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GenericDomTreeConstruction.h
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1 //===- GenericDomTreeConstruction.h - Dominator 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 /// \file
10 ///
11 /// Generic dominator tree construction - This file provides routines to
12 /// construct immediate dominator information for a flow-graph based on the
13 /// Semi-NCA algorithm described in this dissertation:
14 ///
15 /// Linear-Time Algorithms for Dominators and Related Problems
16 /// Loukas Georgiadis, Princeton University, November 2005, pp. 21-23:
17 /// ftp://ftp.cs.princeton.edu/reports/2005/737.pdf
18 ///
19 /// This implements the O(n*log(n)) versions of EVAL and LINK, because it turns
20 /// out that the theoretically slower O(n*log(n)) implementation is actually
21 /// faster than the almost-linear O(n*alpha(n)) version, even for large CFGs.
22 ///
23 /// The file uses the Depth Based Search algorithm to perform incremental
24 /// updates (insertion and deletions). The implemented algorithm is based on
25 /// this publication:
26 ///
27 /// An Experimental Study of Dynamic Dominators
28 /// Loukas Georgiadis, et al., April 12 2016, pp. 5-7, 9-10:
29 /// https://arxiv.org/pdf/1604.02711.pdf
30 ///
31 //===----------------------------------------------------------------------===//
32 
33 #ifndef LLVM_SUPPORT_GENERICDOMTREECONSTRUCTION_H
34 #define LLVM_SUPPORT_GENERICDOMTREECONSTRUCTION_H
35 
36 #include <queue>
37 #include "llvm/ADT/ArrayRef.h"
38 #include "llvm/ADT/DenseSet.h"
41 #include "llvm/ADT/SmallPtrSet.h"
42 #include "llvm/Support/Debug.h"
44 
45 #define DEBUG_TYPE "dom-tree-builder"
46 
47 namespace llvm {
48 namespace DomTreeBuilder {
49 
50 template <typename DomTreeT>
51 struct SemiNCAInfo {
52  using NodePtr = typename DomTreeT::NodePtr;
53  using NodeT = typename DomTreeT::NodeType;
55  using RootsT = decltype(DomTreeT::Roots);
56  static constexpr bool IsPostDom = DomTreeT::IsPostDominator;
57 
58  // Information record used by Semi-NCA during tree construction.
59  struct InfoRec {
60  unsigned DFSNum = 0;
61  unsigned Parent = 0;
62  unsigned Semi = 0;
63  NodePtr Label = nullptr;
64  NodePtr IDom = nullptr;
66  };
67 
68  // Number to node mapping is 1-based. Initialize the mapping to start with
69  // a dummy element.
70  std::vector<NodePtr> NumToNode = {nullptr};
72 
73  using UpdateT = typename DomTreeT::UpdateType;
74  struct BatchUpdateInfo {
77 
78  // In order to be able to walk a CFG that is out of sync with the CFG
79  // DominatorTree last knew about, use the list of updates to reconstruct
80  // previous CFG versions of the current CFG. For each node, we store a set
81  // of its virtually added/deleted future successors and predecessors.
82  // Note that these children are from the future relative to what the
83  // DominatorTree knows about -- using them to gets us some snapshot of the
84  // CFG from the past (relative to the state of the CFG).
87  // Remembers if the whole tree was recalculated at some point during the
88  // current batch update.
89  bool IsRecalculated = false;
90  };
91 
94 
95  // If BUI is a nullptr, then there's no batch update in progress.
96  SemiNCAInfo(BatchUpdatePtr BUI) : BatchUpdates(BUI) {}
97 
98  void clear() {
99  NumToNode = {nullptr}; // Restore to initial state with a dummy start node.
100  NodeToInfo.clear();
101  // Don't reset the pointer to BatchUpdateInfo here -- if there's an update
102  // in progress, we need this information to continue it.
103  }
104 
105  template <bool Inverse>
106  struct ChildrenGetter {
108 
109  static ResultTy Get(NodePtr N, std::integral_constant<bool, false>) {
110  auto RChildren = reverse(children<NodePtr>(N));
111  return ResultTy(RChildren.begin(), RChildren.end());
112  }
113 
114  static ResultTy Get(NodePtr N, std::integral_constant<bool, true>) {
115  auto IChildren = inverse_children<NodePtr>(N);
116  return ResultTy(IChildren.begin(), IChildren.end());
117  }
118 
119  using Tag = std::integral_constant<bool, Inverse>;
120 
121  // The function below is the core part of the batch updater. It allows the
122  // Depth Based Search algorithm to perform incremental updates in lockstep
123  // with updates to the CFG. We emulated lockstep CFG updates by getting its
124  // next snapshots by reverse-applying future updates.
126  ResultTy Res = Get(N, Tag());
127  // If there's no batch update in progress, simply return node's children.
128  if (!BUI) return Res;
129 
130  // CFG children are actually its *most current* children, and we have to
131  // reverse-apply the future updates to get the node's children at the
132  // point in time the update was performed.
133  auto &FutureChildren = (Inverse != IsPostDom) ? BUI->FuturePredecessors
134  : BUI->FutureSuccessors;
135  auto FCIt = FutureChildren.find(N);
136  if (FCIt == FutureChildren.end()) return Res;
137 
138  for (auto ChildAndKind : FCIt->second) {
139  const NodePtr Child = ChildAndKind.getPointer();
140  const UpdateKind UK = ChildAndKind.getInt();
141 
142  // Reverse-apply the future update.
143  if (UK == UpdateKind::Insert) {
144  // If there's an insertion in the future, it means that the edge must
145  // exist in the current CFG, but was not present in it before.
146  assert(llvm::find(Res, Child) != Res.end()
147  && "Expected child not found in the CFG");
148  Res.erase(std::remove(Res.begin(), Res.end(), Child), Res.end());
149  DEBUG(dbgs() << "\tHiding edge " << BlockNamePrinter(N) << " -> "
150  << BlockNamePrinter(Child) << "\n");
151  } else {
152  // If there's an deletion in the future, it means that the edge cannot
153  // exist in the current CFG, but existed in it before.
154  assert(llvm::find(Res, Child) == Res.end() &&
155  "Unexpected child found in the CFG");
156  DEBUG(dbgs() << "\tShowing virtual edge " << BlockNamePrinter(N)
157  << " -> " << BlockNamePrinter(Child) << "\n");
158  Res.push_back(Child);
159  }
160  }
161 
162  return Res;
163  }
164  };
165 
166  NodePtr getIDom(NodePtr BB) const {
167  auto InfoIt = NodeToInfo.find(BB);
168  if (InfoIt == NodeToInfo.end()) return nullptr;
169 
170  return InfoIt->second.IDom;
171  }
172 
173  TreeNodePtr getNodeForBlock(NodePtr BB, DomTreeT &DT) {
174  if (TreeNodePtr Node = DT.getNode(BB)) return Node;
175 
176  // Haven't calculated this node yet? Get or calculate the node for the
177  // immediate dominator.
178  NodePtr IDom = getIDom(BB);
179 
180  assert(IDom || DT.DomTreeNodes[nullptr]);
181  TreeNodePtr IDomNode = getNodeForBlock(IDom, DT);
182 
183  // Add a new tree node for this NodeT, and link it as a child of
184  // IDomNode
185  return (DT.DomTreeNodes[BB] = IDomNode->addChild(
187  .get();
188  }
189 
190  static bool AlwaysDescend(NodePtr, NodePtr) { return true; }
191 
194 
195  BlockNamePrinter(NodePtr Block) : N(Block) {}
196  BlockNamePrinter(TreeNodePtr TN) : N(TN ? TN->getBlock() : nullptr) {}
197 
199  if (!BP.N)
200  O << "nullptr";
201  else
202  BP.N->printAsOperand(O, false);
203 
204  return O;
205  }
206  };
207 
208  // Custom DFS implementation which can skip nodes based on a provided
209  // predicate. It also collects ReverseChildren so that we don't have to spend
210  // time getting predecessors in SemiNCA.
211  //
212  // If IsReverse is set to true, the DFS walk will be performed backwards
213  // relative to IsPostDom -- using reverse edges for dominators and forward
214  // edges for postdominators.
215  template <bool IsReverse = false, typename DescendCondition>
216  unsigned runDFS(NodePtr V, unsigned LastNum, DescendCondition Condition,
217  unsigned AttachToNum) {
218  assert(V);
219  SmallVector<NodePtr, 64> WorkList = {V};
220  if (NodeToInfo.count(V) != 0) NodeToInfo[V].Parent = AttachToNum;
221 
222  while (!WorkList.empty()) {
223  const NodePtr BB = WorkList.pop_back_val();
224  auto &BBInfo = NodeToInfo[BB];
225 
226  // Visited nodes always have positive DFS numbers.
227  if (BBInfo.DFSNum != 0) continue;
228  BBInfo.DFSNum = BBInfo.Semi = ++LastNum;
229  BBInfo.Label = BB;
230  NumToNode.push_back(BB);
231 
232  constexpr bool Direction = IsReverse != IsPostDom; // XOR.
233  for (const NodePtr Succ :
234  ChildrenGetter<Direction>::Get(BB, BatchUpdates)) {
235  const auto SIT = NodeToInfo.find(Succ);
236  // Don't visit nodes more than once but remember to collect
237  // ReverseChildren.
238  if (SIT != NodeToInfo.end() && SIT->second.DFSNum != 0) {
239  if (Succ != BB) SIT->second.ReverseChildren.push_back(BB);
240  continue;
241  }
242 
243  if (!Condition(BB, Succ)) continue;
244 
245  // It's fine to add Succ to the map, because we know that it will be
246  // visited later.
