Dominators.h revision 303f47b1dd3166a8abcd5425f863f7b4815a8e42
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#include "llvm/ADT/DenseMap.h" 27 28namespace llvm { 29 30class Instruction; 31 32template <typename GraphType> struct GraphTraits; 33 34//===----------------------------------------------------------------------===// 35/// DominatorBase - Base class that other, more interesting dominator analyses 36/// inherit from. 37/// 38class DominatorBase : public FunctionPass { 39protected: 40 std::vector<BasicBlock*> Roots; 41 const bool IsPostDominators; 42 inline DominatorBase(intptr_t ID, bool isPostDom) : 43 FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {} 44public: 45 46 /// getRoots - Return the root blocks of the current CFG. This may include 47 /// multiple blocks if we are computing post dominators. For forward 48 /// dominators, this will always be a single block (the entry node). 49 /// 50 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; } 51 52 /// isPostDominator - Returns true if analysis based of postdoms 53 /// 54 bool isPostDominator() const { return IsPostDominators; } 55}; 56 57 58//===----------------------------------------------------------------------===// 59// DomTreeNode - Dominator Tree Node 60class DominatorTreeBase; 61class PostDominatorTree; 62class DomTreeNode { 63 BasicBlock *TheBB; 64 DomTreeNode *IDom; 65 std::vector<DomTreeNode*> Children; 66 int DFSNumIn, DFSNumOut; 67 68 friend class DominatorTreeBase; 69 friend class PostDominatorTree; 70public: 71 typedef std::vector<DomTreeNode*>::iterator iterator; 72 typedef std::vector<DomTreeNode*>::const_iterator const_iterator; 73 74 iterator begin() { return Children.begin(); } 75 iterator end() { return Children.end(); } 76 const_iterator begin() const { return Children.begin(); } 77 const_iterator end() const { return Children.end(); } 78 79 BasicBlock *getBlock() const { return TheBB; } 80 DomTreeNode *getIDom() const { return IDom; } 81 const std::vector<DomTreeNode*> &getChildren() const { return Children; } 82 83 DomTreeNode(BasicBlock *BB, DomTreeNode *iDom) 84 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { } 85 DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; } 86 void setIDom(DomTreeNode *NewIDom); 87 88 89 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do 90 /// not call them. 91 unsigned getDFSNumIn() const { return DFSNumIn; } 92 unsigned getDFSNumOut() const { return DFSNumOut; } 93private: 94 // Return true if this node is dominated by other. Use this only if DFS info 95 // is valid. 96 bool DominatedBy(const DomTreeNode *other) const { 97 return this->DFSNumIn >= other->DFSNumIn && 98 this->DFSNumOut <= other->DFSNumOut; 99 } 100}; 101 102//===----------------------------------------------------------------------===// 103/// DominatorTree - Calculate the immediate dominator tree for a function. 104/// 105class DominatorTreeBase : public DominatorBase { 106protected: 107 void reset(); 108 typedef DenseMap<BasicBlock*, DomTreeNode*> DomTreeNodeMapType; 109 DomTreeNodeMapType DomTreeNodes; 110 DomTreeNode *RootNode; 111 112 bool DFSInfoValid; 113 unsigned int SlowQueries; 114 // Information record used during immediate dominators computation. 115 struct InfoRec { 116 unsigned Semi; 117 unsigned Size; 118 BasicBlock *Label, *Parent, *Child, *Ancestor; 119 120 std::vector<BasicBlock*> Bucket; 121 122 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0) {} 123 }; 124 125 DenseMap<BasicBlock*, BasicBlock*> IDoms; 126 127 // Vertex - Map the DFS number to the BasicBlock* 128 std::vector<BasicBlock*> Vertex; 129 130 // Info - Collection of information used during the computation of idoms. 131 DenseMap<BasicBlock*, InfoRec> Info; 132 133public: 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 /// eraseNode - Removes a node from the dominator tree. Block must not 257 /// domiante any other blocks. Removes node from its immediate dominator's 258 /// children list. Deletes dominator node associated with basic block BB. 259 void eraseNode(BasicBlock *BB); 260 261 /// removeNode - Removes a node from the dominator tree. Block must not 262 /// dominate any other blocks. Invalidates any node pointing to removed 263 /// block. 264 void removeNode(BasicBlock *BB) { 265 assert(getNode(BB) && "Removing node that isn't in dominator tree."); 266 DomTreeNodes.erase(BB); 267 } 268 269 /// print - Convert to human readable form 270 /// 271 virtual void print(std::ostream &OS, const Module* = 0) const; 272 void print(std::ostream *OS, const Module* M = 0) const { 273 if (OS) print(*OS, M); 274 } 275 virtual void dump(); 276 277protected: 278 friend void Compress(DominatorTreeBase& DT, BasicBlock *VIn); 279 friend BasicBlock *Eval(DominatorTreeBase& DT, BasicBlock *V); 280 friend void Link(DominatorTreeBase& DT, BasicBlock *V, 281 BasicBlock *W, InfoRec &WInfo); 282 283 template<class GraphT> friend unsigned DFSPass(DominatorTreeBase& DT, 284 typename GraphT::NodeType* V, 285 unsigned N); 286 287 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking 288 /// dominator tree in dfs order. 289 void updateDFSNumbers(); 290 291 DomTreeNode *getNodeForBlock(BasicBlock *BB); 292 293 inline BasicBlock *getIDom(BasicBlock *BB) const { 294 DenseMap<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB); 295 return I != IDoms.end() ? I->second : 0; 296 } 297}; 298 299//===------------------------------------- 300/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 301/// compute a normal dominator tree. 302/// 303class DominatorTree : public DominatorTreeBase { 304public: 305 static char ID; // Pass ID, replacement for typeid 306 DominatorTree() : DominatorTreeBase(intptr_t(&ID), false) {} 307 308 BasicBlock *getRoot() const { 309 assert(Roots.size() == 1 && "Should always have entry node!"); 310 return Roots[0]; 311 } 312 313 virtual bool runOnFunction(Function &F); 314 315 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 316 AU.setPreservesAll(); 317 } 318 319 /// splitBlock 320 /// BB is split and now it has one successor. Update dominator tree to 321 /// reflect this change. 