Dominators.h revision fe7d4e50b8a34e660a8713da79613041987c19d6
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. DominatorTree: Represent dominators as an explicit tree structure. 12// 2. ETForest: Efficient data structure for dominance comparisons and 13// nearest-common-ancestor queries. 14// 3. DominanceFrontier: Calculate and hold the dominance frontier for a 15// function. 16// 17// These data structures are listed in increasing order of complexity. It 18// takes longer to calculate the dominator frontier, for example, than the 19// DominatorTree mapping. 20// 21//===----------------------------------------------------------------------===// 22 23#ifndef LLVM_ANALYSIS_DOMINATORS_H 24#define LLVM_ANALYSIS_DOMINATORS_H 25 26#include "llvm/Analysis/ET-Forest.h" 27#include "llvm/Pass.h" 28#include <set> 29 30namespace llvm { 31 32class Instruction; 33 34template <typename GraphType> struct GraphTraits; 35 36//===----------------------------------------------------------------------===// 37/// DominatorBase - Base class that other, more interesting dominator analyses 38/// inherit from. 39/// 40class DominatorBase : public FunctionPass { 41protected: 42 std::vector<BasicBlock*> Roots; 43 const bool IsPostDominators; 44 inline DominatorBase(intptr_t ID, bool isPostDom) : 45 FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {} 46public: 47 48 /// getRoots - Return the root blocks of the current CFG. This may include 49 /// multiple blocks if we are computing post dominators. For forward 50 /// dominators, this will always be a single block (the entry node). 51 /// 52 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 53 54 /// isPostDominator - Returns true if analysis based of postdoms 55 /// 56 bool isPostDominator() const { return IsPostDominators; } 57}; 58 59 60//===----------------------------------------------------------------------===// 61// DomTreeNode - Dominator Tree Node 62 63class DomTreeNode { 64 BasicBlock *TheBB; 65 DomTreeNode *IDom; 66 ETNode *ETN; 67 std::vector<DomTreeNode*> Children; 68public: 69 typedef std::vector<DomTreeNode*>::iterator iterator; 70 typedef std::vector<DomTreeNode*>::const_iterator const_iterator; 71 72 iterator begin() { return Children.begin(); } 73 iterator end() { return Children.end(); } 74 const_iterator begin() const { return Children.begin(); } 75 const_iterator end() const { return Children.end(); } 76 77 inline BasicBlock *getBlock() const { return TheBB; } 78 inline DomTreeNode *getIDom() const { return IDom; } 79 inline ETNode *getETNode() const { return ETN; } 80 inline const std::vector<DomTreeNode*> &getChildren() const { return Children; } 81 82 inline DomTreeNode(BasicBlock *BB, DomTreeNode *iDom, ETNode *E) 83 : TheBB(BB), IDom(iDom), ETN(E) { 84 if (IDom) 85 ETN->setFather(IDom->getETNode()); 86 } 87 inline DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; } 88 void setIDom(DomTreeNode *NewIDom); 89}; 90 91//===----------------------------------------------------------------------===// 92/// DominatorTree - Calculate the immediate dominator tree for a function. 93/// 94class DominatorTreeBase : public DominatorBase { 95 96protected: 97 void reset(); 98 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 99 DomTreeNodeMapType DomTreeNodes; 100 DomTreeNode *RootNode; 101 102 typedef std::map<BasicBlock*, ETNode*> ETMapType; 103 ETMapType ETNodes; 104 105 bool DFSInfoValid; 106 unsigned int SlowQueries; 107 // Information record used during immediate dominators computation. 108 struct InfoRec { 109 unsigned Semi; 110 unsigned Size; 111 BasicBlock *Label, *Parent, *Child, *Ancestor; 112 113 std::vector<BasicBlock*> Bucket; 114 115 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 116 }; 117 118 std::map<BasicBlock*, BasicBlock*> IDoms; 119 120 // Vertex - Map the DFS number to the BasicBlock* 121 std::vector<BasicBlock*> Vertex; 122 123 // Info - Collection of information used during the computation of idoms. 