Dominators.h revision 45934330150aecbc98c2d60fe7f17fa69e62ba71
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), 244 GraphT::child_end(NewBB)) == 1 && 245 "NewBB should have a single successor!"); 246 typename GraphT::NodeType* NewBBSucc = *GraphT::child_begin(NewBB); 247 248 std::vector<typename GraphT::NodeType*> PredBlocks; 249 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI = 250 GraphTraits<Inverse<N> >::child_begin(NewBB), 251 PE = GraphTraits<Inverse<N> >::child_end(NewBB); PI != PE; ++PI) 252 PredBlocks.push_back(*PI); 253 254 assert(!PredBlocks.empty() && "No predblocks??"); 255 256 bool NewBBDominatesNewBBSucc = true; 257 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI = 258 GraphTraits<Inverse<N> >::child_begin(NewBBSucc), 259 E = GraphTraits<Inverse<N> >::child_end(NewBBSucc); PI != E; ++PI) 260 if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI) && 261 DT.isReachableFromEntry(*PI)) { 262 NewBBDominatesNewBBSucc = false; 263 break; 264 } 265 266 // Find NewBB's immediate dominator and create new dominator tree node for 267 // NewBB. 268 NodeT *NewBBIDom = 0; 269 unsigned i = 0; 270 for (i = 0; i < PredBlocks.size(); ++i) 271 if (DT.isReachableFromEntry(PredBlocks[i])) { 272 NewBBIDom = PredBlocks[i]; 273 break; 274 } 275 276 // It's possible that none of the predecessors of NewBB are reachable; 277 // in that case, NewBB itself is unreachable, so nothing needs to be 278 // changed. 279 if (!NewBBIDom) 280 return; 281 282 for (i = i + 1; i < PredBlocks.size(); ++i) { 283 if (DT.isReachableFromEntry(PredBlocks[i])) 284 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]); 285 } 286 287 // Create the new dominator tree node... and set the idom of NewBB. 288 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom); 289 290 // If NewBB strictly dominates other blocks, then it is now the immediate 291 // dominator of NewBBSucc. Update the dominator tree as appropriate. 292 if (NewBBDominatesNewBBSucc) { 293 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc); 294 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode); 295 } 296 } 297 298public: 299 explicit DominatorTreeBase(bool isPostDom) 300 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {} 301 virtual ~DominatorTreeBase() { reset(); } 302 303 // FIXME: Should remove this 304 virtual bool runOnFunction(Function &F) { return false; } 305 306 /// compare - Return false if the other dominator tree base matches this 307 /// dominator tree base. Otherwise return true. 308 bool compare(DominatorTreeBase &Other) const { 309 310 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes; 311 if (DomTreeNodes.size() != OtherDomTreeNodes.size()) 312 return true; 313 314 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 // Compare the result of the tree walk and the dfs numbers, if expensive 395 // checks are enabled. 396#ifdef XDEBUG 397 assert((!DFSInfoValid || 398 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) && 399 "Tree walk disagrees with dfs numbers!"); 400#endif 401 402 if (DFSInfoValid) 403 return B->DominatedBy(A); 404 405 // If we end up with too many slow queries, just update the 406 // DFS numbers on the theory that we are going to keep querying. 407 SlowQueries++; 408 if (SlowQueries > 32) { 409 updateDFSNumbers(); 410 return B->DominatedBy(A); 411 } 412 413 return dominatedBySlowTreeWalk(A, B); 414 } 415 416 inline bool dominates(const NodeT *A, const NodeT *B) { 417 if (A == B) 418 return true; 419 420 // Cast away the const qualifiers here. This is ok since 421 // this function doesn't actually return the values returned 422 // from getNode. 423 return dominates(getNode(const_cast<NodeT *>(A)), 424 getNode(const_cast<NodeT *>(B))); 425 } 426 427 NodeT *getRoot() const { 428 assert(this->Roots.size() == 1 && "Should always have entry node!"); 429 return this->Roots[0]; 430 } 431 432 /// findNearestCommonDominator - Find nearest common dominator basic block 433 /// for basic block A and B. If there is no such block then return NULL. 434 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) { 435 assert(A->getParent() == B->getParent() && 436 "Two blocks are not in same function"); 437 438 // If either A or B is a entry block then it is nearest common dominator 439 // (for forward-dominators). 