1 //===- llvm/Analysis/Dominators.h - Dominator Info Calculation --*- 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 //
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
13 // function.
14 //
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.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #ifndef LLVM_ANALYSIS_DOMINATORS_H
22 #define LLVM_ANALYSIS_DOMINATORS_H
23
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"
36 #include <algorithm>
37 #include <map>
38 #include <set>
39
40 namespace llvm {
41
42 //===----------------------------------------------------------------------===//
43 /// DominatorBase - Base class that other, more interesting dominator analyses
44 /// inherit from.
45 ///
46 template <class NodeT>
47 class DominatorBase {
48 protected:
49 std::vector<NodeT*> Roots;
50 const bool IsPostDominators;
DominatorBase(bool isPostDom)51 inline explicit DominatorBase(bool isPostDom) :
52 Roots(), IsPostDominators(isPostDom) {}
53 public:
54
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).
58 ///
getRoots()59 inline const std::vector<NodeT*> &getRoots() const { return Roots; }
60
61 /// isPostDominator - Returns true if analysis based of postdoms
62 ///
isPostDominator()63 bool isPostDominator() const { return IsPostDominators; }
64 };
65
66
67 //===----------------------------------------------------------------------===//
68 // DomTreeNode - Dominator Tree Node
69 template<class NodeT> class DominatorTreeBase;
70 struct PostDominatorTree;
71 class MachineBasicBlock;
72
73 template <class NodeT>
74 class DomTreeNodeBase {
75 NodeT *TheBB;
76 DomTreeNodeBase<NodeT> *IDom;
77 std::vector<DomTreeNodeBase<NodeT> *> Children;
78 int DFSNumIn, DFSNumOut;
79
80 template<class N> friend class DominatorTreeBase;
81 friend struct PostDominatorTree;
82 public:
83 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::iterator iterator;
84 typedef typename std::vector<DomTreeNodeBase<NodeT> *>::const_iterator
85 const_iterator;
86
begin()87 iterator begin() { return Children.begin(); }
end()88 iterator end() { return Children.end(); }
begin()89 const_iterator begin() const { return Children.begin(); }
end()90 const_iterator end() const { return Children.end(); }
91
getBlock()92 NodeT *getBlock() const { return TheBB; }
getIDom()93 DomTreeNodeBase<NodeT> *getIDom() const { return IDom; }
getChildren()94 const std::vector<DomTreeNodeBase<NodeT>*> &getChildren() const {
95 return Children;
96 }
97
DomTreeNodeBase(NodeT * BB,DomTreeNodeBase<NodeT> * iDom)98 DomTreeNodeBase(NodeT *BB, DomTreeNodeBase<NodeT> *iDom)
99 : TheBB(BB), IDom(iDom), DFSNumIn(-1), DFSNumOut(-1) { }
100
addChild(DomTreeNodeBase<NodeT> * C)101 DomTreeNodeBase<NodeT> *addChild(DomTreeNodeBase<NodeT> *C) {
102 Children.push_back(C);
103 return C;
104 }
105
getNumChildren()106 size_t getNumChildren() const {
107 return Children.size();
108 }
109
clearAllChildren()110 void clearAllChildren() {
111 Children.clear();
112 }
113
compare(DomTreeNodeBase<NodeT> * Other)114 bool compare(DomTreeNodeBase<NodeT> *Other) {
115 if (getNumChildren() != Other->getNumChildren())
116 return true;
117
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);
122 }
123
124 for (iterator I = begin(), E = end(); I != E; ++I) {
125 NodeT *N = (*I)->getBlock();
126 if (OtherChildren.count(N) == 0)
127 return true;
128 }
129 return false;
130 }
131
setIDom(DomTreeNodeBase<NodeT> * NewIDom)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);
141
142 // Switch to new dominator
143 IDom = NewIDom;
144 IDom->Children.push_back(this);
145 }
146 }
147
148 /// getDFSNumIn/getDFSNumOut - These are an internal implementation detail, do
149 /// not call them.
getDFSNumIn()150 unsigned getDFSNumIn() const { return DFSNumIn; }
getDFSNumOut()151 unsigned getDFSNumOut() const { return DFSNumOut; }
152 private:
153 // Return true if this node is dominated by other. Use this only if DFS info
154 // is valid.
