Dominators.h revision dba2413b2ecf4e781f457036a2eb0f103192e90d
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 domiantor 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 // dominates - Return true if A dominates B. This performs the 238 // special checks necessary if A and B are in the same basic block. 239 bool dominates(Instruction *A, Instruction *B); 240 241 //===--------------------------------------------------------------------===// 242 // API to update (Post)DominatorTree information based on modifications to 243 // the CFG... 244 245 /// addNewBlock - Add a new node to the dominator tree information. This 246 /// creates a new node as a child of DomBB dominator node,linking it into 247 /// the children list of the immediate dominator. 248 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 249 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 250 DomTreeNode *IDomNode = getNode(DomBB); 251 assert(IDomNode && "Not immediate dominator specified for block!"); 252 DFSInfoValid = false; 253 ETNode *E = new ETNode(BB); 254 ETNodes[BB] = E; 255 return DomTreeNodes[BB] = 256 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E)); 257 } 258 259 /// changeImmediateDominator - This method is used to update the dominator 260 /// tree information when a node's immediate dominator changes. 261 /// 262 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 263 assert(N && NewIDom && "Cannot change null node pointers!"); 264 DFSInfoValid = false; 265 N->setIDom(NewIDom); 266 } 267 268 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) { 269 changeImmediateDominator(getNode(BB), getNode(NewBB)); 270 } 271 272 /// removeNode - Removes a node from the dominator tree. Block must not 273 /// dominate any other blocks. Invalidates any node pointing to removed 274 /// block. 275 void removeNode(BasicBlock *BB) { 276 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 277 DomTreeNodes.erase(BB); 278 } 279 280 /// print - Convert to human readable form 281 /// 282 virtual void print(std::ostream &OS, const Module* = 0) const; 283 void print(std::ostream *OS, const Module* M = 0) const { 284 if (OS) print(*OS, M); 285 } 286 virtual void dump(); 287}; 288 289//===------------------------------------- 290/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 291/// compute a normal dominator tree. 292/// 293class DominatorTree : public DominatorTreeBase { 294public: 295 static char ID; // Pass ID, replacement for typeid 296 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 297 298 BasicBlock *getRoot() const { 299 assert(Roots.size() == 1 && "Should always have entry node!"); 300 return Roots[0]; 301 } 302 303 virtual bool runOnFunction(Function &F); 304 305 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 306 AU.setPreservesAll(); 307 } 308private: 309 void calculate(Function& F); 310 DomTreeNode *getNodeForBlock(BasicBlock *BB); 311 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 312 void Compress(BasicBlock *V); 313 BasicBlock *Eval(BasicBlock *v); 314 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 315 inline BasicBlock *getIDom(BasicBlock *BB) const { 316 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 317 return I != IDoms.end() ? I->second : 0; 318 } 319}; 320 321//===------------------------------------- 322/// DominatorTree GraphTraits specialization so the DominatorTree can be 323/// iterable by generic graph iterators. 324/// 325template <> struct GraphTraits<DomTreeNode*> { 326 typedef DomTreeNode NodeType; 327 typedef NodeType::iterator ChildIteratorType; 328 329 static NodeType *getEntryNode(NodeType *N) { 330 return N; 331 } 332 static inline ChildIteratorType child_begin(NodeType* N) { 333 return N->begin(); 334 } 335 static inline ChildIteratorType child_end(NodeType* N) { 336 return N->end(); 337 } 338}; 339 340template <> struct GraphTraits<DominatorTree*> 341 : public GraphTraits<DomTreeNode*> { 342 static NodeType *getEntryNode(DominatorTree *DT) { 343 return DT->getRootNode(); 344 } 345}; 346 347 348//===------------------------------------- 349/// ET-Forest Class - Class used to construct forwards and backwards 350/// ET-Forests 351/// 352class ETForestBase : public DominatorBase { 353public: 354 ETForestBase(intptr_t ID, bool isPostDom) 355 : DominatorBase(ID, isPostDom), Nodes(), 356 DFSInfoValid(false), SlowQueries(0) {} 357 358 virtual void releaseMemory() { reset(); } 359 360 typedef std::map<BasicBlock*, ETNode*> ETMapType; 361 362 // FIXME : There is no need to make this interface public. 