| //===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/LazyCallGraph.h" |
| #include "llvm/ADT/ScopeExit.h" |
| #include "llvm/ADT/Sequence.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/ScopeExit.h" |
| #include "llvm/IR/CallSite.h" |
| #include "llvm/IR/InstVisitor.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/PassManager.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GraphWriter.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "lcg" |
| |
| static void addEdge(SmallVectorImpl<LazyCallGraph::Edge> &Edges, |
| DenseMap<Function *, int> &EdgeIndexMap, Function &F, |
| LazyCallGraph::Edge::Kind EK) { |
| if (!EdgeIndexMap.insert({&F, Edges.size()}).second) |
| return; |
| |
| DEBUG(dbgs() << " Added callable function: " << F.getName() << "\n"); |
| Edges.emplace_back(LazyCallGraph::Edge(F, EK)); |
| } |
| |
| LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F) |
| : G(&G), F(F), DFSNumber(0), LowLink(0) { |
| DEBUG(dbgs() << " Adding functions called by '" << F.getName() |
| << "' to the graph.\n"); |
| |
| SmallVector<Constant *, 16> Worklist; |
| SmallPtrSet<Function *, 4> Callees; |
| SmallPtrSet<Constant *, 16> Visited; |
| |
| // Find all the potential call graph edges in this function. We track both |
| // actual call edges and indirect references to functions. The direct calls |
| // are trivially added, but to accumulate the latter we walk the instructions |
| // and add every operand which is a constant to the worklist to process |
| // afterward. |
| // |
| // Note that we consider *any* function with a definition to be a viable |
| // edge. Even if the function's definition is subject to replacement by |
| // some other module (say, a weak definition) there may still be |
| // optimizations which essentially speculate based on the definition and |
| // a way to check that the specific definition is in fact the one being |
| // used. For example, this could be done by moving the weak definition to |
| // a strong (internal) definition and making the weak definition be an |
| // alias. Then a test of the address of the weak function against the new |
| // strong definition's address would be an effective way to determine the |
| // safety of optimizing a direct call edge. |
| for (BasicBlock &BB : F) |
| for (Instruction &I : BB) { |
| if (auto CS = CallSite(&I)) |
| if (Function *Callee = CS.getCalledFunction()) |
| if (!Callee->isDeclaration()) |
| if (Callees.insert(Callee).second) { |
| Visited.insert(Callee); |
| addEdge(Edges, EdgeIndexMap, *Callee, LazyCallGraph::Edge::Call); |
| } |
| |
| for (Value *Op : I.operand_values()) |
| if (Constant *C = dyn_cast<Constant>(Op)) |
| if (Visited.insert(C).second) |
| Worklist.push_back(C); |
| } |
| |
| // We've collected all the constant (and thus potentially function or |
| // function containing) operands to all of the instructions in the function. |
| // Process them (recursively) collecting every function found. |
| visitReferences(Worklist, Visited, [&](Function &F) { |
| addEdge(Edges, EdgeIndexMap, F, LazyCallGraph::Edge::Ref); |
| }); |
| } |
| |
| void LazyCallGraph::Node::insertEdgeInternal(Function &Target, Edge::Kind EK) { |
| if (Node *N = G->lookup(Target)) |
| return insertEdgeInternal(*N, EK); |
| |
| EdgeIndexMap.insert({&Target, Edges.size()}); |
| Edges.emplace_back(Target, EK); |
| } |
| |
| void LazyCallGraph::Node::insertEdgeInternal(Node &TargetN, Edge::Kind EK) { |
| EdgeIndexMap.insert({&TargetN.getFunction(), Edges.size()}); |
| Edges.emplace_back(TargetN, EK); |
| } |
| |
| void LazyCallGraph::Node::setEdgeKind(Function &TargetF, Edge::Kind EK) { |
| Edges[EdgeIndexMap.find(&TargetF)->second].setKind(EK); |
| } |
| |
| void LazyCallGraph::Node::removeEdgeInternal(Function &Target) { |
| auto IndexMapI = EdgeIndexMap.find(&Target); |
| assert(IndexMapI != EdgeIndexMap.end() && |
| "Target not in the edge set for this caller?"); |
| |
| Edges[IndexMapI->second] = Edge(); |
| EdgeIndexMap.erase(IndexMapI); |
| } |
| |
| void LazyCallGraph::Node::dump() const { |
| dbgs() << *this << '\n'; |
| } |
| |
| LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) { |
| DEBUG(dbgs() << "Building CG for module: " << M.getModuleIdentifier() |
| << "\n"); |
| for (Function &F : M) |
| if (!F.isDeclaration() && !F.hasLocalLinkage()) |
| if (EntryIndexMap.insert({&F, EntryEdges.size()}).second) { |
| DEBUG(dbgs() << " Adding '" << F.getName() |
| << "' to entry set of the graph.\n"); |
| EntryEdges.emplace_back(F, Edge::Ref); |
| } |
| |
| // Now add entry nodes for functions reachable via initializers to globals. |
| SmallVector<Constant *, 16> Worklist; |
| SmallPtrSet<Constant *, 16> Visited; |
| for (GlobalVariable &GV : M.globals()) |
| if (GV.hasInitializer()) |
| if (Visited.insert(GV.getInitializer()).second) |
| Worklist.push_back(GV.getInitializer()); |
| |
| DEBUG(dbgs() << " Adding functions referenced by global initializers to the " |
| "entry set.\n"); |
| visitReferences(Worklist, Visited, [&](Function &F) { |
| addEdge(EntryEdges, EntryIndexMap, F, LazyCallGraph::Edge::Ref); |
| }); |
| |
| for (const Edge &E : EntryEdges) |
| RefSCCEntryNodes.push_back(&E.getFunction()); |
| } |
| |
| LazyCallGraph::LazyCallGraph(LazyCallGraph &&G) |
| : BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)), |
| EntryEdges(std::move(G.EntryEdges)), |
| EntryIndexMap(std::move(G.EntryIndexMap)), SCCBPA(std::move(G.SCCBPA)), |
| SCCMap(std::move(G.SCCMap)), LeafRefSCCs(std::move(G.LeafRefSCCs)), |
| DFSStack(std::move(G.DFSStack)), |
| RefSCCEntryNodes(std::move(G.RefSCCEntryNodes)), |
| NextDFSNumber(G.NextDFSNumber) { |
| updateGraphPtrs(); |
| } |
| |
| LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) { |
| BPA = std::move(G.BPA); |
| NodeMap = std::move(G.NodeMap); |
| EntryEdges = std::move(G.EntryEdges); |
| EntryIndexMap = std::move(G.EntryIndexMap); |
| SCCBPA = std::move(G.SCCBPA); |
| SCCMap = std::move(G.SCCMap); |
| LeafRefSCCs = std::move(G.LeafRefSCCs); |
| DFSStack = std::move(G.DFSStack); |
| RefSCCEntryNodes = std::move(G.RefSCCEntryNodes); |
| NextDFSNumber = G.NextDFSNumber; |
| updateGraphPtrs(); |
| return *this; |
| } |
| |
| void LazyCallGraph::SCC::dump() const { |
| dbgs() << *this << '\n'; |
| } |
| |
| #ifndef NDEBUG |
| void LazyCallGraph::SCC::verify() { |
| assert(OuterRefSCC && "Can't have a null RefSCC!"); |
| assert(!Nodes.empty() && "Can't have an empty SCC!"); |
| |
| for (Node *N : Nodes) { |
| assert(N && "Can't have a null node!"); |
| assert(OuterRefSCC->G->lookupSCC(*N) == this && |
| "Node does not map to this SCC!"); |
| assert(N->DFSNumber == -1 && |
| "Must set DFS numbers to -1 when adding a node to an SCC!"); |
| assert(N->LowLink == -1 && |
| "Must set low link to -1 when adding a node to an SCC!"); |
| for (Edge &E : *N) |
| assert(E.getNode() && "Can't have an edge to a raw function!"); |
| } |
| } |
| #endif |
| |
| bool LazyCallGraph::SCC::isParentOf(const SCC &C) const { |
| if (this == &C) |
| return false; |
| |
| for (Node &N : *this) |
| for (Edge &E : N.calls()) |
| if (Node *CalleeN = E.getNode()) |
| if (OuterRefSCC->G->lookupSCC(*CalleeN) == &C) |
| return true; |
| |
| // No edges found. |
| return false; |
| } |
| |
| bool LazyCallGraph::SCC::isAncestorOf(const SCC &TargetC) const { |
| if (this == &TargetC) |
| return false; |
| |
| LazyCallGraph &G = *OuterRefSCC->G; |
| |
| // Start with this SCC. |
| SmallPtrSet<const SCC *, 16> Visited = {this}; |
| SmallVector<const SCC *, 16> Worklist = {this}; |
| |
| // Walk down the graph until we run out of edges or find a path to TargetC. |
| do { |
| const SCC &C = *Worklist.pop_back_val(); |
| for (Node &N : C) |
| for (Edge &E : N.calls()) { |
| Node *CalleeN = E.getNode(); |
| if (!CalleeN) |
| continue; |
| SCC *CalleeC = G.lookupSCC(*CalleeN); |
| if (!CalleeC) |
| continue; |
| |
| // If the callee's SCC is the TargetC, we're done. |
| if (CalleeC == &TargetC) |
| return true; |
| |
| // If this is the first time we've reached this SCC, put it on the |
| // worklist to recurse through. |
| if (Visited.insert(CalleeC).second) |
| Worklist.push_back(CalleeC); |
| } |
| } while (!Worklist.empty()); |
| |
| // No paths found. |
| return false; |
| } |
| |
| LazyCallGraph::RefSCC::RefSCC(LazyCallGraph &G) : G(&G) {} |
| |
| void LazyCallGraph::RefSCC::dump() const { |
| dbgs() << *this << '\n'; |
| } |
| |
| #ifndef NDEBUG |
| void LazyCallGraph::RefSCC::verify() { |
| assert(G && "Can't have a null graph!"); |
| assert(!SCCs.empty() && "Can't have an empty SCC!"); |
| |
| // Verify basic properties of the SCCs. |
| SmallPtrSet<SCC *, 4> SCCSet; |
| for (SCC *C : SCCs) { |
| assert(C && "Can't have a null SCC!"); |
| C->verify(); |
| assert(&C->getOuterRefSCC() == this && |
| "SCC doesn't think it is inside this RefSCC!"); |
| bool Inserted = SCCSet.insert(C).second; |
| assert(Inserted && "Found a duplicate SCC!"); |
| auto IndexIt = SCCIndices.find(C); |
| assert(IndexIt != SCCIndices.end() && |
| "Found an SCC that doesn't have an index!"); |
| } |
| |