247  auto &SuccInfo = NodeToInfo[Succ];
248  WorkList.push_back(Succ);
249  SuccInfo.Parent = LastNum;
250  SuccInfo.ReverseChildren.push_back(BB);
251  }
252  }
253 
254  return LastNum;
255  }
256 
257  NodePtr eval(NodePtr VIn, unsigned LastLinked) {
258  auto &VInInfo = NodeToInfo[VIn];
259  if (VInInfo.DFSNum < LastLinked)
260  return VIn;
261 
263  SmallPtrSet<NodePtr, 32> Visited;
264 
265  if (VInInfo.Parent >= LastLinked)
266  Work.push_back(VIn);
267 
268  while (!Work.empty()) {
269  NodePtr V = Work.back();
270  auto &VInfo = NodeToInfo[V];
271  NodePtr VAncestor = NumToNode[VInfo.Parent];
272 
273  // Process Ancestor first
274  if (Visited.insert(VAncestor).second && VInfo.Parent >= LastLinked) {
275  Work.push_back(VAncestor);
276  continue;
277  }
278  Work.pop_back();
279 
280  // Update VInfo based on Ancestor info
281  if (VInfo.Parent < LastLinked)
282  continue;
283 
284  auto &VAInfo = NodeToInfo[VAncestor];
285  NodePtr VAncestorLabel = VAInfo.Label;
286  NodePtr VLabel = VInfo.Label;
287  if (NodeToInfo[VAncestorLabel].Semi < NodeToInfo[VLabel].Semi)
288  VInfo.Label = VAncestorLabel;
289  VInfo.Parent = VAInfo.Parent;
290  }
291 
292  return VInInfo.Label;
293  }
294 
295  // This function requires DFS to be run before calling it.
296  void runSemiNCA(DomTreeT &DT, const unsigned MinLevel = 0) {
297  const unsigned NextDFSNum(NumToNode.size());
298  // Initialize IDoms to spanning tree parents.
299  for (unsigned i = 1; i < NextDFSNum; ++i) {
300  const NodePtr V = NumToNode[i];
301  auto &VInfo = NodeToInfo[V];
302  VInfo.IDom = NumToNode[VInfo.Parent];
303  }
304 
305  // Step #1: Calculate the semidominators of all vertices.
306  for (unsigned i = NextDFSNum - 1; i >= 2; --i) {
307  NodePtr W = NumToNode[i];
308  auto &WInfo = NodeToInfo[W];
309 
310  // Initialize the semi dominator to point to the parent node.
311  WInfo.Semi = WInfo.Parent;
312  for (const auto &N : WInfo.ReverseChildren) {
313  if (NodeToInfo.count(N) == 0) // Skip unreachable predecessors.
314  continue;
315 
316  const TreeNodePtr TN = DT.getNode(N);
317  // Skip predecessors whose level is above the subtree we are processing.
318  if (TN && TN->getLevel() < MinLevel)
319  continue;
320 
321  unsigned SemiU = NodeToInfo[eval(N, i + 1)].Semi;
322  if (SemiU < WInfo.Semi) WInfo.Semi = SemiU;
323  }
324  }
325 
326  // Step #2: Explicitly define the immediate dominator of each vertex.
327  // IDom[i] = NCA(SDom[i], SpanningTreeParent(i)).
328  // Note that the parents were stored in IDoms and later got invalidated
329  // during path compression in Eval.
330  for (unsigned i = 2; i < NextDFSNum; ++i) {
331  const NodePtr W = NumToNode[i];
332  auto &WInfo = NodeToInfo[W];
333  const unsigned SDomNum = NodeToInfo[NumToNode[WInfo.Semi]].DFSNum;
334  NodePtr WIDomCandidate = WInfo.IDom;
335  while (NodeToInfo[WIDomCandidate].DFSNum > SDomNum)
336  WIDomCandidate = NodeToInfo[WIDomCandidate].IDom;
337 
338  WInfo.IDom = WIDomCandidate;
339  }
340  }
341 
342  // PostDominatorTree always has a virtual root that represents a virtual CFG
343  // node that serves as a single exit from the function. All the other exits
344  // (CFG nodes with terminators and nodes in infinite loops are logically
345  // connected to this virtual CFG exit node).
346  // This functions maps a nullptr CFG node to the virtual root tree node.
347  void addVirtualRoot() {
348  assert(IsPostDom && "Only postdominators have a virtual root");
349  assert(NumToNode.size() == 1 && "SNCAInfo must be freshly constructed");
350 
351  auto &BBInfo = NodeToInfo[nullptr];
352  BBInfo.DFSNum = BBInfo.Semi = 1;
353  BBInfo.Label = nullptr;
354 
355  NumToNode.push_back(nullptr); // NumToNode[1] = nullptr;
356  }
357 
358  // For postdominators, nodes with no forward successors are trivial roots that
359  // are always selected as tree roots. Roots with forward successors correspond
360  // to CFG nodes within infinite loops.
361  static bool HasForwardSuccessors(const NodePtr N, BatchUpdatePtr BUI) {
362  assert(N && "N must be a valid node");
363  return !ChildrenGetter<false>::Get(N, BUI).empty();
364  }
365 
366  static NodePtr GetEntryNode(const DomTreeT &DT) {
367  assert(DT.Parent && "Parent not set");
369  }
370 
371  // Finds all roots without relaying on the set of roots already stored in the
372  // tree.
373  // We define roots to be some non-redundant set of the CFG nodes
374  static RootsT FindRoots(const DomTreeT &DT, BatchUpdatePtr BUI) {
375  assert(DT.Parent && "Parent pointer is not set");
376  RootsT Roots;
377 
378  // For dominators, function entry CFG node is always a tree root node.
379  if (!IsPostDom) {
380  Roots.push_back(GetEntryNode(DT));
381  return Roots;
382  }
383 
384  SemiNCAInfo SNCA(BUI);
385 
386  // PostDominatorTree always has a virtual root.
387  SNCA.addVirtualRoot();
388  unsigned Num = 1;
389 
390  DEBUG(dbgs() << "\t\tLooking for trivial roots\n");
391 
392  // Step #1: Find all the trivial roots that are going to will definitely
393  // remain tree roots.
394  unsigned Total = 0;
395  // It may happen that there are some new nodes in the CFG that are result of
396  // the ongoing batch update, but we cannot really pretend that they don't
397  // exist -- we won't see any outgoing or incoming edges to them, so it's
398  // fine to discover them here, as they would end up appearing in the CFG at
399  // some point anyway.
400  for (const NodePtr N : nodes(DT.Parent)) {
401  ++Total;
402  // If it has no *successors*, it is definitely a root.
403  if (!HasForwardSuccessors(N, BUI)) {
404  Roots.push_back(N);
405  // Run DFS not to walk this part of CFG later.
406  Num = SNCA.runDFS(N, Num, AlwaysDescend, 1);
407  DEBUG(dbgs() << "Found a new trivial root: " << BlockNamePrinter(N)
408  << "\n");
409  DEBUG(dbgs() << "Last visited node: "
410  << BlockNamePrinter(SNCA.NumToNode[Num]) << "\n");
411  }
412  }
413 
414  DEBUG(dbgs() << "\t\tLooking for non-trivial roots\n");
415 
416  // Step #2: Find all non-trivial root candidates. Those are CFG nodes that
417  // are reverse-unreachable were not visited by previous DFS walks (i.e. CFG
418  // nodes in infinite loops).
419  bool HasNonTrivialRoots = false;
420  // Accounting for the virtual exit, see if we had any reverse-unreachable
421  // nodes.
422  if (Total + 1 != Num) {
423  HasNonTrivialRoots = true;
424  // Make another DFS pass over all other nodes to find the
425  // reverse-unreachable blocks, and find the furthest paths we'll be able
426  // to make.
427  // Note that this looks N^2, but it's really 2N worst case, if every node
428  // is unreachable. This is because we are still going to only visit each
429  // unreachable node once, we may just visit it in two directions,
430  // depending on how lucky we get.
431  SmallPtrSet<NodePtr, 4> ConnectToExitBlock;
432  for (const NodePtr I : nodes(DT.Parent)) {
433  if (SNCA.NodeToInfo.count(I) == 0) {
434  DEBUG(dbgs() << "\t\t\tVisiting node " << BlockNamePrinter(I)
435  << "\n");
436  // Find the furthest away we can get by following successors, then
437  // follow them in reverse. This gives us some reasonable answer about
438  // the post-dom tree inside any infinite loop. In particular, it
439  // guarantees we get to the farthest away point along *some*
440  // path. This also matches the GCC's behavior.
441  // If we really wanted a totally complete picture of dominance inside
442  // this infinite loop, we could do it with SCC-like algorithms to find
443  // the lowest and highest points in the infinite loop. In theory, it
444  // would be nice to give the canonical backedge for the loop, but it's
445  // expensive and does not always lead to a minimal set of roots.
446  DEBUG(dbgs() << "\t\t\tRunning forward DFS\n");
447 
448  const unsigned NewNum = SNCA.runDFS<true>(I, Num, AlwaysDescend, Num);
449  const NodePtr FurthestAway = SNCA.NumToNode[NewNum];
450  DEBUG(dbgs() << "\t\t\tFound a new furthest away node "
451  << "(non-trivial root): "
452  << BlockNamePrinter(FurthestAway) << "\n");
453  ConnectToExitBlock.insert(FurthestAway);
454  Roots.push_back(FurthestAway);
455  DEBUG(dbgs() << "\t\t\tPrev DFSNum: " << Num << ", new DFSNum: "
456  << NewNum << "\n\t\t\tRemoving DFS info\n");
457  for (unsigned i = NewNum; i > Num; --i) {
458  const NodePtr N = SNCA.NumToNode[i];
459  DEBUG(dbgs() << "\t\t\t\tRemoving DFS info for "
460  << BlockNamePrinter(N) << "\n");
461  SNCA.NodeToInfo.erase(N);
462  SNCA.NumToNode.pop_back();
463  }
464  const unsigned PrevNum = Num;
465  DEBUG(dbgs() << "\t\t\tRunning reverse DFS\n");
466  Num = SNCA.runDFS(FurthestAway, Num, AlwaysDescend, 1);
467  for (unsigned i = PrevNum + 1; i <= Num; ++i)
468  DEBUG(dbgs() << "\t\t\t\tfound node "
469  << BlockNamePrinter(SNCA.NumToNode[i]) << "\n");
470  }
471  }
472  }
473 
474  DEBUG(dbgs() << "Total: " << Total << ", Num: " << Num << "\n");
475  DEBUG(dbgs() << "Discovered CFG nodes:\n");
476  DEBUG(for (size_t i = 0; i <= Num; ++i) dbgs()
477  << i << ": " << BlockNamePrinter(SNCA.NumToNode[i]) << "\n");
478 
479  assert((Total + 1 == Num) && "Everything should have been visited");
480 
481  // Step #3: If we found some non-trivial roots, make them non-redundant.
