Dominators.h revision b62ff3f7f18de9e7c84d14e91132e07199663f42
1//===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the following classes: 11// 1. ImmediateDominators: Calculates and holds a mapping between BasicBlocks 12// and their immediate dominator. 13// 2. DominatorSet: Calculates the [reverse] dominator set for a function 14// 3. DominatorTree: Represent the ImmediateDominator as an explicit tree 15// structure. 16// 4. ETForest: Efficient data structure for dominance comparisons and 17// nearest-common-ancestor queries. 18// 5. DominanceFrontier: Calculate and hold the dominance frontier for a 19// function. 20// 21// These data structures are listed in increasing order of complexity. It 22// takes longer to calculate the dominator frontier, for example, than the 23// ImmediateDominator mapping. 24// 25//===----------------------------------------------------------------------===// 26 27#ifndef LLVM_ANALYSIS_DOMINATORS_H 28#define LLVM_ANALYSIS_DOMINATORS_H 29 30#include "llvm/Analysis/ET-Forest.h" 31#include "llvm/Pass.h" 32#include <set> 33 34namespace llvm { 35 36class Instruction; 37 38template <typename GraphType> struct GraphTraits; 39 40//===----------------------------------------------------------------------===// 41/// DominatorBase - Base class that other, more interesting dominator analyses 42/// inherit from. 43/// 44class DominatorBase : public FunctionPass { 45protected: 46 std::vector<BasicBlock*> Roots; 47 const bool IsPostDominators; 48 49 inline DominatorBase(bool isPostDom) : Roots(), IsPostDominators(isPostDom) {} 50public: 51 /// getRoots - Return the root blocks of the current CFG. This may include 52 /// multiple blocks if we are computing post dominators. For forward 53 /// dominators, this will always be a single block (the entry node). 54 /// 55 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 56 57 /// isPostDominator - Returns true if analysis based of postdoms 58 /// 59 bool isPostDominator() const { return IsPostDominators; } 60}; 61 62 63//===----------------------------------------------------------------------===// 64/// ImmediateDominators - Calculate the immediate dominator for each node in a 65/// function. 66/// 67class ImmediateDominatorsBase : public DominatorBase { 68protected: 69 struct InfoRec { 70 unsigned Semi; 71 unsigned Size; 72 BasicBlock *Label, *Parent, *Child, *Ancestor; 73 74 std::vector<BasicBlock*> Bucket; 75 76 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 77 }; 78 79 std::map<BasicBlock*, BasicBlock*> IDoms; 80 81 // Vertex - Map the DFS number to the BasicBlock* 82 std::vector<BasicBlock*> Vertex; 83 84 // Info - Collection of information used during the computation of idoms. 85 std::map<BasicBlock*, InfoRec> Info; 86public: 87 ImmediateDominatorsBase(bool isPostDom) : DominatorBase(isPostDom) {} 88 89 virtual void releaseMemory() { IDoms.clear(); } 90 91 // Accessor interface: 92 typedef std::map<BasicBlock*, BasicBlock*> IDomMapType; 93 typedef IDomMapType::const_iterator const_iterator; 94 inline const_iterator begin() const { return IDoms.begin(); } 95 inline const_iterator end() const { return IDoms.end(); } 96 inline const_iterator find(BasicBlock* B) const { return IDoms.find(B);} 97 98 /// operator[] - Return the idom for the specified basic block. The start 99 /// node returns null, because it does not have an immediate dominator. 100 /// 101 inline BasicBlock *operator[](BasicBlock *BB) const { 102 return get(BB); 103 } 104 105 /// dominates - Return true if A dominates B. 106 /// 107 bool dominates(BasicBlock *A, BasicBlock *B) const; 108 109 /// properlyDominates - Return true if A dominates B and A != B. 110 /// 111 bool properlyDominates(BasicBlock *A, BasicBlock *B) const { 112 return A != B || properlyDominates(A, B); 113 } 114 115 /// get() - Synonym for operator[]. 116 /// 117 inline BasicBlock *get(BasicBlock *BB) const { 118 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 119 return I != IDoms.end() ? I->second : 0; 120 } 121 122 //===--------------------------------------------------------------------===// 123 // API to update Immediate(Post)Dominators information based on modifications 124 // to the CFG... 125 126 /// addNewBlock - Add a new block to the CFG, with the specified immediate 127 /// dominator. 128 /// 129 void addNewBlock(BasicBlock *BB, BasicBlock *IDom) { 130 assert(get(BB) == 0 && "BasicBlock already in idom info!"); 131 IDoms[BB] = IDom; 132 } 133 134 /// setImmediateDominator - Update the immediate dominator information to 135 /// change the current immediate dominator for the specified block to another 136 /// block. This method requires that BB already have an IDom, otherwise just 137 /// use addNewBlock. 