1 //===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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"
25 #include "llvm/Function.h"
26 #include "llvm/Instructions.h"
27 #include "llvm/ADT/DenseMap.h"
28 #include "llvm/ADT/DepthFirstIterator.h"
29 #include "llvm/ADT/GraphTraits.h"
30 #include "llvm/ADT/SmallPtrSet.h"
31 #include "llvm/ADT/SmallVector.h"
32 #include "llvm/Assembly/Writer.h"
33 #include "llvm/Support/CFG.h"
34 #include "llvm/Support/Compiler.h"
35 #include "llvm/Support/raw_ostream.h"
42 //===----------------------------------------------------------------------===//
43 /// DominatorBase - Base class that other, more interesting dominator analyses
46 template <class NodeT>
49 std::vector<NodeT*> Roots;
50 const bool IsPostDominators;
51 inline explicit DominatorBase(bool isPostDom) :
52 Roots(), IsPostDominators(isPostDom) {}
55 /// getRoots - Return the root blocks of the current CFG. This may include
56 /// multiple blocks if we are computing post dominators. For forward
57 /// dominators, this will always be a single block (the entry node).
59 inline const std::vector<NodeT*> &getRoots() const { return Roots; }
61 /// isPostDominator - Returns true if analysis based of postdoms
63 bool isPostDominator() const { return IsPostDominators; }
67 //===----------------------------------------------------------------------===//
68 // DomTreeNode - Dominator Tree Node
69 template<class NodeT> class DominatorTreeBase;
70 struct PostDominatorTree;
71 class MachineBasicBlock;
73 template <class NodeT>
74 class DomTreeNodeBase {
76 DomTreeNodeBase<NodeT> *IDom;
77 std::vector<DomTreeNodeBase<NodeT> *> Children;
78 int DFSNumIn, DFSNumOut;
80 template<class N> friend class DominatorTreeBase;
81 friend struct PostDominatorTree;
83 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator;
84 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator
87 iterator begin() { return Children.begin(); }
88 iterator end() { return Children.end(); }
89 const_iterator begin() const { return Children.begin(); }
90 const_iterator end() const { return Children.end(); }
92 NodeT *getBlock() const { return TheBB; }
93 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; }
94 const std::vector<DomTreeNodeBase<NodeT>*> &getChildren() const {
98 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom)
99 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { }
101 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) {
102 Children.push_back(C);
106 size_t getNumChildren() const {
107 return Children.size();
110 void clearAllChildren() {
114 bool compare(DomTreeNodeBase<NodeT> *Other) {
115 if (getNumChildren() != Other->getNumChildren())
118 SmallPtrSet<NodeT *, 4> OtherChildren;
119 for (iterator I = Other->begin(), E = Other->end(); I != E; ++I) {
120 NodeT *Nd = (*I)->getBlock();
121 OtherChildren.insert(Nd);
124 for (iterator I = begin(), E = end(); I != E; ++I) {
125 NodeT *N = (*I)->getBlock();
126 if (OtherChildren.count(N) == 0)
132 void setIDom(DomTreeNodeBase<NodeT> *NewIDom) {
133 assert(IDom && "No immediate dominator?");
134 if (IDom != NewIDom) {
135 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
136 std::find(IDom->Children.begin(), IDom->Children.end(), this);
137 assert(I != IDom->Children.end() &&
138 "Not in immediate dominator children set!");
139 // I am no longer your child...
140 IDom->Children.erase(I);
142 // Switch to new dominator
144 IDom->Children.push_back(this);
148 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
150 unsigned getDFSNumIn() const { return DFSNumIn; }
151 unsigned getDFSNumOut() const { return DFSNumOut; }
153 // Return true if this node is dominated by other. Use this only if DFS info
155 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const {
156 return this->DFSNumIn >= other->DFSNumIn &&
157 this->DFSNumOut <= other->DFSNumOut;
161 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<BasicBlock>);
162 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<MachineBasicBlock>);
164 template<class NodeT>
165 static raw_ostream &operator<<(raw_ostream &o,
166 const DomTreeNodeBase<NodeT> *Node) {
167 if (Node->getBlock())
168 WriteAsOperand(o, Node->getBlock(), false);
170 o << " <<exit node>>";
172 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}";
177 template<class NodeT>
178 static void PrintDomTree(const DomTreeNodeBase<NodeT> *N, raw_ostream &o,
180 o.indent(2*Lev) << "[" << Lev << "] " << N;
181 for (typename DomTreeNodeBase<NodeT>::const_iterator I = N->begin(),
182 E = N->end(); I != E; ++I)
183 PrintDomTree<NodeT>(*I, o, Lev+1);
186 typedef DomTreeNodeBase<BasicBlock> DomTreeNode;
188 //===----------------------------------------------------------------------===//
189 /// DominatorTree - Calculate the immediate dominator tree for a function.