482  if (HasNonTrivialRoots) RemoveRedundantRoots(DT, BUI, Roots);
483 
484  DEBUG(dbgs() << "Found roots: ");
485  DEBUG(for (auto *Root : Roots) dbgs() << BlockNamePrinter(Root) << " ");
486  DEBUG(dbgs() << "\n");
487 
488  return Roots;
489  }
490 
491  // This function only makes sense for postdominators.
492  // We define roots to be some set of CFG nodes where (reverse) DFS walks have
493  // to start in order to visit all the CFG nodes (including the
494  // reverse-unreachable ones).
495  // When the search for non-trivial roots is done it may happen that some of
496  // the non-trivial roots are reverse-reachable from other non-trivial roots,
497  // which makes them redundant. This function removes them from the set of
498  // input roots.
499  static void RemoveRedundantRoots(const DomTreeT &DT, BatchUpdatePtr BUI,
500  RootsT &Roots) {
501  assert(IsPostDom && "This function is for postdominators only");
502  DEBUG(dbgs() << "Removing redundant roots\n");
503 
504  SemiNCAInfo SNCA(BUI);
505 
506  for (unsigned i = 0; i < Roots.size(); ++i) {
507  auto &Root = Roots[i];
508  // Trivial roots are always non-redundant.
509  if (!HasForwardSuccessors(Root, BUI)) continue;
510  DEBUG(dbgs() << "\tChecking if " << BlockNamePrinter(Root)
511  << " remains a root\n");
512  SNCA.clear();
513  // Do a forward walk looking for the other roots.
514  const unsigned Num = SNCA.runDFS<true>(Root, 0, AlwaysDescend, 0);
515  // Skip the start node and begin from the second one (note that DFS uses
516  // 1-based indexing).
517  for (unsigned x = 2; x <= Num; ++x) {
518  const NodePtr N = SNCA.NumToNode[x];
519  // If we wound another root in a (forward) DFS walk, remove the current
520  // root from the set of roots, as it is reverse-reachable from the other
521  // one.
522  if (llvm::find(Roots, N) != Roots.end()) {
523  DEBUG(dbgs() << "\tForward DFS walk found another root "
524  << BlockNamePrinter(N) << "\n\tRemoving root "
525  << BlockNamePrinter(Root) << "\n");
526  std::swap(Root, Roots.back());
527  Roots.pop_back();
528 
529  // Root at the back takes the current root's place.
530  // Start the next loop iteration with the same index.
531  --i;
532  break;
533  }
534  }
535  }
536  }
537 
538  template <typename DescendCondition>
539  void doFullDFSWalk(const DomTreeT &DT, DescendCondition DC) {
540  if (!IsPostDom) {
541  assert(DT.Roots.size() == 1 && "Dominators should have a singe root");
542  runDFS(DT.Roots[0], 0, DC, 0);
543  return;
544  }
545 
546  addVirtualRoot();
547  unsigned Num = 1;
548  for (const NodePtr Root : DT.Roots) Num = runDFS(Root, Num, DC, 0);
549  }
550 
551  static void CalculateFromScratch(DomTreeT &DT, BatchUpdatePtr BUI) {
552  auto *Parent = DT.Parent;
553  DT.reset();
554  DT.Parent = Parent;
555  SemiNCAInfo SNCA(nullptr); // Since we are rebuilding the whole tree,
556  // there's no point doing it incrementally.
557 
558  // Step #0: Number blocks in depth-first order and initialize variables used
559  // in later stages of the algorithm.
560  DT.Roots = FindRoots(DT, nullptr);
561  SNCA.doFullDFSWalk(DT, AlwaysDescend);
562 
563  SNCA.runSemiNCA(DT);
564  if (BUI) {
565  BUI->IsRecalculated = true;
566  DEBUG(dbgs() << "DomTree recalculated, skipping future batch updates\n");
567  }
568 
569  if (DT.Roots.empty()) return;
570 
571  // Add a node for the root. If the tree is a PostDominatorTree it will be
572  // the virtual exit (denoted by (BasicBlock *) nullptr) which postdominates
573  // all real exits (including multiple exit blocks, infinite loops).
574  NodePtr Root = IsPostDom ? nullptr : DT.Roots[0];
575 
576  DT.RootNode = (DT.DomTreeNodes[Root] =
577  llvm::make_unique<DomTreeNodeBase<NodeT>>(Root, nullptr))
578  .get();
579  SNCA.attachNewSubtree(DT, DT.RootNode);
580  }
581 
582  void attachNewSubtree(DomTreeT& DT, const TreeNodePtr AttachTo) {
583  // Attach the first unreachable block to AttachTo.
584  NodeToInfo[NumToNode[1]].IDom = AttachTo->getBlock();
585  // Loop over all of the discovered blocks in the function...
586  for (size_t i = 1, e = NumToNode.size(); i != e; ++i) {
587  NodePtr W = NumToNode[i];
588  DEBUG(dbgs() << "\tdiscovered a new reachable node "
589  << BlockNamePrinter(W) << "\n");
590 
591  // Don't replace this with 'count', the insertion side effect is important
592  if (DT.DomTreeNodes[W]) continue; // Haven't calculated this node yet?
593 
594  NodePtr ImmDom = getIDom(W);
595 
596  // Get or calculate the node for the immediate dominator.
597  TreeNodePtr IDomNode = getNodeForBlock(ImmDom, DT);
598 
599  // Add a new tree node for this BasicBlock, and link it as a child of
600  // IDomNode.
601  DT.DomTreeNodes[W] = IDomNode->addChild(
603  }
604  }
605 
606  void reattachExistingSubtree(DomTreeT &DT, const TreeNodePtr AttachTo) {
607  NodeToInfo[NumToNode[1]].IDom = AttachTo->getBlock();
608  for (size_t i = 1, e = NumToNode.size(); i != e; ++i) {
609  const NodePtr N = NumToNode[i];
610  const TreeNodePtr TN = DT.getNode(N);
611  assert(TN);
612  const TreeNodePtr NewIDom = DT.getNode(NodeToInfo[N].IDom);
613  TN->setIDom(NewIDom);
614  }
615  }
616 
617  // Helper struct used during edge insertions.
618  struct InsertionInfo {
619  using BucketElementTy = std::pair<unsigned, TreeNodePtr>;
621  bool operator()(const BucketElementTy &First,
622  const BucketElementTy &Second) const {
623  return First.first > Second.first;
624  }
625  };
626 
627  std::priority_queue<BucketElementTy, SmallVector<BucketElementTy, 8>,
629  Bucket; // Queue of tree nodes sorted by level in descending order.
634  };
635 
636  static void InsertEdge(DomTreeT &DT, const BatchUpdatePtr BUI,
637  const NodePtr From, const NodePtr To) {
638  assert((From || IsPostDom) &&
639  "From has to be a valid CFG node or a virtual root");
640  assert(To && "Cannot be a nullptr");
641  DEBUG(dbgs() << "Inserting edge " << BlockNamePrinter(From) << " -> "
642  << BlockNamePrinter(To) << "\n");
643  TreeNodePtr FromTN = DT.getNode(From);
644 
645  if (!FromTN) {
646  // Ignore edges from unreachable nodes for (forward) dominators.
647  if (!IsPostDom) return;
648 
649  // The unreachable node becomes a new root -- a tree node for it.
650  TreeNodePtr VirtualRoot = DT.getNode(nullptr);
651  FromTN =
652  (DT.DomTreeNodes[From] = VirtualRoot->addChild(
653  llvm::make_unique<DomTreeNodeBase<NodeT>>(From, VirtualRoot)))
654  .get();
655  DT.Roots.push_back(From);
656  }
657 
658  DT.DFSInfoValid = false;
659 
660  const TreeNodePtr ToTN = DT.getNode(To);
661  if (!ToTN)
662  InsertUnreachable(DT, BUI, FromTN, To);
663  else
664  InsertReachable(DT, BUI, FromTN, ToTN);
665  }
666 
667  // Determines if some existing root becomes reverse-reachable after the
668  // insertion. Rebuilds the whole tree if that situation happens.
669  static bool UpdateRootsBeforeInsertion(DomTreeT &DT, const BatchUpdatePtr BUI,
670  const TreeNodePtr From,
671  const TreeNodePtr To) {
672  assert(IsPostDom && "This function is only for postdominators");
673  // Destination node is not attached to the virtual root, so it cannot be a
674  // root.
675  if (!DT.isVirtualRoot(To->getIDom())) return false;
676 
677  auto RIt = llvm::find(DT.Roots, To->getBlock());
678  if (RIt == DT.Roots.end())
679  return false; // To is not a root, nothing to update.
680 
681  DEBUG(dbgs() << "\t\tAfter the insertion, " << BlockNamePrinter(To)
682  << " is no longer a root\n\t\tRebuilding the tree!!!\n");
683 
684  CalculateFromScratch(DT, BUI);
685  return true;
686  }
687 
688  // Updates the set of roots after insertion or deletion. This ensures that
689  // roots are the same when after a series of updates and when the tree would
690  // be built from scratch.
691  static void UpdateRootsAfterUpdate(DomTreeT &DT, const BatchUpdatePtr BUI) {
692  assert(IsPostDom && "This function is only for postdominators");
693 
694  // The tree has only trivial roots -- nothing to update.
695  if (std::none_of(DT.Roots.begin(), DT.Roots.end(), [BUI](const NodePtr N) {
696  return HasForwardSuccessors(N, BUI);
697  }))
698  return;
699 
700  // Recalculate the set of roots.
701  auto Roots = FindRoots(DT, BUI);
702  if (DT.Roots.size() != Roots.size() ||
703  !std::is_permutation(DT.Roots.begin(), DT.Roots.end(), Roots.begin())) {
704  // The roots chosen in the CFG have changed. This is because the
705  // incremental algorithm does not really know or use the set of roots and
706  // can make a different (implicit) decision about which node within an
707  // infinite loop becomes a root.
