1 //===- GenericDomTree.h - Generic dominator trees for graphs ----*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 ///
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
14 /// graph types.
15 ///
16 //===----------------------------------------------------------------------===//
17
18 #ifndef LLVM_SUPPORT_GENERICDOMTREE_H
19 #define LLVM_SUPPORT_GENERICDOMTREE_H
20
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"
28 #include <algorithm>
29
30 namespace llvm {
31
32 /// \brief Base class that other, more interesting dominator analyses
33 /// inherit from.
34 template <class NodeT> class DominatorBase {
35 protected:
36 std::vector<NodeT *> Roots;
37 bool IsPostDominators;
DominatorBase(bool isPostDom)38 explicit DominatorBase(bool isPostDom)
39 : Roots(), IsPostDominators(isPostDom) {}
DominatorBase(DominatorBase && Arg)40 DominatorBase(DominatorBase &&Arg)
41 : Roots(std::move(Arg.Roots)),
42 IsPostDominators(std::move(Arg.IsPostDominators)) {
43 Arg.Roots.clear();
44 }
45 DominatorBase &operator=(DominatorBase &&RHS) {
46 Roots = std::move(RHS.Roots);
47 IsPostDominators = std::move(RHS.IsPostDominators);
48 RHS.Roots.clear();
49 return *this;
50 }
51
52 public:
53 /// getRoots - Return the root blocks of the current CFG. This may include
54 /// multiple blocks if we are computing post dominators. For forward
55 /// dominators, this will always be a single block (the entry node).
56 ///
getRoots()57 const std::vector<NodeT *> &getRoots() const { return Roots; }
58
59 /// isPostDominator - Returns true if analysis based of postdoms
60 ///
isPostDominator()61 bool isPostDominator() const { return IsPostDominators; }
62 };
63
64 template <class NodeT> class DominatorTreeBase;
65 struct PostDominatorTree;
66
67 /// \brief Base class for the actual dominator tree node.
68 template <class NodeT> class DomTreeNodeBase {
69 NodeT *TheBB;
70 DomTreeNodeBase<NodeT> *IDom;
71 std::vector<DomTreeNodeBase<NodeT> *> Children;
72 mutable int DFSNumIn, DFSNumOut;
73
74 template <class N> friend class DominatorTreeBase;
75 friend struct PostDominatorTree;
76
77 public:
78 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator;
79 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator
80 const_iterator;
81
begin()82 iterator begin() { return Children.begin(); }
end()83 iterator end() { return Children.end(); }
begin()84 const_iterator begin() const { return Children.begin(); }
end()85 const_iterator end() const { return Children.end(); }
86
getBlock()87 NodeT *getBlock() const { return TheBB; }
getIDom()88 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; }
getChildren()89 const std::vector<DomTreeNodeBase<NodeT> *> &getChildren() const {
90 return Children;
91 }
92
DomTreeNodeBase(NodeT * BB,DomTreeNodeBase<NodeT> * iDom)93 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom)
94 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) {}
95
addChild(DomTreeNodeBase<NodeT> * C)96 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) {
97 Children.push_back(C);
98 return C;
99 }
100
getNumChildren()101 size_t getNumChildren() const { return Children.size(); }
102
clearAllChildren()103 void clearAllChildren() { Children.clear(); }
104
compare(const DomTreeNodeBase<NodeT> * Other)105 bool compare(const DomTreeNodeBase<NodeT> *Other) const {
106 if (getNumChildren() != Other->getNumChildren())
107 return true;
108
109 SmallPtrSet<const NodeT *, 4> OtherChildren;
110 for (const_iterator I = Other->begin(), E = Other->end(); I != E; ++I) {
111 const NodeT *Nd = (*I)->getBlock();
112 OtherChildren.insert(Nd);
113 }
114
115 for (const_iterator I = begin(), E = end(); I != E; ++I) {
116 const NodeT *N = (*I)->getBlock();
117 if (OtherChildren.count(N) == 0)
118 return true;
119 }
120 return false;
121 }
122
setIDom(DomTreeNodeBase<NodeT> * NewIDom)123 void setIDom(DomTreeNodeBase<NodeT> *NewIDom) {
124 assert(IDom && "No immediate dominator?");
125 if (IDom != NewIDom) {
126 typename std::vector<DomTreeNodeBase<NodeT> *>::iterator I =
127 std::find(IDom->Children.begin(), IDom->Children.end(), this);
128 assert(I != IDom->Children.end() &&
129 "Not in immediate dominator children set!");
130 // I am no longer your child...
