Dominators.h revision 4d42dea25397f2f822a93edfe9930b36ea85a7e7
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 std::vector<DomTreeNode*> Children; 67 int DFSNumIn, DFSNumOut; 68 69public: 70 typedef std::vector<DomTreeNode*>::iterator iterator; 71 typedef std::vector<DomTreeNode*>::const_iterator const_iterator; 72 73 iterator begin() { return Children.begin(); } 74 iterator end() { return Children.end(); } 75 const_iterator begin() const { return Children.begin(); } 76 const_iterator end() const { return Children.end(); } 77 78 inline BasicBlock *getBlock() const { return TheBB; } 79 inline DomTreeNode *getIDom() const { return IDom; } 80 inline const std::vector<DomTreeNode*> &getChildren() const { return Children; } 81 82 inline DomTreeNode(BasicBlock *BB, DomTreeNode *iDom) 83 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { } 84 inline DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; } 85 void setIDom(DomTreeNode *NewIDom); 86 87 // Return true if this node is dominated by other. Use this only if DFS info is valid. 88 bool DominatedBy(const DomTreeNode *other) const { 89 return this->DFSNumIn >= other->DFSNumIn && 90 this->DFSNumOut <= other->DFSNumOut; 91 } 92 93 /// assignDFSNumber - Assign In and Out numbers while walking dominator tree 94 /// in dfs order. 95 void assignDFSNumber(int num); 96}; 97 98//===----------------------------------------------------------------------===// 99/// DominatorTree - Calculate the immediate dominator tree for a function. 100/// 101class DominatorTreeBase : public DominatorBase { 102 103protected: 104 void reset(); 105 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 106 DomTreeNodeMapType DomTreeNodes; 107 DomTreeNode *RootNode; 108 109 bool DFSInfoValid; 110 unsigned int SlowQueries; 111 // Information record used during immediate dominators computation. 112 struct InfoRec { 113 unsigned Semi; 114 unsigned Size; 115 BasicBlock *Label, *Parent, *Child, *Ancestor; 116 117 std::vector<BasicBlock*> Bucket; 118 119 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 120 }; 121 122 std::map<BasicBlock*, BasicBlock*> IDoms; 123 124 // Vertex - Map the DFS number to the BasicBlock* 125 std::vector<BasicBlock*> Vertex; 126 127 // Info - Collection of information used during the computation of idoms. 128 std::map<BasicBlock*, InfoRec> Info; 129 130 public: 131 DominatorTreeBase(intptr_t ID, bool isPostDom) 132 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {} 133 ~DominatorTreeBase() { reset(); } 134 135 virtual void releaseMemory() { reset(); } 136 137 /// getNode - return the (Post)DominatorTree node for the specified basic 138 /// block. This is the same as using operator[] on this class. 139 /// 140 inline DomTreeNode *getNode(BasicBlock *BB) const { 141 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB); 142 return (i != DomTreeNodes.end()) ? i->second : 0; 143 } 144 145 inline DomTreeNode *operator[](BasicBlock *BB) const { 146 return getNode(BB); 147 } 148 149 /// getIDomBlock - return basic block BB's immediate dominator basic block. 150 /// 151 BasicBlock *getIDomBlock(BasicBlock *BB) { 152 DomTreeNode *N = getNode(BB); 153 assert (N && "Missing dominator tree node"); 154 DomTreeNode *I = N->getIDom(); 155 assert (N && "Missing immediate dominator"); 156 return I->getBlock(); 157 } 158 159 /// getRootNode - This returns the entry node for the CFG of the function. If 160 /// this tree represents the post-dominance relations for a function, however, 161 /// this root may be a node with the block == NULL. This is the case when 162 /// there are multiple exit nodes from a particular function. Consumers of 163 /// post-dominance information must be capable of dealing with this 164 /// possibility. 165 /// 166 DomTreeNode *getRootNode() { return RootNode; } 167 const DomTreeNode *getRootNode() const { return RootNode; } 168 169 /// properlyDominates - Returns true iff this dominates N and this != N. 170 /// Note that this is not a constant time operation! 