Dominators.h revision 0e7f728ad1ac25b0ed450fe0f8b86a38d3c2a93a
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 62class DominatorTreeBase; 63class PostDominatorTree; 64class DomTreeNode { 65 BasicBlock *TheBB; 66 DomTreeNode *IDom; 67 std::vector<DomTreeNode*> Children; 68 int DFSNumIn, DFSNumOut; 69 70 friend class DominatorTreeBase; 71 friend class PostDominatorTree; 72public: 73 typedef std::vector<DomTreeNode*>::iterator iterator; 74 typedef std::vector<DomTreeNode*>::const_iterator const_iterator; 75 76 iterator begin() { return Children.begin(); } 77 iterator end() { return Children.end(); } 78 const_iterator begin() const { return Children.begin(); } 79 const_iterator end() const { return Children.end(); } 80 81 inline BasicBlock *getBlock() const { return TheBB; } 82 inline DomTreeNode *getIDom() const { return IDom; } 83 inline const std::vector<DomTreeNode*> &getChildren() const { return Children; } 84 85 inline DomTreeNode(BasicBlock *BB, DomTreeNode *iDom) 86 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { } 87 inline DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; } 88 void setIDom(DomTreeNode *NewIDom); 89 90private: 91 // Return true if this node is dominated by other. Use this only if DFS info is valid. 92 bool DominatedBy(const DomTreeNode *other) const { 93 return this->DFSNumIn >= other->DFSNumIn && 94 this->DFSNumOut <= other->DFSNumOut; 95 } 96 97 /// assignDFSNumber - Assign In and Out numbers while walking dominator tree 98 /// in dfs order. 99 void assignDFSNumber(int num); 100}; 101 102//===----------------------------------------------------------------------===// 103/// DominatorTree - Calculate the immediate dominator tree for a function. 104/// 105class DominatorTreeBase : public DominatorBase { 106 107protected: 108 void reset(); 109 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 110 DomTreeNodeMapType DomTreeNodes; 111 DomTreeNode *RootNode; 112 113 bool DFSInfoValid; 114 unsigned int SlowQueries; 115 // Information record used during immediate dominators computation. 116 struct InfoRec { 117 unsigned Semi; 118 unsigned Size; 119 BasicBlock *Label, *Parent, *Child, *Ancestor; 120 121 std::vector<BasicBlock*> Bucket; 122 123 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 124 }; 125 126 std::map<BasicBlock*, BasicBlock*> IDoms; 127 128 // Vertex - Map the DFS number to the BasicBlock* 129 std::vector<BasicBlock*> Vertex; 130 131 // Info - Collection of information used during the computation of idoms. 132 std::map<BasicBlock*, InfoRec> Info; 133 134 void updateDFSNumbers(); 135 136 public: 137 DominatorTreeBase(intptr_t ID, bool isPostDom) 138 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {} 139 ~DominatorTreeBase() { reset(); } 140 141 virtual void releaseMemory() { reset(); } 142 143 /// getNode - return the (Post)DominatorTree node for the specified basic 144 /// block. This is the same as using operator[] on this class. 145 /// 146 inline DomTreeNode *getNode(BasicBlock *BB) const { 147 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB); 148 return (i != DomTreeNodes.end()) ? i->second : 0; 149 } 150 151 inline DomTreeNode *operator[](BasicBlock *BB) const { 152 return getNode(BB); 153 } 154 155 /// getIDomBlock - return basic block BB's immediate dominator basic block. 156 /// 157 BasicBlock *getIDomBlock(BasicBlock *BB) { 158 DomTreeNode *N = getNode(BB); 159 assert (N && "Missing dominator tree node"); 160 DomTreeNode *I = N->getIDom(); 161 assert (N && "Missing immediate dominator"); 162 return I->getBlock(); 163 } 164 165 /// getRootNode - This returns the entry node for the CFG of the function. If 166 /// this tree represents the post-dominance relations for a function, however, 167 /// this root may be a node with the block == NULL. This is the case when 168 /// there are multiple exit nodes from a particular function. Consumers of 169 /// post-dominance information must be capable of dealing with this 170 /// possibility. 171 /// 172 DomTreeNode *getRootNode() { return RootNode; } 173 const DomTreeNode *getRootNode() const { return RootNode; } 174 175 /// properlyDominates - Returns true iff this dominates N and this != N. 176 /// Note that this is not a constant time operation! 