440 if (!this->isPostDominator()) { 441 NodeT &Entry = A->getParent()->front(); 442 if (A == &Entry || B == &Entry) 443 return &Entry; 444 } 445 446 // If B dominates A then B is nearest common dominator. 447 if (dominates(B, A)) 448 return B; 449 450 // If A dominates B then A is nearest common dominator. 451 if (dominates(A, B)) 452 return A; 453 454 DomTreeNodeBase<NodeT> *NodeA = getNode(A); 455 DomTreeNodeBase<NodeT> *NodeB = getNode(B); 456 457 // Collect NodeA dominators set. 458 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms; 459 NodeADoms.insert(NodeA); 460 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom(); 461 while (IDomA) { 462 NodeADoms.insert(IDomA); 463 IDomA = IDomA->getIDom(); 464 } 465 466 // Walk NodeB immediate dominators chain and find common dominator node. 467 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom(); 468 while (IDomB) { 469 if (NodeADoms.count(IDomB) != 0) 470 return IDomB->getBlock(); 471 472 IDomB = IDomB->getIDom(); 473 } 474 475 return NULL; 476 } 477 478 //===--------------------------------------------------------------------===// 479 // API to update (Post)DominatorTree information based on modifications to 480 // the CFG... 481 482 /// addNewBlock - Add a new node to the dominator tree information. This 483 /// creates a new node as a child of DomBB dominator node,linking it into 484 /// the children list of the immediate dominator. 485 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) { 486 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 487 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB); 488 assert(IDomNode && "Not immediate dominator specified for block!"); 489 DFSInfoValid = false; 490 return DomTreeNodes[BB] = 491 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode)); 492 } 493 494 /// changeImmediateDominator - This method is used to update the dominator 495 /// tree information when a node's immediate dominator changes. 496 /// 497 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N, 498 DomTreeNodeBase<NodeT> *NewIDom) { 499 assert(N && NewIDom && "Cannot change null node pointers!"); 500 DFSInfoValid = false; 501 N->setIDom(NewIDom); 502 } 503 504 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) { 505 changeImmediateDominator(getNode(BB), getNode(NewBB)); 506 } 507 508 /// eraseNode - Removes a node from the dominator tree. Block must not 509 /// domiante any other blocks. Removes node from its immediate dominator's 510 /// children list. Deletes dominator node associated with basic block BB. 511 void eraseNode(NodeT *BB) { 512 DomTreeNodeBase<NodeT> *Node = getNode(BB); 513 assert(Node && "Removing node that isn't in dominator tree."); 514 assert(Node->getChildren().empty() && "Node is not a leaf node."); 515 516 // Remove node from immediate dominator's children list. 517 DomTreeNodeBase<NodeT> *IDom = Node->getIDom(); 518 if (IDom) { 519 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I = 520 std::find(IDom->Children.begin(), IDom->Children.end(), Node); 521 assert(I != IDom->Children.end() && 522 "Not in immediate dominator children set!"); 523 // I am no longer your child... 524 IDom->Children.erase(I); 525 } 526 527 DomTreeNodes.erase(BB); 528 delete Node; 529 } 530 531 /// removeNode - Removes a node from the dominator tree. Block must not 532 /// dominate any other blocks. Invalidates any node pointing to removed 533 /// block. 534 void removeNode(NodeT *BB) { 535 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 536 DomTreeNodes.erase(BB); 537 } 538 539 /// splitBlock - BB is split and now it has one successor. Update dominator 540 /// tree to reflect this change. 