171 /// 172 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const { 173 if (A == 0 || B == 0) return false; 174 return dominatedBySlowTreeWalk(A, B); 175 } 176 177 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) { 178 return properlyDominates(getNode(A), getNode(B)); 179 } 180 181 bool dominatedBySlowTreeWalk(const DomTreeNode *A, 182 const DomTreeNode *B) const { 183 const DomTreeNode *IDom; 184 if (A == 0 || B == 0) return false; 185 while ((IDom = B->getIDom()) != 0 && IDom != A) 186 B = IDom; // Walk up the tree 187 return IDom != 0; 188 } 189 190 void updateDFSNumbers(); 191 192 /// isReachableFromEntry - Return true if A is dominated by the entry 193 /// block of the function containing it. 194 const bool isReachableFromEntry(BasicBlock* A); 195 196 /// dominates - Returns true iff this dominates N. Note that this is not a 197 /// constant time operation! 198 /// 199 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) { 200 if (B == A) 201 return true; // A node trivially dominates itself. 202 203 if (A == 0 || B == 0) 204 return false; 205 206 if (DFSInfoValid) 207 return B->DominatedBy(A); 208 209 // If we end up with too many slow queries, just update the 210 // DFS numbers on the theory that we are going to keep querying. 211 SlowQueries++; 212 if (SlowQueries > 32) { 213 updateDFSNumbers(); 214 return B->DominatedBy(A); 215 } 216 217 return dominatedBySlowTreeWalk(A, B); 218 } 219 220 inline bool dominates(BasicBlock *A, BasicBlock *B) { 221 if (A == B) 222 return true; 223 224 return dominates(getNode(A), getNode(B)); 225 } 226 227 /// findNearestCommonDominator - Find nearest common dominator basic block 228 /// for basic block A and B. If there is no such block then return NULL. 229 BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B); 230 231 // dominates - Return true if A dominates B. This performs the 232 // special checks necessary if A and B are in the same basic block. 233 bool dominates(Instruction *A, Instruction *B); 234 235 //===--------------------------------------------------------------------===// 236 // API to update (Post)DominatorTree information based on modifications to 237 // the CFG... 238 239 /// addNewBlock - Add a new node to the dominator tree information. This 240 /// creates a new node as a child of DomBB dominator node,linking it into 241 /// the children list of the immediate dominator. 242 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 243 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 244 DomTreeNode *IDomNode = getNode(DomBB); 245 assert(IDomNode && "Not immediate dominator specified for block!"); 246 DFSInfoValid = false; 247 return DomTreeNodes[BB] = 248 IDomNode->addChild(new DomTreeNode(BB, IDomNode)); 249 } 250 251 /// changeImmediateDominator - This method is used to update the dominator 252 /// tree information when a node's immediate dominator changes. 253 /// 254 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 255 assert(N && NewIDom && "Cannot change null node pointers!"); 256 DFSInfoValid = false; 257 N->setIDom(NewIDom); 258 } 259 260 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) { 261 changeImmediateDominator(getNode(BB), getNode(NewBB)); 262 } 263 264 /// removeNode - Removes a node from the dominator tree. Block must not 265 /// dominate any other blocks. Invalidates any node pointing to removed 266 /// block. 267 void removeNode(BasicBlock *BB) { 268 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 269 DomTreeNodes.erase(BB); 270 } 271 272 /// print - Convert to human readable form 273 /// 274 virtual void print(std::ostream &OS, const Module* = 0) const; 275 void print(std::ostream *OS, const Module* M = 0) const { 276 if (OS) print(*OS, M); 277 } 278 virtual void dump(); 279}; 280 281//===------------------------------------- 282/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 283/// compute a normal dominator tree. 284/// 285class DominatorTree : public DominatorTreeBase { 286public: 287 static char ID; // Pass ID, replacement for typeid 288 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 289 290 BasicBlock *getRoot() const { 291 assert(Roots.size() == 1 && "Should always have entry node!"); 292 return Roots[0]; 293 } 294 295 virtual bool runOnFunction(Function &F); 296 297 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 298 AU.setPreservesAll(); 299 } 300private: 301 void calculate(Function& F); 302 DomTreeNode *getNodeForBlock(BasicBlock *BB); 303 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 304 void Compress(BasicBlock *V); 305 BasicBlock *Eval(BasicBlock *v); 306 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 307 inline BasicBlock *getIDom(BasicBlock *BB) const { 308 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 309 return I != IDoms.end() ? I->second : 0; 310 } 311}; 312 313//===------------------------------------- 314/// DominatorTree GraphTraits specialization so the DominatorTree can be 315/// iterable by generic graph iterators. 