138 /// 139 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom) { 140 assert(IDoms.find(BB) != IDoms.end() && "BB doesn't have idom yet!"); 141 IDoms[BB] = NewIDom; 142 } 143 144 /// print - Convert to human readable form 145 /// 146 virtual void print(std::ostream &OS, const Module* = 0) const; 147}; 148 149//===------------------------------------- 150/// ImmediateDominators Class - Concrete subclass of ImmediateDominatorsBase 151/// that is used to compute a normal immediate dominator set. 152/// 153class ImmediateDominators : public ImmediateDominatorsBase { 154public: 155 ImmediateDominators() : ImmediateDominatorsBase(false) {} 156 157 BasicBlock *getRoot() const { 158 assert(Roots.size() == 1 && "Should always have entry node!"); 159 return Roots[0]; 160 } 161 162 virtual bool runOnFunction(Function &F); 163 164 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 165 AU.setPreservesAll(); 166 } 167 168private: 169 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 170 void Compress(BasicBlock *V, InfoRec &VInfo); 171 BasicBlock *Eval(BasicBlock *v); 172 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 173}; 174 175 176 177//===----------------------------------------------------------------------===// 178/// DominatorSet - Maintain a set<BasicBlock*> for every basic block in a 179/// function, that represents the blocks that dominate the block. If the block 180/// is unreachable in this function, the set will be empty. This cannot happen 181/// for reachable code, because every block dominates at least itself. 182/// 183class DominatorSetBase : public DominatorBase { 184public: 185 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 186 // Map of dom sets 187 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; 188protected: 189 DomSetMapType Doms; 190public: 191 DominatorSetBase(bool isPostDom) : DominatorBase(isPostDom) {} 192 193 virtual void releaseMemory() { Doms.clear(); } 194 195 // Accessor interface: 196 typedef DomSetMapType::const_iterator const_iterator; 197 typedef DomSetMapType::iterator iterator; 198 inline const_iterator begin() const { return Doms.begin(); } 199 inline iterator begin() { return Doms.begin(); } 200 inline const_iterator end() const { return Doms.end(); } 201 inline iterator end() { return Doms.end(); } 202 inline const_iterator find(BasicBlock* B) const { return Doms.find(B); } 203 inline iterator find(BasicBlock* B) { return Doms.find(B); } 204 205 206 /// getDominators - Return the set of basic blocks that dominate the specified 207 /// block. 208 /// 209 inline const DomSetType &getDominators(BasicBlock *BB) const { 210 const_iterator I = find(BB); 211 assert(I != end() && "BB not in function!"); 212 return I->second; 213 } 214 215 /// isReachable - Return true if the specified basicblock is reachable. If 216 /// the block is reachable, we have dominator set information for it. 217 /// 218 bool isReachable(BasicBlock *BB) const { 219 return !getDominators(BB).empty(); 220 } 221 222 /// dominates - Return true if A dominates B. 223 /// 224 inline bool dominates(BasicBlock *A, BasicBlock *B) const { 225 return getDominators(B).count(A) != 0; 226 } 227 228 /// properlyDominates - Return true if A dominates B and A != B. 229 /// 230 bool properlyDominates(BasicBlock *A, BasicBlock *B) const { 231 return dominates(A, B) && A != B; 232 } 233 234 /// print - Convert to human readable form 235 /// 236 virtual void print(std::ostream &OS, const Module* = 0) const; 237 238 /// dominates - Return true if A dominates B. This performs the special 239 /// checks necessary if A and B are in the same basic block. 240 /// 241 bool dominates(Instruction *A, Instruction *B) const; 242 243 //===--------------------------------------------------------------------===// 244 // API to update (Post)DominatorSet information based on modifications to 245 // the CFG... 246 247 /// addBasicBlock - Call to update the dominator set with information about a 248 /// new block that was inserted into the function. 