1 //===- Dominators.cpp - Dominator Calculation -----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements simple dominator construction algorithms for finding
11 // forward dominators. Postdominators are available in libanalysis, but are not
12 // included in libvmcore, because it's not needed. Forward dominators are
13 // needed to support the Verifier pass.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/Dominators.h"
18 #include "llvm/Support/CFG.h"
19 #include "llvm/Assembly/Writer.h"
20 #include "llvm/ADT/DepthFirstIterator.h"
21 #include "llvm/ADT/SetOperations.h"
22 #include "llvm/ADT/SmallPtrSet.h"
23 #include "llvm/Instructions.h"
24 #include "llvm/Support/Streams.h"
29 static std::ostream &operator<<(std::ostream &o,
30 const std::set<BasicBlock*> &BBs) {
31 for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
34 WriteAsOperand(o, *I, false);
36 o << " <<exit node>>";
41 //===----------------------------------------------------------------------===//
42 // DominatorTree Implementation
43 //===----------------------------------------------------------------------===//
45 // DominatorTree construction - This pass constructs immediate dominator
46 // information for a flow-graph based on the algorithm described in this
49 // A Fast Algorithm for Finding Dominators in a Flowgraph
50 // T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
52 // This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
53 // LINK, but it turns out that the theoretically slower O(n*log(n))
54 // implementation is actually faster than the "efficient" algorithm (even for
55 // large CFGs) because the constant overheads are substantially smaller. The
56 // lower-complexity version can be enabled with the following #define:
58 #define BALANCE_IDOM_TREE 0
60 //===----------------------------------------------------------------------===//
62 char DominatorTree::ID = 0;
63 static RegisterPass<DominatorTree>
64 E("domtree", "Dominator Tree Construction", true);
66 // NewBB is split and now it has one successor. Update dominator tree to
67 // reflect this change.
68 void DominatorTree::splitBlock(BasicBlock *NewBB) {
70 assert(NewBB->getTerminator()->getNumSuccessors() == 1
71 && "NewBB should have a single successor!");
72 BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
74 std::vector<BasicBlock*> PredBlocks;
75 for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
77 PredBlocks.push_back(*PI);
79 assert(!PredBlocks.empty() && "No predblocks??");
81 // The newly inserted basic block will dominate existing basic blocks iff the
82 // PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
83 // the non-pred blocks, then they all must be the same block!
85 bool NewBBDominatesNewBBSucc = true;
87 BasicBlock *OnePred = PredBlocks[0];
88 unsigned i = 1, e = PredBlocks.size();
89 for (i = 1; !isReachableFromEntry(OnePred); ++i) {
90 assert(i != e && "Didn't find reachable pred?");
91 OnePred = PredBlocks[i];
95 if (PredBlocks[i] != OnePred && isReachableFromEntry(OnePred)){
96 NewBBDominatesNewBBSucc = false;
100 if (NewBBDominatesNewBBSucc)
101 for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
103 if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
104 NewBBDominatesNewBBSucc = false;
109 // The other scenario where the new block can dominate its successors are when
110 // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
112 if (!NewBBDominatesNewBBSucc) {
113 NewBBDominatesNewBBSucc = true;
114 for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
116 if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
117 NewBBDominatesNewBBSucc = false;
123 // Find NewBB's immediate dominator and create new dominator tree node for
125 BasicBlock *NewBBIDom = 0;
127 for (i = 0; i < PredBlocks.size(); ++i)
128 if (isReachableFromEntry(PredBlocks[i])) {
129 NewBBIDom = PredBlocks[i];
132 assert(i != PredBlocks.size() && "No reachable preds?");
133 for (i = i + 1; i < PredBlocks.size(); ++i) {
134 if (isReachableFromEntry(PredBlocks[i]))
135 NewBBIDom = findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
137 assert(NewBBIDom && "No immediate dominator found??");
139 // Create the new dominator tree node... and set the idom of NewBB.
140 DomTreeNode *NewBBNode = addNewBlock(NewBB, NewBBIDom);
142 // If NewBB strictly dominates other blocks, then it is now the immediate
143 // dominator of NewBBSucc. Update the dominator tree as appropriate.
