1968 lines
73 KiB
C++
1968 lines
73 KiB
C++
//===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LazyCallGraph.h"
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#include "llvm/ADT/ScopeExit.h"
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#include "llvm/ADT/Sequence.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/ScopeExit.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/InstVisitor.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/GraphWriter.h"
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using namespace llvm;
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#define DEBUG_TYPE "lcg"
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static void addEdge(SmallVectorImpl<LazyCallGraph::Edge> &Edges,
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DenseMap<Function *, int> &EdgeIndexMap, Function &F,
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LazyCallGraph::Edge::Kind EK) {
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if (!EdgeIndexMap.insert({&F, Edges.size()}).second)
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return;
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DEBUG(dbgs() << " Added callable function: " << F.getName() << "\n");
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Edges.emplace_back(LazyCallGraph::Edge(F, EK));
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}
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LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F)
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: G(&G), F(F), DFSNumber(0), LowLink(0) {
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DEBUG(dbgs() << " Adding functions called by '" << F.getName()
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<< "' to the graph.\n");
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SmallVector<Constant *, 16> Worklist;
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SmallPtrSet<Function *, 4> Callees;
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SmallPtrSet<Constant *, 16> Visited;
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// Find all the potential call graph edges in this function. We track both
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// actual call edges and indirect references to functions. The direct calls
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// are trivially added, but to accumulate the latter we walk the instructions
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// and add every operand which is a constant to the worklist to process
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// afterward.
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//
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// Note that we consider *any* function with a definition to be a viable
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// edge. Even if the function's definition is subject to replacement by
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// some other module (say, a weak definition) there may still be
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// optimizations which essentially speculate based on the definition and
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// a way to check that the specific definition is in fact the one being
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// used. For example, this could be done by moving the weak definition to
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// a strong (internal) definition and making the weak definition be an
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// alias. Then a test of the address of the weak function against the new
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// strong definition's address would be an effective way to determine the
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// safety of optimizing a direct call edge.
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for (BasicBlock &BB : F)
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for (Instruction &I : BB) {
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if (auto CS = CallSite(&I))
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if (Function *Callee = CS.getCalledFunction())
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if (!Callee->isDeclaration())
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if (Callees.insert(Callee).second) {
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Visited.insert(Callee);
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addEdge(Edges, EdgeIndexMap, *Callee, LazyCallGraph::Edge::Call);
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}
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for (Value *Op : I.operand_values())
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if (Constant *C = dyn_cast<Constant>(Op))
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if (Visited.insert(C).second)
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Worklist.push_back(C);
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}
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// We've collected all the constant (and thus potentially function or
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// function containing) operands to all of the instructions in the function.
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// Process them (recursively) collecting every function found.
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visitReferences(Worklist, Visited, [&](Function &F) {
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addEdge(Edges, EdgeIndexMap, F, LazyCallGraph::Edge::Ref);
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});
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}
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void LazyCallGraph::Node::insertEdgeInternal(Function &Target, Edge::Kind EK) {
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if (Node *N = G->lookup(Target))
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return insertEdgeInternal(*N, EK);
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EdgeIndexMap.insert({&Target, Edges.size()});
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Edges.emplace_back(Target, EK);
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}
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void LazyCallGraph::Node::insertEdgeInternal(Node &TargetN, Edge::Kind EK) {
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EdgeIndexMap.insert({&TargetN.getFunction(), Edges.size()});
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Edges.emplace_back(TargetN, EK);
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}
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void LazyCallGraph::Node::setEdgeKind(Function &TargetF, Edge::Kind EK) {
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Edges[EdgeIndexMap.find(&TargetF)->second].setKind(EK);
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}
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void LazyCallGraph::Node::removeEdgeInternal(Function &Target) {
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auto IndexMapI = EdgeIndexMap.find(&Target);
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assert(IndexMapI != EdgeIndexMap.end() &&
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"Target not in the edge set for this caller?");
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Edges[IndexMapI->second] = Edge();
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EdgeIndexMap.erase(IndexMapI);
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}
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void LazyCallGraph::Node::dump() const {
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dbgs() << *this << '\n';
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}
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LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) {
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DEBUG(dbgs() << "Building CG for module: " << M.getModuleIdentifier()
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<< "\n");
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for (Function &F : M)
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if (!F.isDeclaration() && !F.hasLocalLinkage())
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if (EntryIndexMap.insert({&F, EntryEdges.size()}).second) {
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DEBUG(dbgs() << " Adding '" << F.getName()
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<< "' to entry set of the graph.\n");
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EntryEdges.emplace_back(F, Edge::Ref);
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}
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// Now add entry nodes for functions reachable via initializers to globals.