192 template<class FuncT, class N>
193 void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
196 template<class NodeT>
197 class DominatorTreeBase : public DominatorBase<NodeT> {
199 typedef DenseMap<NodeT*, DomTreeNodeBase<NodeT>*> DomTreeNodeMapType;
200 DomTreeNodeMapType DomTreeNodes;
201 DomTreeNodeBase<NodeT> *RootNode;
204 unsigned int SlowQueries;
205 // Information record used during immediate dominators computation.
210 NodeT *Label, *Child;
211 unsigned Parent, Ancestor;
213 std::vector<NodeT*> Bucket;
215 InfoRec() : DFSNum(0), Semi(0), Size(0), Label(0), Child(0), Parent(0),
219 DenseMap<NodeT*, NodeT*> IDoms;
221 // Vertex - Map the DFS number to the BasicBlock*
222 std::vector<NodeT*> Vertex;
224 // Info - Collection of information used during the computation of idoms.
225 DenseMap<NodeT*, InfoRec> Info;
228 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(),
229 E = DomTreeNodes.end(); I != E; ++I)
231 DomTreeNodes.clear();
238 // NewBB is split and now it has one successor. Update dominator tree to
239 // reflect this change.
240 template<class N, class GraphT>
241 void Split(DominatorTreeBase<typename GraphT::NodeType>& DT,
242 typename GraphT::NodeType* NewBB) {
243 assert(std::distance(GraphT::child_begin(NewBB),
244 GraphT::child_end(NewBB)) == 1 &&
245 "NewBB should have a single successor!");
246 typename GraphT::NodeType* NewBBSucc = *GraphT::child_begin(NewBB);
248 std::vector<typename GraphT::NodeType*> PredBlocks;
249 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI =
250 GraphTraits<Inverse<N> >::child_begin(NewBB),
251 PE = GraphTraits<Inverse<N> >::child_end(NewBB); PI != PE; ++PI)
252 PredBlocks.push_back(*PI);
254 assert(!PredBlocks.empty() && "No predblocks??");
256 bool NewBBDominatesNewBBSucc = true;
257 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI =
258 GraphTraits<Inverse<N> >::child_begin(NewBBSucc),
259 E = GraphTraits<Inverse<N> >::child_end(NewBBSucc); PI != E; ++PI)
260 if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI) &&
261 DT.isReachableFromEntry(*PI)) {
262 NewBBDominatesNewBBSucc = false;
266 // Find NewBB's immediate dominator and create new dominator tree node for
268 NodeT *NewBBIDom = 0;
270 for (i = 0; i < PredBlocks.size(); ++i)
271 if (DT.isReachableFromEntry(PredBlocks[i])) {
272 NewBBIDom = PredBlocks[i];
276 // It's possible that none of the predecessors of NewBB are reachable;
277 // in that case, NewBB itself is unreachable, so nothing needs to be
282 for (i = i + 1; i < PredBlocks.size(); ++i) {
283 if (DT.isReachableFromEntry(PredBlocks[i]))
284 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
287 // Create the new dominator tree node... and set the idom of NewBB.
288 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
290 // If NewBB strictly dominates other blocks, then it is now the immediate
291 // dominator of NewBBSucc. Update the dominator tree as appropriate.
292 if (NewBBDominatesNewBBSucc) {
293 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc);
294 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
299 explicit DominatorTreeBase(bool isPostDom)
300 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
301 virtual ~DominatorTreeBase() { reset(); }
303 // FIXME: Should remove this
304 virtual bool runOnFunction(Function &F) { return false; }
306 /// compare - Return false if the other dominator tree base matches this
307 /// dominator tree base. Otherwise return true.