| // Check that our indices map correctly. |
| for (auto &SCCIndexPair : SCCIndices) { |
| SCC *C = SCCIndexPair.first; |
| int i = SCCIndexPair.second; |
| assert(C && "Can't have a null SCC in the indices!"); |
| assert(SCCSet.count(C) && "Found an index for an SCC not in the RefSCC!"); |
| assert(SCCs[i] == C && "Index doesn't point to SCC!"); |
| } |
| |
| // Check that the SCCs are in fact in post-order. |
| for (int i = 0, Size = SCCs.size(); i < Size; ++i) { |
| SCC &SourceSCC = *SCCs[i]; |
| for (Node &N : SourceSCC) |
| for (Edge &E : N) { |
| if (!E.isCall()) |
| continue; |
| SCC &TargetSCC = *G->lookupSCC(*E.getNode()); |
| if (&TargetSCC.getOuterRefSCC() == this) { |
| assert(SCCIndices.find(&TargetSCC)->second <= i && |
| "Edge between SCCs violates post-order relationship."); |
| continue; |
| } |
| assert(TargetSCC.getOuterRefSCC().Parents.count(this) && |
| "Edge to a RefSCC missing us in its parent set."); |
| } |
| } |
| |
| // Check that our parents are actually parents. |
| for (RefSCC *ParentRC : Parents) { |
| assert(ParentRC != this && "Cannot be our own parent!"); |
| auto HasConnectingEdge = [&] { |
| for (SCC &C : *ParentRC) |
| for (Node &N : C) |
| for (Edge &E : N) |
| if (G->lookupRefSCC(*E.getNode()) == this) |
| return true; |
| return false; |
| }; |
| assert(HasConnectingEdge() && "No edge connects the parent to us!"); |
| } |
| } |
| #endif |
| |
| bool LazyCallGraph::RefSCC::isDescendantOf(const RefSCC &C) const { |
| // Walk up the parents of this SCC and verify that we eventually find C. |
| SmallVector<const RefSCC *, 4> AncestorWorklist; |
| AncestorWorklist.push_back(this); |
| do { |
| const RefSCC *AncestorC = AncestorWorklist.pop_back_val(); |
| if (AncestorC->isChildOf(C)) |
| return true; |
| for (const RefSCC *ParentC : AncestorC->Parents) |
| AncestorWorklist.push_back(ParentC); |
| } while (!AncestorWorklist.empty()); |
| |
| return false; |
| } |
| |
| /// Generic helper that updates a postorder sequence of SCCs for a potentially |
| /// cycle-introducing edge insertion. |
| /// |
| /// A postorder sequence of SCCs of a directed graph has one fundamental |
| /// property: all deges in the DAG of SCCs point "up" the sequence. That is, |
| /// all edges in the SCC DAG point to prior SCCs in the sequence. |
| /// |
| /// This routine both updates a postorder sequence and uses that sequence to |
| /// compute the set of SCCs connected into a cycle. It should only be called to |
| /// insert a "downward" edge which will require changing the sequence to |
| /// restore it to a postorder. |
| /// |
| /// When inserting an edge from an earlier SCC to a later SCC in some postorder |
| /// sequence, all of the SCCs which may be impacted are in the closed range of |
| /// those two within the postorder sequence. The algorithm used here to restore |
| /// the state is as follows: |
| /// |
| /// 1) Starting from the source SCC, construct a set of SCCs which reach the |
| /// source SCC consisting of just the source SCC. Then scan toward the |
| /// target SCC in postorder and for each SCC, if it has an edge to an SCC |
| /// in the set, add it to the set. Otherwise, the source SCC is not |
| /// a successor, move it in the postorder sequence to immediately before |
| /// the source SCC, shifting the source SCC and all SCCs in the set one |
| /// position toward the target SCC. Stop scanning after processing the |
| /// target SCC. |
| /// 2) If the source SCC is now past the target SCC in the postorder sequence, |
| /// and thus the new edge will flow toward the start, we are done. |
| /// 3) Otherwise, starting from the target SCC, walk all edges which reach an |
| /// SCC between the source and the target, and add them to the set of |
| /// connected SCCs, then recurse through them. Once a complete set of the |
| /// SCCs the target connects to is known, hoist the remaining SCCs between |
| /// the source and the target to be above the target. Note that there is no |
| /// need to process the source SCC, it is already known to connect. |
| /// 4) At this point, all of the SCCs in the closed range between the source |
| /// SCC and the target SCC in the postorder sequence are connected, |
| /// including the target SCC and the source SCC. Inserting the edge from |
| /// the source SCC to the target SCC will form a cycle out of precisely |
| /// these SCCs. Thus we can merge all of the SCCs in this closed range into |
| /// a single SCC. |
| /// |
| /// This process has various important properties: |
| /// - Only mutates the SCCs when adding the edge actually changes the SCC |
| /// structure. |
| /// - Never mutates SCCs which are unaffected by the change. |
| /// - Updates the postorder sequence to correctly satisfy the postorder |
| /// constraint after the edge is inserted. |
| /// - Only reorders SCCs in the closed postorder sequence from the source to |
| /// the target, so easy to bound how much has changed even in the ordering. |
| /// - Big-O is the number of edges in the closed postorder range of SCCs from |
| /// source to target. |
| /// |
| /// This helper routine, in addition to updating the postorder sequence itself |
| /// will also update a map from SCCs to indices within that sequecne. |
| /// |
| /// The sequence and the map must operate on pointers to the SCC type. |
| /// |
| /// Two callbacks must be provided. The first computes the subset of SCCs in |
| /// the postorder closed range from the source to the target which connect to |
| /// the source SCC via some (transitive) set of edges. The second computes the |
| /// subset of the same range which the target SCC connects to via some |
| /// (transitive) set of edges. Both callbacks should populate the set argument |
| /// provided. |
| template <typename SCCT, typename PostorderSequenceT, typename SCCIndexMapT, |
| typename ComputeSourceConnectedSetCallableT, |
| typename ComputeTargetConnectedSetCallableT> |
| static iterator_range<typename PostorderSequenceT::iterator> |
| updatePostorderSequenceForEdgeInsertion( |
| SCCT &SourceSCC, SCCT &TargetSCC, PostorderSequenceT &SCCs, |
| SCCIndexMapT &SCCIndices, |
| ComputeSourceConnectedSetCallableT ComputeSourceConnectedSet, |
| ComputeTargetConnectedSetCallableT ComputeTargetConnectedSet) { |
| int SourceIdx = SCCIndices[&SourceSCC]; |
| int TargetIdx = SCCIndices[&TargetSCC]; |
| assert(SourceIdx < TargetIdx && "Cannot have equal indices here!"); |
| |
| SmallPtrSet<SCCT *, 4> ConnectedSet; |
| |
| // Compute the SCCs which (transitively) reach the source. |
| ComputeSourceConnectedSet(ConnectedSet); |
| |
| // Partition the SCCs in this part of the port-order sequence so only SCCs |
| // connecting to the source remain between it and the target. This is |
| // a benign partition as it preserves postorder. |
| auto SourceI = std::stable_partition( |
| SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx + 1, |
| [&ConnectedSet](SCCT *C) { return !ConnectedSet.count(C); }); |
| for (int i = SourceIdx, e = TargetIdx + 1; i < e; ++i) |
| SCCIndices.find(SCCs[i])->second = i; |
| |
| // If the target doesn't connect to the source, then we've corrected the |
| // post-order and there are no cycles formed. |
| if (!ConnectedSet.count(&TargetSCC)) { |
| assert(SourceI > (SCCs.begin() + SourceIdx) && |
| "Must have moved the source to fix the post-order."); |
| assert(*std::prev(SourceI) == &TargetSCC && |
| "Last SCC to move should have bene the target."); |
| |
| // Return an empty range at the target SCC indicating there is nothing to |
| // merge. |
| return make_range(std::prev(SourceI), std::prev(SourceI)); |
| } |
| |
| assert(SCCs[TargetIdx] == &TargetSCC && |
| "Should not have moved target if connected!"); |
| SourceIdx = SourceI - SCCs.begin(); |
| assert(SCCs[SourceIdx] == &SourceSCC && |
| "Bad updated index computation for the source SCC!"); |
| |
| |
| // See whether there are any remaining intervening SCCs between the source |
| // and target. If so we need to make sure they all are reachable form the |
| // target. |
| if (SourceIdx + 1 < TargetIdx) { |
| ConnectedSet.clear(); |
| ComputeTargetConnectedSet(ConnectedSet); |
| |
| // Partition SCCs so that only SCCs reached from the target remain between |
| // the source and the target. This preserves postorder. |
| auto TargetI = std::stable_partition( |
| SCCs.begin() + SourceIdx + 1, SCCs.begin() + TargetIdx + 1, |
| [&ConnectedSet](SCCT *C) { return ConnectedSet.count(C); }); |
| for (int i = SourceIdx + 1, e = TargetIdx + 1; i < e; ++i) |
| SCCIndices.find(SCCs[i])->second = i; |
| TargetIdx = std::prev(TargetI) - SCCs.begin(); |
| assert(SCCs[TargetIdx] == &TargetSCC && |
| "Should always end with the target!"); |
| } |
| |
| // At this point, we know that connecting source to target forms a cycle |
| // because target connects back to source, and we know that all of the SCCs |
| // between the source and target in the postorder sequence participate in that |
| // cycle. |
| return make_range(SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx); |
| } |
| |
