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 /// getRootNode - This returns the entry node for the CFG of the function. If
146 /// this tree represents the post-dominance relations for a function, however,
147 /// this root may be a node with the block == NULL. This is the case when
148 /// there are multiple exit nodes from a particular function. Consumers of
149 /// post-dominance information must be capable of dealing with this
152 DomTreeNode *getRootNode() { return RootNode; }
153 const DomTreeNode *getRootNode() const { return RootNode; }
155 /// properlyDominates - Returns true iff this dominates N and this != N.
156 /// Note that this is not a constant time operation!
158 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const {
159 if (A == 0 || B == 0) return false;
160 return dominatedBySlowTreeWalk(A, B);
163 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) {
164 return properlyDominates(getNode(A), getNode(B));
167 bool dominatedBySlowTreeWalk(const DomTreeNode *A,
168 const DomTreeNode *B) const {
169 const DomTreeNode *IDom;
170 if (A == 0 || B == 0) return false;
171 while ((IDom = B->getIDom()) != 0 && IDom != A)
172 B = IDom; // Walk up the tree
176 void updateDFSNumbers();
178 /// dominates - Returns true iff this dominates N. Note that this is not a
179 /// constant time operation!
181 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
183 return true; // A node trivially dominates itself.
185 if (A == 0 || B == 0)
188 ETNode *NodeA = A->getETNode();
189 ETNode *NodeB = B->getETNode();
192 return NodeB->DominatedBy(NodeA);
194 // If we end up with too many slow queries, just update the
195 // DFS numbers on the theory that we are going to keep querying.
197 if (SlowQueries > 32) {
199 return NodeB->DominatedBy(NodeA);
201 //return NodeB->DominatedBySlow(NodeA);
202 return dominatedBySlowTreeWalk(A, B);
205 inline bool dominates(BasicBlock *A, BasicBlock *B) {
209 return dominates(getNode(A), getNode(B));
212 //===--------------------------------------------------------------------===//
213 // API to update (Post)DominatorTree information based on modifications to
216 /// addNewBlock - Add a new node to the dominator tree information. This
217 /// creates a new node as a child of DomBB dominator node,linking it into
218 /// the children list of the immediate dominator.
219 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
220 assert(getNode(BB) == 0 && "Block already in dominator tree!");
221 DomTreeNode *IDomNode = getNode(DomBB);
222 assert(IDomNode && "Not immediate dominator specified for block!");
223 DFSInfoValid = false;
224 ETNode *E = new ETNode(BB);
226 return DomTreeNodes[BB] =
227 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E));
230 /// changeImmediateDominator - This method is used to update the dominator
231 /// tree information when a node's immediate dominator changes.
233 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
234 assert(N && NewIDom && "Cannot change null node pointers!");
235 DFSInfoValid = false;
239 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
240 changeImmediateDominator(getNode(BB), getNode(NewBB));
243 /// removeNode - Removes a node from the dominator tree. Block must not
244 /// dominate any other blocks. Invalidates any node pointing to removed
246 void removeNode(BasicBlock *BB) {
247 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
248 DomTreeNodes.erase(BB);
251 /// print - Convert to human readable form
253 virtual void print(std::ostream &OS, const Module* = 0) const;
254 void print(std::ostream *OS, const Module* M = 0) const {
255 if (OS) print(*OS, M);
260 //===-------------------------------------
261 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
262 /// compute a normal dominator tree.
264 class DominatorTree : public DominatorTreeBase {
266 static char ID; // Pass ID, replacement for typeid
267 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {}
269 BasicBlock *getRoot() const {
270 assert(Roots.size() == 1 && "Should always have entry node!");
274 virtual bool runOnFunction(Function &F);
276 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
277 AU.setPreservesAll();
280 void calculate(Function& F);
281 DomTreeNode *getNodeForBlock(BasicBlock *BB);
282 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N);
283 void Compress(BasicBlock *V);
284 BasicBlock *Eval(BasicBlock *v);
285 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
286 inline BasicBlock *getIDom(BasicBlock *BB) const {
287 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB);
288 return I != IDoms.end() ? I->second : 0;
292 //===-------------------------------------
293 /// DominatorTree GraphTraits specialization so the DominatorTree can be
294 /// iterable by generic graph iterators.
