Dominators.h revision ba43963e96c9eb28d4f6862e46c5d3fbdc1f3b96
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. DominatorTree: Represent the ImmediateDominator as an explicit tree 14// structure. 15// 4. ETForest: Efficient data structure for dominance comparisons and 16// nearest-common-ancestor queries. 17// 5. DominanceFrontier: Calculate and hold the dominance frontier for a 18// function. 19// 20// These data structures are listed in increasing order of complexity. It 21// takes longer to calculate the dominator frontier, for example, than the 22// ImmediateDominator mapping. 23// 24//===----------------------------------------------------------------------===// 25 26#ifndef LLVM_ANALYSIS_DOMINATORS_H 27#define LLVM_ANALYSIS_DOMINATORS_H 28 29#include "llvm/Analysis/ET-Forest.h" 30#include "llvm/Pass.h" 31#include <set> 32 33namespace llvm { 34 35class Instruction; 36 37template <typename GraphType> struct GraphTraits; 38 39//===----------------------------------------------------------------------===// 40/// DominatorBase - Base class that other, more interesting dominator analyses 41/// inherit from. 42/// 43class DominatorBase : public FunctionPass { 44protected: 45 std::vector<BasicBlock*> Roots; 46 const bool IsPostDominators; 47 48 inline DominatorBase(bool isPostDom) : Roots(), IsPostDominators(isPostDom) {} 49public: 50 /// getRoots - Return the root blocks of the current CFG. This may include 51 /// multiple blocks if we are computing post dominators. For forward 52 /// dominators, this will always be a single block (the entry node). 53 /// 54 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 55 56 /// isPostDominator - Returns true if analysis based of postdoms 57 /// 58 bool isPostDominator() const { return IsPostDominators; } 59}; 60 61 62//===----------------------------------------------------------------------===// 63/// ImmediateDominators - Calculate the immediate dominator for each node in a 64/// function. 65/// 66class ImmediateDominatorsBase : public DominatorBase { 67protected: 68 struct InfoRec { 69 unsigned Semi; 70 unsigned Size; 71 BasicBlock *Label, *Parent, *Child, *Ancestor; 72 73 std::vector<BasicBlock*> Bucket; 74 75 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 76 }; 77 78 std::map<BasicBlock*, BasicBlock*> IDoms; 79 80 // Vertex - Map the DFS number to the BasicBlock* 81 std::vector<BasicBlock*> Vertex; 82 83 // Info - Collection of information used during the computation of idoms. 84 std::map<BasicBlock*, InfoRec> Info; 85public: 86 ImmediateDominatorsBase(bool isPostDom) : DominatorBase(isPostDom) {} 87 88 virtual void releaseMemory() { IDoms.clear(); } 89 90 // Accessor interface: 91 typedef std::map<BasicBlock*, BasicBlock*> IDomMapType; 92 typedef IDomMapType::const_iterator const_iterator; 93 inline const_iterator begin() const { return IDoms.begin(); } 94 inline const_iterator end() const { return IDoms.end(); } 95 inline const_iterator find(BasicBlock* B) const { return IDoms.find(B);} 96 97 /// operator[] - Return the idom for the specified basic block. The start 98 /// node returns null, because it does not have an immediate dominator. 99 /// 100 inline BasicBlock *operator[](BasicBlock *BB) const { 101 return get(BB); 102 } 103 104 /// dominates - Return true if A dominates B. 105 /// 106 bool dominates(BasicBlock *A, BasicBlock *B) const; 107 108 /// properlyDominates - Return true if A dominates B and A != B. 109 /// 110 bool properlyDominates(BasicBlock *A, BasicBlock *B) const { 111 return A != B || properlyDominates(A, B); 112 } 113 114 /// get() - Synonym for operator[]. 115 /// 116 inline BasicBlock *get(BasicBlock *BB) const { 117 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 118 return I != IDoms.end() ? I->second : 0; 119 } 120 121 //===--------------------------------------------------------------------===// 122 // API to update Immediate(Post)Dominators information based on modifications 123 // to the CFG... 124 125 /// addNewBlock - Add a new block to the CFG, with the specified immediate 126 /// dominator. 127 /// 128 void addNewBlock(BasicBlock *BB, BasicBlock *IDom) { 129 assert(get(BB) == 0 && "BasicBlock already in idom info!"); 130 IDoms[BB] = IDom; 131 } 132 133 /// setImmediateDominator - Update the immediate dominator information to 134 /// change the current immediate dominator for the specified block to another 135 /// block. This method requires that BB already have an IDom, otherwise just 136 /// use addNewBlock. 