| SmallVector<LazyCallGraph::SCC *, 1> |
| LazyCallGraph::RefSCC::switchInternalEdgeToCall(Node &SourceN, Node &TargetN) { |
| assert(!SourceN[TargetN].isCall() && "Must start with a ref edge!"); |
| SmallVector<SCC *, 1> DeletedSCCs; |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| SCC &SourceSCC = *G->lookupSCC(SourceN); |
| SCC &TargetSCC = *G->lookupSCC(TargetN); |
| |
| // If the two nodes are already part of the same SCC, we're also done as |
| // we've just added more connectivity. |
| if (&SourceSCC == &TargetSCC) { |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| return DeletedSCCs; |
| } |
| |
| // At this point we leverage the postorder list of SCCs to detect when the |
| // insertion of an edge changes the SCC structure in any way. |
| // |
| // First and foremost, we can eliminate the need for any changes when the |
| // edge is toward the beginning of the postorder sequence because all edges |
| // flow in that direction already. Thus adding a new one cannot form a cycle. |
| int SourceIdx = SCCIndices[&SourceSCC]; |
| int TargetIdx = SCCIndices[&TargetSCC]; |
| if (TargetIdx < SourceIdx) { |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| return DeletedSCCs; |
| } |
| |
| // Compute the SCCs which (transitively) reach the source. |
| auto ComputeSourceConnectedSet = [&](SmallPtrSetImpl<SCC *> &ConnectedSet) { |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid before computing this as the |
| // results will be nonsensical of we've broken its invariants. |
| verify(); |
| #endif |
| ConnectedSet.insert(&SourceSCC); |
| auto IsConnected = [&](SCC &C) { |
| for (Node &N : C) |
| for (Edge &E : N.calls()) { |
| assert(E.getNode() && "Must have formed a node within an SCC!"); |
| if (ConnectedSet.count(G->lookupSCC(*E.getNode()))) |
| return true; |
| } |
| |
| return false; |
| }; |
| |
| for (SCC *C : |
| make_range(SCCs.begin() + SourceIdx + 1, SCCs.begin() + TargetIdx + 1)) |
| if (IsConnected(*C)) |
| ConnectedSet.insert(C); |
| }; |
| |
| // Use a normal worklist to find which SCCs the target connects to. We still |
| // bound the search based on the range in the postorder list we care about, |
| // but because this is forward connectivity we just "recurse" through the |
| // edges. |
| auto ComputeTargetConnectedSet = [&](SmallPtrSetImpl<SCC *> &ConnectedSet) { |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid before computing this as the |
| // results will be nonsensical of we've broken its invariants. |
| verify(); |
| #endif |
| ConnectedSet.insert(&TargetSCC); |
| SmallVector<SCC *, 4> Worklist; |
| Worklist.push_back(&TargetSCC); |
| do { |
| SCC &C = *Worklist.pop_back_val(); |
| for (Node &N : C) |
| for (Edge &E : N) { |
| assert(E.getNode() && "Must have formed a node within an SCC!"); |
| if (!E.isCall()) |
| continue; |
| SCC &EdgeC = *G->lookupSCC(*E.getNode()); |
| if (&EdgeC.getOuterRefSCC() != this) |
| // Not in this RefSCC... |
| continue; |
| if (SCCIndices.find(&EdgeC)->second <= SourceIdx) |
| // Not in the postorder sequence between source and target. |
| continue; |
| |
| if (ConnectedSet.insert(&EdgeC).second) |
| Worklist.push_back(&EdgeC); |
| } |
| } while (!Worklist.empty()); |
| }; |
| |
| // Use a generic helper to update the postorder sequence of SCCs and return |
| // a range of any SCCs connected into a cycle by inserting this edge. This |
| // routine will also take care of updating the indices into the postorder |
| // sequence. |
| auto MergeRange = updatePostorderSequenceForEdgeInsertion( |
| SourceSCC, TargetSCC, SCCs, SCCIndices, ComputeSourceConnectedSet, |
| ComputeTargetConnectedSet); |
| |
| // If the merge range is empty, then adding the edge didn't actually form any |
| // new cycles. We're done. |
| if (MergeRange.begin() == MergeRange.end()) { |
| // Now that the SCC structure is finalized, flip the kind to call. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| return DeletedSCCs; |
| } |
| |
| #ifndef NDEBUG |
| // Before merging, check that the RefSCC remains valid after all the |
| // postorder updates. |
| verify(); |
| #endif |
| |
| // Otherwise we need to merge all of the SCCs in the cycle into a single |
| // result SCC. |
| // |
| // NB: We merge into the target because all of these functions were already |
| // reachable from the target, meaning any SCC-wide properties deduced about it |
| // other than the set of functions within it will not have changed. |
| for (SCC *C : MergeRange) { |
| assert(C != &TargetSCC && |
| "We merge *into* the target and shouldn't process it here!"); |
| SCCIndices.erase(C); |
| TargetSCC.Nodes.append(C->Nodes.begin(), C->Nodes.end()); |
| for (Node *N : C->Nodes) |
| G->SCCMap[N] = &TargetSCC; |
| C->clear(); |
| DeletedSCCs.push_back(C); |
| } |
| |
| // Erase the merged SCCs from the list and update the indices of the |
| // remaining SCCs. |
| int IndexOffset = MergeRange.end() - MergeRange.begin(); |
| auto EraseEnd = SCCs.erase(MergeRange.begin(), MergeRange.end()); |
| for (SCC *C : make_range(EraseEnd, SCCs.end())) |
| SCCIndices[C] -= IndexOffset; |
| |
| // Now that the SCC structure is finalized, flip the kind to call. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| |
| // And we're done! |
| return DeletedSCCs; |
| } |
| |
| void LazyCallGraph::RefSCC::switchTrivialInternalEdgeToRef(Node &SourceN, |
| Node &TargetN) { |
| assert(SourceN[TargetN].isCall() && "Must start with a call edge!"); |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| assert(G->lookupRefSCC(SourceN) == this && |
| "Source must be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN) == this && |
| "Target must be in this RefSCC."); |
| assert(G->lookupSCC(SourceN) != G->lookupSCC(TargetN) && |
| "Source and Target must be in separate SCCs for this to be trivial!"); |
| |
| // Set the edge kind. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref); |
| } |
| |
| iterator_range<LazyCallGraph::RefSCC::iterator> |
| LazyCallGraph::RefSCC::switchInternalEdgeToRef(Node &SourceN, Node &TargetN) { |
| assert(SourceN[TargetN].isCall() && "Must start with a call edge!"); |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| assert(G->lookupRefSCC(SourceN) == this && |
| "Source must be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN) == this && |
| "Target must be in this RefSCC."); |
| |
| SCC &TargetSCC = *G->lookupSCC(TargetN); |
| assert(G->lookupSCC(SourceN) == &TargetSCC && "Source and Target must be in " |
| "the same SCC to require the " |
| "full CG update."); |
| |
| // Set the edge kind. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref); |
| |
| // Otherwise we are removing a call edge from a single SCC. This may break |
| // the cycle. In order to compute the new set of SCCs, we need to do a small |
| // DFS over the nodes within the SCC to form any sub-cycles that remain as |
| // distinct SCCs and compute a postorder over the resulting SCCs. |
| // |
| // However, we specially handle the target node. The target node is known to |
| // reach all other nodes in the original SCC by definition. This means that |
| // we want the old SCC to be replaced with an SCC contaning that node as it |
| // will be the root of whatever SCC DAG results from the DFS. Assumptions |
| // about an SCC such as the set of functions called will continue to hold, |
| // etc. |
| |
| SCC &OldSCC = TargetSCC; |
| SmallVector<std::pair<Node *, call_edge_iterator>, 16> DFSStack; |
| SmallVector<Node *, 16> PendingSCCStack; |
| SmallVector<SCC *, 4> NewSCCs; |
| |
| // Prepare the nodes for a fresh DFS. |
| SmallVector<Node *, 16> Worklist; |
| Worklist.swap(OldSCC.Nodes); |
| for (Node *N : Worklist) { |
| N->DFSNumber = N->LowLink = 0; |
| G->SCCMap.erase(N); |
| } |
| |
| // Force the target node to be in the old SCC. This also enables us to take |
| // a very significant short-cut in the standard Tarjan walk to re-form SCCs |
| // below: whenever we build an edge that reaches the target node, we know |
| // that the target node eventually connects back to all other nodes in our |
| // walk. As a consequence, we can detect and handle participants in that |
| // cycle without walking all the edges that form this connection, and instead |
| // by relying on the fundamental guarantee coming into this operation (all |
| // nodes are reachable from the target due to previously forming an SCC). |
| TargetN.DFSNumber = TargetN.LowLink = -1; |
| OldSCC.Nodes.push_back(&TargetN); |
| G->SCCMap[&TargetN] = &OldSCC; |
| |
| // Scan down the stack and DFS across the call edges. |
| for (Node *RootN : Worklist) { |
| assert(DFSStack.empty() && |
| "Cannot begin a new root with a non-empty DFS stack!"); |
| assert(PendingSCCStack.empty() && |
| "Cannot begin a new root with pending nodes for an SCC!"); |
| |
| // Skip any nodes we've already reached in the DFS. |
| if (RootN->DFSNumber != 0) { |
| assert(RootN->DFSNumber == -1 && |
| "Shouldn't have any mid-DFS root nodes!"); |
| continue; |
| } |
| |
| RootN->DFSNumber = RootN->LowLink = 1; |
| int NextDFSNumber = 2; |
| |
