Dominators.h revision 14e8190f4329bc0ea4d8813da7486d3e05affc7c
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 typedef GraphTraits<Inverse<N> > InvTraits; 250 for (typename InvTraits::ChildIteratorType PI = 251 InvTraits::child_begin(NewBB), 252 PE = InvTraits::child_end(NewBB); PI != PE; ++PI) 253 PredBlocks.push_back(*PI); 254 255 assert(!PredBlocks.empty() && "No predblocks?"); 256 257 bool NewBBDominatesNewBBSucc = true; 258 for (typename InvTraits::ChildIteratorType PI = 259 InvTraits::child_begin(NewBBSucc), 260 E = InvTraits::child_end(NewBBSucc); PI != E; ++PI) { 261 typename InvTraits::NodeType *ND = *PI; 262 if (ND != NewBB && !DT.dominates(NewBBSucc, ND) && 263 DT.isReachableFromEntry(ND)) { 264 NewBBDominatesNewBBSucc = false; 265 break; 266 } 267 } 268 269 // Find NewBB's immediate dominator and create new dominator tree node for 270 // NewBB. 271 NodeT *NewBBIDom = 0; 272 unsigned i = 0; 273 for (i = 0; i < PredBlocks.size(); ++i) 274 if (DT.isReachableFromEntry(PredBlocks[i])) { 275 NewBBIDom = PredBlocks[i]; 276 break; 277 } 278 279 // It's possible that none of the predecessors of NewBB are reachable; 280 // in that case, NewBB itself is unreachable, so nothing needs to be 281 // changed. 282 if (!NewBBIDom) 283 return; 284 285 for (i = i + 1; i < PredBlocks.size(); ++i) { 286 if (DT.isReachableFromEntry(PredBlocks[i])) 287 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]); 288 } 289 290 // Create the new dominator tree node... and set the idom of NewBB. 291 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom); 292 293 // If NewBB strictly dominates other blocks, then it is now the immediate 294 // dominator of NewBBSucc. Update the dominator tree as appropriate. 295 if (NewBBDominatesNewBBSucc) { 296 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc); 297 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode); 298 } 299 } 300 301public: 302 explicit DominatorTreeBase(bool isPostDom) 303 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {} 304 virtual ~DominatorTreeBase() { reset(); } 305 306 // FIXME: Should remove this 307 virtual bool runOnFunction(Function &F) { return false; } 308 309 /// compare - Return false if the other dominator tree base matches this 310 /// dominator tree base. Otherwise return true. 311 bool compare(DominatorTreeBase &Other) const { 312 313 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes; 314 if (DomTreeNodes.size() != OtherDomTreeNodes.size()) 315 return true; 316 317 for (typename DomTreeNodeMapType::const_iterator 318 I = this->DomTreeNodes.begin(), 319 E = this->DomTreeNodes.end(); I != E; ++I) { 320 NodeT *BB = I->first; 321 typename DomTreeNodeMapType::const_iterator OI = OtherDomTreeNodes.find(BB); 322 if (OI == OtherDomTreeNodes.end()) 323 return true; 324 325 DomTreeNodeBase<NodeT>* MyNd = I->second; 326 DomTreeNodeBase<NodeT>* OtherNd = OI->second; 327 328 if (MyNd->compare(OtherNd)) 329 return true; 330 } 331 332 return false; 333 } 334 335 virtual void releaseMemory() { reset(); } 336 337 /// getNode - return the (Post)DominatorTree node for the specified basic 338 /// block. This is the same as using operator[] on this class. 339 /// 340 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const { 341 typename DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB); 342 return I != DomTreeNodes.end() ? I->second : 0; 343 } 344 345 /// getRootNode - This returns the entry node for the CFG of the function. If 346 /// this tree represents the post-dominance relations for a function, however, 347 /// this root may be a node with the block == NULL. This is the case when 348 /// there are multiple exit nodes from a particular function. Consumers of 349 /// post-dominance information must be capable of dealing with this 350 /// possibility. 351 /// 352 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; } 353 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; } 354 355 /// properlyDominates - Returns true iff this dominates N and this != N. 356 /// Note that this is not a constant time operation! 