708 
709  DEBUG(dbgs() << "Roots are different in updated trees\n"
710  << "The entire tree needs to be rebuilt\n");
711  // It may be possible to update the tree without recalculating it, but
712  // we do not know yet how to do it, and it happens rarely in practise.
713  CalculateFromScratch(DT, BUI);
714  return;
715  }
716  }
717 
718  // Handles insertion to a node already in the dominator tree.
719  static void InsertReachable(DomTreeT &DT, const BatchUpdatePtr BUI,
720  const TreeNodePtr From, const TreeNodePtr To) {
721  DEBUG(dbgs() << "\tReachable " << BlockNamePrinter(From->getBlock())
722  << " -> " << BlockNamePrinter(To->getBlock()) << "\n");
723  if (IsPostDom && UpdateRootsBeforeInsertion(DT, BUI, From, To)) return;
724  // DT.findNCD expects both pointers to be valid. When From is a virtual
725  // root, then its CFG block pointer is a nullptr, so we have to 'compute'
726  // the NCD manually.
727  const NodePtr NCDBlock =
728  (From->getBlock() && To->getBlock())
729  ? DT.findNearestCommonDominator(From->getBlock(), To->getBlock())
730  : nullptr;
731  assert(NCDBlock || DT.isPostDominator());
732  const TreeNodePtr NCD = DT.getNode(NCDBlock);
733  assert(NCD);
734 
735  DEBUG(dbgs() << "\t\tNCA == " << BlockNamePrinter(NCD) << "\n");
736  const TreeNodePtr ToIDom = To->getIDom();
737 
738  // Nothing affected -- NCA property holds.
739  // (Based on the lemma 2.5 from the second paper.)
740  if (NCD == To || NCD == ToIDom) return;
741 
742  // Identify and collect affected nodes.
743  InsertionInfo II;
744  DEBUG(dbgs() << "Marking " << BlockNamePrinter(To) << " as affected\n");
745  II.Affected.insert(To);
746  const unsigned ToLevel = To->getLevel();
747  DEBUG(dbgs() << "Putting " << BlockNamePrinter(To) << " into a Bucket\n");
748  II.Bucket.push({ToLevel, To});
749 
750  while (!II.Bucket.empty()) {
751  const TreeNodePtr CurrentNode = II.Bucket.top().second;
752  const unsigned CurrentLevel = CurrentNode->getLevel();
753  II.Bucket.pop();
754  DEBUG(dbgs() << "\tAdding to Visited and AffectedQueue: "
755  << BlockNamePrinter(CurrentNode) << "\n");
756 
757  II.Visited.insert({CurrentNode, CurrentLevel});
758  II.AffectedQueue.push_back(CurrentNode);
759 
760  // Discover and collect affected successors of the current node.
761  VisitInsertion(DT, BUI, CurrentNode, CurrentLevel, NCD, II);
762  }
763 
764  // Finish by updating immediate dominators and levels.
765  UpdateInsertion(DT, BUI, NCD, II);
766  }
767 
768  // Visits an affected node and collect its affected successors.
769  static void VisitInsertion(DomTreeT &DT, const BatchUpdatePtr BUI,
770  const TreeNodePtr TN, const unsigned RootLevel,
771  const TreeNodePtr NCD, InsertionInfo &II) {
772  const unsigned NCDLevel = NCD->getLevel();
773  DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << ", RootLevel "
774  << RootLevel << "\n");
775 
776  SmallVector<TreeNodePtr, 8> Stack = {TN};
777  assert(TN->getBlock() && II.Visited.count(TN) && "Preconditions!");
778 
779  SmallPtrSet<TreeNodePtr, 8> Processed;
780 
781  do {
782  TreeNodePtr Next = Stack.pop_back_val();
783  DEBUG(dbgs() << " Next: " << BlockNamePrinter(Next) << "\n");
784 
785  for (const NodePtr Succ :
787  const TreeNodePtr SuccTN = DT.getNode(Succ);
788  assert(SuccTN && "Unreachable successor found at reachable insertion");
789  const unsigned SuccLevel = SuccTN->getLevel();
790 
791  DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ) << ", level = "
792  << SuccLevel << "\n");
793 
794  // Do not process the same node multiple times.
795  if (Processed.count(Next) > 0)
796  continue;
797 
798  // Succ dominated by subtree From -- not affected.
799  // (Based on the lemma 2.5 from the second paper.)
800  if (SuccLevel > RootLevel) {
801  DEBUG(dbgs() << "\t\tDominated by subtree From\n");
802  if (II.Visited.count(SuccTN) != 0) {
803  DEBUG(dbgs() << "\t\t\talready visited at level "
804  << II.Visited[SuccTN] << "\n\t\t\tcurrent level "
805  << RootLevel << ")\n");
806 
807  // A node can be necessary to visit again if we see it again at
808  // a lower level than before.
809  if (II.Visited[SuccTN] >= RootLevel)
810  continue;
811  }
812 
813  DEBUG(dbgs() << "\t\tMarking visited not affected "
814  << BlockNamePrinter(Succ) << "\n");
815  II.Visited.insert({SuccTN, RootLevel});
816  II.VisitedNotAffectedQueue.push_back(SuccTN);
817  Stack.push_back(SuccTN);
818  } else if ((SuccLevel > NCDLevel + 1) &&
819  II.Affected.count(SuccTN) == 0) {
820  DEBUG(dbgs() << "\t\tMarking affected and adding "
821  << BlockNamePrinter(Succ) << " to a Bucket\n");
822  II.Affected.insert(SuccTN);
823  II.Bucket.push({SuccLevel, SuccTN});
824  }
825  }
826 
827  Processed.insert(Next);
828  } while (!Stack.empty());
829  }
830 
831  // Updates immediate dominators and levels after insertion.
832  static void UpdateInsertion(DomTreeT &DT, const BatchUpdatePtr BUI,
833  const TreeNodePtr NCD, InsertionInfo &II) {
834  DEBUG(dbgs() << "Updating NCD = " << BlockNamePrinter(NCD) << "\n");
835 
836  for (const TreeNodePtr TN : II.AffectedQueue) {
837  DEBUG(dbgs() << "\tIDom(" << BlockNamePrinter(TN)
838  << ") = " << BlockNamePrinter(NCD) << "\n");
839  TN->setIDom(NCD);
840  }
841 
843  if (IsPostDom) UpdateRootsAfterUpdate(DT, BUI);
844  }
845 
847  DEBUG(dbgs() << "Updating levels for visited but not affected nodes\n");
848 
849  for (const TreeNodePtr TN : II.VisitedNotAffectedQueue) {
850  DEBUG(dbgs() << "\tlevel(" << BlockNamePrinter(TN) << ") = ("
851  << BlockNamePrinter(TN->getIDom()) << ") "
852  << TN->getIDom()->getLevel() << " + 1\n");
853  TN->UpdateLevel();
854  }
855  }
856 
857  // Handles insertion to previously unreachable nodes.
858  static void InsertUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI,
859  const TreeNodePtr From, const NodePtr To) {
860  DEBUG(dbgs() << "Inserting " << BlockNamePrinter(From)
861  << " -> (unreachable) " << BlockNamePrinter(To) << "\n");
862 
863  // Collect discovered edges to already reachable nodes.
864  SmallVector<std::pair<NodePtr, TreeNodePtr>, 8> DiscoveredEdgesToReachable;
865  // Discover and connect nodes that became reachable with the insertion.
866  ComputeUnreachableDominators(DT, BUI, To, From, DiscoveredEdgesToReachable);
867 
868  DEBUG(dbgs() << "Inserted " << BlockNamePrinter(From)
869  << " -> (prev unreachable) " << BlockNamePrinter(To) << "\n");
870 
871  // Used the discovered edges and inset discovered connecting (incoming)
872  // edges.
873  for (const auto &Edge : DiscoveredEdgesToReachable) {
874  DEBUG(dbgs() << "\tInserting discovered connecting edge "
875  << BlockNamePrinter(Edge.first) << " -> "
876  << BlockNamePrinter(Edge.second) << "\n");
877  InsertReachable(DT, BUI, DT.getNode(Edge.first), Edge.second);
878  }
879  }
880 
881  // Connects nodes that become reachable with an insertion.
883  DomTreeT &DT, const BatchUpdatePtr BUI, const NodePtr Root,
884  const TreeNodePtr Incoming,
885  SmallVectorImpl<std::pair<NodePtr, TreeNodePtr>>
886  &DiscoveredConnectingEdges) {
887  assert(!DT.getNode(Root) && "Root must not be reachable");
888 
889  // Visit only previously unreachable nodes.
890  auto UnreachableDescender = [&DT, &DiscoveredConnectingEdges](NodePtr From,
891  NodePtr To) {
892  const TreeNodePtr ToTN = DT.getNode(To);
893  if (!ToTN) return true;
894 
895  DiscoveredConnectingEdges.push_back({From, ToTN});
896  return false;
897  };
898 
899  SemiNCAInfo SNCA(BUI);
900  SNCA.runDFS(Root, 0, UnreachableDescender, 0);
901  SNCA.runSemiNCA(DT);
902  SNCA.attachNewSubtree(DT, Incoming);
903 
904  DEBUG(dbgs() << "After adding unreachable nodes\n");
905  }
906 
907  static void DeleteEdge(DomTreeT &DT, const BatchUpdatePtr BUI,
908  const NodePtr From, const NodePtr To) {
909  assert(From && To && "Cannot disconnect nullptrs");
910  DEBUG(dbgs() << "Deleting edge " << BlockNamePrinter(From) << " -> "
911  << BlockNamePrinter(To) << "\n");
912 
913 #ifndef NDEBUG
914  // Ensure that the edge was in fact deleted from the CFG before informing
915  // the DomTree about it.
916  // The check is O(N), so run it only in debug configuration.