| DFSStack.push_back({RootN, RootN->call_begin()}); |
| do { |
| Node *N; |
| call_edge_iterator I; |
| std::tie(N, I) = DFSStack.pop_back_val(); |
| auto E = N->call_end(); |
| while (I != E) { |
| Node &ChildN = *I->getNode(); |
| if (ChildN.DFSNumber == 0) { |
| // We haven't yet visited this child, so descend, pushing the current |
| // node onto the stack. |
| DFSStack.push_back({N, I}); |
| |
| assert(!G->SCCMap.count(&ChildN) && |
| "Found a node with 0 DFS number but already in an SCC!"); |
| ChildN.DFSNumber = ChildN.LowLink = NextDFSNumber++; |
| N = &ChildN; |
| I = N->call_begin(); |
| E = N->call_end(); |
| continue; |
| } |
| |
| // Check for the child already being part of some component. |
| if (ChildN.DFSNumber == -1) { |
| if (G->lookupSCC(ChildN) == &OldSCC) { |
| // If the child is part of the old SCC, we know that it can reach |
| // every other node, so we have formed a cycle. Pull the entire DFS |
| // and pending stacks into it. See the comment above about setting |
| // up the old SCC for why we do this. |
| int OldSize = OldSCC.size(); |
| OldSCC.Nodes.push_back(N); |
| OldSCC.Nodes.append(PendingSCCStack.begin(), PendingSCCStack.end()); |
| PendingSCCStack.clear(); |
| while (!DFSStack.empty()) |
| OldSCC.Nodes.push_back(DFSStack.pop_back_val().first); |
| for (Node &N : make_range(OldSCC.begin() + OldSize, OldSCC.end())) { |
| N.DFSNumber = N.LowLink = -1; |
| G->SCCMap[&N] = &OldSCC; |
| } |
| N = nullptr; |
| break; |
| } |
| |
| // If the child has already been added to some child component, it |
| // couldn't impact the low-link of this parent because it isn't |
| // connected, and thus its low-link isn't relevant so skip it. |
| ++I; |
| continue; |
| } |
| |
| // Track the lowest linked child as the lowest link for this node. |
| assert(ChildN.LowLink > 0 && "Must have a positive low-link number!"); |
| if (ChildN.LowLink < N->LowLink) |
| N->LowLink = ChildN.LowLink; |
| |
| // Move to the next edge. |
| ++I; |
| } |
| if (!N) |
| // Cleared the DFS early, start another round. |
| break; |
| |
| // We've finished processing N and its descendents, put it on our pending |
| // SCC stack to eventually get merged into an SCC of nodes. |
| PendingSCCStack.push_back(N); |
| |
| // If this node is linked to some lower entry, continue walking up the |
| // stack. |
| if (N->LowLink != N->DFSNumber) |
| continue; |
| |
| // Otherwise, we've completed an SCC. Append it to our post order list of |
| // SCCs. |
| int RootDFSNumber = N->DFSNumber; |
| // Find the range of the node stack by walking down until we pass the |
| // root DFS number. |
| auto SCCNodes = make_range( |
| PendingSCCStack.rbegin(), |
| find_if(reverse(PendingSCCStack), [RootDFSNumber](const Node *N) { |
| return N->DFSNumber < RootDFSNumber; |
| })); |
| |
| // Form a new SCC out of these nodes and then clear them off our pending |
| // stack. |
| NewSCCs.push_back(G->createSCC(*this, SCCNodes)); |
| for (Node &N : *NewSCCs.back()) { |
| N.DFSNumber = N.LowLink = -1; |
| G->SCCMap[&N] = NewSCCs.back(); |
| } |
| PendingSCCStack.erase(SCCNodes.end().base(), PendingSCCStack.end()); |
| } while (!DFSStack.empty()); |
| } |
| |
| // Insert the remaining SCCs before the old one. The old SCC can reach all |
| // other SCCs we form because it contains the target node of the removed edge |
| // of the old SCC. This means that we will have edges into all of the new |
| // SCCs, which means the old one must come last for postorder. |
| int OldIdx = SCCIndices[&OldSCC]; |
| SCCs.insert(SCCs.begin() + OldIdx, NewSCCs.begin(), NewSCCs.end()); |
| |
| // Update the mapping from SCC* to index to use the new SCC*s, and remove the |
| // old SCC from the mapping. |
| for (int Idx = OldIdx, Size = SCCs.size(); Idx < Size; ++Idx) |
| SCCIndices[SCCs[Idx]] = Idx; |
| |
| return make_range(SCCs.begin() + OldIdx, |
| SCCs.begin() + OldIdx + NewSCCs.size()); |
| } |
| |
| void LazyCallGraph::RefSCC::switchOutgoingEdgeToCall(Node &SourceN, |
| Node &TargetN) { |
| assert(!SourceN[TargetN].isCall() && "Must start with a ref edge!"); |
| |
| assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN) != this && |
| "Target must not be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN)->isDescendantOf(*this) && |
| "Target must be a descendant of the Source."); |
| |
| // Edges between RefSCCs are the same regardless of call or ref, so we can |
| // just flip the edge here. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| } |
| |
| void LazyCallGraph::RefSCC::switchOutgoingEdgeToRef(Node &SourceN, |
| Node &TargetN) { |
| assert(SourceN[TargetN].isCall() && "Must start with a call edge!"); |
| |
| assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN) != this && |
| "Target must not be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN)->isDescendantOf(*this) && |
| "Target must be a descendant of the Source."); |
| |
| // Edges between RefSCCs are the same regardless of call or ref, so we can |
| // just flip the edge here. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| } |
| |
| void LazyCallGraph::RefSCC::insertInternalRefEdge(Node &SourceN, |
| Node &TargetN) { |
| assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC."); |
| assert(G->lookupRefSCC(TargetN) == this && "Target must be in this RefSCC."); |
| |
| SourceN.insertEdgeInternal(TargetN, Edge::Ref); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| } |
| |
| void LazyCallGraph::RefSCC::insertOutgoingEdge(Node &SourceN, Node &TargetN, |
| Edge::Kind EK) { |
| // First insert it into the caller. |
| SourceN.insertEdgeInternal(TargetN, EK); |
| |
| assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC."); |
| |
| RefSCC &TargetC = *G->lookupRefSCC(TargetN); |
| assert(&TargetC != this && "Target must not be in this RefSCC."); |
| assert(TargetC.isDescendantOf(*this) && |
| "Target must be a descendant of the Source."); |
| |
| // The only change required is to add this SCC to the parent set of the |
| // callee. |
| TargetC.Parents.insert(this); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| } |
| |
| SmallVector<LazyCallGraph::RefSCC *, 1> |
| LazyCallGraph::RefSCC::insertIncomingRefEdge(Node &SourceN, Node &TargetN) { |
| assert(G->lookupRefSCC(TargetN) == this && "Target must be in this RefSCC."); |
| RefSCC &SourceC = *G->lookupRefSCC(SourceN); |
| assert(&SourceC != this && "Source must not be in this RefSCC."); |
| assert(SourceC.isDescendantOf(*this) && |
| "Source must be a descendant of the Target."); |
| |
| SmallVector<RefSCC *, 1> DeletedRefSCCs; |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| int SourceIdx = G->RefSCCIndices[&SourceC]; |
| int TargetIdx = G->RefSCCIndices[this]; |
| assert(SourceIdx < TargetIdx && |
| "Postorder list doesn't see edge as incoming!"); |
| |
| // Compute the RefSCCs which (transitively) reach the source. We do this by |
| // working backwards from the source using the parent set in each RefSCC, |
| // skipping any RefSCCs that don't fall in the postorder range. This has the |
| // advantage of walking the sparser parent edge (in high fan-out graphs) but |
| // more importantly this removes examining all forward edges in all RefSCCs |
| // within the postorder range which aren't in fact connected. Only connected |
| // RefSCCs (and their edges) are visited here. |
| auto ComputeSourceConnectedSet = [&](SmallPtrSetImpl<RefSCC *> &Set) { |
| Set.insert(&SourceC); |
| SmallVector<RefSCC *, 4> Worklist; |
| Worklist.push_back(&SourceC); |
| do { |
| RefSCC &RC = *Worklist.pop_back_val(); |
| for (RefSCC &ParentRC : RC.parents()) { |
| // Skip any RefSCCs outside the range of source to target in the |
| // postorder sequence. |
| int ParentIdx = G->getRefSCCIndex(ParentRC); |
| assert(ParentIdx > SourceIdx && "Parent cannot precede source in postorder!"); |
| if (ParentIdx > TargetIdx) |
| continue; |
| if (Set.insert(&ParentRC).second) |
| // First edge connecting to this parent, add it to our worklist. |
| Worklist.push_back(&ParentRC); |
| } |
| } while (!Worklist.empty()); |
| }; |
| |
| // Use a normal worklist to find which SCCs the target connects to. We still |
| // bound the search based on the range in the postorder list we care about, |
| // but because this is forward connectivity we just "recurse" through the |
| // edges. |
| auto ComputeTargetConnectedSet = [&](SmallPtrSetImpl<RefSCC *> &Set) { |
| Set.insert(this); |
| SmallVector<RefSCC *, 4> Worklist; |
| Worklist.push_back(this); |
| do { |
| RefSCC &RC = *Worklist.pop_back_val(); |
| for (SCC &C : RC) |
| for (Node &N : C) |
| for (Edge &E : N) { |
| assert(E.getNode() && "Must have formed a node!"); |
| RefSCC &EdgeRC = *G->lookupRefSCC(*E.getNode()); |
| if (G->getRefSCCIndex(EdgeRC) <= SourceIdx) |
| // Not in the postorder sequence between source and target. |
| continue; |
| |
| if (Set.insert(&EdgeRC).second) |
| Worklist.push_back(&EdgeRC); |
| } |
| } while (!Worklist.empty()); |
| }; |
| |
| // Use a generic helper to update the postorder sequence of RefSCCs and return |
