1 //===- GenericDomTree.h - Generic dominator trees for graphs ----*- 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 //===----------------------------------------------------------------------===//
11 /// This file defines a set of templates that efficiently compute a dominator
12 /// tree over a generic graph. This is used typically in LLVM for fast
13 /// dominance queries on the CFG, but is fully generic w.r.t. the underlying
16 //===----------------------------------------------------------------------===//
18 #ifndef LLVM_SUPPORT_GENERIC_DOM_TREE_H
19 #define LLVM_SUPPORT_GENERIC_DOM_TREE_H
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/DepthFirstIterator.h"
23 #include "llvm/ADT/GraphTraits.h"
24 #include "llvm/ADT/SmallPtrSet.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/Support/Compiler.h"
27 #include "llvm/Support/raw_ostream.h"
32 //===----------------------------------------------------------------------===//
33 /// DominatorBase - Base class that other, more interesting dominator analyses
36 template <class NodeT>
39 std::vector<NodeT*> Roots;
40 const bool IsPostDominators;
41 inline explicit DominatorBase(bool isPostDom) :
42 Roots(), IsPostDominators(isPostDom) {}
45 /// getRoots - Return the root blocks of the current CFG. This may include
46 /// multiple blocks if we are computing post dominators. For forward
47 /// dominators, this will always be a single block (the entry node).
49 inline const std::vector<NodeT*> &getRoots() const { return Roots; }
51 /// isPostDominator - Returns true if analysis based of postdoms
53 bool isPostDominator() const { return IsPostDominators; }
57 //===----------------------------------------------------------------------===//
58 // DomTreeNodeBase - Dominator Tree Node
59 template<class NodeT> class DominatorTreeBase;
60 struct PostDominatorTree;
62 template <class NodeT>
63 class DomTreeNodeBase {
65 DomTreeNodeBase<NodeT> *IDom;
66 std::vector<DomTreeNodeBase<NodeT> *> Children;
67 mutable int DFSNumIn, DFSNumOut;
69 template<class N> friend class DominatorTreeBase;
70 friend struct PostDominatorTree;
72 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator;
73 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator
76 iterator begin() { return Children.begin(); }
77 iterator end() { return Children.end(); }
78 const_iterator begin() const { return Children.begin(); }
79 const_iterator end() const { return Children.end(); }
81 NodeT *getBlock() const { return TheBB; }
82 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; }
83 const std::vector<DomTreeNodeBase<NodeT>*> &getChildren() const {
87 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom)
88 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { }
90 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) {
91 Children.push_back(C);
95 size_t getNumChildren() const {
96 return Children.size();
99 void clearAllChildren() {
103 bool compare(const DomTreeNodeBase<NodeT> *Other) const {
104 if (getNumChildren() != Other->getNumChildren())
107 SmallPtrSet<const NodeT *, 4> OtherChildren;
108 for (const_iterator I = Other->begin(), E = Other->end(); I != E; ++I) {
109 const NodeT *Nd = (*I)->getBlock();
110 OtherChildren.insert(Nd);
113 for (const_iterator I = begin(), E = end(); I != E; ++I) {
114 const NodeT *N = (*I)->getBlock();
115 if (OtherChildren.count(N) == 0)
121 void setIDom(DomTreeNodeBase<NodeT> *NewIDom) {
122 assert(IDom && "No immediate dominator?");
123 if (IDom != NewIDom) {
124 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
125 std::find(IDom->Children.begin(), IDom->Children.end(), this);
126 assert(I != IDom->Children.end() &&
127 "Not in immediate dominator children set!");
128 // I am no longer your child...
