Dominators.h revision bec7647f985d54d2be2100e3813b85267cf1fe49
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/// DominatorTree - Calculate the immediate dominator tree for a function. 61/// 62class DominatorTreeBase : public DominatorBase { 63public: 64 class DomTreeNode; 65protected: 66 std::map<BasicBlock*, DomTreeNode*> DomTreeNodes; 67 void reset(); 68 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 69 70 DomTreeNode *RootNode; 71 72 struct InfoRec { 73 unsigned Semi; 74 unsigned Size; 75 BasicBlock *Label, *Parent, *Child, *Ancestor; 76 77 std::vector<BasicBlock*> Bucket; 78 79 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 80 }; 81 82 std::map<BasicBlock*, BasicBlock*> IDoms; 83 84 // Vertex - Map the DFS number to the BasicBlock* 85 std::vector<BasicBlock*> Vertex; 86 87 // Info - Collection of information used during the computation of idoms. 88 std::map<BasicBlock*, InfoRec> Info; 89 90public: 91 class DomTreeNode { 92 friend class DominatorTree; 93 friend struct PostDominatorTree; 94 friend class DominatorTreeBase; 95 BasicBlock *TheBB; 96 DomTreeNode *IDom; 97 std::vector<DomTreeNode*> Children; 98 public: 99 typedef std::vector<DomTreeNode*>::iterator iterator; 100 typedef std::vector<DomTreeNode*>::const_iterator const_iterator; 101 102 iterator begin() { return Children.begin(); } 103 iterator end() { return Children.end(); } 104 const_iterator begin() const { return Children.begin(); } 105 const_iterator end() const { return Children.end(); } 106 107 inline BasicBlock *getBlock() const { return TheBB; } 108 inline DomTreeNode *getIDom() const { return IDom; } 109 inline const std::vector<DomTreeNode*> &getChildren() const { return Children; } 110 111 /// properlyDominates - Returns true iff this dominates N and this != N. 112 /// Note that this is not a constant time operation! 113 /// 114 bool properlyDominates(const DomTreeNode *N) const { 115 const DomTreeNode *IDom; 116 if (this == 0 || N == 0) return false; 117 while ((IDom = N->getIDom()) != 0 && IDom != this) 118 N = IDom; // Walk up the tree 119 return IDom != 0; 120 } 121 122 /// dominates - Returns true iff this dominates N. Note that this is not a 123 /// constant time operation! 124 /// 125 inline bool dominates(const DomTreeNode *N) const { 126 if (N == this) return true; // A node trivially dominates itself. 127 return properlyDominates(N); 128 } 129 130 private: 131 inline DomTreeNode(BasicBlock *BB, DomTreeNode *iDom) : TheBB(BB), IDom(iDom) {} 132 inline DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; } 133 134 void setIDom(DomTreeNode *NewIDom); 135 }; 136 137public: 138 DominatorTreeBase(intptr_t ID, bool isPostDom) 139 : DominatorBase(ID, isPostDom) {} 140 ~DominatorTreeBase() { reset(); } 141 142 virtual void releaseMemory() { reset(); } 143 144 /// getNode - return the (Post)DominatorTree node for the specified basic 145 /// block. This is the same as using operator[] on this class. 146 /// 147 inline DomTreeNode *getNode(BasicBlock *BB) const { 148 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB); 149 return (i != DomTreeNodes.end()) ? i->second : 0; 150 } 151 152 inline DomTreeNode *operator[](BasicBlock *BB) const { 153 return getNode(BB); 154 } 155 156 /// getRootNode - This returns the entry node for the CFG of the function. If 157 /// this tree represents the post-dominance relations for a function, however, 158 /// this root may be a node with the block == NULL. This is the case when 159 /// there are multiple exit nodes from a particular function. Consumers of 160 /// post-dominance information must be capable of dealing with this 161 /// possibility. 162 /// 163 DomTreeNode *getRootNode() { return RootNode; } 164 const DomTreeNode *getRootNode() const { return RootNode; } 165 166 //===--------------------------------------------------------------------===// 167 // API to update (Post)DominatorTree information based on modifications to 168 // the CFG... 169 170 /// createNewNode - Add a new node to the dominator tree information. This 171 /// creates a new node as a child of IDomNode, linking it into the children 172 /// list of the immediate dominator. 173 /// 174 DomTreeNode *createNewNode(BasicBlock *BB, DomTreeNode *IDomNode) { 175 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 176 assert(IDomNode && "Not immediate dominator specified for block!"); 177 return DomTreeNodes[BB] = IDomNode->addChild(new DomTreeNode(BB, IDomNode)); 178 } 179 180 /// changeImmediateDominator - This method is used to update the dominator 181 /// tree information when a node's immediate dominator changes. 182 /// 183 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 184 assert(N && NewIDom && "Cannot change null node pointers!"); 185 N->setIDom(NewIDom); 186 } 187 188 /// removeNode - Removes a node from the dominator tree. Block must not 189 /// dominate any other blocks. Invalidates any node pointing to removed 190 /// block. 