Dominators.h revision bef204db6fc6b2e69f93f23f644617a3c01968aa
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. DominanceFrontier: Calculate and hold the dominance frontier for a 13// function. 14// 15// These data structures are listed in increasing order of complexity. It 16// takes longer to calculate the dominator frontier, for example, than the 17// DominatorTree mapping. 18// 19//===----------------------------------------------------------------------===// 20 21#ifndef LLVM_ANALYSIS_DOMINATORS_H 22#define LLVM_ANALYSIS_DOMINATORS_H 23 24#include "llvm/Pass.h" 25#include <set> 26 27namespace llvm { 28 29class Instruction; 30 31template <typename GraphType> struct GraphTraits; 32 33//===----------------------------------------------------------------------===// 34/// DominatorBase - Base class that other, more interesting dominator analyses 35/// inherit from. 36/// 37class DominatorBase : public FunctionPass { 38protected: 39 std::vector<BasicBlock*> Roots; 40 const bool IsPostDominators; 41 inline DominatorBase(intptr_t ID, bool isPostDom) : 42 FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {} 43public: 44 45 /// getRoots - Return the root blocks of the current CFG. This may include 46 /// multiple blocks if we are computing post dominators. For forward 47 /// dominators, this will always be a single block (the entry node). 48 /// 49 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 50 51 /// isPostDominator - Returns true if analysis based of postdoms 52 /// 53 bool isPostDominator() const { return IsPostDominators; } 54}; 55 56 57//===----------------------------------------------------------------------===// 58// DomTreeNode - Dominator Tree Node 59class DominatorTreeBase; 60class PostDominatorTree; 61class DomTreeNode { 62 BasicBlock *TheBB; 63 DomTreeNode *IDom; 64 std::vector<DomTreeNode*> Children; 65 int DFSNumIn, DFSNumOut; 66 67 friend class DominatorTreeBase; 68 friend class PostDominatorTree; 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 87private: 88 // Return true if this node is dominated by other. Use this only if DFS info is valid. 89 bool DominatedBy(const DomTreeNode *other) const { 90 return this->DFSNumIn >= other->DFSNumIn && 91 this->DFSNumOut <= other->DFSNumOut; 92 } 93 94 /// assignDFSNumber - Assign In and Out numbers while walking dominator tree 95 /// in dfs order. 96 void assignDFSNumber(int num); 97}; 98 99//===----------------------------------------------------------------------===// 100/// DominatorTree - Calculate the immediate dominator tree for a function. 101/// 102class DominatorTreeBase : public DominatorBase { 103 104protected: 105 void reset(); 106 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 107 DomTreeNodeMapType DomTreeNodes; 108 DomTreeNode *RootNode; 109 110 bool DFSInfoValid; 111 unsigned int SlowQueries; 112 // Information record used during immediate dominators computation. 113 struct InfoRec { 114 unsigned Semi; 115 unsigned Size; 116 BasicBlock *Label, *Parent, *Child, *Ancestor; 117 118 std::vector<BasicBlock*> Bucket; 119 120 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){} 121 }; 122 123 std::map<BasicBlock*, BasicBlock*> IDoms; 124 125 // Vertex - Map the DFS number to the BasicBlock* 126 std::vector<BasicBlock*> Vertex; 127 128 // Info - Collection of information used during the computation of idoms. 129 std::map<BasicBlock*, InfoRec> Info; 130 131 void updateDFSNumbers(); 132 133 public: 134 DominatorTreeBase(intptr_t ID, bool isPostDom) 135 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {} 136 ~DominatorTreeBase() { reset(); } 137 138 virtual void releaseMemory() { reset(); } 139 140 /// getNode - return the (Post)DominatorTree node for the specified basic 141 /// block. This is the same as using operator[] on this class. 142 /// 143 inline DomTreeNode *getNode(BasicBlock *BB) const { 144 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB); 145 return (i != DomTreeNodes.end()) ? i->second : 0; 146 } 147 148 inline DomTreeNode *operator[](BasicBlock *BB) const { 149 return getNode(BB); 150 } 151 152 /// getRootNode - This returns the entry node for the CFG of the function. If 153 /// this tree represents the post-dominance relations for a function, however, 154 /// this root may be a node with the block == NULL. This is the case when 155 /// there are multiple exit nodes from a particular function. Consumers of 156 /// post-dominance information must be capable of dealing with this 157 /// possibility. 