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 typedef GraphTraits<Inverse<N> > InvTraits;
250 for (typename InvTraits::ChildIteratorType PI =
251 InvTraits::child_begin(NewBB),
252 PE = InvTraits::child_end(NewBB); PI != PE; ++PI)
253 PredBlocks.push_back(*PI);
255 assert(!PredBlocks.empty() && "No predblocks?");
257 bool NewBBDominatesNewBBSucc = true;
258 for (typename InvTraits::ChildIteratorType PI =
259 InvTraits::child_begin(NewBBSucc),
260 E = InvTraits::child_end(NewBBSucc); PI != E; ++PI) {
261 typename InvTraits::NodeType *ND = *PI;
262 if (ND != NewBB && !DT.dominates(NewBBSucc, ND) &&
263 DT.isReachableFromEntry(ND)) {
264 NewBBDominatesNewBBSucc = false;
269 // Find NewBB's immediate dominator and create new dominator tree node for
271 NodeT *NewBBIDom = 0;
273 for (i = 0; i < PredBlocks.size(); ++i)
274 if (DT.isReachableFromEntry(PredBlocks[i])) {
275 NewBBIDom = PredBlocks[i];
279 // It's possible that none of the predecessors of NewBB are reachable;
280 // in that case, NewBB itself is unreachable, so nothing needs to be
285 for (i = i + 1; i < PredBlocks.size(); ++i) {
286 if (DT.isReachableFromEntry(PredBlocks[i]))
287 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
290 // Create the new dominator tree node... and set the idom of NewBB.
291 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
293 // If NewBB strictly dominates other blocks, then it is now the immediate
294 // dominator of NewBBSucc. Update the dominator tree as appropriate.
295 if (NewBBDominatesNewBBSucc) {
296 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc);
297 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
302 explicit DominatorTreeBase(bool isPostDom)
303 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
304 virtual ~DominatorTreeBase() { reset(); }
306 // FIXME: Should remove this
307 virtual bool runOnFunction(Function &F) { return false; }
309 /// compare - Return false if the other dominator tree base matches this
310 /// dominator tree base. Otherwise return true.
311 bool compare(DominatorTreeBase &Other) const {
313 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
314 if (DomTreeNodes.size() != OtherDomTreeNodes.size())
317 for (typename DomTreeNodeMapType::const_iterator
318 I = this->DomTreeNodes.begin(),
319 E = this->DomTreeNodes.end(); I != E; ++I) {
320 NodeT *BB = I->first;
321 typename DomTreeNodeMapType::const_iterator OI = OtherDomTreeNodes.find(BB);
322 if (OI == OtherDomTreeNodes.end())
325 DomTreeNodeBase<NodeT>* MyNd = I->second;
326 DomTreeNodeBase<NodeT>* OtherNd = OI->second;
328 if (MyNd->compare(OtherNd))
335 virtual void releaseMemory() { reset(); }
337 /// getNode - return the (Post)DominatorTree node for the specified basic
338 /// block. This is the same as using operator[] on this class.
340 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
341 typename DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB);
342 return I != DomTreeNodes.end() ? I->second : 0;
345 /// getRootNode - This returns the entry node for the CFG of the function. If
346 /// this tree represents the post-dominance relations for a function, however,
347 /// this root may be a node with the block == NULL. This is the case when
348 /// there are multiple exit nodes from a particular function. Consumers of
349 /// post-dominance information must be capable of dealing with this
352 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
353 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
355 /// properlyDominates - Returns true iff this dominates N and this != N.
356 /// Note that this is not a constant time operation!