137 /// 138 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom) { 139 assert(IDoms.find(BB) != IDoms.end() && "BB doesn't have idom yet!"); 140 IDoms[BB] = NewIDom; 141 } 142 143 /// print - Convert to human readable form 144 /// 145 virtual void print(std::ostream &OS, const Module* = 0) const; 146 void print(std::ostream *OS, const Module* M = 0) const { 147 if (OS) print(*OS, M); 148 } 149}; 150 151//===------------------------------------- 152/// ImmediateDominators Class - Concrete subclass of ImmediateDominatorsBase 153/// that is used to compute a normal immediate dominator set. 154/// 155class ImmediateDominators : public ImmediateDominatorsBase { 156public: 157 ImmediateDominators() : ImmediateDominatorsBase(false) {} 158 159 BasicBlock *getRoot() const { 160 assert(Roots.size() == 1 && "Should always have entry node!"); 161 return Roots[0]; 162 } 163 164 virtual bool runOnFunction(Function &F); 165 166 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 167 AU.setPreservesAll(); 168 } 169 170private: 171 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 172 void Compress(BasicBlock *V, InfoRec &VInfo); 173 BasicBlock *Eval(BasicBlock *v); 174 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 175}; 176 177//===----------------------------------------------------------------------===// 178/// DominatorTree - Calculate the immediate dominator tree for a function. 179/// 180class DominatorTreeBase : public DominatorBase { 181public: 182 class Node; 183protected: 184 std::map<BasicBlock*, Node*> Nodes; 185 void reset(); 186 typedef std::map<BasicBlock*, Node*> NodeMapType; 187 188 Node *RootNode; 189public: 190 class Node { 191 friend class DominatorTree; 192 friend struct PostDominatorTree; 193 friend class DominatorTreeBase; 194 BasicBlock *TheBB; 195 Node *IDom; 196 std::vector<Node*> Children; 197 public: 198 typedef std::vector<Node*>::iterator iterator; 199 typedef std::vector<Node*>::const_iterator const_iterator; 200 201 iterator begin() { return Children.begin(); } 202 iterator end() { return Children.end(); } 203 const_iterator begin() const { return Children.begin(); } 204 const_iterator end() const { return Children.end(); } 205 206 inline BasicBlock *getBlock() const { return TheBB; } 207 inline Node *getIDom() const { return IDom; } 208 inline const std::vector<Node*> &getChildren() const { return Children; } 209 210 /// properlyDominates - Returns true iff this dominates N and this != N. 211 /// Note that this is not a constant time operation! 212 /// 213 bool properlyDominates(const Node *N) const { 214 const Node *IDom; 215 if (this == 0 || N == 0) return false; 216 while ((IDom = N->getIDom()) != 0 && IDom != this) 217 N = IDom; // Walk up the tree 218 return IDom != 0; 219 } 220 221 /// dominates - Returns true iff this dominates N. Note that this is not a 222 /// constant time operation! 223 /// 224 inline bool dominates(const Node *N) const { 225 if (N == this) return true; // A node trivially dominates itself. 226 return properlyDominates(N); 227 } 228 229 private: 230 inline Node(BasicBlock *BB, Node *iDom) : TheBB(BB), IDom(iDom) {} 231 inline Node *addChild(Node *C) { Children.push_back(C); return C; } 232 233 void setIDom(Node *NewIDom); 234 }; 235 236public: 237 DominatorTreeBase(bool isPostDom) : DominatorBase(isPostDom) {} 238 ~DominatorTreeBase() { reset(); } 239 240 virtual void releaseMemory() { reset(); } 241 242 /// getNode - return the (Post)DominatorTree node for the specified basic 243 /// block. This is the same as using operator[] on this class. 244 /// 245 inline Node *getNode(BasicBlock *BB) const { 246 NodeMapType::const_iterator i = Nodes.find(BB); 247 return (i != Nodes.end()) ? i->second : 0; 248 } 249 250 inline Node *operator[](BasicBlock *BB) const { 251 return getNode(BB); 252 } 253 254 /// getRootNode - This returns the entry node for the CFG of the function. If 255 /// this tree represents the post-dominance relations for a function, however, 256 /// this root may be a node with the block == NULL. This is the case when 257 /// there are multiple exit nodes from a particular function. Consumers of 258 /// post-dominance information must be capable of dealing with this 259 /// possibility. 260 /// 261 Node *getRootNode() { return RootNode; } 262 const Node *getRootNode() const { return RootNode; } 263 264 //===--------------------------------------------------------------------===// 265 // API to update (Post)DominatorTree information based on modifications to 266 // the CFG... 267 268 /// createNewNode - Add a new node to the dominator tree information. This 269 /// creates a new node as a child of IDomNode, linking it into the children 270 /// list of the immediate dominator. 271 /// 272 Node *createNewNode(BasicBlock *BB, Node *IDomNode) { 273 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 274 assert(IDomNode && "Not immediate dominator specified for block!"); 275 return Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode)); 276 } 277 278 /// changeImmediateDominator - This method is used to update the dominator 279 /// tree information when a node's immediate dominator changes. 