129 IDom->Children.erase(I);
131 // Switch to new dominator
133 IDom->Children.push_back(this);
137 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
139 unsigned getDFSNumIn() const { return DFSNumIn; }
140 unsigned getDFSNumOut() const { return DFSNumOut; }
142 // Return true if this node is dominated by other. Use this only if DFS info
144 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const {
145 return this->DFSNumIn >= other->DFSNumIn &&
146 this->DFSNumOut <= other->DFSNumOut;
150 template<class NodeT>
151 inline raw_ostream &operator<<(raw_ostream &o,
152 const DomTreeNodeBase<NodeT> *Node) {
153 if (Node->getBlock())
154 Node->getBlock()->printAsOperand(o, false);
156 o << " <<exit node>>";
158 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}";
163 template<class NodeT>
164 inline void PrintDomTree(const DomTreeNodeBase<NodeT> *N, raw_ostream &o,
166 o.indent(2*Lev) << "[" << Lev << "] " << N;
167 for (typename DomTreeNodeBase<NodeT>::const_iterator I = N->begin(),
168 E = N->end(); I != E; ++I)
169 PrintDomTree<NodeT>(*I, o, Lev+1);
172 //===----------------------------------------------------------------------===//
173 /// DominatorTree - Calculate the immediate dominator tree for a function.
176 template<class FuncT, class N>
177 void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
180 template<class NodeT>
181 class DominatorTreeBase : public DominatorBase<NodeT> {
182 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
183 const DomTreeNodeBase<NodeT> *B) const {
185 assert(isReachableFromEntry(B));
186 assert(isReachableFromEntry(A));
188 const DomTreeNodeBase<NodeT> *IDom;
189 while ((IDom = B->getIDom()) != nullptr && IDom != A && IDom != B)
190 B = IDom; // Walk up the tree
191 return IDom != nullptr;
195 typedef DenseMap<NodeT*, DomTreeNodeBase<NodeT>*> DomTreeNodeMapType;
196 DomTreeNodeMapType DomTreeNodes;
197 DomTreeNodeBase<NodeT> *RootNode;
199 mutable bool DFSInfoValid;
200 mutable unsigned int SlowQueries;
201 // Information record used during immediate dominators computation.
208 InfoRec() : DFSNum(0), Parent(0), Semi(0), Label(nullptr) {}
211 DenseMap<NodeT*, NodeT*> IDoms;
213 // Vertex - Map the DFS number to the NodeT*
214 std::vector<NodeT*> Vertex;
216 // Info - Collection of information used during the computation of idoms.
217 DenseMap<NodeT*, InfoRec> Info;
220 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(),
221 E = DomTreeNodes.end(); I != E; ++I)
223 DomTreeNodes.clear();
230 // NewBB is split and now it has one successor. Update dominator tree to
231 // reflect this change.
232 template<class N, class GraphT>
233 void Split(DominatorTreeBase<typename GraphT::NodeType>& DT,
234 typename GraphT::NodeType* NewBB) {
235 assert(std::distance(GraphT::child_begin(NewBB),
236 GraphT::child_end(NewBB)) == 1 &&
237 "NewBB should have a single successor!");
238 typename GraphT::NodeType* NewBBSucc = *GraphT::child_begin(NewBB);
240 std::vector<typename GraphT::NodeType*> PredBlocks;
241 typedef GraphTraits<Inverse<N> > InvTraits;
242 for (typename InvTraits::ChildIteratorType PI =
243 InvTraits::child_begin(NewBB),
244 PE = InvTraits::child_end(NewBB); PI != PE; ++PI)
245 PredBlocks.push_back(*PI);
247 assert(!PredBlocks.empty() && "No predblocks?");
249 bool NewBBDominatesNewBBSucc = true;
250 for (typename InvTraits::ChildIteratorType PI =
251 InvTraits::child_begin(NewBBSucc),
252 E = InvTraits::child_end(NewBBSucc); PI != E; ++PI) {
253 typename InvTraits::NodeType *ND = *PI;
254 if (ND != NewBB && !DT.dominates(NewBBSucc, ND) &&
255 DT.isReachableFromEntry(ND)) {
256 NewBBDominatesNewBBSucc = false;
261 // Find NewBB's immediate dominator and create new dominator tree node for
263 NodeT *NewBBIDom = nullptr;
265 for (i = 0; i < PredBlocks.size(); ++i)
266 if (DT.isReachableFromEntry(PredBlocks[i])) {
267 NewBBIDom = PredBlocks[i];
271 // It's possible that none of the predecessors of NewBB are reachable;
272 // in that case, NewBB itself is unreachable, so nothing needs to be
277 for (i = i + 1; i < PredBlocks.size(); ++i) {
278 if (DT.isReachableFromEntry(PredBlocks[i]))
279 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
282 // Create the new dominator tree node... and set the idom of NewBB.