358 bool properlyDominates(const DomTreeNodeBase<NodeT> *A,
359 const DomTreeNodeBase<NodeT> *B) const {
360 if (A == 0 || B == 0) return false;
361 return dominatedBySlowTreeWalk(A, B);
364 inline bool properlyDominates(const NodeT *A, const NodeT *B) {
368 // Cast away the const qualifiers here. This is ok since
369 // this function doesn't actually return the values returned
371 return properlyDominates(getNode(const_cast<NodeT *>(A)),
372 getNode(const_cast<NodeT *>(B)));
375 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
376 const DomTreeNodeBase<NodeT> *B) const {
377 const DomTreeNodeBase<NodeT> *IDom;
378 if (A == 0 || B == 0) return false;
379 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B)
380 B = IDom; // Walk up the tree
385 /// isReachableFromEntry - Return true if A is dominated by the entry
386 /// block of the function containing it.
387 bool isReachableFromEntry(const NodeT* A) {
388 assert(!this->isPostDominator() &&
389 "This is not implemented for post dominators");
390 return dominates(&A->getParent()->front(), A);
393 /// dominates - Returns true iff A dominates B. Note that this is not a
394 /// constant time operation!
396 inline bool dominates(const DomTreeNodeBase<NodeT> *A,
397 const DomTreeNodeBase<NodeT> *B) {
399 return true; // A node trivially dominates itself.
401 if (A == 0 || B == 0)
404 // Compare the result of the tree walk and the dfs numbers, if expensive
405 // checks are enabled.
407 assert((!DFSInfoValid ||
408 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) &&
409 "Tree walk disagrees with dfs numbers!");
413 return B->DominatedBy(A);
415 // If we end up with too many slow queries, just update the
416 // DFS numbers on the theory that we are going to keep querying.
418 if (SlowQueries > 32) {
420 return B->DominatedBy(A);
423 return dominatedBySlowTreeWalk(A, B);
426 inline bool dominates(const NodeT *A, const NodeT *B) {
430 // Cast away the const qualifiers here. This is ok since
431 // this function doesn't actually return the values returned
433 return dominates(getNode(const_cast<NodeT *>(A)),
434 getNode(const_cast<NodeT *>(B)));
437 NodeT *getRoot() const {
438 assert(this->Roots.size() == 1 && "Should always have entry node!");
439 return this->Roots[0];
442 /// findNearestCommonDominator - Find nearest common dominator basic block
443 /// for basic block A and B. If there is no such block then return NULL.
444 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
445 assert(A->getParent() == B->getParent() &&
446 "Two blocks are not in same function");
448 // If either A or B is a entry block then it is nearest common dominator
449 // (for forward-dominators).
450 if (!this->isPostDominator()) {
451 NodeT &Entry = A->getParent()->front();
452 if (A == &Entry || B == &Entry)
456 // If B dominates A then B is nearest common dominator.
460 // If A dominates B then A is nearest common dominator.
464 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
465 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
467 // Collect NodeA dominators set.
468 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms;
469 NodeADoms.insert(NodeA);
470 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
472 NodeADoms.insert(IDomA);
473 IDomA = IDomA->getIDom();
476 // Walk NodeB immediate dominators chain and find common dominator node.
477 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
479 if (NodeADoms.count(IDomB) != 0)
480 return IDomB->getBlock();
482 IDomB = IDomB->getIDom();
488 const NodeT *findNearestCommonDominator(const NodeT *A, const NodeT *B) {
489 // Cast away the const qualifiers here. This is ok since
490 // const is re-introduced on the return type.
491 return findNearestCommonDominator(const_cast<NodeT *>(A),
492 const_cast<NodeT *>(B));
495 //===--------------------------------------------------------------------===//
496 // API to update (Post)DominatorTree information based on modifications to
499 /// addNewBlock - Add a new node to the dominator tree information. This
500 /// creates a new node as a child of DomBB dominator node,linking it into
501 /// the children list of the immediate dominator.
502 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
503 assert(getNode(BB) == 0 && "Block already in dominator tree!");
504 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
505 assert(IDomNode && "Not immediate dominator specified for block!");
506 DFSInfoValid = false;
507 return DomTreeNodes[BB] =
508 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
511 /// changeImmediateDominator - This method is used to update the dominator
512 /// tree information when a node's immediate dominator changes.