322 void splitBlock(BasicBlock *BB); 323 324private: 325 friend void DTcalculate(DominatorTree& DT, Function& F); 326}; 327 328//===------------------------------------- 329/// DominatorTree GraphTraits specialization so the DominatorTree can be 330/// iterable by generic graph iterators. 331/// 332template <> struct GraphTraits<DomTreeNode*> { 333 typedef DomTreeNode NodeType; 334 typedef NodeType::iterator ChildIteratorType; 335 336 static NodeType *getEntryNode(NodeType *N) { 337 return N; 338 } 339 static inline ChildIteratorType child_begin(NodeType* N) { 340 return N->begin(); 341 } 342 static inline ChildIteratorType child_end(NodeType* N) { 343 return N->end(); 344 } 345}; 346 347template <> struct GraphTraits<DominatorTree*> 348 : public GraphTraits<DomTreeNode*> { 349 static NodeType *getEntryNode(DominatorTree *DT) { 350 return DT->getRootNode(); 351 } 352}; 353 354 355//===----------------------------------------------------------------------===// 356/// DominanceFrontierBase - Common base class for computing forward and inverse 357/// dominance frontiers for a function. 358/// 359class DominanceFrontierBase : public DominatorBase { 360public: 361 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb 362 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map 363protected: 364 DomSetMapType Frontiers; 365public: 366 DominanceFrontierBase(intptr_t ID, bool isPostDom) 367 : DominatorBase(ID, isPostDom) {} 368 369 virtual void releaseMemory() { Frontiers.clear(); } 370 371 // Accessor interface: 372 typedef DomSetMapType::iterator iterator; 373 typedef DomSetMapType::const_iterator const_iterator; 374 iterator begin() { return Frontiers.begin(); } 375 const_iterator begin() const { return Frontiers.begin(); } 376 iterator end() { return Frontiers.end(); } 377 const_iterator end() const { return Frontiers.end(); } 378 iterator find(BasicBlock *B) { return Frontiers.find(B); } 379 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); } 380 381 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) { 382 assert(find(BB) == end() && "Block already in DominanceFrontier!"); 383 Frontiers.insert(std::make_pair(BB, frontier)); 384 } 385 386 /// removeBlock - Remove basic block BB's frontier. 387 void removeBlock(BasicBlock *BB) { 388 assert(find(BB) != end() && "Block is not in DominanceFrontier!"); 389 for (iterator I = begin(), E = end(); I != E; ++I) 390 I->second.erase(BB); 391 Frontiers.erase(BB); 392 } 393 394 void addToFrontier(iterator I, BasicBlock *Node) { 395 assert(I != end() && "BB is not in DominanceFrontier!"); 396 I->second.insert(Node); 397 } 398 399 void removeFromFrontier(iterator I, BasicBlock *Node) { 400 assert(I != end() && "BB is not in DominanceFrontier!"); 401 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB"); 402 I->second.erase(Node); 403 } 404 405 /// print - Convert to human readable form 406 /// 407 virtual void print(std::ostream &OS, const Module* = 0) const; 408 void print(std::ostream *OS, const Module* M = 0) const { 409 if (OS) print(*OS, M); 410 } 411 virtual void dump(); 412}; 413 414 415//===------------------------------------- 416/// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is 417/// used to compute a forward dominator frontiers. 418/// 419class DominanceFrontier : public DominanceFrontierBase { 420public: 421 static char ID; // Pass ID, replacement for typeid 422 DominanceFrontier() : 423 DominanceFrontierBase(intptr_t(&ID), false) {} 424 425 BasicBlock *getRoot() const { 426 assert(Roots.size() == 1 && "Should always have entry node!"); 427 return Roots[0]; 428 } 429 430 virtual bool runOnFunction(Function &) { 431 Frontiers.clear(); 432 DominatorTree &DT = getAnalysis<DominatorTree>(); 433 Roots = DT.getRoots(); 434 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!"); 435 calculate(DT, DT[Roots[0]]); 436 return false; 437 } 438 439 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 440 AU.setPreservesAll(); 441 AU.addRequired<DominatorTree>(); 442 } 443 444 /// splitBlock - BB is split and now it has one successor. Update dominance 445 /// frontier to reflect this change. 446 void splitBlock(BasicBlock *BB); 447 448 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier 449 /// to reflect this change. 450 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB, 451 DominatorTree *DT) { 452 // NewBB is now dominating BB. Which means BB's dominance 453 // frontier is now part of NewBB's dominance frontier. However, BB 454 // itself is not member of NewBB's dominance frontier. 455 DominanceFrontier::iterator NewDFI = find(NewBB); 456 DominanceFrontier::iterator DFI = find(BB); 457 DominanceFrontier::DomSetType BBSet = DFI->second; 458 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(), 459 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) { 460 BasicBlock *DFMember = *BBSetI; 461 // Insert only if NewBB dominates DFMember. 462 if (!DT->dominates(NewBB, DFMember)) 463 NewDFI->second.insert(DFMember); 464 } 465 NewDFI->second.erase(BB); 466 } 467 468private: 469 const DomSetType &calculate(const DominatorTree &DT, 470 const DomTreeNode *Node); 471}; 472 473 474} // End llvm namespace 475 476#endif 477