1 //===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Analysis/LazyCallGraph.h"
11 #include "llvm/ADT/ScopeExit.h"
12 #include "llvm/ADT/Sequence.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/ADT/ScopeExit.h"
15 #include "llvm/IR/CallSite.h"
16 #include "llvm/IR/InstVisitor.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/PassManager.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/GraphWriter.h"
24 #define DEBUG_TYPE "lcg"
26 static void addEdge(SmallVectorImpl<LazyCallGraph::Edge> &Edges,
27 DenseMap<Function *, int> &EdgeIndexMap, Function &F,
28 LazyCallGraph::Edge::Kind EK) {
29 if (!EdgeIndexMap.insert({&F, Edges.size()}).second)
32 DEBUG(dbgs() << " Added callable function: " << F.getName() << "\n");
33 Edges.emplace_back(LazyCallGraph::Edge(F, EK));
36 LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F)
37 : G(&G), F(F), DFSNumber(0), LowLink(0) {
38 DEBUG(dbgs() << " Adding functions called by '" << F.getName()
39 << "' to the graph.\n");
41 SmallVector<Constant *, 16> Worklist;
42 SmallPtrSet<Function *, 4> Callees;
43 SmallPtrSet<Constant *, 16> Visited;
45 // Find all the potential call graph edges in this function. We track both
46 // actual call edges and indirect references to functions. The direct calls
47 // are trivially added, but to accumulate the latter we walk the instructions
48 // and add every operand which is a constant to the worklist to process
51 // Note that we consider *any* function with a definition to be a viable
52 // edge. Even if the function's definition is subject to replacement by
53 // some other module (say, a weak definition) there may still be
54 // optimizations which essentially speculate based on the definition and
55 // a way to check that the specific definition is in fact the one being
56 // used. For example, this could be done by moving the weak definition to
57 // a strong (internal) definition and making the weak definition be an
58 // alias. Then a test of the address of the weak function against the new
59 // strong definition's address would be an effective way to determine the
60 // safety of optimizing a direct call edge.
61 for (BasicBlock &BB : F)
62 for (Instruction &I : BB) {
63 if (auto CS = CallSite(&I))
64 if (Function *Callee = CS.getCalledFunction())
65 if (!Callee->isDeclaration())
66 if (Callees.insert(Callee).second) {
67 Visited.insert(Callee);
68 addEdge(Edges, EdgeIndexMap, *Callee, LazyCallGraph::Edge::Call);
71 for (Value *Op : I.operand_values())
72 if (Constant *C = dyn_cast<Constant>(Op))
73 if (Visited.insert(C).second)
74 Worklist.push_back(C);
77 // We've collected all the constant (and thus potentially function or
78 // function containing) operands to all of the instructions in the function.
79 // Process them (recursively) collecting every function found.
80 visitReferences(Worklist, Visited, [&](Function &F) {
81 addEdge(Edges, EdgeIndexMap, F, LazyCallGraph::Edge::Ref);
85 void LazyCallGraph::Node::insertEdgeInternal(Function &Target, Edge::Kind EK) {
86 if (Node *N = G->lookup(Target))
87 return insertEdgeInternal(*N, EK);
89 EdgeIndexMap.insert({&Target, Edges.size()});
90 Edges.emplace_back(Target, EK);
93 void LazyCallGraph::Node::insertEdgeInternal(Node &TargetN, Edge::Kind EK) {
94 EdgeIndexMap.insert({&TargetN.getFunction(), Edges.size()});
95 Edges.emplace_back(TargetN, EK);
98 void LazyCallGraph::Node::setEdgeKind(Function &TargetF, Edge::Kind EK) {
99 Edges[EdgeIndexMap.find(&TargetF)->second].setKind(EK);
102 void LazyCallGraph::Node::removeEdgeInternal(Function &Target) {
103 auto IndexMapI = EdgeIndexMap.find(&Target);
104 assert(IndexMapI != EdgeIndexMap.end() &&
105 "Target not in the edge set for this caller?");
107 Edges[IndexMapI->second] = Edge();
108 EdgeIndexMap.erase(IndexMapI);
111 void LazyCallGraph::Node::dump() const {
112 dbgs() << *this << '\n';
115 LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) {
116 DEBUG(dbgs() << "Building CG for module: " << M.getModuleIdentifier()
118 for (Function &F : M)
119 if (!F.isDeclaration() && !F.hasLocalLinkage())
120 if (EntryIndexMap.insert({&F, EntryEdges.size()}).second) {
121 DEBUG(dbgs() << " Adding '" << F.getName()
122 << "' to entry set of the graph.\n");
123 EntryEdges.emplace_back(F, Edge::Ref);
126 // Now add entry nodes for functions reachable via initializers to globals.
127 SmallVector<Constant *, 16> Worklist;
128 SmallPtrSet<Constant *, 16> Visited;
129 for (GlobalVariable &GV : M.globals())
130 if (GV.hasInitializer())
131 if (Visited.insert(GV.getInitializer()).second)
132 Worklist.push_back(GV.getInitializer());
134 DEBUG(dbgs() << " Adding functions referenced by global initializers to the "
136 visitReferences(Worklist, Visited, [&](Function &F) {
137 addEdge(EntryEdges, EntryIndexMap, F, LazyCallGraph::Edge::Ref);
140 for (const Edge &E : EntryEdges)
141 RefSCCEntryNodes.push_back(&E.getFunction());
144 LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
145 : BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)),
146 EntryEdges(std::move(G.EntryEdges)),
147 EntryIndexMap(std::move(G.EntryIndexMap)), SCCBPA(std::move(G.SCCBPA)),
148 SCCMap(std::move(G.SCCMap)), LeafRefSCCs(std::move(G.LeafRefSCCs)),
149 DFSStack(std::move(G.DFSStack)),
150 RefSCCEntryNodes(std::move(G.RefSCCEntryNodes)),
151 NextDFSNumber(G.NextDFSNumber) {
155 LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) {
156 BPA = std::move(G.BPA);
157 NodeMap = std::move(G.NodeMap);
158 EntryEdges = std::move(G.EntryEdges);
159 EntryIndexMap = std::move(G.EntryIndexMap);
160 SCCBPA = std::move(G.SCCBPA);
161 SCCMap = std::move(G.SCCMap);
162 LeafRefSCCs = std::move(G.LeafRefSCCs);
163 DFSStack = std::move(G.DFSStack);
164 RefSCCEntryNodes = std::move(G.RefSCCEntryNodes);
165 NextDFSNumber = G.NextDFSNumber;
170 void LazyCallGraph::SCC::dump() const {
171 dbgs() << *this << '\n';
175 void LazyCallGraph::SCC::verify() {
176 assert(OuterRefSCC && "Can't have a null RefSCC!");
177 assert(!Nodes.empty() && "Can't have an empty SCC!");
179 for (Node *N : Nodes) {
180 assert(N && "Can't have a null node!");
181 assert(OuterRefSCC->G->lookupSCC(*N) == this &&
182 "Node does not map to this SCC!");
183 assert(N->DFSNumber == -1 &&
184 "Must set DFS numbers to -1 when adding a node to an SCC!");
185 assert(N->LowLink == -1 &&
186 "Must set low link to -1 when adding a node to an SCC!");
188 assert(E.getNode() && "Can't have an edge to a raw function!");
193 bool LazyCallGraph::SCC::isParentOf(const SCC &C) const {
197 for (Node &N : *this)
198 for (Edge &E : N.calls())
199 if (Node *CalleeN = E.getNode())
200 if (OuterRefSCC->G->lookupSCC(*CalleeN) == &C)
207 bool LazyCallGraph::SCC::isAncestorOf(const SCC &TargetC) const {
208 if (this == &TargetC)
211 LazyCallGraph &G = *OuterRefSCC->G;
213 // Start with this SCC.
214 SmallPtrSet<const SCC *, 16> Visited = {this};
215 SmallVector<const SCC *, 16> Worklist = {this};
217 // Walk down the graph until we run out of edges or find a path to TargetC.
219 const SCC &C = *Worklist.pop_back_val();
221 for (Edge &E : N.calls()) {
222 Node *CalleeN = E.getNode();
225 SCC *CalleeC = G.lookupSCC(*CalleeN);
229 // If the callee's SCC is the TargetC, we're done.
230 if (CalleeC == &TargetC)
233 // If this is the first time we've reached this SCC, put it on the
234 // worklist to recurse through.
235 if (Visited.insert(CalleeC).second)
236 Worklist.push_back(CalleeC);
238 } while (!Worklist.empty());
244 LazyCallGraph::RefSCC::RefSCC(LazyCallGraph &G) : G(&G) {}
246 void LazyCallGraph::RefSCC::dump() const {
247 dbgs() << *this << '\n';
251 void LazyCallGraph::RefSCC::verify() {
252 assert(G && "Can't have a null graph!");
253 assert(!SCCs.empty() && "Can't have an empty SCC!");
255 // Verify basic properties of the SCCs.
256 SmallPtrSet<SCC *, 4> SCCSet;
257 for (SCC *C : SCCs) {
258 assert(C && "Can't have a null SCC!");
260 assert(&C->getOuterRefSCC() == this &&
261 "SCC doesn't think it is inside this RefSCC!");
262 bool Inserted = SCCSet.insert(C).second;
263 assert(Inserted && "Found a duplicate SCC!");
264 auto IndexIt = SCCIndices.find(C);
265 assert(IndexIt != SCCIndices.end() &&
266 "Found an SCC that doesn't have an index!");
269 // Check that our indices map correctly.
