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 bool dominatedBySlowTreeWalk(const DomTreeNode *A,
164 const DomTreeNode *B) const {
165 const DomTreeNode *IDom;
166 if (A == 0 || B == 0) return false;
167 while ((IDom = B->getIDom()) != 0 && IDom != A)
168 B = IDom; // Walk up the tree
172 void updateDFSNumbers();
174 /// dominates - Returns true iff this dominates N. Note that this is not a
175 /// constant time operation!
177 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
179 return true; // A node trivially dominates itself.
181 if (A == 0 || B == 0)
184 ETNode *NodeA = A->getETNode();
185 ETNode *NodeB = B->getETNode();
188 return NodeB->DominatedBy(NodeA);
190 // If we end up with too many slow queries, just update the
191 // DFS numbers on the theory that we are going to keep querying.
193 if (SlowQueries > 32) {
195 return NodeB->DominatedBy(NodeA);
197 //return NodeB->DominatedBySlow(NodeA);
198 return dominatedBySlowTreeWalk(A, B);
201 inline bool dominates(BasicBlock *A, BasicBlock *B) {
205 return dominates(getNode(A), getNode(B));
208 //===--------------------------------------------------------------------===//
209 // API to update (Post)DominatorTree information based on modifications to
212 /// addNewBlock - Add a new node to the dominator tree information. This
213 /// creates a new node as a child of DomBB dominator node,linking it into
214 /// the children list of the immediate dominator.
215 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
216 assert(getNode(BB) == 0 && "Block already in dominator tree!");
217 DomTreeNode *IDomNode = getNode(DomBB);
218 assert(IDomNode && "Not immediate dominator specified for block!");
219 DFSInfoValid = false;
220 ETNode *E = new ETNode(BB);
222 return DomTreeNodes[BB] =
223 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E));
226 /// changeImmediateDominator - This method is used to update the dominator
227 /// tree information when a node's immediate dominator changes.
229 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
230 assert(N && NewIDom && "Cannot change null node pointers!");
231 DFSInfoValid = false;
235 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
236 changeImmediateDominator(getNode(BB), getNode(NewBB));
239 /// removeNode - Removes a node from the dominator tree. Block must not
240 /// dominate any other blocks. Invalidates any node pointing to removed
242 void removeNode(BasicBlock *BB) {
243 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
244 DomTreeNodes.erase(BB);
247 /// print - Convert to human readable form
249 virtual void print(std::ostream &OS, const Module* = 0) const;
250 void print(std::ostream *OS, const Module* M = 0) const {
251 if (OS) print(*OS, M);
256 //===-------------------------------------
257 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
258 /// compute a normal dominator tree.
260 class DominatorTree : public DominatorTreeBase {
262 static char ID; // Pass ID, replacement for typeid
263 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {}
265 BasicBlock *getRoot() const {
266 assert(Roots.size() == 1 && "Should always have entry node!");
270 virtual bool runOnFunction(Function &F);
272 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
273 AU.setPreservesAll();
276 void calculate(Function& F);
277 DomTreeNode *getNodeForBlock(BasicBlock *BB);
278 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N);
279 void Compress(BasicBlock *V);
280 BasicBlock *Eval(BasicBlock *v);
281 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
282 inline BasicBlock *getIDom(BasicBlock *BB) const {
283 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB);
284 return I != IDoms.end() ? I->second : 0;
288 //===-------------------------------------
289 /// DominatorTree GraphTraits specialization so the DominatorTree can be
290 /// iterable by generic graph iterators.
292 template <> struct GraphTraits<DomTreeNode*> {
293 typedef DomTreeNode NodeType;
294 typedef NodeType::iterator ChildIteratorType;
296 static NodeType *getEntryNode(NodeType *N) {
299 static inline ChildIteratorType child_begin(NodeType* N) {
302 static inline ChildIteratorType child_end(NodeType* N) {
307 template <> struct GraphTraits<DominatorTree*>
308 : public GraphTraits<DomTreeNode*> {
309 static NodeType *getEntryNode(DominatorTree *DT) {
310 return DT->getRootNode();
315 //===-------------------------------------
316 /// ET-Forest Class - Class used to construct forwards and backwards
319 class ETForestBase : public DominatorBase {
321 ETForestBase(intptr_t ID, bool isPostDom)
322 : DominatorBase(ID, isPostDom), Nodes(),
323 DFSInfoValid(false), SlowQueries(0) {}
325 virtual void releaseMemory() { reset(); }
327 typedef std::map<BasicBlock*, ETNode*> ETMapType;
329 // FIXME : There is no need to make this interface public.
330 // Fix predicate simplifier.
331 void updateDFSNumbers();
333 /// dominates - Return true if A dominates B.
335 inline bool dominates(BasicBlock *A, BasicBlock *B) {
339 ETNode *NodeA = getNode(A);
340 ETNode *NodeB = getNode(B);
343 return NodeB->DominatedBy(NodeA);
345 // If we end up with too many slow queries, just update the
346 // DFS numbers on the theory that we are going to keep querying.
348 if (SlowQueries > 32) {
350 return NodeB->DominatedBy(NodeA);
352 return NodeB->DominatedBySlow(NodeA);
356 // dominates - Return true if A dominates B. This performs the
357 // special checks necessary if A and B are in the same basic block.
358 bool dominates(Instruction *A, Instruction *B);
360 /// properlyDominates - Return true if A dominates B and A != B.
362 bool properlyDominates(BasicBlock *A, BasicBlock *B) {
363 return dominates(A, B) && A != B;
366 /// isReachableFromEntry - Return true if A is dominated by the entry
367 /// block of the function containing it.