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SmallVector<Constant *, 16> Worklist;
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SmallPtrSet<Constant *, 16> Visited;
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for (GlobalVariable &GV : M.globals())
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if (GV.hasInitializer())
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if (Visited.insert(GV.getInitializer()).second)
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Worklist.push_back(GV.getInitializer());
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DEBUG(dbgs() << " Adding functions referenced by global initializers to the "
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"entry set.\n");
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visitReferences(Worklist, Visited, [&](Function &F) {
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addEdge(EntryEdges, EntryIndexMap, F, LazyCallGraph::Edge::Ref);
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});
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for (const Edge &E : EntryEdges)
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RefSCCEntryNodes.push_back(&E.getFunction());
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}
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LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
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: BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)),
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EntryEdges(std::move(G.EntryEdges)),
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EntryIndexMap(std::move(G.EntryIndexMap)), SCCBPA(std::move(G.SCCBPA)),
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SCCMap(std::move(G.SCCMap)), LeafRefSCCs(std::move(G.LeafRefSCCs)),
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DFSStack(std::move(G.DFSStack)),
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RefSCCEntryNodes(std::move(G.RefSCCEntryNodes)),
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NextDFSNumber(G.NextDFSNumber) {
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updateGraphPtrs();
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}
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LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) {
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BPA = std::move(G.BPA);
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NodeMap = std::move(G.NodeMap);
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EntryEdges = std::move(G.EntryEdges);
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EntryIndexMap = std::move(G.EntryIndexMap);
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SCCBPA = std::move(G.SCCBPA);
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SCCMap = std::move(G.SCCMap);
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LeafRefSCCs = std::move(G.LeafRefSCCs);
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DFSStack = std::move(G.DFSStack);
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RefSCCEntryNodes = std::move(G.RefSCCEntryNodes);
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NextDFSNumber = G.NextDFSNumber;
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updateGraphPtrs();
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return *this;
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}
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void LazyCallGraph::SCC::dump() const {
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dbgs() << *this << '\n';
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}
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#ifndef NDEBUG
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void LazyCallGraph::SCC::verify() {
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assert(OuterRefSCC && "Can't have a null RefSCC!");
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assert(!Nodes.empty() && "Can't have an empty SCC!");
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for (Node *N : Nodes) {
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assert(N && "Can't have a null node!");
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assert(OuterRefSCC->G->lookupSCC(*N) == this &&
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"Node does not map to this SCC!");
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assert(N->DFSNumber == -1 &&
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"Must set DFS numbers to -1 when adding a node to an SCC!");
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assert(N->LowLink == -1 &&
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"Must set low link to -1 when adding a node to an SCC!");
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for (Edge &E : *N)
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assert(E.getNode() && "Can't have an edge to a raw function!");
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}
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}
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#endif
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bool LazyCallGraph::SCC::isParentOf(const SCC &C) const {
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if (this == &C)
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return false;
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for (Node &N : *this)
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for (Edge &E : N.calls())
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if (Node *CalleeN = E.getNode())
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if (OuterRefSCC->G->lookupSCC(*CalleeN) == &C)
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return true;
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// No edges found.
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return false;
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}
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bool LazyCallGraph::SCC::isAncestorOf(const SCC &TargetC) const {
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if (this == &TargetC)
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return false;
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LazyCallGraph &G = *OuterRefSCC->G;
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// Start with this SCC.
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SmallPtrSet<const SCC *, 16> Visited = {this};
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SmallVector<const SCC *, 16> Worklist = {this};
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// Walk down the graph until we run out of edges or find a path to TargetC.
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do {
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const SCC &C = *Worklist.pop_back_val();
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for (Node &N : C)
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for (Edge &E : N.calls()) {
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Node *CalleeN = E.getNode();
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if (!CalleeN)
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continue;
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SCC *CalleeC = G.lookupSCC(*CalleeN);
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if (!CalleeC)
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continue;
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// If the callee's SCC is the TargetC, we're done.
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if (CalleeC == &TargetC)
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return true;
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// If this is the first time we've reached this SCC, put it on the
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// worklist to recurse through.
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if (Visited.insert(CalleeC).second)
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Worklist.push_back(CalleeC);
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}
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} while (!Worklist.empty());
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// No paths found.
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return false;
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}
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LazyCallGraph::RefSCC::RefSCC(LazyCallGraph &G) : G(&G) {}
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void LazyCallGraph::RefSCC::dump() const {
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dbgs() << *this << '\n';
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}
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#ifndef NDEBUG
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void LazyCallGraph::RefSCC::verify() {
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assert(G && "Can't have a null graph!");
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assert(!SCCs.empty() && "Can't have an empty SCC!");
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// Verify basic properties of the SCCs.