541 void splitBlock(NodeT* NewBB) { 542 if (this->IsPostDominators) 543 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB); 544 else 545 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB); 546 } 547 548 /// print - Convert to human readable form 549 /// 550 void print(raw_ostream &o) const { 551 o << "=============================--------------------------------\n"; 552 if (this->isPostDominator()) 553 o << "Inorder PostDominator Tree: "; 554 else 555 o << "Inorder Dominator Tree: "; 556 if (this->DFSInfoValid) 557 o << "DFSNumbers invalid: " << SlowQueries << " slow queries."; 558 o << "\n"; 559 560 // The postdom tree can have a null root if there are no returns. 561 if (getRootNode()) 562 PrintDomTree<NodeT>(getRootNode(), o, 1); 563 } 564 565protected: 566 template<class GraphT> 567 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT, 568 typename GraphT::NodeType* VIn); 569 570 template<class GraphT> 571 friend typename GraphT::NodeType* Eval( 572 DominatorTreeBase<typename GraphT::NodeType>& DT, 573 typename GraphT::NodeType* V); 574 575 template<class GraphT> 576 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT, 577 unsigned DFSNumV, typename GraphT::NodeType* W, 578 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo); 579 580 template<class GraphT> 581 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT, 582 typename GraphT::NodeType* V, 583 unsigned N); 584 585 template<class FuncT, class N> 586 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT, 587 FuncT& F); 588 589 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking 590 /// dominator tree in dfs order. 591 void updateDFSNumbers() { 592 unsigned DFSNum = 0; 593 594 SmallVector<std::pair<DomTreeNodeBase<NodeT>*, 595 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack; 596 597 DomTreeNodeBase<NodeT> *ThisRoot = getRootNode(); 598 599 if (!ThisRoot) 600 return; 601 602 // Even in the case of multiple exits that form the post dominator root 603 // nodes, do not iterate over all exits, but start from the virtual root 604 // node. Otherwise bbs, that are not post dominated by any exit but by the 605 // virtual root node, will never be assigned a DFS number. 606 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin())); 607 ThisRoot->DFSNumIn = DFSNum++; 608 609 while (!WorkStack.empty()) { 610 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first; 611 typename DomTreeNodeBase<NodeT>::iterator ChildIt = 612 WorkStack.back().second; 613 614 // If we visited all of the children of this node, "recurse" back up the 615 // stack setting the DFOutNum. 616 if (ChildIt == Node->end()) { 617 Node->DFSNumOut = DFSNum++; 618 WorkStack.pop_back(); 619 } else { 620 // Otherwise, recursively visit this child. 621 DomTreeNodeBase<NodeT> *Child = *ChildIt; 622 ++WorkStack.back().second; 623 624 WorkStack.push_back(std::make_pair(Child, Child->begin())); 625 Child->DFSNumIn = DFSNum++; 626 } 627 } 628 629 SlowQueries = 0; 630 DFSInfoValid = true; 631 } 632 633 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) { 634 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB); 635 if (I != this->DomTreeNodes.end() && I->second) 636 return I->second; 637 638 // Haven't calculated this node yet? Get or calculate the node for the 639 // immediate dominator. 640 NodeT *IDom = getIDom(BB); 641 642 assert(IDom || this->DomTreeNodes[NULL]); 643 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom); 644 645 // Add a new tree node for this BasicBlock, and link it as a child of 646 // IDomNode 647 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode); 648 return this->DomTreeNodes[BB] = IDomNode->addChild(C); 649 } 650 651 inline NodeT *getIDom(NodeT *BB) const { 652 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB); 653 return I != IDoms.end() ? I->second : 0; 654 } 655 656 inline void addRoot(NodeT* BB) { 657 this->Roots.push_back(BB); 658 } 659 660public: 661 /// recalculate - compute a dominator tree for the given function 662 template<class FT> 663 void recalculate(FT& F) { 664 reset(); 665 this->Vertex.push_back(0); 666 667 if (!this->IsPostDominators) { 668 // Initialize root 669 this->Roots.push_back(&F.front()); 670 this->IDoms[&F.front()] = 0; 671 this->DomTreeNodes[&F.front()] = 0; 672 673 Calculate<FT, NodeT*>(*this, F); 674 } else { 675 // Initialize the roots list 676 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) { 677 if (std::distance(GraphTraits<FT*>::child_begin(I), 678 GraphTraits<FT*>::child_end(I)) == 0) 679 addRoot(I); 680 681 // Prepopulate maps so that we don't get iterator invalidation issues later. 