| //===- 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/STLExtras.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) { |
| // 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. |
| if (!F.isDeclaration() && |
| EdgeIndexMap.insert({&F, Edges.size()}).second) { |
| DEBUG(dbgs() << " Added callable function: " << F.getName() << "\n"); |
| Edges.emplace_back(LazyCallGraph::Edge(F, EK)); |
| } |
| } |
| |
| static void findReferences(SmallVectorImpl<Constant *> &Worklist, |
| SmallPtrSetImpl<Constant *> &Visited, |
| SmallVectorImpl<LazyCallGraph::Edge> &Edges, |
| DenseMap<Function *, int> &EdgeIndexMap) { |
| while (!Worklist.empty()) { |
| Constant *C = Worklist.pop_back_val(); |
| |
| if (Function *F = dyn_cast<Function>(C)) { |
| addEdge(Edges, EdgeIndexMap, *F, LazyCallGraph::Edge::Ref); |
| continue; |
| } |
| |
| for (Value *Op : C->operand_values()) |
| if (Visited.insert(cast<Constant>(Op)).second) |
| Worklist.push_back(cast<Constant>(Op)); |
| } |
| } |
| |
| 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. |
| for (BasicBlock &BB : F) |
| for (Instruction &I : BB) { |
| if (auto CS = CallSite(&I)) |
| if (Function *Callee = CS.getCalledFunction()) |
| 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. |
| findReferences(Worklist, Visited, Edges, EdgeIndexMap); |
| } |
| |
| 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"); |
| findReferences(Worklist, Visited, EntryEdges, EntryIndexMap); |
| |
| 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 |
| |
| 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. |
| 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!"); |
| } |
| |
| // 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(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."); |
| } |
| } |
| } |
| #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; |
| } |
| |
| 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; |
| |
| 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); |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| 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); |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| return DeletedSCCs; |
| } |
| |
| // When we do have an edge from an earlier SCC to a later SCC in the |
| // postorder sequence, all of the SCCs which may be impacted are in the |
| // closed range of those two within the postorder sequence. The algorithm 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. |
| |
| assert(SourceIdx < TargetIdx && "Cannot have equal indices here!"); |
| SmallPtrSet<SCC *, 4> ConnectedSet; |
| |
| // Compute the SCCs which (transitively) reach the source. |
| 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); |
| |
| // 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](SCC *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."); |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Call); |
| #ifndef NDEBUG |
| verify(); |
| #endif |
| return DeletedSCCs; |
| } |
| |
| assert(SCCs[TargetIdx] == &TargetSCC && |
| "Should not have moved target if connected!"); |
| SourceIdx = SourceI - SCCs.begin(); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| |
| // 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) { |
| // 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. |
| ConnectedSet.clear(); |
| 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()); |
| |
| // 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](SCC *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!"); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| } |
| |
| // 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. This means that we need to merge all of these SCCs 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. |
| auto MergeRange = |
| make_range(SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx); |
| 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); |
| |
| #ifndef NDEBUG |
| // And we're done! Verify in debug builds that the RefSCC is coherent. |
| verify(); |
| #endif |
| return DeletedSCCs; |
| } |
| |
| void LazyCallGraph::RefSCC::switchInternalEdgeToRef(Node &SourceN, |
| Node &TargetN) { |
| assert(SourceN[TargetN].isCall() && "Must start with a call edge!"); |
| |
| SCC &SourceSCC = *G->lookupSCC(SourceN); |
| SCC &TargetSCC = *G->lookupSCC(TargetN); |
| |
| assert(&SourceSCC.getOuterRefSCC() == this && |
| "Source must be in this RefSCC."); |
| assert(&TargetSCC.getOuterRefSCC() == this && |
| "Target must be in this RefSCC."); |
| |
| // Set the edge kind. |
| SourceN.setEdgeKind(TargetN.getFunction(), Edge::Ref); |
| |
| // If this call edge is just connecting two separate SCCs within this RefSCC, |
| // there is nothing to do. |
| if (&SourceSCC != &TargetSCC) { |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| return; |
| } |
| |
| // 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(), |
| std::find_if(PendingSCCStack.rbegin(), PendingSCCStack.rend(), |
| [RootDFSNumber](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; |
| |
| #ifndef NDEBUG |
| // We're done. Check the validity on our way out. |
| verify(); |
| #endif |
| } |
| |
| 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 SCC."); |
| |
| // We store the RefSCCs found to be connected in postorder so that we can use |
| // that when merging. We also return this to the caller to allow them to |
| // invalidate information pertaining to these RefSCCs. |
| SmallVector<RefSCC *, 1> Connected; |
| |
| RefSCC &SourceC = *G->lookupRefSCC(SourceN); |
| assert(&SourceC != this && "Source must not be in this SCC."); |
| assert(SourceC.isDescendantOf(*this) && |
| "Source must be a descendant of the Target."); |
| |
| // The algorithm we use for merging SCCs based on the cycle introduced here |
| // is to walk the RefSCC inverted DAG formed by the parent sets. The inverse |
| // graph has the same cycle properties as the actual DAG of the RefSCCs, and |
| // when forming RefSCCs lazily by a DFS, the bottom of the graph won't exist |
| // in many cases which should prune the search space. |
| // |
| // FIXME: We can get this pruning behavior even after the incremental RefSCC |
| // formation by leaving behind (conservative) DFS numberings in the nodes, |