917  auto IsSuccessor = [BUI](const NodePtr SuccCandidate, const NodePtr Of) {
918  auto Successors = ChildrenGetter<IsPostDom>::Get(Of, BUI);
919  return llvm::find(Successors, SuccCandidate) != Successors.end();
920  };
921  (void)IsSuccessor;
922  assert(!IsSuccessor(To, From) && "Deleted edge still exists in the CFG!");
923 #endif
924 
925  const TreeNodePtr FromTN = DT.getNode(From);
926  // Deletion in an unreachable subtree -- nothing to do.
927  if (!FromTN) return;
928 
929  const TreeNodePtr ToTN = DT.getNode(To);
930  if (!ToTN) {
931  DEBUG(dbgs() << "\tTo (" << BlockNamePrinter(To)
932  << ") already unreachable -- there is no edge to delete\n");
933  return;
934  }
935 
936  const NodePtr NCDBlock = DT.findNearestCommonDominator(From, To);
937  const TreeNodePtr NCD = DT.getNode(NCDBlock);
938 
939  // If To dominates From -- nothing to do.
940  if (ToTN != NCD) {
941  DT.DFSInfoValid = false;
942 
943  const TreeNodePtr ToIDom = ToTN->getIDom();
944  DEBUG(dbgs() << "\tNCD " << BlockNamePrinter(NCD) << ", ToIDom "
945  << BlockNamePrinter(ToIDom) << "\n");
946 
947  // To remains reachable after deletion.
948  // (Based on the caption under Figure 4. from the second paper.)
949  if (FromTN != ToIDom || HasProperSupport(DT, BUI, ToTN))
950  DeleteReachable(DT, BUI, FromTN, ToTN);
951  else
952  DeleteUnreachable(DT, BUI, ToTN);
953  }
954 
955  if (IsPostDom) UpdateRootsAfterUpdate(DT, BUI);
956  }
957 
958  // Handles deletions that leave destination nodes reachable.
959  static void DeleteReachable(DomTreeT &DT, const BatchUpdatePtr BUI,
960  const TreeNodePtr FromTN,
961  const TreeNodePtr ToTN) {
962  DEBUG(dbgs() << "Deleting reachable " << BlockNamePrinter(FromTN) << " -> "
963  << BlockNamePrinter(ToTN) << "\n");
964  DEBUG(dbgs() << "\tRebuilding subtree\n");
965 
966  // Find the top of the subtree that needs to be rebuilt.
967  // (Based on the lemma 2.6 from the second paper.)
968  const NodePtr ToIDom =
969  DT.findNearestCommonDominator(FromTN->getBlock(), ToTN->getBlock());
970  assert(ToIDom || DT.isPostDominator());
971  const TreeNodePtr ToIDomTN = DT.getNode(ToIDom);
972  assert(ToIDomTN);
973  const TreeNodePtr PrevIDomSubTree = ToIDomTN->getIDom();
974  // Top of the subtree to rebuild is the root node. Rebuild the tree from
975  // scratch.
976  if (!PrevIDomSubTree) {
977  DEBUG(dbgs() << "The entire tree needs to be rebuilt\n");
978  CalculateFromScratch(DT, BUI);
979  return;
980  }
981 
982  // Only visit nodes in the subtree starting at To.
983  const unsigned Level = ToIDomTN->getLevel();
984  auto DescendBelow = [Level, &DT](NodePtr, NodePtr To) {
985  return DT.getNode(To)->getLevel() > Level;
986  };
987 
988  DEBUG(dbgs() << "\tTop of subtree: " << BlockNamePrinter(ToIDomTN) << "\n");
989 
990  SemiNCAInfo SNCA(BUI);
991  SNCA.runDFS(ToIDom, 0, DescendBelow, 0);
992  DEBUG(dbgs() << "\tRunning Semi-NCA\n");
993  SNCA.runSemiNCA(DT, Level);
994  SNCA.reattachExistingSubtree(DT, PrevIDomSubTree);
995  }
996 
997  // Checks if a node has proper support, as defined on the page 3 and later
998  // explained on the page 7 of the second paper.
999  static bool HasProperSupport(DomTreeT &DT, const BatchUpdatePtr BUI,
1000  const TreeNodePtr TN) {
1001  DEBUG(dbgs() << "IsReachableFromIDom " << BlockNamePrinter(TN) << "\n");
1002  for (const NodePtr Pred :
1004  DEBUG(dbgs() << "\tPred " << BlockNamePrinter(Pred) << "\n");
1005  if (!DT.getNode(Pred)) continue;
1006 
1007  const NodePtr Support =
1008  DT.findNearestCommonDominator(TN->getBlock(), Pred);
1009  DEBUG(dbgs() << "\tSupport " << BlockNamePrinter(Support) << "\n");
1010  if (Support != TN->getBlock()) {
1011  DEBUG(dbgs() << "\t" << BlockNamePrinter(TN)
1012  << " is reachable from support "
1013  << BlockNamePrinter(Support) << "\n");
1014  return true;
1015  }
1016  }
1017 
1018  return false;
1019  }
1020 
1021  // Handle deletions that make destination node unreachable.
1022  // (Based on the lemma 2.7 from the second paper.)
1023  static void DeleteUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI,
1024  const TreeNodePtr ToTN) {
1025  DEBUG(dbgs() << "Deleting unreachable subtree " << BlockNamePrinter(ToTN)
1026  << "\n");
1027  assert(ToTN);
1028  assert(ToTN->getBlock());
1029 
1030  if (IsPostDom) {
1031  // Deletion makes a region reverse-unreachable and creates a new root.
1032  // Simulate that by inserting an edge from the virtual root to ToTN and
1033  // adding it as a new root.
1034  DEBUG(dbgs() << "\tDeletion made a region reverse-unreachable\n");
1035  DEBUG(dbgs() << "\tAdding new root " << BlockNamePrinter(ToTN) << "\n");
1036  DT.Roots.push_back(ToTN->getBlock());
1037  InsertReachable(DT, BUI, DT.getNode(nullptr), ToTN);
1038  return;
1039  }
1040 
1041  SmallVector<NodePtr, 16> AffectedQueue;
1042  const unsigned Level = ToTN->getLevel();
1043 
1044  // Traverse destination node's descendants with greater level in the tree
1045  // and collect visited nodes.
1046  auto DescendAndCollect = [Level, &AffectedQueue, &DT](NodePtr, NodePtr To) {
1047  const TreeNodePtr TN = DT.getNode(To);
1048  assert(TN);
1049  if (TN->getLevel() > Level) return true;
1050  if (llvm::find(AffectedQueue, To) == AffectedQueue.end())
1051  AffectedQueue.push_back(To);
1052 
1053  return false;
1054  };
1055 
1056  SemiNCAInfo SNCA(BUI);
1057  unsigned LastDFSNum =
1058  SNCA.runDFS(ToTN->getBlock(), 0, DescendAndCollect, 0);
1059 
1060  TreeNodePtr MinNode = ToTN;
1061 
1062  // Identify the top of the subtree to rebuild by finding the NCD of all
1063  // the affected nodes.
1064  for (const NodePtr N : AffectedQueue) {
1065  const TreeNodePtr TN = DT.getNode(N);
1066  const NodePtr NCDBlock =
1067  DT.findNearestCommonDominator(TN->getBlock(), ToTN->getBlock());
1068  assert(NCDBlock || DT.isPostDominator());
1069  const TreeNodePtr NCD = DT.getNode(NCDBlock);
1070  assert(NCD);
1071 
1072  DEBUG(dbgs() << "Processing affected node " << BlockNamePrinter(TN)
1073  << " with NCD = " << BlockNamePrinter(NCD)
1074  << ", MinNode =" << BlockNamePrinter(MinNode) << "\n");
1075  if (NCD != TN && NCD->getLevel() < MinNode->getLevel()) MinNode = NCD;
1076  }
1077 
1078  // Root reached, rebuild the whole tree from scratch.
1079  if (!MinNode->getIDom()) {
1080  DEBUG(dbgs() << "The entire tree needs to be rebuilt\n");
1081  CalculateFromScratch(DT, BUI);
1082  return;
1083  }
1084 
1085  // Erase the unreachable subtree in reverse preorder to process all children
1086  // before deleting their parent.
1087  for (unsigned i = LastDFSNum; i > 0; --i) {
1088  const NodePtr N = SNCA.NumToNode[i];
1089  const TreeNodePtr TN = DT.getNode(N);
1090  DEBUG(dbgs() << "Erasing node " << BlockNamePrinter(TN) << "\n");
1091 
1092  EraseNode(DT, TN);
1093  }
1094 
1095  // The affected subtree start at the To node -- there's no extra work to do.
1096  if (MinNode == ToTN) return;
1097 
1098  DEBUG(dbgs() << "DeleteUnreachable: running DFS with MinNode = "
1099  << BlockNamePrinter(MinNode) << "\n");
1100  const unsigned MinLevel = MinNode->getLevel();
1101  const TreeNodePtr PrevIDom = MinNode->getIDom();
1102  assert(PrevIDom);
1103  SNCA.clear();
1104 
1105  // Identify nodes that remain in the affected subtree.
1106  auto DescendBelow = [MinLevel, &DT](NodePtr, NodePtr To) {
1107  const TreeNodePtr ToTN = DT.getNode(To);
1108  return ToTN && ToTN->getLevel() > MinLevel;
1109  };
1110  SNCA.runDFS(MinNode->getBlock(), 0, DescendBelow, 0);
1111 
1112  DEBUG(dbgs() << "Previous IDom(MinNode) = " << BlockNamePrinter(PrevIDom)
1113  << "\nRunning Semi-NCA\n");
1114 
1115  // Rebuild the remaining part of affected subtree.
1116  SNCA.runSemiNCA(DT, MinLevel);
1117  SNCA.reattachExistingSubtree(DT, PrevIDom);
1118  }
1119 
1120  // Removes leaf tree nodes from the dominator tree.