316/// 317template <> struct GraphTraits<DomTreeNode*> { 318 typedef DomTreeNode NodeType; 319 typedef NodeType::iterator ChildIteratorType; 320 321 static NodeType *getEntryNode(NodeType *N) { 322 return N; 323 } 324 static inline ChildIteratorType child_begin(NodeType* N) { 325 return N->begin(); 326 } 327 static inline ChildIteratorType child_end(NodeType* N) { 328 return N->end(); 329 } 330}; 331 332template <> struct GraphTraits<DominatorTree*> 333 : public GraphTraits<DomTreeNode*> { 334 static NodeType *getEntryNode(DominatorTree *DT) { 335 return DT->getRootNode(); 336 } 337}; 338 339 340//===------------------------------------- 341/// ET-Forest Class - Class used to construct forwards and backwards 342/// ET-Forests 343/// 344class ETForestBase : public DominatorBase { 345public: 346 ETForestBase(intptr_t ID, bool isPostDom) 347 : DominatorBase(ID, isPostDom), Nodes(), 348 DFSInfoValid(false), SlowQueries(0) {} 349 350 virtual void releaseMemory() { reset(); } 351 352 typedef std::map<BasicBlock*, ETNode*> ETMapType; 353 354 // FIXME : There is no need to make this interface public. 355 // Fix predicate simplifier. 356 void updateDFSNumbers(); 357 358 /// dominates - Return true if A dominates B. 359 /// 360 inline bool dominates(BasicBlock *A, BasicBlock *B) { 361 if (A == B) 362 return true; 363 364 ETNode *NodeA = getNode(A); 365 ETNode *NodeB = getNode(B); 366 367 if (DFSInfoValid) 368 return NodeB->DominatedBy(NodeA); 369 else { 370 // If we end up with too many slow queries, just update the 371 // DFS numbers on the theory that we are going to keep querying. 372 SlowQueries++; 373 if (SlowQueries > 32) { 374 updateDFSNumbers(); 375 return NodeB->DominatedBy(NodeA); 376 } 377 return NodeB->DominatedBySlow(NodeA); 378 } 379 } 380 381 // dominates - Return true if A dominates B. This performs the 382 // special checks necessary if A and B are in the same basic block. 383 bool dominates(Instruction *A, Instruction *B); 384 385 /// properlyDominates - Return true if A dominates B and A != B. 386 /// 387 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 388 return dominates(A, B) && A != B; 389 } 390 391 /// isReachableFromEntry - Return true if A is dominated by the entry 392 /// block of the function containing it. 393 const bool isReachableFromEntry(BasicBlock* A); 394 395 /// Return the nearest common dominator of A and B. 396 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 397 ETNode *NodeA = getNode(A); 398 ETNode *NodeB = getNode(B); 399 400 ETNode *Common = NodeA->NCA(NodeB); 401 if (!Common) 402 return NULL; 403 return Common->getData<BasicBlock>(); 404 } 405 406 /// Return the immediate dominator of A. 407 BasicBlock *getIDom(BasicBlock *A) const { 408 ETNode *NodeA = getNode(A); 409 if (!NodeA) return 0; 410 const ETNode *idom = NodeA->getFather(); 411 return idom ? idom->getData<BasicBlock>() : 0; 412 } 413 414 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const { 415 ETNode *NodeA = getNode(A); 416 if (!NodeA) return; 417 const ETNode* son = NodeA->getSon(); 418 419 if (!son) return; 420 children.push_back(son->getData<BasicBlock>()); 421 422 const ETNode* brother = son->getBrother(); 423 while (brother != son) { 424 children.push_back(brother->getData<BasicBlock>()); 425 brother = brother->getBrother(); 426 } 427 } 428 429 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 430 AU.setPreservesAll(); 431 AU.addRequired<DominatorTree>(); 432 } 433 //===--------------------------------------------------------------------===// 434 // API to update Forest information based on modifications 435 // to the CFG... 436 437 /// addNewBlock - Add a new block to the CFG, with the specified immediate 438 /// dominator. 439 /// 440 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 441 442 /// setImmediateDominator - Update the immediate dominator information to 443 /// change the current immediate dominator for the specified block 444 /// to another block. This method requires that BB for NewIDom 445 /// already have an ETNode, otherwise just use addNewBlock. 446 /// 447 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 448 /// print - Convert to human readable form 449 /// 450 virtual void print(std::ostream &OS, const Module* = 0) const; 451 void print(std::ostream *OS, const Module* M = 0) const { 452 if (OS) print(*OS, M); 453 } 454 virtual void dump(); 455protected: 456 /// getNode - return the (Post)DominatorTree node for the specified basic 457 /// block. This is the same as using operator[] on this class. 