124 std::map<BasicBlock*, InfoRec> Info; 125 126 public: 127 DominatorTreeBase(intptr_t ID, bool isPostDom) 128 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {} 129 ~DominatorTreeBase() { reset(); } 130 131 virtual void releaseMemory() { reset(); } 132 133 /// getNode - return the (Post)DominatorTree node for the specified basic 134 /// block. This is the same as using operator[] on this class. 135 /// 136 inline DomTreeNode *getNode(BasicBlock *BB) const { 137 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB); 138 return (i != DomTreeNodes.end()) ? i->second : 0; 139 } 140 141 inline DomTreeNode *operator[](BasicBlock *BB) const { 142 return getNode(BB); 143 } 144 145 /// getIDomBlock - return basic block BB's immediate dominator basic block. 146 /// 147 BasicBlock *getIDomBlock(BasicBlock *BB) { 148 DomTreeNode *N = getNode(BB); 149 assert (N && "Missing dominator tree node"); 150 DomTreeNode *I = N->getIDom(); 151 assert (N && "Missing immediate dominator"); 152 return I->getBlock(); 153 } 154 155 /// getRootNode - This returns the entry node for the CFG of the function. If 156 /// this tree represents the post-dominance relations for a function, however, 157 /// this root may be a node with the block == NULL. This is the case when 158 /// there are multiple exit nodes from a particular function. Consumers of 159 /// post-dominance information must be capable of dealing with this 160 /// possibility. 161 /// 162 DomTreeNode *getRootNode() { return RootNode; } 163 const DomTreeNode *getRootNode() const { return RootNode; } 164 165 /// properlyDominates - Returns true iff this dominates N and this != N. 166 /// Note that this is not a constant time operation! 167 /// 168 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const { 169 if (A == 0 || B == 0) return false; 170 return dominatedBySlowTreeWalk(A, B); 171 } 172 173 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) { 174 return properlyDominates(getNode(A), getNode(B)); 175 } 176 177 bool dominatedBySlowTreeWalk(const DomTreeNode *A, 178 const DomTreeNode *B) const { 179 const DomTreeNode *IDom; 180 if (A == 0 || B == 0) return false; 181 while ((IDom = B->getIDom()) != 0 && IDom != A) 182 B = IDom; // Walk up the tree 183 return IDom != 0; 184 } 185 186 void updateDFSNumbers(); 187 188 /// Return the nearest common dominator of A and B. 189 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 190 ETNode *NodeA = getNode(A)->getETNode(); 191 ETNode *NodeB = getNode(B)->getETNode(); 192 193 ETNode *Common = NodeA->NCA(NodeB); 194 if (!Common) 195 return NULL; 196 return Common->getData<BasicBlock>(); 197 } 198 199 /// isReachableFromEntry - Return true if A is dominated by the entry 200 /// block of the function containing it. 201 const bool isReachableFromEntry(BasicBlock* A); 202 203 /// dominates - Returns true iff this dominates N. Note that this is not a 204 /// constant time operation! 205 /// 206 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) { 207 if (B == A) 208 return true; // A node trivially dominates itself. 209 210 if (A == 0 || B == 0) 211 return false; 212 213 ETNode *NodeA = A->getETNode(); 214 ETNode *NodeB = B->getETNode(); 215 216 if (DFSInfoValid) 217 return NodeB->DominatedBy(NodeA); 218 219 // If we end up with too many slow queries, just update the 220 // DFS numbers on the theory that we are going to keep querying. 221 SlowQueries++; 222 if (SlowQueries > 32) { 223 updateDFSNumbers(); 224 return NodeB->DominatedBy(NodeA); 225 } 226 //return NodeB->DominatedBySlow(NodeA); 227 return dominatedBySlowTreeWalk(A, B); 228 } 229 230 inline bool dominates(BasicBlock *A, BasicBlock *B) { 231 if (A == B) 232 return true; 233 234 return dominates(getNode(A), getNode(B)); 235 } 236 237 /// findNearestCommonDominator - Find nearest common dominator basic block 238 /// for basic block A and B. If there is no such block then return NULL. 239 BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B); 240 241 // dominates - Return true if A dominates B. This performs the 242 // special checks necessary if A and B are in the same basic block. 