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/BasicBlock.h"
26 #include "llvm/Function.h"
27 #include "llvm/Instruction.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/ADT/DenseMap.h"
30 #include "llvm/ADT/GraphTraits.h"
31 #include "llvm/ADT/SmallPtrSet.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/Assembly/Writer.h"
34 #include "llvm/Support/CFG.h"
35 #include "llvm/Support/Compiler.h"
41 //===----------------------------------------------------------------------===//
42 /// DominatorBase - Base class that other, more interesting dominator analyses
45 template <class NodeT>
48 std::vector<NodeT*> Roots;
49 const bool IsPostDominators;
50 inline DominatorBase(bool isPostDom) :
51 Roots(), IsPostDominators(isPostDom) {}
54 /// getRoots - Return the root blocks of the current CFG. This may include
55 /// multiple blocks if we are computing post dominators. For forward
56 /// dominators, this will always be a single block (the entry node).
58 inline const std::vector<NodeT*> &getRoots() const { return Roots; }
60 /// isPostDominator - Returns true if analysis based of postdoms
62 bool isPostDominator() const { return IsPostDominators; }
66 //===----------------------------------------------------------------------===//
67 // DomTreeNode - Dominator Tree Node
68 template<class NodeT> class DominatorTreeBase;
69 struct PostDominatorTree;
70 class MachineBasicBlock;
72 template <class NodeT>
73 class DomTreeNodeBase {
75 DomTreeNodeBase<NodeT> *IDom;
76 std::vector<DomTreeNodeBase<NodeT> *> Children;
77 int DFSNumIn, DFSNumOut;
79 template<class N> friend class DominatorTreeBase;
80 friend struct PostDominatorTree;
82 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator;
83 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator
86 iterator begin() { return Children.begin(); }
87 iterator end() { return Children.end(); }
88 const_iterator begin() const { return Children.begin(); }
89 const_iterator end() const { return Children.end(); }
91 NodeT *getBlock() const { return TheBB; }
92 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; }
93 const std::vector<DomTreeNodeBase<NodeT>*> &getChildren() const {
97 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom)
98 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { }
100 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) {
101 Children.push_back(C);
105 void setIDom(DomTreeNodeBase<NodeT> *NewIDom) {
106 assert(IDom && "No immediate dominator?");
107 if (IDom != NewIDom) {
108 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
109 std::find(IDom->Children.begin(), IDom->Children.end(), this);
110 assert(I != IDom->Children.end() &&
111 "Not in immediate dominator children set!");
112 // I am no longer your child...
113 IDom->Children.erase(I);
115 // Switch to new dominator
117 IDom->Children.push_back(this);
121 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
123 unsigned getDFSNumIn() const { return DFSNumIn; }
124 unsigned getDFSNumOut() const { return DFSNumOut; }
126 // Return true if this node is dominated by other. Use this only if DFS info
128 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const {
129 return this->DFSNumIn >= other->DFSNumIn &&
130 this->DFSNumOut <= other->DFSNumOut;
134 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<BasicBlock>);
135 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<MachineBasicBlock>);
137 template<class NodeT>
138 static std::ostream &operator<<(std::ostream &o,
139 const DomTreeNodeBase<NodeT> *Node) {
140 if (Node->getBlock())
141 WriteAsOperand(o, Node->getBlock(), false);
143 o << " <<exit node>>";
145 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}";
150 template<class NodeT>
151 static void PrintDomTree(const DomTreeNodeBase<NodeT> *N, std::ostream &o,
153 o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
154 for (typename DomTreeNodeBase<NodeT>::const_iterator I = N->begin(),
155 E = N->end(); I != E; ++I)
156 PrintDomTree<NodeT>(*I, o, Lev+1);
159 typedef DomTreeNodeBase<BasicBlock> DomTreeNode;
161 //===----------------------------------------------------------------------===//
162 /// DominatorTree - Calculate the immediate dominator tree for a function.
165 template<class FuncT, class N>
166 void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
169 template<class NodeT>
170 class DominatorTreeBase : public DominatorBase<NodeT> {
172 typedef DenseMap<NodeT*, DomTreeNodeBase<NodeT>*> DomTreeNodeMapType;
173 DomTreeNodeMapType DomTreeNodes;
174 DomTreeNodeBase<NodeT> *RootNode;
177 unsigned int SlowQueries;
178 // Information record used during immediate dominators computation.