514 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
515 DomTreeNodeBase<NodeT> *NewIDom) {
516 assert(N && NewIDom && "Cannot change null node pointers!");
517 DFSInfoValid = false;
521 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
522 changeImmediateDominator(getNode(BB), getNode(NewBB));
525 /// eraseNode - Removes a node from the dominator tree. Block must not
526 /// dominate any other blocks. Removes node from its immediate dominator's
527 /// children list. Deletes dominator node associated with basic block BB.
528 void eraseNode(NodeT *BB) {
529 DomTreeNodeBase<NodeT> *Node = getNode(BB);
530 assert(Node && "Removing node that isn't in dominator tree.");
531 assert(Node->getChildren().empty() && "Node is not a leaf node.");
533 // Remove node from immediate dominator's children list.
534 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
536 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
537 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
538 assert(I != IDom->Children.end() &&
539 "Not in immediate dominator children set!");
540 // I am no longer your child...
541 IDom->Children.erase(I);
544 DomTreeNodes.erase(BB);
548 /// removeNode - Removes a node from the dominator tree. Block must not
549 /// dominate any other blocks. Invalidates any node pointing to removed
551 void removeNode(NodeT *BB) {
552 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
553 DomTreeNodes.erase(BB);
556 /// splitBlock - BB is split and now it has one successor. Update dominator
557 /// tree to reflect this change.
558 void splitBlock(NodeT* NewBB) {
559 if (this->IsPostDominators)
560 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB);
562 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB);
565 /// print - Convert to human readable form
567 void print(raw_ostream &o) const {
568 o << "=============================--------------------------------\n";
569 if (this->isPostDominator())
570 o << "Inorder PostDominator Tree: ";
572 o << "Inorder Dominator Tree: ";
573 if (this->DFSInfoValid)
574 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
577 // The postdom tree can have a null root if there are no returns.
579 PrintDomTree<NodeT>(getRootNode(), o, 1);
583 template<class GraphT>
584 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
585 typename GraphT::NodeType* VIn);
587 template<class GraphT>
588 friend typename GraphT::NodeType* Eval(
589 DominatorTreeBase<typename GraphT::NodeType>& DT,
590 typename GraphT::NodeType* V);
592 template<class GraphT>
593 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
594 unsigned DFSNumV, typename GraphT::NodeType* W,
595 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo);
597 template<class GraphT>
598 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
599 typename GraphT::NodeType* V,
602 template<class FuncT, class N>
603 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
606 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
607 /// dominator tree in dfs order.
608 void updateDFSNumbers() {
611 SmallVector<std::pair<DomTreeNodeBase<NodeT>*,
612 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack;
614 DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
619 // Even in the case of multiple exits that form the post dominator root
620 // nodes, do not iterate over all exits, but start from the virtual root
621 // node. Otherwise bbs, that are not post dominated by any exit but by the
622 // virtual root node, will never be assigned a DFS number.
623 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
624 ThisRoot->DFSNumIn = DFSNum++;
626 while (!WorkStack.empty()) {
627 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
628 typename DomTreeNodeBase<NodeT>::iterator ChildIt =
629 WorkStack.back().second;
631 // If we visited all of the children of this node, "recurse" back up the
632 // stack setting the DFOutNum.
633 if (ChildIt == Node->end()) {
634 Node->DFSNumOut = DFSNum++;
635 WorkStack.pop_back();
637 // Otherwise, recursively visit this child.
638 DomTreeNodeBase<NodeT> *Child = *ChildIt;
639 ++WorkStack.back().second;
641 WorkStack.push_back(std::make_pair(Child, Child->begin()));
642 Child->DFSNumIn = DFSNum++;
650 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
651 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB);
652 if (I != this->DomTreeNodes.end() && I->second)
655 // Haven't calculated this node yet? Get or calculate the node for the
656 // immediate dominator.