DominatedBy(const DomTreeNodeBase<NodeT> * other)155 bool DominatedBy(const DomTreeNodeBase<NodeT> *other) const {
156 return this->DFSNumIn >= other->DFSNumIn &&
157 this->DFSNumOut <= other->DFSNumOut;
158 }
159 };
160
161 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<BasicBlock>);
162 EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<MachineBasicBlock>);
163
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);
169 else
170 o << " <<exit node>>";
171
172 o << " {" << Node->getDFSNumIn() << "," << Node->getDFSNumOut() << "}";
173
174 return o << "\n";
175 }
176
177 template<class NodeT>
PrintDomTree(const DomTreeNodeBase<NodeT> * N,raw_ostream & o,unsigned Lev)178 static void PrintDomTree(const DomTreeNodeBase<NodeT> *N, raw_ostream &o,
179 unsigned Lev) {
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);
184 }
185
186 typedef DomTreeNodeBase<BasicBlock> DomTreeNode;
187
188 //===----------------------------------------------------------------------===//
189 /// DominatorTree - Calculate the immediate dominator tree for a function.
190 ///
191
192 template<class FuncT, class N>
193 void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
194 FuncT& F);
195
196 template<class NodeT>
197 class DominatorTreeBase : public DominatorBase<NodeT> {
198 protected:
199 typedef DenseMap<NodeT*, DomTreeNodeBase<NodeT>*> DomTreeNodeMapType;
200 DomTreeNodeMapType DomTreeNodes;
201 DomTreeNodeBase<NodeT> *RootNode;
202
203 bool DFSInfoValid;
204 unsigned int SlowQueries;
205 // Information record used during immediate dominators computation.
206 struct InfoRec {
207 unsigned DFSNum;
208 unsigned Semi;
209 unsigned Size;
210 NodeT *Label, *Child;
211 unsigned Parent, Ancestor;
212
213 std::vector<NodeT*> Bucket;
214
InfoRecInfoRec215 InfoRec() : DFSNum(0), Semi(0), Size(0), Label(0), Child(0), Parent(0),
216 Ancestor(0) {}
217 };
218
219 DenseMap<NodeT*, NodeT*> IDoms;
220
221 // Vertex - Map the DFS number to the BasicBlock*
222 std::vector<NodeT*> Vertex;
223
224 // Info - Collection of information used during the computation of idoms.
225 DenseMap<NodeT*, InfoRec> Info;
226
reset()227 void reset() {
228 for (typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.begin(),
229 E = DomTreeNodes.end(); I != E; ++I)
230 delete I->second;
231 DomTreeNodes.clear();
232 IDoms.clear();
233 this->Roots.clear();
234 Vertex.clear();
235 RootNode = 0;
236 }
237
238 // NewBB is split and now it has one successor. Update dominator tree to
239 // reflect this change.
240 template<class N, class GraphT>
Split(DominatorTreeBase<typename GraphT::NodeType> & DT,typename GraphT::NodeType * NewBB)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);
247
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);
254
255 assert(!PredBlocks.empty() && "No predblocks?");
256
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;
265 break;
266 }
267 }
268
269 // Find NewBB's immediate dominator and create new dominator tree node for
270 // NewBB.
271 NodeT *NewBBIDom = 0;
272 unsigned i = 0;
273 for (i = 0; i < PredBlocks.size(); ++i)
274 if (DT.isReachableFromEntry(PredBlocks[i])) {
275 NewBBIDom = PredBlocks[i];
276 break;
277 }
278
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
281 // changed.
282 if (!NewBBIDom)
283 return;
284
285 for (i = i + 1; i < PredBlocks.size(); ++i) {
286 if (DT.isReachableFromEntry(PredBlocks[i]))
287 NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
288 }
289
290 // Create the new dominator tree node... and set the idom of NewBB.
291 DomTreeNodeBase<NodeT> *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
292
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);
298 }
299 }
300
301 public:
DominatorTreeBase(bool isPostDom)302 explicit DominatorTreeBase(bool isPostDom)
303 : DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
~DominatorTreeBase()304 virtual ~DominatorTreeBase() { reset(); }
305
306 // FIXME: Should remove this
runOnFunction(Function & F)307 virtual bool runOnFunction(Function &F) { return false; }
308
309 /// compare - Return false if the other dominator tree base matches this
310 /// dominator tree base. Otherwise return true.
compare(DominatorTreeBase & Other)311 bool compare(DominatorTreeBase &Other) const {
312
313 const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
314 if (DomTreeNodes.size() != OtherDomTreeNodes.size())
315 return true;
316
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())
323 return true;
324
325 DomTreeNodeBase<NodeT>* MyNd = I->second;
326 DomTreeNodeBase<NodeT>* OtherNd = OI->second;
327
328 if (MyNd->compare(OtherNd))
329 return true;
330 }
331
332 return false;
333 }
334
releaseMemory()335 virtual void releaseMemory() { reset(); }
336
337 /// getNode - return the (Post)DominatorTree node for the specified basic
338 /// block. This is the same as using operator[] on this class.
339 ///
getNode(NodeT * BB)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;
343 }
344
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
350 /// possibility.