270 for (auto &SCCIndexPair : SCCIndices) {
271 SCC *C = SCCIndexPair.first;
272 int i = SCCIndexPair.second;
273 assert(C && "Can't have a null SCC in the indices!");
274 assert(SCCSet.count(C) && "Found an index for an SCC not in the RefSCC!");
275 assert(SCCs[i] == C && "Index doesn't point to SCC!");
278 // Check that the SCCs are in fact in post-order.
279 for (int i = 0, Size = SCCs.size(); i < Size; ++i) {
280 SCC &SourceSCC = *SCCs[i];
281 for (Node &N : SourceSCC)
285 SCC &TargetSCC = *G->lookupSCC(*E.getNode());
286 if (&TargetSCC.getOuterRefSCC() == this) {
287 assert(SCCIndices.find(&TargetSCC)->second <= i &&
288 "Edge between SCCs violates post-order relationship.");
291 assert(TargetSCC.getOuterRefSCC().Parents.count(this) &&
292 "Edge to a RefSCC missing us in its parent set.");
296 // Check that our parents are actually parents.
297 for (RefSCC *ParentRC : Parents) {
298 assert(ParentRC != this && "Cannot be our own parent!");
299 auto HasConnectingEdge = [&] {
300 for (SCC &C : *ParentRC)
303 if (G->lookupRefSCC(*E.getNode()) == this)
307 assert(HasConnectingEdge() && "No edge connects the parent to us!");
312 bool LazyCallGraph::RefSCC::isDescendantOf(const RefSCC &C) const {
313 // Walk up the parents of this SCC and verify that we eventually find C.
314 SmallVector<const RefSCC *, 4> AncestorWorklist;
315 AncestorWorklist.push_back(this);
317 const RefSCC *AncestorC = AncestorWorklist.pop_back_val();
318 if (AncestorC->isChildOf(C))
320 for (const RefSCC *ParentC : AncestorC->Parents)
321 AncestorWorklist.push_back(ParentC);
322 } while (!AncestorWorklist.empty());
327 /// Generic helper that updates a postorder sequence of SCCs for a potentially
328 /// cycle-introducing edge insertion.
330 /// A postorder sequence of SCCs of a directed graph has one fundamental
331 /// property: all deges in the DAG of SCCs point "up" the sequence. That is,
332 /// all edges in the SCC DAG point to prior SCCs in the sequence.
334 /// This routine both updates a postorder sequence and uses that sequence to
335 /// compute the set of SCCs connected into a cycle. It should only be called to
336 /// insert a "downward" edge which will require changing the sequence to
337 /// restore it to a postorder.
339 /// When inserting an edge from an earlier SCC to a later SCC in some postorder
340 /// sequence, all of the SCCs which may be impacted are in the closed range of
341 /// those two within the postorder sequence. The algorithm used here to restore
342 /// the state is as follows:
344 /// 1) Starting from the source SCC, construct a set of SCCs which reach the
345 /// source SCC consisting of just the source SCC. Then scan toward the
346 /// target SCC in postorder and for each SCC, if it has an edge to an SCC
347 /// in the set, add it to the set. Otherwise, the source SCC is not
348 /// a successor, move it in the postorder sequence to immediately before
349 /// the source SCC, shifting the source SCC and all SCCs in the set one
350 /// position toward the target SCC. Stop scanning after processing the
352 /// 2) If the source SCC is now past the target SCC in the postorder sequence,
353 /// and thus the new edge will flow toward the start, we are done.
354 /// 3) Otherwise, starting from the target SCC, walk all edges which reach an
355 /// SCC between the source and the target, and add them to the set of
356 /// connected SCCs, then recurse through them. Once a complete set of the
357 /// SCCs the target connects to is known, hoist the remaining SCCs between
358 /// the source and the target to be above the target. Note that there is no
359 /// need to process the source SCC, it is already known to connect.
360 /// 4) At this point, all of the SCCs in the closed range between the source
361 /// SCC and the target SCC in the postorder sequence are connected,
362 /// including the target SCC and the source SCC. Inserting the edge from
363 /// the source SCC to the target SCC will form a cycle out of precisely
364 /// these SCCs. Thus we can merge all of the SCCs in this closed range into
367 /// This process has various important properties:
368 /// - Only mutates the SCCs when adding the edge actually changes the SCC
370 /// - Never mutates SCCs which are unaffected by the change.
371 /// - Updates the postorder sequence to correctly satisfy the postorder
372 /// constraint after the edge is inserted.
373 /// - Only reorders SCCs in the closed postorder sequence from the source to
374 /// the target, so easy to bound how much has changed even in the ordering.
375 /// - Big-O is the number of edges in the closed postorder range of SCCs from
376 /// source to target.
378 /// This helper routine, in addition to updating the postorder sequence itself
379 /// will also update a map from SCCs to indices within that sequecne.
381 /// The sequence and the map must operate on pointers to the SCC type.
383 /// Two callbacks must be provided. The first computes the subset of SCCs in
384 /// the postorder closed range from the source to the target which connect to
385 /// the source SCC via some (transitive) set of edges. The second computes the
386 /// subset of the same range which the target SCC connects to via some
387 /// (transitive) set of edges. Both callbacks should populate the set argument
389 template <typename SCCT, typename PostorderSequenceT, typename SCCIndexMapT,
390 typename ComputeSourceConnectedSetCallableT,
391 typename ComputeTargetConnectedSetCallableT>
392 static iterator_range<typename PostorderSequenceT::iterator>
393 updatePostorderSequenceForEdgeInsertion(
394 SCCT &SourceSCC, SCCT &TargetSCC, PostorderSequenceT &SCCs,
395 SCCIndexMapT &SCCIndices,
396 ComputeSourceConnectedSetCallableT ComputeSourceConnectedSet,
397 ComputeTargetConnectedSetCallableT ComputeTargetConnectedSet) {
398 int SourceIdx = SCCIndices[&SourceSCC];
399 int TargetIdx = SCCIndices[&TargetSCC];
400 assert(SourceIdx < TargetIdx && "Cannot have equal indices here!");
402 SmallPtrSet<SCCT *, 4> ConnectedSet;
404 // Compute the SCCs which (transitively) reach the source.
405 ComputeSourceConnectedSet(ConnectedSet);
407 // Partition the SCCs in this part of the port-order sequence so only SCCs
408 // connecting to the source remain between it and the target. This is
409 // a benign partition as it preserves postorder.
410 auto SourceI = std::stable_partition(
411 SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx + 1,
412 [&ConnectedSet](SCCT *C) { return !ConnectedSet.count(C); });
413 for (int i = SourceIdx, e = TargetIdx + 1; i < e; ++i)
414 SCCIndices.find(SCCs[i])->second = i;
416 // If the target doesn't connect to the source, then we've corrected the
417 // post-order and there are no cycles formed.
418 if (!ConnectedSet.count(&TargetSCC)) {
419 assert(SourceI > (SCCs.begin() + SourceIdx) &&
420 "Must have moved the source to fix the post-order.");
421 assert(*std::prev(SourceI) == &TargetSCC &&
422 "Last SCC to move should have bene the target.");
424 // Return an empty range at the target SCC indicating there is nothing to
426 return make_range(std::prev(SourceI), std::prev(SourceI));
429 assert(SCCs[TargetIdx] == &TargetSCC &&
430 "Should not have moved target if connected!");
431 SourceIdx = SourceI - SCCs.begin();
432 assert(SCCs[SourceIdx] == &SourceSCC &&
433 "Bad updated index computation for the source SCC!");
436 // See whether there are any remaining intervening SCCs between the source
437 // and target. If so we need to make sure they all are reachable form the
439 if (SourceIdx + 1 < TargetIdx) {
440 ConnectedSet.clear();
441 ComputeTargetConnectedSet(ConnectedSet);
443 // Partition SCCs so that only SCCs reached from the target remain between
444 // the source and the target. This preserves postorder.
445 auto TargetI = std::stable_partition(
446 SCCs.begin() + SourceIdx + 1, SCCs.begin() + TargetIdx + 1,
447 [&ConnectedSet](SCCT *C) { return ConnectedSet.count(C); });
448 for (int i = SourceIdx + 1, e = TargetIdx + 1; i < e; ++i)
449 SCCIndices.find(SCCs[i])->second = i;
450 TargetIdx = std::prev(TargetI) - SCCs.begin();
451 assert(SCCs[TargetIdx] == &TargetSCC &&
452 "Should always end with the target!");
455 // At this point, we know that connecting source to target forms a cycle
456 // because target connects back to source, and we know that all of the SCCs
457 // between the source and target in the postorder sequence participate in that
459 return make_range(SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx);
462 SmallVector<LazyCallGraph::SCC *, 1>
463 LazyCallGraph::RefSCC::switchInternalEdgeToCall(Node &SourceN, Node &TargetN) {
464 assert(!SourceN[TargetN].isCall() && "Must start with a ref edge!");
465 SmallVector<SCC *, 1> DeletedSCCs;
468 // In a debug build, verify the RefSCC is valid to start with and when this
471 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
474 SCC &SourceSCC = *G->lookupSCC(SourceN);
475 SCC &TargetSCC = *G->lookupSCC(TargetN);
477 // If the two nodes are already part of the same SCC, we're also done as
478 // we've just added more connectivity.