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SmallPtrSet<SCC *, 4> SCCSet;
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for (SCC *C : SCCs) {
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assert(C && "Can't have a null SCC!");
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C->verify();
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assert(&C->getOuterRefSCC() == this &&
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"SCC doesn't think it is inside this RefSCC!");
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bool Inserted = SCCSet.insert(C).second;
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assert(Inserted && "Found a duplicate SCC!");
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auto IndexIt = SCCIndices.find(C);
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assert(IndexIt != SCCIndices.end() &&
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"Found an SCC that doesn't have an index!");
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}
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// Check that our indices map correctly.
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for (auto &SCCIndexPair : SCCIndices) {
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SCC *C = SCCIndexPair.first;
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int i = SCCIndexPair.second;
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assert(C && "Can't have a null SCC in the indices!");
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assert(SCCSet.count(C) && "Found an index for an SCC not in the RefSCC!");
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assert(SCCs[i] == C && "Index doesn't point to SCC!");
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}
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// Check that the SCCs are in fact in post-order.
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for (int i = 0, Size = SCCs.size(); i < Size; ++i) {
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SCC &SourceSCC = *SCCs[i];
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for (Node &N : SourceSCC)
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for (Edge &E : N) {
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if (!E.isCall())
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continue;
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SCC &TargetSCC = *G->lookupSCC(*E.getNode());
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if (&TargetSCC.getOuterRefSCC() == this) {
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assert(SCCIndices.find(&TargetSCC)->second <= i &&
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"Edge between SCCs violates post-order relationship.");
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continue;
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}
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assert(TargetSCC.getOuterRefSCC().Parents.count(this) &&
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"Edge to a RefSCC missing us in its parent set.");
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}
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}
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// Check that our parents are actually parents.
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for (RefSCC *ParentRC : Parents) {
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assert(ParentRC != this && "Cannot be our own parent!");
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auto HasConnectingEdge = [&] {
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for (SCC &C : *ParentRC)
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for (Node &N : C)
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for (Edge &E : N)
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if (G->lookupRefSCC(*E.getNode()) == this)
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return true;
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return false;
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};
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assert(HasConnectingEdge() && "No edge connects the parent to us!");
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}
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}
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#endif
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bool LazyCallGraph::RefSCC::isDescendantOf(const RefSCC &C) const {
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// Walk up the parents of this SCC and verify that we eventually find C.
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SmallVector<const RefSCC *, 4> AncestorWorklist;
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AncestorWorklist.push_back(this);
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do {
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const RefSCC *AncestorC = AncestorWorklist.pop_back_val();
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if (AncestorC->isChildOf(C))
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return true;
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for (const RefSCC *ParentC : AncestorC->Parents)
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AncestorWorklist.push_back(ParentC);
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} while (!AncestorWorklist.empty());
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return false;
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}
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/// Generic helper that updates a postorder sequence of SCCs for a potentially
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/// cycle-introducing edge insertion.
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///
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/// A postorder sequence of SCCs of a directed graph has one fundamental
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/// property: all deges in the DAG of SCCs point "up" the sequence. That is,
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/// all edges in the SCC DAG point to prior SCCs in the sequence.
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///
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/// This routine both updates a postorder sequence and uses that sequence to
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/// compute the set of SCCs connected into a cycle. It should only be called to
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/// insert a "downward" edge which will require changing the sequence to
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/// restore it to a postorder.
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///
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/// When inserting an edge from an earlier SCC to a later SCC in some postorder
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/// sequence, all of the SCCs which may be impacted are in the closed range of
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/// those two within the postorder sequence. The algorithm used here to restore
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/// the state is as follows:
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///
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/// 1) Starting from the source SCC, construct a set of SCCs which reach the
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/// source SCC consisting of just the source SCC. Then scan toward the
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/// target SCC in postorder and for each SCC, if it has an edge to an SCC
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/// in the set, add it to the set. Otherwise, the source SCC is not
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/// a successor, move it in the postorder sequence to immediately before
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/// the source SCC, shifting the source SCC and all SCCs in the set one
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/// position toward the target SCC. Stop scanning after processing the
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/// target SCC.
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/// 2) If the source SCC is now past the target SCC in the postorder sequence,
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/// and thus the new edge will flow toward the start, we are done.
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/// 3) Otherwise, starting from the target SCC, walk all edges which reach an
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/// SCC between the source and the target, and add them to the set of
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/// connected SCCs, then recurse through them. Once a complete set of the
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/// SCCs the target connects to is known, hoist the remaining SCCs between
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/// the source and the target to be above the target. Note that there is no
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/// need to process the source SCC, it is already known to connect.