243 bool dominates(Instruction *A, Instruction *B); 244 245 //===--------------------------------------------------------------------===// 246 // API to update (Post)DominatorTree information based on modifications to 247 // the CFG... 248 249 /// addNewBlock - Add a new node to the dominator tree information. This 250 /// creates a new node as a child of DomBB dominator node,linking it into 251 /// the children list of the immediate dominator. 252 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 253 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 254 DomTreeNode *IDomNode = getNode(DomBB); 255 assert(IDomNode && "Not immediate dominator specified for block!"); 256 DFSInfoValid = false; 257 ETNode *E = new ETNode(BB); 258 ETNodes[BB] = E; 259 return DomTreeNodes[BB] = 260 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E)); 261 } 262 263 /// changeImmediateDominator - This method is used to update the dominator 264 /// tree information when a node's immediate dominator changes. 265 /// 266 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 267 assert(N && NewIDom && "Cannot change null node pointers!"); 268 DFSInfoValid = false; 269 N->setIDom(NewIDom); 270 } 271 272 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) { 273 changeImmediateDominator(getNode(BB), getNode(NewBB)); 274 } 275 276 /// removeNode - Removes a node from the dominator tree. Block must not 277 /// dominate any other blocks. Invalidates any node pointing to removed 278 /// block. 279 void removeNode(BasicBlock *BB) { 280 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 281 DomTreeNodes.erase(BB); 282 } 283 284 /// print - Convert to human readable form 285 /// 286 virtual void print(std::ostream &OS, const Module* = 0) const; 287 void print(std::ostream *OS, const Module* M = 0) const { 288 if (OS) print(*OS, M); 289 } 290 virtual void dump(); 291}; 292 293//===------------------------------------- 294/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 295/// compute a normal dominator tree. 296/// 297class DominatorTree : public DominatorTreeBase { 298public: 299 static char ID; // Pass ID, replacement for typeid 300 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 301 302 BasicBlock *getRoot() const { 303 assert(Roots.size() == 1 && "Should always have entry node!"); 304 return Roots[0]; 305 } 306 307 virtual bool runOnFunction(Function &F); 308 309 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 310 AU.setPreservesAll(); 311 } 312private: 313 void calculate(Function& F); 314 DomTreeNode *getNodeForBlock(BasicBlock *BB); 315 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 316 void Compress(BasicBlock *V); 317 BasicBlock *Eval(BasicBlock *v); 318 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 319 inline BasicBlock *getIDom(BasicBlock *BB) const { 320 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 321 return I != IDoms.end() ? I->second : 0; 322 } 323}; 324 325//===------------------------------------- 326/// DominatorTree GraphTraits specialization so the DominatorTree can be 327/// iterable by generic graph iterators. 328/// 329template <> struct GraphTraits<DomTreeNode*> { 330 typedef DomTreeNode NodeType; 331 typedef NodeType::iterator ChildIteratorType; 332 333 static NodeType *getEntryNode(NodeType *N) { 334 return N; 335 } 336 static inline ChildIteratorType child_begin(NodeType* N) { 337 return N->begin(); 338 } 339 static inline ChildIteratorType child_end(NodeType* N) { 340 return N->end(); 341 } 342}; 343 344template <> struct GraphTraits<DominatorTree*> 345 : public GraphTraits<DomTreeNode*> { 346 static NodeType *getEntryNode(DominatorTree *DT) { 347 return DT->getRootNode(); 348 } 349}; 350 351 352//===------------------------------------- 353/// ET-Forest Class - Class used to construct forwards and backwards 354/// ET-Forests 355/// 356class ETForestBase : public DominatorBase { 357public: 358 ETForestBase(intptr_t ID, bool isPostDom) 359 : DominatorBase(ID, isPostDom), Nodes(), 360 DFSInfoValid(false), SlowQueries(0) {} 361 362 virtual void releaseMemory() { reset(); } 363 364 typedef std::map<BasicBlock*, ETNode*> ETMapType; 365 366 // FIXME : There is no need to make this interface public. 