1121  static void EraseNode(DomTreeT &DT, const TreeNodePtr TN) {
1122  assert(TN);
1123  assert(TN->getNumChildren() == 0 && "Not a tree leaf");
1124 
1125  const TreeNodePtr IDom = TN->getIDom();
1126  assert(IDom);
1127 
1128  auto ChIt = llvm::find(IDom->Children, TN);
1129  assert(ChIt != IDom->Children.end());
1130  std::swap(*ChIt, IDom->Children.back());
1131  IDom->Children.pop_back();
1132 
1133  DT.DomTreeNodes.erase(TN->getBlock());
1134  }
1135 
1136  //~~
1137  //===--------------------- DomTree Batch Updater --------------------------===
1138  //~~
1139 
1140  static void ApplyUpdates(DomTreeT &DT, ArrayRef<UpdateT> Updates) {
1141  const size_t NumUpdates = Updates.size();
1142  if (NumUpdates == 0)
1143  return;
1144 
1145  // Take the fast path for a single update and avoid running the batch update
1146  // machinery.
1147  if (NumUpdates == 1) {
1148  const auto &Update = Updates.front();
1150  DT.insertEdge(Update.getFrom(), Update.getTo());
1151  else
1152  DT.deleteEdge(Update.getFrom(), Update.getTo());
1153 
1154  return;
1155  }
1156 
1157  BatchUpdateInfo BUI;
1158  LegalizeUpdates(Updates, BUI.Updates);
1159 
1160  const size_t NumLegalized = BUI.Updates.size();
1161  BUI.FutureSuccessors.reserve(NumLegalized);
1162  BUI.FuturePredecessors.reserve(NumLegalized);
1163 
1164  // Use the legalized future updates to initialize future successors and
1165  // predecessors. Note that these sets will only decrease size over time, as
1166  // the next CFG snapshots slowly approach the actual (current) CFG.
1167  for (UpdateT &U : BUI.Updates) {
1168  BUI.FutureSuccessors[U.getFrom()].insert({U.getTo(), U.getKind()});
1169  BUI.FuturePredecessors[U.getTo()].insert({U.getFrom(), U.getKind()});
1170  }
1171 
1172  DEBUG(dbgs() << "About to apply " << NumLegalized << " updates\n");
1173  DEBUG(if (NumLegalized < 32) for (const auto &U
1174  : reverse(BUI.Updates)) dbgs()
1175  << '\t' << U << "\n");
1176  DEBUG(dbgs() << "\n");
1177 
1178  // If the DominatorTree was recalculated at some point, stop the batch
1179  // updates. Full recalculations ignore batch updates and look at the actual
1180  // CFG.
1181  for (size_t i = 0; i < NumLegalized && !BUI.IsRecalculated; ++i)
1182  ApplyNextUpdate(DT, BUI);
1183  }
1184 
1185  // This function serves double purpose:
1186  // a) It removes redundant updates, which makes it easier to reverse-apply
1187  // them when traversing CFG.
1188  // b) It optimizes away updates that cancel each other out, as the end result
1189  // is the same.
1190  //
1191  // It relies on the property of the incremental updates that says that the
1192  // order of updates doesn't matter. This allows us to reorder them and end up
1193  // with the exact same DomTree every time.
1194  //
1195  // Following the same logic, the function doesn't care about the order of
1196  // input updates, so it's OK to pass it an unordered sequence of updates, that
1197  // doesn't make sense when applied sequentially, eg. performing double
1198  // insertions or deletions and then doing an opposite update.
1199  //
1200  // In the future, it should be possible to schedule updates in way that
1201  // minimizes the amount of work needed done during incremental updates.
1202  static void LegalizeUpdates(ArrayRef<UpdateT> AllUpdates,
1203  SmallVectorImpl<UpdateT> &Result) {
1204  DEBUG(dbgs() << "Legalizing " << AllUpdates.size() << " updates\n");
1205  // Count the total number of inserions of each edge.
1206  // Each insertion adds 1 and deletion subtracts 1. The end number should be
1207  // one of {-1 (deletion), 0 (NOP), +1 (insertion)}. Otherwise, the sequence
1208  // of updates contains multiple updates of the same kind and we assert for
1209  // that case.
1210  SmallDenseMap<std::pair<NodePtr, NodePtr>, int, 4> Operations;
1211  Operations.reserve(AllUpdates.size());
1212 
1213  for (const auto &U : AllUpdates) {
1214  NodePtr From = U.getFrom();
1215  NodePtr To = U.getTo();
1216  if (IsPostDom) std::swap(From, To); // Reverse edge for postdominators.
1217 
1218  Operations[{From, To}] += (U.getKind() == UpdateKind::Insert ? 1 : -1);
1219  }
1220 
1221  Result.clear();
1222  Result.reserve(Operations.size());
1223  for (auto &Op : Operations) {
1224  const int NumInsertions = Op.second;
1225  assert(std::abs(NumInsertions) <= 1 && "Unbalanced operations!");
1226  if (NumInsertions == 0) continue;
1227  const UpdateKind UK =
1228  NumInsertions > 0 ? UpdateKind::Insert : UpdateKind::Delete;
1229  Result.push_back({UK, Op.first.first, Op.first.second});
1230  }
1231 
1232  // Make the order consistent by not relying on pointer values within the
1233  // set. Reuse the old Operations map.
1234  // In the future, we should sort by something else to minimize the amount
1235  // of work needed to perform the series of updates.
1236  for (size_t i = 0, e = AllUpdates.size(); i != e; ++i) {
1237  const auto &U = AllUpdates[i];
1238  if (!IsPostDom)
1239  Operations[{U.getFrom(), U.getTo()}] = int(i);
1240  else
1241  Operations[{U.getTo(), U.getFrom()}] = int(i);
1242  }
1243 
1244  std::sort(Result.begin(), Result.end(),
1245  [&Operations](const UpdateT &A, const UpdateT &B) {
1246  return Operations[{A.getFrom(), A.getTo()}] >
1247  Operations[{B.getFrom(), B.getTo()}];
1248  });
1249  }
1250 
1251  static void ApplyNextUpdate(DomTreeT &DT, BatchUpdateInfo &BUI) {
1252  assert(!BUI.Updates.empty() && "No updates to apply!");
1253  UpdateT CurrentUpdate = BUI.Updates.pop_back_val();
1254  DEBUG(dbgs() << "Applying update: " << CurrentUpdate << "\n");
1255 
1256  // Move to the next snapshot of the CFG by removing the reverse-applied
1257  // current update.
1258  auto &FS = BUI.FutureSuccessors[CurrentUpdate.getFrom()];
1259  FS.erase({CurrentUpdate.getTo(), CurrentUpdate.getKind()});
1260  if (FS.empty()) BUI.FutureSuccessors.erase(CurrentUpdate.getFrom());
1261 
1262  auto &FP = BUI.FuturePredecessors[CurrentUpdate.getTo()];
1263  FP.erase({CurrentUpdate.getFrom(), CurrentUpdate.getKind()});
1264  if (FP.empty()) BUI.FuturePredecessors.erase(CurrentUpdate.getTo());
1265 
1266  if (CurrentUpdate.getKind() == UpdateKind::Insert)
1267  InsertEdge(DT, &BUI, CurrentUpdate.getFrom(), CurrentUpdate.getTo());
1268  else
1269  DeleteEdge(DT, &BUI, CurrentUpdate.getFrom(), CurrentUpdate.getTo());
1270  }
1271 
1272  //~~
1273  //===--------------- DomTree correctness verification ---------------------===
1274  //~~
1275 
1276  // Check if the tree has correct roots. A DominatorTree always has a single
1277  // root which is the function's entry node. A PostDominatorTree can have
1278  // multiple roots - one for each node with no successors and for infinite
1279  // loops.
1280  // Running time: O(N).
1281  bool verifyRoots(const DomTreeT &DT) {
1282  if (!DT.Parent && !DT.Roots.empty()) {
1283  errs() << "Tree has no parent but has roots!\n";
1284  errs().flush();
1285  return false;
1286  }
1287 
1288  if (!IsPostDom) {
1289  if (DT.Roots.empty()) {
1290  errs() << "Tree doesn't have a root!\n";
1291  errs().flush();
1292  return false;
1293  }
1294 
1295  if (DT.getRoot() != GetEntryNode(DT)) {
1296  errs() << "Tree's root is not its parent's entry node!\n";
1297  errs().flush();
1298  return false;
1299  }
1300  }
1301 
1302  RootsT ComputedRoots = FindRoots(DT, nullptr);
1303  if (DT.Roots.size() != ComputedRoots.size() ||
1304  !std::is_permutation(DT.Roots.begin(), DT.Roots.end(),
1305  ComputedRoots.begin())) {
1306  errs() << "Tree has different roots than freshly computed ones!\n";
1307  errs() << "\tPDT roots: ";
1308  for (const NodePtr N : DT.Roots) errs() << BlockNamePrinter(N) << ", ";
1309  errs() << "\n\tComputed roots: ";
1310  for (const NodePtr N : ComputedRoots)
1311  errs() << BlockNamePrinter(N) << ", ";
1312  errs() << "\n";
1313  errs().flush();
1314  return false;
1315  }
1316 
1317  return true;
1318  }
1319 
1320  // Checks if the tree contains all reachable nodes in the input graph.
1321  // Running time: O(N).
1322  bool verifyReachability(const DomTreeT &DT) {
1323  clear();
1325 
1326  for (auto &NodeToTN : DT.DomTreeNodes) {
1327  const TreeNodePtr TN = NodeToTN.second.get();
1328  const NodePtr BB = TN->getBlock();
1329 
1330  // Virtual root has a corresponding virtual CFG node.
1331  if (DT.isVirtualRoot(TN)) continue;
1332 
1333  if (NodeToInfo.count(BB) == 0) {
1334  errs() << "DomTree node " << BlockNamePrinter(BB)
1335  << " not found by DFS walk!\n";
1336  errs().flush();
1337 
1338  return false;
1339  }
1340  }
1341 
1342  for (const NodePtr N : NumToNode) {
1343  if (N && !DT.getNode(N)) {
1344  errs() << "CFG node " << BlockNamePrinter(N)
1345  << " not found in the DomTree!\n";
1346  errs().flush();
1347 
1348  return false;
1349  }
1350  }
1351 
1352  return true;
1353  }
1354 
1355  // Check if for every parent with a level L in the tree all of its children
1356  // have level L + 1.