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/// 4) At this point, all of the SCCs in the closed range between the source
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/// SCC and the target SCC in the postorder sequence are connected,
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/// including the target SCC and the source SCC. Inserting the edge from
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/// the source SCC to the target SCC will form a cycle out of precisely
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/// these SCCs. Thus we can merge all of the SCCs in this closed range into
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/// a single SCC.
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///
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/// This process has various important properties:
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/// - Only mutates the SCCs when adding the edge actually changes the SCC
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/// structure.
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/// - Never mutates SCCs which are unaffected by the change.
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/// - Updates the postorder sequence to correctly satisfy the postorder
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/// constraint after the edge is inserted.
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/// - Only reorders SCCs in the closed postorder sequence from the source to
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/// the target, so easy to bound how much has changed even in the ordering.
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/// - Big-O is the number of edges in the closed postorder range of SCCs from
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/// source to target.
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///
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/// This helper routine, in addition to updating the postorder sequence itself
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/// will also update a map from SCCs to indices within that sequecne.
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///
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/// The sequence and the map must operate on pointers to the SCC type.
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///
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/// Two callbacks must be provided. The first computes the subset of SCCs in
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/// the postorder closed range from the source to the target which connect to
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/// the source SCC via some (transitive) set of edges. The second computes the
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/// subset of the same range which the target SCC connects to via some
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/// (transitive) set of edges. Both callbacks should populate the set argument
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/// provided.
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template <typename SCCT, typename PostorderSequenceT, typename SCCIndexMapT,
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typename ComputeSourceConnectedSetCallableT,
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typename ComputeTargetConnectedSetCallableT>
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static iterator_range<typename PostorderSequenceT::iterator>
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updatePostorderSequenceForEdgeInsertion(
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SCCT &SourceSCC, SCCT &TargetSCC, PostorderSequenceT &SCCs,
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SCCIndexMapT &SCCIndices,
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ComputeSourceConnectedSetCallableT ComputeSourceConnectedSet,
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ComputeTargetConnectedSetCallableT ComputeTargetConnectedSet) {
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int SourceIdx = SCCIndices[&SourceSCC];
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int TargetIdx = SCCIndices[&TargetSCC];
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assert(SourceIdx < TargetIdx && "Cannot have equal indices here!");
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SmallPtrSet<SCCT *, 4> ConnectedSet;
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// Compute the SCCs which (transitively) reach the source.
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ComputeSourceConnectedSet(ConnectedSet);
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// Partition the SCCs in this part of the port-order sequence so only SCCs
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// connecting to the source remain between it and the target. This is
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// a benign partition as it preserves postorder.
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auto SourceI = std::stable_partition(
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SCCs.begin() + SourceIdx, SCCs.begin() + TargetIdx + 1,
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[&ConnectedSet](SCCT *C) { return !ConnectedSet.count(C); });
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for (int i = SourceIdx, e = TargetIdx + 1; i < e; ++i)
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SCCIndices.find(SCCs[i])->second = i;
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// If the target doesn't connect to the source, then we've corrected the
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// post-order and there are no cycles formed.
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if (!ConnectedSet.count(&TargetSCC)) {
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assert(SourceI > (SCCs.begin() + SourceIdx) &&
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"Must have moved the source to fix the post-order.");
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assert(*std::prev(SourceI) == &TargetSCC &&
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"Last SCC to move should have bene the target.");
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// Return an empty range at the target SCC indicating there is nothing to
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// merge.
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return make_range(std::prev(SourceI), std::prev(SourceI));
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}
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assert(SCCs[TargetIdx] == &TargetSCC &&
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"Should not have moved target if connected!");
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SourceIdx = SourceI - SCCs.begin();
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assert(SCCs[SourceIdx] == &SourceSCC &&
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"Bad updated index computation for the source SCC!");
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// See whether there are any remaining intervening SCCs between the source
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// and target. If so we need to make sure they all are reachable form the
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// target.
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if (SourceIdx + 1 < TargetIdx) {
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ConnectedSet.clear();
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ComputeTargetConnectedSet(ConnectedSet);
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// Partition SCCs so that only SCCs reached from the target remain between
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// the source and the target. This preserves postorder.
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auto TargetI = std::stable_partition(
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SCCs.begin() + SourceIdx + 1, SCCs.begin() + TargetIdx + 1,
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[&ConnectedSet](SCCT *C) { return ConnectedSet.count(C); });
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for (int i = SourceIdx + 1, e = TargetIdx + 1; i < e; ++i)
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SCCIndices.find(SCCs[i])->second = i;
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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();
|
|
}
|