283 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
285 // If NewBB strictly dominates other blocks, then it is now the immediate
286 // dominator of NewBBSucc. Update the dominator tree as appropriate.
287 if (NewBBDominatesNewBBSucc) {
288 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc);
289 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
294 explicit DominatorTreeBase(bool isPostDom)
295 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
296 virtual ~DominatorTreeBase() { reset(); }
298 /// compare - Return false if the other dominator tree base matches this
299 /// dominator tree base. Otherwise return true.
300 bool compare(const DominatorTreeBase &Other) const {
302 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
303 if (DomTreeNodes.size() != OtherDomTreeNodes.size())
306 for (typename DomTreeNodeMapType::const_iterator
307 I = this->DomTreeNodes.begin(),
308 E = this->DomTreeNodes.end(); I != E; ++I) {
309 NodeT *BB = I->first;
310 typename DomTreeNodeMapType::const_iterator OI = OtherDomTreeNodes.find(BB);
311 if (OI == OtherDomTreeNodes.end())
314 DomTreeNodeBase<NodeT>* MyNd = I->second;
315 DomTreeNodeBase<NodeT>* OtherNd = OI->second;
317 if (MyNd->compare(OtherNd))
324 virtual void releaseMemory() { reset(); }
326 /// getNode - return the (Post)DominatorTree node for the specified basic
327 /// block. This is the same as using operator[] on this class.
329 inline DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
330 return DomTreeNodes.lookup(BB);
333 /// getRootNode - This returns the entry node for the CFG of the function. If
334 /// this tree represents the post-dominance relations for a function, however,
335 /// this root may be a node with the block == NULL. This is the case when
336 /// there are multiple exit nodes from a particular function. Consumers of
337 /// post-dominance information must be capable of dealing with this
340 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
341 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
343 /// Get all nodes dominated by R, including R itself.
344 void getDescendants(NodeT *R, SmallVectorImpl<NodeT *> &Result) const {
346 const DomTreeNodeBase<NodeT> *RN = getNode(R);
348 return; // If R is unreachable, it will not be present in the DOM tree.
349 SmallVector<const DomTreeNodeBase<NodeT> *, 8> WL;
352 while (!WL.empty()) {
353 const DomTreeNodeBase<NodeT> *N = WL.pop_back_val();
354 Result.push_back(N->getBlock());
355 WL.append(N->begin(), N->end());
359 /// properlyDominates - Returns true iff A dominates B and A != B.
360 /// Note that this is not a constant time operation!
362 bool properlyDominates(const DomTreeNodeBase<NodeT> *A,
363 const DomTreeNodeBase<NodeT> *B) const {
368 return dominates(A, B);
371 bool properlyDominates(const NodeT *A, const NodeT *B) const;
373 /// isReachableFromEntry - Return true if A is dominated by the entry
374 /// block of the function containing it.
375 bool isReachableFromEntry(const NodeT* A) const {
376 assert(!this->isPostDominator() &&
377 "This is not implemented for post dominators");
378 return isReachableFromEntry(getNode(const_cast<NodeT *>(A)));
381 inline bool isReachableFromEntry(const DomTreeNodeBase<NodeT> *A) const {
385 /// dominates - Returns true iff A dominates B. Note that this is not a
386 /// constant time operation!
388 inline bool dominates(const DomTreeNodeBase<NodeT> *A,
389 const DomTreeNodeBase<NodeT> *B) const {
390 // A node trivially dominates itself.
394 // An unreachable node is dominated by anything.
395 if (!isReachableFromEntry(B))
398 // And dominates nothing.
399 if (!isReachableFromEntry(A))
402 // Compare the result of the tree walk and the dfs numbers, if expensive
403 // checks are enabled.
405 assert((!DFSInfoValid ||
406 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) &&
407 "Tree walk disagrees with dfs numbers!");
411 return B->DominatedBy(A);
413 // If we end up with too many slow queries, just update the
414 // DFS numbers on the theory that we are going to keep querying.