357 /// 358 bool properlyDominates(const DomTreeNodeBase<NodeT> *A, 359 const DomTreeNodeBase<NodeT> *B) const { 360 if (A == 0 || B == 0) return false; 361 return dominatedBySlowTreeWalk(A, B); 362 } 363 364 inline bool properlyDominates(const NodeT *A, const NodeT *B) { 365 if (A == B) 366 return false; 367 368 // Cast away the const qualifiers here. This is ok since 369 // this function doesn't actually return the values returned 370 // from getNode. 371 return properlyDominates(getNode(const_cast<NodeT *>(A)), 372 getNode(const_cast<NodeT *>(B))); 373 } 374 375 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A, 376 const DomTreeNodeBase<NodeT> *B) const { 377 const DomTreeNodeBase<NodeT> *IDom; 378 if (A == 0 || B == 0) return false; 379 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B) 380 B = IDom; // Walk up the tree 381 return IDom != 0; 382 } 383 384 385 /// isReachableFromEntry - Return true if A is dominated by the entry 386 /// block of the function containing it. 387 bool isReachableFromEntry(const NodeT* A) { 388 assert(!this->isPostDominator() && 389 "This is not implemented for post dominators"); 390 return dominates(&A->getParent()->front(), A); 391 } 392 393 /// dominates - Returns true iff A dominates B. Note that this is not a 394 /// constant time operation! 395 /// 396 inline bool dominates(const DomTreeNodeBase<NodeT> *A, 397 const DomTreeNodeBase<NodeT> *B) { 398 if (B == A) 399 return true; // A node trivially dominates itself. 400 401 if (A == 0 || B == 0) 402 return false; 403 404 // Compare the result of the tree walk and the dfs numbers, if expensive 405 // checks are enabled. 406#ifdef XDEBUG 407 assert((!DFSInfoValid || 408 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) && 409 "Tree walk disagrees with dfs numbers!"); 410#endif 411 412 if (DFSInfoValid) 413 return B->DominatedBy(A); 414 415 // If we end up with too many slow queries, just update the 416 // DFS numbers on the theory that we are going to keep querying. 417 SlowQueries++; 418 if (SlowQueries > 32) { 419 updateDFSNumbers(); 420 return B->DominatedBy(A); 421 } 422 423 return dominatedBySlowTreeWalk(A, B); 424 } 425 426 inline bool dominates(const NodeT *A, const NodeT *B) { 427 if (A == B) 428 return true; 429 430 // Cast away the const qualifiers here. This is ok since 431 // this function doesn't actually return the values returned 432 // from getNode. 433 return dominates(getNode(const_cast<NodeT *>(A)), 434 getNode(const_cast<NodeT *>(B))); 435 } 436 437 NodeT *getRoot() const { 438 assert(this->Roots.size() == 1 && "Should always have entry node!"); 439 return this->Roots[0]; 440 } 441 442 /// findNearestCommonDominator - Find nearest common dominator basic block 443 /// for basic block A and B. If there is no such block then return NULL. 444 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) { 445 assert(A->getParent() == B->getParent() && 446 "Two blocks are not in same function"); 447 448 // If either A or B is a entry block then it is nearest common dominator 449 // (for forward-dominators). 450 if (!this->isPostDominator()) { 451 NodeT &Entry = A->getParent()->front(); 452 if (A == &Entry || B == &Entry) 453 return &Entry; 454 } 455 456 // If B dominates A then B is nearest common dominator. 457 if (dominates(B, A)) 458 return B; 459 460 // If A dominates B then A is nearest common dominator. 