182 NodeT *Label, *Parent, *Child, *Ancestor;
184 std::vector<NodeT*> Bucket;
186 InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0) {}
189 DenseMap<NodeT*, NodeT*> IDoms;
191 // Vertex - Map the DFS number to the BasicBlock*
192 std::vector<NodeT*> Vertex;
194 // Info - Collection of information used during the computation of idoms.
195 DenseMap<NodeT*, InfoRec> Info;
198 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(),
199 E = DomTreeNodes.end(); I != E; ++I)
201 DomTreeNodes.clear();
208 // NewBB is split and now it has one successor. Update dominator tree to
209 // reflect this change.
210 template<class N, class GraphT>
211 void Split(DominatorTreeBase<typename GraphT::NodeType>& DT,
212 typename GraphT::NodeType* NewBB) {
213 assert(std::distance(GraphT::child_begin(NewBB), GraphT::child_end(NewBB)) == 1
214 && "NewBB should have a single successor!");
215 typename GraphT::NodeType* NewBBSucc = *GraphT::child_begin(NewBB);
217 std::vector<typename GraphT::NodeType*> PredBlocks;
218 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI =
219 GraphTraits<Inverse<N> >::child_begin(NewBB),
220 PE = GraphTraits<Inverse<N> >::child_end(NewBB); PI != PE; ++PI)
221 PredBlocks.push_back(*PI);
223 assert(!PredBlocks.empty() && "No predblocks??");
225 // The newly inserted basic block will dominate existing basic blocks iff the
226 // PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
227 // the non-pred blocks, then they all must be the same block!
229 bool NewBBDominatesNewBBSucc = true;
231 typename GraphT::NodeType* OnePred = PredBlocks[0];
232 unsigned i = 1, e = PredBlocks.size();
233 for (i = 1; !DT.isReachableFromEntry(OnePred); ++i) {
234 assert(i != e && "Didn't find reachable pred?");
235 OnePred = PredBlocks[i];
239 if (PredBlocks[i] != OnePred && DT.isReachableFromEntry(OnePred)) {
240 NewBBDominatesNewBBSucc = false;
244 if (NewBBDominatesNewBBSucc)
245 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI =
246 GraphTraits<Inverse<N> >::child_begin(NewBBSucc),
247 E = GraphTraits<Inverse<N> >::child_end(NewBBSucc); PI != E; ++PI)
248 if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
249 NewBBDominatesNewBBSucc = false;
254 // The other scenario where the new block can dominate its successors are when
255 // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
257 if (!NewBBDominatesNewBBSucc) {
258 NewBBDominatesNewBBSucc = true;
259 for (typename GraphTraits<Inverse<N> >::ChildIteratorType PI =
260 GraphTraits<Inverse<N> >::child_begin(NewBBSucc),
261 E = GraphTraits<Inverse<N> >::child_end(NewBBSucc); PI != E; ++PI)
262 if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
263 NewBBDominatesNewBBSucc = false;
268 // Find NewBB's immediate dominator and create new dominator tree node for
270 NodeT *NewBBIDom = 0;
272 for (i = 0; i < PredBlocks.size(); ++i)
273 if (DT.isReachableFromEntry(PredBlocks[i])) {
274 NewBBIDom = PredBlocks[i];
277 assert(i != PredBlocks.size() && "No reachable preds?");
278 for (i = i + 1; i < PredBlocks.size(); ++i) {
279 if (DT.isReachableFromEntry(PredBlocks[i]))
280 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
282 assert(NewBBIDom && "No immediate dominator found??");
284 // Create the new dominator tree node... and set the idom of NewBB.
285 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
287 // If NewBB strictly dominates other blocks, then it is now the immediate
288 // dominator of NewBBSucc. Update the dominator tree as appropriate.
289 if (NewBBDominatesNewBBSucc) {
290 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc);
291 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
296 DominatorTreeBase(bool isPostDom)
297 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
298 virtual ~DominatorTreeBase() { reset(); }
300 // FIXME: Should remove this
301 virtual bool runOnFunction(Function &F) { return false; }
303 /// isAnalysis - Return true if this pass is implementing an analysis pass.
304 virtual bool isAnalysis() const { return true; }
306 virtual void releaseMemory() { reset(); }
308 /// getNode - return the (Post)DominatorTree node for the specified basic
309 /// block. This is the same as using operator[] on this class.