249 /// 250 void addBasicBlock(BasicBlock *BB, const DomSetType &Dominators) { 251 assert(find(BB) == end() && "Block already in DominatorSet!"); 252 Doms.insert(std::make_pair(BB, Dominators)); 253 } 254 255 /// addDominator - If a new block is inserted into the CFG, then method may be 256 /// called to notify the blocks it dominates that it is in their set. 257 /// 258 void addDominator(BasicBlock *BB, BasicBlock *NewDominator) { 259 iterator I = find(BB); 260 assert(I != end() && "BB is not in DominatorSet!"); 261 I->second.insert(NewDominator); 262 } 263}; 264 265 266//===------------------------------------- 267/// DominatorSet Class - Concrete subclass of DominatorSetBase that is used to 268/// compute a normal dominator set. 269/// 270class DominatorSet : public DominatorSetBase { 271public: 272 DominatorSet() : DominatorSetBase(false) {} 273 274 virtual bool runOnFunction(Function &F); 275 276 BasicBlock *getRoot() const { 277 assert(Roots.size() == 1 && "Should always have entry node!"); 278 return Roots[0]; 279 } 280 281 /// getAnalysisUsage - This simply provides a dominator set 282 /// 283 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 284 AU.addRequired<ImmediateDominators>(); 285 AU.setPreservesAll(); 286 } 287 288 // stub - dummy function, just ignore it 289 static int stub; 290}; 291 292 293//===----------------------------------------------------------------------===// 294/// DominatorTree - Calculate the immediate dominator tree for a function. 295/// 296class DominatorTreeBase : public DominatorBase { 297public: 298 class Node; 299protected: 300 std::map<BasicBlock*, Node*> Nodes; 301 void reset(); 302 typedef std::map<BasicBlock*, Node*> NodeMapType; 303 304 Node *RootNode; 305public: 306 class Node { 307 friend struct DominatorTree; 308 friend struct PostDominatorTree; 309 friend struct DominatorTreeBase; 310 BasicBlock *TheBB; 311 Node *IDom; 312 std::vector<Node*> Children; 313 public: 314 typedef std::vector<Node*>::iterator iterator; 315 typedef std::vector<Node*>::const_iterator const_iterator; 316 317 iterator begin() { return Children.begin(); } 318 iterator end() { return Children.end(); } 319 const_iterator begin() const { return Children.begin(); } 320 const_iterator end() const { return Children.end(); } 321 322 inline BasicBlock *getBlock() const { return TheBB; } 323 inline Node *getIDom() const { return IDom; } 324 inline const std::vector<Node*> &getChildren() const { return Children; } 325 326 /// properlyDominates - Returns true iff this dominates N and this != N. 327 /// Note that this is not a constant time operation! 328 /// 329 bool properlyDominates(const Node *N) const { 330 const Node *IDom; 331 if (this == 0 || N == 0) return false; 332 while ((IDom = N->getIDom()) != 0 && IDom != this) 333 N = IDom; // Walk up the tree 334 return IDom != 0; 335 } 336 337 /// dominates - Returns true iff this dominates N. Note that this is not a 338 /// constant time operation! 339 /// 340 inline bool dominates(const Node *N) const { 341 if (N == this) return true; // A node trivially dominates itself. 342 return properlyDominates(N); 343 } 344 345 private: 346 inline Node(BasicBlock *BB, Node *iDom) : TheBB(BB), IDom(iDom) {} 347 inline Node *addChild(Node *C) { Children.push_back(C); return C; } 348 349 void setIDom(Node *NewIDom); 350 }; 351 352public: 353 DominatorTreeBase(bool isPostDom) : DominatorBase(isPostDom) {} 354 ~DominatorTreeBase() { reset(); } 355 356 virtual void releaseMemory() { reset(); } 357 358 /// getNode - return the (Post)DominatorTree node for the specified basic 359 /// block. This is the same as using operator[] on this class. 360 /// 361 inline Node *getNode(BasicBlock *BB) const { 362 NodeMapType::const_iterator i = Nodes.find(BB); 363 return (i != Nodes.end()) ? i->second : 0; 364 } 365 366 inline Node *operator[](BasicBlock *BB) const { 367 return getNode(BB); 368 } 369 370 /// getRootNode - This returns the entry node for the CFG of the function. If 371 /// this tree represents the post-dominance relations for a function, however, 372 /// this root may be a node with the block == NULL. This is the case when 373 /// there are multiple exit nodes from a particular function. Consumers of 374 /// post-dominance information must be capable of dealing with this 375 /// possibility. 376 /// 377 Node *getRootNode() { return RootNode; } 378 const Node *getRootNode() const { return RootNode; } 379 380 //===--------------------------------------------------------------------===// 381 // API to update (Post)DominatorTree information based on modifications to 382 // the CFG... 383 384 /// createNewNode - Add a new node to the dominator tree information. This 385 /// creates a new node as a child of IDomNode, linking it into the children 386 /// list of the immediate dominator. 