308 bool compare(DominatorTreeBase &Other) const {
310 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
311 if (DomTreeNodes.size() != OtherDomTreeNodes.size())
314 for (typename DomTreeNodeMapType::const_iterator
315 I = this->DomTreeNodes.begin(),
316 E = this->DomTreeNodes.end(); I != E; ++I) {
317 NodeT *BB = I->first;
318 typename DomTreeNodeMapType::const_iterator OI = OtherDomTreeNodes.find(BB);
319 if (OI == OtherDomTreeNodes.end())
322 DomTreeNodeBase<NodeT>* MyNd = I->second;
323 DomTreeNodeBase<NodeT>* OtherNd = OI->second;
325 if (MyNd->compare(OtherNd))
332 virtual void releaseMemory() { reset(); }
334 /// getNode - return the (Post)DominatorTree node for the specified basic
335 /// block. This is the same as using operator[] on this class.
337 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
338 typename DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB);
339 return I != DomTreeNodes.end() ? I->second : 0;
342 /// getRootNode - This returns the entry node for the CFG of the function. If
343 /// this tree represents the post-dominance relations for a function, however,
344 /// this root may be a node with the block == NULL. This is the case when
345 /// there are multiple exit nodes from a particular function. Consumers of
346 /// post-dominance information must be capable of dealing with this
349 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
350 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
352 /// properlyDominates - Returns true iff this dominates N and this != N.
353 /// Note that this is not a constant time operation!
355 bool properlyDominates(const DomTreeNodeBase<NodeT> *A,
356 const DomTreeNodeBase<NodeT> *B) const {
357 if (A == 0 || B == 0) return false;
358 return dominatedBySlowTreeWalk(A, B);
361 inline bool properlyDominates(NodeT *A, NodeT *B) {
362 return properlyDominates(getNode(A), getNode(B));
365 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
366 const DomTreeNodeBase<NodeT> *B) const {
367 const DomTreeNodeBase<NodeT> *IDom;
368 if (A == 0 || B == 0) return false;
369 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B)
370 B = IDom; // Walk up the tree
375 /// isReachableFromEntry - Return true if A is dominated by the entry
376 /// block of the function containing it.
377 bool isReachableFromEntry(NodeT* A) {
378 assert(!this->isPostDominator() &&
379 "This is not implemented for post dominators");
380 return dominates(&A->getParent()->front(), A);
383 /// dominates - Returns true iff A dominates B. Note that this is not a
384 /// constant time operation!
386 inline bool dominates(const DomTreeNodeBase<NodeT> *A,
387 const DomTreeNodeBase<NodeT> *B) {
389 return true; // A node trivially dominates itself.
391 if (A == 0 || B == 0)
394 // Compare the result of the tree walk and the dfs numbers, if expensive
395 // checks are enabled.
397 assert((!DFSInfoValid ||
398 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) &&
399 "Tree walk disagrees with dfs numbers!");
403 return B->DominatedBy(A);
405 // If we end up with too many slow queries, just update the
406 // DFS numbers on the theory that we are going to keep querying.
408 if (SlowQueries > 32) {
410 return B->DominatedBy(A);
413 return dominatedBySlowTreeWalk(A, B);
416 inline bool dominates(const NodeT *A, const NodeT *B) {
420 // Cast away the const qualifiers here. This is ok since
421 // this function doesn't actually return the values returned
423 return dominates(getNode(const_cast<NodeT *>(A)),
424 getNode(const_cast<NodeT *>(B)));
427 NodeT *getRoot() const {
428 assert(this->Roots.size() == 1 && "Should always have entry node!");
429 return this->Roots[0];
432 /// findNearestCommonDominator - Find nearest common dominator basic block
433 /// for basic block A and B. If there is no such block then return NULL.
434 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
435 assert(A->getParent() == B->getParent() &&
436 "Two blocks are not in same function");
438 // If either A or B is a entry block then it is nearest common dominator
439 // (for forward-dominators).
440 if (!this->isPostDominator()) {
441 NodeT &Entry = A->getParent()->front();
442 if (A == &Entry || B == &Entry)
446 // If B dominates A then B is nearest common dominator.