191 void removeNode(BasicBlock *BB) { 192 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 193 DomTreeNodes.erase(BB); 194 } 195 196 /// print - Convert to human readable form 197 /// 198 virtual void print(std::ostream &OS, const Module* = 0) const; 199 void print(std::ostream *OS, const Module* M = 0) const { 200 if (OS) print(*OS, M); 201 } 202 virtual void dump(); 203}; 204 205//===------------------------------------- 206/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 207/// compute a normal dominator tree. 208/// 209class DominatorTree : public DominatorTreeBase { 210public: 211 static char ID; // Pass ID, replacement for typeid 212 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 213 214 BasicBlock *getRoot() const { 215 assert(Roots.size() == 1 && "Should always have entry node!"); 216 return Roots[0]; 217 } 218 219 virtual bool runOnFunction(Function &F); 220 221 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 222 AU.setPreservesAll(); 223 } 224private: 225 void calculate(Function& F); 226 DomTreeNode *getNodeForBlock(BasicBlock *BB); 227 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 228 void Compress(BasicBlock *V); 229 BasicBlock *Eval(BasicBlock *v); 230 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 231 inline BasicBlock *getIDom(BasicBlock *BB) const { 232 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 233 return I != IDoms.end() ? I->second : 0; 234 } 235}; 236 237//===------------------------------------- 238/// DominatorTree GraphTraits specialization so the DominatorTree can be 239/// iterable by generic graph iterators. 240/// 241template <> struct GraphTraits<DominatorTree::DomTreeNode*> { 242 typedef DominatorTree::DomTreeNode NodeType; 243 typedef NodeType::iterator ChildIteratorType; 244 245 static NodeType *getEntryNode(NodeType *N) { 246 return N; 247 } 248 static inline ChildIteratorType child_begin(NodeType* N) { 249 return N->begin(); 250 } 251 static inline ChildIteratorType child_end(NodeType* N) { 252 return N->end(); 253 } 254}; 255 256template <> struct GraphTraits<DominatorTree*> 257 : public GraphTraits<DominatorTree::DomTreeNode*> { 258 static NodeType *getEntryNode(DominatorTree *DT) { 259 return DT->getRootNode(); 260 } 261}; 262 263 264//===------------------------------------- 265/// ET-Forest Class - Class used to construct forwards and backwards 266/// ET-Forests 267/// 268class ETForestBase : public DominatorBase { 269public: 270 ETForestBase(intptr_t ID, bool isPostDom) 271 : DominatorBase(ID, isPostDom), Nodes(), 272 DFSInfoValid(false), SlowQueries(0) {} 273 274 virtual void releaseMemory() { reset(); } 275 276 typedef std::map<BasicBlock*, ETNode*> ETMapType; 277 278 void updateDFSNumbers(); 279 280 /// dominates - Return true if A dominates B. 281 /// 282 inline bool dominates(BasicBlock *A, BasicBlock *B) { 283 if (A == B) 284 return true; 285 286 ETNode *NodeA = getNode(A); 287 ETNode *NodeB = getNode(B); 288 289 if (DFSInfoValid) 290 return NodeB->DominatedBy(NodeA); 291 else { 292 // If we end up with too many slow queries, just update the 293 // DFS numbers on the theory that we are going to keep querying. 294 SlowQueries++; 295 if (SlowQueries > 32) { 296 updateDFSNumbers(); 297 return NodeB->DominatedBy(NodeA); 298 } 299 return NodeB->DominatedBySlow(NodeA); 300 } 301 } 302 303 // dominates - Return true if A dominates B. This performs the 304 // special checks necessary if A and B are in the same basic block. 305 bool dominates(Instruction *A, Instruction *B); 306 307 /// properlyDominates - Return true if A dominates B and A != B. 308 /// 309 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 310 return dominates(A, B) && A != B; 311 } 312 313 /// isReachableFromEntry - Return true if A is dominated by the entry 314 /// block of the function containing it. 315 const bool isReachableFromEntry(BasicBlock* A); 316 317 /// Return the nearest common dominator of A and B. 318 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 319 ETNode *NodeA = getNode(A); 320 ETNode *NodeB = getNode(B); 321 322 ETNode *Common = NodeA->NCA(NodeB); 323 if (!Common) 324 return NULL; 325 return Common->getData<BasicBlock>(); 326 } 327 328 /// Return the immediate dominator of A. 329 BasicBlock *getIDom(BasicBlock *A) const { 330 ETNode *NodeA = getNode(A); 331 if (!NodeA) return 0; 332 const ETNode *idom = NodeA->getFather(); 333 return idom ? idom->getData<BasicBlock>() : 0; 334 } 335 336 void getChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const { 337 ETNode *NodeA = getNode(A); 338 if (!NodeA) return; 339 const ETNode* son = NodeA->getSon(); 340 341 if (!son) return; 342 children.push_back(son->getData<BasicBlock>()); 343 344 const ETNode* brother = son->getBrother(); 345 while (brother != son) { 346 children.push_back(brother->getData<BasicBlock>()); 347 brother = brother->getBrother(); 348 } 349 } 350 351 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 352 AU.setPreservesAll(); 353 AU.addRequired<DominatorTree>(); 354 } 355 //===--------------------------------------------------------------------===// 356 // API to update Forest information based on modifications 357 // to the CFG... 358 359 /// addNewBlock - Add a new block to the CFG, with the specified immediate 360 /// dominator. 