479 if (&SourceSCC == &TargetSCC) {
480 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call);
484 // At this point we leverage the postorder list of SCCs to detect when the
485 // insertion of an edge changes the SCC structure in any way.
487 // First and foremost, we can eliminate the need for any changes when the
488 // edge is toward the beginning of the postorder sequence because all edges
489 // flow in that direction already. Thus adding a new one cannot form a cycle.
490 int SourceIdx = SCCIndices[&SourceSCC];
491 int TargetIdx = SCCIndices[&TargetSCC];
492 if (TargetIdx < SourceIdx) {
493 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call);
497 // Compute the SCCs which (transitively) reach the source.
498 auto ComputeSourceConnectedSet = [&](SmallPtrSetImpl<SCC *> &ConnectedSet) {
500 // Check that the RefSCC is still valid before computing this as the
501 // results will be nonsensical of we've broken its invariants.
504 ConnectedSet.insert(&SourceSCC);
505 auto IsConnected = [&](SCC &C) {
507 for (Edge &E : N.calls()) {
508 assert(E.getNode() && "Must have formed a node within an SCC!");
509 if (ConnectedSet.count(G->lookupSCC(*E.getNode())))
517 make_range(SCCs.begin() + SourceIdx + 1, SCCs.begin() + TargetIdx + 1))
519 ConnectedSet.insert(C);
522 // Use a normal worklist to find which SCCs the target connects to. We still
523 // bound the search based on the range in the postorder list we care about,
524 // but because this is forward connectivity we just "recurse" through the
526 auto ComputeTargetConnectedSet = [&](SmallPtrSetImpl<SCC *> &ConnectedSet) {
528 // Check that the RefSCC is still valid before computing this as the
529 // results will be nonsensical of we've broken its invariants.
532 ConnectedSet.insert(&TargetSCC);
533 SmallVector<SCC *, 4> Worklist;
534 Worklist.push_back(&TargetSCC);
536 SCC &C = *Worklist.pop_back_val();
539 assert(E.getNode() && "Must have formed a node within an SCC!");
542 SCC &EdgeC = *G->lookupSCC(*E.getNode());
543 if (&EdgeC.getOuterRefSCC() != this)
544 // Not in this RefSCC...
546 if (SCCIndices.find(&EdgeC)->second <= SourceIdx)
547 // Not in the postorder sequence between source and target.
550 if (ConnectedSet.insert(&EdgeC).second)
551 Worklist.push_back(&EdgeC);
553 } while (!Worklist.empty());
556 // Use a generic helper to update the postorder sequence of SCCs and return
557 // a range of any SCCs connected into a cycle by inserting this edge. This
558 // routine will also take care of updating the indices into the postorder
560 auto MergeRange = updatePostorderSequenceForEdgeInsertion(
561 SourceSCC, TargetSCC, SCCs, SCCIndices, ComputeSourceConnectedSet,
562 ComputeTargetConnectedSet);
564 // If the merge range is empty, then adding the edge didn't actually form any
565 // new cycles. We're done.
566 if (MergeRange.begin() == MergeRange.end()) {
567 // Now that the SCC structure is finalized, flip the kind to call.
568 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call);
573 // Before merging, check that the RefSCC remains valid after all the
574 // postorder updates.
578 // Otherwise we need to merge all of the SCCs in the cycle into a single
581 // NB: We merge into the target because all of these functions were already
582 // reachable from the target, meaning any SCC-wide properties deduced about it
583 // other than the set of functions within it will not have changed.
584 for (SCC *C : MergeRange) {
585 assert(C != &TargetSCC &&
586 "We merge *into* the target and shouldn't process it here!");
588 TargetSCC.Nodes.append(C->Nodes.begin(), C->Nodes.end());
589 for (Node *N : C->Nodes)
590 G->SCCMap[N] = &TargetSCC;
592 DeletedSCCs.push_back(C);
595 // Erase the merged SCCs from the list and update the indices of the
597 int IndexOffset = MergeRange.end() - MergeRange.begin();
598 auto EraseEnd = SCCs.erase(MergeRange.begin(), MergeRange.end());
599 for (SCC *C : make_range(EraseEnd, SCCs.end()))
600 SCCIndices[C] -= IndexOffset;
602 // Now that the SCC structure is finalized, flip the kind to call.
603 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call);
609 void LazyCallGraph::RefSCC::switchTrivialInternalEdgeToRef(Node &SourceN,
611 assert(SourceN[TargetN].isCall() && "Must start with a call edge!");
614 // In a debug build, verify the RefSCC is valid to start with and when this
617 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
620 assert(G->lookupRefSCC(SourceN) == this &&
621 "Source must be in this RefSCC.");
622 assert(G->lookupRefSCC(TargetN) == this &&
623 "Target must be in this RefSCC.");
624 assert(G->lookupSCC(SourceN) != G->lookupSCC(TargetN) &&
625 "Source and Target must be in separate SCCs for this to be trivial!");
627 // Set the edge kind.
628 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref);
631 iterator_range<LazyCallGraph::RefSCC::iterator>
632 LazyCallGraph::RefSCC::switchInternalEdgeToRef(Node &SourceN, Node &TargetN) {
633 assert(SourceN[TargetN].isCall() && "Must start with a call edge!");
636 // In a debug build, verify the RefSCC is valid to start with and when this
639 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
642 assert(G->lookupRefSCC(SourceN) == this &&
643 "Source must be in this RefSCC.");
644 assert(G->lookupRefSCC(TargetN) == this &&
645 "Target must be in this RefSCC.");
647 SCC &TargetSCC = *G->lookupSCC(TargetN);
648 assert(G->lookupSCC(SourceN) == &TargetSCC && "Source and Target must be in "
649 "the same SCC to require the "
652 // Set the edge kind.
653 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref);
655 // Otherwise we are removing a call edge from a single SCC. This may break
656 // the cycle. In order to compute the new set of SCCs, we need to do a small
657 // DFS over the nodes within the SCC to form any sub-cycles that remain as
658 // distinct SCCs and compute a postorder over the resulting SCCs.
660 // However, we specially handle the target node. The target node is known to
661 // reach all other nodes in the original SCC by definition. This means that
662 // we want the old SCC to be replaced with an SCC contaning that node as it
663 // will be the root of whatever SCC DAG results from the DFS. Assumptions
664 // about an SCC such as the set of functions called will continue to hold,
667 SCC &OldSCC = TargetSCC;
668 SmallVector<std::pair<Node *, call_edge_iterator>, 16> DFSStack;
669 SmallVector<Node *, 16> PendingSCCStack;
670 SmallVector<SCC *, 4> NewSCCs;
672 // Prepare the nodes for a fresh DFS.
673 SmallVector<Node *, 16> Worklist;
674 Worklist.swap(OldSCC.Nodes);
675 for (Node *N : Worklist) {
676 N->DFSNumber = N->LowLink = 0;
680 // Force the target node to be in the old SCC. This also enables us to take
681 // a very significant short-cut in the standard Tarjan walk to re-form SCCs
682 // below: whenever we build an edge that reaches the target node, we know
683 // that the target node eventually connects back to all other nodes in our
684 // walk. As a consequence, we can detect and handle participants in that
685 // cycle without walking all the edges that form this connection, and instead
686 // by relying on the fundamental guarantee coming into this operation (all
687 // nodes are reachable from the target due to previously forming an SCC).
688 TargetN.DFSNumber = TargetN.LowLink = -1;
689 OldSCC.Nodes.push_back(&TargetN);
690 G->SCCMap[&TargetN] = &OldSCC;
692 // Scan down the stack and DFS across the call edges.
693 for (Node *RootN : Worklist) {
694 assert(DFSStack.empty() &&
695 "Cannot begin a new root with a non-empty DFS stack!");
696 assert(PendingSCCStack.empty() &&
697 "Cannot begin a new root with pending nodes for an SCC!");
699 // Skip any nodes we've already reached in the DFS.
700 if (RootN->DFSNumber != 0) {
701 assert(RootN->DFSNumber == -1 &&
702 "Shouldn't have any mid-DFS root nodes!");
706 RootN->DFSNumber = RootN->LowLink = 1;
707 int NextDFSNumber = 2;
709 DFSStack.push_back({RootN, RootN->call_begin()});
712 call_edge_iterator I;
713 std::tie(N, I) = DFSStack.pop_back_val();
714 auto E = N->call_end();
716 Node &ChildN = *I->getNode();
717 if (ChildN.DFSNumber == 0) {
718 // We haven't yet visited this child, so descend, pushing the current
719 // node onto the stack.
720 DFSStack.push_back({N, I});
722 assert(!G->SCCMap.count(&ChildN) &&
723 "Found a node with 0 DFS number but already in an SCC!");
724 ChildN.DFSNumber = ChildN.LowLink = NextDFSNumber++;
731 // Check for the child already being part of some component.
732 if (ChildN.DFSNumber == -1) {
733 if (G->lookupSCC(ChildN) == &OldSCC) {
734 // If the child is part of the old SCC, we know that it can reach
735 // every other node, so we have formed a cycle. Pull the entire DFS
736 // and pending stacks into it. See the comment above about setting
737 // up the old SCC for why we do this.