657 NodeT *IDom = getIDom(BB);
659 assert(IDom || this->DomTreeNodes[NULL]);
660 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
662 // Add a new tree node for this BasicBlock, and link it as a child of
664 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
665 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
668 inline NodeT *getIDom(NodeT *BB) const {
669 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB);
670 return I != IDoms.end() ? I->second : 0;
673 inline void addRoot(NodeT* BB) {
674 this->Roots.push_back(BB);
678 /// recalculate - compute a dominator tree for the given function
680 void recalculate(FT& F) {
682 this->Vertex.push_back(0);
684 if (!this->IsPostDominators) {
686 this->Roots.push_back(&F.front());
687 this->IDoms[&F.front()] = 0;
688 this->DomTreeNodes[&F.front()] = 0;
690 Calculate<FT, NodeT*>(*this, F);
692 // Initialize the roots list
693 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) {
694 if (std::distance(GraphTraits<FT*>::child_begin(I),
695 GraphTraits<FT*>::child_end(I)) == 0)
698 // Prepopulate maps so that we don't get iterator invalidation issues later.
700 this->DomTreeNodes[I] = 0;
703 Calculate<FT, Inverse<NodeT*> >(*this, F);
708 EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
710 //===-------------------------------------
711 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
712 /// compute a normal dominator tree.
714 class DominatorTree : public FunctionPass {
716 static char ID; // Pass ID, replacement for typeid
717 DominatorTreeBase<BasicBlock>* DT;
719 DominatorTree() : FunctionPass(ID) {
720 DT = new DominatorTreeBase<BasicBlock>(false);
727 DominatorTreeBase<BasicBlock>& getBase() { return *DT; }
729 /// getRoots - Return the root blocks of the current CFG. This may include
730 /// multiple blocks if we are computing post dominators. For forward
731 /// dominators, this will always be a single block (the entry node).
733 inline const std::vector<BasicBlock*> &getRoots() const {
734 return DT->getRoots();
737 inline BasicBlock *getRoot() const {
738 return DT->getRoot();
741 inline DomTreeNode *getRootNode() const {
742 return DT->getRootNode();
745 /// compare - Return false if the other dominator tree matches this
746 /// dominator tree. Otherwise return true.
747 inline bool compare(DominatorTree &Other) const {
748 DomTreeNode *R = getRootNode();
749 DomTreeNode *OtherR = Other.getRootNode();
751 if (!R || !OtherR || R->getBlock() != OtherR->getBlock())
754 if (DT->compare(Other.getBase()))
760 virtual bool runOnFunction(Function &F);
762 virtual void verifyAnalysis() const;
764 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
765 AU.setPreservesAll();
768 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const {
769 return DT->dominates(A, B);
772 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const {
773 return DT->dominates(A, B);
776 // dominates - Return true if A dominates B. This performs the
777 // special checks necessary if A and B are in the same basic block.
778 bool dominates(const Instruction *A, const Instruction *B) const;
780 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const {
781 return DT->properlyDominates(A, B);
784 bool properlyDominates(const BasicBlock *A, const BasicBlock *B) const {
785 return DT->properlyDominates(A, B);
788 /// findNearestCommonDominator - Find nearest common dominator basic block
789 /// for basic block A and B. If there is no such block then return NULL.
790 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) {
791 return DT->findNearestCommonDominator(A, B);
794 inline const BasicBlock *findNearestCommonDominator(const BasicBlock *A,
795 const BasicBlock *B) {
796 return DT->findNearestCommonDominator(A, B);
799 inline DomTreeNode *operator[](BasicBlock *BB) const {
800 return DT->getNode(BB);
803 /// getNode - return the (Post)DominatorTree node for the specified basic
804 /// block. This is the same as using operator[] on this class.
806 inline DomTreeNode *getNode(BasicBlock *BB) const {
807 return DT->getNode(BB);
810 /// addNewBlock - Add a new node to the dominator tree information. This
811 /// creates a new node as a child of DomBB dominator node,linking it into
812 /// the children list of the immediate dominator.
