Dominators.h revision 3dc6776b338f81e2d47daa42cc12c9f91053043d
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 the ImmediateDominator as an explicit tree 12// structure. 13// 2. ETForest: Efficient data structure for dominance comparisons and 14// nearest-common-ancestor queries. 15// 3. DominanceFrontier: Calculate and hold the dominance frontier for a 16// function. 17// 18// These data structures are listed in increasing order of complexity. It 19// takes longer to calculate the dominator frontier, for example, than the 20// ImmediateDominator mapping. 21// 22//===----------------------------------------------------------------------===// 23 24#ifndef LLVM_ANALYSIS_DOMINATORS_H 25#define LLVM_ANALYSIS_DOMINATORS_H 26 27#include "llvm/Analysis/ET-Forest.h" 28#include "llvm/Pass.h" 29#include <set> 30 31namespace llvm { 32 33class Instruction; 34 35template <typename GraphType> struct GraphTraits; 36 37//===----------------------------------------------------------------------===// 38/// DominatorBase - Base class that other, more interesting dominator analyses 39/// inherit from. 40/// 41class DominatorBase : public FunctionPass { 42protected: 43 std::vector<BasicBlock*> Roots; 44 const bool IsPostDominators; 45 46 inline DominatorBase(bool isPostDom) : Roots(), IsPostDominators(isPostDom) {} 47public: 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 Node; 65protected: 66 std::map<BasicBlock*, Node*> Nodes; 67 void reset(); 68 typedef std::map<BasicBlock*, Node*> NodeMapType; 69 70 Node *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 Node { 92 friend class DominatorTree; 93 friend struct PostDominatorTree; 94 friend class DominatorTreeBase; 95 BasicBlock *TheBB; 96 Node *IDom; 97 std::vector<Node*> Children; 98 public: 99 typedef std::vector<Node*>::iterator iterator; 100 typedef std::vector<Node*>::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 Node *getIDom() const { return IDom; } 109 inline const std::vector<Node*> &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 Node *N) const { 115 const Node *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 Node *N) const { 126 if (N == this) return true; // A node trivially dominates itself. 127 return properlyDominates(N); 128 } 129 130 private: 131 inline Node(BasicBlock *BB, Node *iDom) : TheBB(BB), IDom(iDom) {} 132 inline Node *addChild(Node *C) { Children.push_back(C); return C; } 133 134 void setIDom(Node *NewIDom); 135 }; 136 137public: 138 DominatorTreeBase(bool isPostDom) : DominatorBase(isPostDom) {} 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 Node *getNode(BasicBlock *BB) const { 147 NodeMapType::const_iterator i = Nodes.find(BB); 148 return (i != Nodes.end()) ? i->second : 0; 149 } 150 151 inline Node *operator[](BasicBlock *BB) const { 152 return getNode(BB); 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 Node *getRootNode() { return RootNode; } 163 const Node *getRootNode() const { return RootNode; } 164 165 //===--------------------------------------------------------------------===// 166 // API to update (Post)DominatorTree information based on modifications to 167 // the CFG... 168 169 /// createNewNode - Add a new node to the dominator tree information. This 170 /// creates a new node as a child of IDomNode, linking it into the children 171 /// list of the immediate dominator. 172 /// 173 Node *createNewNode(BasicBlock *BB, Node *IDomNode) { 174 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 175 assert(IDomNode && "Not immediate dominator specified for block!"); 176 return Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode)); 177 } 178 179 /// changeImmediateDominator - This method is used to update the dominator 180 /// tree information when a node's immediate dominator changes. 181 /// 182 void changeImmediateDominator(Node *N, Node *NewIDom) { 183 assert(N && NewIDom && "Cannot change null node pointers!"); 184 N->setIDom(NewIDom); 185 } 186 187 /// removeNode - Removes a node from the dominator tree. Block must not 188 /// dominate any other blocks. Invalidates any node pointing to removed 189 /// block. 