| // a range of any RefSCCs connected into a cycle by inserting this edge. This |
| // routine will also take care of updating the indices into the postorder |
| // sequence. |
| iterator_range<SmallVectorImpl<RefSCC *>::iterator> MergeRange = |
| updatePostorderSequenceForEdgeInsertion( |
| SourceC, *this, G->PostOrderRefSCCs, G->RefSCCIndices, |
| ComputeSourceConnectedSet, ComputeTargetConnectedSet); |
| |
| // Build a set so we can do fast tests for whether a RefSCC will end up as |
| // part of the merged RefSCC. |
| SmallPtrSet<RefSCC *, 16> MergeSet(MergeRange.begin(), MergeRange.end()); |
| |
| // This RefSCC will always be part of that set, so just insert it here. |
| MergeSet.insert(this); |
| |
| // Now that we have identified all of the SCCs which need to be merged into |
| // a connected set with the inserted edge, merge all of them into this SCC. |
| SmallVector<SCC *, 16> MergedSCCs; |
| int SCCIndex = 0; |
| for (RefSCC *RC : MergeRange) { |
| assert(RC != this && "We're merging into the target RefSCC, so it " |
| "shouldn't be in the range."); |
| |
| // Merge the parents which aren't part of the merge into the our parents. |
| for (RefSCC *ParentRC : RC->Parents) |
| if (!MergeSet.count(ParentRC)) |
| Parents.insert(ParentRC); |
| RC->Parents.clear(); |
| |
| // Walk the inner SCCs to update their up-pointer and walk all the edges to |
| // update any parent sets. |
| // FIXME: We should try to find a way to avoid this (rather expensive) edge |
| // walk by updating the parent sets in some other manner. |
| for (SCC &InnerC : *RC) { |
| InnerC.OuterRefSCC = this; |
| SCCIndices[&InnerC] = SCCIndex++; |
| for (Node &N : InnerC) { |
| G->SCCMap[&N] = &InnerC; |
| for (Edge &E : N) { |
| assert(E.getNode() && |
| "Cannot have a null node within a visited SCC!"); |
| RefSCC &ChildRC = *G->lookupRefSCC(*E.getNode()); |
| if (MergeSet.count(&ChildRC)) |
| continue; |
| ChildRC.Parents.erase(RC); |
| ChildRC.Parents.insert(this); |
| } |
| } |
| } |
| |
| // Now merge in the SCCs. We can actually move here so try to reuse storage |
| // the first time through. |
| if (MergedSCCs.empty()) |
| MergedSCCs = std::move(RC->SCCs); |
| else |
| MergedSCCs.append(RC->SCCs.begin(), RC->SCCs.end()); |
| RC->SCCs.clear(); |
| DeletedRefSCCs.push_back(RC); |
| } |
| |
| // Append our original SCCs to the merged list and move it into place. |
| for (SCC &InnerC : *this) |
| SCCIndices[&InnerC] = SCCIndex++; |
| MergedSCCs.append(SCCs.begin(), SCCs.end()); |
| SCCs = std::move(MergedSCCs); |
| |
| // Remove the merged away RefSCCs from the post order sequence. |
| for (RefSCC *RC : MergeRange) |
| G->RefSCCIndices.erase(RC); |
| int IndexOffset = MergeRange.end() - MergeRange.begin(); |
| auto EraseEnd = |
| G->PostOrderRefSCCs.erase(MergeRange.begin(), MergeRange.end()); |
| for (RefSCC *RC : make_range(EraseEnd, G->PostOrderRefSCCs.end())) |
| G->RefSCCIndices[RC] -= IndexOffset; |
| |
| // At this point we have a merged RefSCC with a post-order SCCs list, just |
| // connect the nodes to form the new edge. |
| SourceN.insertEdgeInternal(TargetN, Edge::Ref); |
| |
| // We return the list of SCCs which were merged so that callers can |
| // invalidate any data they have associated with those SCCs. Note that these |
| // SCCs are no longer in an interesting state (they are totally empty) but |
| // the pointers will remain stable for the life of the graph itself. |
| return DeletedRefSCCs; |
| } |
| |
| void LazyCallGraph::RefSCC::removeOutgoingEdge(Node &SourceN, Node &TargetN) { |
| assert(G->lookupRefSCC(SourceN) == this && |
| "The source must be a member of this RefSCC."); |
| |
| RefSCC &TargetRC = *G->lookupRefSCC(TargetN); |
| assert(&TargetRC != this && "The target must not be a member of this RefSCC"); |
| |
| assert(!is_contained(G->LeafRefSCCs, this) && |
| "Cannot have a leaf RefSCC source."); |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| // First remove it from the node. |
| SourceN.removeEdgeInternal(TargetN.getFunction()); |
| |
| bool HasOtherEdgeToChildRC = false; |
| bool HasOtherChildRC = false; |
| for (SCC *InnerC : SCCs) { |
| for (Node &N : *InnerC) { |
| for (Edge &E : N) { |
| assert(E.getNode() && "Cannot have a missing node in a visited SCC!"); |
| RefSCC &OtherChildRC = *G->lookupRefSCC(*E.getNode()); |
| if (&OtherChildRC == &TargetRC) { |
| HasOtherEdgeToChildRC = true; |
| break; |
| } |
| if (&OtherChildRC != this) |
| HasOtherChildRC = true; |
| } |
| if (HasOtherEdgeToChildRC) |
| break; |
| } |
| if (HasOtherEdgeToChildRC) |
| break; |
| } |
| // Because the SCCs form a DAG, deleting such an edge cannot change the set |
| // of SCCs in the graph. However, it may cut an edge of the SCC DAG, making |
| // the source SCC no longer connected to the target SCC. If so, we need to |
| // update the target SCC's map of its parents. |
| if (!HasOtherEdgeToChildRC) { |
| bool Removed = TargetRC.Parents.erase(this); |
| (void)Removed; |
| assert(Removed && |
| "Did not find the source SCC in the target SCC's parent list!"); |
| |
| // It may orphan an SCC if it is the last edge reaching it, but that does |
| // not violate any invariants of the graph. |
| if (TargetRC.Parents.empty()) |
| DEBUG(dbgs() << "LCG: Update removing " << SourceN.getFunction().getName() |
| << " -> " << TargetN.getFunction().getName() |
| << " edge orphaned the callee's SCC!\n"); |
| |
| // It may make the Source SCC a leaf SCC. |
| if (!HasOtherChildRC) |
| G->LeafRefSCCs.push_back(this); |
| } |
| } |
| |
| SmallVector<LazyCallGraph::RefSCC *, 1> |
| LazyCallGraph::RefSCC::removeInternalRefEdge(Node &SourceN, Node &TargetN) { |
| assert(!SourceN[TargetN].isCall() && |
| "Cannot remove a call edge, it must first be made a ref edge"); |
| |
| #ifndef NDEBUG |
| // In a debug build, verify the RefSCC is valid to start with and when this |
| // routine finishes. |
| verify(); |
| auto VerifyOnExit = make_scope_exit([&]() { verify(); }); |
| #endif |
| |
| // First remove the actual edge. |
| SourceN.removeEdgeInternal(TargetN.getFunction()); |
| |
| // We return a list of the resulting *new* RefSCCs in post-order. |
| SmallVector<RefSCC *, 1> Result; |
| |
| // Direct recursion doesn't impact the SCC graph at all. |
| if (&SourceN == &TargetN) |
| return Result; |
| |
| // If this ref edge is within an SCC then there are sufficient other edges to |
| // form a cycle without this edge so removing it is a no-op. |
| SCC &SourceC = *G->lookupSCC(SourceN); |
| SCC &TargetC = *G->lookupSCC(TargetN); |
| if (&SourceC == &TargetC) |
| return Result; |
| |
| // We build somewhat synthetic new RefSCCs by providing a postorder mapping |
| // for each inner SCC. We also store these associated with *nodes* rather |
| // than SCCs because this saves a round-trip through the node->SCC map and in |
| // the common case, SCCs are small. We will verify that we always give the |
| // same number to every node in the SCC such that these are equivalent. |
| const int RootPostOrderNumber = 0; |
| int PostOrderNumber = RootPostOrderNumber + 1; |
| SmallDenseMap<Node *, int> PostOrderMapping; |
| |
| // Every node in the target SCC can already reach every node in this RefSCC |
| // (by definition). It is the only node we know will stay inside this RefSCC. |
| // Everything which transitively reaches Target will also remain in the |
| // RefSCC. We handle this by pre-marking that the nodes in the target SCC map |
| // back to the root post order number. |
| // |
| // This also enables us to take a very significant short-cut in the standard |
| // Tarjan walk to re-form RefSCCs below: whenever we build an edge that |
| // references the target node, we know that the target node eventually |
| // references all other nodes in our walk. As a consequence, we can detect |
| // and handle participants in that cycle without walking all the edges that |
| // form the connections, and instead by relying on the fundamental guarantee |
| // coming into this operation. |
| for (Node &N : TargetC) |
| PostOrderMapping[&N] = RootPostOrderNumber; |
| |
| // Reset all the other nodes to prepare for a DFS over them, and add them to |
| // our worklist. |
| SmallVector<Node *, 8> Worklist; |
| for (SCC *C : SCCs) { |
| if (C == &TargetC) |
| continue; |
| |
| for (Node &N : *C) |
| N.DFSNumber = N.LowLink = 0; |
| |
| Worklist.append(C->Nodes.begin(), C->Nodes.end()); |
| } |
| |
| auto MarkNodeForSCCNumber = [&PostOrderMapping](Node &N, int Number) { |
| N.DFSNumber = N.LowLink = -1; |
| PostOrderMapping[&N] = Number; |
| }; |
| |
| SmallVector<std::pair<Node *, edge_iterator>, 4> DFSStack; |
| SmallVector<Node *, 4> PendingRefSCCStack; |
| do { |
| assert(DFSStack.empty() && |
| "Cannot begin a new root with a non-empty DFS stack!"); |
| assert(PendingRefSCCStack.empty() && |
| "Cannot begin a new root with pending nodes for an SCC!"); |
| |
| Node *RootN = Worklist.pop_back_val(); |
| // Skip any nodes we've already reached in the DFS. |
| if (RootN->DFSNumber != 0) { |
| assert(RootN->DFSNumber == -1 && |
| "Shouldn't have any mid-DFS root nodes!"); |