296 template <> struct GraphTraits<DomTreeNode*> {
297 typedef DomTreeNode NodeType;
298 typedef NodeType::iterator ChildIteratorType;
300 static NodeType *getEntryNode(NodeType *N) {
303 static inline ChildIteratorType child_begin(NodeType* N) {
306 static inline ChildIteratorType child_end(NodeType* N) {
311 template <> struct GraphTraits<DominatorTree*>
312 : public GraphTraits<DomTreeNode*> {
313 static NodeType *getEntryNode(DominatorTree *DT) {
314 return DT->getRootNode();
319 //===-------------------------------------
320 /// ET-Forest Class - Class used to construct forwards and backwards
323 class ETForestBase : public DominatorBase {
325 ETForestBase(intptr_t ID, bool isPostDom)
326 : DominatorBase(ID, isPostDom), Nodes(),
327 DFSInfoValid(false), SlowQueries(0) {}
329 virtual void releaseMemory() { reset(); }
331 typedef std::map<BasicBlock*, ETNode*> ETMapType;
333 // FIXME : There is no need to make this interface public.
334 // Fix predicate simplifier.
335 void updateDFSNumbers();
337 /// dominates - Return true if A dominates B.
339 inline bool dominates(BasicBlock *A, BasicBlock *B) {
343 ETNode *NodeA = getNode(A);
344 ETNode *NodeB = getNode(B);
347 return NodeB->DominatedBy(NodeA);
349 // If we end up with too many slow queries, just update the
350 // DFS numbers on the theory that we are going to keep querying.
352 if (SlowQueries > 32) {
354 return NodeB->DominatedBy(NodeA);
356 return NodeB->DominatedBySlow(NodeA);
360 // dominates - Return true if A dominates B. This performs the
361 // special checks necessary if A and B are in the same basic block.
362 bool dominates(Instruction *A, Instruction *B);
364 /// properlyDominates - Return true if A dominates B and A != B.
366 bool properlyDominates(BasicBlock *A, BasicBlock *B) {
367 return dominates(A, B) && A != B;
370 /// isReachableFromEntry - Return true if A is dominated by the entry
371 /// block of the function containing it.
372 const bool isReachableFromEntry(BasicBlock* A);
374 /// Return the nearest common dominator of A and B.
375 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const {
376 ETNode *NodeA = getNode(A);
377 ETNode *NodeB = getNode(B);
379 ETNode *Common = NodeA->NCA(NodeB);
382 return Common->getData<BasicBlock>();
385 /// Return the immediate dominator of A.
386 BasicBlock *getIDom(BasicBlock *A) const {
387 ETNode *NodeA = getNode(A);
388 if (!NodeA) return 0;
389 const ETNode *idom = NodeA->getFather();
390 return idom ? idom->getData<BasicBlock>() : 0;
393 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const {
394 ETNode *NodeA = getNode(A);
396 const ETNode* son = NodeA->getSon();
399 children.push_back(son->getData<BasicBlock>());
401 const ETNode* brother = son->getBrother();
402 while (brother != son) {
403 children.push_back(brother->getData<BasicBlock>());
404 brother = brother->getBrother();
408 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
409 AU.setPreservesAll();
410 AU.addRequired<DominatorTree>();
412 //===--------------------------------------------------------------------===//
413 // API to update Forest information based on modifications
416 /// addNewBlock - Add a new block to the CFG, with the specified immediate
419 void addNewBlock(BasicBlock *BB, BasicBlock *IDom);
421 /// setImmediateDominator - Update the immediate dominator information to
422 /// change the current immediate dominator for the specified block
423 /// to another block. This method requires that BB for NewIDom
424 /// already have an ETNode, otherwise just use addNewBlock.