144 if (NewBBDominatesNewBBSucc) {
145 DomTreeNode *NewBBSuccNode = getNode(NewBBSucc);
146 changeImmediateDominator(NewBBSuccNode, NewBBNode);
150 unsigned DominatorTree::DFSPass(BasicBlock *V, unsigned N) {
151 // This is more understandable as a recursive algorithm, but we can't use the
152 // recursive algorithm due to stack depth issues. Keep it here for
153 // documentation purposes.
155 InfoRec &VInfo = Info[Roots[i]];
159 Vertex.push_back(V); // Vertex[n] = V;
160 //Info[V].Ancestor = 0; // Ancestor[n] = 0
161 //Info[V].Child = 0; // Child[v] = 0
162 VInfo.Size = 1; // Size[v] = 1
164 for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
165 InfoRec &SuccVInfo = Info[*SI];
166 if (SuccVInfo.Semi == 0) {
167 SuccVInfo.Parent = V;
172 std::vector<std::pair<BasicBlock*, unsigned> > Worklist;
173 Worklist.push_back(std::make_pair(V, 0U));
174 while (!Worklist.empty()) {
175 BasicBlock *BB = Worklist.back().first;
176 unsigned NextSucc = Worklist.back().second;
178 // First time we visited this BB?
180 InfoRec &BBInfo = Info[BB];
184 Vertex.push_back(BB); // Vertex[n] = V;
185 //BBInfo[V].Ancestor = 0; // Ancestor[n] = 0
186 //BBInfo[V].Child = 0; // Child[v] = 0
187 BBInfo.Size = 1; // Size[v] = 1
190 // If we are done with this block, remove it from the worklist.
191 if (NextSucc == BB->getTerminator()->getNumSuccessors()) {
196 // Otherwise, increment the successor number for the next time we get to it.
197 ++Worklist.back().second;
199 // Visit the successor next, if it isn't already visited.
200 BasicBlock *Succ = BB->getTerminator()->getSuccessor(NextSucc);
202 InfoRec &SuccVInfo = Info[Succ];
203 if (SuccVInfo.Semi == 0) {
204 SuccVInfo.Parent = BB;
205 Worklist.push_back(std::make_pair(Succ, 0U));
212 void DominatorTree::Compress(BasicBlock *VIn) {
214 std::vector<BasicBlock *> Work;
215 SmallPtrSet<BasicBlock *, 32> Visited;
216 BasicBlock *VInAncestor = Info[VIn].Ancestor;
217 InfoRec &VInVAInfo = Info[VInAncestor];
219 if (VInVAInfo.Ancestor != 0)
222 while (!Work.empty()) {
223 BasicBlock *V = Work.back();
224 InfoRec &VInfo = Info[V];
225 BasicBlock *VAncestor = VInfo.Ancestor;
226 InfoRec &VAInfo = Info[VAncestor];
228 // Process Ancestor first
229 if (Visited.insert(VAncestor) &&
230 VAInfo.Ancestor != 0) {
231 Work.push_back(VAncestor);
236 // Update VInfo based on Ancestor info
237 if (VAInfo.Ancestor == 0)
239 BasicBlock *VAncestorLabel = VAInfo.Label;
240 BasicBlock *VLabel = VInfo.Label;
241 if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
242 VInfo.Label = VAncestorLabel;
243 VInfo.Ancestor = VAInfo.Ancestor;
247 BasicBlock *DominatorTree::Eval(BasicBlock *V) {
248 InfoRec &VInfo = Info[V];
249 #if !BALANCE_IDOM_TREE
250 // Higher-complexity but faster implementation
251 if (VInfo.Ancestor == 0)
256 // Lower-complexity but slower implementation
257 if (VInfo.Ancestor == 0)
260 BasicBlock *VLabel = VInfo.Label;
262 BasicBlock *VAncestorLabel = Info[VInfo.Ancestor].Label;
263 if (Info[VAncestorLabel].Semi >= Info[VLabel].Semi)
266 return VAncestorLabel;
270 void DominatorTree::Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo){
271 #if !BALANCE_IDOM_TREE
272 // Higher-complexity but faster implementation
275 // Lower-complexity but slower implementation
276 BasicBlock *WLabel = WInfo.Label;
277 unsigned WLabelSemi = Info[WLabel].Semi;
279 InfoRec *SInfo = &Info[S];
281 BasicBlock *SChild = SInfo->Child;
282 InfoRec *SChildInfo = &Info[SChild];
284 while (WLabelSemi < Info[SChildInfo->Label].Semi) {
285 BasicBlock *SChildChild = SChildInfo->Child;
286 if (SInfo->Size+Info[SChildChild].Size >= 2*SChildInfo->Size) {
287 SChildInfo->Ancestor = S;
288 SInfo->Child = SChild = SChildChild;
289 SChildInfo = &Info[SChild];
291 SChildInfo->Size = SInfo->Size;
292 S = SInfo->Ancestor = SChild;
294 SChild = SChildChild;
295 SChildInfo = &Info[SChild];
299 InfoRec &VInfo = Info[V];
300 SInfo->Label = WLabel;
302 assert(V != W && "The optimization here will not work in this case!");
303 unsigned WSize = WInfo.Size;
304 unsigned VSize = (VInfo.Size += WSize);
307 std::swap(S, VInfo.Child);
317 void DominatorTree::calculate(Function &F) {
318 BasicBlock* Root = Roots[0];
320 // Add a node for the root...