450 // If A dominates B then A is nearest common dominator.
454 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
455 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
457 // Collect NodeA dominators set.
458 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms;
459 NodeADoms.insert(NodeA);
460 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
462 NodeADoms.insert(IDomA);
463 IDomA = IDomA->getIDom();
466 // Walk NodeB immediate dominators chain and find common dominator node.
467 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
469 if (NodeADoms.count(IDomB) != 0)
470 return IDomB->getBlock();
472 IDomB = IDomB->getIDom();
478 //===--------------------------------------------------------------------===//
479 // API to update (Post)DominatorTree information based on modifications to
482 /// addNewBlock - Add a new node to the dominator tree information. This
483 /// creates a new node as a child of DomBB dominator node,linking it into
484 /// the children list of the immediate dominator.
485 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
486 assert(getNode(BB) == 0 && "Block already in dominator tree!");
487 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
488 assert(IDomNode && "Not immediate dominator specified for block!");
489 DFSInfoValid = false;
490 return DomTreeNodes[BB] =
491 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
494 /// changeImmediateDominator - This method is used to update the dominator
495 /// tree information when a node's immediate dominator changes.
497 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
498 DomTreeNodeBase<NodeT> *NewIDom) {
499 assert(N && NewIDom && "Cannot change null node pointers!");
500 DFSInfoValid = false;
504 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
505 changeImmediateDominator(getNode(BB), getNode(NewBB));
508 /// eraseNode - Removes a node from the dominator tree. Block must not
509 /// domiante any other blocks. Removes node from its immediate dominator's
510 /// children list. Deletes dominator node associated with basic block BB.
511 void eraseNode(NodeT *BB) {
512 DomTreeNodeBase<NodeT> *Node = getNode(BB);
513 assert(Node && "Removing node that isn't in dominator tree.");
514 assert(Node->getChildren().empty() && "Node is not a leaf node.");
516 // Remove node from immediate dominator's children list.
517 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
519 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
520 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
521 assert(I != IDom->Children.end() &&
522 "Not in immediate dominator children set!");
523 // I am no longer your child...
524 IDom->Children.erase(I);
527 DomTreeNodes.erase(BB);
531 /// removeNode - Removes a node from the dominator tree. Block must not
532 /// dominate any other blocks. Invalidates any node pointing to removed
534 void removeNode(NodeT *BB) {
535 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
536 DomTreeNodes.erase(BB);
539 /// splitBlock - BB is split and now it has one successor. Update dominator
540 /// tree to reflect this change.
541 void splitBlock(NodeT* NewBB) {
542 if (this->IsPostDominators)
543 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB);
545 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB);
548 /// print - Convert to human readable form
550 void print(raw_ostream &o) const {
551 o << "=============================--------------------------------\n";
552 if (this->isPostDominator())
553 o << "Inorder PostDominator Tree: ";
555 o << "Inorder Dominator Tree: ";
556 if (this->DFSInfoValid)
557 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
560 // The postdom tree can have a null root if there are no returns.
562 PrintDomTree<NodeT>(getRootNode(), o, 1);
566 template<class GraphT>
567 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
568 typename GraphT::NodeType* VIn);
570 template<class GraphT>
571 friend typename GraphT::NodeType* Eval(
572 DominatorTreeBase<typename GraphT::NodeType>& DT,
573 typename GraphT::NodeType* V);
575 template<class GraphT>
576 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
577 unsigned DFSNumV, typename GraphT::NodeType* W,
578 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo);
580 template<class GraphT>
581 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
582 typename GraphT::NodeType* V,
585 template<class FuncT, class N>
586 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
589 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
590 /// dominator tree in dfs order.
591 void updateDFSNumbers() {
594 SmallVector<std::pair<DomTreeNodeBase<NodeT>*,
595 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack;
597 DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
602 // Even in the case of multiple exits that form the post dominator root
603 // nodes, do not iterate over all exits, but start from the virtual root
604 // node. Otherwise bbs, that are not post dominated by any exit but by the
605 // virtual root node, will never be assigned a DFS number.