131 IDom->Children.erase(I);
132
133 // Switch to new dominator
134 IDom = NewIDom;
135 IDom->Children.push_back(this);
136 }
137 }
138
139 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
140 /// not call them.
getDFSNumIn()141 unsigned getDFSNumIn() const { return DFSNumIn; }
getDFSNumOut()142 unsigned getDFSNumOut() const { return DFSNumOut; }
143
144 private:
145 // Return true if this node is dominated by other. Use this only if DFS info
146 // is valid.
DominatedBy(const DomTreeNodeBase<NodeT> * other)147 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const {
148 return this->DFSNumIn >= other->DFSNumIn &&
149 this->DFSNumOut <= other->DFSNumOut;
150 }
151 };
152
153 template <class NodeT>
154 raw_ostream &operator<<(raw_ostream &o, const DomTreeNodeBase<NodeT> *Node) {
155 if (Node->getBlock())
156 Node->getBlock()->printAsOperand(o, false);
157 else
158 o << " <<exit node>>";
159
160 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}";
161
162 return o << "\n";
163 }
164
165 template <class NodeT>
PrintDomTree(const DomTreeNodeBase<NodeT> * N,raw_ostream & o,unsigned Lev)166 void PrintDomTree(const DomTreeNodeBase<NodeT> *N, raw_ostream &o,
167 unsigned Lev) {
168 o.indent(2 * Lev) << "[" << Lev << "] " << N;
169 for (typename DomTreeNodeBase<NodeT>::const_iterator I = N->begin(),
170 E = N->end();
171 I != E; ++I)
172 PrintDomTree<NodeT>(*I, o, Lev + 1);
173 }
174
175 // The calculate routine is provided in a separate header but referenced here.
176 template <class FuncT, class N>
177 void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType> &DT,
178 FuncT &F);
179
180 /// \brief Core dominator tree base class.
181 ///
182 /// This class is a generic template over graph nodes. It is instantiated for
183 /// various graphs in the LLVM IR or in the code generator.
184 template <class NodeT> class DominatorTreeBase : public DominatorBase<NodeT> {
185 DominatorTreeBase(const DominatorTreeBase &) LLVM_DELETED_FUNCTION;
186 DominatorTreeBase &operator=(const DominatorTreeBase &) LLVM_DELETED_FUNCTION;
187
dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)188 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
189 const DomTreeNodeBase<NodeT> *B) const {
190 assert(A != B);
191 assert(isReachableFromEntry(B));
192 assert(isReachableFromEntry(A));
193
194 const DomTreeNodeBase<NodeT> *IDom;
195 while ((IDom = B->getIDom()) != nullptr && IDom != A && IDom != B)
196 B = IDom; // Walk up the tree
197 return IDom != nullptr;
198 }
199
200 /// \brief Wipe this tree's state without releasing any resources.
201 ///
202 /// This is essentially a post-move helper only. It leaves the object in an
203 /// assignable and destroyable state, but otherwise invalid.
wipe()204 void wipe() {
205 DomTreeNodes.clear();
206 IDoms.clear();
207 Vertex.clear();
208 Info.clear();
209 RootNode = nullptr;
210 }
211
212 protected:
213 typedef DenseMap<NodeT *, DomTreeNodeBase<NodeT> *> DomTreeNodeMapType;
214 DomTreeNodeMapType DomTreeNodes;
215 DomTreeNodeBase<NodeT> *RootNode;
216
217 mutable bool DFSInfoValid;
218 mutable unsigned int SlowQueries;
219 // Information record used during immediate dominators computation.
220 struct InfoRec {
221 unsigned DFSNum;
222 unsigned Parent;
223 unsigned Semi;
224 NodeT *Label;
225
InfoRecInfoRec226 InfoRec() : DFSNum(0), Parent(0), Semi(0), Label(nullptr) {}
227 };
228
229 DenseMap<NodeT *, NodeT *> IDoms;
230
231 // Vertex - Map the DFS number to the NodeT*
232 std::vector<NodeT *> Vertex;
233
234 // Info - Collection of information used during the computation of idoms.