177 /// 178 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const { 179 if (A == 0 || B == 0) return false; 180 return dominatedBySlowTreeWalk(A, B); 181 } 182 183 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) { 184 return properlyDominates(getNode(A), getNode(B)); 185 } 186 187 bool dominatedBySlowTreeWalk(const DomTreeNode *A, 188 const DomTreeNode *B) const { 189 const DomTreeNode *IDom; 190 if (A == 0 || B == 0) return false; 191 while ((IDom = B->getIDom()) != 0 && IDom != A) 192 B = IDom; // Walk up the tree 193 return IDom != 0; 194 } 195 196 197 /// isReachableFromEntry - Return true if A is dominated by the entry 198 /// block of the function containing it. 199 const bool isReachableFromEntry(BasicBlock* A); 200 201 /// dominates - Returns true iff A dominates B. Note that this is not a 202 /// constant time operation! 203 /// 204 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) { 205 if (B == A) 206 return true; // A node trivially dominates itself. 207 208 if (A == 0 || B == 0) 209 return false; 210 211 if (DFSInfoValid) 212 return B->DominatedBy(A); 213 214 // If we end up with too many slow queries, just update the 215 // DFS numbers on the theory that we are going to keep querying. 216 SlowQueries++; 217 if (SlowQueries > 32) { 218 updateDFSNumbers(); 219 return B->DominatedBy(A); 220 } 221 222 return dominatedBySlowTreeWalk(A, B); 223 } 224 225 inline bool dominates(BasicBlock *A, BasicBlock *B) { 226 if (A == B) 227 return true; 228 229 return dominates(getNode(A), getNode(B)); 230 } 231 232 /// findNearestCommonDominator - Find nearest common dominator basic block 233 /// for basic block A and B. If there is no such block then return NULL. 234 BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B); 235 236 // dominates - Return true if A dominates B. This performs the 237 // special checks necessary if A and B are in the same basic block. 238 bool dominates(Instruction *A, Instruction *B); 239 240 //===--------------------------------------------------------------------===// 241 // API to update (Post)DominatorTree information based on modifications to 242 // the CFG... 243 244 /// addNewBlock - Add a new node to the dominator tree information. This 245 /// creates a new node as a child of DomBB dominator node,linking it into 246 /// the children list of the immediate dominator. 247 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 248 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 249 DomTreeNode *IDomNode = getNode(DomBB); 250 assert(IDomNode && "Not immediate dominator specified for block!"); 251 DFSInfoValid = false; 252 return DomTreeNodes[BB] = 253 IDomNode->addChild(new DomTreeNode(BB, IDomNode)); 254 } 255 256 /// changeImmediateDominator - This method is used to update the dominator 257 /// tree information when a node's immediate dominator changes. 258 /// 259 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 260 assert(N && NewIDom && "Cannot change null node pointers!"); 261 DFSInfoValid = false; 262 N->setIDom(NewIDom); 263 } 264 265 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) { 266 changeImmediateDominator(getNode(BB), getNode(NewBB)); 267 } 268 269 /// removeNode - Removes a node from the dominator tree. Block must not 270 /// dominate any other blocks. Invalidates any node pointing to removed 271 /// block. 272 void removeNode(BasicBlock *BB) { 273 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 274 DomTreeNodes.erase(BB); 275 } 276 277 /// print - Convert to human readable form 278 /// 279 virtual void print(std::ostream &OS, const Module* = 0) const; 280 void print(std::ostream *OS, const Module* M = 0) const { 281 if (OS) print(*OS, M); 282 } 283 virtual void dump(); 284}; 285 286//===------------------------------------- 287/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 288/// compute a normal dominator tree. 289/// 290class DominatorTree : public DominatorTreeBase { 291public: 292 static char ID; // Pass ID, replacement for typeid 293 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 294 295 BasicBlock *getRoot() const { 296 assert(Roots.size() == 1 && "Should always have entry node!"); 297 return Roots[0]; 298 } 299 300 virtual bool runOnFunction(Function &F); 301 302 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 303 AU.setPreservesAll(); 304 } 305 306 /// splitBlock 307 /// BB is split and now it has one successor. Update dominator tree to 308 /// reflect this change. 309 void splitBlock(BasicBlock *BB); 310private: 311 void calculate(Function& F); 312 DomTreeNode *getNodeForBlock(BasicBlock *BB); 313 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 314 void Compress(BasicBlock *V); 315 BasicBlock *Eval(BasicBlock *v); 316 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 317 inline BasicBlock *getIDom(BasicBlock *BB) const { 318 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 319 return I != IDoms.end() ? I->second : 0; 320 } 321}; 322 323//===------------------------------------- 324/// DominatorTree GraphTraits specialization so the DominatorTree can be 325/// iterable by generic graph iterators. 