351 ///
getRootNode()352 DomTreeNodeBase<NodeT> *getRootNode() { return RootNode; }
getRootNode()353 const DomTreeNodeBase<NodeT> *getRootNode() const { return RootNode; }
354
355 /// properlyDominates - Returns true iff this dominates N and this != N.
356 /// Note that this is not a constant time operation!
357 ///
properlyDominates(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)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);
362 }
363
properlyDominates(NodeT * A,NodeT * B)364 inline bool properlyDominates(NodeT *A, NodeT *B) {
365 return properlyDominates(getNode(A), getNode(B));
366 }
367
dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)368 bool dominatedBySlowTreeWalk(const DomTreeNodeBase<NodeT> *A,
369 const DomTreeNodeBase<NodeT> *B) const {
370 const DomTreeNodeBase<NodeT> *IDom;
371 if (A == 0 || B == 0) return false;
372 while ((IDom = B->getIDom()) != 0 && IDom != A && IDom != B)
373 B = IDom; // Walk up the tree
374 return IDom != 0;
375 }
376
377
378 /// isReachableFromEntry - Return true if A is dominated by the entry
379 /// block of the function containing it.
isReachableFromEntry(NodeT * A)380 bool isReachableFromEntry(NodeT* A) {
381 assert(!this->isPostDominator() &&
382 "This is not implemented for post dominators");
383 return dominates(&A->getParent()->front(), A);
384 }
385
386 /// dominates - Returns true iff A dominates B. Note that this is not a
387 /// constant time operation!
388 ///
dominates(const DomTreeNodeBase<NodeT> * A,const DomTreeNodeBase<NodeT> * B)389 inline bool dominates(const DomTreeNodeBase<NodeT> *A,
390 const DomTreeNodeBase<NodeT> *B) {
391 if (B == A)
392 return true; // A node trivially dominates itself.
393
394 if (A == 0 || B == 0)
395 return false;
396
397 // Compare the result of the tree walk and the dfs numbers, if expensive
398 // checks are enabled.
399 #ifdef XDEBUG
400 assert((!DFSInfoValid ||
401 (dominatedBySlowTreeWalk(A, B) == B->DominatedBy(A))) &&
402 "Tree walk disagrees with dfs numbers!");
403 #endif
404
405 if (DFSInfoValid)
406 return B->DominatedBy(A);
407
408 // If we end up with too many slow queries, just update the
409 // DFS numbers on the theory that we are going to keep querying.
410 SlowQueries++;
411 if (SlowQueries > 32) {
412 updateDFSNumbers();
413 return B->DominatedBy(A);
414 }
415
416 return dominatedBySlowTreeWalk(A, B);
417 }
418
dominates(const NodeT * A,const NodeT * B)419 inline bool dominates(const NodeT *A, const NodeT *B) {
420 if (A == B)
421 return true;
422
423 // Cast away the const qualifiers here. This is ok since
424 // this function doesn't actually return the values returned
425 // from getNode.
426 return dominates(getNode(const_cast<NodeT *>(A)),
427 getNode(const_cast<NodeT *>(B)));
428 }
429
getRoot()430 NodeT *getRoot() const {
431 assert(this->Roots.size() == 1 && "Should always have entry node!");
432 return this->Roots[0];
433 }
434
435 /// findNearestCommonDominator - Find nearest common dominator basic block
436 /// for basic block A and B. If there is no such block then return NULL.
findNearestCommonDominator(NodeT * A,NodeT * B)437 NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) {
438 assert(A->getParent() == B->getParent() &&
439 "Two blocks are not in same function");
440
441 // If either A or B is a entry block then it is nearest common dominator
442 // (for forward-dominators).
443 if (!this->isPostDominator()) {
444 NodeT &Entry = A->getParent()->front();
445 if (A == &Entry || B == &Entry)
446 return &Entry;
447 }
448
449 // If B dominates A then B is nearest common dominator.
450 if (dominates(B, A))
451 return B;
452
453 // If A dominates B then A is nearest common dominator.
454 if (dominates(A, B))
455 return A;
456
457 DomTreeNodeBase<NodeT> *NodeA = getNode(A);
458 DomTreeNodeBase<NodeT> *NodeB = getNode(B);
459
460 // Collect NodeA dominators set.
461 SmallPtrSet<DomTreeNodeBase<NodeT>*, 16> NodeADoms;
462 NodeADoms.insert(NodeA);
463 DomTreeNodeBase<NodeT> *IDomA = NodeA->getIDom();
464 while (IDomA) {
465 NodeADoms.insert(IDomA);
466 IDomA = IDomA->getIDom();
467 }
468
469 // Walk NodeB immediate dominators chain and find common dominator node.