606 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
607 ThisRoot->DFSNumIn = DFSNum++;
609 while (!WorkStack.empty()) {
610 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
611 typename DomTreeNodeBase<NodeT>::iterator ChildIt =
612 WorkStack.back().second;
614 // If we visited all of the children of this node, "recurse" back up the
615 // stack setting the DFOutNum.
616 if (ChildIt == Node->end()) {
617 Node->DFSNumOut = DFSNum++;
618 WorkStack.pop_back();
620 // Otherwise, recursively visit this child.
621 DomTreeNodeBase<NodeT> *Child = *ChildIt;
622 ++WorkStack.back().second;
624 WorkStack.push_back(std::make_pair(Child, Child->begin()));
625 Child->DFSNumIn = DFSNum++;
633 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
634 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB);
635 if (I != this->DomTreeNodes.end() && I->second)
638 // Haven't calculated this node yet? Get or calculate the node for the
639 // immediate dominator.
640 NodeT *IDom = getIDom(BB);
642 assert(IDom || this->DomTreeNodes[NULL]);
643 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
645 // Add a new tree node for this BasicBlock, and link it as a child of
647 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
648 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
651 inline NodeT *getIDom(NodeT *BB) const {
652 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB);
653 return I != IDoms.end() ? I->second : 0;
656 inline void addRoot(NodeT* BB) {
657 this->Roots.push_back(BB);
661 /// recalculate - compute a dominator tree for the given function
663 void recalculate(FT& F) {
665 this->Vertex.push_back(0);
667 if (!this->IsPostDominators) {
669 this->Roots.push_back(&F.front());
670 this->IDoms[&F.front()] = 0;
671 this->DomTreeNodes[&F.front()] = 0;
673 Calculate<FT, NodeT*>(*this, F);
675 // Initialize the roots list
676 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) {
677 if (std::distance(GraphTraits<FT*>::child_begin(I),
678 GraphTraits<FT*>::child_end(I)) == 0)
681 // Prepopulate maps so that we don't get iterator invalidation issues later.
683 this->DomTreeNodes[I] = 0;
686 Calculate<FT, Inverse<NodeT*> >(*this, F);
691 EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
693 //===-------------------------------------
694 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
695 /// compute a normal dominator tree.
697 class DominatorTree : public FunctionPass {
699 static char ID; // Pass ID, replacement for typeid
700 DominatorTreeBase<BasicBlock>* DT;
702 DominatorTree() : FunctionPass(&ID) {
703 DT = new DominatorTreeBase<BasicBlock>(false);
710 DominatorTreeBase<BasicBlock>& getBase() { return *DT; }
712 /// getRoots - Return the root blocks of the current CFG. This may include
713 /// multiple blocks if we are computing post dominators. For forward
714 /// dominators, this will always be a single block (the entry node).
716 inline const std::vector<BasicBlock*> &getRoots() const {
717 return DT->getRoots();
720 inline BasicBlock *getRoot() const {
721 return DT->getRoot();
724 inline DomTreeNode *getRootNode() const {
725 return DT->getRootNode();
728 /// compare - Return false if the other dominator tree matches this
729 /// dominator tree. Otherwise return true.
730 inline bool compare(DominatorTree &Other) const {
731 DomTreeNode *R = getRootNode();
732 DomTreeNode *OtherR = Other.getRootNode();
734 if (!R || !OtherR || R->getBlock() != OtherR->getBlock())
737 if (DT->compare(Other.getBase()))
743 virtual bool runOnFunction(Function &F);
745 virtual void verifyAnalysis() const;
747 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
748 AU.setPreservesAll();
751 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const {
752 return DT->dominates(A, B);
755 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const {
756 return DT->dominates(A, B);
759 // dominates - Return true if A dominates B. This performs the
760 // special checks necessary if A and B are in the same basic block.
761 bool dominates(const Instruction *A, const Instruction *B) const;
763 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const {
764 return DT->properlyDominates(A, B);
767 bool properlyDominates(BasicBlock *A, BasicBlock *B) const {
768 return DT->properlyDominates(A, B);
771 /// findNearestCommonDominator - Find nearest common dominator basic block
772 /// for basic block A and B. If there is no such block then return NULL.