235 DenseMap<NodeT *, InfoRec> Info;
236
reset()237 void reset() {
238 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(),
239 E = DomTreeNodes.end();
240 I != E; ++I)
241 delete I->second;
242 DomTreeNodes.clear();
243 IDoms.clear();
244 this->Roots.clear();
245 Vertex.clear();
246 RootNode = nullptr;
247 }
248
249 // NewBB is split and now it has one successor. Update dominator tree to
250 // reflect this change.
251 template <class N, class GraphT>
Split(DominatorTreeBase<typename GraphT::NodeType> & DT,typename GraphT::NodeType * NewBB)252 void Split(DominatorTreeBase<typename GraphT::NodeType> &DT,
253 typename GraphT::NodeType *NewBB) {
254 assert(std::distance(GraphT::child_begin(NewBB),
255 GraphT::child_end(NewBB)) == 1 &&
256 "NewBB should have a single successor!");
257 typename GraphT::NodeType *NewBBSucc = *GraphT::child_begin(NewBB);
258
259 std::vector<typename GraphT::NodeType *> PredBlocks;
260 typedef GraphTraits<Inverse<N>> InvTraits;
261 for (typename InvTraits::ChildIteratorType
262 PI = InvTraits::child_begin(NewBB),
263 PE = InvTraits::child_end(NewBB);
264 PI != PE; ++PI)
265 PredBlocks.push_back(*PI);
266
267 assert(!PredBlocks.empty() && "No predblocks?");
268
269 bool NewBBDominatesNewBBSucc = true;
270 for (typename InvTraits::ChildIteratorType
271 PI = InvTraits::child_begin(NewBBSucc),
272 E = InvTraits::child_end(NewBBSucc);
273 PI != E; ++PI) {
274 typename InvTraits::NodeType *ND = *PI;
275 if (ND != NewBB && !DT.dominates(NewBBSucc, ND) &&
276 DT.isReachableFromEntry(ND)) {
277 NewBBDominatesNewBBSucc = false;
278 break;
279 }
280 }
281
282 // Find NewBB's immediate dominator and create new dominator tree node for
283 // NewBB.
284 NodeT *NewBBIDom = nullptr;
285 unsigned i = 0;
286 for (i = 0; i < PredBlocks.size(); ++i)
287 if (DT.isReachableFromEntry(PredBlocks[i])) {
288 NewBBIDom = PredBlocks[i];
289 break;
290 }
291
292 // It's possible that none of the predecessors of NewBB are reachable;
293 // in that case, NewBB itself is unreachable, so nothing needs to be
294 // changed.
295 if (!NewBBIDom)
296 return;
297
298 for (i = i + 1; i < PredBlocks.size(); ++i) {
299 if (DT.isReachableFromEntry(PredBlocks[i]))
300 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
301 }
302
303 // Create the new dominator tree node... and set the idom of NewBB.
304 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
305
306 // If NewBB strictly dominates other blocks, then it is now the immediate
307 // dominator of NewBBSucc. Update the dominator tree as appropriate.
308 if (NewBBDominatesNewBBSucc) {
309 DomTreeNodeBase<NodeT> *NewBBSuccNode = DT.getNode(NewBBSucc);
310 DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
311 }
312 }
313
314 public:
DominatorTreeBase(bool isPostDom)315 explicit DominatorTreeBase(bool isPostDom)
316 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
~DominatorTreeBase()317 ~DominatorTreeBase() { reset(); }
318
DominatorTreeBase(DominatorTreeBase && Arg)319 DominatorTreeBase(DominatorTreeBase &&Arg)
320 : DominatorBase<NodeT>(
321 std::move(static_cast<DominatorBase<NodeT> &>(Arg))),
322 DomTreeNodes(std::move(Arg.DomTreeNodes)),
323 RootNode(std::move(Arg.RootNode)),
324 DFSInfoValid(std::move(Arg.DFSInfoValid)),
325 SlowQueries(std::move(Arg.SlowQueries)), IDoms(std::move(Arg.IDoms)),
326 Vertex(std::move(Arg.Vertex)), Info(std::move(Arg.Info)) {
327 Arg.wipe();
328 }
329 DominatorTreeBase &operator=(DominatorTreeBase &&RHS) {
330 DominatorBase<NodeT>::operator=(
331 std::move(static_cast<DominatorBase<NodeT> &>(RHS)));
332 DomTreeNodes = std::move(RHS.DomTreeNodes);
333 RootNode = std::move(RHS.RootNode);
334 DFSInfoValid = std::move(RHS.DFSInfoValid);
335 SlowQueries = std::move(RHS.SlowQueries);
336 IDoms = std::move(RHS.IDoms);
337 Vertex = std::move(RHS.Vertex);
338 Info = std::move(RHS.Info);
339 RHS.wipe();
340 return *this;
341 }
342
343 /// compare - Return false if the other dominator tree base matches this
344 /// dominator tree base. Otherwise return true.