368 const bool isReachableFromEntry(BasicBlock* A);
370 /// Return the nearest common dominator of A and B.
371 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const {
372 ETNode *NodeA = getNode(A);
373 ETNode *NodeB = getNode(B);
375 ETNode *Common = NodeA->NCA(NodeB);
378 return Common->getData<BasicBlock>();
381 /// Return the immediate dominator of A.
382 BasicBlock *getIDom(BasicBlock *A) const {
383 ETNode *NodeA = getNode(A);
384 if (!NodeA) return 0;
385 const ETNode *idom = NodeA->getFather();
386 return idom ? idom->getData<BasicBlock>() : 0;
389 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const {
390 ETNode *NodeA = getNode(A);
392 const ETNode* son = NodeA->getSon();
395 children.push_back(son->getData<BasicBlock>());
397 const ETNode* brother = son->getBrother();
398 while (brother != son) {
399 children.push_back(brother->getData<BasicBlock>());
400 brother = brother->getBrother();
404 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
405 AU.setPreservesAll();
406 AU.addRequired<DominatorTree>();
408 //===--------------------------------------------------------------------===//
409 // API to update Forest information based on modifications
412 /// addNewBlock - Add a new block to the CFG, with the specified immediate
415 void addNewBlock(BasicBlock *BB, BasicBlock *IDom);
417 /// setImmediateDominator - Update the immediate dominator information to
418 /// change the current immediate dominator for the specified block
419 /// to another block. This method requires that BB for NewIDom
420 /// already have an ETNode, otherwise just use addNewBlock.
422 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom);
423 /// print - Convert to human readable form
425 virtual void print(std::ostream &OS, const Module* = 0) const;
426 void print(std::ostream *OS, const Module* M = 0) const {
427 if (OS) print(*OS, M);
431 /// getNode - return the (Post)DominatorTree node for the specified basic
432 /// block. This is the same as using operator[] on this class.
434 inline ETNode *getNode(BasicBlock *BB) const {
435 ETMapType::const_iterator i = Nodes.find(BB);
436 return (i != Nodes.end()) ? i->second : 0;
439 inline ETNode *operator[](BasicBlock *BB) const {
446 unsigned int SlowQueries;
450 //==-------------------------------------
451 /// ETForest Class - Concrete subclass of ETForestBase that is used to
452 /// compute a forwards ET-Forest.
454 class ETForest : public ETForestBase {
456 static char ID; // Pass identification, replacement for typeid
458 ETForest() : ETForestBase((intptr_t)&ID, false) {}
460 BasicBlock *getRoot() const {
461 assert(Roots.size() == 1 && "Should always have entry node!");
465 virtual bool runOnFunction(Function &F) {
466 reset(); // Reset from the last time we were run...
467 DominatorTree &DT = getAnalysis<DominatorTree>();
468 Roots = DT.getRoots();
473 void calculate(const DominatorTree &DT);
474 // FIXME : There is no need to make getNodeForBlock public. Fix
475 // predicate simplifier.
476 ETNode *getNodeForBlock(BasicBlock *BB);
479 //===----------------------------------------------------------------------===//
480 /// DominanceFrontierBase - Common base class for computing forward and inverse
481 /// dominance frontiers for a function.
483 class DominanceFrontierBase : public DominatorBase {
485 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
486 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
488 DomSetMapType Frontiers;
490 DominanceFrontierBase(intptr_t ID, bool isPostDom)
491 : DominatorBase(ID, isPostDom) {}
493 virtual void releaseMemory() { Frontiers.clear(); }
495 // Accessor interface:
496 typedef DomSetMapType::iterator iterator;
497 typedef DomSetMapType::const_iterator const_iterator;
498 iterator begin() { return Frontiers.begin(); }
499 const_iterator begin() const { return Frontiers.begin(); }
500 iterator end() { return Frontiers.end(); }
501 const_iterator end() const { return Frontiers.end(); }
502 iterator find(BasicBlock *B) { return Frontiers.find(B); }
503 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
505 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
506 assert(find(BB) == end() && "Block already in DominanceFrontier!");
507 Frontiers.insert(std::make_pair(BB, frontier));
510 void addToFrontier(iterator I, BasicBlock *Node) {
511 assert(I != end() && "BB is not in DominanceFrontier!");
512 I->second.insert(Node);
515 void removeFromFrontier(iterator I, BasicBlock *Node) {
516 assert(I != end() && "BB is not in DominanceFrontier!");
517 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
518 I->second.erase(Node);
521 /// print - Convert to human readable form
523 virtual void print(std::ostream &OS, const Module* = 0) const;
524 void print(std::ostream *OS, const Module* M = 0) const {
525 if (OS) print(*OS, M);
531 //===-------------------------------------
532 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
533 /// used to compute a forward dominator frontiers.
535 class DominanceFrontier : public DominanceFrontierBase {
537 static char ID; // Pass ID, replacement for typeid
538 DominanceFrontier() :
539 DominanceFrontierBase((intptr_t)& ID, false) {}
541 BasicBlock *getRoot() const {
542 assert(Roots.size() == 1 && "Should always have entry node!");
546 virtual bool runOnFunction(Function &) {
548 DominatorTree &DT = getAnalysis<DominatorTree>();
549 Roots = DT.getRoots();
550 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
551 calculate(DT, DT[Roots[0]]);
555 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
556 AU.setPreservesAll();
557 AU.addRequired<DominatorTree>();
561 const DomSetType &calculate(const DominatorTree &DT,
562 const DomTreeNode *Node);
566 } // End llvm namespace