773 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) {
774 return DT->findNearestCommonDominator(A, B);
777 inline DomTreeNode *operator[](BasicBlock *BB) const {
778 return DT->getNode(BB);
781 /// getNode - return the (Post)DominatorTree node for the specified basic
782 /// block. This is the same as using operator[] on this class.
784 inline DomTreeNode *getNode(BasicBlock *BB) const {
785 return DT->getNode(BB);
788 /// addNewBlock - Add a new node to the dominator tree information. This
789 /// creates a new node as a child of DomBB dominator node,linking it into
790 /// the children list of the immediate dominator.
791 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
792 return DT->addNewBlock(BB, DomBB);
795 /// changeImmediateDominator - This method is used to update the dominator
796 /// tree information when a node's immediate dominator changes.
798 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) {
799 DT->changeImmediateDominator(N, NewIDom);
802 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) {
803 DT->changeImmediateDominator(N, NewIDom);
806 /// eraseNode - Removes a node from the dominator tree. Block must not
807 /// domiante any other blocks. Removes node from its immediate dominator's
808 /// children list. Deletes dominator node associated with basic block BB.
809 inline void eraseNode(BasicBlock *BB) {
813 /// splitBlock - BB is split and now it has one successor. Update dominator
814 /// tree to reflect this change.
815 inline void splitBlock(BasicBlock* NewBB) {
816 DT->splitBlock(NewBB);
819 bool isReachableFromEntry(BasicBlock* A) {
820 return DT->isReachableFromEntry(A);
824 virtual void releaseMemory() {
828 virtual void print(raw_ostream &OS, const Module* M= 0) const;
831 //===-------------------------------------
832 /// DominatorTree GraphTraits specialization so the DominatorTree can be
833 /// iterable by generic graph iterators.
835 template <> struct GraphTraits<DomTreeNode*> {
836 typedef DomTreeNode NodeType;
837 typedef NodeType::iterator ChildIteratorType;
839 static NodeType *getEntryNode(NodeType *N) {
842 static inline ChildIteratorType child_begin(NodeType *N) {
845 static inline ChildIteratorType child_end(NodeType *N) {
849 typedef df_iterator<DomTreeNode*> nodes_iterator;
851 static nodes_iterator nodes_begin(DomTreeNode *N) {
852 return df_begin(getEntryNode(N));
855 static nodes_iterator nodes_end(DomTreeNode *N) {
856 return df_end(getEntryNode(N));
860 template <> struct GraphTraits<DominatorTree*>
861 : public GraphTraits<DomTreeNode*> {
862 static NodeType *getEntryNode(DominatorTree *DT) {
863 return DT->getRootNode();
866 static nodes_iterator nodes_begin(DominatorTree *N) {
867 return df_begin(getEntryNode(N));
870 static nodes_iterator nodes_end(DominatorTree *N) {
871 return df_end(getEntryNode(N));
876 //===----------------------------------------------------------------------===//
877 /// DominanceFrontierBase - Common base class for computing forward and inverse
878 /// dominance frontiers for a function.
880 class DominanceFrontierBase : public FunctionPass {
882 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
883 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
885 DomSetMapType Frontiers;
886 std::vector<BasicBlock*> Roots;
887 const bool IsPostDominators;
890 DominanceFrontierBase(void *ID, bool isPostDom)
891 : FunctionPass(ID), IsPostDominators(isPostDom) {}
893 /// getRoots - Return the root blocks of the current CFG. This may include
894 /// multiple blocks if we are computing post dominators. For forward
895 /// dominators, this will always be a single block (the entry node).
897 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
899 /// isPostDominator - Returns true if analysis based of postdoms
901 bool isPostDominator() const { return IsPostDominators; }
903 virtual void releaseMemory() { Frontiers.clear(); }
905 // Accessor interface:
906 typedef DomSetMapType::iterator iterator;
907 typedef DomSetMapType::const_iterator const_iterator;
908 iterator begin() { return Frontiers.begin(); }
909 const_iterator begin() const { return Frontiers.begin(); }
910 iterator end() { return Frontiers.end(); }
911 const_iterator end() const { return Frontiers.end(); }
912 iterator find(BasicBlock *B) { return Frontiers.find(B); }
913 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
915 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
916 assert(find(BB) == end() && "Block already in DominanceFrontier!");
917 return Frontiers.insert(std::make_pair(BB, frontier)).first;
920 /// removeBlock - Remove basic block BB's frontier.