321 DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
325 // Step #1: Number blocks in depth-first order and initialize variables used
326 // in later stages of the algorithm.
327 unsigned N = DFSPass(Root, 0);
329 for (unsigned i = N; i >= 2; --i) {
330 BasicBlock *W = Vertex[i];
331 InfoRec &WInfo = Info[W];
333 // Step #2: Calculate the semidominators of all vertices
334 for (pred_iterator PI = pred_begin(W), E = pred_end(W); PI != E; ++PI)
335 if (Info.count(*PI)) { // Only if this predecessor is reachable!
336 unsigned SemiU = Info[Eval(*PI)].Semi;
337 if (SemiU < WInfo.Semi)
341 Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
343 BasicBlock *WParent = WInfo.Parent;
344 Link(WParent, W, WInfo);
346 // Step #3: Implicitly define the immediate dominator of vertices
347 std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
348 while (!WParentBucket.empty()) {
349 BasicBlock *V = WParentBucket.back();
350 WParentBucket.pop_back();
351 BasicBlock *U = Eval(V);
352 IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
356 // Step #4: Explicitly define the immediate dominator of each vertex
357 for (unsigned i = 2; i <= N; ++i) {
358 BasicBlock *W = Vertex[i];
359 BasicBlock *&WIDom = IDoms[W];
360 if (WIDom != Vertex[Info[W].Semi])
361 WIDom = IDoms[WIDom];
364 // Loop over all of the reachable blocks in the function...
365 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
366 if (BasicBlock *ImmDom = getIDom(I)) { // Reachable block.
367 DomTreeNode *BBNode = DomTreeNodes[I];
368 if (BBNode) continue; // Haven't calculated this node yet?
370 // Get or calculate the node for the immediate dominator
371 DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
373 // Add a new tree node for this BasicBlock, and link it as a child of
375 DomTreeNode *C = new DomTreeNode(I, IDomNode);
376 DomTreeNodes[I] = IDomNode->addChild(C);
379 // Free temporary memory used to construct idom's
382 std::vector<BasicBlock*>().swap(Vertex);
387 void DominatorTreeBase::updateDFSNumbers() {
389 // Iterate over all nodes in depth first order.
390 for (unsigned i = 0, e = Roots.size(); i != e; ++i)
391 for (df_iterator<BasicBlock*> I = df_begin(Roots[i]),
392 E = df_end(Roots[i]); I != E; ++I) {
394 DomTreeNode *BBNode = getNode(BB);
396 if (!BBNode->getIDom())
397 BBNode->assignDFSNumber(dfsnum);
404 /// isReachableFromEntry - Return true if A is dominated by the entry
405 /// block of the function containing it.
406 const bool DominatorTreeBase::isReachableFromEntry(BasicBlock* A) {
407 assert (!isPostDominator()
408 && "This is not implemented for post dominators");
409 return dominates(&A->getParent()->getEntryBlock(), A);
412 // dominates - Return true if A dominates B. THis performs the
413 // special checks necessary if A and B are in the same basic block.