363 // Fix predicate simplifier. 364 void updateDFSNumbers(); 365 366 /// dominates - Return true if A dominates B. 367 /// 368 inline bool dominates(BasicBlock *A, BasicBlock *B) { 369 if (A == B) 370 return true; 371 372 ETNode *NodeA = getNode(A); 373 ETNode *NodeB = getNode(B); 374 375 if (DFSInfoValid) 376 return NodeB->DominatedBy(NodeA); 377 else { 378 // If we end up with too many slow queries, just update the 379 // DFS numbers on the theory that we are going to keep querying. 380 SlowQueries++; 381 if (SlowQueries > 32) { 382 updateDFSNumbers(); 383 return NodeB->DominatedBy(NodeA); 384 } 385 return NodeB->DominatedBySlow(NodeA); 386 } 387 } 388 389 // dominates - Return true if A dominates B. This performs the 390 // special checks necessary if A and B are in the same basic block. 391 bool dominates(Instruction *A, Instruction *B); 392 393 /// properlyDominates - Return true if A dominates B and A != B. 394 /// 395 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 396 return dominates(A, B) && A != B; 397 } 398 399 /// isReachableFromEntry - Return true if A is dominated by the entry 400 /// block of the function containing it. 401 const bool isReachableFromEntry(BasicBlock* A); 402 403 /// Return the nearest common dominator of A and B. 404 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 405 ETNode *NodeA = getNode(A); 406 ETNode *NodeB = getNode(B); 407 408 ETNode *Common = NodeA->NCA(NodeB); 409 if (!Common) 410 return NULL; 411 return Common->getData<BasicBlock>(); 412 } 413 414 /// Return the immediate dominator of A. 415 BasicBlock *getIDom(BasicBlock *A) const { 416 ETNode *NodeA = getNode(A); 417 if (!NodeA) return 0; 418 const ETNode *idom = NodeA->getFather(); 419 return idom ? idom->getData<BasicBlock>() : 0; 420 } 421 422 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const { 423 ETNode *NodeA = getNode(A); 424 if (!NodeA) return; 425 const ETNode* son = NodeA->getSon(); 426 427 if (!son) return; 428 children.push_back(son->getData<BasicBlock>()); 429 430 const ETNode* brother = son->getBrother(); 431 while (brother != son) { 432 children.push_back(brother->getData<BasicBlock>()); 433 brother = brother->getBrother(); 434 } 435 } 436 437 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 438 AU.setPreservesAll(); 439 AU.addRequired<DominatorTree>(); 440 } 441 //===--------------------------------------------------------------------===// 442 // API to update Forest information based on modifications 443 // to the CFG... 444 445 /// addNewBlock - Add a new block to the CFG, with the specified immediate 446 /// dominator. 447 /// 448 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 449 450 /// setImmediateDominator - Update the immediate dominator information to 451 /// change the current immediate dominator for the specified block 452 /// to another block. This method requires that BB for NewIDom 453 /// already have an ETNode, otherwise just use addNewBlock. 454 /// 455 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 456 /// print - Convert to human readable form 457 /// 458 virtual void print(std::ostream &OS, const Module* = 0) const; 459 void print(std::ostream *OS, const Module* M = 0) const { 460 if (OS) print(*OS, M); 461 } 462 virtual void dump(); 463protected: 464 /// getNode - return the (Post)DominatorTree node for the specified basic 465 /// block. This is the same as using operator[] on this class. 