compare(const DominatorTreeBase & Other)345 bool compare(const DominatorTreeBase &Other) const {
346
347 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
348 if (DomTreeNodes.size() != OtherDomTreeNodes.size())
349 return true;
350
351 for (typename DomTreeNodeMapType::const_iterator
352 I = this->DomTreeNodes.begin(),
353 E = this->DomTreeNodes.end();
354 I != E; ++I) {
355 NodeT *BB = I->first;
356 typename DomTreeNodeMapType::const_iterator OI =
357 OtherDomTreeNodes.find(BB);
358 if (OI == OtherDomTreeNodes.end())
359 return true;
360
361 DomTreeNodeBase<NodeT> *MyNd = I->second;
362 DomTreeNodeBase<NodeT> *OtherNd = OI->second;
363
364 if (MyNd->compare(OtherNd))
365 return true;
366 }
367
368 return false;
369 }
370
releaseMemory()371 void releaseMemory() { reset(); }
372
373 /// getNode - return the (Post)DominatorTree node for the specified basic
374 /// block. This is the same as using operator[] on this class.
375 ///
getNode(NodeT * BB)376 DomTreeNodeBase<NodeT> *getNode(NodeT *BB) const {
377 return DomTreeNodes.lookup(BB);
378 }
379
380 DomTreeNodeBase<NodeT> *operator[](NodeT *BB) const { return getNode(BB); }
381
382 /// getRootNode - This returns the entry node for the CFG of the function. If
383 /// this tree represents the post-dominance relations for a function, however,
384 /// this root may be a node with the block == NULL. This is the case when
385 /// there are multiple exit nodes from a particular function. Consumers of
386 /// post-dominance information must be capable of dealing with this
387 /// possibility.
388 ///
getRootNode()389 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
getRootNode()390 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
391
392 /// Get all nodes dominated by R, including R itself.
getDescendants(NodeT * R,SmallVectorImpl<NodeT * > & Result)393 void getDescendants(NodeT *R, SmallVectorImpl<NodeT *> &Result) const {
394 Result.clear();
395 const DomTreeNodeBase<NodeT> *RN = getNode(R);
396 if (!RN)
397 return; // If R is unreachable, it will not be present in the DOM tree.
398 SmallVector<const DomTreeNodeBase<NodeT> *, 8> WL;
399 WL.push_back(RN);
400
401 while (!WL.empty()) {
402 const DomTreeNodeBase<NodeT> *N = WL.pop_back_val();
403 Result.push_back(N->getBlock());
404 WL.append(N->begin(), N->end());
405 }
406 }
407
408 /// properlyDominates - Returns true iff A dominates B and A != B.
409 /// Note that this is not a constant time operation!
410 ///
properlyDominates(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)411 bool properlyDominates(const DomTreeNodeBase<NodeT> *A,
412 const DomTreeNodeBase<NodeT> *B) const {
413 if (!A || !B)
414 return false;
415 if (A == B)
416 return false;
417 return dominates(A, B);
418 }
419
420 bool properlyDominates(const NodeT *A, const NodeT *B) const;
421
422 /// isReachableFromEntry - Return true if A is dominated by the entry
423 /// block of the function containing it.
isReachableFromEntry(const NodeT * A)424 bool isReachableFromEntry(const NodeT *A) const {
425 assert(!this->isPostDominator() &&
426 "This is not implemented for post dominators");
427 return isReachableFromEntry(getNode(const_cast<NodeT *>(A)));
428 }
429
isReachableFromEntry(const DomTreeNodeBase<NodeT> * A)430 bool isReachableFromEntry(const DomTreeNodeBase<NodeT> *A) const { return A; }
431
432 /// dominates - Returns true iff A dominates B. Note that this is not a
433 /// constant time operation!