280 /// 281 void changeImmediateDominator(Node *N, Node *NewIDom) { 282 assert(N && NewIDom && "Cannot change null node pointers!"); 283 N->setIDom(NewIDom); 284 } 285 286 /// removeNode - Removes a node from the dominator tree. Block must not 287 /// dominate any other blocks. Invalidates any node pointing to removed 288 /// block. 289 void removeNode(BasicBlock *BB) { 290 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 291 Nodes.erase(BB); 292 } 293 294 /// print - Convert to human readable form 295 /// 296 virtual void print(std::ostream &OS, const Module* = 0) const; 297 void print(std::ostream *OS, const Module* M = 0) const { 298 if (OS) print(*OS, M); 299 } 300}; 301 302//===------------------------------------- 303/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 304/// compute a normal dominator tree. 305/// 306class DominatorTree : public DominatorTreeBase { 307public: 308 DominatorTree() : DominatorTreeBase(false) {} 309 310 BasicBlock *getRoot() const { 311 assert(Roots.size() == 1 && "Should always have entry node!"); 312 return Roots[0]; 313 } 314 315 virtual bool runOnFunction(Function &F) { 316 reset(); // Reset from the last time we were run... 317 ImmediateDominators &ID = getAnalysis<ImmediateDominators>(); 318 Roots = ID.getRoots(); 319 calculate(ID); 320 return false; 321 } 322 323 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 324 AU.setPreservesAll(); 325 AU.addRequired<ImmediateDominators>(); 326 } 327private: 328 void calculate(const ImmediateDominators &ID); 329 Node *getNodeForBlock(BasicBlock *BB); 330}; 331 332//===------------------------------------- 333/// DominatorTree GraphTraits specialization so the DominatorTree can be 334/// iterable by generic graph iterators. 335/// 336template <> struct GraphTraits<DominatorTree::Node*> { 337 typedef DominatorTree::Node NodeType; 338 typedef NodeType::iterator ChildIteratorType; 339 340 static NodeType *getEntryNode(NodeType *N) { 341 return N; 342 } 343 static inline ChildIteratorType child_begin(NodeType* N) { 344 return N->begin(); 345 } 346 static inline ChildIteratorType child_end(NodeType* N) { 347 return N->end(); 348 } 349}; 350 351template <> struct GraphTraits<DominatorTree*> 352 : public GraphTraits<DominatorTree::Node*> { 353 static NodeType *getEntryNode(DominatorTree *DT) { 354 return DT->getRootNode(); 355 } 356}; 357 358 359//===------------------------------------- 360/// ET-Forest Class - Class used to construct forwards and backwards 361/// ET-Forests 362/// 363class ETForestBase : public DominatorBase { 364public: 365 ETForestBase(bool isPostDom) : DominatorBase(isPostDom), Nodes(), 366 DFSInfoValid(false), SlowQueries(0) {} 367 368 virtual void releaseMemory() { reset(); } 369 370 typedef std::map<BasicBlock*, ETNode*> ETMapType; 371 372 void updateDFSNumbers(); 373 374 /// dominates - Return true if A dominates B. 375 /// 376 inline bool dominates(BasicBlock *A, BasicBlock *B) { 377 if (A == B) 378 return true; 379 380 ETNode *NodeA = getNode(A); 381 ETNode *NodeB = getNode(B); 382 383 if (DFSInfoValid) 384 return NodeB->DominatedBy(NodeA); 385 else { 386 // If we end up with too many slow queries, just update the 387 // DFS numbers on the theory that we are going to keep querying. 388 SlowQueries++; 389 if (SlowQueries > 32) { 390 updateDFSNumbers(); 391 return NodeB->DominatedBy(NodeA); 392 } 393 return NodeB->DominatedBySlow(NodeA); 394 } 395 } 396 397 // dominates - Return true if A dominates B. THis performs the 398 // special checks necessary if A and B are in the same basic block. 399 bool dominates(Instruction *A, Instruction *B); 400 401 /// properlyDominates - Return true if A dominates B and A != B. 402 /// 403 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 404 return dominates(A, B) && A != B; 405 } 406 407 /// Return the nearest common dominator of A and B. 408 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 409 ETNode *NodeA = getNode(A); 410 ETNode *NodeB = getNode(B); 411 412 ETNode *Common = NodeA->NCA(NodeB); 413 if (!Common) 414 return NULL; 415 return Common->getData<BasicBlock>(); 416 } 417 418 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 419 AU.setPreservesAll(); 420 AU.addRequired<ImmediateDominators>(); 421 } 422 //===--------------------------------------------------------------------===// 423 // API to update Forest information based on modifications 424 // to the CFG... 425 426 /// addNewBlock - Add a new block to the CFG, with the specified immediate 427 /// dominator. 