1357  // Running time: O(N).
1358  static bool VerifyLevels(const DomTreeT &DT) {
1359  for (auto &NodeToTN : DT.DomTreeNodes) {
1360  const TreeNodePtr TN = NodeToTN.second.get();
1361  const NodePtr BB = TN->getBlock();
1362  if (!BB) continue;
1363 
1364  const TreeNodePtr IDom = TN->getIDom();
1365  if (!IDom && TN->getLevel() != 0) {
1366  errs() << "Node without an IDom " << BlockNamePrinter(BB)
1367  << " has a nonzero level " << TN->getLevel() << "!\n";
1368  errs().flush();
1369 
1370  return false;
1371  }
1372 
1373  if (IDom && TN->getLevel() != IDom->getLevel() + 1) {
1374  errs() << "Node " << BlockNamePrinter(BB) << " has level "
1375  << TN->getLevel() << " while its IDom "
1376  << BlockNamePrinter(IDom->getBlock()) << " has level "
1377  << IDom->getLevel() << "!\n";
1378  errs().flush();
1379 
1380  return false;
1381  }
1382  }
1383 
1384  return true;
1385  }
1386 
1387  // Check if the computed DFS numbers are correct. Note that DFS info may not
1388  // be valid, and when that is the case, we don't verify the numbers.
1389  // Running time: O(N log(N)).
1390  static bool VerifyDFSNumbers(const DomTreeT &DT) {
1391  if (!DT.DFSInfoValid || !DT.Parent)
1392  return true;
1393 
1394  const NodePtr RootBB = IsPostDom ? nullptr : DT.getRoots()[0];
1395  const TreeNodePtr Root = DT.getNode(RootBB);
1396 
1397  auto PrintNodeAndDFSNums = [](const TreeNodePtr TN) {
1398  errs() << BlockNamePrinter(TN) << " {" << TN->getDFSNumIn() << ", "
1399  << TN->getDFSNumOut() << '}';
1400  };
1401 
1402  // Verify the root's DFS In number. Although DFS numbering would also work
1403  // if we started from some other value, we assume 0-based numbering.
1404  if (Root->getDFSNumIn() != 0) {
1405  errs() << "DFSIn number for the tree root is not:\n\t";
1406  PrintNodeAndDFSNums(Root);
1407  errs() << '\n';
1408  errs().flush();
1409  return false;
1410  }
1411 
1412  // For each tree node verify if children's DFS numbers cover their parent's
1413  // DFS numbers with no gaps.
1414  for (const auto &NodeToTN : DT.DomTreeNodes) {
1415  const TreeNodePtr Node = NodeToTN.second.get();
1416 
1417  // Handle tree leaves.
1418  if (Node->getChildren().empty()) {
1419  if (Node->getDFSNumIn() + 1 != Node->getDFSNumOut()) {
1420  errs() << "Tree leaf should have DFSOut = DFSIn + 1:\n\t";
1421  PrintNodeAndDFSNums(Node);
1422  errs() << '\n';
1423  errs().flush();
1424  return false;
1425  }
1426 
1427  continue;
1428  }
1429 
1430  // Make a copy and sort it such that it is possible to check if there are
1431  // no gaps between DFS numbers of adjacent children.
1432  SmallVector<TreeNodePtr, 8> Children(Node->begin(), Node->end());
1433  std::sort(Children.begin(), Children.end(),
1434  [](const TreeNodePtr Ch1, const TreeNodePtr Ch2) {
1435  return Ch1->getDFSNumIn() < Ch2->getDFSNumIn();
1436  });
1437 
1438  auto PrintChildrenError = [Node, &Children, PrintNodeAndDFSNums](
1439  const TreeNodePtr FirstCh, const TreeNodePtr SecondCh) {
1440  assert(FirstCh);
1441 
1442  errs() << "Incorrect DFS numbers for:\n\tParent ";
1443  PrintNodeAndDFSNums(Node);
1444 
1445  errs() << "\n\tChild ";
1446  PrintNodeAndDFSNums(FirstCh);
1447 
1448  if (SecondCh) {
1449  errs() << "\n\tSecond child ";
1450  PrintNodeAndDFSNums(SecondCh);
1451  }
1452 
1453  errs() << "\nAll children: ";
1454  for (const TreeNodePtr Ch : Children) {
1455  PrintNodeAndDFSNums(Ch);
1456  errs() << ", ";
1457  }
1458 
1459  errs() << '\n';
1460  errs().flush();
1461  };
1462 
1463  if (Children.front()->getDFSNumIn() != Node->getDFSNumIn() + 1) {
1464  PrintChildrenError(Children.front(), nullptr);
1465  return false;
1466  }
1467 
1468  if (Children.back()->getDFSNumOut() + 1 != Node->getDFSNumOut()) {
1469  PrintChildrenError(Children.back(), nullptr);
1470  return false;
1471  }
1472 
1473  for (size_t i = 0, e = Children.size() - 1; i != e; ++i) {
1474  if (Children[i]->getDFSNumOut() + 1 != Children[i + 1]->getDFSNumIn()) {
1475  PrintChildrenError(Children[i], Children[i + 1]);
1476  return false;
1477  }
1478  }
1479  }
1480 
1481  return true;
1482  }
1483 
1484  // The below routines verify the correctness of the dominator tree relative to
1485  // the CFG it's coming from. A tree is a dominator tree iff it has two
1486  // properties, called the parent property and the sibling property. Tarjan
1487  // and Lengauer prove (but don't explicitly name) the properties as part of
1488  // the proofs in their 1972 paper, but the proofs are mostly part of proving
1489  // things about semidominators and idoms, and some of them are simply asserted
1490  // based on even earlier papers (see, e.g., lemma 2). Some papers refer to
1491  // these properties as "valid" and "co-valid". See, e.g., "Dominators,
1492  // directed bipolar orders, and independent spanning trees" by Loukas
1493  // Georgiadis and Robert E. Tarjan, as well as "Dominator Tree Verification
1494  // and Vertex-Disjoint Paths " by the same authors.
1495 
1496  // A very simple and direct explanation of these properties can be found in
1497  // "An Experimental Study of Dynamic Dominators", found at
1498  // https://arxiv.org/abs/1604.02711
1499 
1500  // The easiest way to think of the parent property is that it's a requirement
1501  // of being a dominator. Let's just take immediate dominators. For PARENT to
1502  // be an immediate dominator of CHILD, all paths in the CFG must go through
1503  // PARENT before they hit CHILD. This implies that if you were to cut PARENT
1504  // out of the CFG, there should be no paths to CHILD that are reachable. If
1505  // there are, then you now have a path from PARENT to CHILD that goes around
1506  // PARENT and still reaches CHILD, which by definition, means PARENT can't be
1507  // a dominator of CHILD (let alone an immediate one).
1508 
1509  // The sibling property is similar. It says that for each pair of sibling
1510  // nodes in the dominator tree (LEFT and RIGHT) , they must not dominate each
1511  // other. If sibling LEFT dominated sibling RIGHT, it means there are no
1512  // paths in the CFG from sibling LEFT to sibling RIGHT that do not go through
1513  // LEFT, and thus, LEFT is really an ancestor (in the dominator tree) of
1514  // RIGHT, not a sibling.
1515 
1516  // It is possible to verify the parent and sibling properties in
1517  // linear time, but the algorithms are complex. Instead, we do it in a
1518  // straightforward N^2 and N^3 way below, using direct path reachability.
1519 
1520  // Checks if the tree has the parent property: if for all edges from V to W in
1521  // the input graph, such that V is reachable, the parent of W in the tree is
1522  // an ancestor of V in the tree.
1523  // Running time: O(N^2).
1524  //
1525  // This means that if a node gets disconnected from the graph, then all of
1526  // the nodes it dominated previously will now become unreachable.
1527  bool verifyParentProperty(const DomTreeT &DT) {
1528  for (auto &NodeToTN : DT.DomTreeNodes) {
1529  const TreeNodePtr TN = NodeToTN.second.get();
1530  const NodePtr BB = TN->getBlock();
1531  if (!BB || TN->getChildren().empty()) continue;
1532 
1533  DEBUG(dbgs() << "Verifying parent property of node "
1534  << BlockNamePrinter(TN) << "\n");
1535  clear();
1536  doFullDFSWalk(DT, [BB](NodePtr From, NodePtr To) {
1537  return From != BB && To != BB;
1538  });
1539 
1540  for (TreeNodePtr Child : TN->getChildren())
1541  if (NodeToInfo.count(Child->getBlock()) != 0) {
1542  errs() << "Child " << BlockNamePrinter(Child)
1543  << " reachable after its parent " << BlockNamePrinter(BB)
1544  << " is removed!\n";
1545  errs().flush();
1546 
1547  return false;
1548  }
1549  }
1550 
1551  return true;
1552  }
1553 
1554  // Check if the tree has sibling property: if a node V does not dominate a
1555  // node W for all siblings V and W in the tree.
1556  // Running time: O(N^3).
1557  //
1558  // This means that if a node gets disconnected from the graph, then all of its
1559  // siblings will now still be reachable.
1560  bool verifySiblingProperty(const DomTreeT &DT) {
1561  for (auto &NodeToTN : DT.DomTreeNodes) {
1562  const TreeNodePtr TN = NodeToTN.second.get();
1563  const NodePtr BB = TN->getBlock();
1564  if (!BB || TN->getChildren().empty()) continue;
1565 
1566  const auto &Siblings = TN->getChildren();
1567  for (const TreeNodePtr N : Siblings) {
1568  clear();
1569  NodePtr BBN = N->getBlock();
1570  doFullDFSWalk(DT, [BBN](NodePtr From, NodePtr To) {
1571  return From != BBN && To != BBN;
1572  });
1573 
1574  for (const TreeNodePtr S : Siblings) {
1575  if (S == N) continue;
1576 
1577  if (NodeToInfo.count(S->getBlock()) == 0) {
1578  errs() << "Node " << BlockNamePrinter(S)
1579  << " not reachable when its sibling " << BlockNamePrinter(N)
1580  << " is removed!\n";
1581  errs().flush();
1582 
1583  return false;
1584  }
1585  }
1586  }
1587  }
1588 
1589  return true;
1590  }
1591 
1592  // Check if the given tree is the same as a freshly computed one for the same
1593  // Parent.