434 ///
dominates(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)435 bool dominates(const DomTreeNodeBase<NodeT> *A,
436 const DomTreeNodeBase<NodeT> *B) const {
437 // A node trivially dominates itself.
438 if (B == A)
439 return true;
440
441 // An unreachable node is dominated by anything.
442 if (!isReachableFromEntry(B))
443 return true;
444
445 // And dominates nothing.
446 if (!isReachableFromEntry(A))
447 return false;
448
449 // Compare the result of the tree walk and the dfs numbers, if expensive
450 // checks are enabled.
451 #ifdef XDEBUG
452 assert((!DFSInfoValid ||
453 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) &&
454 "Tree walk disagrees with dfs numbers!");
455 #endif
456
457 if (DFSInfoValid)
458 return B->DominatedBy(A);
459
460 // If we end up with too many slow queries, just update the
461 // DFS numbers on the theory that we are going to keep querying.
462 SlowQueries++;
463 if (SlowQueries > 32) {
464 updateDFSNumbers();
465 return B->DominatedBy(A);
466 }
467
468 return dominatedBySlowTreeWalk(A, B);
469 }
470
471 bool dominates(const NodeT *A, const NodeT *B) const;
472
getRoot()473 NodeT *getRoot() const {
474 assert(this->Roots.size() == 1 && "Should always have entry node!");
475 return this->Roots[0];
476 }
477
478 /// findNearestCommonDominator - Find nearest common dominator basic block
479 /// for basic block A and B. If there is no such block then return NULL.
findNearestCommonDominator(NodeT * A,NodeT * B)480 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
481 assert(A->getParent() == B->getParent() &&
482 "Two blocks are not in same function");
483
484 // If either A or B is a entry block then it is nearest common dominator
485 // (for forward-dominators).
486 if (!this->isPostDominator()) {
487 NodeT &Entry = A->getParent()->front();
488 if (A == &Entry || B == &Entry)
489 return &Entry;
490 }
491
492 // If B dominates A then B is nearest common dominator.
493 if (dominates(B, A))
494 return B;
495
496 // If A dominates B then A is nearest common dominator.
497 if (dominates(A, B))
498 return A;
499
500 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
501 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
502
503 // If we have DFS info, then we can avoid all allocations by just querying
504 // it from each IDom. Note that because we call 'dominates' twice above, we
505 // expect to call through this code at most 16 times in a row without
506 // building valid DFS information. This is important as below is a *very*
507 // slow tree walk.
508 if (DFSInfoValid) {
509 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
510 while (IDomA) {
511 if (NodeB->DominatedBy(IDomA))
512 return IDomA->getBlock();
513 IDomA = IDomA->getIDom();
514 }
515 return nullptr;
516 }
517
518 // Collect NodeA dominators set.
519 SmallPtrSet<DomTreeNodeBase<NodeT> *, 16> NodeADoms;
520 NodeADoms.insert(NodeA);
521 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
522 while (IDomA) {
523 NodeADoms.insert(IDomA);
524 IDomA = IDomA->getIDom();
525 }
526
527 // Walk NodeB immediate dominators chain and find common dominator node.
528 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
529 while (IDomB) {
530 if (NodeADoms.count(IDomB) != 0)
531 return IDomB->getBlock();
532
533 IDomB = IDomB->getIDom();
534 }
535
536 return nullptr;
537 }
538
findNearestCommonDominator(const NodeT * A,const NodeT * B)539 const NodeT *findNearestCommonDominator(const NodeT *A, const NodeT *B) {
540 // Cast away the const qualifiers here. This is ok since
541 // const is re-introduced on the return type.
542 return findNearestCommonDominator(const_cast<NodeT *>(A),
543 const_cast<NodeT *>(B));
544 }
545
546 //===--------------------------------------------------------------------===//
547 // API to update (Post)DominatorTree information based on modifications to
548 // the CFG...