428 /// 429 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 430 431 /// setImmediateDominator - Update the immediate dominator information to 432 /// change the current immediate dominator for the specified block 433 /// to another block. This method requires that BB for NewIDom 434 /// already have an ETNode, otherwise just use addNewBlock. 435 /// 436 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 437 /// print - Convert to human readable form 438 /// 439 virtual void print(std::ostream &OS, const Module* = 0) const; 440 void print(std::ostream *OS, const Module* M = 0) const { 441 if (OS) print(*OS, M); 442 } 443protected: 444 /// getNode - return the (Post)DominatorTree node for the specified basic 445 /// block. This is the same as using operator[] on this class. 446 /// 447 inline ETNode *getNode(BasicBlock *BB) const { 448 ETMapType::const_iterator i = Nodes.find(BB); 449 return (i != Nodes.end()) ? i->second : 0; 450 } 451 452 inline ETNode *operator[](BasicBlock *BB) const { 453 return getNode(BB); 454 } 455 456 void reset(); 457 ETMapType Nodes; 458 bool DFSInfoValid; 459 unsigned int SlowQueries; 460 461}; 462 463//==------------------------------------- 464/// ETForest Class - Concrete subclass of ETForestBase that is used to 465/// compute a forwards ET-Forest. 466 467class ETForest : public ETForestBase { 468public: 469 ETForest() : ETForestBase(false) {} 470 471 BasicBlock *getRoot() const { 472 assert(Roots.size() == 1 && "Should always have entry node!"); 473 return Roots[0]; 474 } 475 476 virtual bool runOnFunction(Function &F) { 477 reset(); // Reset from the last time we were run... 478 ImmediateDominators &ID = getAnalysis<ImmediateDominators>(); 479 Roots = ID.getRoots(); 480 calculate(ID); 481 return false; 482 } 483 484 void calculate(const ImmediateDominators &ID); 485 ETNode *getNodeForBlock(BasicBlock *BB); 486}; 487 488//===----------------------------------------------------------------------===// 489/// DominanceFrontierBase - Common base class for computing forward and inverse 490/// dominance frontiers for a function. 491/// 492class DominanceFrontierBase : public DominatorBase { 493public: 494 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 495 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 496protected: 497 DomSetMapType Frontiers; 498public: 499 DominanceFrontierBase(bool isPostDom) : DominatorBase(isPostDom) {} 500 501 virtual void releaseMemory() { Frontiers.clear(); } 502 503 // Accessor interface: 504 typedef DomSetMapType::iterator iterator; 505 typedef DomSetMapType::const_iterator const_iterator; 506 iterator begin() { return Frontiers.begin(); } 507 const_iterator begin() const { return Frontiers.begin(); } 508 iterator end() { return Frontiers.end(); } 509 const_iterator end() const { return Frontiers.end(); } 510 iterator find(BasicBlock *B) { return Frontiers.find(B); } 511 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 512 513 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 514 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 515 Frontiers.insert(std::make_pair(BB, frontier)); 516 } 517 518 void addToFrontier(iterator I, BasicBlock *Node) { 519 assert(I != end() && "BB is not in DominanceFrontier!"); 520 I->second.insert(Node); 521 } 522 523 void removeFromFrontier(iterator I, BasicBlock *Node) { 524 assert(I != end() && "BB is not in DominanceFrontier!"); 525 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 526 I->second.erase(Node); 527 } 528 529 /// print - Convert to human readable form 530 /// 531 virtual void print(std::ostream &OS, const Module* = 0) const; 532 void print(std::ostream *OS, const Module* M = 0) const { 533 if (OS) print(*OS, M); 534 } 535}; 536 537 538//===------------------------------------- 539/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 540/// used to compute a forward dominator frontiers. 541/// 542class DominanceFrontier : public DominanceFrontierBase { 543public: 544 DominanceFrontier() : DominanceFrontierBase(false) {} 545 546 BasicBlock *getRoot() const { 547 assert(Roots.size() == 1 && "Should always have entry node!"); 548 return Roots[0]; 549 } 550 551 virtual bool runOnFunction(Function &) { 552 Frontiers.clear(); 553 DominatorTree &DT = getAnalysis<DominatorTree>(); 554 Roots = DT.getRoots(); 555 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 556 calculate(DT, DT[Roots[0]]); 557 return false; 558 } 559 560 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 561 AU.setPreservesAll(); 562 AU.addRequired<DominatorTree>(); 563 } 564private: 565 const DomSetType &calculate(const DominatorTree &DT, 566 const DominatorTree::Node *Node); 567}; 568 569 570} // End llvm namespace 571 572#endif 573