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Diffstat (limited to 'contrib/llvm/lib/Analysis/LazyCallGraph.cpp')
| -rw-r--r-- | contrib/llvm/lib/Analysis/LazyCallGraph.cpp | 728 |
1 files changed, 728 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Analysis/LazyCallGraph.cpp b/contrib/llvm/lib/Analysis/LazyCallGraph.cpp new file mode 100644 index 000000000000..e0736162a77a --- /dev/null +++ b/contrib/llvm/lib/Analysis/LazyCallGraph.cpp @@ -0,0 +1,728 @@ +//===- 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/raw_ostream.h" + +using namespace llvm; + +#define DEBUG_TYPE "lcg" + +static void findCallees( + SmallVectorImpl<Constant *> &Worklist, SmallPtrSetImpl<Constant *> &Visited, + SmallVectorImpl<PointerUnion<Function *, LazyCallGraph::Node *>> &Callees, + DenseMap<Function *, size_t> &CalleeIndexMap) { + while (!Worklist.empty()) { + Constant *C = Worklist.pop_back_val(); + + if (Function *F = dyn_cast<Function>(C)) { + // 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() && + CalleeIndexMap.insert(std::make_pair(F, Callees.size())).second) { + DEBUG(dbgs() << " Added callable function: " << F->getName() + << "\n"); + Callees.push_back(F); + } + continue; + } + + for (Value *Op : C->operand_values()) + if (Visited.insert(cast<Constant>(Op))) + 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<Constant *, 16> Visited; + // Find all the potential callees in this function. First walk the + // instructions and add every operand which is a constant to the worklist. + for (BasicBlock &BB : F) + for (Instruction &I : BB) + for (Value *Op : I.operand_values()) + if (Constant *C = dyn_cast<Constant>(Op)) + if (Visited.insert(C)) + 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. + findCallees(Worklist, Visited, Callees, CalleeIndexMap); +} + +void LazyCallGraph::Node::insertEdgeInternal(Function &Callee) { + if (Node *N = G->lookup(Callee)) + return insertEdgeInternal(*N); + + CalleeIndexMap.insert(std::make_pair(&Callee, Callees.size())); + Callees.push_back(&Callee); +} + +void LazyCallGraph::Node::insertEdgeInternal(Node &CalleeN) { + CalleeIndexMap.insert(std::make_pair(&CalleeN.getFunction(), Callees.size())); + Callees.push_back(&CalleeN); +} + +void LazyCallGraph::Node::removeEdgeInternal(Function &Callee) { + auto IndexMapI = CalleeIndexMap.find(&Callee); + assert(IndexMapI != CalleeIndexMap.end() && + "Callee not in the callee set for this caller?"); + + Callees[IndexMapI->second] = nullptr; + CalleeIndexMap.erase(IndexMapI); +} + +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(std::make_pair(&F, EntryNodes.size())).second) { + DEBUG(dbgs() << " Adding '" << F.getName() + << "' to entry set of the graph.\n"); + EntryNodes.push_back(&F); + } + + // 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())) + Worklist.push_back(GV.getInitializer()); + + DEBUG(dbgs() << " Adding functions referenced by global initializers to the " + "entry set.\n"); + findCallees(Worklist, Visited, EntryNodes, EntryIndexMap); + + for (auto &Entry : EntryNodes) { + assert(!Entry.isNull() && + "We can't have removed edges before we finish the constructor!"); + if (Function *F = Entry.dyn_cast<Function *>()) + SCCEntryNodes.push_back(F); + else + SCCEntryNodes.push_back(&Entry.get<Node *>()->getFunction()); + } +} + +LazyCallGraph::LazyCallGraph(LazyCallGraph &&G) + : BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)), + EntryNodes(std::move(G.EntryNodes)), + EntryIndexMap(std::move(G.EntryIndexMap)), SCCBPA(std::move(G.SCCBPA)), + SCCMap(std::move(G.SCCMap)), LeafSCCs(std::move(G.LeafSCCs)), + DFSStack(std::move(G.DFSStack)), + SCCEntryNodes(std::move(G.SCCEntryNodes)), + NextDFSNumber(G.NextDFSNumber) { + updateGraphPtrs(); +} + +LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) { + BPA = std::move(G.BPA); + NodeMap = std::move(G.NodeMap); + EntryNodes = std::move(G.EntryNodes); + EntryIndexMap = std::move(G.EntryIndexMap); + SCCBPA = std::move(G.SCCBPA); + SCCMap = std::move(G.SCCMap); + LeafSCCs = std::move(G.LeafSCCs); + DFSStack = std::move(G.DFSStack); + SCCEntryNodes = std::move(G.SCCEntryNodes); + NextDFSNumber = G.NextDFSNumber; + updateGraphPtrs(); + return *this; +} + +void LazyCallGraph::SCC::insert(Node &N) { + N.DFSNumber = N.LowLink = -1; + Nodes.push_back(&N); + G->SCCMap[&N] = this; +} + +bool LazyCallGraph::SCC::isDescendantOf(const SCC &C) const { + // Walk up the parents of this SCC and verify that we eventually find C. + SmallVector<const SCC *, 4> AncestorWorklist; + AncestorWorklist.push_back(this); + do { + const SCC *AncestorC = AncestorWorklist.pop_back_val(); + if (AncestorC->isChildOf(C)) + return true; + for (const SCC *ParentC : AncestorC->ParentSCCs) + AncestorWorklist.push_back(ParentC); + } while (!AncestorWorklist.empty()); + + return false; +} + +void LazyCallGraph::SCC::insertIntraSCCEdge(Node &CallerN, Node &CalleeN) { + // First insert it into the caller. + CallerN.insertEdgeInternal(CalleeN); + + assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC."); + assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC."); + + // Nothing changes about this SCC or any other. +} + +void LazyCallGraph::SCC::insertOutgoingEdge(Node &CallerN, Node &CalleeN) { + // First insert it into the caller. + CallerN.insertEdgeInternal(CalleeN); + + assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC."); + + SCC &CalleeC = *G->SCCMap.lookup(&CalleeN); + assert(&CalleeC != this && "Callee must not be in this SCC."); + assert(CalleeC.isDescendantOf(*this) && + "Callee must be a descendant of the Caller."); + + // The only change required is to add this SCC to the parent set of the callee. + CalleeC.ParentSCCs.insert(this); +} + +SmallVector<LazyCallGraph::SCC *, 1> +LazyCallGraph::SCC::insertIncomingEdge(Node &CallerN, Node &CalleeN) { + // First insert it into the caller. + CallerN.insertEdgeInternal(CalleeN); + + assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC."); + + SCC &CallerC = *G->SCCMap.lookup(&CallerN); + assert(&CallerC != this && "Caller must not be in this SCC."); + assert(CallerC.isDescendantOf(*this) && + "Caller must be a descendant of the Callee."); + + // The algorithm we use for merging SCCs based on the cycle introduced here + // is to walk the SCC inverted DAG formed by the parent SCC sets. The inverse + // graph has the same cycle properties as the actual DAG of the SCCs, and + // when forming SCCs 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 SCC + // 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. + + // The set of SCCs that are connected to the caller, and thus will + // participate in the merged connected component. + SmallPtrSet<SCC *, 8> ConnectedSCCs; + ConnectedSCCs.insert(this); + ConnectedSCCs.insert(&CallerC); + + // We build up a DFS stack of the parents chains. + SmallVector<std::pair<SCC *, SCC::parent_iterator>, 8> DFSSCCs; + SmallPtrSet<SCC *, 8> VisitedSCCs; + int ConnectedDepth = -1; + SCC *C = this; + parent_iterator I = parent_begin(), E = parent_end(); + for (;;) { + while (I != E) { + SCC &ParentSCC = *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 (ConnectedSCCs.count(&ParentSCC)) { + ConnectedDepth = std::max<int>(ConnectedDepth, DFSSCCs.size()); + continue; + } + if (VisitedSCCs.count(&ParentSCC)) + 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. + DFSSCCs.push_back(std::make_pair(C, I)); + C = &ParentSCC; + I = ParentSCC.parent_begin(); + E = ParentSCC.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)DFSSCCs.size() == ConnectedDepth) { + --ConnectedDepth; // We're finished with this connection. + ConnectedSCCs.insert(C); + } else { + // Otherwise remember that its parents don't ever connect. + assert(ConnectedDepth < (int)DFSSCCs.size() && + "Cannot have a connected depth greater than the DFS depth!"); + VisitedSCCs.insert(C); + } + + if (DFSSCCs.empty()) + break; // We've walked all the parents of the caller transitively. + + // Pop off the prior node and position to unwind the depth first recursion. + std::tie(C, I) = DFSSCCs.pop_back_val(); + E = C->parent_end(); + } + + // 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. + // FIXME: This operation currently creates ordering stability problems + // because we don't use stably ordered containers for the parent SCCs or