682 this->IDoms[I] = 0; 683 this->DomTreeNodes[I] = 0; 684 } 685 686 Calculate<FT, Inverse<NodeT*> >(*this, F); 687 } 688 } 689}; 690 691EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>); 692 693//===------------------------------------- 694/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 695/// compute a normal dominator tree. 696/// 697class DominatorTree : public FunctionPass { 698public: 699 static char ID; // Pass ID, replacement for typeid 700 DominatorTreeBase<BasicBlock>* DT; 701 702 DominatorTree() : FunctionPass(&ID) { 703 DT = new DominatorTreeBase<BasicBlock>(false); 704 } 705 706 ~DominatorTree() { 707 delete DT; 708 } 709 710 DominatorTreeBase<BasicBlock>& getBase() { return *DT; } 711 712 /// getRoots - Return the root blocks of the current CFG. This may include 713 /// multiple blocks if we are computing post dominators. For forward 714 /// dominators, this will always be a single block (the entry node). 715 /// 716 inline const std::vector<BasicBlock*> &getRoots() const { 717 return DT->getRoots(); 718 } 719 720 inline BasicBlock *getRoot() const { 721 return DT->getRoot(); 722 } 723 724 inline DomTreeNode *getRootNode() const { 725 return DT->getRootNode(); 726 } 727 728 /// compare - Return false if the other dominator tree matches this 729 /// dominator tree. Otherwise return true. 730 inline bool compare(DominatorTree &Other) const { 731 DomTreeNode *R = getRootNode(); 732 DomTreeNode *OtherR = Other.getRootNode(); 733 734 if (!R || !OtherR || R->getBlock() != OtherR->getBlock()) 735 return true; 736 737 if (DT->compare(Other.getBase())) 738 return true; 739 740 return false; 741 } 742 743 virtual bool runOnFunction(Function &F); 744 745 virtual void verifyAnalysis() const; 746 747 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 748 AU.setPreservesAll(); 749 } 750 751 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const { 752 return DT->dominates(A, B); 753 } 754 755 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const { 756 return DT->dominates(A, B); 757 } 758 759 // dominates - Return true if A dominates B. This performs the 760 // special checks necessary if A and B are in the same basic block. 761 bool dominates(const Instruction *A, const Instruction *B) const; 762 763 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const { 764 return DT->properlyDominates(A, B); 765 } 766 767 bool properlyDominates(BasicBlock *A, BasicBlock *B) const { 768 return DT->properlyDominates(A, B); 769 } 770 771 /// findNearestCommonDominator - Find nearest common dominator basic block 772 /// for basic block A and B. If there is no such block then return NULL. 773 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) { 774 return DT->findNearestCommonDominator(A, B); 775 } 776 777 inline DomTreeNode *operator[](BasicBlock *BB) const { 778 return DT->getNode(BB); 779 } 780 781 /// getNode - return the (Post)DominatorTree node for the specified basic 782 /// block. This is the same as using operator[] on this class. 783 /// 784 inline DomTreeNode *getNode(BasicBlock *BB) const { 785 return DT->getNode(BB); 786 } 787 788 /// addNewBlock - Add a new node to the dominator tree information. This 789 /// creates a new node as a child of DomBB dominator node,linking it into 790 /// the children list of the immediate dominator. 791 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 792 return DT->addNewBlock(BB, DomBB); 793 } 794 795 /// changeImmediateDominator - This method is used to update the dominator 796 /// tree information when a node's immediate dominator changes. 