190 void removeNode(BasicBlock *BB) { 191 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 192 Nodes.erase(BB); 193 } 194 195 /// print - Convert to human readable form 196 /// 197 virtual void print(std::ostream &OS, const Module* = 0) const; 198 void print(std::ostream *OS, const Module* M = 0) const { 199 if (OS) print(*OS, M); 200 } 201}; 202 203//===------------------------------------- 204/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 205/// compute a normal dominator tree. 206/// 207class DominatorTree : public DominatorTreeBase { 208public: 209 DominatorTree() : DominatorTreeBase(false) {} 210 211 BasicBlock *getRoot() const { 212 assert(Roots.size() == 1 && "Should always have entry node!"); 213 return Roots[0]; 214 } 215 216 virtual bool runOnFunction(Function &F); 217 218 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 219 AU.setPreservesAll(); 220 } 221private: 222 void calculate(Function& F); 223 Node *getNodeForBlock(BasicBlock *BB); 224 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 225 void Compress(BasicBlock *V, InfoRec &VInfo); 226 BasicBlock *Eval(BasicBlock *v); 227 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 228 inline BasicBlock *getIDom(BasicBlock *BB) const { 229 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 230 return I != IDoms.end() ? I->second : 0; 231 } 232}; 233 234//===------------------------------------- 235/// DominatorTree GraphTraits specialization so the DominatorTree can be 236/// iterable by generic graph iterators. 237/// 238template <> struct GraphTraits<DominatorTree::Node*> { 239 typedef DominatorTree::Node NodeType; 240 typedef NodeType::iterator ChildIteratorType; 241 242 static NodeType *getEntryNode(NodeType *N) { 243 return N; 244 } 245 static inline ChildIteratorType child_begin(NodeType* N) { 246 return N->begin(); 247 } 248 static inline ChildIteratorType child_end(NodeType* N) { 249 return N->end(); 250 } 251}; 252 253template <> struct GraphTraits<DominatorTree*> 254 : public GraphTraits<DominatorTree::Node*> { 255 static NodeType *getEntryNode(DominatorTree *DT) { 256 return DT->getRootNode(); 257 } 258}; 259 260 261//===------------------------------------- 262/// ET-Forest Class - Class used to construct forwards and backwards 263/// ET-Forests 264/// 265class ETForestBase : public DominatorBase { 266public: 267 ETForestBase(bool isPostDom) : DominatorBase(isPostDom), Nodes(), 268 DFSInfoValid(false), SlowQueries(0) {} 269 270 virtual void releaseMemory() { reset(); } 271 272 typedef std::map<BasicBlock*, ETNode*> ETMapType; 273 274 void updateDFSNumbers(); 275 276 /// dominates - Return true if A dominates B. 277 /// 278 inline bool dominates(BasicBlock *A, BasicBlock *B) { 279 if (A == B) 280 return true; 281 282 ETNode *NodeA = getNode(A); 283 ETNode *NodeB = getNode(B); 284 285 if (DFSInfoValid) 286 return NodeB->DominatedBy(NodeA); 287 else { 288 // If we end up with too many slow queries, just update the 289 // DFS numbers on the theory that we are going to keep querying. 290 SlowQueries++; 291 if (SlowQueries > 32) { 292 updateDFSNumbers(); 293 return NodeB->DominatedBy(NodeA); 294 } 295 return NodeB->DominatedBySlow(NodeA); 296 } 297 } 298 299 // dominates - Return true if A dominates B. This performs the 300 // special checks necessary if A and B are in the same basic block. 301 bool dominates(Instruction *A, Instruction *B); 302 303 /// properlyDominates - Return true if A dominates B and A != B. 304 /// 305 bool properlyDominates(BasicBlock *A, BasicBlock *B) { 306 return dominates(A, B) && A != B; 307 } 308 309 /// isReachableFromEntry - Return true if A is dominated by the entry 310 /// block of the function containing it. 311 const bool isReachableFromEntry(BasicBlock* A); 312 313 /// Return the nearest common dominator of A and B. 314 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const { 315 ETNode *NodeA = getNode(A); 316 ETNode *NodeB = getNode(B); 317 318 ETNode *Common = NodeA->NCA(NodeB); 319 if (!Common) 320 return NULL; 321 return Common->getData<BasicBlock>(); 322 } 323 324 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 325 AU.setPreservesAll(); 326 AU.addRequired<DominatorTree>(); 327 } 328 //===--------------------------------------------------------------------===// 329 // API to update Forest information based on modifications 330 // to the CFG... 331 332 /// addNewBlock - Add a new block to the CFG, with the specified immediate 333 /// dominator. 334 /// 335 void addNewBlock(BasicBlock *BB, BasicBlock *IDom); 336 337 /// setImmediateDominator - Update the immediate dominator information to 338 /// change the current immediate dominator for the specified block 339 /// to another block. This method requires that BB for NewIDom 340 /// already have an ETNode, otherwise just use addNewBlock. 