738 int OldSize = OldSCC.size();
739 OldSCC.Nodes.push_back(N);
740 OldSCC.Nodes.append(PendingSCCStack.begin(), PendingSCCStack.end());
741 PendingSCCStack.clear();
742 while (!DFSStack.empty())
743 OldSCC.Nodes.push_back(DFSStack.pop_back_val().first);
744 for (Node &N : make_range(OldSCC.begin() + OldSize, OldSCC.end())) {
745 N.DFSNumber = N.LowLink = -1;
746 G->SCCMap[&N] = &OldSCC;
752 // If the child has already been added to some child component, it
753 // couldn't impact the low-link of this parent because it isn't
754 // connected, and thus its low-link isn't relevant so skip it.
759 // Track the lowest linked child as the lowest link for this node.
760 assert(ChildN.LowLink > 0 && "Must have a positive low-link number!");
761 if (ChildN.LowLink < N->LowLink)
762 N->LowLink = ChildN.LowLink;
764 // Move to the next edge.
768 // Cleared the DFS early, start another round.
771 // We've finished processing N and its descendents, put it on our pending
772 // SCC stack to eventually get merged into an SCC of nodes.
773 PendingSCCStack.push_back(N);
775 // If this node is linked to some lower entry, continue walking up the
777 if (N->LowLink != N->DFSNumber)
780 // Otherwise, we've completed an SCC. Append it to our post order list of
782 int RootDFSNumber = N->DFSNumber;
783 // Find the range of the node stack by walking down until we pass the
785 auto SCCNodes = make_range(
786 PendingSCCStack.rbegin(),
787 find_if(reverse(PendingSCCStack), [RootDFSNumber](const Node *N) {
788 return N->DFSNumber < RootDFSNumber;
791 // Form a new SCC out of these nodes and then clear them off our pending
793 NewSCCs.push_back(G->createSCC(*this, SCCNodes));
794 for (Node &N : *NewSCCs.back()) {
795 N.DFSNumber = N.LowLink = -1;
796 G->SCCMap[&N] = NewSCCs.back();
798 PendingSCCStack.erase(SCCNodes.end().base(), PendingSCCStack.end());
799 } while (!DFSStack.empty());
802 // Insert the remaining SCCs before the old one. The old SCC can reach all
803 // other SCCs we form because it contains the target node of the removed edge
804 // of the old SCC. This means that we will have edges into all of the new
805 // SCCs, which means the old one must come last for postorder.
806 int OldIdx = SCCIndices[&OldSCC];
807 SCCs.insert(SCCs.begin() + OldIdx, NewSCCs.begin(), NewSCCs.end());
809 // Update the mapping from SCC* to index to use the new SCC*s, and remove the
810 // old SCC from the mapping.
811 for (int Idx = OldIdx, Size = SCCs.size(); Idx < Size; ++Idx)
812 SCCIndices[SCCs[Idx]] = Idx;
814 return make_range(SCCs.begin() + OldIdx,
815 SCCs.begin() + OldIdx + NewSCCs.size());
818 void LazyCallGraph::RefSCC::switchOutgoingEdgeToCall(Node &SourceN,
820 assert(!SourceN[TargetN].isCall() && "Must start with a ref edge!");
822 assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC.");
823 assert(G->lookupRefSCC(TargetN) != this &&
824 "Target must not be in this RefSCC.");
825 assert(G->lookupRefSCC(TargetN)->isDescendantOf(*this) &&
826 "Target must be a descendant of the Source.");
828 // Edges between RefSCCs are the same regardless of call or ref, so we can
829 // just flip the edge here.
830 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call);
833 // Check that the RefSCC is still valid.
838 void LazyCallGraph::RefSCC::switchOutgoingEdgeToRef(Node &SourceN,
840 assert(SourceN[TargetN].isCall() && "Must start with a call edge!");
842 assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC.");
843 assert(G->lookupRefSCC(TargetN) != this &&
844 "Target must not be in this RefSCC.");
845 assert(G->lookupRefSCC(TargetN)->isDescendantOf(*this) &&
846 "Target must be a descendant of the Source.");
848 // Edges between RefSCCs are the same regardless of call or ref, so we can
849 // just flip the edge here.
850 SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref);
853 // Check that the RefSCC is still valid.
858 void LazyCallGraph::RefSCC::insertInternalRefEdge(Node &SourceN,
860 assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC.");
861 assert(G->lookupRefSCC(TargetN) == this && "Target must be in this RefSCC.");
863 SourceN.insertEdgeInternal(TargetN, Edge::Ref);
866 // Check that the RefSCC is still valid.
871 void LazyCallGraph::RefSCC::insertOutgoingEdge(Node &SourceN, Node &TargetN,
873 // First insert it into the caller.
874 SourceN.insertEdgeInternal(TargetN, EK);
876 assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC.");
878 RefSCC &TargetC = *G->lookupRefSCC(TargetN);
879 assert(&TargetC != this && "Target must not be in this RefSCC.");
880 assert(TargetC.isDescendantOf(*this) &&
881 "Target must be a descendant of the Source.");
883 // The only change required is to add this SCC to the parent set of the
885 TargetC.Parents.insert(this);
888 // Check that the RefSCC is still valid.
893 SmallVector<LazyCallGraph::RefSCC *, 1>
894 LazyCallGraph::RefSCC::insertIncomingRefEdge(Node &SourceN, Node &TargetN) {
895 assert(G->lookupRefSCC(TargetN) == this && "Target must be in this RefSCC.");
896 RefSCC &SourceC = *G->lookupRefSCC(SourceN);
897 assert(&SourceC != this && "Source must not be in this RefSCC.");
898 assert(SourceC.isDescendantOf(*this) &&
899 "Source must be a descendant of the Target.");
901 SmallVector<RefSCC *, 1> DeletedRefSCCs;
904 // In a debug build, verify the RefSCC is valid to start with and when this
907 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
910 int SourceIdx = G->RefSCCIndices[&SourceC];
911 int TargetIdx = G->RefSCCIndices[this];
912 assert(SourceIdx < TargetIdx &&
913 "Postorder list doesn't see edge as incoming!");
915 // Compute the RefSCCs which (transitively) reach the source. We do this by
916 // working backwards from the source using the parent set in each RefSCC,
917 // skipping any RefSCCs that don't fall in the postorder range. This has the
918 // advantage of walking the sparser parent edge (in high fan-out graphs) but
919 // more importantly this removes examining all forward edges in all RefSCCs
920 // within the postorder range which aren't in fact connected. Only connected
921 // RefSCCs (and their edges) are visited here.
922 auto ComputeSourceConnectedSet = [&](SmallPtrSetImpl<RefSCC *> &Set) {
923 Set.insert(&SourceC);
924 SmallVector<RefSCC *, 4> Worklist;
925 Worklist.push_back(&SourceC);
927 RefSCC &RC = *Worklist.pop_back_val();
928 for (RefSCC &ParentRC : RC.parents()) {
929 // Skip any RefSCCs outside the range of source to target in the
930 // postorder sequence.
931 int ParentIdx = G->getRefSCCIndex(ParentRC);
932 assert(ParentIdx > SourceIdx && "Parent cannot precede source in postorder!");
933 if (ParentIdx > TargetIdx)
935 if (Set.insert(&ParentRC).second)
936 // First edge connecting to this parent, add it to our worklist.
937 Worklist.push_back(&ParentRC);
939 } while (!Worklist.empty());
942 // Use a normal worklist to find which SCCs the target connects to. We still
943 // bound the search based on the range in the postorder list we care about,
944 // but because this is forward connectivity we just "recurse" through the
946 auto ComputeTargetConnectedSet = [&](SmallPtrSetImpl<RefSCC *> &Set) {
948 SmallVector<RefSCC *, 4> Worklist;
949 Worklist.push_back(this);
951 RefSCC &RC = *Worklist.pop_back_val();
955 assert(E.getNode() && "Must have formed a node!");
956 RefSCC &EdgeRC = *G->lookupRefSCC(*E.getNode());
957 if (G->getRefSCCIndex(EdgeRC) <= SourceIdx)
958 // Not in the postorder sequence between source and target.
961 if (Set.insert(&EdgeRC).second)
962 Worklist.push_back(&EdgeRC);
964 } while (!Worklist.empty());
967 // Use a generic helper to update the postorder sequence of RefSCCs and return
968 // a range of any RefSCCs connected into a cycle by inserting this edge. This
969 // routine will also take care of updating the indices into the postorder
971 iterator_range<SmallVectorImpl<RefSCC *>::iterator> MergeRange =
972 updatePostorderSequenceForEdgeInsertion(
973 SourceC, *this, G->PostOrderRefSCCs, G->RefSCCIndices,
974 ComputeSourceConnectedSet, ComputeTargetConnectedSet);
976 // Build a set so we can do fast tests for whether a RefSCC will end up as
977 // part of the merged RefSCC.
978 SmallPtrSet<RefSCC *, 16> MergeSet(MergeRange.begin(), MergeRange.end());
980 // This RefSCC will always be part of that set, so just insert it here.
981 MergeSet.insert(this);
983 // Now that we have identified all of the SCCs which need to be merged into
984 // a connected set with the inserted edge, merge all of them into this SCC.