797 /// 798 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) { 799 DT->changeImmediateDominator(N, NewIDom); 800 } 801 802 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) { 803 DT->changeImmediateDominator(N, NewIDom); 804 } 805 806 /// eraseNode - Removes a node from the dominator tree. Block must not 807 /// domiante any other blocks. Removes node from its immediate dominator's 808 /// children list. Deletes dominator node associated with basic block BB. 809 inline void eraseNode(BasicBlock *BB) { 810 DT->eraseNode(BB); 811 } 812 813 /// splitBlock - BB is split and now it has one successor. Update dominator 814 /// tree to reflect this change. 815 inline void splitBlock(BasicBlock* NewBB) { 816 DT->splitBlock(NewBB); 817 } 818 819 bool isReachableFromEntry(BasicBlock* A) { 820 return DT->isReachableFromEntry(A); 821 } 822 823 824 virtual void releaseMemory() { 825 DT->releaseMemory(); 826 } 827 828 virtual void print(raw_ostream &OS, const Module* M= 0) const; 829}; 830 831//===------------------------------------- 832/// DominatorTree GraphTraits specialization so the DominatorTree can be 833/// iterable by generic graph iterators. 834/// 835template <> struct GraphTraits<DomTreeNode*> { 836 typedef DomTreeNode NodeType; 837 typedef NodeType::iterator ChildIteratorType; 838 839 static NodeType *getEntryNode(NodeType *N) { 840 return N; 841 } 842 static inline ChildIteratorType child_begin(NodeType *N) { 843 return N->begin(); 844 } 845 static inline ChildIteratorType child_end(NodeType *N) { 846 return N->end(); 847 } 848 849 typedef df_iterator<DomTreeNode*> nodes_iterator; 850 851 static nodes_iterator nodes_begin(DomTreeNode *N) { 852 return df_begin(getEntryNode(N)); 853 } 854 855 static nodes_iterator nodes_end(DomTreeNode *N) { 856 return df_end(getEntryNode(N)); 857 } 858}; 859 860template <> struct GraphTraits<DominatorTree*> 861 : public GraphTraits<DomTreeNode*> { 862 static NodeType *getEntryNode(DominatorTree *DT) { 863 return DT->getRootNode(); 864 } 865 866 static nodes_iterator nodes_begin(DominatorTree *N) { 867 return df_begin(getEntryNode(N)); 868 } 869 870 static nodes_iterator nodes_end(DominatorTree *N) { 871 return df_end(getEntryNode(N)); 872 } 873}; 874 875 876//===----------------------------------------------------------------------===// 877/// DominanceFrontierBase - Common base class for computing forward and inverse 878/// dominance frontiers for a function. 879/// 880class DominanceFrontierBase : public FunctionPass { 881public: 882 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 883 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 884protected: 885 DomSetMapType Frontiers; 886 std::vector<BasicBlock*> Roots; 887 const bool IsPostDominators; 888 889public: 890 DominanceFrontierBase(void *ID, bool isPostDom) 891 : FunctionPass(ID), IsPostDominators(isPostDom) {} 892 893 /// getRoots - Return the root blocks of the current CFG. This may include 894 /// multiple blocks if we are computing post dominators. For forward 895 /// dominators, this will always be a single block (the entry node). 896 /// 897 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 898 899 /// isPostDominator - Returns true if analysis based of postdoms 900 /// 901 bool isPostDominator() const { return IsPostDominators; } 902 903 virtual void releaseMemory() { Frontiers.clear(); } 904 905 // Accessor interface: 906 typedef DomSetMapType::iterator iterator; 907 typedef DomSetMapType::const_iterator const_iterator; 908 iterator begin() { return Frontiers.begin(); } 909 const_iterator begin() const { return Frontiers.begin(); } 910 iterator end() { return Frontiers.end(); } 911 const_iterator end() const { return Frontiers.end(); } 912 iterator find(BasicBlock *B) { return Frontiers.find(B); } 913 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 914 915 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 916 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 917 return Frontiers.insert(std::make_pair(BB, frontier)).first; 918 } 919 920 /// removeBlock - Remove basic block BB's frontier. 