341 /// 342 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom); 343 /// print - Convert to human readable form 344 /// 345 virtual void print(std::ostream &OS, const Module* = 0) const; 346 void print(std::ostream *OS, const Module* M = 0) const { 347 if (OS) print(*OS, M); 348 } 349protected: 350 /// getNode - return the (Post)DominatorTree node for the specified basic 351 /// block. This is the same as using operator[] on this class. 352 /// 353 inline ETNode *getNode(BasicBlock *BB) const { 354 ETMapType::const_iterator i = Nodes.find(BB); 355 return (i != Nodes.end()) ? i->second : 0; 356 } 357 358 inline ETNode *operator[](BasicBlock *BB) const { 359 return getNode(BB); 360 } 361 362 void reset(); 363 ETMapType Nodes; 364 bool DFSInfoValid; 365 unsigned int SlowQueries; 366 367}; 368 369//==------------------------------------- 370/// ETForest Class - Concrete subclass of ETForestBase that is used to 371/// compute a forwards ET-Forest. 372 373class ETForest : public ETForestBase { 374public: 375 ETForest() : ETForestBase(false) {} 376 377 BasicBlock *getRoot() const { 378 assert(Roots.size() == 1 && "Should always have entry node!"); 379 return Roots[0]; 380 } 381 382 virtual bool runOnFunction(Function &F) { 383 reset(); // Reset from the last time we were run... 384 DominatorTree &DT = getAnalysis<DominatorTree>(); 385 Roots = DT.getRoots(); 386 calculate(DT); 387 return false; 388 } 389 390 void calculate(const DominatorTree &DT); 391 ETNode *getNodeForBlock(BasicBlock *BB); 392}; 393 394//===----------------------------------------------------------------------===// 395/// DominanceFrontierBase - Common base class for computing forward and inverse 396/// dominance frontiers for a function. 397/// 398class DominanceFrontierBase : public DominatorBase { 399public: 400 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 401 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 402protected: 403 DomSetMapType Frontiers; 404public: 405 DominanceFrontierBase(bool isPostDom) : DominatorBase(isPostDom) {} 406 407 virtual void releaseMemory() { Frontiers.clear(); } 408 409 // Accessor interface: 410 typedef DomSetMapType::iterator iterator; 411 typedef DomSetMapType::const_iterator const_iterator; 412 iterator begin() { return Frontiers.begin(); } 413 const_iterator begin() const { return Frontiers.begin(); } 414 iterator end() { return Frontiers.end(); } 415 const_iterator end() const { return Frontiers.end(); } 416 iterator find(BasicBlock *B) { return Frontiers.find(B); } 417 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 418 419 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 420 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 421 Frontiers.insert(std::make_pair(BB, frontier)); 422 } 423 424 void addToFrontier(iterator I, BasicBlock *Node) { 425 assert(I != end() && "BB is not in DominanceFrontier!"); 426 I->second.insert(Node); 427 } 428 429 void removeFromFrontier(iterator I, BasicBlock *Node) { 430 assert(I != end() && "BB is not in DominanceFrontier!"); 431 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 432 I->second.erase(Node); 433 } 434 435 /// print - Convert to human readable form 436 /// 437 virtual void print(std::ostream &OS, const Module* = 0) const; 438 void print(std::ostream *OS, const Module* M = 0) const { 439 if (OS) print(*OS, M); 440 } 441}; 442 443 444//===------------------------------------- 445/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 446/// used to compute a forward dominator frontiers. 447/// 448class DominanceFrontier : public DominanceFrontierBase { 449public: 450 DominanceFrontier() : DominanceFrontierBase(false) {} 451 452 BasicBlock *getRoot() const { 453 assert(Roots.size() == 1 && "Should always have entry node!"); 454 return Roots[0]; 455 } 456 457 virtual bool runOnFunction(Function &) { 458 Frontiers.clear(); 459 DominatorTree &DT = getAnalysis<DominatorTree>(); 460 Roots = DT.getRoots(); 461 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 462 calculate(DT, DT[Roots[0]]); 463 return false; 464 } 465 466 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 467 AU.setPreservesAll(); 468 AU.addRequired<DominatorTree>(); 469 } 470private: 471 const DomSetType &calculate(const DominatorTree &DT, 472 const DominatorTree::Node *Node); 473}; 474 475 476} // End llvm namespace 477 478#endif 479