311 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
312 typename DomTreeNodeMapType::const_iterator I = DomTreeNodes.find(BB);
313 return I != DomTreeNodes.end() ? I->second : 0;
316 /// getRootNode - This returns the entry node for the CFG of the function. If
317 /// this tree represents the post-dominance relations for a function, however,
318 /// this root may be a node with the block == NULL. This is the case when
319 /// there are multiple exit nodes from a particular function. Consumers of
320 /// post-dominance information must be capable of dealing with this
323 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
324 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
326 /// properlyDominates - Returns true iff this dominates N and this != N.
327 /// Note that this is not a constant time operation!
329 bool properlyDominates(const DomTreeNodeBase<NodeT> *A,
330 DomTreeNodeBase<NodeT> *B) const {
331 if (A == 0 || B == 0) return false;
332 return dominatedBySlowTreeWalk(A, B);
335 inline bool properlyDominates(NodeT *A, NodeT *B) {
336 return properlyDominates(getNode(A), getNode(B));
339 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
340 const DomTreeNodeBase<NodeT> *B) const {
341 const DomTreeNodeBase<NodeT> *IDom;
342 if (A == 0 || B == 0) return false;
343 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B)
344 B = IDom; // Walk up the tree
349 /// isReachableFromEntry - Return true if A is dominated by the entry
350 /// block of the function containing it.
351 bool isReachableFromEntry(NodeT* A) {
352 assert (!this->isPostDominator()
353 && "This is not implemented for post dominators");
354 return dominates(&A->getParent()->front(), A);
357 /// dominates - Returns true iff A dominates B. Note that this is not a
358 /// constant time operation!
360 inline bool dominates(const DomTreeNodeBase<NodeT> *A,
361 DomTreeNodeBase<NodeT> *B) {
363 return true; // A node trivially dominates itself.
365 if (A == 0 || B == 0)
369 return B->DominatedBy(A);
371 // If we end up with too many slow queries, just update the
372 // DFS numbers on the theory that we are going to keep querying.
374 if (SlowQueries > 32) {
376 return B->DominatedBy(A);
379 return dominatedBySlowTreeWalk(A, B);
382 inline bool dominates(NodeT *A, NodeT *B) {
386 return dominates(getNode(A), getNode(B));
389 NodeT *getRoot() const {
390 assert(this->Roots.size() == 1 && "Should always have entry node!");
391 return this->Roots[0];
394 /// findNearestCommonDominator - Find nearest common dominator basic block
395 /// for basic block A and B. If there is no such block then return NULL.
396 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
398 assert (!this->isPostDominator()
399 && "This is not implemented for post dominators");
400 assert (A->getParent() == B->getParent()
401 && "Two blocks are not in same function");
403 // If either A or B is a entry block then it is nearest common dominator.
404 NodeT &Entry = A->getParent()->front();
405 if (A == &Entry || B == &Entry)
408 // If B dominates A then B is nearest common dominator.
412 // If A dominates B then A is nearest common dominator.
416 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
417 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
419 // Collect NodeA dominators set.
420 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms;
421 NodeADoms.insert(NodeA);
422 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
424 NodeADoms.insert(IDomA);
425 IDomA = IDomA->getIDom();
428 // Walk NodeB immediate dominators chain and find common dominator node.
429 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
431 if (NodeADoms.count(IDomB) != 0)
432 return IDomB->getBlock();
434 IDomB = IDomB->getIDom();
440 //===--------------------------------------------------------------------===//
441 // API to update (Post)DominatorTree information based on modifications to
444 /// addNewBlock - Add a new node to the dominator tree information. This
445 /// creates a new node as a child of DomBB dominator node,linking it into
446 /// the children list of the immediate dominator.
447 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
448 assert(getNode(BB) == 0 && "Block already in dominator tree!");
449 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
450 assert(IDomNode && "Not immediate dominator specified for block!");
451 DFSInfoValid = false;
452 return DomTreeNodes[BB] =
453 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
456 /// changeImmediateDominator - This method is used to update the dominator
457 /// tree information when a node's immediate dominator changes.
459 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
460 DomTreeNodeBase<NodeT> *NewIDom) {
461 assert(N && NewIDom && "Cannot change null node pointers!");
462 DFSInfoValid = false;
466 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
467 changeImmediateDominator(getNode(BB), getNode(NewBB));
470 /// eraseNode - Removes a node from the dominator tree. Block must not
471 /// domiante any other blocks. Removes node from its immediate dominator's
472 /// children list. Deletes dominator node associated with basic block BB.
473 void eraseNode(NodeT *BB) {
474 DomTreeNodeBase<NodeT> *Node = getNode(BB);
475 assert (Node && "Removing node that isn't in dominator tree.");
476 assert (Node->getChildren().empty() && "Node is not a leaf node.");
478 // Remove node from immediate dominator's children list.