470 DomTreeNodeBase<NodeT> *IDomB = NodeB->getIDom();
471 while (IDomB) {
472 if (NodeADoms.count(IDomB) != 0)
473 return IDomB->getBlock();
474
475 IDomB = IDomB->getIDom();
476 }
477
478 return NULL;
479 }
480
481 //===--------------------------------------------------------------------===//
482 // API to update (Post)DominatorTree information based on modifications to
483 // the CFG...
484
485 /// addNewBlock - Add a new node to the dominator tree information. This
486 /// creates a new node as a child of DomBB dominator node,linking it into
487 /// the children list of the immediate dominator.
addNewBlock(NodeT * BB,NodeT * DomBB)488 DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
489 assert(getNode(BB) == 0 && "Block already in dominator tree!");
490 DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
491 assert(IDomNode && "Not immediate dominator specified for block!");
492 DFSInfoValid = false;
493 return DomTreeNodes[BB] =
494 IDomNode->addChild(new DomTreeNodeBase<NodeT>(BB, IDomNode));
495 }
496
497 /// changeImmediateDominator - This method is used to update the dominator
498 /// tree information when a node's immediate dominator changes.
499 ///
changeImmediateDominator(DomTreeNodeBase<NodeT> * N,DomTreeNodeBase<NodeT> * NewIDom)500 void changeImmediateDominator(DomTreeNodeBase<NodeT> *N,
501 DomTreeNodeBase<NodeT> *NewIDom) {
502 assert(N && NewIDom && "Cannot change null node pointers!");
503 DFSInfoValid = false;
504 N->setIDom(NewIDom);
505 }
506
changeImmediateDominator(NodeT * BB,NodeT * NewBB)507 void changeImmediateDominator(NodeT *BB, NodeT *NewBB) {
508 changeImmediateDominator(getNode(BB), getNode(NewBB));
509 }
510
511 /// eraseNode - Removes a node from the dominator tree. Block must not
512 /// domiante any other blocks. Removes node from its immediate dominator's
513 /// children list. Deletes dominator node associated with basic block BB.
eraseNode(NodeT * BB)514 void eraseNode(NodeT *BB) {
515 DomTreeNodeBase<NodeT> *Node = getNode(BB);
516 assert(Node && "Removing node that isn't in dominator tree.");
517 assert(Node->getChildren().empty() && "Node is not a leaf node.");
518
519 // Remove node from immediate dominator's children list.
520 DomTreeNodeBase<NodeT> *IDom = Node->getIDom();
521 if (IDom) {
522 typename std::vector<DomTreeNodeBase<NodeT>*>::iterator I =
523 std::find(IDom->Children.begin(), IDom->Children.end(), Node);
524 assert(I != IDom->Children.end() &&
525 "Not in immediate dominator children set!");
526 // I am no longer your child...
527 IDom->Children.erase(I);
528 }
529
530 DomTreeNodes.erase(BB);
531 delete Node;
532 }
533
534 /// removeNode - Removes a node from the dominator tree. Block must not
535 /// dominate any other blocks. Invalidates any node pointing to removed
536 /// block.
removeNode(NodeT * BB)537 void removeNode(NodeT *BB) {
538 assert(getNode(BB) && "Removing node that isn't in dominator tree.");
539 DomTreeNodes.erase(BB);
540 }
541
542 /// splitBlock - BB is split and now it has one successor. Update dominator
543 /// tree to reflect this change.
splitBlock(NodeT * NewBB)544 void splitBlock(NodeT* NewBB) {
545 if (this->IsPostDominators)
546 this->Split<Inverse<NodeT*>, GraphTraits<Inverse<NodeT*> > >(*this, NewBB);
547 else
548 this->Split<NodeT*, GraphTraits<NodeT*> >(*this, NewBB);
549 }
550
551 /// print - Convert to human readable form
552 ///
print(raw_ostream & o)553 void print(raw_ostream &o) const {
554 o << "=============================--------------------------------\n";
555 if (this->isPostDominator())
556 o << "Inorder PostDominator Tree: ";
557 else
558 o << "Inorder Dominator Tree: ";
559 if (this->DFSInfoValid)
560 o << "DFSNumbers invalid: " << SlowQueries << " slow queries.";
561 o << "\n";
562
563 // The postdom tree can have a null root if there are no returns.