985 SmallVector<SCC *, 16> MergedSCCs;
987 for (RefSCC *RC : MergeRange) {
988 assert(RC != this && "We're merging into the target RefSCC, so it "
989 "shouldn't be in the range.");
991 // Merge the parents which aren't part of the merge into the our parents.
992 for (RefSCC *ParentRC : RC->Parents)
993 if (!MergeSet.count(ParentRC))
994 Parents.insert(ParentRC);
997 // Walk the inner SCCs to update their up-pointer and walk all the edges to
998 // update any parent sets.
999 // FIXME: We should try to find a way to avoid this (rather expensive) edge
1000 // walk by updating the parent sets in some other manner.
1001 for (SCC &InnerC : *RC) {
1002 InnerC.OuterRefSCC = this;
1003 SCCIndices[&InnerC] = SCCIndex++;
1004 for (Node &N : InnerC) {
1005 G->SCCMap[&N] = &InnerC;
1007 assert(E.getNode() &&
1008 "Cannot have a null node within a visited SCC!");
1009 RefSCC &ChildRC = *G->lookupRefSCC(*E.getNode());
1010 if (MergeSet.count(&ChildRC))
1012 ChildRC.Parents.erase(RC);
1013 ChildRC.Parents.insert(this);
1018 // Now merge in the SCCs. We can actually move here so try to reuse storage
1019 // the first time through.
1020 if (MergedSCCs.empty())
1021 MergedSCCs = std::move(RC->SCCs);
1023 MergedSCCs.append(RC->SCCs.begin(), RC->SCCs.end());
1025 DeletedRefSCCs.push_back(RC);
1028 // Append our original SCCs to the merged list and move it into place.
1029 for (SCC &InnerC : *this)
1030 SCCIndices[&InnerC] = SCCIndex++;
1031 MergedSCCs.append(SCCs.begin(), SCCs.end());
1032 SCCs = std::move(MergedSCCs);
1034 // Remove the merged away RefSCCs from the post order sequence.
1035 for (RefSCC *RC : MergeRange)
1036 G->RefSCCIndices.erase(RC);
1037 int IndexOffset = MergeRange.end() - MergeRange.begin();
1039 G->PostOrderRefSCCs.erase(MergeRange.begin(), MergeRange.end());
1040 for (RefSCC *RC : make_range(EraseEnd, G->PostOrderRefSCCs.end()))
1041 G->RefSCCIndices[RC] -= IndexOffset;
1043 // At this point we have a merged RefSCC with a post-order SCCs list, just
1044 // connect the nodes to form the new edge.
1045 SourceN.insertEdgeInternal(TargetN, Edge::Ref);
1047 // We return the list of SCCs which were merged so that callers can
1048 // invalidate any data they have associated with those SCCs. Note that these
1049 // SCCs are no longer in an interesting state (they are totally empty) but
1050 // the pointers will remain stable for the life of the graph itself.
1051 return DeletedRefSCCs;
1054 void LazyCallGraph::RefSCC::removeOutgoingEdge(Node &SourceN, Node &TargetN) {
1055 assert(G->lookupRefSCC(SourceN) == this &&
1056 "The source must be a member of this RefSCC.");
1058 RefSCC &TargetRC = *G->lookupRefSCC(TargetN);
1059 assert(&TargetRC != this && "The target must not be a member of this RefSCC");
1061 assert(!is_contained(G->LeafRefSCCs, this) &&
1062 "Cannot have a leaf RefSCC source.");
1065 // In a debug build, verify the RefSCC is valid to start with and when this
1066 // routine finishes.
1068 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
1071 // First remove it from the node.
1072 SourceN.removeEdgeInternal(TargetN.getFunction());
1074 bool HasOtherEdgeToChildRC = false;
1075 bool HasOtherChildRC = false;
1076 for (SCC *InnerC : SCCs) {
1077 for (Node &N : *InnerC) {
1079 assert(E.getNode() && "Cannot have a missing node in a visited SCC!");
1080 RefSCC &OtherChildRC = *G->lookupRefSCC(*E.getNode());
1081 if (&OtherChildRC == &TargetRC) {
1082 HasOtherEdgeToChildRC = true;
1085 if (&OtherChildRC != this)
1086 HasOtherChildRC = true;
1088 if (HasOtherEdgeToChildRC)
1091 if (HasOtherEdgeToChildRC)
1094 // Because the SCCs form a DAG, deleting such an edge cannot change the set
1095 // of SCCs in the graph. However, it may cut an edge of the SCC DAG, making
1096 // the source SCC no longer connected to the target SCC. If so, we need to
1097 // update the target SCC's map of its parents.
1098 if (!HasOtherEdgeToChildRC) {
1099 bool Removed = TargetRC.Parents.erase(this);
1102 "Did not find the source SCC in the target SCC's parent list!");
1104 // It may orphan an SCC if it is the last edge reaching it, but that does
1105 // not violate any invariants of the graph.
1106 if (TargetRC.Parents.empty())
1107 DEBUG(dbgs() << "LCG: Update removing " << SourceN.getFunction().getName()
1108 << " -> " << TargetN.getFunction().getName()
1109 << " edge orphaned the callee's SCC!\n");
1111 // It may make the Source SCC a leaf SCC.
1112 if (!HasOtherChildRC)
1113 G->LeafRefSCCs.push_back(this);
1117 SmallVector<LazyCallGraph::RefSCC *, 1>
1118 LazyCallGraph::RefSCC::removeInternalRefEdge(Node &SourceN, Node &TargetN) {
1119 assert(!SourceN[TargetN].isCall() &&
1120 "Cannot remove a call edge, it must first be made a ref edge");
1123 // In a debug build, verify the RefSCC is valid to start with and when this
1124 // routine finishes.
1126 auto VerifyOnExit = make_scope_exit([&]() { verify(); });
1129 // First remove the actual edge.
1130 SourceN.removeEdgeInternal(TargetN.getFunction());
1132 // We return a list of the resulting *new* RefSCCs in post-order.
1133 SmallVector<RefSCC *, 1> Result;
1135 // Direct recursion doesn't impact the SCC graph at all.
1136 if (&SourceN == &TargetN)
1139 // If this ref edge is within an SCC then there are sufficient other edges to
1140 // form a cycle without this edge so removing it is a no-op.
1141 SCC &SourceC = *G->lookupSCC(SourceN);
1142 SCC &TargetC = *G->lookupSCC(TargetN);
1143 if (&SourceC == &TargetC)
1146 // We build somewhat synthetic new RefSCCs by providing a postorder mapping
1147 // for each inner SCC. We also store these associated with *nodes* rather
1148 // than SCCs because this saves a round-trip through the node->SCC map and in
1149 // the common case, SCCs are small. We will verify that we always give the
1150 // same number to every node in the SCC such that these are equivalent.
1151 const int RootPostOrderNumber = 0;
1152 int PostOrderNumber = RootPostOrderNumber + 1;
1153 SmallDenseMap<Node *, int> PostOrderMapping;
1155 // Every node in the target SCC can already reach every node in this RefSCC
1156 // (by definition). It is the only node we know will stay inside this RefSCC.
1157 // Everything which transitively reaches Target will also remain in the
1158 // RefSCC. We handle this by pre-marking that the nodes in the target SCC map
1159 // back to the root post order number.
1161 // This also enables us to take a very significant short-cut in the standard
1162 // Tarjan walk to re-form RefSCCs below: whenever we build an edge that
1163 // references the target node, we know that the target node eventually
1164 // references all other nodes in our walk. As a consequence, we can detect
1165 // and handle participants in that cycle without walking all the edges that
1166 // form the connections, and instead by relying on the fundamental guarantee
1167 // coming into this operation.
1168 for (Node &N : TargetC)
1169 PostOrderMapping[&N] = RootPostOrderNumber;
1171 // Reset all the other nodes to prepare for a DFS over them, and add them to
1173 SmallVector<Node *, 8> Worklist;
1174 for (SCC *C : SCCs) {
1179 N.DFSNumber = N.LowLink = 0;
1181 Worklist.append(C->Nodes.begin(), C->Nodes.end());
1184 auto MarkNodeForSCCNumber = [&PostOrderMapping](Node &N, int Number) {
1185 N.DFSNumber = N.LowLink = -1;
1186 PostOrderMapping[&N] = Number;
1189 SmallVector<std::pair<Node *, edge_iterator>, 4> DFSStack;
1190 SmallVector<Node *, 4> PendingRefSCCStack;
1192 assert(DFSStack.empty() &&
1193 "Cannot begin a new root with a non-empty DFS stack!");
1194 assert(PendingRefSCCStack.empty() &&
1195 "Cannot begin a new root with pending nodes for an SCC!");
1197 Node *RootN = Worklist.pop_back_val();
1198 // Skip any nodes we've already reached in the DFS.
1199 if (RootN->DFSNumber != 0) {
1200 assert(RootN->DFSNumber == -1 &&
1201 "Shouldn't have any mid-DFS root nodes!");
1205 RootN->DFSNumber = RootN->LowLink = 1;
1206 int NextDFSNumber = 2;
1208 DFSStack.push_back({RootN, RootN->begin()});
1212 std::tie(N, I) = DFSStack.pop_back_val();
1215 assert(N->DFSNumber != 0 && "We should always assign a DFS number "
1216 "before processing a node.");
1219 Node &ChildN = I->getNode(*G);
1220 if (ChildN.DFSNumber == 0) {
1221 // Mark that we should start at this child when next this node is the
1222 // top of the stack. We don't start at the next child to ensure this
1223 // child's lowlink is reflected.