| continue; |
| } |
| |
| RootN->DFSNumber = RootN->LowLink = 1; |
| int NextDFSNumber = 2; |
| |
| DFSStack.push_back({RootN, RootN->begin()}); |
| do { |
| Node *N; |
| edge_iterator I; |
| std::tie(N, I) = DFSStack.pop_back_val(); |
| auto E = N->end(); |
| |
| assert(N->DFSNumber != 0 && "We should always assign a DFS number " |
| "before processing a node."); |
| |
| while (I != E) { |
| Node &ChildN = I->getNode(*G); |
| if (ChildN.DFSNumber == 0) { |
| // Mark that we should start at this child when next this node is the |
| // top of the stack. We don't start at the next child to ensure this |
| // child's lowlink is reflected. |
| DFSStack.push_back({N, I}); |
| |
| // Continue, resetting to the child node. |
| ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++; |
| N = &ChildN; |
| I = ChildN.begin(); |
| E = ChildN.end(); |
| continue; |
| } |
| if (ChildN.DFSNumber == -1) { |
| // Check if this edge's target node connects to the deleted edge's |
| // target node. If so, we know that every node connected will end up |
| // in this RefSCC, so collapse the entire current stack into the root |
| // slot in our SCC numbering. See above for the motivation of |
| // optimizing the target connected nodes in this way. |
| auto PostOrderI = PostOrderMapping.find(&ChildN); |
| if (PostOrderI != PostOrderMapping.end() && |
| PostOrderI->second == RootPostOrderNumber) { |
| MarkNodeForSCCNumber(*N, RootPostOrderNumber); |
| while (!PendingRefSCCStack.empty()) |
| MarkNodeForSCCNumber(*PendingRefSCCStack.pop_back_val(), |
| RootPostOrderNumber); |
| while (!DFSStack.empty()) |
| MarkNodeForSCCNumber(*DFSStack.pop_back_val().first, |
| RootPostOrderNumber); |
| // Ensure we break all the way out of the enclosing loop. |
| N = nullptr; |
| break; |
| } |
| |
| // If this child isn't currently in this RefSCC, no need to process |
| // it. However, we do need to remove this RefSCC from its RefSCC's |
| // parent set. |
| RefSCC &ChildRC = *G->lookupRefSCC(ChildN); |
| ChildRC.Parents.erase(this); |
| ++I; |
| continue; |
| } |
| |
| // Track the lowest link of the children, if any are still in the stack. |
| // Any child not on the stack will have a LowLink of -1. |
| assert(ChildN.LowLink != 0 && |
| "Low-link must not be zero with a non-zero DFS number."); |
| if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink) |
| N->LowLink = ChildN.LowLink; |
| ++I; |
| } |
| if (!N) |
| // We short-circuited this node. |
| break; |
| |
| // We've finished processing N and its descendents, put it on our pending |
| // stack to eventually get merged into a RefSCC. |
| PendingRefSCCStack.push_back(N); |
| |
| // If this node is linked to some lower entry, continue walking up the |
| // stack. |
| if (N->LowLink != N->DFSNumber) { |
| assert(!DFSStack.empty() && |
| "We never found a viable root for a RefSCC to pop off!"); |
| continue; |
| } |
| |
| // Otherwise, form a new RefSCC from the top of the pending node stack. |
| int RootDFSNumber = N->DFSNumber; |
| // Find the range of the node stack by walking down until we pass the |
| // root DFS number. |
| auto RefSCCNodes = make_range( |
| PendingRefSCCStack.rbegin(), |
| find_if(reverse(PendingRefSCCStack), [RootDFSNumber](const Node *N) { |
| return N->DFSNumber < RootDFSNumber; |
| })); |
| |
| // Mark the postorder number for these nodes and clear them off the |
| // stack. We'll use the postorder number to pull them into RefSCCs at the |
| // end. FIXME: Fuse with the loop above. |
| int RefSCCNumber = PostOrderNumber++; |
| for (Node *N : RefSCCNodes) |
| MarkNodeForSCCNumber(*N, RefSCCNumber); |
| |
| PendingRefSCCStack.erase(RefSCCNodes.end().base(), |
| PendingRefSCCStack.end()); |
| } while (!DFSStack.empty()); |
| |
| assert(DFSStack.empty() && "Didn't flush the entire DFS stack!"); |
| assert(PendingRefSCCStack.empty() && "Didn't flush all pending nodes!"); |
| } while (!Worklist.empty()); |
| |
| // We now have a post-order numbering for RefSCCs and a mapping from each |
| // node in this RefSCC to its final RefSCC. We create each new RefSCC node |
| // (re-using this RefSCC node for the root) and build a radix-sort style map |
| // from postorder number to the RefSCC. We then append SCCs to each of these |
| // RefSCCs in the order they occured in the original SCCs container. |
| for (int i = 1; i < PostOrderNumber; ++i) |
| Result.push_back(G->createRefSCC(*G)); |
| |
| // Insert the resulting postorder sequence into the global graph postorder |
| // sequence before the current RefSCC in that sequence. The idea being that |
| // this RefSCC is the target of the reference edge removed, and thus has |
| // a direct or indirect edge to every other RefSCC formed and so must be at |
| // the end of any postorder traversal. |
| // |
| // FIXME: It'd be nice to change the APIs so that we returned an iterator |
| // range over the global postorder sequence and generally use that sequence |
| // rather than building a separate result vector here. |
| if (!Result.empty()) { |
| int Idx = G->getRefSCCIndex(*this); |
| G->PostOrderRefSCCs.insert(G->PostOrderRefSCCs.begin() + Idx, |
| Result.begin(), Result.end()); |
| for (int i : seq<int>(Idx, G->PostOrderRefSCCs.size())) |
| G->RefSCCIndices[G->PostOrderRefSCCs[i]] = i; |
| assert(G->PostOrderRefSCCs[G->getRefSCCIndex(*this)] == this && |
| "Failed to update this RefSCC's index after insertion!"); |
| } |
| |
| for (SCC *C : SCCs) { |
| auto PostOrderI = PostOrderMapping.find(&*C->begin()); |
| assert(PostOrderI != PostOrderMapping.end() && |
| "Cannot have missing mappings for nodes!"); |
| int SCCNumber = PostOrderI->second; |
| #ifndef NDEBUG |
| for (Node &N : *C) |
| assert(PostOrderMapping.find(&N)->second == SCCNumber && |
| "Cannot have different numbers for nodes in the same SCC!"); |
| #endif |
| if (SCCNumber == 0) |
| // The root node is handled separately by removing the SCCs. |
| continue; |
| |
| RefSCC &RC = *Result[SCCNumber - 1]; |
| int SCCIndex = RC.SCCs.size(); |
| RC.SCCs.push_back(C); |
| RC.SCCIndices[C] = SCCIndex; |
| C->OuterRefSCC = &RC; |
| } |
| |
| // FIXME: We re-walk the edges in each RefSCC to establish whether it is |
| // a leaf and connect it to the rest of the graph's parents lists. This is |
| // really wasteful. We should instead do this during the DFS to avoid yet |
| // another edge walk. |
| for (RefSCC *RC : Result) |
| G->connectRefSCC(*RC); |
| |
| // Now erase all but the root's SCCs. |
| SCCs.erase(remove_if(SCCs, |
| [&](SCC *C) { |
| return PostOrderMapping.lookup(&*C->begin()) != |
| RootPostOrderNumber; |
| }), |
| SCCs.end()); |
| SCCIndices.clear(); |
| for (int i = 0, Size = SCCs.size(); i < Size; ++i) |
| SCCIndices[SCCs[i]] = i; |
| |
| #ifndef NDEBUG |
| // Now we need to reconnect the current (root) SCC to the graph. We do this |
| // manually because we can special case our leaf handling and detect errors. |
| bool IsLeaf = true; |
| #endif |
| for (SCC *C : SCCs) |
| for (Node &N : *C) { |
| for (Edge &E : N) { |
| assert(E.getNode() && "Cannot have a missing node in a visited SCC!"); |
| RefSCC &ChildRC = *G->lookupRefSCC(*E.getNode()); |
| if (&ChildRC == this) |
| continue; |
| ChildRC.Parents.insert(this); |
| #ifndef NDEBUG |
| IsLeaf = false; |
| #endif |
| } |
| } |
| #ifndef NDEBUG |
| if (!Result.empty()) |
| assert(!IsLeaf && "This SCC cannot be a leaf as we have split out new " |
| "SCCs by removing this edge."); |
| if (none_of(G->LeafRefSCCs, [&](RefSCC *C) { return C == this; })) |
| assert(!IsLeaf && "This SCC cannot be a leaf as it already had child " |
| "SCCs before we removed this edge."); |
| #endif |
| // And connect both this RefSCC and all the new ones to the correct parents. |
| // The easiest way to do this is just to re-analyze the old parent set. |
| SmallVector<RefSCC *, 4> OldParents(Parents.begin(), Parents.end()); |
| Parents.clear(); |
| for (RefSCC *ParentRC : OldParents) |
| for (SCC &ParentC : *ParentRC) |
| for (Node &ParentN : ParentC) |
| for (Edge &E : ParentN) { |
| assert(E.getNode() && "Cannot have a missing node in a visited SCC!"); |
| RefSCC &RC = *G->lookupRefSCC(*E.getNode()); |
| if (&RC != ParentRC) |
| RC.Parents.insert(ParentRC); |
| } |
| |
| // If this SCC stopped being a leaf through this edge removal, remove it from |
| // the leaf SCC list. Note that this DTRT in the case where this was never |
| // a leaf. |
| // FIXME: As LeafRefSCCs could be very large, we might want to not walk the |
| // entire list if this RefSCC wasn't a leaf before the edge removal. |
| if (!Result.empty()) |
| G->LeafRefSCCs.erase( |
| std::remove(G->LeafRefSCCs.begin(), G->LeafRefSCCs.end(), this), |
| G->LeafRefSCCs.end()); |
| |
| #ifndef NDEBUG |
| // Verify all of the new RefSCCs. |
| for (RefSCC *RC : Result) |
| RC->verify(); |
| #endif |
| |
| // Return the new list of SCCs. |
| return Result; |
| } |
| |
| void LazyCallGraph::RefSCC::handleTrivialEdgeInsertion(Node &SourceN, |
| Node &TargetN) { |
| // The only trivial case that requires any graph updates is when we add new |