461 if (dominates(A, B)) 462 return A; 463 464 DomTreeNodeBase<NodeT> *NodeA = getNode(A); 465 DomTreeNodeBase<NodeT> *NodeB = getNode(B); 466 467 // Collect NodeA dominators set. 468 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms; 469 NodeADoms.insert(NodeA); 470 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom(); 471 while (IDomA) { 472 NodeADoms.insert(IDomA); 473 IDomA = IDomA->getIDom(); 474 } 475 476 // Walk NodeB immediate dominators chain and find common dominator node. 477 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom(); 478 while (IDomB) { 479 if (NodeADoms.count(IDomB) != 0) 480 return IDomB->getBlock(); 481 482 IDomB = IDomB->getIDom(); 483 } 484 485 return NULL; 486 } 487 488 const NodeT *findNearestCommonDominator(const NodeT *A, const NodeT *B) { 489 // Cast away the const qualifiers here. This is ok since 490 // const is re-introduced on the return type. 491 return findNearestCommonDominator(const_cast<NodeT *>(A), 492 const_cast<NodeT *>(B)); 493 } 494 495 //===--------------------------------------------------------------------===// 496 // API to update (Post)DominatorTree information based on modifications to 497 // the CFG... 498 499 /// addNewBlock - Add a new node to the dominator tree information. This 500 /// creates a new node as a child of DomBB dominator node,linking it into 501 /// the children list of the immediate dominator. 502 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) { 503 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 504 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB); 505 assert(IDomNode && "Not immediate dominator specified for block!"); 506 DFSInfoValid = false; 507 return DomTreeNodes[BB] = 508 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode)); 509 } 510 511 /// changeImmediateDominator - This method is used to update the dominator 512 /// tree information when a node's immediate dominator changes. 513 /// 514 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N, 515 DomTreeNodeBase<NodeT> *NewIDom) { 516 assert(N && NewIDom && "Cannot change null node pointers!"); 517 DFSInfoValid = false; 518 N->setIDom(NewIDom); 519 } 520 521 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) { 522 changeImmediateDominator(getNode(BB), getNode(NewBB)); 523 } 524 525 /// eraseNode - Removes a node from the dominator tree. Block must not 526 /// dominate any other blocks. Removes node from its immediate dominator's 527 /// children list. Deletes dominator node associated with basic block BB. 528 void eraseNode(NodeT *BB) { 529 DomTreeNodeBase<NodeT> *Node = getNode(BB); 530 assert(Node && "Removing node that isn't in dominator tree."); 531 assert(Node->getChildren().empty() && "Node is not a leaf node."); 532 533 // Remove node from immediate dominator's children list. 534 DomTreeNodeBase<NodeT> *IDom = Node->getIDom(); 535 if (IDom) { 536 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I = 537 std::find(IDom->Children.begin(), IDom->Children.end(), Node); 538 assert(I != IDom->Children.end() && 539 "Not in immediate dominator children set!"); 540 // I am no longer your child... 541 IDom->Children.erase(I); 542 } 543 544 DomTreeNodes.erase(BB); 545 delete Node; 546 } 547 548 /// removeNode - Removes a node from the dominator tree. Block must not 549 /// dominate any other blocks. Invalidates any node pointing to removed 550 /// block. 551 void removeNode(NodeT *BB) { 552 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 553 DomTreeNodes.erase(BB); 554 } 555 556 /// splitBlock - BB is split and now it has one successor. Update dominator 557 /// tree to reflect this change. 558 void splitBlock(NodeT* NewBB) { 559 if (this->IsPostDominators) 560 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB); 561 else 562 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB); 563 } 564 565 /// print - Convert to human readable form 566 /// 567 void print(raw_ostream &o) const { 568 o << "=============================--------------------------------\n"; 569 if (this->isPostDominator()) 570 o << "Inorder PostDominator Tree: "; 571 else 572 o << "Inorder Dominator Tree: "; 573 if (this->DFSInfoValid) 574 o << "DFSNumbers invalid: " << SlowQueries << " slow queries."; 575 o << "\n"; 576 577 // The postdom tree can have a null root if there are no returns. 