813 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
814 return DT->addNewBlock(BB, DomBB);
817 /// changeImmediateDominator - This method is used to update the dominator
818 /// tree information when a node's immediate dominator changes.
820 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) {
821 DT->changeImmediateDominator(N, NewIDom);
824 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) {
825 DT->changeImmediateDominator(N, NewIDom);
828 /// eraseNode - Removes a node from the dominator tree. Block must not
829 /// dominate any other blocks. Removes node from its immediate dominator's
830 /// children list. Deletes dominator node associated with basic block BB.
831 inline void eraseNode(BasicBlock *BB) {
835 /// splitBlock - BB is split and now it has one successor. Update dominator
836 /// tree to reflect this change.
837 inline void splitBlock(BasicBlock* NewBB) {
838 DT->splitBlock(NewBB);
841 bool isReachableFromEntry(const BasicBlock* A) {
842 return DT->isReachableFromEntry(A);
846 virtual void releaseMemory() {
850 virtual void print(raw_ostream &OS, const Module* M= 0) const;
853 //===-------------------------------------
854 /// DominatorTree GraphTraits specialization so the DominatorTree can be
855 /// iterable by generic graph iterators.
857 template <> struct GraphTraits<DomTreeNode*> {
858 typedef DomTreeNode NodeType;
859 typedef NodeType::iterator ChildIteratorType;
861 static NodeType *getEntryNode(NodeType *N) {
864 static inline ChildIteratorType child_begin(NodeType *N) {
867 static inline ChildIteratorType child_end(NodeType *N) {
871 typedef df_iterator<DomTreeNode*> nodes_iterator;
873 static nodes_iterator nodes_begin(DomTreeNode *N) {
874 return df_begin(getEntryNode(N));
877 static nodes_iterator nodes_end(DomTreeNode *N) {
878 return df_end(getEntryNode(N));
882 template <> struct GraphTraits<DominatorTree*>
883 : public GraphTraits<DomTreeNode*> {
884 static NodeType *getEntryNode(DominatorTree *DT) {
885 return DT->getRootNode();
888 static nodes_iterator nodes_begin(DominatorTree *N) {
889 return df_begin(getEntryNode(N));
892 static nodes_iterator nodes_end(DominatorTree *N) {
893 return df_end(getEntryNode(N));
898 //===----------------------------------------------------------------------===//
899 /// DominanceFrontierBase - Common base class for computing forward and inverse
900 /// dominance frontiers for a function.
902 class DominanceFrontierBase : public FunctionPass {
904 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
905 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
907 DomSetMapType Frontiers;
908 std::vector<BasicBlock*> Roots;
909 const bool IsPostDominators;
912 DominanceFrontierBase(char &ID, bool isPostDom)
913 : FunctionPass(ID), IsPostDominators(isPostDom) {}
915 /// getRoots - Return the root blocks of the current CFG. This may include
916 /// multiple blocks if we are computing post dominators. For forward
917 /// dominators, this will always be a single block (the entry node).
919 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
921 /// isPostDominator - Returns true if analysis based of postdoms
923 bool isPostDominator() const { return IsPostDominators; }
925 virtual void releaseMemory() { Frontiers.clear(); }
927 // Accessor interface:
928 typedef DomSetMapType::iterator iterator;
929 typedef DomSetMapType::const_iterator const_iterator;
930 iterator begin() { return Frontiers.begin(); }
931 const_iterator begin() const { return Frontiers.begin(); }
932 iterator end() { return Frontiers.end(); }
933 const_iterator end() const { return Frontiers.end(); }
934 iterator find(BasicBlock *B) { return Frontiers.find(B); }
935 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
937 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
938 assert(find(BB) == end() && "Block already in DominanceFrontier!");
939 return Frontiers.insert(std::make_pair(BB, frontier)).first;
942 /// removeBlock - Remove basic block BB's frontier.