1224 DFSStack.push_back({N, I});
1226 // Continue, resetting to the child node.
1227 ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
1233 if (ChildN.DFSNumber == -1) {
1234 // Check if this edge's target node connects to the deleted edge's
1235 // target node. If so, we know that every node connected will end up
1236 // in this RefSCC, so collapse the entire current stack into the root
1237 // slot in our SCC numbering. See above for the motivation of
1238 // optimizing the target connected nodes in this way.
1239 auto PostOrderI = PostOrderMapping.find(&ChildN);
1240 if (PostOrderI != PostOrderMapping.end() &&
1241 PostOrderI->second == RootPostOrderNumber) {
1242 MarkNodeForSCCNumber(*N, RootPostOrderNumber);
1243 while (!PendingRefSCCStack.empty())
1244 MarkNodeForSCCNumber(*PendingRefSCCStack.pop_back_val(),
1245 RootPostOrderNumber);
1246 while (!DFSStack.empty())
1247 MarkNodeForSCCNumber(*DFSStack.pop_back_val().first,
1248 RootPostOrderNumber);
1249 // Ensure we break all the way out of the enclosing loop.
1254 // If this child isn't currently in this RefSCC, no need to process
1255 // it. However, we do need to remove this RefSCC from its RefSCC's
1257 RefSCC &ChildRC = *G->lookupRefSCC(ChildN);
1258 ChildRC.Parents.erase(this);
1263 // Track the lowest link of the children, if any are still in the stack.
1264 // Any child not on the stack will have a LowLink of -1.
1265 assert(ChildN.LowLink != 0 &&
1266 "Low-link must not be zero with a non-zero DFS number.");
1267 if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink)
1268 N->LowLink = ChildN.LowLink;
1272 // We short-circuited this node.
1275 // We've finished processing N and its descendents, put it on our pending
1276 // stack to eventually get merged into a RefSCC.
1277 PendingRefSCCStack.push_back(N);
1279 // If this node is linked to some lower entry, continue walking up the
1281 if (N->LowLink != N->DFSNumber) {
1282 assert(!DFSStack.empty() &&
1283 "We never found a viable root for a RefSCC to pop off!");
1287 // Otherwise, form a new RefSCC from the top of the pending node stack.
1288 int RootDFSNumber = N->DFSNumber;
1289 // Find the range of the node stack by walking down until we pass the
1291 auto RefSCCNodes = make_range(
1292 PendingRefSCCStack.rbegin(),
1293 find_if(reverse(PendingRefSCCStack), [RootDFSNumber](const Node *N) {
1294 return N->DFSNumber < RootDFSNumber;
1297 // Mark the postorder number for these nodes and clear them off the
1298 // stack. We'll use the postorder number to pull them into RefSCCs at the
1299 // end. FIXME: Fuse with the loop above.
1300 int RefSCCNumber = PostOrderNumber++;
1301 for (Node *N : RefSCCNodes)
1302 MarkNodeForSCCNumber(*N, RefSCCNumber);
1304 PendingRefSCCStack.erase(RefSCCNodes.end().base(),
1305 PendingRefSCCStack.end());
1306 } while (!DFSStack.empty());
1308 assert(DFSStack.empty() && "Didn't flush the entire DFS stack!");
1309 assert(PendingRefSCCStack.empty() && "Didn't flush all pending nodes!");
1310 } while (!Worklist.empty());
1312 // We now have a post-order numbering for RefSCCs and a mapping from each
1313 // node in this RefSCC to its final RefSCC. We create each new RefSCC node
1314 // (re-using this RefSCC node for the root) and build a radix-sort style map
1315 // from postorder number to the RefSCC. We then append SCCs to each of these
1316 // RefSCCs in the order they occured in the original SCCs container.
1317 for (int i = 1; i < PostOrderNumber; ++i)
1318 Result.push_back(G->createRefSCC(*G));
1320 // Insert the resulting postorder sequence into the global graph postorder
1321 // sequence before the current RefSCC in that sequence. The idea being that
1322 // this RefSCC is the target of the reference edge removed, and thus has
1323 // a direct or indirect edge to every other RefSCC formed and so must be at
1324 // the end of any postorder traversal.
1326 // FIXME: It'd be nice to change the APIs so that we returned an iterator
1327 // range over the global postorder sequence and generally use that sequence
1328 // rather than building a separate result vector here.
1329 if (!Result.empty()) {
1330 int Idx = G->getRefSCCIndex(*this);
1331 G->PostOrderRefSCCs.insert(G->PostOrderRefSCCs.begin() + Idx,
1332 Result.begin(), Result.end());
1333 for (int i : seq<int>(Idx, G->PostOrderRefSCCs.size()))
1334 G->RefSCCIndices[G->PostOrderRefSCCs[i]] = i;
1335 assert(G->PostOrderRefSCCs[G->getRefSCCIndex(*this)] == this &&
1336 "Failed to update this RefSCC's index after insertion!");
1339 for (SCC *C : SCCs) {
1340 auto PostOrderI = PostOrderMapping.find(&*C->begin());
1341 assert(PostOrderI != PostOrderMapping.end() &&
1342 "Cannot have missing mappings for nodes!");
1343 int SCCNumber = PostOrderI->second;
1346 assert(PostOrderMapping.find(&N)->second == SCCNumber &&
1347 "Cannot have different numbers for nodes in the same SCC!");
1350 // The root node is handled separately by removing the SCCs.
1353 RefSCC &RC = *Result[SCCNumber - 1];
1354 int SCCIndex = RC.SCCs.size();
1355 RC.SCCs.push_back(C);
1356 RC.SCCIndices[C] = SCCIndex;
1357 C->OuterRefSCC = &RC;
1360 // FIXME: We re-walk the edges in each RefSCC to establish whether it is
1361 // a leaf and connect it to the rest of the graph's parents lists. This is
1362 // really wasteful. We should instead do this during the DFS to avoid yet
1363 // another edge walk.
1364 for (RefSCC *RC : Result)
1365 G->connectRefSCC(*RC);
1367 // Now erase all but the root's SCCs.
1368 SCCs.erase(remove_if(SCCs,
1370 return PostOrderMapping.lookup(&*C->begin()) !=
1371 RootPostOrderNumber;
1375 for (int i = 0, Size = SCCs.size(); i < Size; ++i)
1376 SCCIndices[SCCs[i]] = i;
1379 // Now we need to reconnect the current (root) SCC to the graph. We do this
1380 // manually because we can special case our leaf handling and detect errors.
1384 for (Node &N : *C) {
1386 assert(E.getNode() && "Cannot have a missing node in a visited SCC!");
1387 RefSCC &ChildRC = *G->lookupRefSCC(*E.getNode());
1388 if (&ChildRC == this)
1390 ChildRC.Parents.insert(this);
1397 if (!Result.empty())
1398 assert(!IsLeaf && "This SCC cannot be a leaf as we have split out new "
1399 "SCCs by removing this edge.");
1400 if (none_of(G->LeafRefSCCs, [&](RefSCC *C) { return C == this; }))
1401 assert(!IsLeaf && "This SCC cannot be a leaf as it already had child "
1402 "SCCs before we removed this edge.");
1404 // And connect both this RefSCC and all the new ones to the correct parents.
1405 // The easiest way to do this is just to re-analyze the old parent set.
1406 SmallVector<RefSCC *, 4> OldParents(Parents.begin(), Parents.end());
1408 for (RefSCC *ParentRC : OldParents)
1409 for (SCC &ParentC : *ParentRC)
1410 for (Node &ParentN : ParentC)
1411 for (Edge &E : ParentN) {
1412 assert(E.getNode() && "Cannot have a missing node in a visited SCC!");
1413 RefSCC &RC = *G->lookupRefSCC(*E.getNode());
1414 if (&RC != ParentRC)
1415 RC.Parents.insert(ParentRC);
1418 // If this SCC stopped being a leaf through this edge removal, remove it from
1419 // the leaf SCC list. Note that this DTRT in the case where this was never
1421 // FIXME: As LeafRefSCCs could be very large, we might want to not walk the
1422 // entire list if this RefSCC wasn't a leaf before the edge removal.
1423 if (!Result.empty())
1424 G->LeafRefSCCs.erase(
1425 std::remove(G->LeafRefSCCs.begin(), G->LeafRefSCCs.end(), this),
1426 G->LeafRefSCCs.end());
1429 // Verify all of the new RefSCCs.
1430 for (RefSCC *RC : Result)
1434 // Return the new list of SCCs.
1438 void LazyCallGraph::RefSCC::handleTrivialEdgeInsertion(Node &SourceN,
1440 // The only trivial case that requires any graph updates is when we add new
1441 // ref edge and may connect different RefSCCs along that path. This is only
1442 // because of the parents set. Every other part of the graph remains constant
1443 // after this edge insertion.
1444 assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC.");
1445 RefSCC &TargetRC = *G->lookupRefSCC(TargetN);
1446 if (&TargetRC == this) {
1451 assert(TargetRC.isDescendantOf(*this) &&
1452 "Target must be a descendant of the Source.");
1453 // The only change required is to add this RefSCC to the parent set of the
1454 // target. This is a set and so idempotent if the edge already existed.