367 // Fix predicate simplifier. 368 void updateDFSNumbers(); 369 370 /// dominates - Return true if A dominates B. 371 /// 372 inline bool dominates(BasicBlock *A, BasicBlock *B) { 373 if (A == B) 374 return true; 375 376 ETNode *NodeA = getNode(A); 377 ETNode *NodeB = getNode(B); 378 379 if (DFSInfoValid) 380 return NodeB->DominatedBy(NodeA); 381 else { 382 // If we end up with too many slow queries, just update the 383 // DFS numbers on the theory that we are going to keep querying. 384 SlowQueries++; 385 if (SlowQueries > 32) { 386 updateDFSNumbers(); 387 return NodeB->DominatedBy(NodeA); 388 } 389 return NodeB->DominatedBySlow(NodeA); 390 } 391 } 392 393 // dominates - Return true if A dominates B. This performs the 394 // special checks necessary if A and B are in the same basic block. 395 bool dominates(Instruction *A, Instruction *B); 396 397 /// properlyDominates - Return true if A dominates B and A != B. 398 /// 399 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 400 return dominates(A, B) && A != B; 401 } 402 403 /// isReachableFromEntry - Return true if A is dominated by the entry 404 /// block of the function containing it. 405 const bool isReachableFromEntry(BasicBlock* A); 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 /// Return the immediate dominator of A. 419 BasicBlock *getIDom(BasicBlock *A) const { 420 ETNode *NodeA = getNode(A); 421 if (!NodeA) return 0; 422 const ETNode *idom = NodeA->getFather(); 423 return idom ? idom->getData<BasicBlock>() : 0; 424 } 425 426 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const { 427 ETNode *NodeA = getNode(A); 428 if (!NodeA) return; 429 const ETNode* son = NodeA->getSon(); 430 431 if (!son) return; 432 children.push_back(son->getData<BasicBlock>()); 433 434 const ETNode* brother = son->getBrother(); 435 while (brother != son) { 436 children.push_back(brother->getData<BasicBlock>()); 437 brother = brother->getBrother(); 438 } 439 } 440 441 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 442 AU.setPreservesAll(); 443 AU.addRequired<DominatorTree>(); 444 } 445 //===--------------------------------------------------------------------===// 446 // API to update Forest information based on modifications 447 // to the CFG... 448 449 /// addNewBlock - Add a new block to the CFG, with the specified immediate 450 /// dominator. 451 /// 452 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 453 454 /// setImmediateDominator - Update the immediate dominator information to 455 /// change the current immediate dominator for the specified block 456 /// to another block. This method requires that BB for NewIDom 457 /// already have an ETNode, otherwise just use addNewBlock. 458 /// 459 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 460 /// print - Convert to human readable form 461 /// 462 virtual void print(std::ostream &OS, const Module* = 0) const; 463 void print(std::ostream *OS, const Module* M = 0) const { 464 if (OS) print(*OS, M); 465 } 466 virtual void dump(); 467protected: 468 /// getNode - return the (Post)DominatorTree node for the specified basic 469 /// block. This is the same as using operator[] on this class. 470 /// 471 inline ETNode *getNode(BasicBlock *BB) const { 472 ETMapType::const_iterator i = Nodes.find(BB); 473 return (i != Nodes.end()) ? i->second : 0; 474 } 475 476 inline ETNode *operator[](BasicBlock *BB) const { 477 return getNode(BB); 478 } 479 480 void reset(); 481 ETMapType Nodes; 482 bool DFSInfoValid; 483 unsigned int SlowQueries; 484 485}; 486 487//==------------------------------------- 488/// ETForest Class - Concrete subclass of ETForestBase that is used to 489/// compute a forwards ET-Forest. 