578 if (getRootNode()) 579 PrintDomTree<NodeT>(getRootNode(), o, 1); 580 } 581 582protected: 583 template<class GraphT> 584 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT, 585 typename GraphT::NodeType* VIn); 586 587 template<class GraphT> 588 friend typename GraphT::NodeType* Eval( 589 DominatorTreeBase<typename GraphT::NodeType>& DT, 590 typename GraphT::NodeType* V); 591 592 template<class GraphT> 593 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT, 594 unsigned DFSNumV, typename GraphT::NodeType* W, 595 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo); 596 597 template<class GraphT> 598 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT, 599 typename GraphT::NodeType* V, 600 unsigned N); 601 602 template<class FuncT, class N> 603 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT, 604 FuncT& F); 605 606 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking 607 /// dominator tree in dfs order. 608 void updateDFSNumbers() { 609 unsigned DFSNum = 0; 610 611 SmallVector<std::pair<DomTreeNodeBase<NodeT>*, 612 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack; 613 614 DomTreeNodeBase<NodeT> *ThisRoot = getRootNode(); 615 616 if (!ThisRoot) 617 return; 618 619 // Even in the case of multiple exits that form the post dominator root 620 // nodes, do not iterate over all exits, but start from the virtual root 621 // node. Otherwise bbs, that are not post dominated by any exit but by the 622 // virtual root node, will never be assigned a DFS number. 623 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin())); 624 ThisRoot->DFSNumIn = DFSNum++; 625 626 while (!WorkStack.empty()) { 627 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first; 628 typename DomTreeNodeBase<NodeT>::iterator ChildIt = 629 WorkStack.back().second; 630 631 // If we visited all of the children of this node, "recurse" back up the 632 // stack setting the DFOutNum. 633 if (ChildIt == Node->end()) { 634 Node->DFSNumOut = DFSNum++; 635 WorkStack.pop_back(); 636 } else { 637 // Otherwise, recursively visit this child. 638 DomTreeNodeBase<NodeT> *Child = *ChildIt; 639 ++WorkStack.back().second; 640 641 WorkStack.push_back(std::make_pair(Child, Child->begin())); 642 Child->DFSNumIn = DFSNum++; 643 } 644 } 645 646 SlowQueries = 0; 647 DFSInfoValid = true; 648 } 649 650 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) { 651 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB); 652 if (I != this->DomTreeNodes.end() && I->second) 653 return I->second; 654 655 // Haven't calculated this node yet? Get or calculate the node for the 656 // immediate dominator. 657 NodeT *IDom = getIDom(BB); 658 659 assert(IDom || this->DomTreeNodes[NULL]); 660 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom); 661 662 // Add a new tree node for this BasicBlock, and link it as a child of 663 // IDomNode 664 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode); 665 return this->DomTreeNodes[BB] = IDomNode->addChild(C); 666 } 667 668 inline NodeT *getIDom(NodeT *BB) const { 669 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB); 670 return I != IDoms.end() ? I->second : 0; 671 } 672 673 inline void addRoot(NodeT* BB) { 674 this->Roots.push_back(BB); 675 } 676 677public: 678 /// recalculate - compute a dominator tree for the given function 679 template<class FT> 680 void recalculate(FT& F) { 681 reset(); 682 this->Vertex.push_back(0); 683 684 if (!this->IsPostDominators) { 685 // Initialize root 686 this->Roots.push_back(&F.front()); 687 this->IDoms[&F.front()] = 0; 688 this->DomTreeNodes[&F.front()] = 0; 689 690 Calculate<FT, NodeT*>(*this, F); 691 } else { 692 // Initialize the roots list 693 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) { 694 if (std::distance(GraphTraits<FT*>::child_begin(I), 695 GraphTraits<FT*>::child_end(I)) == 0) 696 addRoot(I); 697 698 // Prepopulate maps so that we don't get iterator invalidation issues later. 