158 /// 159 DomTreeNode *getRootNode() { return RootNode; } 160 const DomTreeNode *getRootNode() const { return RootNode; } 161 162 /// properlyDominates - Returns true iff this dominates N and this != N. 163 /// Note that this is not a constant time operation! 164 /// 165 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const { 166 if (A == 0 || B == 0) return false; 167 return dominatedBySlowTreeWalk(A, B); 168 } 169 170 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) { 171 return properlyDominates(getNode(A), getNode(B)); 172 } 173 174 bool dominatedBySlowTreeWalk(const DomTreeNode *A, 175 const DomTreeNode *B) const { 176 const DomTreeNode *IDom; 177 if (A == 0 || B == 0) return false; 178 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B) 179 B = IDom; // Walk up the tree 180 return IDom != 0; 181 } 182 183 184 /// isReachableFromEntry - Return true if A is dominated by the entry 185 /// block of the function containing it. 186 const bool isReachableFromEntry(BasicBlock* A); 187 188 /// dominates - Returns true iff A dominates B. Note that this is not a 189 /// constant time operation! 190 /// 191 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) { 192 if (B == A) 193 return true; // A node trivially dominates itself. 194 195 if (A == 0 || B == 0) 196 return false; 197 198 if (DFSInfoValid) 199 return B->DominatedBy(A); 200 201 // If we end up with too many slow queries, just update the 202 // DFS numbers on the theory that we are going to keep querying. 203 SlowQueries++; 204 if (SlowQueries > 32) { 205 updateDFSNumbers(); 206 return B->DominatedBy(A); 207 } 208 209 return dominatedBySlowTreeWalk(A, B); 210 } 211 212 inline bool dominates(BasicBlock *A, BasicBlock *B) { 213 if (A == B) 214 return true; 215 216 return dominates(getNode(A), getNode(B)); 217 } 218 219 /// findNearestCommonDominator - Find nearest common dominator basic block 220 /// for basic block A and B. If there is no such block then return NULL. 221 BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B); 222 223 // dominates - Return true if A dominates B. This performs the 224 // special checks necessary if A and B are in the same basic block. 225 bool dominates(Instruction *A, Instruction *B); 226 227 //===--------------------------------------------------------------------===// 228 // API to update (Post)DominatorTree information based on modifications to 229 // the CFG... 230 231 /// addNewBlock - Add a new node to the dominator tree information. This 232 /// creates a new node as a child of DomBB dominator node,linking it into 233 /// the children list of the immediate dominator. 234 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) { 235 assert(getNode(BB) == 0 && "Block already in dominator tree!"); 236 DomTreeNode *IDomNode = getNode(DomBB); 237 assert(IDomNode && "Not immediate dominator specified for block!"); 238 DFSInfoValid = false; 239 return DomTreeNodes[BB] = 240 IDomNode->addChild(new DomTreeNode(BB, IDomNode)); 241 } 242 243 /// changeImmediateDominator - This method is used to update the dominator 244 /// tree information when a node's immediate dominator changes. 245 /// 246 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) { 247 assert(N && NewIDom && "Cannot change null node pointers!"); 248 DFSInfoValid = false; 249 N->setIDom(NewIDom); 250 } 251 252 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) { 253 changeImmediateDominator(getNode(BB), getNode(NewBB)); 254 } 255 256 /// removeNode - Removes a node from the dominator tree. Block must not 257 /// dominate any other blocks. Invalidates any node pointing to removed 258 /// block. 259 void removeNode(BasicBlock *BB) { 260 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 261 DomTreeNodes.erase(BB); 262 } 263 264 /// print - Convert to human readable form 265 /// 266 virtual void print(std::ostream &OS, const Module* = 0) const; 267 void print(std::ostream *OS, const Module* M = 0) const { 268 if (OS) print(*OS, M); 269 } 270 virtual void dump(); 271}; 272 273//===------------------------------------- 274/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 275/// compute a normal dominator tree. 276/// 277class DominatorTree : public DominatorTreeBase { 278public: 279 static char ID; // Pass ID, replacement for typeid 280 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {} 281 282 BasicBlock *getRoot() const { 283 assert(Roots.size() == 1 && "Should always have entry node!"); 284 return Roots[0]; 285 } 286 287 virtual bool runOnFunction(Function &F); 288 289 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 290 AU.setPreservesAll(); 291 } 292 293 /// splitBlock 294 /// BB is split and now it has one successor. Update dominator tree to 295 /// reflect this change. 