466 /// 467 inline ETNode *getNode(BasicBlock *BB) const { 468 ETMapType::const_iterator i = Nodes.find(BB); 469 return (i != Nodes.end()) ? i->second : 0; 470 } 471 472 inline ETNode *operator[](BasicBlock *BB) const { 473 return getNode(BB); 474 } 475 476 void reset(); 477 ETMapType Nodes; 478 bool DFSInfoValid; 479 unsigned int SlowQueries; 480 481}; 482 483//==------------------------------------- 484/// ETForest Class - Concrete subclass of ETForestBase that is used to 485/// compute a forwards ET-Forest. 486 487class ETForest : public ETForestBase { 488public: 489 static char ID; // Pass identification, replacement for typeid 490 491 ETForest() : ETForestBase((intptr_t)&ID, false) {} 492 493 BasicBlock *getRoot() const { 494 assert(Roots.size() == 1 && "Should always have entry node!"); 495 return Roots[0]; 496 } 497 498 virtual bool runOnFunction(Function &F) { 499 reset(); // Reset from the last time we were run... 500 DominatorTree &DT = getAnalysis<DominatorTree>(); 501 Roots = DT.getRoots(); 502 calculate(DT); 503 return false; 504 } 505 506 void calculate(const DominatorTree &DT); 507 // FIXME : There is no need to make getNodeForBlock public. Fix 508 // predicate simplifier. 509 ETNode *getNodeForBlock(BasicBlock *BB); 510}; 511 512//===----------------------------------------------------------------------===// 513/// DominanceFrontierBase - Common base class for computing forward and inverse 514/// dominance frontiers for a function. 515/// 516class DominanceFrontierBase : public DominatorBase { 517public: 518 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 519 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 520protected: 521 DomSetMapType Frontiers; 522public: 523 DominanceFrontierBase(intptr_t ID, bool isPostDom) 524 : DominatorBase(ID, isPostDom) {} 525 526 virtual void releaseMemory() { Frontiers.clear(); } 527 528 // Accessor interface: 529 typedef DomSetMapType::iterator iterator; 530 typedef DomSetMapType::const_iterator const_iterator; 531 iterator begin() { return Frontiers.begin(); } 532 const_iterator begin() const { return Frontiers.begin(); } 533 iterator end() { return Frontiers.end(); } 534 const_iterator end() const { return Frontiers.end(); } 535 iterator find(BasicBlock *B) { return Frontiers.find(B); } 536 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 537 538 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 539 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 540 Frontiers.insert(std::make_pair(BB, frontier)); 541 } 542 543 void addToFrontier(iterator I, BasicBlock *Node) { 544 assert(I != end() && "BB is not in DominanceFrontier!"); 545 I->second.insert(Node); 546 } 547 548 void removeFromFrontier(iterator I, BasicBlock *Node) { 549 assert(I != end() && "BB is not in DominanceFrontier!"); 550 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 551 I->second.erase(Node); 552 } 553 554 /// print - Convert to human readable form 555 /// 556 virtual void print(std::ostream &OS, const Module* = 0) const; 557 void print(std::ostream *OS, const Module* M = 0) const { 558 if (OS) print(*OS, M); 559 } 560 virtual void dump(); 561}; 562 563 564//===------------------------------------- 565/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 566/// used to compute a forward dominator frontiers. 567/// 568class DominanceFrontier : public DominanceFrontierBase { 569public: 570 static char ID; // Pass ID, replacement for typeid 571 DominanceFrontier() : 572 DominanceFrontierBase((intptr_t)& ID, false) {} 573 574 BasicBlock *getRoot() const { 575 assert(Roots.size() == 1 && "Should always have entry node!"); 576 return Roots[0]; 577 } 578 579 virtual bool runOnFunction(Function &) { 580 Frontiers.clear(); 581 DominatorTree &DT = getAnalysis<DominatorTree>(); 582 Roots = DT.getRoots(); 583 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 584 calculate(DT, DT[Roots[0]]); 585 return false; 586 } 587 588 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 589 AU.setPreservesAll(); 590 AU.addRequired<DominatorTree>(); 591 } 592 593private: 594 const DomSetType &calculate(const DominatorTree &DT, 595 const DomTreeNode *Node); 596}; 597 598 599} // End llvm namespace 600 601#endif 602