387 /// 388 Node *createNewNode(BasicBlock *BB, Node *IDomNode) { 389 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 390 assert(IDomNode && "Not immediate dominator specified for block!"); 391 return Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode)); 392 } 393 394 /// changeImmediateDominator - This method is used to update the dominator 395 /// tree information when a node's immediate dominator changes. 396 /// 397 void changeImmediateDominator(Node *N, Node *NewIDom) { 398 assert(N && NewIDom && "Cannot change null node pointers!"); 399 N->setIDom(NewIDom); 400 } 401 402 /// removeNode - Removes a node from the dominator tree. Block must not 403 /// dominate any other blocks. Invalidates any node pointing to removed 404 /// block. 405 void removeNode(BasicBlock *BB) { 406 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 407 Nodes.erase(BB); 408 } 409 410 /// print - Convert to human readable form 411 /// 412 virtual void print(std::ostream &OS, const Module* = 0) const; 413}; 414 415//===------------------------------------- 416/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 417/// compute a normal dominator tree. 418/// 419class DominatorTree : public DominatorTreeBase { 420public: 421 DominatorTree() : DominatorTreeBase(false) {} 422 423 BasicBlock *getRoot() const { 424 assert(Roots.size() == 1 && "Should always have entry node!"); 425 return Roots[0]; 426 } 427 428 virtual bool runOnFunction(Function &F) { 429 reset(); // Reset from the last time we were run... 430 ImmediateDominators &ID = getAnalysis<ImmediateDominators>(); 431 Roots = ID.getRoots(); 432 calculate(ID); 433 return false; 434 } 435 436 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 437 AU.setPreservesAll(); 438 AU.addRequired<ImmediateDominators>(); 439 } 440private: 441 void calculate(const ImmediateDominators &ID); 442 Node *getNodeForBlock(BasicBlock *BB); 443}; 444 445//===------------------------------------- 446/// DominatorTree GraphTraits specialization so the DominatorTree can be 447/// iterable by generic graph iterators. 448/// 449template <> struct GraphTraits<DominatorTree::Node*> { 450 typedef DominatorTree::Node NodeType; 451 typedef NodeType::iterator ChildIteratorType; 452 453 static NodeType *getEntryNode(NodeType *N) { 454 return N; 455 } 456 static inline ChildIteratorType child_begin(NodeType* N) { 457 return N->begin(); 458 } 459 static inline ChildIteratorType child_end(NodeType* N) { 460 return N->end(); 461 } 462}; 463 464template <> struct GraphTraits<DominatorTree*> 465 : public GraphTraits<DominatorTree::Node*> { 466 static NodeType *getEntryNode(DominatorTree *DT) { 467 return DT->getRootNode(); 468 } 469}; 470 471 472//===------------------------------------- 473/// ET-Forest Class - Class used to construct forwards and backwards 474/// ET-Forests 475/// 476class ETForestBase : public DominatorBase { 477public: 478 ETForestBase(bool isPostDom) : DominatorBase(isPostDom), Nodes(), 479 DFSInfoValid(false), SlowQueries(0) {} 480 481 virtual void releaseMemory() { reset(); } 482 483 typedef std::map<BasicBlock*, ETNode*> ETMapType; 484 485 void updateDFSNumbers(); 486 487 /// dominates - Return true if A dominates B. 488 /// 489 inline bool dominates(BasicBlock *A, BasicBlock *B) { 490 if (A == B) 491 return true; 492 493 ETNode *NodeA = getNode(A); 494 ETNode *NodeB = getNode(B); 495 496 if (DFSInfoValid) 497 return NodeB->DominatedBy(NodeA); 498 else { 499 // If we end up with too many slow queries, just update the 500 // DFS numbers on the theory that we are going to keep querying. 501 SlowQueries++; 502 if (SlowQueries > 32) { 503 updateDFSNumbers(); 504 return NodeB->DominatedBy(NodeA); 505 } 506 return NodeB->DominatedBySlow(NodeA); 507 } 508 } 509 510 /// properlyDominates - Return true if A dominates B and A != B. 511 /// 512 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 513 return dominates(A, B) && A != B; 514 } 515 516 /// Return the nearest common dominator of A and B. 517 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 518 ETNode *NodeA = getNode(A); 519 ETNode *NodeB = getNode(B); 520 521 ETNode *Common = NodeA->NCA(NodeB); 522 if (!Common) 523 return NULL; 524 return Common->getData<BasicBlock>(); 525 } 526 527 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 528 AU.setPreservesAll(); 529 AU.addRequired<ImmediateDominators>(); 530 } 531 //===--------------------------------------------------------------------===// 532 // API to update Forest information based on modifications 533 // to the CFG... 534 535 /// addNewBlock - Add a new block to the CFG, with the specified immediate 536 /// dominator. 