1455 TargetRC.Parents.insert(this);
1458 void LazyCallGraph::RefSCC::insertTrivialCallEdge(Node &SourceN,
1461 // Check that the RefSCC is still valid when we finish.
1462 auto ExitVerifier = make_scope_exit([this] { verify(); });
1464 // Check that we aren't breaking some invariants of the SCC graph.
1465 SCC &SourceC = *G->lookupSCC(SourceN);
1466 SCC &TargetC = *G->lookupSCC(TargetN);
1467 if (&SourceC != &TargetC)
1468 assert(SourceC.isAncestorOf(TargetC) &&
1469 "Call edge is not trivial in the SCC graph!");
1471 // First insert it into the source or find the existing edge.
1472 auto InsertResult = SourceN.EdgeIndexMap.insert(
1473 {&TargetN.getFunction(), SourceN.Edges.size()});
1474 if (!InsertResult.second) {
1475 // Already an edge, just update it.
1476 Edge &E = SourceN.Edges[InsertResult.first->second];
1478 return; // Nothing to do!
1479 E.setKind(Edge::Call);
1481 // Create the new edge.
1482 SourceN.Edges.emplace_back(TargetN, Edge::Call);
1485 // Now that we have the edge, handle the graph fallout.
1486 handleTrivialEdgeInsertion(SourceN, TargetN);
1489 void LazyCallGraph::RefSCC::insertTrivialRefEdge(Node &SourceN, Node &TargetN) {
1491 // Check that the RefSCC is still valid when we finish.
1492 auto ExitVerifier = make_scope_exit([this] { verify(); });
1494 // Check that we aren't breaking some invariants of the RefSCC graph.
1495 RefSCC &SourceRC = *G->lookupRefSCC(SourceN);
1496 RefSCC &TargetRC = *G->lookupRefSCC(TargetN);
1497 if (&SourceRC != &TargetRC)
1498 assert(SourceRC.isAncestorOf(TargetRC) &&
1499 "Ref edge is not trivial in the RefSCC graph!");
1501 // First insert it into the source or find the existing edge.
1502 auto InsertResult = SourceN.EdgeIndexMap.insert(
1503 {&TargetN.getFunction(), SourceN.Edges.size()});
1504 if (!InsertResult.second)
1505 // Already an edge, we're done.
1508 // Create the new edge.
1509 SourceN.Edges.emplace_back(TargetN, Edge::Ref);
1511 // Now that we have the edge, handle the graph fallout.
1512 handleTrivialEdgeInsertion(SourceN, TargetN);
1515 void LazyCallGraph::insertEdge(Node &SourceN, Function &Target, Edge::Kind EK) {
1516 assert(SCCMap.empty() && DFSStack.empty() &&
1517 "This method cannot be called after SCCs have been formed!");
1519 return SourceN.insertEdgeInternal(Target, EK);
1522 void LazyCallGraph::removeEdge(Node &SourceN, Function &Target) {
1523 assert(SCCMap.empty() && DFSStack.empty() &&
1524 "This method cannot be called after SCCs have been formed!");
1526 return SourceN.removeEdgeInternal(Target);
1529 void LazyCallGraph::removeDeadFunction(Function &F) {
1530 // FIXME: This is unnecessarily restrictive. We should be able to remove
1531 // functions which recursively call themselves.
1532 assert(F.use_empty() &&
1533 "This routine should only be called on trivially dead functions!");
1535 auto EII = EntryIndexMap.find(&F);
1536 if (EII != EntryIndexMap.end()) {
1537 EntryEdges[EII->second] = Edge();
1538 EntryIndexMap.erase(EII);
1541 // It's safe to just remove un-visited functions from the RefSCC entry list.
1542 // FIXME: This is a linear operation which could become hot and benefit from
1544 auto RENI = find(RefSCCEntryNodes, &F);
1545 if (RENI != RefSCCEntryNodes.end())
1546 RefSCCEntryNodes.erase(RENI);
1548 auto NI = NodeMap.find(&F);
1549 if (NI == NodeMap.end())
1550 // Not in the graph at all!
1553 Node &N = *NI->second;
1556 if (SCCMap.empty() && DFSStack.empty()) {
1557 // No SCC walk has begun, so removing this is fine and there is nothing
1558 // else necessary at this point but clearing out the node.
1563 // Check that we aren't going to break the DFS walk.
1564 assert(all_of(DFSStack,
1565 [&N](const std::pair<Node *, edge_iterator> &Element) {
1566 return Element.first != &N;
1568 "Tried to remove a function currently in the DFS stack!");
1569 assert(find(PendingRefSCCStack, &N) == PendingRefSCCStack.end() &&
1570 "Tried to remove a function currently pending to add to a RefSCC!");
1572 // Cannot remove a function which has yet to be visited in the DFS walk, so
1573 // if we have a node at all then we must have an SCC and RefSCC.
1574 auto CI = SCCMap.find(&N);
1575 assert(CI != SCCMap.end() &&
1576 "Tried to remove a node without an SCC after DFS walk started!");
1577 SCC &C = *CI->second;
1579 RefSCC &RC = C.getOuterRefSCC();
1581 // This node must be the only member of its SCC as it has no callers, and
1582 // that SCC must be the only member of a RefSCC as it has no references.
1583 // Validate these properties first.
1584 assert(C.size() == 1 && "Dead functions must be in a singular SCC");
1585 assert(RC.size() == 1 && "Dead functions must be in a singular RefSCC");
1586 assert(RC.Parents.empty() && "Cannot have parents of a dead RefSCC!");
1588 // Now remove this RefSCC from any parents sets and the leaf list.
1590 if (Node *TargetN = E.getNode())
1591 if (RefSCC *TargetRC = lookupRefSCC(*TargetN))
1592 TargetRC->Parents.erase(&RC);
1593 // FIXME: This is a linear operation which could become hot and benefit from
1595 auto LRI = find(LeafRefSCCs, &RC);
1596 if (LRI != LeafRefSCCs.end())
1597 LeafRefSCCs.erase(LRI);
1599 auto RCIndexI = RefSCCIndices.find(&RC);
1600 int RCIndex = RCIndexI->second;
1601 PostOrderRefSCCs.erase(PostOrderRefSCCs.begin() + RCIndex);
1602 RefSCCIndices.erase(RCIndexI);
1603 for (int i = RCIndex, Size = PostOrderRefSCCs.size(); i < Size; ++i)
1604 RefSCCIndices[PostOrderRefSCCs[i]] = i;
1606 // Finally clear out all the data structures from the node down through the
1612 // Nothing to delete as all the objects are allocated in stable bump pointer
1616 LazyCallGraph::Node &LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
1617 return *new (MappedN = BPA.Allocate()) Node(*this, F);
1620 void LazyCallGraph::updateGraphPtrs() {
1621 // Process all nodes updating the graph pointers.
1623 SmallVector<Node *, 16> Worklist;
1624 for (Edge &E : EntryEdges)
1625 if (Node *EntryN = E.getNode())
1626 Worklist.push_back(EntryN);
1628 while (!Worklist.empty()) {
1629 Node *N = Worklist.pop_back_val();
1631 for (Edge &E : N->Edges)
1632 if (Node *TargetN = E.getNode())
1633 Worklist.push_back(TargetN);
1637 // Process all SCCs updating the graph pointers.
1639 SmallVector<RefSCC *, 16> Worklist(LeafRefSCCs.begin(), LeafRefSCCs.end());
1641 while (!Worklist.empty()) {
1642 RefSCC &C = *Worklist.pop_back_val();
1644 for (RefSCC &ParentC : C.parents())
1645 Worklist.push_back(&ParentC);
1650 /// Build the internal SCCs for a RefSCC from a sequence of nodes.
1652 /// Appends the SCCs to the provided vector and updates the map with their
1653 /// indices. Both the vector and map must be empty when passed into this
1655 void LazyCallGraph::buildSCCs(RefSCC &RC, node_stack_range Nodes) {
1656 assert(RC.SCCs.empty() && "Already built SCCs!");
1657 assert(RC.SCCIndices.empty() && "Already mapped SCC indices!");
1659 for (Node *N : Nodes) {
1660 assert(N->LowLink >= (*Nodes.begin())->LowLink &&
1661 "We cannot have a low link in an SCC lower than its root on the "
1664 // This node will go into the next RefSCC, clear out its DFS and low link
1666 N->DFSNumber = N->LowLink = 0;
1669 // Each RefSCC contains a DAG of the call SCCs. To build these, we do
1670 // a direct walk of the call edges using Tarjan's algorithm. We reuse the
1671 // internal storage as we won't need it for the outer graph's DFS any longer.
1673 SmallVector<std::pair<Node *, call_edge_iterator>, 16> DFSStack;
1674 SmallVector<Node *, 16> PendingSCCStack;
1676 // Scan down the stack and DFS across the call edges.
1677 for (Node *RootN : Nodes) {
1678 assert(DFSStack.empty() &&
1679 "Cannot begin a new root with a non-empty DFS stack!");
1680 assert(PendingSCCStack.empty() &&
1681 "Cannot begin a new root with pending nodes for an SCC!");
1683 // Skip any nodes we've already reached in the DFS.