549
550 /// addNewBlock - Add a new node to the dominator tree information. This
551 /// creates a new node as a child of DomBB dominator node,linking it into
552 /// the children list of the immediate dominator.
addNewBlock(NodeT * BB,NodeT * DomBB)553 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
554 assert(getNode(BB) == nullptr && "Block already in dominator tree!");
555 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
556 assert(IDomNode && "Not immediate dominator specified for block!");
557 DFSInfoValid = false;
558 return DomTreeNodes[BB] =
559 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
560 }
561
562 /// changeImmediateDominator - This method is used to update the dominator
563 /// tree information when a node's immediate dominator changes.
564 ///
changeImmediateDominator(DomTreeNodeBase<NodeT> * N,DomTreeNodeBase<NodeT> * NewIDom)565 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
566 DomTreeNodeBase<NodeT> *NewIDom) {
567 assert(N && NewIDom && "Cannot change null node pointers!");
568 DFSInfoValid = false;
569 N->setIDom(NewIDom);
570 }
571
changeImmediateDominator(NodeT * BB,NodeT * NewBB)572 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
573 changeImmediateDominator(getNode(BB), getNode(NewBB));
574 }
575
576 /// eraseNode - Removes a node from the dominator tree. Block must not
577 /// dominate any other blocks. Removes node from its immediate dominator's
578 /// children list. Deletes dominator node associated with basic block BB.
eraseNode(NodeT * BB)579 void eraseNode(NodeT *BB) {
580 DomTreeNodeBase<NodeT> *Node = getNode(BB);
581 assert(Node && "Removing node that isn't in dominator tree.");
582 assert(Node->getChildren().empty() && "Node is not a leaf node.");
583
584 // Remove node from immediate dominator's children list.
585 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
586 if (IDom) {
587 typename std::vector<DomTreeNodeBase<NodeT> *>::iterator I =
588 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
589 assert(I != IDom->Children.end() &&
590 "Not in immediate dominator children set!");
591 // I am no longer your child...
592 IDom->Children.erase(I);
593 }
594
595 DomTreeNodes.erase(BB);
596 delete Node;
597 }
598
599 /// removeNode - Removes a node from the dominator tree. Block must not
600 /// dominate any other blocks. Invalidates any node pointing to removed
601 /// block.
removeNode(NodeT * BB)602 void removeNode(NodeT *BB) {
603 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
604 DomTreeNodes.erase(BB);
605 }
606
607 /// splitBlock - BB is split and now it has one successor. Update dominator
608 /// tree to reflect this change.
splitBlock(NodeT * NewBB)609 void splitBlock(NodeT *NewBB) {
610 if (this->IsPostDominators)
611 this->Split<Inverse<NodeT *>, GraphTraits<Inverse<NodeT *>>>(*this,
612 NewBB);
613 else
614 this->Split<NodeT *, GraphTraits<NodeT *>>(*this, NewBB);
615 }
616
617 /// print - Convert to human readable form
618 ///
print(raw_ostream & o)619 void print(raw_ostream &o) const {
620 o << "=============================--------------------------------\n";
621 if (this->isPostDominator())
622 o << "Inorder PostDominator Tree: ";
623 else
624 o << "Inorder Dominator Tree: ";
625 if (!this->DFSInfoValid)
626 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
627 o << "\n";
628
629 // The postdom tree can have a null root if there are no returns.
630 if (getRootNode())
631 PrintDomTree<NodeT>(getRootNode(), o, 1);
632 }
633
634 protected:
635 template <class GraphT>
636 friend typename GraphT::NodeType *
637 Eval(DominatorTreeBase<typename GraphT::NodeType> &DT,
638 typename GraphT::NodeType *V, unsigned LastLinked);
639
640 template <class GraphT>
641 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType> &DT,
642 typename GraphT::NodeType *V, unsigned N);
643
644 template <class FuncT, class N>
645 friend void
646 Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType> &DT, FuncT &F);
647
648 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
649 /// dominator tree in dfs order.
updateDFSNumbers()650 void updateDFSNumbers() const {
651 unsigned DFSNum = 0;
652
653 SmallVector<std::pair<const DomTreeNodeBase<NodeT> *,
654 typename DomTreeNodeBase<NodeT>::const_iterator>,
655 32> WorkStack;
656
657 const DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
658
659 if (!ThisRoot)
660 return;
661
662 // Even in the case of multiple exits that form the post dominator root
663 // nodes, do not iterate over all exits, but start from the virtual root
664 // node. Otherwise bbs, that are not post dominated by any exit but by the
665 // virtual root node, will never be assigned a DFS number.