564 if (getRootNode())
565 PrintDomTree<NodeT>(getRootNode(), o, 1);
566 }
567
568 protected:
569 template<class GraphT>
570 friend void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
571 typename GraphT::NodeType* VIn);
572
573 template<class GraphT>
574 friend typename GraphT::NodeType* Eval(
575 DominatorTreeBase<typename GraphT::NodeType>& DT,
576 typename GraphT::NodeType* V);
577
578 template<class GraphT>
579 friend void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
580 unsigned DFSNumV, typename GraphT::NodeType* W,
581 typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo);
582
583 template<class GraphT>
584 friend unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
585 typename GraphT::NodeType* V,
586 unsigned N);
587
588 template<class FuncT, class N>
589 friend void Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType>& DT,
590 FuncT& F);
591
592 /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
593 /// dominator tree in dfs order.
updateDFSNumbers()594 void updateDFSNumbers() {
595 unsigned DFSNum = 0;
596
597 SmallVector<std::pair<DomTreeNodeBase<NodeT>*,
598 typename DomTreeNodeBase<NodeT>::iterator>, 32> WorkStack;
599
600 DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
601
602 if (!ThisRoot)
603 return;
604
605 // Even in the case of multiple exits that form the post dominator root
606 // nodes, do not iterate over all exits, but start from the virtual root
607 // node. Otherwise bbs, that are not post dominated by any exit but by the
608 // virtual root node, will never be assigned a DFS number.
609 WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
610 ThisRoot->DFSNumIn = DFSNum++;
611
612 while (!WorkStack.empty()) {
613 DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
614 typename DomTreeNodeBase<NodeT>::iterator ChildIt =
615 WorkStack.back().second;
616
617 // If we visited all of the children of this node, "recurse" back up the
618 // stack setting the DFOutNum.
619 if (ChildIt == Node->end()) {
620 Node->DFSNumOut = DFSNum++;
621 WorkStack.pop_back();
622 } else {
623 // Otherwise, recursively visit this child.
624 DomTreeNodeBase<NodeT> *Child = *ChildIt;
625 ++WorkStack.back().second;
626
627 WorkStack.push_back(std::make_pair(Child, Child->begin()));
628 Child->DFSNumIn = DFSNum++;
629 }
630 }
631
632 SlowQueries = 0;
633 DFSInfoValid = true;
634 }
635
getNodeForBlock(NodeT * BB)636 DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
637 typename DomTreeNodeMapType::iterator I = this->DomTreeNodes.find(BB);
638 if (I != this->DomTreeNodes.end() && I->second)
639 return I->second;
640
641 // Haven't calculated this node yet? Get or calculate the node for the
642 // immediate dominator.
643 NodeT *IDom = getIDom(BB);
644
645 assert(IDom || this->DomTreeNodes[NULL]);
646 DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
647
648 // Add a new tree node for this BasicBlock, and link it as a child of
649 // IDomNode
650 DomTreeNodeBase<NodeT> *C = new DomTreeNodeBase<NodeT>(BB, IDomNode);
651 return this->DomTreeNodes[BB] = IDomNode->addChild(C);
652 }
653
getIDom(NodeT * BB)654 inline NodeT *getIDom(NodeT *BB) const {
655 typename DenseMap<NodeT*, NodeT*>::const_iterator I = IDoms.find(BB);
656 return I != IDoms.end() ? I->second : 0;
657 }
658
addRoot(NodeT * BB)659 inline void addRoot(NodeT* BB) {
660 this->Roots.push_back(BB);
661 }
662
663 public:
664 /// recalculate - compute a dominator tree for the given function
665 template<class FT>
recalculate(FT & F)666 void recalculate(FT& F) {
667 reset();
668 this->Vertex.push_back(0);
669
670 if (!this->IsPostDominators) {
671 // Initialize root
672 this->Roots.push_back(&F.front());
673 this->IDoms[&F.front()] = 0;
674 this->DomTreeNodes[&F.front()] = 0;
675
676 Calculate<FT, NodeT*>(*this, F);
677 } else {
678 // Initialize the roots list
679 for (typename FT::iterator I = F.begin(), E = F.end(); I != E; ++I) {
680 if (std::distance(GraphTraits<FT*>::child_begin(I),
681 GraphTraits<FT*>::child_end(I)) == 0)
682 addRoot(I);
683
684 // Prepopulate maps so that we don't get iterator invalidation issues later.
685 this->IDoms[I] = 0;
686 this->DomTreeNodes[I] = 0;
687 }
688
689 Calculate<FT, Inverse<NodeT*> >(*this, F);
690 }
691 }
692 };
693
694 EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
695
696 //===-------------------------------------
697 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
698 /// compute a normal dominator tree.