699 this->IDoms[I] = 0; 700 this->DomTreeNodes[I] = 0; 701 } 702 703 Calculate<FT, Inverse<NodeT*> >(*this, F); 704 } 705 } 706}; 707 708EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>); 709 710//===------------------------------------- 711/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 712/// compute a normal dominator tree. 713/// 714class DominatorTree : public FunctionPass { 715public: 716 static char ID; // Pass ID, replacement for typeid 717 DominatorTreeBase<BasicBlock>* DT; 718 719 DominatorTree() : FunctionPass(ID) { 720 DT = new DominatorTreeBase<BasicBlock>(false); 721 } 722 723 ~DominatorTree() { 724 delete DT; 725 } 726 727 DominatorTreeBase<BasicBlock>& getBase() { return *DT; } 728 729 /// getRoots - Return the root blocks of the current CFG. This may include 730 /// multiple blocks if we are computing post dominators. For forward 731 /// dominators, this will always be a single block (the entry node). 732 /// 733 inline const std::vector<BasicBlock*> &getRoots() const { 734 return DT->getRoots(); 735 } 736 737 inline BasicBlock *getRoot() const { 738 return DT->getRoot(); 739 } 740 741 inline DomTreeNode *getRootNode() const { 742 return DT->getRootNode(); 743 } 744 745 /// compare - Return false if the other dominator tree matches this 746 /// dominator tree. Otherwise return true. 747 inline bool compare(DominatorTree &Other) const { 748 DomTreeNode *R = getRootNode(); 749 DomTreeNode *OtherR = Other.getRootNode(); 750 751 if (!R || !OtherR || R->getBlock() != OtherR->getBlock()) 752 return true; 753 754 if (DT->compare(Other.getBase())) 755 return true; 756 757 return false; 758 } 759 760 virtual bool runOnFunction(Function &F); 761 762 virtual void verifyAnalysis() const; 763 764 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 765 AU.setPreservesAll(); 766 } 767 768 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const { 769 return DT->dominates(A, B); 770 } 771 772 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const { 773 return DT->dominates(A, B); 774 } 775 776 // dominates - Return true if A dominates B. This performs the 777 // special checks necessary if A and B are in the same basic block. 778 bool dominates(const Instruction *A, const Instruction *B) const; 779 780 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const { 781 return DT->properlyDominates(A, B); 782 } 783 784 bool properlyDominates(const BasicBlock *A, const BasicBlock *B) const { 785 return DT->properlyDominates(A, B); 786 } 787 788 /// findNearestCommonDominator - Find nearest common dominator basic block 789 /// for basic block A and B. If there is no such block then return NULL. 790 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) { 791 return DT->findNearestCommonDominator(A, B); 792 } 793 794 inline const BasicBlock *findNearestCommonDominator(const BasicBlock *A, 795 const BasicBlock *B) { 796 return DT->findNearestCommonDominator(A, B); 797 } 798 799 inline DomTreeNode *operator[](BasicBlock *BB) const { 800 return DT->getNode(BB); 801 } 802 803 /// getNode - return the (Post)DominatorTree node for the specified basic 804 /// block. This is the same as using operator[] on this class. 805 /// 806 inline DomTreeNode *getNode(BasicBlock *BB) const { 807 return DT->getNode(BB); 808 } 809 810 /// addNewBlock - Add a new node to the dominator tree information. This 811 /// creates a new node as a child of DomBB dominator node,linking it into 812 /// the children list of the immediate dominator. 813 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 814 return DT->addNewBlock(BB, DomBB); 815 } 816 817 /// changeImmediateDominator - This method is used to update the dominator 818 /// tree information when a node's immediate dominator changes. 819 /// 820 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) { 821 DT->changeImmediateDominator(N, NewIDom); 822 } 823 824 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) { 825 DT->changeImmediateDominator(N, NewIDom); 826 } 827 828 /// eraseNode - Removes a node from the dominator tree. Block must not 829 /// dominate any other blocks. Removes node from its immediate dominator's 830 /// children list. Deletes dominator node associated with basic block BB. 831 inline void eraseNode(BasicBlock *BB) { 832 DT->eraseNode(BB); 833 } 834 835 /// splitBlock - BB is split and now it has one successor. Update dominator 836 /// tree to reflect this change. 