296 void splitBlock(BasicBlock *BB); 297private: 298 void calculate(Function& F); 299 DomTreeNode *getNodeForBlock(BasicBlock *BB); 300 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N); 301 void Compress(BasicBlock *V); 302 BasicBlock *Eval(BasicBlock *v); 303 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo); 304 inline BasicBlock *getIDom(BasicBlock *BB) const { 305 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 306 return I != IDoms.end() ? I->second : 0; 307 } 308}; 309 310//===------------------------------------- 311/// DominatorTree GraphTraits specialization so the DominatorTree can be 312/// iterable by generic graph iterators. 313/// 314template <> struct GraphTraits<DomTreeNode*> { 315 typedef DomTreeNode NodeType; 316 typedef NodeType::iterator ChildIteratorType; 317 318 static NodeType *getEntryNode(NodeType *N) { 319 return N; 320 } 321 static inline ChildIteratorType child_begin(NodeType* N) { 322 return N->begin(); 323 } 324 static inline ChildIteratorType child_end(NodeType* N) { 325 return N->end(); 326 } 327}; 328 329template <> struct GraphTraits<DominatorTree*> 330 : public GraphTraits<DomTreeNode*> { 331 static NodeType *getEntryNode(DominatorTree *DT) { 332 return DT->getRootNode(); 333 } 334}; 335 336 337//===----------------------------------------------------------------------===// 338/// DominanceFrontierBase - Common base class for computing forward and inverse 339/// dominance frontiers for a function. 340/// 341class DominanceFrontierBase : public DominatorBase { 342public: 343 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 344 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 345protected: 346 DomSetMapType Frontiers; 347public: 348 DominanceFrontierBase(intptr_t ID, bool isPostDom) 349 : DominatorBase(ID, isPostDom) {} 350 351 virtual void releaseMemory() { Frontiers.clear(); } 352 353 // Accessor interface: 354 typedef DomSetMapType::iterator iterator; 355 typedef DomSetMapType::const_iterator const_iterator; 356 iterator begin() { return Frontiers.begin(); } 357 const_iterator begin() const { return Frontiers.begin(); } 358 iterator end() { return Frontiers.end(); } 359 const_iterator end() const { return Frontiers.end(); } 360 iterator find(BasicBlock *B) { return Frontiers.find(B); } 361 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 362 363 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 364 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 365 Frontiers.insert(std::make_pair(BB, frontier)); 366 } 367 368 void addToFrontier(iterator I, BasicBlock *Node) { 369 assert(I != end() && "BB is not in DominanceFrontier!"); 370 I->second.insert(Node); 371 } 372 373 void removeFromFrontier(iterator I, BasicBlock *Node) { 374 assert(I != end() && "BB is not in DominanceFrontier!"); 375 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 376 I->second.erase(Node); 377 } 378 379 /// print - Convert to human readable form 380 /// 381 virtual void print(std::ostream &OS, const Module* = 0) const; 382 void print(std::ostream *OS, const Module* M = 0) const { 383 if (OS) print(*OS, M); 384 } 385 virtual void dump(); 386}; 387 388 389//===------------------------------------- 390/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 391/// used to compute a forward dominator frontiers. 392/// 393class DominanceFrontier : public DominanceFrontierBase { 394public: 395 static char ID; // Pass ID, replacement for typeid 396 DominanceFrontier() : 397 DominanceFrontierBase((intptr_t)& ID, false) {} 398 399 BasicBlock *getRoot() const { 400 assert(Roots.size() == 1 && "Should always have entry node!"); 401 return Roots[0]; 402 } 403 404 virtual bool runOnFunction(Function &) { 405 Frontiers.clear(); 406 DominatorTree &DT = getAnalysis<DominatorTree>(); 407 Roots = DT.getRoots(); 408 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 409 calculate(DT, DT[Roots[0]]); 410 return false; 411 } 412 413 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 414 AU.setPreservesAll(); 415 AU.addRequired<DominatorTree>(); 416 } 417 418 /// splitBlock 419 /// BB is split and now it has one successor. Update dominace frontier to 420 /// reflect this change. 421 void splitBlock(BasicBlock *BB); 422 423private: 424 const DomSetType &calculate(const DominatorTree &DT, 425 const DomTreeNode *Node); 426}; 427 428 429} // End llvm namespace 430 431#endif 432