699 ///
700 class DominatorTree : public FunctionPass {
701 public:
702 static char ID; // Pass ID, replacement for typeid
703 DominatorTreeBase<BasicBlock>* DT;
704
DominatorTree()705 DominatorTree() : FunctionPass(ID) {
706 DT = new DominatorTreeBase<BasicBlock>(false);
707 }
708
~DominatorTree()709 ~DominatorTree() {
710 delete DT;
711 }
712
getBase()713 DominatorTreeBase<BasicBlock>& getBase() { return *DT; }
714
715 /// getRoots - Return the root blocks of the current CFG. This may include
716 /// multiple blocks if we are computing post dominators. For forward
717 /// dominators, this will always be a single block (the entry node).
718 ///
getRoots()719 inline const std::vector<BasicBlock*> &getRoots() const {
720 return DT->getRoots();
721 }
722
getRoot()723 inline BasicBlock *getRoot() const {
724 return DT->getRoot();
725 }
726
getRootNode()727 inline DomTreeNode *getRootNode() const {
728 return DT->getRootNode();
729 }
730
731 /// compare - Return false if the other dominator tree matches this
732 /// dominator tree. Otherwise return true.
compare(DominatorTree & Other)733 inline bool compare(DominatorTree &Other) const {
734 DomTreeNode *R = getRootNode();
735 DomTreeNode *OtherR = Other.getRootNode();
736
737 if (!R || !OtherR || R->getBlock() != OtherR->getBlock())
738 return true;
739
740 if (DT->compare(Other.getBase()))
741 return true;
742
743 return false;
744 }
745
746 virtual bool runOnFunction(Function &F);
747
748 virtual void verifyAnalysis() const;
749
getAnalysisUsage(AnalysisUsage & AU)750 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
751 AU.setPreservesAll();
752 }
753
dominates(DomTreeNode * A,DomTreeNode * B)754 inline bool dominates(DomTreeNode* A, DomTreeNode* B) const {
755 return DT->dominates(A, B);
756 }
757
dominates(const BasicBlock * A,const BasicBlock * B)758 inline bool dominates(const BasicBlock* A, const BasicBlock* B) const {
759 return DT->dominates(A, B);
760 }
761
762 // dominates - Return true if A dominates B. This performs the
763 // special checks necessary if A and B are in the same basic block.
764 bool dominates(const Instruction *A, const Instruction *B) const;
765
properlyDominates(const DomTreeNode * A,const DomTreeNode * B)766 bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const {
767 return DT->properlyDominates(A, B);
768 }
769
properlyDominates(BasicBlock * A,BasicBlock * B)770 bool properlyDominates(BasicBlock *A, BasicBlock *B) const {
771 return DT->properlyDominates(A, B);
772 }
773
774 /// findNearestCommonDominator - Find nearest common dominator basic block
775 /// for basic block A and B. If there is no such block then return NULL.
findNearestCommonDominator(BasicBlock * A,BasicBlock * B)776 inline BasicBlock *findNearestCommonDominator(BasicBlock *A, BasicBlock *B) {
777 return DT->findNearestCommonDominator(A, B);
778 }
779
780 inline DomTreeNode *operator[](BasicBlock *BB) const {
781 return DT->getNode(BB);
782 }
783
784 /// getNode - return the (Post)DominatorTree node for the specified basic
785 /// block. This is the same as using operator[] on this class.
786 ///
getNode(BasicBlock * BB)787 inline DomTreeNode *getNode(BasicBlock *BB) const {
788 return DT->getNode(BB);
789 }
790
791 /// addNewBlock - Add a new node to the dominator tree information. This
792 /// creates a new node as a child of DomBB dominator node,linking it into
793 /// the children list of the immediate dominator.
addNewBlock(BasicBlock * BB,BasicBlock * DomBB)794 inline DomTreeNode *addNewBlock(BasicBlock *BB, BasicBlock *DomBB) {
795 return DT->addNewBlock(BB, DomBB);
796 }
797
798 /// changeImmediateDominator - This method is used to update the dominator
799 /// tree information when a node's immediate dominator changes.
800 ///
changeImmediateDominator(BasicBlock * N,BasicBlock * NewIDom)801 inline void changeImmediateDominator(BasicBlock *N, BasicBlock* NewIDom) {
802 DT->changeImmediateDominator(N, NewIDom);
803 }
804
changeImmediateDominator(DomTreeNode * N,DomTreeNode * NewIDom)805 inline void changeImmediateDominator(DomTreeNode *N, DomTreeNode* NewIDom) {
806 DT->changeImmediateDominator(N, NewIDom);
807 }
808
809 /// eraseNode - Removes a node from the dominator tree. Block must not
810 /// domiante any other blocks. Removes node from its immediate dominator's
811 /// children list. Deletes dominator node associated with basic block BB.
eraseNode(BasicBlock * BB)812 inline void eraseNode(BasicBlock *BB) {
813 DT->eraseNode(BB);
814 }
815
816 /// splitBlock - BB is split and now it has one successor. Update dominator
817 /// tree to reflect this change.