326/// 327template <> struct GraphTraits<DomTreeNode*> { 328 typedef DomTreeNode NodeType; 329 typedef NodeType::iterator ChildIteratorType; 330 331 static NodeType *getEntryNode(NodeType *N) { 332 return N; 333 } 334 static inline ChildIteratorType child_begin(NodeType* N) { 335 return N->begin(); 336 } 337 static inline ChildIteratorType child_end(NodeType* N) { 338 return N->end(); 339 } 340}; 341 342template <> struct GraphTraits<DominatorTree*> 343 : public GraphTraits<DomTreeNode*> { 344 static NodeType *getEntryNode(DominatorTree *DT) { 345 return DT->getRootNode(); 346 } 347}; 348 349 350//===------------------------------------- 351/// ET-Forest Class - Class used to construct forwards and backwards 352/// ET-Forests 353/// 354class ETForestBase : public DominatorBase { 355public: 356 ETForestBase(intptr_t ID, bool isPostDom) 357 : DominatorBase(ID, isPostDom), Nodes(), 358 DFSInfoValid(false), SlowQueries(0) {} 359 360 virtual void releaseMemory() { reset(); } 361 362 typedef std::map<BasicBlock*, ETNode*> ETMapType; 363 364 // FIXME : There is no need to make this interface public. 365 // Fix predicate simplifier. 366 void updateDFSNumbers(); 367 368 /// dominates - Return true if A dominates B. 369 /// 370 inline bool dominates(BasicBlock *A, BasicBlock *B) { 371 if (A == B) 372 return true; 373 374 ETNode *NodeA = getNode(A); 375 ETNode *NodeB = getNode(B); 376 377 if (DFSInfoValid) 378 return NodeB->DominatedBy(NodeA); 379 else { 380 // If we end up with too many slow queries, just update the 381 // DFS numbers on the theory that we are going to keep querying. 382 SlowQueries++; 383 if (SlowQueries > 32) { 384 updateDFSNumbers(); 385 return NodeB->DominatedBy(NodeA); 386 } 387 return NodeB->DominatedBySlow(NodeA); 388 } 389 } 390 391 // dominates - Return true if A dominates B. This performs the 392 // special checks necessary if A and B are in the same basic block. 393 bool dominates(Instruction *A, Instruction *B); 394 395 /// properlyDominates - Return true if A dominates B and A != B. 396 /// 397 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 398 return dominates(A, B) && A != B; 399 } 400 401 /// isReachableFromEntry - Return true if A is dominated by the entry 402 /// block of the function containing it. 403 const bool isReachableFromEntry(BasicBlock* A); 404 405 /// Return the nearest common dominator of A and B. 406 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 407 ETNode *NodeA = getNode(A); 408 ETNode *NodeB = getNode(B); 409 410 ETNode *Common = NodeA->NCA(NodeB); 411 if (!Common) 412 return NULL; 413 return Common->getData<BasicBlock>(); 414 } 415 416 /// Return the immediate dominator of A. 417 BasicBlock *getIDom(BasicBlock *A) const { 418 ETNode *NodeA = getNode(A); 419 if (!NodeA) return 0; 420 const ETNode *idom = NodeA->getFather(); 421 return idom ? idom->getData<BasicBlock>() : 0; 422 } 423 424 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const { 425 ETNode *NodeA = getNode(A); 426 if (!NodeA) return; 427 const ETNode* son = NodeA->getSon(); 428 429 if (!son) return; 430 children.push_back(son->getData<BasicBlock>()); 431 432 const ETNode* brother = son->getBrother(); 433 while (brother != son) { 434 children.push_back(brother->getData<BasicBlock>()); 435 brother = brother->getBrother(); 436 } 437 } 438 439 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 440 AU.setPreservesAll(); 441 AU.addRequired<DominatorTree>(); 442 } 443 //===--------------------------------------------------------------------===// 444 // API to update Forest information based on modifications 445 // to the CFG... 446 447 /// addNewBlock - Add a new block to the CFG, with the specified immediate 448 /// dominator. 449 /// 450 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 451 452 /// setImmediateDominator - Update the immediate dominator information to 453 /// change the current immediate dominator for the specified block 454 /// to another block. This method requires that BB for NewIDom 455 /// already have an ETNode, otherwise just use addNewBlock. 456 /// 457 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 458 /// print - Convert to human readable form 459 /// 460 virtual void print(std::ostream &OS, const Module* = 0) const; 461 void print(std::ostream *OS, const Module* M = 0) const { 462 if (OS) print(*OS, M); 463 } 464 virtual void dump(); 465protected: 466 /// getNode - return the (Post)DominatorTree node for the specified basic 467 /// block. This is the same as using operator[] on this class. 