1684 if (RootN->DFSNumber != 0) {
1685 assert(RootN->DFSNumber == -1 &&
1686 "Shouldn't have any mid-DFS root nodes!");
1690 RootN->DFSNumber = RootN->LowLink = 1;
1691 int NextDFSNumber = 2;
1693 DFSStack.push_back({RootN, RootN->call_begin()});
1696 call_edge_iterator I;
1697 std::tie(N, I) = DFSStack.pop_back_val();
1698 auto E = N->call_end();
1700 Node &ChildN = *I->getNode();
1701 if (ChildN.DFSNumber == 0) {
1702 // We haven't yet visited this child, so descend, pushing the current
1703 // node onto the stack.
1704 DFSStack.push_back({N, I});
1706 assert(!lookupSCC(ChildN) &&
1707 "Found a node with 0 DFS number but already in an SCC!");
1708 ChildN.DFSNumber = ChildN.LowLink = NextDFSNumber++;
1710 I = N->call_begin();
1715 // If the child has already been added to some child component, it
1716 // couldn't impact the low-link of this parent because it isn't
1717 // connected, and thus its low-link isn't relevant so skip it.
1718 if (ChildN.DFSNumber == -1) {
1723 // Track the lowest linked child as the lowest link for this node.
1724 assert(ChildN.LowLink > 0 && "Must have a positive low-link number!");
1725 if (ChildN.LowLink < N->LowLink)
1726 N->LowLink = ChildN.LowLink;
1728 // Move to the next edge.
1732 // We've finished processing N and its descendents, put it on our pending
1733 // SCC stack to eventually get merged into an SCC of nodes.
1734 PendingSCCStack.push_back(N);
1736 // If this node is linked to some lower entry, continue walking up the
1738 if (N->LowLink != N->DFSNumber)
1741 // Otherwise, we've completed an SCC. Append it to our post order list of
1743 int RootDFSNumber = N->DFSNumber;
1744 // Find the range of the node stack by walking down until we pass the
1746 auto SCCNodes = make_range(
1747 PendingSCCStack.rbegin(),
1748 find_if(reverse(PendingSCCStack), [RootDFSNumber](const Node *N) {
1749 return N->DFSNumber < RootDFSNumber;
1751 // Form a new SCC out of these nodes and then clear them off our pending
1753 RC.SCCs.push_back(createSCC(RC, SCCNodes));
1754 for (Node &N : *RC.SCCs.back()) {
1755 N.DFSNumber = N.LowLink = -1;
1756 SCCMap[&N] = RC.SCCs.back();
1758 PendingSCCStack.erase(SCCNodes.end().base(), PendingSCCStack.end());
1759 } while (!DFSStack.empty());
1762 // Wire up the SCC indices.
1763 for (int i = 0, Size = RC.SCCs.size(); i < Size; ++i)
1764 RC.SCCIndices[RC.SCCs[i]] = i;
1767 // FIXME: We should move callers of this to embed the parent linking and leaf
1768 // tracking into their DFS in order to remove a full walk of all edges.
1769 void LazyCallGraph::connectRefSCC(RefSCC &RC) {
1770 // Walk all edges in the RefSCC (this remains linear as we only do this once
1771 // when we build the RefSCC) to connect it to the parent sets of its
1777 assert(E.getNode() &&
1778 "Cannot have a missing node in a visited part of the graph!");
1779 RefSCC &ChildRC = *lookupRefSCC(*E.getNode());
1780 if (&ChildRC == &RC)
1782 ChildRC.Parents.insert(&RC);
1786 // For the SCCs where we find no child SCCs, add them to the leaf list.
1788 LeafRefSCCs.push_back(&RC);
1791 bool LazyCallGraph::buildNextRefSCCInPostOrder() {
1792 if (DFSStack.empty()) {
1795 // If we've handled all candidate entry nodes to the SCC forest, we're
1797 if (RefSCCEntryNodes.empty())
1800 N = &get(*RefSCCEntryNodes.pop_back_val());
1801 } while (N->DFSNumber != 0);
1803 // Found a new root, begin the DFS here.
1804 N->LowLink = N->DFSNumber = 1;
1806 DFSStack.push_back({N, N->begin()});
1812 std::tie(N, I) = DFSStack.pop_back_val();
1814 assert(N->DFSNumber > 0 && "We should always assign a DFS number "
1815 "before placing a node onto the stack.");
1819 Node &ChildN = I->getNode(*this);
1820 if (ChildN.DFSNumber == 0) {
1821 // We haven't yet visited this child, so descend, pushing the current
1822 // node onto the stack.
1823 DFSStack.push_back({N, N->begin()});
1825 assert(!SCCMap.count(&ChildN) &&
1826 "Found a node with 0 DFS number but already in an SCC!");
1827 ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
1834 // If the child has already been added to some child component, it
1835 // couldn't impact the low-link of this parent because it isn't
1836 // connected, and thus its low-link isn't relevant so skip it.
1837 if (ChildN.DFSNumber == -1) {
1842 // Track the lowest linked child as the lowest link for this node.
1843 assert(ChildN.LowLink > 0 && "Must have a positive low-link number!");
1844 if (ChildN.LowLink < N->LowLink)
1845 N->LowLink = ChildN.LowLink;
1847 // Move to the next edge.
1851 // We've finished processing N and its descendents, put it on our pending
1852 // SCC stack to eventually get merged into an SCC of nodes.
1853 PendingRefSCCStack.push_back(N);
1855 // If this node is linked to some lower entry, continue walking up the
1857 if (N->LowLink != N->DFSNumber) {
1858 assert(!DFSStack.empty() &&
1859 "We never found a viable root for an SCC to pop off!");
1863 // Otherwise, form a new RefSCC from the top of the pending node stack.
1864 int RootDFSNumber = N->DFSNumber;
1865 // Find the range of the node stack by walking down until we pass the
1867 auto RefSCCNodes = node_stack_range(
1868 PendingRefSCCStack.rbegin(),
1869 find_if(reverse(PendingRefSCCStack), [RootDFSNumber](const Node *N) {
1870 return N->DFSNumber < RootDFSNumber;
1872 // Form a new RefSCC out of these nodes and then clear them off our pending
1874 RefSCC *NewRC = createRefSCC(*this);
1875 buildSCCs(*NewRC, RefSCCNodes);
1876 connectRefSCC(*NewRC);
1877 PendingRefSCCStack.erase(RefSCCNodes.end().base(),
1878 PendingRefSCCStack.end());
1880 // Push the new node into the postorder list and return true indicating we
1881 // successfully grew the postorder sequence by one.
1883 RefSCCIndices.insert({NewRC, PostOrderRefSCCs.size()}).second;
1885 assert(Inserted && "Cannot already have this RefSCC in the index map!");
1886 PostOrderRefSCCs.push_back(NewRC);
1891 AnalysisKey LazyCallGraphAnalysis::Key;
1893 LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
1895 static void printNode(raw_ostream &OS, LazyCallGraph::Node &N) {
1896 OS << " Edges in function: " << N.getFunction().getName() << "\n";
1897 for (const LazyCallGraph::Edge &E : N)
1898 OS << " " << (E.isCall() ? "call" : "ref ") << " -> "
1899 << E.getFunction().getName() << "\n";
1904 static void printSCC(raw_ostream &OS, LazyCallGraph::SCC &C) {
1905 ptrdiff_t Size = std::distance(C.begin(), C.end());
1906 OS << " SCC with " << Size << " functions:\n";
1908 for (LazyCallGraph::Node &N : C)
1909 OS << " " << N.getFunction().getName() << "\n";
1912 static void printRefSCC(raw_ostream &OS, LazyCallGraph::RefSCC &C) {
1913 ptrdiff_t Size = std::distance(C.begin(), C.end());
1914 OS << " RefSCC with " << Size << " call SCCs:\n";
1916 for (LazyCallGraph::SCC &InnerC : C)
1917 printSCC(OS, InnerC);
1922 PreservedAnalyses LazyCallGraphPrinterPass::run(Module &M,
1923 ModuleAnalysisManager &AM) {
1924 LazyCallGraph &G = AM.getResult<LazyCallGraphAnalysis>(M);
1926 OS << "Printing the call graph for module: " << M.getModuleIdentifier()
1929 for (Function &F : M)
1930 printNode(OS, G.get(F));
1932 for (LazyCallGraph::RefSCC &C : G.postorder_ref_sccs())
1935 return PreservedAnalyses::all();
1938 LazyCallGraphDOTPrinterPass::LazyCallGraphDOTPrinterPass(raw_ostream &OS)
1941 static void printNodeDOT(raw_ostream &OS, LazyCallGraph::Node &N) {
1942 std::string Name = "\"" + DOT::EscapeString(N.getFunction().getName()) + "\"";
1944 for (const LazyCallGraph::Edge &E : N) {
1945 OS << " " << Name << " -> \""
1946 << DOT::EscapeString(E.getFunction().getName()) << "\"";
1947 if (!E.isCall()) // It is a ref edge.
1948 OS << " [style=dashed,label=\"ref\"]";
1955 PreservedAnalyses LazyCallGraphDOTPrinterPass::run(Module &M,
1956 ModuleAnalysisManager &AM) {
1957 LazyCallGraph &G = AM.getResult<LazyCallGraphAnalysis>(M);
1959 OS << "digraph \"" << DOT::EscapeString(M.getModuleIdentifier()) << "\" {\n";
1961 for (Function &F : M)
1962 printNodeDOT(OS, G.get(F));
1966 return PreservedAnalyses::all();