1 //===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
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
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.
21 //===----------------------------------------------------------------------===//
23 #ifndef LLVM_ANALYSIS_DOMINATORS_H
24 #define LLVM_ANALYSIS_DOMINATORS_H
26 #include "llvm/Analysis/ET-Forest.h"
27 #include "llvm/Pass.h"
34 template <typename GraphType> struct GraphTraits;
36 //===----------------------------------------------------------------------===//
37 /// DominatorBase - Base class that other, more interesting dominator analyses
40 class DominatorBase : public FunctionPass {
42 std::vector<BasicBlock*> Roots;
43 const bool IsPostDominators;
44 inline DominatorBase(intptr_t ID, bool isPostDom) :
45 FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {}
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).
52 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
54 /// isPostDominator - Returns true if analysis based of postdoms
56 bool isPostDominator() const { return IsPostDominators; }
60 //===----------------------------------------------------------------------===//
61 // DomTreeNode - Dominator Tree Node
67 std::vector<DomTreeNode*> Children;
69 typedef std::vector<DomTreeNode*>::iterator iterator;
70 typedef std::vector<DomTreeNode*>::const_iterator const_iterator;
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(); }
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; }
82 inline DomTreeNode(BasicBlock *BB, DomTreeNode *iDom, ETNode *E)
83 : TheBB(BB), IDom(iDom), ETN(E) {
85 ETN->setFather(IDom->getETNode());
87 inline DomTreeNode *addChild(DomTreeNode *C) { Children.push_back(C); return C; }
88 void setIDom(DomTreeNode *NewIDom);
91 //===----------------------------------------------------------------------===//
92 /// DominatorTree - Calculate the immediate dominator tree for a function.
94 class DominatorTreeBase : public DominatorBase {
98 typedef std::map<BasicBlock*, DomTreeNode*> DomTreeNodeMapType;
99 DomTreeNodeMapType DomTreeNodes;
100 DomTreeNode *RootNode;
102 typedef std::map<BasicBlock*, ETNode*> ETMapType;
106 unsigned int SlowQueries;
107 // Information record used during immediate dominators computation.
111 BasicBlock *Label, *Parent, *Child, *Ancestor;
113 std::vector<BasicBlock*> Bucket;
115 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){}
118 std::map<BasicBlock*, BasicBlock*> IDoms;
120 // Vertex - Map the DFS number to the BasicBlock*
121 std::vector<BasicBlock*> Vertex;
123 // Info - Collection of information used during the computation of idoms.
124 std::map<BasicBlock*, InfoRec> Info;
127 DominatorTreeBase(intptr_t ID, bool isPostDom)
128 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {}
129 ~DominatorTreeBase() { reset(); }
131 virtual void releaseMemory() { reset(); }
133 /// getNode - return the (Post)DominatorTree node for the specified basic
134 /// block. This is the same as using operator[] on this class.
136 inline DomTreeNode *getNode(BasicBlock *BB) const {
137 DomTreeNodeMapType::const_iterator i = DomTreeNodes.find(BB);
138 return (i != DomTreeNodes.end()) ? i->second : 0;
141 inline DomTreeNode *operator[](BasicBlock *BB) const {
145 /// getIDomBlock - return basic block BB's immediate domiantor basic block.
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();
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
162 DomTreeNode *getRootNode() { return RootNode; }
163 const DomTreeNode *getRootNode() const { return RootNode; }
165 /// properlyDominates - Returns true iff this dominates N and this != N.
166 /// Note that this is not a constant time operation!
168 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const {
169 if (A == 0 || B == 0) return false;
170 return dominatedBySlowTreeWalk(A, B);
173 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) {
174 return properlyDominates(getNode(A), getNode(B));
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
186 void updateDFSNumbers();
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();
193 ETNode *Common = NodeA->NCA(NodeB);
196 return Common->getData<BasicBlock>();
199 /// dominates - Returns true iff this dominates N. Note that this is not a
200 /// constant time operation!
202 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
204 return true; // A node trivially dominates itself.
206 if (A == 0 || B == 0)
209 ETNode *NodeA = A->getETNode();
210 ETNode *NodeB = B->getETNode();
213 return NodeB->DominatedBy(NodeA);
215 // If we end up with too many slow queries, just update the
216 // DFS numbers on the theory that we are going to keep querying.
218 if (SlowQueries > 32) {
220 return NodeB->DominatedBy(NodeA);
222 //return NodeB->DominatedBySlow(NodeA);
223 return dominatedBySlowTreeWalk(A, B);
226 inline bool dominates(BasicBlock *A, BasicBlock *B) {
230 return dominates(getNode(A), getNode(B));
233 // dominates - Return true if A dominates B. This performs the
234 // special checks necessary if A and B are in the same basic block.
235 bool dominates(Instruction *A, Instruction *B);
237 //===--------------------------------------------------------------------===//
238 // API to update (Post)DominatorTree information based on modifications to
241 /// addNewBlock - Add a new node to the dominator tree information. This
242 /// creates a new node as a child of DomBB dominator node,linking it into
243 /// the children list of the immediate dominator.