414 bool DominatorTreeBase::dominates(Instruction *A, Instruction *B) {
415 BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
416 if (BBA != BBB) return dominates(BBA, BBB);
418 // It is not possible to determine dominance between two PHI nodes
419 // based on their ordering.
420 if (isa<PHINode>(A) && isa<PHINode>(B))
423 // Loop through the basic block until we find A or B.
424 BasicBlock::iterator I = BBA->begin();
425 for (; &*I != A && &*I != B; ++I) /*empty*/;
427 if(!IsPostDominators) {
428 // A dominates B if it is found first in the basic block.
431 // A post-dominates B if B is found first in the basic block.
436 // DominatorTreeBase::reset - Free all of the tree node memory.
438 void DominatorTreeBase::reset() {
439 for (DomTreeNodeMapType::iterator I = DomTreeNodes.begin(),
440 E = DomTreeNodes.end(); I != E; ++I)
442 DomTreeNodes.clear();
449 /// findNearestCommonDominator - Find nearest common dominator basic block
450 /// for basic block A and B. If there is no such block then return NULL.
451 BasicBlock *DominatorTreeBase::findNearestCommonDominator(BasicBlock *A,
454 assert (!isPostDominator()
455 && "This is not implemented for post dominators");
456 assert (A->getParent() == B->getParent()
457 && "Two blocks are not in same function");
459 // If either A or B is a entry block then it is nearest common dominator.
460 BasicBlock &Entry = A->getParent()->getEntryBlock();
461 if (A == &Entry || B == &Entry)
464 // If B dominates A then B is nearest common dominator.
468 // If A dominates B then A is nearest common dominator.
472 DomTreeNode *NodeA = getNode(A);
473 DomTreeNode *NodeB = getNode(B);
475 // Collect NodeA dominators set.
476 SmallPtrSet<DomTreeNode*, 16> NodeADoms;
477 NodeADoms.insert(NodeA);
478 DomTreeNode *IDomA = NodeA->getIDom();
480 NodeADoms.insert(IDomA);
481 IDomA = IDomA->getIDom();
484 // Walk NodeB immediate dominators chain and find common dominator node.
485 DomTreeNode *IDomB = NodeB->getIDom();
487 if (NodeADoms.count(IDomB) != 0)
488 return IDomB->getBlock();
490 IDomB = IDomB->getIDom();
496 /// assignDFSNumber - Assign In and Out numbers while walking dominator tree
498 void DomTreeNode::assignDFSNumber(int num) {
499 std::vector<DomTreeNode *> workStack;
500 SmallPtrSet<DomTreeNode *, 32> Visited;
502 workStack.push_back(this);
503 Visited.insert(this);
504 this->DFSNumIn = num++;
506 while (!workStack.empty()) {
507 DomTreeNode *Node = workStack.back();
509 bool visitChild = false;
510 for (std::vector<DomTreeNode*>::iterator DI = Node->begin(),
511 E = Node->end(); DI != E && !visitChild; ++DI) {
512 DomTreeNode *Child = *DI;
513 if (!Visited.insert(Child))
517 Child->DFSNumIn = num++;
518 workStack.push_back(Child);
521 // If we reach here means all children are visited
522 Node->DFSNumOut = num++;
523 workStack.pop_back();
528 void DomTreeNode::setIDom(DomTreeNode *NewIDom) {
529 assert(IDom && "No immediate dominator?");
530 if (IDom != NewIDom) {
531 std::vector<DomTreeNode*>::iterator I =
532 std::find(IDom->Children.begin(), IDom->Children.end(), this);
533 assert(I != IDom->Children.end() &&
534 "Not in immediate dominator children set!");
535 // I am no longer your child...
536 IDom->Children.erase(I);
538 // Switch to new dominator
540 IDom->Children.push_back(this);
544 DomTreeNode *DominatorTree::getNodeForBlock(BasicBlock *BB) {
545 DomTreeNode *&BBNode = DomTreeNodes[BB];
546 if (BBNode) return BBNode;
548 // Haven't calculated this node yet? Get or calculate the node for the
549 // immediate dominator.