| // ref edge and may connect different RefSCCs along that path. This is only |
| // because of the parents set. Every other part of the graph remains constant |
| // after this edge insertion. |
| assert(G->lookupRefSCC(SourceN) == this && "Source must be in this RefSCC."); |
| RefSCC &TargetRC = *G->lookupRefSCC(TargetN); |
| if (&TargetRC == this) { |
| |
| return; |
| } |
| |
| assert(TargetRC.isDescendantOf(*this) && |
| "Target must be a descendant of the Source."); |
| // The only change required is to add this RefSCC to the parent set of the |
| // target. This is a set and so idempotent if the edge already existed. |
| TargetRC.Parents.insert(this); |
| } |
| |
| void LazyCallGraph::RefSCC::insertTrivialCallEdge(Node &SourceN, |
| Node &TargetN) { |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid when we finish. |
| auto ExitVerifier = make_scope_exit([this] { verify(); }); |
| |
| // Check that we aren't breaking some invariants of the SCC graph. |
| SCC &SourceC = *G->lookupSCC(SourceN); |
| SCC &TargetC = *G->lookupSCC(TargetN); |
| if (&SourceC != &TargetC) |
| assert(SourceC.isAncestorOf(TargetC) && |
| "Call edge is not trivial in the SCC graph!"); |
| #endif |
| // First insert it into the source or find the existing edge. |
| auto InsertResult = SourceN.EdgeIndexMap.insert( |
| {&TargetN.getFunction(), SourceN.Edges.size()}); |
| if (!InsertResult.second) { |
| // Already an edge, just update it. |
| Edge &E = SourceN.Edges[InsertResult.first->second]; |
| if (E.isCall()) |
| return; // Nothing to do! |
| E.setKind(Edge::Call); |
| } else { |
| // Create the new edge. |
| SourceN.Edges.emplace_back(TargetN, Edge::Call); |
| } |
| |
| // Now that we have the edge, handle the graph fallout. |
| handleTrivialEdgeInsertion(SourceN, TargetN); |
| } |
| |
| void LazyCallGraph::RefSCC::insertTrivialRefEdge(Node &SourceN, Node &TargetN) { |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid when we finish. |
| auto ExitVerifier = make_scope_exit([this] { verify(); }); |
| |
| // Check that we aren't breaking some invariants of the RefSCC graph. |
| RefSCC &SourceRC = *G->lookupRefSCC(SourceN); |
| RefSCC &TargetRC = *G->lookupRefSCC(TargetN); |
| if (&SourceRC != &TargetRC) |
| assert(SourceRC.isAncestorOf(TargetRC) && |
| "Ref edge is not trivial in the RefSCC graph!"); |
| #endif |
| // First insert it into the source or find the existing edge. |
| auto InsertResult = SourceN.EdgeIndexMap.insert( |
| {&TargetN.getFunction(), SourceN.Edges.size()}); |
| if (!InsertResult.second) |
| // Already an edge, we're done. |
| return; |
| |
| // Create the new edge. |
| SourceN.Edges.emplace_back(TargetN, Edge::Ref); |
| |
| // Now that we have the edge, handle the graph fallout. |
| handleTrivialEdgeInsertion(SourceN, TargetN); |
| } |
| |
| void LazyCallGraph::insertEdge(Node &SourceN, Function &Target, Edge::Kind EK) { |
| assert(SCCMap.empty() && DFSStack.empty() && |
| "This method cannot be called after SCCs have been formed!"); |
| |
| return SourceN.insertEdgeInternal(Target, EK); |
| } |
| |
| void LazyCallGraph::removeEdge(Node &SourceN, Function &Target) { |
| assert(SCCMap.empty() && DFSStack.empty() && |
| "This method cannot be called after SCCs have been formed!"); |
| |
| return SourceN.removeEdgeInternal(Target); |
| } |
| |
| void LazyCallGraph::removeDeadFunction(Function &F) { |
| // FIXME: This is unnecessarily restrictive. We should be able to remove |
| // functions which recursively call themselves. |
| assert(F.use_empty() && |
| "This routine should only be called on trivially dead functions!"); |
| |
| auto EII = EntryIndexMap.find(&F); |
| if (EII != EntryIndexMap.end()) { |
| EntryEdges[EII->second] = Edge(); |
| EntryIndexMap.erase(EII); |
| } |
| |
| // It's safe to just remove un-visited functions from the RefSCC entry list. |
| // FIXME: This is a linear operation which could become hot and benefit from |
| // an index map. |
| auto RENI = find(RefSCCEntryNodes, &F); |
| if (RENI != RefSCCEntryNodes.end()) |
| RefSCCEntryNodes.erase(RENI); |
| |
| auto NI = NodeMap.find(&F); |
| if (NI == NodeMap.end()) |
| // Not in the graph at all! |
| return; |
| |
| Node &N = *NI->second; |
| NodeMap.erase(NI); |
| |
| if (SCCMap.empty() && DFSStack.empty()) { |
| // No SCC walk has begun, so removing this is fine and there is nothing |
| // else necessary at this point but clearing out the node. |
| N.clear(); |
| return; |
| } |
| |
| // Check that we aren't going to break the DFS walk. |
| assert(all_of(DFSStack, |
| [&N](const std::pair<Node *, edge_iterator> &Element) { |
| return Element.first != &N; |
| }) && |
| "Tried to remove a function currently in the DFS stack!"); |
| assert(find(PendingRefSCCStack, &N) == PendingRefSCCStack.end() && |
| "Tried to remove a function currently pending to add to a RefSCC!"); |
| |
| // Cannot remove a function which has yet to be visited in the DFS walk, so |
| // if we have a node at all then we must have an SCC and RefSCC. |
| auto CI = SCCMap.find(&N); |
| assert(CI != SCCMap.end() && |
| "Tried to remove a node without an SCC after DFS walk started!"); |
| SCC &C = *CI->second; |
| SCCMap.erase(CI); |
| RefSCC &RC = C.getOuterRefSCC(); |
| |
| // This node must be the only member of its SCC as it has no callers, and |
| // that SCC must be the only member of a RefSCC as it has no references. |
| // Validate these properties first. |
| assert(C.size() == 1 && "Dead functions must be in a singular SCC"); |
| assert(RC.size() == 1 && "Dead functions must be in a singular RefSCC"); |
| assert(RC.Parents.empty() && "Cannot have parents of a dead RefSCC!"); |
| |
| // Now remove this RefSCC from any parents sets and the leaf list. |
| for (Edge &E : N) |
| if (Node *TargetN = E.getNode()) |
| if (RefSCC *TargetRC = lookupRefSCC(*TargetN)) |
| TargetRC->Parents.erase(&RC); |
| // FIXME: This is a linear operation which could become hot and benefit from |
| // an index map. |
| auto LRI = find(LeafRefSCCs, &RC); |
| if (LRI != LeafRefSCCs.end()) |
| LeafRefSCCs.erase(LRI); |
| |
| auto RCIndexI = RefSCCIndices.find(&RC); |
| int RCIndex = RCIndexI->second; |
| PostOrderRefSCCs.erase(PostOrderRefSCCs.begin() + RCIndex); |
| RefSCCIndices.erase(RCIndexI); |
| for (int i = RCIndex, Size = PostOrderRefSCCs.size(); i < Size; ++i) |
| RefSCCIndices[PostOrderRefSCCs[i]] = i; |
| |
| // Finally clear out all the data structures from the node down through the |
| // components. |
| N.clear(); |
| C.clear(); |
| RC.clear(); |
| |
| // Nothing to delete as all the objects are allocated in stable bump pointer |
| // allocators. |
| } |
| |
| LazyCallGraph::Node &LazyCallGraph::insertInto(Function &F, Node *&MappedN) { |
| return *new (MappedN = BPA.Allocate()) Node(*this, F); |
| } |
| |
| void LazyCallGraph::updateGraphPtrs() { |
| // Process all nodes updating the graph pointers. |
| { |
| SmallVector<Node *, 16> Worklist; |
| for (Edge &E : EntryEdges) |
| if (Node *EntryN = E.getNode()) |
| Worklist.push_back(EntryN); |
| |
| while (!Worklist.empty()) { |
| Node *N = Worklist.pop_back_val(); |
| N->G = this; |
| for (Edge &E : N->Edges) |
| if (Node *TargetN = E.getNode()) |
| Worklist.push_back(TargetN); |
| } |
| } |
| |
| // Process all SCCs updating the graph pointers. |
| { |
| SmallVector<RefSCC *, 16> Worklist(LeafRefSCCs.begin(), LeafRefSCCs.end()); |
| |
| while (!Worklist.empty()) { |
| RefSCC &C = *Worklist.pop_back_val(); |
| C.G = this; |
| for (RefSCC &ParentC : C.parents()) |
| Worklist.push_back(&ParentC); |
| } |
| } |
| } |
| |
| /// Build the internal SCCs for a RefSCC from a sequence of nodes. |
| /// |
| /// Appends the SCCs to the provided vector and updates the map with their |
| /// indices. Both the vector and map must be empty when passed into this |
| /// routine. |
| void LazyCallGraph::buildSCCs(RefSCC &RC, node_stack_range Nodes) { |
| assert(RC.SCCs.empty() && "Already built SCCs!"); |
| assert(RC.SCCIndices.empty() && "Already mapped SCC indices!"); |
| |
| for (Node *N : Nodes) { |
| assert(N->LowLink >= (*Nodes.begin())->LowLink && |
| "We cannot have a low link in an SCC lower than its root on the " |
| "stack!"); |
| |
| // This node will go into the next RefSCC, clear out its DFS and low link |
| // as we scan. |
| N->DFSNumber = N->LowLink = 0; |
| } |
| |
| // Each RefSCC contains a DAG of the call SCCs. To build these, we do |
| // a direct walk of the call edges using Tarjan's algorithm. We reuse the |
| // internal storage as we won't need it for the outer graph's DFS any longer. |
| |
| SmallVector<std::pair<Node *, call_edge_iterator>, 16> DFSStack; |
| SmallVector<Node *, 16> PendingSCCStack; |
| |
| // Scan down the stack and DFS across the call edges. |
| for (Node *RootN : Nodes) { |
| assert(DFSStack.empty() && |
| "Cannot begin a new root with a non-empty DFS stack!"); |
| assert(PendingSCCStack.empty() && |
| "Cannot begin a new root with pending nodes for an SCC!"); |
| |
| // Skip any nodes we've already reached in the DFS. |
| if (RootN->DFSNumber != 0) { |