416 if (SlowQueries > 32) {
418 return B->DominatedBy(A);
421 return dominatedBySlowTreeWalk(A, B);
424 bool dominates(const NodeT *A, const NodeT *B) const;
426 NodeT *getRoot() const {
427 assert(this->Roots.size() == 1 && "Should always have entry node!");
428 return this->Roots[0];
431 /// findNearestCommonDominator - Find nearest common dominator basic block
432 /// for basic block A and B. If there is no such block then return NULL.
433 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
434 assert(A->getParent() == B->getParent() &&
435 "Two blocks are not in same function");
437 // If either A or B is a entry block then it is nearest common dominator
438 // (for forward-dominators).
439 if (!this->isPostDominator()) {
440 NodeT &Entry = A->getParent()->front();
441 if (A == &Entry || B == &Entry)
445 // If B dominates A then B is nearest common dominator.
449 // If A dominates B then A is nearest common dominator.
453 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
454 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
456 // Collect NodeA dominators set.
457 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms;
458 NodeADoms.insert(NodeA);
459 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
461 NodeADoms.insert(IDomA);
462 IDomA = IDomA->getIDom();
465 // Walk NodeB immediate dominators chain and find common dominator node.
466 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
468 if (NodeADoms.count(IDomB) != 0)
469 return IDomB->getBlock();
471 IDomB = IDomB->getIDom();
477 const NodeT *findNearestCommonDominator(const NodeT *A, const NodeT *B) {
478 // Cast away the const qualifiers here. This is ok since
479 // const is re-introduced on the return type.
480 return findNearestCommonDominator(const_cast<NodeT *>(A),
481 const_cast<NodeT *>(B));
484 //===--------------------------------------------------------------------===//
485 // API to update (Post)DominatorTree information based on modifications to
488 /// addNewBlock - Add a new node to the dominator tree information. This
489 /// creates a new node as a child of DomBB dominator node,linking it into
490 /// the children list of the immediate dominator.
491 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
492 assert(getNode(BB) == 0 && "Block already in dominator tree!");
493 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
494 assert(IDomNode && "Not immediate dominator specified for block!");
495 DFSInfoValid = false;
496 return DomTreeNodes[BB] =
497 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
500 /// changeImmediateDominator - This method is used to update the dominator
501 /// tree information when a node's immediate dominator changes.
503 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
504 DomTreeNodeBase<NodeT> *NewIDom) {
505 assert(N && NewIDom && "Cannot change null node pointers!");
506 DFSInfoValid = false;
510 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
511 changeImmediateDominator(getNode(BB), getNode(NewBB));
514 /// eraseNode - Removes a node from the dominator tree. Block must not
515 /// dominate any other blocks. Removes node from its immediate dominator's
516 /// children list. Deletes dominator node associated with basic block BB.
517 void eraseNode(NodeT *BB) {
518 DomTreeNodeBase<NodeT> *Node = getNode(BB);
519 assert(Node && "Removing node that isn't in dominator tree.");
520 assert(Node->getChildren().empty() && "Node is not a leaf node.");
522 // Remove node from immediate dominator's children list.
523 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
525 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
526 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
527 assert(I != IDom->Children.end() &&
528 "Not in immediate dominator children set!");
529 // I am no longer your child...
530 IDom->Children.erase(I);
533 DomTreeNodes.erase(BB);
537 /// removeNode - Removes a node from the dominator tree. Block must not
538 /// dominate any other blocks. Invalidates any node pointing to removed
540 void removeNode(NodeT *BB) {
541 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
542 DomTreeNodes.erase(BB);
545 /// splitBlock - BB is split and now it has one successor. Update dominator
546 /// tree to reflect this change.
547 void splitBlock(NodeT* NewBB) {
548 if (this->IsPostDominators)
549 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB);
551 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB);
554 /// print - Convert to human readable form
556 void print(raw_ostream &o) const {
557 o << "=============================--------------------------------\n";
558 if (this->isPostDominator())
559 o << "Inorder PostDominator Tree: ";
561 o << "Inorder Dominator Tree: ";
562 if (!this->DFSInfoValid)
563 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
566 // The postdom tree can have a null root if there are no returns.