426 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom);
427 /// print - Convert to human readable form
429 virtual void print(std::ostream &OS, const Module* = 0) const;
430 void print(std::ostream *OS, const Module* M = 0) const {
431 if (OS) print(*OS, M);
435 /// getNode - return the (Post)DominatorTree node for the specified basic
436 /// block. This is the same as using operator[] on this class.
438 inline ETNode *getNode(BasicBlock *BB) const {
439 ETMapType::const_iterator i = Nodes.find(BB);
440 return (i != Nodes.end()) ? i->second : 0;
443 inline ETNode *operator[](BasicBlock *BB) const {
450 unsigned int SlowQueries;
454 //==-------------------------------------
455 /// ETForest Class - Concrete subclass of ETForestBase that is used to
456 /// compute a forwards ET-Forest.
458 class ETForest : public ETForestBase {
460 static char ID; // Pass identification, replacement for typeid
462 ETForest() : ETForestBase((intptr_t)&ID, false) {}
464 BasicBlock *getRoot() const {
465 assert(Roots.size() == 1 && "Should always have entry node!");
469 virtual bool runOnFunction(Function &F) {
470 reset(); // Reset from the last time we were run...
471 DominatorTree &DT = getAnalysis<DominatorTree>();
472 Roots = DT.getRoots();
477 void calculate(const DominatorTree &DT);
478 // FIXME : There is no need to make getNodeForBlock public. Fix
479 // predicate simplifier.
480 ETNode *getNodeForBlock(BasicBlock *BB);
483 //===----------------------------------------------------------------------===//
484 /// DominanceFrontierBase - Common base class for computing forward and inverse
485 /// dominance frontiers for a function.
487 class DominanceFrontierBase : public DominatorBase {
489 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
490 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
492 DomSetMapType Frontiers;
494 DominanceFrontierBase(intptr_t ID, bool isPostDom)
495 : DominatorBase(ID, isPostDom) {}
497 virtual void releaseMemory() { Frontiers.clear(); }
499 // Accessor interface:
500 typedef DomSetMapType::iterator iterator;
501 typedef DomSetMapType::const_iterator const_iterator;
502 iterator begin() { return Frontiers.begin(); }
503 const_iterator begin() const { return Frontiers.begin(); }
504 iterator end() { return Frontiers.end(); }
505 const_iterator end() const { return Frontiers.end(); }
506 iterator find(BasicBlock *B) { return Frontiers.find(B); }
507 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
509 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
510 assert(find(BB) == end() && "Block already in DominanceFrontier!");
511 Frontiers.insert(std::make_pair(BB, frontier));
514 void addToFrontier(iterator I, BasicBlock *Node) {
515 assert(I != end() && "BB is not in DominanceFrontier!");
516 I->second.insert(Node);
519 void removeFromFrontier(iterator I, BasicBlock *Node) {
520 assert(I != end() && "BB is not in DominanceFrontier!");
521 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
522 I->second.erase(Node);
525 /// print - Convert to human readable form
527 virtual void print(std::ostream &OS, const Module* = 0) const;
528 void print(std::ostream *OS, const Module* M = 0) const {
529 if (OS) print(*OS, M);
535 //===-------------------------------------
536 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
537 /// used to compute a forward dominator frontiers.
539 class DominanceFrontier : public DominanceFrontierBase {
541 static char ID; // Pass ID, replacement for typeid
542 DominanceFrontier() :
543 DominanceFrontierBase((intptr_t)& ID, false) {}
545 BasicBlock *getRoot() const {
546 assert(Roots.size() == 1 && "Should always have entry node!");
550 virtual bool runOnFunction(Function &) {
552 DominatorTree &DT = getAnalysis<DominatorTree>();
553 Roots = DT.getRoots();
554 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
555 calculate(DT, DT[Roots[0]]);
559 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
560 AU.setPreservesAll();
561 AU.addRequired<DominatorTree>();
565 const DomSetType &calculate(const DominatorTree &DT,
566 const DomTreeNode *Node);
570 } // End llvm namespace