244 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
245 assert(getNode(BB) == 0 && "Block already in dominator tree!");
246 DomTreeNode *IDomNode = getNode(DomBB);
247 assert(IDomNode && "Not immediate dominator specified for block!");
248 DFSInfoValid = false;
249 ETNode *E = new ETNode(BB);
251 return DomTreeNodes[BB] =
252 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E));
255 /// changeImmediateDominator - This method is used to update the dominator
256 /// tree information when a node's immediate dominator changes.
258 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
259 assert(N && NewIDom && "Cannot change null node pointers!");
260 DFSInfoValid = false;
264 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
265 changeImmediateDominator(getNode(BB), getNode(NewBB));
268 /// removeNode - Removes a node from the dominator tree. Block must not
269 /// dominate any other blocks. Invalidates any node pointing to removed
271 void removeNode(BasicBlock *BB) {
272 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
273 DomTreeNodes.erase(BB);
276 /// print - Convert to human readable form
278 virtual void print(std::ostream &OS, const Module* = 0) const;
279 void print(std::ostream *OS, const Module* M = 0) const {
280 if (OS) print(*OS, M);
285 //===-------------------------------------
286 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
287 /// compute a normal dominator tree.
289 class DominatorTree : public DominatorTreeBase {
291 static char ID; // Pass ID, replacement for typeid
292 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {}
294 BasicBlock *getRoot() const {
295 assert(Roots.size() == 1 && "Should always have entry node!");
299 virtual bool runOnFunction(Function &F);
301 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
302 AU.setPreservesAll();
305 void calculate(Function& F);
306 DomTreeNode *getNodeForBlock(BasicBlock *BB);
307 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N);
308 void Compress(BasicBlock *V);
309 BasicBlock *Eval(BasicBlock *v);
310 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
311 inline BasicBlock *getIDom(BasicBlock *BB) const {
312 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB);
313 return I != IDoms.end() ? I->second : 0;
317 //===-------------------------------------
318 /// DominatorTree GraphTraits specialization so the DominatorTree can be
319 /// iterable by generic graph iterators.
321 template <> struct GraphTraits<DomTreeNode*> {
322 typedef DomTreeNode NodeType;
323 typedef NodeType::iterator ChildIteratorType;
325 static NodeType *getEntryNode(NodeType *N) {
328 static inline ChildIteratorType child_begin(NodeType* N) {
331 static inline ChildIteratorType child_end(NodeType* N) {
336 template <> struct GraphTraits<DominatorTree*>
337 : public GraphTraits<DomTreeNode*> {
338 static NodeType *getEntryNode(DominatorTree *DT) {
339 return DT->getRootNode();
344 //===-------------------------------------
345 /// ET-Forest Class - Class used to construct forwards and backwards
348 class ETForestBase : public DominatorBase {
350 ETForestBase(intptr_t ID, bool isPostDom)
351 : DominatorBase(ID, isPostDom), Nodes(),
352 DFSInfoValid(false), SlowQueries(0) {}
354 virtual void releaseMemory() { reset(); }
356 typedef std::map<BasicBlock*, ETNode*> ETMapType;
358 // FIXME : There is no need to make this interface public.
359 // Fix predicate simplifier.
360 void updateDFSNumbers();
362 /// dominates - Return true if A dominates B.
364 inline bool dominates(BasicBlock *A, BasicBlock *B) {
368 ETNode *NodeA = getNode(A);
369 ETNode *NodeB = getNode(B);
372 return NodeB->DominatedBy(NodeA);
374 // If we end up with too many slow queries, just update the
375 // DFS numbers on the theory that we are going to keep querying.
377 if (SlowQueries > 32) {
379 return NodeB->DominatedBy(NodeA);
381 return NodeB->DominatedBySlow(NodeA);
385 // dominates - Return true if A dominates B. This performs the
386 // special checks necessary if A and B are in the same basic block.
387 bool dominates(Instruction *A, Instruction *B);
389 /// properlyDominates - Return true if A dominates B and A != B.
391 bool properlyDominates(BasicBlock *A, BasicBlock *B) {
392 return dominates(A, B) && A != B;
395 /// isReachableFromEntry - Return true if A is dominated by the entry
396 /// block of the function containing it.
397 const bool isReachableFromEntry(BasicBlock* A);
399 /// Return the nearest common dominator of A and B.
400 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const {
401 ETNode *NodeA = getNode(A);
402 ETNode *NodeB = getNode(B);
404 ETNode *Common = NodeA->NCA(NodeB);
407 return Common->getData<BasicBlock>();
410 /// Return the immediate dominator of A.