splitBlock(BasicBlock * NewBB)818 inline void splitBlock(BasicBlock* NewBB) {
819 DT->splitBlock(NewBB);
820 }
821
isReachableFromEntry(BasicBlock * A)822 bool isReachableFromEntry(BasicBlock* A) {
823 return DT->isReachableFromEntry(A);
824 }
825
826
releaseMemory()827 virtual void releaseMemory() {
828 DT->releaseMemory();
829 }
830
831 virtual void print(raw_ostream &OS, const Module* M= 0) const;
832 };
833
834 //===-------------------------------------
835 /// DominatorTree GraphTraits specialization so the DominatorTree can be
836 /// iterable by generic graph iterators.
837 ///
838 template <> struct GraphTraits<DomTreeNode*> {
839 typedef DomTreeNode NodeType;
840 typedef NodeType::iterator ChildIteratorType;
841
842 static NodeType *getEntryNode(NodeType *N) {
843 return N;
844 }
845 static inline ChildIteratorType child_begin(NodeType *N) {
846 return N->begin();
847 }
848 static inline ChildIteratorType child_end(NodeType *N) {
849 return N->end();
850 }
851
852 typedef df_iterator<DomTreeNode*> nodes_iterator;
853
854 static nodes_iterator nodes_begin(DomTreeNode *N) {
855 return df_begin(getEntryNode(N));
856 }
857
858 static nodes_iterator nodes_end(DomTreeNode *N) {
859 return df_end(getEntryNode(N));
860 }
861 };
862
863 template <> struct GraphTraits<DominatorTree*>
864 : public GraphTraits<DomTreeNode*> {
865 static NodeType *getEntryNode(DominatorTree *DT) {
866 return DT->getRootNode();
867 }
868
869 static nodes_iterator nodes_begin(DominatorTree *N) {
870 return df_begin(getEntryNode(N));
871 }
872
873 static nodes_iterator nodes_end(DominatorTree *N) {
874 return df_end(getEntryNode(N));
875 }
876 };
877
878
879 //===----------------------------------------------------------------------===//
880 /// DominanceFrontierBase - Common base class for computing forward and inverse
881 /// dominance frontiers for a function.
882 ///
883 class DominanceFrontierBase : public FunctionPass {
884 public:
885 typedef std::set<BasicBlock*> DomSetType; // Dom set for a bb
886 typedef std::map<BasicBlock*, DomSetType> DomSetMapType; // Dom set map
887 protected:
888 DomSetMapType Frontiers;
889 std::vector<BasicBlock*> Roots;
890 const bool IsPostDominators;
891
892 public:
893 DominanceFrontierBase(char &ID, bool isPostDom)
894 : FunctionPass(ID), IsPostDominators(isPostDom) {}
895
896 /// getRoots - Return the root blocks of the current CFG. This may include
897 /// multiple blocks if we are computing post dominators. For forward
898 /// dominators, this will always be a single block (the entry node).
899 ///
900 inline const std::vector<BasicBlock*> &getRoots() const { return Roots; }
901
902 /// isPostDominator - Returns true if analysis based of postdoms
903 ///
904 bool isPostDominator() const { return IsPostDominators; }
905
906 virtual void releaseMemory() { Frontiers.clear(); }
907
908 // Accessor interface:
909 typedef DomSetMapType::iterator iterator;
910 typedef DomSetMapType::const_iterator const_iterator;
911 iterator begin() { return Frontiers.begin(); }
912 const_iterator begin() const { return Frontiers.begin(); }
913 iterator end() { return Frontiers.end(); }
914 const_iterator end() const { return Frontiers.end(); }
915 iterator find(BasicBlock *B) { return Frontiers.find(B); }
916 const_iterator find(BasicBlock *B) const { return Frontiers.find(B); }
917
918 iterator addBasicBlock(BasicBlock *BB, const DomSetType &frontier) {
919 assert(find(BB) == end() && "Block already in DominanceFrontier!");
920 return Frontiers.insert(std::make_pair(BB, frontier)).first;
921 }
922
923 /// removeBlock - Remove basic block BB's frontier.