537 /// 538 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 539 540 /// setImmediateDominator - Update the immediate dominator information to 541 /// change the current immediate dominator for the specified block 542 /// to another block. This method requires that BB for NewIDom 543 /// already have an ETNode, otherwise just use addNewBlock. 544 /// 545 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 546 /// print - Convert to human readable form 547 /// 548 virtual void print(std::ostream &OS, const Module* = 0) const; 549protected: 550 /// getNode - return the (Post)DominatorTree node for the specified basic 551 /// block. This is the same as using operator[] on this class. 552 /// 553 inline ETNode *getNode(BasicBlock *BB) const { 554 ETMapType::const_iterator i = Nodes.find(BB); 555 return (i != Nodes.end()) ? i->second : 0; 556 } 557 558 inline ETNode *operator[](BasicBlock *BB) const { 559 return getNode(BB); 560 } 561 562 void reset(); 563 ETMapType Nodes; 564 bool DFSInfoValid; 565 unsigned int SlowQueries; 566 567}; 568 569//==------------------------------------- 570/// ETForest Class - Concrete subclass of ETForestBase that is used to 571/// compute a forwards ET-Forest. 572 573class ETForest : public ETForestBase { 574public: 575 ETForest() : ETForestBase(false) {} 576 577 BasicBlock *getRoot() const { 578 assert(Roots.size() == 1 && "Should always have entry node!"); 579 return Roots[0]; 580 } 581 582 virtual bool runOnFunction(Function &F) { 583 reset(); // Reset from the last time we were run... 584 ImmediateDominators &ID = getAnalysis<ImmediateDominators>(); 585 Roots = ID.getRoots(); 586 calculate(ID); 587 return false; 588 } 589 590 void calculate(const ImmediateDominators &ID); 591 ETNode *getNodeForBlock(BasicBlock *BB); 592}; 593 594//===----------------------------------------------------------------------===// 595/// DominanceFrontierBase - Common base class for computing forward and inverse 596/// dominance frontiers for a function. 597/// 598class DominanceFrontierBase : public DominatorBase { 599public: 600 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 601 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 602protected: 603 DomSetMapType Frontiers; 604public: 605 DominanceFrontierBase(bool isPostDom) : DominatorBase(isPostDom) {} 606 607 virtual void releaseMemory() { Frontiers.clear(); } 608 609 // Accessor interface: 610 typedef DomSetMapType::iterator iterator; 611 typedef DomSetMapType::const_iterator const_iterator; 612 iterator begin() { return Frontiers.begin(); } 613 const_iterator begin() const { return Frontiers.begin(); } 614 iterator end() { return Frontiers.end(); } 615 const_iterator end() const { return Frontiers.end(); } 616 iterator find(BasicBlock *B) { return Frontiers.find(B); } 617 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 618 619 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 620 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 621 Frontiers.insert(std::make_pair(BB, frontier)); 622 } 623 624 void addToFrontier(iterator I, BasicBlock *Node) { 625 assert(I != end() && "BB is not in DominanceFrontier!"); 626 I->second.insert(Node); 627 } 628 629 void removeFromFrontier(iterator I, BasicBlock *Node) { 630 assert(I != end() && "BB is not in DominanceFrontier!"); 631 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 632 I->second.erase(Node); 633 } 634 635 /// print - Convert to human readable form 636 /// 637 virtual void print(std::ostream &OS, const Module* = 0) const; 638}; 639 640 641//===------------------------------------- 642/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 643/// used to compute a forward dominator frontiers. 644/// 645class DominanceFrontier : public DominanceFrontierBase { 646public: 647 DominanceFrontier() : DominanceFrontierBase(false) {} 648 649 BasicBlock *getRoot() const { 650 assert(Roots.size() == 1 && "Should always have entry node!"); 651 return Roots[0]; 652 } 653 654 virtual bool runOnFunction(Function &) { 655 Frontiers.clear(); 656 DominatorTree &DT = getAnalysis<DominatorTree>(); 657 Roots = DT.getRoots(); 658 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 659 calculate(DT, DT[Roots[0]]); 660 return false; 661 } 662 663 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 664 AU.setPreservesAll(); 665 AU.addRequired<DominatorTree>(); 666 } 667private: 668 const DomSetType &calculate(const DominatorTree &DT, 669 const DominatorTree::Node *Node); 670}; 671 672 673} // End llvm namespace 674 675// Make sure that any clients of this file link in Dominators.cpp 676FORCE_DEFINING_FILE_TO_BE_LINKED(DominatorSet) 677 678#endif 679