468 /// 469 inline ETNode *getNode(BasicBlock *BB) const { 470 ETMapType::const_iterator i = Nodes.find(BB); 471 return (i != Nodes.end()) ? i->second : 0; 472 } 473 474 inline ETNode *operator[](BasicBlock *BB) const { 475 return getNode(BB); 476 } 477 478 void reset(); 479 ETMapType Nodes; 480 bool DFSInfoValid; 481 unsigned int SlowQueries; 482 483}; 484 485//==------------------------------------- 486/// ETForest Class - Concrete subclass of ETForestBase that is used to 487/// compute a forwards ET-Forest. 488 489class ETForest : public ETForestBase { 490public: 491 static char ID; // Pass identification, replacement for typeid 492 493 ETForest() : ETForestBase((intptr_t)&ID, false) {} 494 495 BasicBlock *getRoot() const { 496 assert(Roots.size() == 1 && "Should always have entry node!"); 497 return Roots[0]; 498 } 499 500 virtual bool runOnFunction(Function &F) { 501 reset(); // Reset from the last time we were run... 502 DominatorTree &DT = getAnalysis<DominatorTree>(); 503 Roots = DT.getRoots(); 504 calculate(DT); 505 return false; 506 } 507 508 void calculate(const DominatorTree &DT); 509 // FIXME : There is no need to make getNodeForBlock public. Fix 510 // predicate simplifier. 511 ETNode *getNodeForBlock(BasicBlock *BB); 512}; 513 514//===----------------------------------------------------------------------===// 515/// DominanceFrontierBase - Common base class for computing forward and inverse 516/// dominance frontiers for a function. 517/// 518class DominanceFrontierBase : public DominatorBase { 519public: 520 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 521 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 522protected: 523 DomSetMapType Frontiers; 524public: 525 DominanceFrontierBase(intptr_t ID, bool isPostDom) 526 : DominatorBase(ID, isPostDom) {} 527 528 virtual void releaseMemory() { Frontiers.clear(); } 529 530 // Accessor interface: 531 typedef DomSetMapType::iterator iterator; 532 typedef DomSetMapType::const_iterator const_iterator; 533 iterator begin() { return Frontiers.begin(); } 534 const_iterator begin() const { return Frontiers.begin(); } 535 iterator end() { return Frontiers.end(); } 536 const_iterator end() const { return Frontiers.end(); } 537 iterator find(BasicBlock *B) { return Frontiers.find(B); } 538 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 539 540 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 541 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 542 Frontiers.insert(std::make_pair(BB, frontier)); 543 } 544 545 void addToFrontier(iterator I, BasicBlock *Node) { 546 assert(I != end() && "BB is not in DominanceFrontier!"); 547 I->second.insert(Node); 548 } 549 550 void removeFromFrontier(iterator I, BasicBlock *Node) { 551 assert(I != end() && "BB is not in DominanceFrontier!"); 552 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 553 I->second.erase(Node); 554 } 555 556 /// print - Convert to human readable form 557 /// 558 virtual void print(std::ostream &OS, const Module* = 0) const; 559 void print(std::ostream *OS, const Module* M = 0) const { 560 if (OS) print(*OS, M); 561 } 562 virtual void dump(); 563}; 564 565 566//===------------------------------------- 567/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 568/// used to compute a forward dominator frontiers. 569/// 570class DominanceFrontier : public DominanceFrontierBase { 571public: 572 static char ID; // Pass ID, replacement for typeid 573 DominanceFrontier() : 574 DominanceFrontierBase((intptr_t)& ID, false) {} 575 576 BasicBlock *getRoot() const { 577 assert(Roots.size() == 1 && "Should always have entry node!"); 578 return Roots[0]; 579 } 580 581 virtual bool runOnFunction(Function &) { 582 Frontiers.clear(); 583 DominatorTree &DT = getAnalysis<DominatorTree>(); 584 Roots = DT.getRoots(); 585 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 586 calculate(DT, DT[Roots[0]]); 587 return false; 588 } 589 590 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 591 AU.setPreservesAll(); 592 AU.addRequired<DominatorTree>(); 593 } 594 595 /// splitBlock 596 /// BB is split and now it has one successor. Update dominace frontier to 597 /// reflect this change. 598 void splitBlock(BasicBlock *BB); 599 600private: 601 const DomSetType &calculate(const DominatorTree &DT, 602 const DomTreeNode *Node); 603}; 604 605 606} // End llvm namespace 607 608#endif 609