the + // connected SCCs. + unsigned NewNodeBeginIdx = Nodes.size(); + for (SCC *C : ConnectedSCCs) { + if (C == this) + continue; + for (SCC *ParentC : C->ParentSCCs) + if (!ConnectedSCCs.count(ParentC)) + ParentSCCs.insert(ParentC); + C->ParentSCCs.clear(); + + for (Node *N : *C) { + for (Node &ChildN : *N) { + SCC &ChildC = *G->SCCMap.lookup(&ChildN); + if (&ChildC != C) + ChildC.ParentSCCs.erase(C); + } + G->SCCMap[N] = this; + Nodes.push_back(N); + } + C->Nodes.clear(); + } + for (auto I = Nodes.begin() + NewNodeBeginIdx, E = Nodes.end(); I != E; ++I) + for (Node &ChildN : **I) { + SCC &ChildC = *G->SCCMap.lookup(&ChildN); + if (&ChildC != this) + ChildC.ParentSCCs.insert(this); + } + + // 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 SmallVector<SCC *, 1>(ConnectedSCCs.begin(), ConnectedSCCs.end()); +} + +void LazyCallGraph::SCC::removeInterSCCEdge(Node &CallerN, Node &CalleeN) { + // First remove it from the node. + CallerN.removeEdgeInternal(CalleeN.getFunction()); + + assert(G->SCCMap.lookup(&CallerN) == this && + "The caller must be a member of this SCC."); + + SCC &CalleeC = *G->SCCMap.lookup(&CalleeN); + assert(&CalleeC != this && + "This API only supports the rmoval of inter-SCC edges."); + + assert(std::find(G->LeafSCCs.begin(), G->LeafSCCs.end(), this) == + G->LeafSCCs.end() && + "Cannot have a leaf SCC caller with a different SCC callee."); + + bool HasOtherCallToCalleeC = false; + bool HasOtherCallOutsideSCC = false; + for (Node *N : *this) { + for (Node &OtherCalleeN : *N) { + SCC &OtherCalleeC = *G->SCCMap.lookup(&OtherCalleeN); + if (&OtherCalleeC == &CalleeC) { + HasOtherCallToCalleeC = true; + break; + } + if (&OtherCalleeC != this) + HasOtherCallOutsideSCC = true; + } + if (HasOtherCallToCalleeC) + 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 caller no longer a parent of the callee. Walk the other call edges + // in the caller to tell. + if (!HasOtherCallToCalleeC) { + bool Removed = CalleeC.ParentSCCs.erase(this); + (void)Removed; + assert(Removed && + "Did not find the caller SCC in the callee 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 (CalleeC.ParentSCCs.empty()) + DEBUG(dbgs() << "LCG: Update removing " << CallerN.getFunction().getName() + << " -> " << CalleeN.getFunction().getName() + << " edge orphaned the callee's SCC!\n"); + } + + // It may make the Caller SCC a leaf SCC. + if (!HasOtherCallOutsideSCC) + G->LeafSCCs.push_back(this); +} + +void LazyCallGraph::SCC::internalDFS( + SmallVectorImpl<std::pair<Node *, Node::iterator>> &DFSStack, + SmallVectorImpl<Node *> &PendingSCCStack, Node *N, + SmallVectorImpl<SCC *> &ResultSCCs) { + Node::iterator I = N->begin(); + N->LowLink = N->DFSNumber = 1; + int NextDFSNumber = 2; + for (;;) { + assert(N->DFSNumber != 0 && "We should always assign a DFS number " + "before processing a node."); + + // We simulate recursion by popping out of the nested loop and continuing. + Node::iterator E = N->end(); + while (I != E) { + Node &ChildN = *I; + if (SCC *ChildSCC = G->SCCMap.lookup(&ChildN)) { + // Check if we have reached a node in the new (known connected) set of + // this SCC. If so, the entire stack is necessarily in that set and we + // can re-start. + if (ChildSCC == this) { + insert(*N); + while (!PendingSCCStack.empty()) + insert(*PendingSCCStack.pop_back_val()); + while (!DFSStack.empty()) + insert(*DFSStack.pop_back_val().first); + return; + } + + // If this child isn't currently in this SCC, no need to process it. + // However, we do need to remove this SCC from its SCC's parent set. + ChildSCC->ParentSCCs.erase(this); + ++I; + continue; + } + + 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(std::make_pair(N, I)); + + // Continue, resetting to the child node. + ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++; + N = &ChildN; + I = ChildN.begin(); + E = ChildN.end(); + 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->LowLink == N->DFSNumber) { + ResultSCCs.push_back(G->formSCC(N, PendingSCCStack)); + if (DFSStack.empty()) + return; + } else { + // At this point we know that N cannot ever be an SCC root. Its low-link + // is not its dfs-number, and