479 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
481 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
482 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
483 assert(I != IDom->Children.end() &&
484 "Not in immediate dominator children set!");
485 // I am no longer your child...
486 IDom->Children.erase(I);
489 DomTreeNodes.erase(BB);
493 /// removeNode - Removes a node from the dominator tree. Block must not
494 /// dominate any other blocks. Invalidates any node pointing to removed
496 void removeNode(NodeT *BB) {
497 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
498 DomTreeNodes.erase(BB);
501 /// splitBlock - BB is split and now it has one successor. Update dominator
502 /// tree to reflect this change.
503 void splitBlock(NodeT* NewBB) {
504 if (this->IsPostDominators)
505 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB);
507 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB);
510 /// print - Convert to human readable form
512 virtual void print(std::ostream &o, const Module* ) const {
513 o << "=============================--------------------------------\n";
514 if (this->isPostDominator())
515 o << "Inorder PostDominator Tree: ";
517 o << "Inorder Dominator Tree: ";
518 if (this->DFSInfoValid)
519 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
522 PrintDomTree<NodeT>(getRootNode(), o, 1);
525 void print(std::ostream *OS, const Module* M = 0) const {
526 if (OS) print(*OS, M);
529 virtual void dump() {
534 template<class GraphT>
535 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
536 typename GraphT::NodeType* VIn);
538 template<class GraphT>
539 friend typename GraphT::NodeType* Eval(
540 DominatorTreeBase<typename GraphT::NodeType>& DT,
541 typename GraphT::NodeType* V);
543 template<class GraphT>
544 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
545 typename GraphT::NodeType* V,
546 typename GraphT::NodeType* W,
547 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo);
549 template<class GraphT>
550 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
551 typename GraphT::NodeType* V,
554 template<class FuncT, class N>
555 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
558 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
559 /// dominator tree in dfs order.
560 void updateDFSNumbers() {
563 SmallVector<std::pair<DomTreeNodeBase<NodeT>*,
564 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack;
566 for (unsigned i = 0, e = this->Roots.size(); i != e; ++i) {
567 DomTreeNodeBase<NodeT> *ThisRoot = getNode(this->Roots[i]);
568 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
569 ThisRoot->DFSNumIn = DFSNum++;
571 while (!WorkStack.empty()) {
572 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
573 typename DomTreeNodeBase<NodeT>::iterator ChildIt =
574 WorkStack.back().second;
576 // If we visited all of the children of this node, "recurse" back up the
577 // stack setting the DFOutNum.
578 if (ChildIt == Node->end()) {
579 Node->DFSNumOut = DFSNum++;
580 WorkStack.pop_back();
582 // Otherwise, recursively visit this child.
583 DomTreeNodeBase<NodeT> *Child = *ChildIt;
584 ++WorkStack.back().second;
586 WorkStack.push_back(std::make_pair(Child, Child->begin()));
587 Child->DFSNumIn = DFSNum++;
596 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
597 if (DomTreeNodeBase<NodeT> *BBNode = this->DomTreeNodes[BB])
600 // Haven't calculated this node yet? Get or calculate the node for the
601 // immediate dominator.
602 NodeT *IDom = getIDom(BB);
603 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
605 // Add a new tree node for this BasicBlock, and link it as a child of
607 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
608 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
611 inline NodeT *getIDom(NodeT *BB) const {
612 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB);
613 return I != IDoms.end() ? I->second : 0;
616 inline void addRoot(NodeT* BB) {
617 // Unreachable block is not a root node.
618 if (!isa<UnreachableInst>(&BB->back()))
619 this->Roots.push_back(BB);
623 /// recalculate - compute a dominator tree for the given function
625 void recalculate(FT& F) {
626 if (!this->IsPostDominators) {
630 this->Roots.push_back(&F.front());
631 this->IDoms[&F.front()] = 0;
632 this->DomTreeNodes[&F.front()] = 0;
633 this->Vertex.push_back(0);
635 Calculate<FT, NodeT*>(*this, F);
639 reset(); // Reset from the last time we were run...
641 // Initialize the roots list
642 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) {
643 if (std::distance(GraphTraits<FT*>::child_begin(I),
644 GraphTraits<FT*>::child_end(I)) == 0)
647 // Prepopulate maps so that we don't get iterator invalidation issues later.