921 void removeBlock(BasicBlock *BB) {
922 assert(find(BB) != end() && "Block is not in DominanceFrontier!");
923 for (iterator I = begin(), E = end(); I != E; ++I)
928 void addToFrontier(iterator I, BasicBlock *Node) {
929 assert(I != end() && "BB is not in DominanceFrontier!");
930 I->second.insert(Node);
933 void removeFromFrontier(iterator I, BasicBlock *Node) {
934 assert(I != end() && "BB is not in DominanceFrontier!");
935 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
936 I->second.erase(Node);
939 /// compareDomSet - Return false if two domsets match. Otherwise
941 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const {
942 std::set<BasicBlock *> tmpSet;
943 for (DomSetType::const_iterator I = DS2.begin(),
944 E = DS2.end(); I != E; ++I)
947 for (DomSetType::const_iterator I = DS1.begin(),
948 E = DS1.end(); I != E; ) {
949 BasicBlock *Node = *I++;
951 if (tmpSet.erase(Node) == 0)
952 // Node is in DS1 but not in DS2.
957 // There are nodes that are in DS2 but not in DS1.
960 // DS1 and DS2 matches.
964 /// compare - Return true if the other dominance frontier base matches
965 /// this dominance frontier base. Otherwise return false.
966 bool compare(DominanceFrontierBase &Other) const {
967 DomSetMapType tmpFrontiers;
968 for (DomSetMapType::const_iterator I = Other.begin(),
969 E = Other.end(); I != E; ++I)
970 tmpFrontiers.insert(std::make_pair(I->first, I->second));
972 for (DomSetMapType::iterator I = tmpFrontiers.begin(),
973 E = tmpFrontiers.end(); I != E; ) {
974 BasicBlock *Node = I->first;
975 const_iterator DFI = find(Node);
979 if (compareDomSet(I->second, DFI->second))
983 tmpFrontiers.erase(Node);
986 if (!tmpFrontiers.empty())
992 /// print - Convert to human readable form
994 virtual void print(raw_ostream &OS, const Module* = 0) const;
998 //===-------------------------------------
999 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
1000 /// used to compute a forward dominator frontiers.
1002 class DominanceFrontier : public DominanceFrontierBase {
1004 static char ID; // Pass ID, replacement for typeid
1005 DominanceFrontier() :
1006 DominanceFrontierBase(&ID, false) {}
1008 BasicBlock *getRoot() const {
1009 assert(Roots.size() == 1 && "Should always have entry node!");
1013 virtual bool runOnFunction(Function &) {
1015 DominatorTree &DT = getAnalysis<DominatorTree>();
1016 Roots = DT.getRoots();
1017 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
1018 calculate(DT, DT[Roots[0]]);
1022 virtual void verifyAnalysis() const;
1024 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
1025 AU.setPreservesAll();
1026 AU.addRequired<DominatorTree>();
1029 /// splitBlock - BB is split and now it has one successor. Update dominance
1030 /// frontier to reflect this change.
1031 void splitBlock(BasicBlock *BB);
1033 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier
1034 /// to reflect this change.
1035 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB,
1036 DominatorTree *DT) {
1037 // NewBB is now dominating BB. Which means BB's dominance
1038 // frontier is now part of NewBB's dominance frontier. However, BB
1039 // itself is not member of NewBB's dominance frontier.
1040 DominanceFrontier::iterator NewDFI = find(NewBB);
1041 DominanceFrontier::iterator DFI = find(BB);
1042 // If BB was an entry block then its frontier is empty.
1045 DominanceFrontier::DomSetType BBSet = DFI->second;
1046 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
1047 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {
1048 BasicBlock *DFMember = *BBSetI;
1049 // Insert only if NewBB dominates DFMember.
1050 if (!DT->dominates(NewBB, DFMember))
1051 NewDFI->second.insert(DFMember);
1053 NewDFI->second.erase(BB);
1056 const DomSetType &calculate(const DominatorTree &DT,
1057 const DomTreeNode *Node);
1061 } // End llvm namespace