we've processed all of its children. It is + // just sitting here waiting until some node further down the stack gets + // low-link == dfs-number and pops it off as well. Move it to the pending + // stack which is pulled into the next SCC to be formed. + PendingSCCStack.push_back(N); + + assert(!DFSStack.empty() && "We shouldn't have an empty stack!"); + } + + N = DFSStack.back().first; + I = DFSStack.back().second; + DFSStack.pop_back(); + } +} + +SmallVector<LazyCallGraph::SCC *, 1> +LazyCallGraph::SCC::removeIntraSCCEdge(Node &CallerN, + Node &CalleeN) { + // First remove it from the node. + CallerN.removeEdgeInternal(CalleeN.getFunction()); + + // We return a list of the resulting *new* SCCs in postorder. + SmallVector<SCC *, 1> ResultSCCs; + + // Direct recursion doesn't impact the SCC graph at all. + if (&CallerN == &CalleeN) + return ResultSCCs; + + // The worklist is every node in the original SCC. + SmallVector<Node *, 1> Worklist; + Worklist.swap(Nodes); + for (Node *N : Worklist) { + // The nodes formerly in this SCC are no longer in any SCC. + N->DFSNumber = 0; + N->LowLink = 0; + G->SCCMap.erase(N); + } + assert(Worklist.size() > 1 && "We have to have at least two nodes to have an " + "edge between them that is within the SCC."); + + // The callee can already reach every node in this SCC (by definition). It is + // the only node we know will stay inside this SCC. Everything which + // transitively reaches Callee will also remain in the SCC. To model this we + // incrementally add any chain of nodes which reaches something in the new + // node set to the new node set. This short circuits one side of the Tarjan's + // walk. + insert(CalleeN); + + // We're going to do a full mini-Tarjan's walk using a local stack here. + SmallVector<std::pair<Node *, Node::iterator>, 4> DFSStack; + SmallVector<Node *, 4> PendingSCCStack; + do { + Node *N = Worklist.pop_back_val(); + if (N->DFSNumber == 0) + internalDFS(DFSStack, PendingSCCStack, N, ResultSCCs); + + assert(DFSStack.empty() && "Didn't flush the entire DFS stack!"); + assert(PendingSCCStack.empty() && "Didn't flush all pending SCC nodes!"); + } while (!Worklist.empty()); + + // Now we need to reconnect the current SCC to the graph. + bool IsLeafSCC = true; + for (Node *N : Nodes) { + for (Node &ChildN : *N) { + SCC &ChildSCC = *G->SCCMap.lookup(&ChildN); + if (&ChildSCC == this) + continue; + ChildSCC.ParentSCCs.insert(this); + IsLeafSCC = false; + } + } +#ifndef NDEBUG + if (!ResultSCCs.empty()) + assert(!IsLeafSCC && "This SCC cannot be a leaf as we have split out new " + "SCCs by removing this edge."); + if (!std::any_of(G->LeafSCCs.begin(), G->LeafSCCs.end(), + [&](SCC *C) { return C == this; })) + assert(!IsLeafSCC && "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. + if (!IsLeafSCC && !ResultSCCs.empty()) + G->LeafSCCs.erase(std::remove(G->LeafSCCs.begin(), G->LeafSCCs.end(), this), + G->LeafSCCs.end()); + + // Return the new list of SCCs. + return ResultSCCs; +} + +void LazyCallGraph::insertEdge(Node &CallerN, Function &Callee) { + assert(SCCMap.empty() && DFSStack.empty() && + "This method cannot be called after SCCs have been formed!"); + + return CallerN.insertEdgeInternal(Callee); +} + +void LazyCallGraph::removeEdge(Node &CallerN, Function &Callee) { + assert(SCCMap.empty() && DFSStack.empty() && + "This method cannot be called after SCCs have been formed!"); + + return CallerN.removeEdgeInternal(Callee); +} + +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 (auto &Entry : EntryNodes) + if (Node *EntryN = Entry.dyn_cast<Node *>()) + Worklist.push_back(EntryN); + + while (!Worklist.empty()) { + Node *N = Worklist.pop_back_val(); + N->G = this; + for (auto &Callee : N->Callees) + if (!Callee.isNull()) + if (Node *CalleeN = Callee.dyn_cast<Node *>()) + Worklist.push_back(CalleeN); + } + } + + // Process all SCCs updating the graph pointers. + { + SmallVector<SCC *, 16> Worklist(LeafSCCs.begin(), LeafSCCs.end()); + + while (!Worklist.empty()) { + SCC *C = Worklist.pop_back_val(); + C->G = this; + Worklist.insert(Worklist.end(), C->ParentSCCs.begin(), + C->ParentSCCs.end()); + } + } +} + +LazyCallGraph::SCC *LazyCallGraph::formSCC(Node *RootN, + SmallVectorImpl<Node *> &NodeStack) { + // The tail of the stack is the new SCC. Allocate the SCC and pop the stack + // into it. + SCC *NewSCC = new (SCCBPA.Allocate()) SCC(*this); + + while (!NodeStack.empty() && NodeStack.back()->DFSNumber > RootN->DFSNumber) { + assert(NodeStack.back()->LowLink >= RootN->LowLink && + "We cannot have a low link in an SCC lower than its root on the " + "stack!"); + NewSCC->insert(*NodeStack.pop_back_val()); + } + NewSCC->insert(*RootN); + + // A final pass over all edges in the SCC (this remains linear as we only + // do this once when we build the SCC) to connect it to the parent sets of + // its children. + bool IsLeafSCC = true; + for (Node *SCCN : NewSCC->Nodes) + for (Node &SCCChildN : *SCCN) { + SCC &ChildSCC = *SCCMap.lookup(&SCCChildN); + if (&ChildSCC == NewSCC) + continue; + ChildSCC.ParentSCCs.insert(NewSCC); + IsLeafSCC = false; + } + + // For the SCCs where we fine no child SCCs, add them to the leaf list. + if (IsLeafSCC) + LeafSCCs.push_back(NewSCC); + + return NewSCC; +} + +LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() { + Node *N; + Node::iterator I; + if (!DFSStack.empty()) { + N = DFSStack.back().first; + I = DFSStack.back().second; + DFSStack.pop_back(); + } else { + // If we've handled all candidate entry nodes to the SCC forest, we're done. + do { + if (SCCEntryNodes.empty()) + return nullptr; + + N = &get(*SCCEntryNodes.pop_back_val()); + } while (N->DFSNumber != 0); + I = N->begin(); + N->LowLink = N->DFSNumber = 1; + NextDFSNumber = 2; + } + + for (;;) { + assert(N->DFSNumber != 0 && "We should always assign a DFS number " + "before placing a node onto the stack."); + + Node::iterator E = N->end(); + while (I != E) { + Node &ChildN = *I; + 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(std::make_pair(N, N->begin())); + + // Recurse onto this node via a tail call. + assert(!SCCMap.count(&ChildN) && + "Found a node with 0 DFS number but already in an SCC!"); + ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++; + N = &ChildN; + I = ChildN.begin(); + E = ChildN.end(); + continue; + } + + // Track the lowest link of the children, if any are still in the stack. + 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->LowLink == N->DFSNumber) + // Form the new SCC out of the top of the DFS stack. + return formSCC(N, PendingSCCStack); + + // At this point we know that N cannot ever be an SCC root. Its low-link + // is not its dfs-number, and we've processed all of its children. It is + // just sitting here waiting until some node further down the stack gets + // low-link == dfs-number and pops it off as well. Move it to the pending + // stack which is pulled into the next SCC to be formed. + PendingSCCStack.push_back(N); + + assert(!DFSStack.empty() && "We never found a viable root!"); + N = DFSStack.back().first; + I = DFSStack.back().second; + DFSStack.pop_back(); + } +} + +char LazyCallGraphAnalysis::PassID; + +LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {} + +static void printNodes(raw_ostream &OS, LazyCallGraph::Node &N, + SmallPtrSetImpl<LazyCallGraph::Node *> &Printed) { + // Recurse depth first through the nodes. + for (LazyCallGraph::Node &ChildN : N) + if (Printed.insert(&ChildN)) + printNodes(OS, ChildN, Printed); + + OS << " Call edges in function: " << N.getFunction().getName() << "\n"; + for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I) + OS << " -> " << I->getFunction().getName() << "\n"; + + OS << "\n"; +} + +static void printSCC(raw_ostream &OS, LazyCallGraph::SCC &SCC) { + ptrdiff_t SCCSize = std::distance(SCC.begin(), SCC.end()); + OS << " SCC with " << SCCSize << " functions:\n"; + + for (LazyCallGraph::Node *N : SCC) + OS << " " << N->getFunction().getName() << "\n"; + + 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"; + + SmallPtrSet<LazyCallGraph::Node *, 16> Printed; + for (LazyCallGraph::Node &N : G) + if (Printed.insert(&N)) + printNodes(OS, N, Printed); + + for (LazyCallGraph::SCC &SCC : G.postorder_sccs()) + printSCC(OS, SCC); + + return PreservedAnalyses::all(); + +} |