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. DominanceFrontier: Calculate and hold the dominance frontier for a
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.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_ANALYSIS_DOMINATORS_H
22 #define LLVM_ANALYSIS_DOMINATORS_H
24 #include "llvm/Pass.h"
26 #include "llvm/ADT/DenseMap.h"
32 template <typename GraphType> struct GraphTraits;
34 //===----------------------------------------------------------------------===//
35 /// DominatorBase - Base class that other, more interesting dominator analyses
38 class DominatorBase : public FunctionPass {
40 std::vector<BasicBlock*> Roots;
41 const bool IsPostDominators;
42 inline DominatorBase(intptr_t ID, bool isPostDom) :
43 FunctionPass(ID), Roots(), IsPostDominators(isPostDom) {}
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).
50 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
52 /// isPostDominator - Returns true if analysis based of postdoms
54 bool isPostDominator() const { return IsPostDominators; }
58 //===----------------------------------------------------------------------===//
59 // DomTreeNode - Dominator Tree Node
60 class DominatorTreeBase;
61 class PostDominatorTree;
65 std::vector<DomTreeNode*> Children;
66 int DFSNumIn, DFSNumOut;
68 friend class DominatorTreeBase;
69 friend class PostDominatorTree;
71 typedef std::vector<DomTreeNode*>::iterator iterator;
72 typedef std::vector<DomTreeNode*>::const_iterator const_iterator;
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(); }
79 BasicBlock *getBlock() const { return TheBB; }
80 DomTreeNode *getIDom() const { return IDom; }
81 const std::vector<DomTreeNode*> &getChildren() const { return Children; }
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);
89 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
91 unsigned getDFSNumIn() const { return DFSNumIn; }
92 unsigned getDFSNumOut() const { return DFSNumOut; }
94 // Return true if this node is dominated by other. Use this only if DFS info
96 bool DominatedBy(const DomTreeNode *other) const {
97 return this->DFSNumIn >= other->DFSNumIn &&
98 this->DFSNumOut <= other->DFSNumOut;
102 //===----------------------------------------------------------------------===//
103 /// DominatorTree - Calculate the immediate dominator tree for a function.
105 class DominatorTreeBase : public DominatorBase {
108 typedef DenseMap<BasicBlock*, DomTreeNode*> DomTreeNodeMapType;
109 DomTreeNodeMapType DomTreeNodes;
110 DomTreeNode *RootNode;
113 unsigned int SlowQueries;
114 // Information record used during immediate dominators computation.
118 BasicBlock *Label, *Parent, *Child, *Ancestor;
120 std::vector<BasicBlock*> Bucket;
122 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0) {}
125 DenseMap<BasicBlock*, BasicBlock*> IDoms;
127 // Vertex - Map the DFS number to the BasicBlock*
128 std::vector<BasicBlock*> Vertex;
130 // Info - Collection of information used during the computation of idoms.
131 DenseMap<BasicBlock*, InfoRec> Info;
134 DominatorTreeBase(intptr_t ID, bool isPostDom)
135 : DominatorBase(ID, isPostDom), DFSInfoValid(false), SlowQueries(0) {}
136 ~DominatorTreeBase() { reset(); }
138 virtual void releaseMemory() { reset(); }
140 /// getNode - return the (Post)DominatorTree node for the specified basic
141 /// block. This is the same as using operator[] on this class.
143 inline DomTreeNode *getNode(BasicBlock *BB) const {
144 DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB);
145 return I != DomTreeNodes.end() ? I->second : 0;
148 inline DomTreeNode *operator[](BasicBlock *BB) const {
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
159 DomTreeNode *getRootNode() { return RootNode; }
160 const DomTreeNode *getRootNode() const { return RootNode; }
162 /// properlyDominates - Returns true iff this dominates N and this != N.
163 /// Note that this is not a constant time operation!
165 bool properlyDominates(const DomTreeNode *A, DomTreeNode *B) const {
166 if (A == 0 || B == 0) return false;
167 return dominatedBySlowTreeWalk(A, B);
170 inline bool properlyDominates(BasicBlock *A, BasicBlock *B) {
171 return properlyDominates(getNode(A), getNode(B));
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
184 /// isReachableFromEntry - Return true if A is dominated by the entry
185 /// block of the function containing it.
186 const bool isReachableFromEntry(BasicBlock* A);
188 /// dominates - Returns true iff A dominates B. Note that this is not a
189 /// constant time operation!
191 inline bool dominates(const DomTreeNode *A, DomTreeNode *B) {
193 return true; // A node trivially dominates itself.