837 inline void splitBlock(BasicBlock* NewBB) { 838 DT->splitBlock(NewBB); 839 } 840 841 bool isReachableFromEntry(const BasicBlock* A) { 842 return DT->isReachableFromEntry(A); 843 } 844 845 846 virtual void releaseMemory() { 847 DT->releaseMemory(); 848 } 849 850 virtual void print(raw_ostream &OS, const Module* M= 0) const; 851}; 852 853//===------------------------------------- 854/// DominatorTree GraphTraits specialization so the DominatorTree can be 855/// iterable by generic graph iterators. 856/// 857template <> struct GraphTraits<DomTreeNode*> { 858 typedef DomTreeNode NodeType; 859 typedef NodeType::iterator ChildIteratorType; 860 861 static NodeType *getEntryNode(NodeType *N) { 862 return N; 863 } 864 static inline ChildIteratorType child_begin(NodeType *N) { 865 return N->begin(); 866 } 867 static inline ChildIteratorType child_end(NodeType *N) { 868 return N->end(); 869 } 870 871 typedef df_iterator<DomTreeNode*> nodes_iterator; 872 873 static nodes_iterator nodes_begin(DomTreeNode *N) { 874 return df_begin(getEntryNode(N)); 875 } 876 877 static nodes_iterator nodes_end(DomTreeNode *N) { 878 return df_end(getEntryNode(N)); 879 } 880}; 881 882template <> struct GraphTraits<DominatorTree*> 883 : public GraphTraits<DomTreeNode*> { 884 static NodeType *getEntryNode(DominatorTree *DT) { 885 return DT->getRootNode(); 886 } 887 888 static nodes_iterator nodes_begin(DominatorTree *N) { 889 return df_begin(getEntryNode(N)); 890 } 891 892 static nodes_iterator nodes_end(DominatorTree *N) { 893 return df_end(getEntryNode(N)); 894 } 895}; 896 897 898//===----------------------------------------------------------------------===// 899/// DominanceFrontierBase - Common base class for computing forward and inverse 900/// dominance frontiers for a function. 901/// 902class DominanceFrontierBase : public FunctionPass { 903public: 904 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 905 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 906protected: 907 DomSetMapType Frontiers; 908 std::vector<BasicBlock*> Roots; 909 const bool IsPostDominators; 910 911public: 912 DominanceFrontierBase(char &ID, bool isPostDom) 913 : FunctionPass(ID), IsPostDominators(isPostDom) {} 914 915 /// getRoots - Return the root blocks of the current CFG. This may include 916 /// multiple blocks if we are computing post dominators. For forward 917 /// dominators, this will always be a single block (the entry node). 918 /// 919 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 920 921 /// isPostDominator - Returns true if analysis based of postdoms 922 /// 923 bool isPostDominator() const { return IsPostDominators; } 924 925 virtual void releaseMemory() { Frontiers.clear(); } 926 927 // Accessor interface: 928 typedef DomSetMapType::iterator iterator; 929 typedef DomSetMapType::const_iterator const_iterator; 930 iterator begin() { return Frontiers.begin(); } 931 const_iterator begin() const { return Frontiers.begin(); } 932 iterator end() { return Frontiers.end(); } 933 const_iterator end() const { return Frontiers.end(); } 934 iterator find(BasicBlock *B) { return Frontiers.find(B); } 935 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 936 937 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 938 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 939 return Frontiers.insert(std::make_pair(BB, frontier)).first; 940 } 941 942 /// removeBlock - Remove basic block BB's frontier. 943 void removeBlock(BasicBlock *BB) { 944 assert(find(BB) != end() && "Block is not in DominanceFrontier!"); 945 for (iterator I = begin(), E = end(); I != E; ++I) 946 I->second.erase(BB); 947 Frontiers.erase(BB); 948 } 949 950 void addToFrontier(iterator I, BasicBlock *Node) { 951 assert(I != end() && "BB is not in DominanceFrontier!"); 952 I->second.insert(Node); 953 } 954 955 void removeFromFrontier(iterator I, BasicBlock *Node) { 956 assert(I != end() && "BB is not in DominanceFrontier!"); 957 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 958 I->second.erase(Node); 959 } 960 961 /// compareDomSet - Return false if two domsets match. Otherwise 962 /// return true; 963 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const { 964 std::set<BasicBlock *> tmpSet; 965 for (DomSetType::const_iterator I = DS2.begin(), 966 E = DS2.end(); I != E; ++I) 967 tmpSet.insert(*I); 968 969 for (DomSetType::const_iterator I = DS1.begin(), 970 E = DS1.end(); I != E; ) { 971 BasicBlock *Node = *I++; 972 973 if (tmpSet.erase(Node) == 0) 974 // Node is in DS1 but not in DS2. 