550 BasicBlock *IDom = getIDom(BB);
551 DomTreeNode *IDomNode = getNodeForBlock(IDom);
553 // Add a new tree node for this BasicBlock, and link it as a child of
555 DomTreeNode *C = new DomTreeNode(BB, IDomNode);
556 return DomTreeNodes[BB] = IDomNode->addChild(C);
559 static std::ostream &operator<<(std::ostream &o,
560 const DomTreeNode *Node) {
561 if (Node->getBlock())
562 WriteAsOperand(o, Node->getBlock(), false);
564 o << " <<exit node>>";
568 static void PrintDomTree(const DomTreeNode *N, std::ostream &o,
570 o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
571 for (DomTreeNode::const_iterator I = N->begin(), E = N->end();
573 PrintDomTree(*I, o, Lev+1);
576 void DominatorTreeBase::print(std::ostream &o, const Module* ) const {
577 o << "=============================--------------------------------\n"
578 << "Inorder Dominator Tree:\n";
579 PrintDomTree(getRootNode(), o, 1);
582 void DominatorTreeBase::dump() {
586 bool DominatorTree::runOnFunction(Function &F) {
587 reset(); // Reset from the last time we were run...
588 Roots.push_back(&F.getEntryBlock());
593 //===----------------------------------------------------------------------===//
594 // DominanceFrontier Implementation
595 //===----------------------------------------------------------------------===//
597 char DominanceFrontier::ID = 0;
598 static RegisterPass<DominanceFrontier>
599 G("domfrontier", "Dominance Frontier Construction", true);
601 // NewBB is split and now it has one successor. Update dominace frontier to
602 // reflect this change.
603 void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
605 assert(NewBB->getTerminator()->getNumSuccessors() == 1
606 && "NewBB should have a single successor!");
607 BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
609 std::vector<BasicBlock*> PredBlocks;
610 for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
612 PredBlocks.push_back(*PI);
614 if (PredBlocks.empty())
615 // If NewBB does not have any predecessors then it is a entry block.
616 // In this case, NewBB and its successor NewBBSucc dominates all
620 DominatorTree &DT = getAnalysis<DominatorTree>();
621 bool NewBBDominatesNewBBSucc = true;
622 if (!DT.dominates(NewBB, NewBBSucc))
623 NewBBDominatesNewBBSucc = false;
625 // NewBBSucc inherites original NewBB frontier.
626 DominanceFrontier::iterator NewBBI = find(NewBB);
627 if (NewBBI != end()) {
628 DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
629 DominanceFrontier::DomSetType NewBBSuccSet;
630 NewBBSuccSet.insert(NewBBSet.begin(), NewBBSet.end());
631 addBasicBlock(NewBBSucc, NewBBSuccSet);
634 // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
635 // DF(PredBlocks[0]) without the stuff that the new block does not dominate
637 if (NewBBDominatesNewBBSucc) {
638 DominanceFrontier::iterator DFI = find(PredBlocks[0]);
640 DominanceFrontier::DomSetType Set = DFI->second;
641 // Filter out stuff in Set that we do not dominate a predecessor of.
642 for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
643 E = Set.end(); SetI != E;) {
644 bool DominatesPred = false;
645 for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
647 if (DT.dominates(NewBB, *PI))
648 DominatesPred = true;
655 if (NewBBI != end()) {
656 DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
657 NewBBSet.insert(Set.begin(), Set.end());
659 addBasicBlock(NewBB, Set);
663 // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
664 // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
665 // NewBBSucc)). NewBBSucc is the single successor of NewBB.
666 DominanceFrontier::DomSetType NewDFSet;
667 NewDFSet.insert(NewBBSucc);
668 addBasicBlock(NewBB, NewDFSet);
671 // Now we must loop over all of the dominance frontiers in the function,
672 // replacing occurrences of NewBBSucc with NewBB in some cases. All
673 // blocks that dominate a block in PredBlocks and contained NewBBSucc in
674 // their dominance frontier must be updated to contain NewBB instead.
676 for (Function::iterator FI = NewBB->getParent()->begin(),
677 FE = NewBB->getParent()->end(); FI != FE; ++FI) {
678 DominanceFrontier::iterator DFI = find(FI);
679 if (DFI == end()) continue; // unreachable block.