411 BasicBlock *getIDom(BasicBlock *A) const {
412 ETNode *NodeA = getNode(A);
413 if (!NodeA) return 0;
414 const ETNode *idom = NodeA->getFather();
415 return idom ? idom->getData<BasicBlock>() : 0;
418 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const {
419 ETNode *NodeA = getNode(A);
421 const ETNode* son = NodeA->getSon();
424 children.push_back(son->getData<BasicBlock>());
426 const ETNode* brother = son->getBrother();
427 while (brother != son) {
428 children.push_back(brother->getData<BasicBlock>());
429 brother = brother->getBrother();
433 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
434 AU.setPreservesAll();
435 AU.addRequired<DominatorTree>();
437 //===--------------------------------------------------------------------===//
438 // API to update Forest information based on modifications
441 /// addNewBlock - Add a new block to the CFG, with the specified immediate
444 void addNewBlock(BasicBlock *BB, BasicBlock *IDom);
446 /// setImmediateDominator - Update the immediate dominator information to
447 /// change the current immediate dominator for the specified block
448 /// to another block. This method requires that BB for NewIDom
449 /// already have an ETNode, otherwise just use addNewBlock.
451 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom);
452 /// print - Convert to human readable form
454 virtual void print(std::ostream &OS, const Module* = 0) const;
455 void print(std::ostream *OS, const Module* M = 0) const {
456 if (OS) print(*OS, M);
460 /// getNode - return the (Post)DominatorTree node for the specified basic
461 /// block. This is the same as using operator[] on this class.
463 inline ETNode *getNode(BasicBlock *BB) const {
464 ETMapType::const_iterator i = Nodes.find(BB);
465 return (i != Nodes.end()) ? i->second : 0;
468 inline ETNode *operator[](BasicBlock *BB) const {
475 unsigned int SlowQueries;
479 //==-------------------------------------
480 /// ETForest Class - Concrete subclass of ETForestBase that is used to
481 /// compute a forwards ET-Forest.
483 class ETForest : public ETForestBase {
485 static char ID; // Pass identification, replacement for typeid
487 ETForest() : ETForestBase((intptr_t)&ID, false) {}
489 BasicBlock *getRoot() const {
490 assert(Roots.size() == 1 && "Should always have entry node!");
494 virtual bool runOnFunction(Function &F) {
495 reset(); // Reset from the last time we were run...
496 DominatorTree &DT = getAnalysis<DominatorTree>();
497 Roots = DT.getRoots();
502 void calculate(const DominatorTree &DT);
503 // FIXME : There is no need to make getNodeForBlock public. Fix
504 // predicate simplifier.
505 ETNode *getNodeForBlock(BasicBlock *BB);
508 //===----------------------------------------------------------------------===//
509 /// DominanceFrontierBase - Common base class for computing forward and inverse
510 /// dominance frontiers for a function.
512 class DominanceFrontierBase : public DominatorBase {
514 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
515 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
517 DomSetMapType Frontiers;
519 DominanceFrontierBase(intptr_t ID, bool isPostDom)
520 : DominatorBase(ID, isPostDom) {}
522 virtual void releaseMemory() { Frontiers.clear(); }
524 // Accessor interface:
525 typedef DomSetMapType::iterator iterator;
526 typedef DomSetMapType::const_iterator const_iterator;
527 iterator begin() { return Frontiers.begin(); }
528 const_iterator begin() const { return Frontiers.begin(); }
529 iterator end() { return Frontiers.end(); }
530 const_iterator end() const { return Frontiers.end(); }
531 iterator find(BasicBlock *B) { return Frontiers.find(B); }
532 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
534 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
535 assert(find(BB) == end() && "Block already in DominanceFrontier!");
536 Frontiers.insert(std::make_pair(BB, frontier));
539 void addToFrontier(iterator I, BasicBlock *Node) {
540 assert(I != end() && "BB is not in DominanceFrontier!");
541 I->second.insert(Node);
544 void removeFromFrontier(iterator I, BasicBlock *Node) {
545 assert(I != end() && "BB is not in DominanceFrontier!");
546 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
547 I->second.erase(Node);
550 /// print - Convert to human readable form
552 virtual void print(std::ostream &OS, const Module* = 0) const;
553 void print(std::ostream *OS, const Module* M = 0) const {
554 if (OS) print(*OS, M);
560 //===-------------------------------------
561 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
562 /// used to compute a forward dominator frontiers.
564 class DominanceFrontier : public DominanceFrontierBase {
566 static char ID; // Pass ID, replacement for typeid
567 DominanceFrontier() :
568 DominanceFrontierBase((intptr_t)& ID, false) {}
570 BasicBlock *getRoot() const {
571 assert(Roots.size() == 1 && "Should always have entry node!");
575 virtual bool runOnFunction(Function &) {
577 DominatorTree &DT = getAnalysis<DominatorTree>();
578 Roots = DT.getRoots();
579 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
580 calculate(DT, DT[Roots[0]]);
584 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
585 AU.setPreservesAll();
586 AU.addRequired<DominatorTree>();
590 const DomSetType &calculate(const DominatorTree &DT,
591 const DomTreeNode *Node);
595 } // End llvm namespace