649 this->DomTreeNodes[I] = 0;
652 this->Vertex.push_back(0);
654 Calculate<FT, Inverse<NodeT*> >(*this, F);
659 EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
661 //===-------------------------------------
662 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
663 /// compute a normal dominator tree.
665 class DominatorTree : public FunctionPass {
667 static char ID; // Pass ID, replacement for typeid
668 DominatorTreeBase<BasicBlock>* DT;
670 DominatorTree() : FunctionPass(intptr_t(&ID)) {
671 DT = new DominatorTreeBase<BasicBlock>(false);
679 DominatorTreeBase<BasicBlock>& getBase() { return *DT; }
681 /// getRoots - Return the root blocks of the current CFG. This may include
682 /// multiple blocks if we are computing post dominators. For forward
683 /// dominators, this will always be a single block (the entry node).
685 inline const std::vector<BasicBlock*> &getRoots() const {
686 return DT->getRoots();
689 inline BasicBlock *getRoot() const {
690 return DT->getRoot();
693 inline DomTreeNode *getRootNode() const {
694 return DT->getRootNode();
697 /// isAnalysis - Return true if this pass is implementing an analysis pass.
698 virtual bool isAnalysis() const { return true; }
700 virtual bool runOnFunction(Function &F);
702 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
703 AU.setPreservesAll();
706 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const {
707 return DT->dominates(A, B);
710 inline bool dominates(BasicBlock* A, BasicBlock* B) const {
711 return DT->dominates(A, B);
714 // dominates - Return true if A dominates B. This performs the
715 // special checks necessary if A and B are in the same basic block.
716 bool dominates(Instruction *A, Instruction *B) const {
717 BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
718 if (BBA != BBB) return DT->dominates(BBA, BBB);
720 // It is not possible to determine dominance between two PHI nodes
721 // based on their ordering.
722 if (isa<PHINode>(A) && isa<PHINode>(B))
725 // Loop through the basic block until we find A or B.
726 BasicBlock::iterator I = BBA->begin();
727 for (; &*I != A && &*I != B; ++I) /*empty*/;
729 //if(!DT.IsPostDominators) {
730 // A dominates B if it is found first in the basic block.
733 // // A post-dominates B if B is found first in the basic block.
738 inline bool properlyDominates(const DomTreeNode* A, DomTreeNode* B) const {
739 return DT->properlyDominates(A, B);
742 inline bool properlyDominates(BasicBlock* A, BasicBlock* B) const {
743 return DT->properlyDominates(A, B);
746 /// findNearestCommonDominator - Find nearest common dominator basic block
747 /// for basic block A and B. If there is no such block then return NULL.
748 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) {
749 return DT->findNearestCommonDominator(A, B);
752 inline DomTreeNode *operator[](BasicBlock *BB) const {
753 return DT->getNode(BB);
756 /// getNode - return the (Post)DominatorTree node for the specified basic
757 /// block. This is the same as using operator[] on this class.
759 inline DomTreeNode *getNode(BasicBlock *BB) const {
760 return DT->getNode(BB);
763 /// addNewBlock - Add a new node to the dominator tree information. This
764 /// creates a new node as a child of DomBB dominator node,linking it into
765 /// the children list of the immediate dominator.
766 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
767 return DT->addNewBlock(BB, DomBB);
770 /// changeImmediateDominator - This method is used to update the dominator
771 /// tree information when a node's immediate dominator changes.
773 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) {
774 DT->changeImmediateDominator(N, NewIDom);
777 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) {
778 DT->changeImmediateDominator(N, NewIDom);
781 /// eraseNode - Removes a node from the dominator tree. Block must not
782 /// domiante any other blocks. Removes node from its immediate dominator's
783 /// children list. Deletes dominator node associated with basic block BB.
784 inline void eraseNode(BasicBlock *BB) {
788 /// splitBlock - BB is split and now it has one successor. Update dominator
789 /// tree to reflect this change.
790 inline void splitBlock(BasicBlock* NewBB) {
791 DT->splitBlock(NewBB);
795 virtual void releaseMemory() {
799 virtual void print(std::ostream &OS, const Module* M= 0) const {
804 //===-------------------------------------
805 /// DominatorTree GraphTraits specialization so the DominatorTree can be
806 /// iterable by generic graph iterators.