361 /// 362 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 363 364 /// setImmediateDominator - Update the immediate dominator information to 365 /// change the current immediate dominator for the specified block 366 /// to another block. This method requires that BB for NewIDom 367 /// already have an ETNode, otherwise just use addNewBlock. 368 /// 369 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 370 /// print - Convert to human readable form 371 /// 372 virtual void print(std::ostream &OS, const Module* = 0) const; 373 void print(std::ostream *OS, const Module* M = 0) const { 374 if (OS) print(*OS, M); 375 } 376 virtual void dump(); 377protected: 378 /// getNode - return the (Post)DominatorTree node for the specified basic 379 /// block. This is the same as using operator[] on this class. 380 /// 381 inline ETNode *getNode(BasicBlock *BB) const { 382 ETMapType::const_iterator i = Nodes.find(BB); 383 return (i != Nodes.end()) ? i->second : 0; 384 } 385 386 inline ETNode *operator[](BasicBlock *BB) const { 387 return getNode(BB); 388 } 389 390 void reset(); 391 ETMapType Nodes; 392 bool DFSInfoValid; 393 unsigned int SlowQueries; 394 395}; 396 397//==------------------------------------- 398/// ETForest Class - Concrete subclass of ETForestBase that is used to 399/// compute a forwards ET-Forest. 400 401class ETForest : public ETForestBase { 402public: 403 static char ID; // Pass identification, replacement for typeid 404 405 ETForest() : ETForestBase((intptr_t)&ID, false) {} 406 407 BasicBlock *getRoot() const { 408 assert(Roots.size() == 1 && "Should always have entry node!"); 409 return Roots[0]; 410 } 411 412 virtual bool runOnFunction(Function &F) { 413 reset(); // Reset from the last time we were run... 414 DominatorTree &DT = getAnalysis<DominatorTree>(); 415 Roots = DT.getRoots(); 416 calculate(DT); 417 return false; 418 } 419 420 void calculate(const DominatorTree &DT); 421 ETNode *getNodeForBlock(BasicBlock *BB); 422}; 423 424//===----------------------------------------------------------------------===// 425/// DominanceFrontierBase - Common base class for computing forward and inverse 426/// dominance frontiers for a function. 427/// 428class DominanceFrontierBase : public DominatorBase { 429public: 430 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 431 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 432protected: 433 DomSetMapType Frontiers; 434public: 435 DominanceFrontierBase(intptr_t ID, bool isPostDom) 436 : DominatorBase(ID, isPostDom) {} 437 438 virtual void releaseMemory() { Frontiers.clear(); } 439 440 // Accessor interface: 441 typedef DomSetMapType::iterator iterator; 442 typedef DomSetMapType::const_iterator const_iterator; 443 iterator begin() { return Frontiers.begin(); } 444 const_iterator begin() const { return Frontiers.begin(); } 445 iterator end() { return Frontiers.end(); } 446 const_iterator end() const { return Frontiers.end(); } 447 iterator find(BasicBlock *B) { return Frontiers.find(B); } 448 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 449 450 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 451 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 452 Frontiers.insert(std::make_pair(BB, frontier)); 453 } 454 455 void addToFrontier(iterator I, BasicBlock *Node) { 456 assert(I != end() && "BB is not in DominanceFrontier!"); 457 I->second.insert(Node); 458 } 459 460 void removeFromFrontier(iterator I, BasicBlock *Node) { 461 assert(I != end() && "BB is not in DominanceFrontier!"); 462 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 463 I->second.erase(Node); 464 } 465 466 /// print - Convert to human readable form 467 /// 468 virtual void print(std::ostream &OS, const Module* = 0) const; 469 void print(std::ostream *OS, const Module* M = 0) const { 470 if (OS) print(*OS, M); 471 } 472 virtual void dump(); 473}; 474 475 476//===------------------------------------- 477/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 478/// used to compute a forward dominator frontiers. 479/// 480class DominanceFrontier : public DominanceFrontierBase { 481public: 482 static char ID; // Pass ID, replacement for typeid 483 DominanceFrontier() : 484 DominanceFrontierBase((intptr_t)& ID, false) {} 485 486 BasicBlock *getRoot() const { 487 assert(Roots.size() == 1 && "Should always have entry node!"); 488 return Roots[0]; 489 } 490 491 virtual bool runOnFunction(Function &) { 492 Frontiers.clear(); 493 DominatorTree &DT = getAnalysis<DominatorTree>(); 494 Roots = DT.getRoots(); 495 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 496 calculate(DT, DT[Roots[0]]); 497 return false; 498 } 499 500 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 501 AU.setPreservesAll(); 502 AU.addRequired<DominatorTree>(); 503 } 504private: 505 const DomSetType &calculate(const DominatorTree &DT, 506 const DominatorTree::DomTreeNode *Node); 507}; 508 509 510} // End llvm namespace 511 512#endif 513