| // and pruning the search with them. These would need to be cleverly updated |
| // during the removal of intra-SCC edges, but could be preserved |
| // conservatively. |
| // |
| // FIXME: This operation currently creates ordering stability problems |
| // because we don't use stably ordered containers for the parent SCCs. |
| |
| // The set of RefSCCs that are connected to the parent, and thus will |
| // participate in the merged connected component. |
| SmallPtrSet<RefSCC *, 8> ConnectedSet; |
| ConnectedSet.insert(this); |
| |
| // We build up a DFS stack of the parents chains. |
| SmallVector<std::pair<RefSCC *, parent_iterator>, 8> DFSStack; |
| SmallPtrSet<RefSCC *, 8> Visited; |
| int ConnectedDepth = -1; |
| DFSStack.push_back({&SourceC, SourceC.parent_begin()}); |
| do { |
| auto DFSPair = DFSStack.pop_back_val(); |
| RefSCC *C = DFSPair.first; |
| parent_iterator I = DFSPair.second; |
| auto E = C->parent_end(); |
| |
| while (I != E) { |
| RefSCC &Parent = *I++; |
| |
| // If we have already processed this parent SCC, skip it, and remember |
| // whether it was connected so we don't have to check the rest of the |
| // stack. This also handles when we reach a child of the 'this' SCC (the |
| // callee) which terminates the search. |
| if (ConnectedSet.count(&Parent)) { |
| assert(ConnectedDepth < (int)DFSStack.size() && |
| "Cannot have a connected depth greater than the DFS depth!"); |
| ConnectedDepth = DFSStack.size(); |
| continue; |
| } |
| if (Visited.count(&Parent)) |
| continue; |
| |
| // We fully explore the depth-first space, adding nodes to the connected |
| // set only as we pop them off, so "recurse" by rotating to the parent. |
| DFSStack.push_back({C, I}); |
| C = &Parent; |
| I = C->parent_begin(); |
| E = C->parent_end(); |
| } |
| |
| // If we've found a connection anywhere below this point on the stack (and |
| // thus up the parent graph from the caller), the current node needs to be |
| // added to the connected set now that we've processed all of its parents. |
| if ((int)DFSStack.size() == ConnectedDepth) { |
| --ConnectedDepth; // We're finished with this connection. |
| bool Inserted = ConnectedSet.insert(C).second; |
| (void)Inserted; |
| assert(Inserted && "Cannot insert a refSCC multiple times!"); |
| Connected.push_back(C); |
| } else { |
| // Otherwise remember that its parents don't ever connect. |
| assert(ConnectedDepth < (int)DFSStack.size() && |
| "Cannot have a connected depth greater than the DFS depth!"); |
| Visited.insert(C); |
| } |
| } while (!DFSStack.empty()); |
| |
| // 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. |
| // We walk the newly connected RefSCCs in the reverse postorder of the parent |
| // DAG walk above and merge in each of their SCC postorder lists. This |
| // ensures a merged postorder SCC list. |
| SmallVector<SCC *, 16> MergedSCCs; |
| int SCCIndex = 0; |
| for (RefSCC *C : reverse(Connected)) { |
| assert(C != this && |
| "This RefSCC should terminate the DFS without being reached."); |
| |
| // Merge the parents which aren't part of the merge into the our parents. |
| for (RefSCC *ParentC : C->Parents) |
| if (!ConnectedSet.count(ParentC)) |
| Parents.insert(ParentC); |
| C->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 : *C) { |
| 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 (ConnectedSet.count(&ChildRC)) |
| continue; |
| ChildRC.Parents.erase(C); |
| 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(C->SCCs); |
| else |
| MergedSCCs.append(C->SCCs.begin(), C->SCCs.end()); |
| C->SCCs.clear(); |
| } |
| |
| // Finally 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); |
| |
| // 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); |
| |
| #ifndef NDEBUG |
| // Check that the RefSCC is still valid. |
| verify(); |
| #endif |
| |
| // 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 Connected; |
| } |
| |
| 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(std::find(G->LeafRefSCCs.begin(), G->LeafRefSCCs.end(), this) == |
| G->LeafRefSCCs.end() && |
| "Cannot have a leaf RefSCC source."); |
| |
| // 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"); |
| |
| // 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; |
| |
| // 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. |
| SCC &TargetC = *G->lookupSCC(TargetN); |
| 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(), |
| std::find_if(PendingRefSCCStack.rbegin(), PendingRefSCCStack.rend(), |
| [RootDFSNumber](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)); |
| |
| 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); |
| 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(std::remove_if(SCCs.begin(), SCCs.end(), |
| [&](SCC *C) { |
| return PostOrderMapping.lookup(&*C->begin()) != |
| RootPostOrderNumber; |
| }), |
| SCCs.end()); |
| |
| #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 (!std::any_of(G->LeafRefSCCs.begin(), G->LeafRefSCCs.end(), |
| [&](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 |
| // 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()); |
| |
| // Return the new list of SCCs. |
| return Result; |
| } |
| |
| 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); |
| } |
| |
| 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(), |
| std::find_if(PendingSCCStack.rbegin(), PendingSCCStack.rend(), |
| [RootDFSNumber](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 fine no child SCCs, add them to the leaf list. |
| if (IsLeaf) |
| LeafRefSCCs.push_back(&RC); |
| } |
| |
| LazyCallGraph::RefSCC *LazyCallGraph::getNextRefSCCInPostOrder() { |
| 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 nullptr; |
| |
| 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(), |
| std::find_if( |
| PendingRefSCCStack.rbegin(), PendingRefSCCStack.rend(), |
| [RootDFSNumber](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()); |
| |
| // We return the new node here. This essentially suspends the DFS walk |
| // until another RefSCC is requested. |
| return NewRC; |
| } |
| } |
| |
| char LazyCallGraphAnalysis::PassID; |
| |
| 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(); |
| } |