681 // Only consider dominators of NewBBSucc
682 if (!DFI->second.count(NewBBSucc)) continue;
684 bool BlockDominatesAny = false;
685 for (std::vector<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
686 BE = PredBlocks.end(); BI != BE; ++BI) {
687 if (DT.dominates(FI, *BI)) {
688 BlockDominatesAny = true;
693 if (BlockDominatesAny) {
694 // If NewBBSucc should not stay in our dominator frontier, remove it.
695 // We remove it unless there is a predecessor of NewBBSucc that we
696 // dominate, but we don't strictly dominate NewBBSucc.
697 bool ShouldRemove = true;
698 if ((BasicBlock*)FI == NewBBSucc
699 || !DT.dominates(FI, NewBBSucc)) {
700 // Okay, we know that PredDom does not strictly dominate NewBBSucc.
701 // Check to see if it dominates any predecessors of NewBBSucc.
702 for (pred_iterator PI = pred_begin(NewBBSucc),
703 E = pred_end(NewBBSucc); PI != E; ++PI)
704 if (DT.dominates(FI, *PI)) {
705 ShouldRemove = false;
710 removeFromFrontier(DFI, NewBBSucc);
711 addToFrontier(DFI, NewBB);
720 class DFCalculateWorkObject {
722 DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
723 const DomTreeNode *N,
724 const DomTreeNode *PN)
725 : currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
726 BasicBlock *currentBB;
727 BasicBlock *parentBB;
728 const DomTreeNode *Node;
729 const DomTreeNode *parentNode;
733 const DominanceFrontier::DomSetType &
734 DominanceFrontier::calculate(const DominatorTree &DT,
735 const DomTreeNode *Node) {
736 BasicBlock *BB = Node->getBlock();
737 DomSetType *Result = NULL;
739 std::vector<DFCalculateWorkObject> workList;
740 SmallPtrSet<BasicBlock *, 32> visited;
742 workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
744 DFCalculateWorkObject *currentW = &workList.back();
745 assert (currentW && "Missing work object.");
747 BasicBlock *currentBB = currentW->currentBB;
748 BasicBlock *parentBB = currentW->parentBB;
749 const DomTreeNode *currentNode = currentW->Node;
750 const DomTreeNode *parentNode = currentW->parentNode;
751 assert (currentBB && "Invalid work object. Missing current Basic Block");
752 assert (currentNode && "Invalid work object. Missing current Node");
753 DomSetType &S = Frontiers[currentBB];
755 // Visit each block only once.
756 if (visited.count(currentBB) == 0) {
757 visited.insert(currentBB);
759 // Loop over CFG successors to calculate DFlocal[currentNode]
760 for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
762 // Does Node immediately dominate this successor?
763 if (DT[*SI]->getIDom() != currentNode)
768 // At this point, S is DFlocal. Now we union in DFup's of our children...
769 // Loop through and visit the nodes that Node immediately dominates (Node's
770 // children in the IDomTree)
771 bool visitChild = false;
772 for (DomTreeNode::const_iterator NI = currentNode->begin(),
773 NE = currentNode->end(); NI != NE; ++NI) {
774 DomTreeNode *IDominee = *NI;
775 BasicBlock *childBB = IDominee->getBlock();
776 if (visited.count(childBB) == 0) {
777 workList.push_back(DFCalculateWorkObject(childBB, currentBB,
778 IDominee, currentNode));
783 // If all children are visited or there is any child then pop this block
784 // from the workList.
792 DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
793 DomSetType &parentSet = Frontiers[parentBB];
794 for (; CDFI != CDFE; ++CDFI) {
795 if (!DT.properlyDominates(parentNode, DT[*CDFI]))
796 parentSet.insert(*CDFI);
801 } while (!workList.empty());
806 void DominanceFrontierBase::print(std::ostream &o, const Module* ) const {
807 for (const_iterator I = begin(), E = end(); I != E; ++I) {
808 o << " DomFrontier for BB";
810 WriteAsOperand(o, I->first, false);
812 o << " <<exit node>>";
813 o << " is:\t" << I->second << "\n";
817 void DominanceFrontierBase::dump() {