1594  // Running time: O(N^2), but faster in practise (same as tree construction).
1595  //
1596  // Note that this does not check if that the tree construction algorithm is
1597  // correct and should be only used for fast (but possibly unsound)
1598  // verification.
1599  static bool IsSameAsFreshTree(const DomTreeT &DT) {
1600  DomTreeT FreshTree;
1601  FreshTree.recalculate(*DT.Parent);
1602  const bool Different = DT.compare(FreshTree);
1603 
1604  if (Different) {
1605  errs() << "DominatorTree is different than a freshly computed one!\n"
1606  << "\tCurrent:\n";
1607  DT.print(errs());
1608  errs() << "\n\tFreshly computed tree:\n";
1609  FreshTree.print(errs());
1610  errs().flush();
1611  }
1612 
1613  return !Different;
1614  }
1615 };
1616 
1617 template <class DomTreeT>
1618 void Calculate(DomTreeT &DT) {
1620 }
1621 
1622 template <class DomTreeT>
1623 void InsertEdge(DomTreeT &DT, typename DomTreeT::NodePtr From,
1624  typename DomTreeT::NodePtr To) {
1625  if (DT.isPostDominator()) std::swap(From, To);
1626  SemiNCAInfo<DomTreeT>::InsertEdge(DT, nullptr, From, To);
1627 }
1628 
1629 template <class DomTreeT>
1630 void DeleteEdge(DomTreeT &DT, typename DomTreeT::NodePtr From,
1631  typename DomTreeT::NodePtr To) {
1632  if (DT.isPostDominator()) std::swap(From, To);
1633  SemiNCAInfo<DomTreeT>::DeleteEdge(DT, nullptr, From, To);
1634 }
1635 
1636 template <class DomTreeT>
1637 void ApplyUpdates(DomTreeT &DT,
1640 }
1641 
1642 template <class DomTreeT>
1643 bool Verify(const DomTreeT &DT, typename DomTreeT::VerificationLevel VL) {
1644  SemiNCAInfo<DomTreeT> SNCA(nullptr);
1645  const bool InitialChecks = SNCA.verifyRoots(DT) &&
1646  SNCA.verifyReachability(DT) &&
1647  SNCA.VerifyLevels(DT) && SNCA.VerifyDFSNumbers(DT);
1648 
1649  if (!InitialChecks)
1650  return false;
1651 
1652  switch (VL) {
1654  return SNCA.IsSameAsFreshTree(DT);
1655 
1657  return SNCA.verifyParentProperty(DT) && SNCA.IsSameAsFreshTree(DT);
1658 
1660  bool FullRes
1661  = SNCA.verifyParentProperty(DT) && SNCA.verifySiblingProperty(DT);
1662 
1663  // Postdominators depend on root selection, make sure that a fresh tree
1664  // looks the same.
1665  if (DT.isPostDominator())
1666  FullRes &= SNCA.IsSameAsFreshTree(DT);
1667 
1668  return FullRes;
1669  }
1670  }
1671 
1672  llvm_unreachable("Unhandled DomTree VerificationLevel");
1673 }
1674 
1675 } // namespace DomTreeBuilder
1676 } // namespace llvm
1677 
1678 #undef DEBUG_TYPE
1679 
1680 #endif
const T & front() const
front - Get the first element.
Definition: ArrayRef.h:152
UpdateKind getKind() const
void push_back(const T &Elt)
Definition: SmallVector.h:212
static void UpdateInsertion(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr NCD, InsertionInfo &II)
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
DenseMap< NodePtr, InfoRec > NodeToInfo
static void EraseNode(DomTreeT &DT, const TreeNodePtr TN)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
std::error_code remove(const Twine &path, bool IgnoreNonExisting=true)
Remove path.
static void UpdateRootsAfterUpdate(DomTreeT &DT, const BatchUpdatePtr BUI)
void doFullDFSWalk(const DomTreeT &DT, DescendCondition DC)
SmallDenseMap< TreeNodePtr, unsigned, 8 > Visited
std::enable_if<!std::is_array< T >::value, std::unique_ptr< T > >::type make_unique(Args &&... args)
Constructs a new T() with the given args and returns a unique_ptr<T> which owns the object...
Definition: STLExtras.h:950
void reserve(size_type N)
Definition: SmallVector.h:378
std::priority_queue< BucketElementTy, SmallVector< BucketElementTy, 8 >, DecreasingLevel > Bucket
static bool VerifyLevels(const DomTreeT &DT)
NodeType
ISD::NodeType enum - This enum defines the target-independent operators for a SelectionDAG.
Definition: ISDOpcodes.h:39
static void ApplyNextUpdate(DomTreeT &DT, BatchUpdateInfo &BUI)
NodePtr eval(NodePtr VIn, unsigned LastLinked)
void runSemiNCA(DomTreeT &DT, const unsigned MinLevel=0)
static ManagedStatic< DebugCounter > DC
static void RemoveRedundantRoots(const DomTreeT &DT, BatchUpdatePtr BUI, RootsT &Roots)
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
bool none_of(R &&Range, UnaryPredicate P)
Provide wrappers to std::none_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:828
DenseMap< NodePtr, SmallDenseSet< NodePtrAndKind, 4 > > FutureSuccessors
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:233
static bool IsSameAsFreshTree(const DomTreeT &DT)
bool operator()(const BucketElementTy &First, const BucketElementTy &Second) const
static void DeleteEdge(DomTreeT &DT, const BatchUpdatePtr BUI, const NodePtr From, const NodePtr To)
Base class for the actual dominator tree node.
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
const std::vector< DomTreeNodeBase * > & getChildren() const
static bool HasForwardSuccessors(const NodePtr N, BatchUpdatePtr BUI)
unsigned runDFS(NodePtr V, unsigned LastNum, DescendCondition Condition, unsigned AttachToNum)
unsigned getDFSNumIn() const
getDFSNumIn/getDFSNumOut - These return the DFS visitation order for nodes in the dominator tree...
NodeT * getBlock() const
static ResultTy Get(NodePtr N, std::integral_constant< bool, true >)
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
typename DomTreeT::UpdateType UpdateT
PointerIntPair - This class implements a pair of a pointer and small integer.
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:149
DomTreeNodeBase * getIDom() const
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:116
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
static ResultTy Get(NodePtr N, BatchUpdatePtr BUI)
static void UpdateLevelsAfterInsertion(InsertionInfo &II)
Fast - This calling convention attempts to make calls as fast as possible (e.g.
Definition: CallingConv.h:43
static RootsT FindRoots(const DomTreeT &DT, BatchUpdatePtr BUI)
static void LegalizeUpdates(ArrayRef< UpdateT > AllUpdates, SmallVectorImpl< UpdateT > &Result)
DenseMap< NodePtr, SmallDenseSet< NodePtrAndKind, 4 > > FuturePredecessors
unsigned getDFSNumOut() const
void reserve(size_type NumEntries)
Grow the densemap so that it can contain at least NumEntries items before resizing again...
Definition: DenseMap.h:100
iterator erase(const_iterator CI)
Definition: SmallVector.h:447
static void DeleteReachable(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr FromTN, const TreeNodePtr ToTN)
auto find(R &&Range, const T &Val) -> decltype(adl_begin(Range))
Provide wrappers to std::find which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:835
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static bool UpdateRootsBeforeInsertion(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr From, const TreeNodePtr To)
static void ApplyUpdates(DomTreeT &DT, ArrayRef< UpdateT > Updates)
static void VisitInsertion(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr TN, const unsigned RootLevel, const TreeNodePtr NCD, InsertionInfo &II)
static void CalculateFromScratch(DomTreeT &DT, BatchUpdatePtr BUI)
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
size_t getNumChildren() const
static bool HasProperSupport(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr TN)
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:383
static bool VerifyDFSNumbers(const DomTreeT &DT)
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
Implements a dense probed hash-table based set with some number of buckets stored inline...
Definition: DenseSet.h:239
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:923
static void DeleteUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr ToTN)
bool Verify(const DomTreeT &DT, typename DomTreeT::VerificationLevel VL)
static bool AlwaysDescend(NodePtr, NodePtr)
friend raw_ostream & operator<<(raw_ostream &O, const BlockNamePrinter &BP)
std::unique_ptr< DomTreeNodeBase > addChild(std::unique_ptr< DomTreeNodeBase > C)
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
iterator_range< typename GraphTraits< GraphType >::nodes_iterator > nodes(const GraphType &G)
Definition: GraphTraits.h:102
void attachNewSubtree(DomTreeT &DT, const TreeNodePtr AttachTo)
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
void reattachExistingSubtree(DomTreeT &DT, const TreeNodePtr AttachTo)
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
APFloat abs(APFloat X)
Returns the absolute value of the argument.
Definition: APFloat.h:1213
static NodePtr GetEntryNode(const DomTreeT &DT)
static void InsertEdge(DomTreeT &DT, const BatchUpdatePtr BUI, const NodePtr From, const NodePtr To)
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:141
static void InsertReachable(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr From, const TreeNodePtr To)
static void ComputeUnreachableDominators(DomTreeT &DT, const BatchUpdatePtr BUI, const NodePtr Root, const TreeNodePtr Incoming, SmallVectorImpl< std::pair< NodePtr, TreeNodePtr >> &DiscoveredConnectingEdges)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:44
#define DEBUG(X)
Definition: Debug.h:118
unsigned getLevel() const
This file defines a set of templates that efficiently compute a dominator tree over a generic graph...
static void InsertUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI, const TreeNodePtr From, const NodePtr To)
void sort(Policy policy, RandomAccessIterator Start, RandomAccessIterator End, const Comparator &Comp=Comparator())
Definition: Parallel.h:199
TreeNodePtr getNodeForBlock(NodePtr BB, DomTreeT &DT)
static ResultTy Get(NodePtr N, std::integral_constant< bool, false >)
void setIDom(DomTreeNodeBase *NewIDom)