666 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
667 ThisRoot->DFSNumIn = DFSNum++;
668
669 while (!WorkStack.empty()) {
670 const DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
671 typename DomTreeNodeBase<NodeT>::const_iterator ChildIt =
672 WorkStack.back().second;
673
674 // If we visited all of the children of this node, "recurse" back up the
675 // stack setting the DFOutNum.
676 if (ChildIt == Node->end()) {
677 Node->DFSNumOut = DFSNum++;
678 WorkStack.pop_back();
679 } else {
680 // Otherwise, recursively visit this child.
681 const DomTreeNodeBase<NodeT> *Child = *ChildIt;
682 ++WorkStack.back().second;
683
684 WorkStack.push_back(std::make_pair(Child, Child->begin()));
685 Child->DFSNumIn = DFSNum++;
686 }
687 }
688
689 SlowQueries = 0;
690 DFSInfoValid = true;
691 }
692
getNodeForBlock(NodeT * BB)693 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
694 if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
695 return Node;
696
697 // Haven't calculated this node yet? Get or calculate the node for the
698 // immediate dominator.
699 NodeT *IDom = getIDom(BB);
700
701 assert(IDom || this->DomTreeNodes[nullptr]);
702 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
703
704 // Add a new tree node for this NodeT, and link it as a child of
705 // IDomNode
706 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
707 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
708 }
709
getIDom(NodeT * BB)710 NodeT *getIDom(NodeT *BB) const { return IDoms.lookup(BB); }
711
addRoot(NodeT * BB)712 void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
713
714 public:
715 /// recalculate - compute a dominator tree for the given function
recalculate(FT & F)716 template <class FT> void recalculate(FT &F) {
717 typedef GraphTraits<FT *> TraitsTy;
718 reset();
719 this->Vertex.push_back(nullptr);
720
721 if (!this->IsPostDominators) {
722 // Initialize root
723 NodeT *entry = TraitsTy::getEntryNode(&F);
724 this->Roots.push_back(entry);
725 this->IDoms[entry] = nullptr;
726 this->DomTreeNodes[entry] = nullptr;
727
728 Calculate<FT, NodeT *>(*this, F);
729 } else {
730 // Initialize the roots list
731 for (typename TraitsTy::nodes_iterator I = TraitsTy::nodes_begin(&F),
732 E = TraitsTy::nodes_end(&F);
733 I != E; ++I) {
734 if (TraitsTy::child_begin(I) == TraitsTy::child_end(I))
735 addRoot(I);
736
737 // Prepopulate maps so that we don't get iterator invalidation issues
738 // later.
739 this->IDoms[I] = nullptr;
740 this->DomTreeNodes[I] = nullptr;
741 }
742
743 Calculate<FT, Inverse<NodeT *>>(*this, F);
744 }
745 }
746 };
747
748 // These two functions are declared out of line as a workaround for building
749 // with old (< r147295) versions of clang because of pr11642.
750 template <class NodeT>
dominates(const NodeT * A,const NodeT * B)751 bool DominatorTreeBase<NodeT>::dominates(const NodeT *A, const NodeT *B) const {
752 if (A == B)
753 return true;
754
755 // Cast away the const qualifiers here. This is ok since
756 // this function doesn't actually return the values returned
757 // from getNode.
758 return dominates(getNode(const_cast<NodeT *>(A)),
759 getNode(const_cast<NodeT *>(B)));
760 }
761 template <class NodeT>
properlyDominates(const NodeT * A,const NodeT * B)762 bool DominatorTreeBase<NodeT>::properlyDominates(const NodeT *A,
763 const NodeT *B) const {
764 if (A == B)
765 return false;
766
767 // Cast away the const qualifiers here. This is ok since
768 // this function doesn't actually return the values returned
769 // from getNode.
770 return dominates(getNode(const_cast<NodeT *>(A)),
771 getNode(const_cast<NodeT *>(B)));
772 }
773
774 }
775
776 #endif
777