458 /// 459 inline ETNode *getNode(BasicBlock *BB) const { 460 ETMapType::const_iterator i = Nodes.find(BB); 461 return (i != Nodes.end()) ? i->second : 0; 462 } 463 464 inline ETNode *operator[](BasicBlock *BB) const { 465 return getNode(BB); 466 } 467 468 void reset(); 469 ETMapType Nodes; 470 bool DFSInfoValid; 471 unsigned int SlowQueries; 472 473}; 474 475//==------------------------------------- 476/// ETForest Class - Concrete subclass of ETForestBase that is used to 477/// compute a forwards ET-Forest. 478 479class ETForest : public ETForestBase { 480public: 481 static char ID; // Pass identification, replacement for typeid 482 483 ETForest() : ETForestBase((intptr_t)&ID, false) {} 484 485 BasicBlock *getRoot() const { 486 assert(Roots.size() == 1 && "Should always have entry node!"); 487 return Roots[0]; 488 } 489 490 virtual bool runOnFunction(Function &F) { 491 reset(); // Reset from the last time we were run... 492 DominatorTree &DT = getAnalysis<DominatorTree>(); 493 Roots = DT.getRoots(); 494 calculate(DT); 495 return false; 496 } 497 498 void calculate(const DominatorTree &DT); 499 // FIXME : There is no need to make getNodeForBlock public. Fix 500 // predicate simplifier. 501 ETNode *getNodeForBlock(BasicBlock *BB); 502}; 503 504//===----------------------------------------------------------------------===// 505/// DominanceFrontierBase - Common base class for computing forward and inverse 506/// dominance frontiers for a function. 507/// 508class DominanceFrontierBase : public DominatorBase { 509public: 510 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 511 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 512protected: 513 DomSetMapType Frontiers; 514public: 515 DominanceFrontierBase(intptr_t ID, bool isPostDom) 516 : DominatorBase(ID, isPostDom) {} 517 518 virtual void releaseMemory() { Frontiers.clear(); } 519 520 // Accessor interface: 521 typedef DomSetMapType::iterator iterator; 522 typedef DomSetMapType::const_iterator const_iterator; 523 iterator begin() { return Frontiers.begin(); } 524 const_iterator begin() const { return Frontiers.begin(); } 525 iterator end() { return Frontiers.end(); } 526 const_iterator end() const { return Frontiers.end(); } 527 iterator find(BasicBlock *B) { return Frontiers.find(B); } 528 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 529 530 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 531 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 532 Frontiers.insert(std::make_pair(BB, frontier)); 533 } 534 535 void addToFrontier(iterator I, BasicBlock *Node) { 536 assert(I != end() && "BB is not in DominanceFrontier!"); 537 I->second.insert(Node); 538 } 539 540 void removeFromFrontier(iterator I, BasicBlock *Node) { 541 assert(I != end() && "BB is not in DominanceFrontier!"); 542 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 543 I->second.erase(Node); 544 } 545 546 /// print - Convert to human readable form 547 /// 548 virtual void print(std::ostream &OS, const Module* = 0) const; 549 void print(std::ostream *OS, const Module* M = 0) const { 550 if (OS) print(*OS, M); 551 } 552 virtual void dump(); 553}; 554 555 556//===------------------------------------- 557/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 558/// used to compute a forward dominator frontiers. 559/// 560class DominanceFrontier : public DominanceFrontierBase { 561public: 562 static char ID; // Pass ID, replacement for typeid 563 DominanceFrontier() : 564 DominanceFrontierBase((intptr_t)& ID, false) {} 565 566 BasicBlock *getRoot() const { 567 assert(Roots.size() == 1 && "Should always have entry node!"); 568 return Roots[0]; 569 } 570 571 virtual bool runOnFunction(Function &) { 572 Frontiers.clear(); 573 DominatorTree &DT = getAnalysis<DominatorTree>(); 574 Roots = DT.getRoots(); 575 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 576 calculate(DT, DT[Roots[0]]); 577 return false; 578 } 579 580 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 581 AU.setPreservesAll(); 582 AU.addRequired<DominatorTree>(); 583 } 584 585private: 586 const DomSetType &calculate(const DominatorTree &DT, 587 const DomTreeNode *Node); 588}; 589 590 591} // End llvm namespace 592 593#endif 594