921 void removeBlock(BasicBlock *BB) { 922 assert(find(BB) != end() && "Block is not in DominanceFrontier!"); 923 for (iterator I = begin(), E = end(); I != E; ++I) 924 I->second.erase(BB); 925 Frontiers.erase(BB); 926 } 927 928 void addToFrontier(iterator I, BasicBlock *Node) { 929 assert(I != end() && "BB is not in DominanceFrontier!"); 930 I->second.insert(Node); 931 } 932 933 void removeFromFrontier(iterator I, BasicBlock *Node) { 934 assert(I != end() && "BB is not in DominanceFrontier!"); 935 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 936 I->second.erase(Node); 937 } 938 939 /// compareDomSet - Return false if two domsets match. Otherwise 940 /// return true; 941 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const { 942 std::set<BasicBlock *> tmpSet; 943 for (DomSetType::const_iterator I = DS2.begin(), 944 E = DS2.end(); I != E; ++I) 945 tmpSet.insert(*I); 946 947 for (DomSetType::const_iterator I = DS1.begin(), 948 E = DS1.end(); I != E; ) { 949 BasicBlock *Node = *I++; 950 951 if (tmpSet.erase(Node) == 0) 952 // Node is in DS1 but not in DS2. 953 return true; 954 } 955 956 if (!tmpSet.empty()) 957 // There are nodes that are in DS2 but not in DS1. 958 return true; 959 960 // DS1 and DS2 matches. 961 return false; 962 } 963 964 /// compare - Return true if the other dominance frontier base matches 965 /// this dominance frontier base. Otherwise return false. 966 bool compare(DominanceFrontierBase &Other) const { 967 DomSetMapType tmpFrontiers; 968 for (DomSetMapType::const_iterator I = Other.begin(), 969 E = Other.end(); I != E; ++I) 970 tmpFrontiers.insert(std::make_pair(I->first, I->second)); 971 972 for (DomSetMapType::iterator I = tmpFrontiers.begin(), 973 E = tmpFrontiers.end(); I != E; ) { 974 BasicBlock *Node = I->first; 975 const_iterator DFI = find(Node); 976 if (DFI == end()) 977 return true; 978 979 if (compareDomSet(I->second, DFI->second)) 980 return true; 981 982 ++I; 983 tmpFrontiers.erase(Node); 984 } 985 986 if (!tmpFrontiers.empty()) 987 return true; 988 989 return false; 990 } 991 992 /// print - Convert to human readable form 993 /// 994 virtual void print(raw_ostream &OS, const Module* = 0) const; 995}; 996 997 998//===------------------------------------- 999/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 1000/// used to compute a forward dominator frontiers. 1001/// 1002class DominanceFrontier : public DominanceFrontierBase { 1003public: 1004 static char ID; // Pass ID, replacement for typeid 1005 DominanceFrontier() : 1006 DominanceFrontierBase(&ID, false) {} 1007 1008 BasicBlock *getRoot() const { 1009 assert(Roots.size() == 1 && "Should always have entry node!"); 1010 return Roots[0]; 1011 } 1012 1013 virtual bool runOnFunction(Function &) { 1014 Frontiers.clear(); 1015 DominatorTree &DT = getAnalysis<DominatorTree>(); 1016 Roots = DT.getRoots(); 1017 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 1018 calculate(DT, DT[Roots[0]]); 1019 return false; 1020 } 1021 1022 virtual void verifyAnalysis() const; 1023 1024 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 1025 AU.setPreservesAll(); 1026 AU.addRequired<DominatorTree>(); 1027 } 1028 1029 /// splitBlock - BB is split and now it has one successor. Update dominance 1030 /// frontier to reflect this change. 1031 void splitBlock(BasicBlock *BB); 1032 1033 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier 1034 /// to reflect this change. 1035 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB, 1036 DominatorTree *DT) { 1037 // NewBB is now dominating BB. Which means BB's dominance 1038 // frontier is now part of NewBB's dominance frontier. However, BB 1039 // itself is not member of NewBB's dominance frontier. 1040 DominanceFrontier::iterator NewDFI = find(NewBB); 1041 DominanceFrontier::iterator DFI = find(BB); 1042 // If BB was an entry block then its frontier is empty. 1043 if (DFI == end()) 1044 return; 1045 DominanceFrontier::DomSetType BBSet = DFI->second; 1046 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(), 1047 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) { 1048 BasicBlock *DFMember = *BBSetI; 1049 // Insert only if NewBB dominates DFMember. 1050 if (!DT->dominates(NewBB, DFMember)) 1051 NewDFI->second.insert(DFMember); 1052 } 1053 NewDFI->second.erase(BB); 1054 } 1055 1056 const DomSetType &calculate(const DominatorTree &DT, 1057 const DomTreeNode *Node); 1058}; 1059 1060 1061} // End llvm namespace 1062 1063#endif 1064