| assert(RootN->DFSNumber == -1 && |
| "Shouldn't have any mid-DFS root nodes!"); |
| continue; |
| } |
| |
| RootN->DFSNumber = RootN->LowLink = 1; |
| int NextDFSNumber = 2; |
| |
| DFSStack.push_back({RootN, RootN->call_begin()}); |
| do { |
| Node *N; |
| call_edge_iterator I; |
| std::tie(N, I) = DFSStack.pop_back_val(); |
| auto E = N->call_end(); |
| while (I != E) { |
| Node &ChildN = *I->getNode(); |
| if (ChildN.DFSNumber == 0) { |
| // We haven't yet visited this child, so descend, pushing the current |
| // node onto the stack. |
| DFSStack.push_back({N, I}); |
| |
| assert(!lookupSCC(ChildN) && |
| "Found a node with 0 DFS number but already in an SCC!"); |
| ChildN.DFSNumber = ChildN.LowLink = NextDFSNumber++; |
| N = &ChildN; |
| I = N->call_begin(); |
| E = N->call_end(); |
| continue; |
| } |
| |
| // If the child has already been added to some child component, it |
| // couldn't impact the low-link of this parent because it isn't |
| // connected, and thus its low-link isn't relevant so skip it. |
| if (ChildN.DFSNumber == -1) { |
| ++I; |
| continue; |
| } |
| |
| // Track the lowest linked child as the lowest link for this node. |
| assert(ChildN.LowLink > 0 && "Must have a positive low-link number!"); |
| if (ChildN.LowLink < N->LowLink) |
| N->LowLink = ChildN.LowLink; |
| |
| // Move to the next edge. |
| ++I; |
| } |
| |
| // We've finished processing N and its descendents, put it on our pending |
| // SCC stack to eventually get merged into an SCC of nodes. |
| PendingSCCStack.push_back(N); |
| |
| // If this node is linked to some lower entry, continue walking up the |
| // stack. |
| if (N->LowLink != N->DFSNumber) |
| continue; |
| |
| // Otherwise, we've completed an SCC. Append it to our post order list of |
| // SCCs. |
| int RootDFSNumber = N->DFSNumber; |
| // Find the range of the node stack by walking down until we pass the |
| // root DFS number. |
| auto SCCNodes = make_range( |
| PendingSCCStack.rbegin(), |
| find_if(reverse(PendingSCCStack), [RootDFSNumber](const Node *N) { |
| return N->DFSNumber < RootDFSNumber; |
| })); |
| // Form a new SCC out of these nodes and then clear them off our pending |
| // stack. |
| RC.SCCs.push_back(createSCC(RC, SCCNodes)); |
| for (Node &N : *RC.SCCs.back()) { |
| N.DFSNumber = N.LowLink = -1; |
| SCCMap[&N] = RC.SCCs.back(); |
| } |
| PendingSCCStack.erase(SCCNodes.end().base(), PendingSCCStack.end()); |
| } while (!DFSStack.empty()); |
| } |
| |
| // Wire up the SCC indices. |
| for (int i = 0, Size = RC.SCCs.size(); i < Size; ++i) |
| RC.SCCIndices[RC.SCCs[i]] = i; |
| } |
| |
| // FIXME: We should move callers of this to embed the parent linking and leaf |
| // tracking into their DFS in order to remove a full walk of all edges. |
| void LazyCallGraph::connectRefSCC(RefSCC &RC) { |
| // Walk all edges in the RefSCC (this remains linear as we only do this once |
| // when we build the RefSCC) to connect it to the parent sets of its |
| // children. |
| bool IsLeaf = true; |
| for (SCC &C : RC) |
| for (Node &N : C) |
| for (Edge &E : N) { |
| assert(E.getNode() && |
| "Cannot have a missing node in a visited part of the graph!"); |
| RefSCC &ChildRC = *lookupRefSCC(*E.getNode()); |
| if (&ChildRC == &RC) |
| continue; |
| ChildRC.Parents.insert(&RC); |
| IsLeaf = false; |
| } |
| |
| // For the SCCs where we find no child SCCs, add them to the leaf list. |
| if (IsLeaf) |
| LeafRefSCCs.push_back(&RC); |
| } |
| |
| bool LazyCallGraph::buildNextRefSCCInPostOrder() { |
| if (DFSStack.empty()) { |
| Node *N; |
| do { |
| // If we've handled all candidate entry nodes to the SCC forest, we're |
| // done. |
| if (RefSCCEntryNodes.empty()) |
| return false; |
| |
| N = &get(*RefSCCEntryNodes.pop_back_val()); |
| } while (N->DFSNumber != 0); |
| |
| // Found a new root, begin the DFS here. |
| N->LowLink = N->DFSNumber = 1; |
| NextDFSNumber = 2; |
| DFSStack.push_back({N, N->begin()}); |
| } |
| |
| for (;;) { |
| Node *N; |
| edge_iterator I; |
| std::tie(N, I) = DFSStack.pop_back_val(); |
| |
| assert(N->DFSNumber > 0 && "We should always assign a DFS number " |
| "before placing a node onto the stack."); |
| |
| auto E = N->end(); |
| while (I != E) { |
| Node &ChildN = I->getNode(*this); |
| if (ChildN.DFSNumber == 0) { |
| // We haven't yet visited this child, so descend, pushing the current |
| // node onto the stack. |
| DFSStack.push_back({N, N->begin()}); |
| |
| assert(!SCCMap.count(&ChildN) && |
| "Found a node with 0 DFS number but already in an SCC!"); |
| ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++; |
| N = &ChildN; |
| I = N->begin(); |
| E = N->end(); |
| continue; |
| } |
| |
| // If the child has already been added to some child component, it |
| // couldn't impact the low-link of this parent because it isn't |
| // connected, and thus its low-link isn't relevant so skip it. |
| if (ChildN.DFSNumber == -1) { |
| ++I; |
| continue; |
| } |
| |
| // Track the lowest linked child as the lowest link for this node. |
| assert(ChildN.LowLink > 0 && "Must have a positive low-link number!"); |
| if (ChildN.LowLink < N->LowLink) |
| N->LowLink = ChildN.LowLink; |
| |
| // Move to the next edge. |
| ++I; |
| } |
| |
| // We've finished processing N and its descendents, put it on our pending |
| // SCC stack to eventually get merged into an SCC of nodes. |
| PendingRefSCCStack.push_back(N); |
| |
| // If this node is linked to some lower entry, continue walking up the |
| // stack. |
| if (N->LowLink != N->DFSNumber) { |
| assert(!DFSStack.empty() && |
| "We never found a viable root for an SCC to pop off!"); |
| continue; |
| } |
| |
| // Otherwise, form a new RefSCC from the top of the pending node stack. |
| int RootDFSNumber = N->DFSNumber; |
| // Find the range of the node stack by walking down until we pass the |
| // root DFS number. |
| auto RefSCCNodes = node_stack_range( |
| PendingRefSCCStack.rbegin(), |
| find_if(reverse(PendingRefSCCStack), [RootDFSNumber](const Node *N) { |
| return N->DFSNumber < RootDFSNumber; |
| })); |
| // Form a new RefSCC out of these nodes and then clear them off our pending |
| // stack. |
| RefSCC *NewRC = createRefSCC(*this); |
| buildSCCs(*NewRC, RefSCCNodes); |
| connectRefSCC(*NewRC); |
| PendingRefSCCStack.erase(RefSCCNodes.end().base(), |
| PendingRefSCCStack.end()); |
| |
| // Push the new node into the postorder list and return true indicating we |
| // successfully grew the postorder sequence by one. |
| bool Inserted = |
| RefSCCIndices.insert({NewRC, PostOrderRefSCCs.size()}).second; |
| (void)Inserted; |
| assert(Inserted && "Cannot already have this RefSCC in the index map!"); |
| PostOrderRefSCCs.push_back(NewRC); |
| return true; |
| } |
| } |
| |
| AnalysisKey LazyCallGraphAnalysis::Key; |
| |
| LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {} |
| |
| static void printNode(raw_ostream &OS, LazyCallGraph::Node &N) { |
| OS << " Edges in function: " << N.getFunction().getName() << "\n"; |
| for (const LazyCallGraph::Edge &E : N) |
| OS << " " << (E.isCall() ? "call" : "ref ") << " -> " |
| << E.getFunction().getName() << "\n"; |
| |
| OS << "\n"; |
| } |
| |
| static void printSCC(raw_ostream &OS, LazyCallGraph::SCC &C) { |
| ptrdiff_t Size = std::distance(C.begin(), C.end()); |
| OS << " SCC with " << Size << " functions:\n"; |
| |
| for (LazyCallGraph::Node &N : C) |
| OS << " " << N.getFunction().getName() << "\n"; |
| } |
| |
| static void printRefSCC(raw_ostream &OS, LazyCallGraph::RefSCC &C) { |
| ptrdiff_t Size = std::distance(C.begin(), C.end()); |
| OS << " RefSCC with " << Size << " call SCCs:\n"; |
| |
| for (LazyCallGraph::SCC &InnerC : C) |
| printSCC(OS, InnerC); |
| |
| OS << "\n"; |
| } |
| |
| PreservedAnalyses LazyCallGraphPrinterPass::run(Module &M, |
| ModuleAnalysisManager &AM) { |
| LazyCallGraph &G = AM.getResult<LazyCallGraphAnalysis>(M); |
| |
| OS << "Printing the call graph for module: " << M.getModuleIdentifier() |
| << "\n\n"; |
| |
| for (Function &F : M) |
| printNode(OS, G.get(F)); |
| |
| for (LazyCallGraph::RefSCC &C : G.postorder_ref_sccs()) |
| printRefSCC(OS, C); |
| |
| return PreservedAnalyses::all(); |
| } |
| |
| LazyCallGraphDOTPrinterPass::LazyCallGraphDOTPrinterPass(raw_ostream &OS) |
| : OS(OS) {} |
| |
| static void printNodeDOT(raw_ostream &OS, LazyCallGraph::Node &N) { |
| std::string Name = "\"" + DOT::EscapeString(N.getFunction().getName()) + "\""; |
| |
| for (const LazyCallGraph::Edge &E : N) { |
| OS << " " << Name << " -> \"" |
| << DOT::EscapeString(E.getFunction().getName()) << "\""; |
| if (!E.isCall()) // It is a ref edge. |
| OS << " [style=dashed,label=\"ref\"]"; |
| OS << ";\n"; |
| } |
| |
| OS << "\n"; |
| } |
| |
| PreservedAnalyses LazyCallGraphDOTPrinterPass::run(Module &M, |
| ModuleAnalysisManager &AM) { |
| LazyCallGraph &G = AM.getResult<LazyCallGraphAnalysis>(M); |
| |
| OS << "digraph \"" << DOT::EscapeString(M.getModuleIdentifier()) << "\" {\n"; |
| |
| for (Function &F : M) |
| printNodeDOT(OS, G.get(F)); |
| |
| OS << "}\n"; |
| |
| return PreservedAnalyses::all(); |
| } |