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();
173 /// dominates - Returns true iff this dominates N. Note that this is not a
174 /// constant time operation!
176 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
177 if (B == A) return true; // A node trivially dominates itself.
179 ETNode *NodeA = A->getETNode();
180 ETNode *NodeB = B->getETNode();
183 return NodeB->DominatedBy(NodeA);
185 // If we end up with too many slow queries, just update the
186 // DFS numbers on the theory that we are going to keep querying.
188 if (SlowQueries > 32) {
190 return NodeB->DominatedBy(NodeA);
192 //return NodeB->DominatedBySlow(NodeA);
193 return dominatedBySlowTreeWalk(A, B);
196 //===--------------------------------------------------------------------===//
197 // API to update (Post)DominatorTree information based on modifications to
200 /// addNewBlock - Add a new node to the dominator tree information. This
201 /// creates a new node as a child of DomBB dominator node,linking it into
202 /// the children list of the immediate dominator.
203 DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
204 assert(getNode(BB) == 0 && "Block already in dominator tree!");
205 DomTreeNode *IDomNode = getNode(DomBB);
206 assert(IDomNode && "Not immediate dominator specified for block!");
207 DFSInfoValid = false;
208 ETNode *E = new ETNode(BB);
210 return DomTreeNodes[BB] =
211 IDomNode->addChild(new DomTreeNode(BB, IDomNode, E));
214 /// changeImmediateDominator - This method is used to update the dominator
215 /// tree information when a node's immediate dominator changes.
217 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
218 assert(N && NewIDom && "Cannot change null node pointers!");
219 DFSInfoValid = false;
223 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
224 changeImmediateDominator(getNode(BB), getNode(NewBB));
227 /// removeNode - Removes a node from the dominator tree. Block must not
228 /// dominate any other blocks. Invalidates any node pointing to removed
230 void removeNode(BasicBlock *BB) {
231 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
232 DomTreeNodes.erase(BB);
235 /// print - Convert to human readable form
237 virtual void print(std::ostream &OS, const Module* = 0) const;
238 void print(std::ostream *OS, const Module* M = 0) const {
239 if (OS) print(*OS, M);
244 //===-------------------------------------
245 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
246 /// compute a normal dominator tree.
248 class DominatorTree : public DominatorTreeBase {
250 static char ID; // Pass ID, replacement for typeid
251 DominatorTree() : DominatorTreeBase((intptr_t)&ID, false) {}
253 BasicBlock *getRoot() const {
254 assert(Roots.size() == 1 && "Should always have entry node!");
258 virtual bool runOnFunction(Function &F);
260 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
261 AU.setPreservesAll();
264 void calculate(Function& F);
265 DomTreeNode *getNodeForBlock(BasicBlock *BB);
266 unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N);
267 void Compress(BasicBlock *V);
268 BasicBlock *Eval(BasicBlock *v);
269 void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
270 inline BasicBlock *getIDom(BasicBlock *BB) const {
271 std::map<BasicBlock*, BasicBlock*>::const_iterator I = IDoms.find(BB);
272 return I != IDoms.end() ? I->second : 0;
276 //===-------------------------------------
277 /// DominatorTree GraphTraits specialization so the DominatorTree can be
278 /// iterable by generic graph iterators.
280 template <> struct GraphTraits<DomTreeNode*> {
281 typedef DomTreeNode NodeType;
282 typedef NodeType::iterator ChildIteratorType;
284 static NodeType *getEntryNode(NodeType *N) {
287 static inline ChildIteratorType child_begin(NodeType* N) {
290 static inline ChildIteratorType child_end(NodeType* N) {
295 template <> struct GraphTraits<DominatorTree*>
296 : public GraphTraits<DomTreeNode*> {
297 static NodeType *getEntryNode(DominatorTree *DT) {
298 return DT->getRootNode();
303 //===-------------------------------------
304 /// ET-Forest Class - Class used to construct forwards and backwards
307 class ETForestBase : public DominatorBase {
309 ETForestBase(intptr_t ID, bool isPostDom)
310 : DominatorBase(ID, isPostDom), Nodes(),
311 DFSInfoValid(false), SlowQueries(0) {}
313 virtual void releaseMemory() { reset(); }
315 typedef std::map<BasicBlock*, ETNode*> ETMapType;
317 // FIXME : There is no need to make this interface public.
318 // Fix predicate simplifier.
319 void updateDFSNumbers();
321 /// dominates - Return true if A dominates B.
323 inline bool dominates(BasicBlock *A, BasicBlock *B) {
327 ETNode *NodeA = getNode(A);
328 ETNode *NodeB = getNode(B);
331 return NodeB->DominatedBy(NodeA);
333 // If we end up with too many slow queries, just update the
334 // DFS numbers on the theory that we are going to keep querying.
336 if (SlowQueries > 32) {
338 return NodeB->DominatedBy(NodeA);
340 return NodeB->DominatedBySlow(NodeA);
344 // dominates - Return true if A dominates B. This performs the
345 // special checks necessary if A and B are in the same basic block.
346 bool dominates(Instruction *A, Instruction *B);
348 /// properlyDominates - Return true if A dominates B and A != B.
350 bool properlyDominates(BasicBlock *A, BasicBlock *B) {
351 return dominates(A, B) && A != B;
354 /// isReachableFromEntry - Return true if A is dominated by the entry
355 /// block of the function containing it.
356 const bool isReachableFromEntry(BasicBlock* A);
358 /// Return the nearest common dominator of A and B.