568 PrintDomTree<NodeT>(getRootNode(), o, 1);
572 template<class GraphT>
573 friend typename GraphT::NodeType* Eval(
574 DominatorTreeBase<typename GraphT::NodeType>& DT,
575 typename GraphT::NodeType* V,
576 unsigned LastLinked);
578 template<class GraphT>
579 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
580 typename GraphT::NodeType* V,
583 template<class FuncT, class N>
584 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
587 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
588 /// dominator tree in dfs order.
589 void updateDFSNumbers() const {
592 SmallVector<std::pair<const DomTreeNodeBase<NodeT>*,
593 typename DomTreeNodeBase<NodeT>::const_iterator>, 32> WorkStack;
595 const DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
600 // Even in the case of multiple exits that form the post dominator root
601 // nodes, do not iterate over all exits, but start from the virtual root
602 // node. Otherwise bbs, that are not post dominated by any exit but by the
603 // virtual root node, will never be assigned a DFS number.
604 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
605 ThisRoot->DFSNumIn = DFSNum++;
607 while (!WorkStack.empty()) {
608 const DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
609 typename DomTreeNodeBase<NodeT>::const_iterator ChildIt =
610 WorkStack.back().second;
612 // If we visited all of the children of this node, "recurse" back up the
613 // stack setting the DFOutNum.
614 if (ChildIt == Node->end()) {
615 Node->DFSNumOut = DFSNum++;
616 WorkStack.pop_back();
618 // Otherwise, recursively visit this child.
619 const DomTreeNodeBase<NodeT> *Child = *ChildIt;
620 ++WorkStack.back().second;
622 WorkStack.push_back(std::make_pair(Child, Child->begin()));
623 Child->DFSNumIn = DFSNum++;
631 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
632 if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
635 // Haven't calculated this node yet? Get or calculate the node for the
636 // immediate dominator.
637 NodeT *IDom = getIDom(BB);
639 assert(IDom || this->DomTreeNodes[NULL]);
640 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
642 // Add a new tree node for this NodeT, and link it as a child of
644 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
645 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
648 inline NodeT *getIDom(NodeT *BB) const {
649 return IDoms.lookup(BB);
652 inline void addRoot(NodeT* BB) {
653 this->Roots.push_back(BB);
657 /// recalculate - compute a dominator tree for the given function
659 void recalculate(FT& F) {
660 typedef GraphTraits<FT*> TraitsTy;
662 this->Vertex.push_back(nullptr);
664 if (!this->IsPostDominators) {
666 NodeT *entry = TraitsTy::getEntryNode(&F);
667 this->Roots.push_back(entry);
668 this->IDoms[entry] = nullptr;
669 this->DomTreeNodes[entry] = nullptr;
671 Calculate<FT, NodeT*>(*this, F);
673 // Initialize the roots list
674 for (typename TraitsTy::nodes_iterator I = TraitsTy::nodes_begin(&F),
675 E = TraitsTy::nodes_end(&F); I != E; ++I) {
676 if (TraitsTy::child_begin(I) == TraitsTy::child_end(I))
679 // Prepopulate maps so that we don't get iterator invalidation issues later.
680 this->IDoms[I] = nullptr;
681 this->DomTreeNodes[I] = nullptr;
684 Calculate<FT, Inverse<NodeT*> >(*this, F);
689 // These two functions are declared out of line as a workaround for building
690 // with old (< r147295) versions of clang because of pr11642.
691 template<class NodeT>
692 bool DominatorTreeBase<NodeT>::dominates(const NodeT *A, const NodeT *B) const {
696 // Cast away the const qualifiers here. This is ok since
697 // this function doesn't actually return the values returned
699 return dominates(getNode(const_cast<NodeT *>(A)),
700 getNode(const_cast<NodeT *>(B)));
702 template<class NodeT>
704 DominatorTreeBase<NodeT>::properlyDominates(const NodeT *A, const NodeT *B) const {
708 // Cast away the const qualifiers here. This is ok since
709 // this function doesn't actually return the values returned
711 return dominates(getNode(const_cast<NodeT *>(A)),
712 getNode(const_cast<NodeT *>(B)));