195 if (A == 0 || B == 0)
199 return B->DominatedBy(A);
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.
204 if (SlowQueries > 32) {
206 return B->DominatedBy(A);
209 return dominatedBySlowTreeWalk(A, B);
212 inline bool dominates(BasicBlock *A, BasicBlock *B) {
216 return dominates(getNode(A), getNode(B));
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);
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);
227 //===--------------------------------------------------------------------===//
228 // API to update (Post)DominatorTree information based on modifications to
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));
243 /// changeImmediateDominator - This method is used to update the dominator
244 /// tree information when a node's immediate dominator changes.
246 void changeImmediateDominator(DomTreeNode *N, DomTreeNode *NewIDom) {
247 assert(N && NewIDom && "Cannot change null node pointers!");
248 DFSInfoValid = false;
252 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB) {
253 changeImmediateDominator(getNode(BB), getNode(NewBB));
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);
261 /// removeNode - Removes a node from the dominator tree. Block must not
262 /// dominate any other blocks. Invalidates any node pointing to removed
264 void removeNode(BasicBlock *BB) {
265 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
266 DomTreeNodes.erase(BB);
269 /// print - Convert to human readable form
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);
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);
283 template<class GraphT> friend unsigned DFSPass(DominatorTreeBase& DT,
284 typename GraphT::NodeType* V,
287 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
288 /// dominator tree in dfs order.
289 void updateDFSNumbers();
291 DomTreeNode *getNodeForBlock(BasicBlock *BB);
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;
299 //===-------------------------------------
300 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
301 /// compute a normal dominator tree.
303 class DominatorTree : public DominatorTreeBase {
305 static char ID; // Pass ID, replacement for typeid
306 DominatorTree() : DominatorTreeBase(intptr_t(&ID), false) {}
308 BasicBlock *getRoot() const {
309 assert(Roots.size() == 1 && "Should always have entry node!");
313 virtual bool runOnFunction(Function &F);
315 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
316 AU.setPreservesAll();
320 /// BB is split and now it has one successor. Update dominator tree to
321 /// reflect this change.
322 void splitBlock(BasicBlock *BB);
325 friend void DTcalculate(DominatorTree& DT, Function& F);
328 //===-------------------------------------
329 /// DominatorTree GraphTraits specialization so the DominatorTree can be
330 /// iterable by generic graph iterators.
332 template <> struct GraphTraits<DomTreeNode*> {
333 typedef DomTreeNode NodeType;
334 typedef NodeType::iterator ChildIteratorType;
336 static NodeType *getEntryNode(NodeType *N) {
339 static inline ChildIteratorType child_begin(NodeType* N) {
342 static inline ChildIteratorType child_end(NodeType* N) {
347 template <> struct GraphTraits<DominatorTree*>
348 : public GraphTraits<DomTreeNode*> {
349 static NodeType *getEntryNode(DominatorTree *DT) {
350 return DT->getRootNode();
355 //===----------------------------------------------------------------------===//
356 /// DominanceFrontierBase - Common base class for computing forward and inverse
357 /// dominance frontiers for a function.
359 class DominanceFrontierBase : public DominatorBase {
361 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
362 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
364 DomSetMapType Frontiers;
366 DominanceFrontierBase(intptr_t ID, bool isPostDom)
367 : DominatorBase(ID, isPostDom) {}
369 virtual void releaseMemory() { Frontiers.clear(); }
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); }
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));
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)
394 void addToFrontier(iterator I, BasicBlock *Node) {
395 assert(I != end() && "BB is not in DominanceFrontier!");
396 I->second.insert(Node);
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);
405 /// print - Convert to human readable form
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);
415 //===-------------------------------------
416 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
417 /// used to compute a forward dominator frontiers.
419 class DominanceFrontier : public DominanceFrontierBase {
421 static char ID; // Pass ID, replacement for typeid
422 DominanceFrontier() :
423 DominanceFrontierBase(intptr_t(&ID), false) {}
425 BasicBlock *getRoot() const {
426 assert(Roots.size() == 1 && "Should always have entry node!");
430 virtual bool runOnFunction(Function &) {
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]]);
439 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
440 AU.setPreservesAll();
441 AU.addRequired<DominatorTree>();
444 /// splitBlock - BB is split and now it has one successor. Update dominance
445 /// frontier to reflect this change.
446 void splitBlock(BasicBlock *BB);
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,
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);
465 NewDFI->second.erase(BB);
469 const DomSetType &calculate(const DominatorTree &DT,
470 const DomTreeNode *Node);
474 } // End llvm namespace