924 void removeBlock(BasicBlock *BB) {
925 assert(find(BB) != end() && "Block is not in DominanceFrontier!");
926 for (iterator I = begin(), E = end(); I != E; ++I)
927 I->second.erase(BB);
928 Frontiers.erase(BB);
929 }
930
931 void addToFrontier(iterator I, BasicBlock *Node) {
932 assert(I != end() && "BB is not in DominanceFrontier!");
933 I->second.insert(Node);
934 }
935
936 void removeFromFrontier(iterator I, BasicBlock *Node) {
937 assert(I != end() && "BB is not in DominanceFrontier!");
938 assert(I->second.count(Node) && "Node is not in DominanceFrontier of BB");
939 I->second.erase(Node);
940 }
941
942 /// compareDomSet - Return false if two domsets match. Otherwise
943 /// return true;
944 bool compareDomSet(DomSetType &DS1, const DomSetType &DS2) const {
945 std::set<BasicBlock *> tmpSet;
946 for (DomSetType::const_iterator I = DS2.begin(),
947 E = DS2.end(); I != E; ++I)
948 tmpSet.insert(*I);
949
950 for (DomSetType::const_iterator I = DS1.begin(),
951 E = DS1.end(); I != E; ) {
952 BasicBlock *Node = *I++;
953
954 if (tmpSet.erase(Node) == 0)
955 // Node is in DS1 but not in DS2.
956 return true;
957 }
958
959 if (!tmpSet.empty())
960 // There are nodes that are in DS2 but not in DS1.
961 return true;
962
963 // DS1 and DS2 matches.
964 return false;
965 }
966
967 /// compare - Return true if the other dominance frontier base matches
968 /// this dominance frontier base. Otherwise return false.
969 bool compare(DominanceFrontierBase &Other) const {
970 DomSetMapType tmpFrontiers;
971 for (DomSetMapType::const_iterator I = Other.begin(),
972 E = Other.end(); I != E; ++I)
973 tmpFrontiers.insert(std::make_pair(I->first, I->second));
974
975 for (DomSetMapType::iterator I = tmpFrontiers.begin(),
976 E = tmpFrontiers.end(); I != E; ) {
977 BasicBlock *Node = I->first;
978 const_iterator DFI = find(Node);
979 if (DFI == end())
980 return true;
981
982 if (compareDomSet(I->second, DFI->second))
983 return true;
984
985 ++I;
986 tmpFrontiers.erase(Node);
987 }
988
989 if (!tmpFrontiers.empty())
990 return true;
991
992 return false;
993 }
994
995 /// print - Convert to human readable form
996 ///
997 virtual void print(raw_ostream &OS, const Module* = 0) const;
998
999 /// dump - Dump the dominance frontier to dbgs().
1000 void dump() const;
1001 };
1002
1003
1004 //===-------------------------------------
1005 /// DominanceFrontier Class - Concrete subclass of DominanceFrontierBase that is
1006 /// used to compute a forward dominator frontiers.
1007 ///
1008 class DominanceFrontier : public DominanceFrontierBase {
1009 public:
1010 static char ID; // Pass ID, replacement for typeid
1011 DominanceFrontier() :
1012 DominanceFrontierBase(ID, false) {}
1013
1014 BasicBlock *getRoot() const {
1015 assert(Roots.size() == 1 && "Should always have entry node!");
1016 return Roots[0];
1017 }
1018
1019 virtual bool runOnFunction(Function &) {
1020 Frontiers.clear();
1021 DominatorTree &DT = getAnalysis<DominatorTree>();
1022 Roots = DT.getRoots();
1023 assert(Roots.size() == 1 && "Only one entry block for forward domfronts!");
1024 calculate(DT, DT[Roots[0]]);
1025 return false;
1026 }
1027
1028 virtual void verifyAnalysis() const;
1029
1030 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
1031 AU.setPreservesAll();
1032 AU.addRequired<DominatorTree>();
1033 }
1034
1035 /// splitBlock - BB is split and now it has one successor. Update dominance
1036 /// frontier to reflect this change.
1037 void splitBlock(BasicBlock *BB);
1038
1039 /// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier
1040 /// to reflect this change.
1041 void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB,
1042 DominatorTree *DT) {
1043 // NewBB is now dominating BB. Which means BB's dominance
1044 // frontier is now part of NewBB's dominance frontier. However, BB
1045 // itself is not member of NewBB's dominance frontier.
1046 DominanceFrontier::iterator NewDFI = find(NewBB);
1047 DominanceFrontier::iterator DFI = find(BB);
1048 // If BB was an entry block then its frontier is empty.
1049 if (DFI == end())
1050 return;
1051 DominanceFrontier::DomSetType BBSet = DFI->second;
1052 for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
1053 BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {
1054 BasicBlock *DFMember = *BBSetI;
1055 // Insert only if NewBB dominates DFMember.
1056 if (!DT->dominates(NewBB, DFMember))
1057 NewDFI->second.insert(DFMember);
1058 }
1059 NewDFI->second.erase(BB);
1060 }
1061
1062 const DomSetType &calculate(const DominatorTree &DT,
1063 const DomTreeNode *Node);
1064 };
1065
1066
1067 } // End llvm namespace
1068
1069 #endif
1070