808 template <> struct GraphTraits<DomTreeNode *> {
809 typedef DomTreeNode NodeType;
810 typedef NodeType::iterator ChildIteratorType;
812 static NodeType *getEntryNode(NodeType *N) {
815 static inline ChildIteratorType child_begin(NodeType* N) {
818 static inline ChildIteratorType child_end(NodeType* N) {
823 template <> struct GraphTraits<DominatorTree*>
824 : public GraphTraits<DomTreeNode *> {
825 static NodeType *getEntryNode(DominatorTree *DT) {
826 return DT->getRootNode();
831 //===----------------------------------------------------------------------===//
832 /// DominanceFrontierBase - Common base class for computing forward and inverse
833 /// dominance frontiers for a function.
835 class DominanceFrontierBase : public FunctionPass {
837 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
838 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
840 DomSetMapType Frontiers;
841 std::vector<BasicBlock*> Roots;
842 const bool IsPostDominators;
845 DominanceFrontierBase(intptr_t ID, bool isPostDom)
846 : FunctionPass(ID), IsPostDominators(isPostDom) {}
848 /// getRoots - Return the root blocks of the current CFG. This may include
849 /// multiple blocks if we are computing post dominators. For forward
850 /// dominators, this will always be a single block (the entry node).
852 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
854 /// isPostDominator - Returns true if analysis based of postdoms
856 bool isPostDominator() const { return IsPostDominators; }
858 virtual void releaseMemory() { Frontiers.clear(); }
860 // Accessor interface:
861 typedef DomSetMapType::iterator iterator;
862 typedef DomSetMapType::const_iterator const_iterator;
863 iterator begin() { return Frontiers.begin(); }
864 const_iterator begin() const { return Frontiers.begin(); }
865 iterator end() { return Frontiers.end(); }
866 const_iterator end() const { return Frontiers.end(); }
867 iterator find(BasicBlock *B) { return Frontiers.find(B); }
868 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
870 void addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
871 assert(find(BB) == end() && "Block already in DominanceFrontier!");
872 Frontiers.insert(std::make_pair(BB, frontier));
875 /// removeBlock - Remove basic block BB's frontier.
876 void removeBlock(BasicBlock *BB) {
877 assert(find(BB) != end() && "Block is not in DominanceFrontier!");
878 for (iterator I = begin(), E = end(); I != E; ++I)
883 void addToFrontier(iterator I, BasicBlock *Node) {
884 assert(I != end() && "BB is not in DominanceFrontier!");
885 I->second.insert(Node);
888 void removeFromFrontier(iterator I, BasicBlock *Node) {
889 assert(I != end() && "BB is not in DominanceFrontier!");
890 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
891 I->second.erase(Node);
894 /// print - Convert to human readable form
896 virtual void print(std::ostream &OS, const Module* = 0) const;
897 void print(std::ostream *OS, const Module* M = 0) const {
898 if (OS) print(*OS, M);
904 //===-------------------------------------
905 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
906 /// used to compute a forward dominator frontiers.
908 class DominanceFrontier : public DominanceFrontierBase {
910 static char ID; // Pass ID, replacement for typeid
911 DominanceFrontier() :
912 DominanceFrontierBase(intptr_t(&ID), false) {}
914 BasicBlock *getRoot() const {
915 assert(Roots.size() == 1 && "Should always have entry node!");
919 /// isAnalysis - Return true if this pass is implementing an analysis pass.
920 virtual bool isAnalysis() const { return true; }
922 virtual bool runOnFunction(Function &) {
924 DominatorTree &DT = getAnalysis<DominatorTree>();
925 Roots = DT.getRoots();
926 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
927 calculate(DT, DT[Roots[0]]);
931 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
932 AU.setPreservesAll();
933 AU.addRequired<DominatorTree>();
936 /// splitBlock - BB is split and now it has one successor. Update dominance
937 /// frontier to reflect this change.
938 void splitBlock(BasicBlock *BB);
940 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier
941 /// to reflect this change.
942 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB,
944 // NewBB is now dominating BB. Which means BB's dominance
945 // frontier is now part of NewBB's dominance frontier. However, BB
946 // itself is not member of NewBB's dominance frontier.
947 DominanceFrontier::iterator NewDFI = find(NewBB);
948 DominanceFrontier::iterator DFI = find(BB);
949 DominanceFrontier::DomSetType BBSet = DFI->second;
950 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
951 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {
952 BasicBlock *DFMember = *BBSetI;
953 // Insert only if NewBB dominates DFMember.
954 if (!DT->dominates(NewBB, DFMember))
955 NewDFI->second.insert(DFMember);
957 NewDFI->second.erase(BB);
961 const DomSetType &calculate(const DominatorTree &DT,
962 const DomTreeNode *Node);
966 } // End llvm namespace