490 491class ETForest : public ETForestBase { 492public: 493 static char ID; // Pass identification, replacement for typeid 494 495 ETForest() : ETForestBase((intptr_t)&ID, false) {} 496 497 BasicBlock *getRoot() const { 498 assert(Roots.size() == 1 && "Should always have entry node!"); 499 return Roots[0]; 500 } 501 502 virtual bool runOnFunction(Function &F) { 503 reset(); // Reset from the last time we were run... 504 DominatorTree &DT = getAnalysis<DominatorTree>(); 505 Roots = DT.getRoots(); 506 calculate(DT); 507 return false; 508 } 509 510 void calculate(const DominatorTree &DT); 511 // FIXME : There is no need to make getNodeForBlock public. Fix 512 // predicate simplifier. 513 ETNode *getNodeForBlock(BasicBlock *BB); 514}; 515 516//===----------------------------------------------------------------------===// 517/// DominanceFrontierBase - Common base class for computing forward and inverse 518/// dominance frontiers for a function. 519/// 520class DominanceFrontierBase : public DominatorBase { 521public: 522 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 523 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 524protected: 525 DomSetMapType Frontiers; 526public: 527 DominanceFrontierBase(intptr_t ID, bool isPostDom) 528 : DominatorBase(ID, isPostDom) {} 529 530 virtual void releaseMemory() { Frontiers.clear(); } 531 532 // Accessor interface: 533 typedef DomSetMapType::iterator iterator; 534 typedef DomSetMapType::const_iterator const_iterator; 535 iterator begin() { return Frontiers.begin(); } 536 const_iterator begin() const { return Frontiers.begin(); } 537 iterator end() { return Frontiers.end(); } 538 const_iterator end() const { return Frontiers.end(); } 539 iterator find(BasicBlock *B) { return Frontiers.find(B); } 540 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 541 542 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 543 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 544 Frontiers.insert(std::make_pair(BB, frontier)); 545 } 546 547 void addToFrontier(iterator I, BasicBlock *Node) { 548 assert(I != end() && "BB is not in DominanceFrontier!"); 549 I->second.insert(Node); 550 } 551 552 void removeFromFrontier(iterator I, BasicBlock *Node) { 553 assert(I != end() && "BB is not in DominanceFrontier!"); 554 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 555 I->second.erase(Node); 556 } 557 558 /// print - Convert to human readable form 559 /// 560 virtual void print(std::ostream &OS, const Module* = 0) const; 561 void print(std::ostream *OS, const Module* M = 0) const { 562 if (OS) print(*OS, M); 563 } 564 virtual void dump(); 565}; 566 567 568//===------------------------------------- 569/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 570/// used to compute a forward dominator frontiers. 571/// 572class DominanceFrontier : public DominanceFrontierBase { 573public: 574 static char ID; // Pass ID, replacement for typeid 575 DominanceFrontier() : 576 DominanceFrontierBase((intptr_t)& ID, false) {} 577 578 BasicBlock *getRoot() const { 579 assert(Roots.size() == 1 && "Should always have entry node!"); 580 return Roots[0]; 581 } 582 583 virtual bool runOnFunction(Function &) { 584 Frontiers.clear(); 585 DominatorTree &DT = getAnalysis<DominatorTree>(); 586 Roots = DT.getRoots(); 587 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 588 calculate(DT, DT[Roots[0]]); 589 return false; 590 } 591 592 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 593 AU.setPreservesAll(); 594 AU.addRequired<DominatorTree>(); 595 } 596 597private: 598 const DomSetType &calculate(const DominatorTree &DT, 599 const DomTreeNode *Node); 600}; 601 602 603} // End llvm namespace 604 605#endif 606