943 void removeBlock(BasicBlock *BB) {
944 assert(find(BB) != end() && "Block is not in DominanceFrontier!");
945 for (iterator I = begin(), E = end(); I != E; ++I)
950 void addToFrontier(iterator I, BasicBlock *Node) {
951 assert(I != end() && "BB is not in DominanceFrontier!");
952 I->second.insert(Node);
955 void removeFromFrontier(iterator I, BasicBlock *Node) {
956 assert(I != end() && "BB is not in DominanceFrontier!");
957 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
958 I->second.erase(Node);
961 /// compareDomSet - Return false if two domsets match. Otherwise
963 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const {
964 std::set<BasicBlock *> tmpSet;
965 for (DomSetType::const_iterator I = DS2.begin(),
966 E = DS2.end(); I != E; ++I)
969 for (DomSetType::const_iterator I = DS1.begin(),
970 E = DS1.end(); I != E; ) {
971 BasicBlock *Node = *I++;
973 if (tmpSet.erase(Node) == 0)
974 // Node is in DS1 but not in DS2.
979 // There are nodes that are in DS2 but not in DS1.
982 // DS1 and DS2 matches.
986 /// compare - Return true if the other dominance frontier base matches
987 /// this dominance frontier base. Otherwise return false.
988 bool compare(DominanceFrontierBase &Other) const {
989 DomSetMapType tmpFrontiers;
990 for (DomSetMapType::const_iterator I = Other.begin(),
991 E = Other.end(); I != E; ++I)
992 tmpFrontiers.insert(std::make_pair(I->first, I->second));
994 for (DomSetMapType::iterator I = tmpFrontiers.begin(),
995 E = tmpFrontiers.end(); I != E; ) {
996 BasicBlock *Node = I->first;
997 const_iterator DFI = find(Node);
1001 if (compareDomSet(I->second, DFI->second))
1005 tmpFrontiers.erase(Node);
1008 if (!tmpFrontiers.empty())
1014 /// print - Convert to human readable form
1016 virtual void print(raw_ostream &OS, const Module* = 0) const;
1018 /// dump - Dump the dominance frontier to dbgs().
1023 //===-------------------------------------
1024 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
1025 /// used to compute a forward dominator frontiers.
1027 class DominanceFrontier : public DominanceFrontierBase {
1029 static char ID; // Pass ID, replacement for typeid
1030 DominanceFrontier() :
1031 DominanceFrontierBase(ID, false) {}
1033 BasicBlock *getRoot() const {
1034 assert(Roots.size() == 1 && "Should always have entry node!");
1038 virtual bool runOnFunction(Function &) {
1040 DominatorTree &DT = getAnalysis<DominatorTree>();
1041 Roots = DT.getRoots();
1042 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
1043 calculate(DT, DT[Roots[0]]);
1047 virtual void verifyAnalysis() const;
1049 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
1050 AU.setPreservesAll();
1051 AU.addRequired<DominatorTree>();
1054 /// splitBlock - BB is split and now it has one successor. Update dominance
1055 /// frontier to reflect this change.
1056 void splitBlock(BasicBlock *BB);
1058 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier
1059 /// to reflect this change.
1060 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB,
1061 DominatorTree *DT) {
1062 // NewBB is now dominating BB. Which means BB's dominance
1063 // frontier is now part of NewBB's dominance frontier. However, BB
1064 // itself is not member of NewBB's dominance frontier.
1065 DominanceFrontier::iterator NewDFI = find(NewBB);
1066 DominanceFrontier::iterator DFI = find(BB);
1067 // If BB was an entry block then its frontier is empty.
1070 DominanceFrontier::DomSetType BBSet = DFI->second;
1071 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
1072 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {
1073 BasicBlock *DFMember = *BBSetI;
1074 // Insert only if NewBB dominates DFMember.
1075 if (!DT->dominates(NewBB, DFMember))
1076 NewDFI->second.insert(DFMember);
1078 NewDFI->second.erase(BB);
1081 const DomSetType &calculate(const DominatorTree &DT,
1082 const DomTreeNode *Node);
1086 } // End llvm namespace