975 return true; 976 } 977 978 if (!tmpSet.empty()) 979 // There are nodes that are in DS2 but not in DS1. 980 return true; 981 982 // DS1 and DS2 matches. 983 return false; 984 } 985 986 /// compare - Return true if the other dominance frontier base matches 987 /// this dominance frontier base. Otherwise return false. 988 bool compare(DominanceFrontierBase &Other) const { 989 DomSetMapType tmpFrontiers; 990 for (DomSetMapType::const_iterator I = Other.begin(), 991 E = Other.end(); I != E; ++I) 992 tmpFrontiers.insert(std::make_pair(I->first, I->second)); 993 994 for (DomSetMapType::iterator I = tmpFrontiers.begin(), 995 E = tmpFrontiers.end(); I != E; ) { 996 BasicBlock *Node = I->first; 997 const_iterator DFI = find(Node); 998 if (DFI == end()) 999 return true; 1000 1001 if (compareDomSet(I->second, DFI->second)) 1002 return true; 1003 1004 ++I; 1005 tmpFrontiers.erase(Node); 1006 } 1007 1008 if (!tmpFrontiers.empty()) 1009 return true; 1010 1011 return false; 1012 } 1013 1014 /// print - Convert to human readable form 1015 /// 1016 virtual void print(raw_ostream &OS, const Module* = 0) const; 1017 1018 /// dump - Dump the dominance frontier to dbgs(). 1019 void dump() const; 1020}; 1021 1022 1023//===------------------------------------- 1024/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 1025/// used to compute a forward dominator frontiers. 1026/// 1027class DominanceFrontier : public DominanceFrontierBase { 1028public: 1029 static char ID; // Pass ID, replacement for typeid 1030 DominanceFrontier() : 1031 DominanceFrontierBase(ID, false) {} 1032 1033 BasicBlock *getRoot() const { 1034 assert(Roots.size() == 1 && "Should always have entry node!"); 1035 return Roots[0]; 1036 } 1037 1038 virtual bool runOnFunction(Function &) { 1039 Frontiers.clear(); 1040 DominatorTree &DT = getAnalysis<DominatorTree>(); 1041 Roots = DT.getRoots(); 1042 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 1043 calculate(DT, DT[Roots[0]]); 1044 return false; 1045 } 1046 1047 virtual void verifyAnalysis() const; 1048 1049 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 1050 AU.setPreservesAll(); 1051 AU.addRequired<DominatorTree>(); 1052 } 1053 1054 /// splitBlock - BB is split and now it has one successor. Update dominance 1055 /// frontier to reflect this change. 1056 void splitBlock(BasicBlock *BB); 1057 1058 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier 1059 /// to reflect this change. 1060 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB, 1061 DominatorTree *DT) { 1062 // NewBB is now dominating BB. Which means BB's dominance 1063 // frontier is now part of NewBB's dominance frontier. However, BB 1064 // itself is not member of NewBB's dominance frontier. 1065 DominanceFrontier::iterator NewDFI = find(NewBB); 1066 DominanceFrontier::iterator DFI = find(BB); 1067 // If BB was an entry block then its frontier is empty. 1068 if (DFI == end()) 1069 return; 1070 DominanceFrontier::DomSetType BBSet = DFI->second; 1071 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(), 1072 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) { 1073 BasicBlock *DFMember = *BBSetI; 1074 // Insert only if NewBB dominates DFMember. 1075 if (!DT->dominates(NewBB, DFMember)) 1076 NewDFI->second.insert(DFMember); 1077 } 1078 NewDFI->second.erase(BB); 1079 } 1080 1081 const DomSetType &calculate(const DominatorTree &DT, 1082 const DomTreeNode *Node); 1083}; 1084 1085 1086} // End llvm namespace 1087 1088#endif 1089