359 BasicBlock *nearestCommonDominator(BasicBlock *A, BasicBlock *B) const {
360 ETNode *NodeA = getNode(A);
361 ETNode *NodeB = getNode(B);
363 ETNode *Common = NodeA->NCA(NodeB);
366 return Common->getData<BasicBlock>();
369 /// Return the immediate dominator of A.
370 BasicBlock *getIDom(BasicBlock *A) const {
371 ETNode *NodeA = getNode(A);
372 if (!NodeA) return 0;
373 const ETNode *idom = NodeA->getFather();
374 return idom ? idom->getData<BasicBlock>() : 0;
377 void getETNodeChildren(BasicBlock *A, std::vector<BasicBlock*>& children) const {
378 ETNode *NodeA = getNode(A);
380 const ETNode* son = NodeA->getSon();
383 children.push_back(son->getData<BasicBlock>());
385 const ETNode* brother = son->getBrother();
386 while (brother != son) {
387 children.push_back(brother->getData<BasicBlock>());
388 brother = brother->getBrother();
392 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
393 AU.setPreservesAll();
394 AU.addRequired<DominatorTree>();
396 //===--------------------------------------------------------------------===//
397 // API to update Forest information based on modifications
400 /// addNewBlock - Add a new block to the CFG, with the specified immediate
403 void addNewBlock(BasicBlock *BB, BasicBlock *IDom);
405 /// setImmediateDominator - Update the immediate dominator information to
406 /// change the current immediate dominator for the specified block
407 /// to another block. This method requires that BB for NewIDom
408 /// already have an ETNode, otherwise just use addNewBlock.
410 void setImmediateDominator(BasicBlock *BB, BasicBlock *NewIDom);
411 /// print - Convert to human readable form
413 virtual void print(std::ostream &OS, const Module* = 0) const;
414 void print(std::ostream *OS, const Module* M = 0) const {
415 if (OS) print(*OS, M);
419 /// getNode - return the (Post)DominatorTree node for the specified basic
420 /// block. This is the same as using operator[] on this class.
422 inline ETNode *getNode(BasicBlock *BB) const {
423 ETMapType::const_iterator i = Nodes.find(BB);
424 return (i != Nodes.end()) ? i->second : 0;
427 inline ETNode *operator[](BasicBlock *BB) const {
434 unsigned int SlowQueries;
438 //==-------------------------------------
439 /// ETForest Class - Concrete subclass of ETForestBase that is used to
440 /// compute a forwards ET-Forest.
442 class ETForest : public ETForestBase {
444 static char ID; // Pass identification, replacement for typeid
446 ETForest() : ETForestBase((intptr_t)&ID, false) {}
448 BasicBlock *getRoot() const {
449 assert(Roots.size() == 1 && "Should always have entry node!");
453 virtual bool runOnFunction(Function &F) {
454 reset(); // Reset from the last time we were run...
455 DominatorTree &DT = getAnalysis<DominatorTree>();
456 Roots = DT.getRoots();
461 void calculate(const DominatorTree &DT);
462 // FIXME : There is no need to make getNodeForBlock public. Fix
463 // predicate simplifier.
464 ETNode *getNodeForBlock(BasicBlock *BB);
467 //===----------------------------------------------------------------------===//
468 /// DominanceFrontierBase - Common base class for computing forward and inverse
469 /// dominance frontiers for a function.
471 class DominanceFrontierBase : public DominatorBase {
473 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
474 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
476 DomSetMapType Frontiers;
478 DominanceFrontierBase(intptr_t ID, bool isPostDom)
479 : DominatorBase(ID, isPostDom) {}
481 virtual void releaseMemory() { Frontiers.clear(); }
483 // Accessor interface:
484 typedef DomSetMapType::iterator iterator;
485 typedef DomSetMapType::const_iterator const_iterator;
486 iterator begin() { return Frontiers.begin(); }
487 const_iterator begin() const { return Frontiers.begin(); }
488 iterator end() { return Frontiers.end(); }
489 const_iterator end() const { return Frontiers.end(); }
490 iterator find(BasicBlock *B) { return Frontiers.find(B); }
491 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
493 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
494 assert(find(BB) == end() && "Block already in DominanceFrontier!");
495 Frontiers.insert(std::make_pair(BB, frontier));
498 void addToFrontier(iterator I, BasicBlock *Node) {
499 assert(I != end() && "BB is not in DominanceFrontier!");
500 I->second.insert(Node);
503 void removeFromFrontier(iterator I, BasicBlock *Node) {
504 assert(I != end() && "BB is not in DominanceFrontier!");
505 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
506 I->second.erase(Node);
509 /// print - Convert to human readable form
511 virtual void print(std::ostream &OS, const Module* = 0) const;
512 void print(std::ostream *OS, const Module* M = 0) const {
513 if (OS) print(*OS, M);
519 //===-------------------------------------
520 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
521 /// used to compute a forward dominator frontiers.
523 class DominanceFrontier : public DominanceFrontierBase {
525 static char ID; // Pass ID, replacement for typeid
526 DominanceFrontier() :
527 DominanceFrontierBase((intptr_t)& ID, false) {}
529 BasicBlock *getRoot() const {
530 assert(Roots.size() == 1 && "Should always have entry node!");
534 virtual bool runOnFunction(Function &) {
536 DominatorTree &DT = getAnalysis<DominatorTree>();
537 Roots = DT.getRoots();
538 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
539 calculate(DT, DT[Roots[0]]);
543 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
544 AU.setPreservesAll();
545 AU.addRequired<DominatorTree>();
549 const DomSetType &calculate(const DominatorTree &DT,
550 const DomTreeNode *Node);
554 } // End llvm namespace