmpFrontiers.end(); I != E; ) { 967 BasicBlock *Node = I->first; 968 const_iterator DFI = find(Node); 969 if (DFI == end()) 970 return true; 971 972 if (compareDomSet(I->second, DFI->second)) 973 return true; 974 975 ++I; 976 tmpFrontiers.erase(Node); 977 } 978 979 if (!tmpFrontiers.empty()) 980 return true; 981 982 return false; 983 } 984 985 /// print - Convert to human readable form 986 /// 987 virtual void print(raw_ostream &OS, const Module* = 0) const; 988}; 989 990 991//===------------------------------------- 992/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 993/// used to compute a forward dominator frontiers. 994/// 995class DominanceFrontier : public DominanceFrontierBase { 996public: 997 static char ID; // Pass ID, replacement for typeid 998 DominanceFrontier() : 999 DominanceFrontierBase(&ID, false) {} 1000 1001 BasicBlock *getRoot() const { 1002 assert(Roots.size() == 1 && "Should always have entry node!"); 1003 return Roots[0]; 1004 } 1005 1006 virtual bool runOnFunction(Function &) { 1007 Frontiers.clear(); 1008 DominatorTree &DT = getAnalysis<DominatorTree>(); 1009 Roots = DT.getRoots(); 1010 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 1011 calculate(DT, DT[Roots[0]]); 1012 return false; 1013 } 1014 1015 virtual void verifyAnalysis() const; 1016 1017 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 1018 AU.setPreservesAll(); 1019 AU.addRequired<DominatorTree>(); 1020 } 1021 1022 /// splitBlock - BB is split and now it has one successor. Update dominance 1023 /// frontier to reflect this change. 1024 void splitBlock(BasicBlock *BB); 1025 1026 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier 1027 /// to reflect this change. 1028 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB, 1029 DominatorTree *DT) { 1030 // NewBB is now dominating BB. Which means BB's dominance 1031 // frontier is now part of NewBB's dominance frontier. However, BB 1032 // itself is not member of NewBB's dominance frontier. 1033 DominanceFrontier::iterator NewDFI = find(NewBB); 1034 DominanceFrontier::iterator DFI = find(BB); 1035 // If BB was an entry block then its frontier is empty. 1036 if (DFI == end()) 1037 return; 1038 DominanceFrontier::DomSetType BBSet = DFI->second; 1039 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(), 1040 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) { 1041 BasicBlock *DFMember = *BBSetI; 1042 // Insert only if NewBB dominates DFMember. 1043 if (!DT->dominates(NewBB, DFMember)) 1044 NewDFI->second.insert(DFMember); 1045 } 1046 NewDFI->second.erase(BB); 1047 } 1048 1049 const DomSetType &calculate(const DominatorTree &DT, 1050 const DomTreeNode *Node); 1051}; 1052 1053 1054} // End llvm namespace 1055 1056#endif 1057