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+//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/AbstractCallSite.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Implementations of the CallGraph class methods.
+//
+
+CallGraph::CallGraph(Module &M)
+ : M(M), ExternalCallingNode(getOrInsertFunction(nullptr)),
+ CallsExternalNode(std::make_unique<CallGraphNode>(this, nullptr)) {
+ // Add every interesting function to the call graph.
+ for (Function &F : M)
+ if (!isDbgInfoIntrinsic(F.getIntrinsicID()))
+ addToCallGraph(&F);
+}
+
+CallGraph::CallGraph(CallGraph &&Arg)
+ : M(Arg.M), FunctionMap(std::move(Arg.FunctionMap)),
+ ExternalCallingNode(Arg.ExternalCallingNode),
+ CallsExternalNode(std::move(Arg.CallsExternalNode)) {
+ Arg.FunctionMap.clear();
+ Arg.ExternalCallingNode = nullptr;
+
+ // Update parent CG for all call graph's nodes.
+ CallsExternalNode->CG = this;
+ for (auto &P : FunctionMap)
+ P.second->CG = this;
+}
+
+CallGraph::~CallGraph() {
+ // CallsExternalNode is not in the function map, delete it explicitly.
+ if (CallsExternalNode)
+ CallsExternalNode->allReferencesDropped();
+
+// Reset all node's use counts to zero before deleting them to prevent an
+// assertion from firing.
+#ifndef NDEBUG
+ for (auto &I : FunctionMap)
+ I.second->allReferencesDropped();
+#endif
+}
+
+bool CallGraph::invalidate(Module &, const PreservedAnalyses &PA,
+ ModuleAnalysisManager::Invalidator &) {
+ // Check whether the analysis, all analyses on functions, or the function's
+ // CFG have been preserved.
+ auto PAC = PA.getChecker<CallGraphAnalysis>();
+ return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>());
+}
+
+void CallGraph::addToCallGraph(Function *F) {
+ CallGraphNode *Node = getOrInsertFunction(F);
+
+ // If this function has external linkage or has its address taken and
+ // it is not a callback, then anything could call it.
+ if (!F->hasLocalLinkage() ||
+ F->hasAddressTaken(nullptr, /*IgnoreCallbackUses=*/true,
+ /* IgnoreAssumeLikeCalls */ true,
+ /* IgnoreLLVMUsed */ false))
+ ExternalCallingNode->addCalledFunction(nullptr, Node);
+
+ populateCallGraphNode(Node);
+}
+
+void CallGraph::populateCallGraphNode(CallGraphNode *Node) {
+ Function *F = Node->getFunction();
+
+ // If this function is not defined in this translation unit, it could call
+ // anything.
+ if (F->isDeclaration() && !F->hasFnAttribute(Attribute::NoCallback))
+ Node->addCalledFunction(nullptr, CallsExternalNode.get());
+
+ // Look for calls by this function.
+ for (BasicBlock &BB : *F)
+ for (Instruction &I : BB) {
+ if (auto *Call = dyn_cast<CallBase>(&I)) {
+ const Function *Callee = Call->getCalledFunction();
+ if (!Callee)
+ Node->addCalledFunction(Call, CallsExternalNode.get());
+ else if (!isDbgInfoIntrinsic(Callee->getIntrinsicID()))
+ Node->addCalledFunction(Call, getOrInsertFunction(Callee));
+
+ // Add reference to callback functions.
+ forEachCallbackFunction(*Call, [=](Function *CB) {
+ Node->addCalledFunction(nullptr, getOrInsertFunction(CB));
+ });
+ }
+ }
+}
+
+void CallGraph::print(raw_ostream &OS) const {
+ // Print in a deterministic order by sorting CallGraphNodes by name. We do
+ // this here to avoid slowing down the non-printing fast path.
+
+ SmallVector<CallGraphNode *, 16> Nodes;
+ Nodes.reserve(FunctionMap.size());
+
+ for (const auto &I : *this)
+ Nodes.push_back(I.second.get());
+
+ llvm::sort(Nodes, [](CallGraphNode *LHS, CallGraphNode *RHS) {
+ if (Function *LF = LHS->getFunction())
+ if (Function *RF = RHS->getFunction())
+ return LF->getName() < RF->getName();
+
+ return RHS->getFunction() != nullptr;
+ });
+
+ for (CallGraphNode *CN : Nodes)
+ CN->print(OS);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void CallGraph::dump() const { print(dbgs()); }
+#endif
+
+void CallGraph::ReplaceExternalCallEdge(CallGraphNode *Old,
+ CallGraphNode *New) {
+ for (auto &CR : ExternalCallingNode->CalledFunctions)
+ if (CR.second == Old) {
+ CR.second->DropRef();
+ CR.second = New;
+ CR.second->AddRef();
+ }
+}
+
+// removeFunctionFromModule - Unlink the function from this module, returning
+// it. Because this removes the function from the module, the call graph node
+// is destroyed. This is only valid if the function does not call any other
+// functions (ie, there are no edges in it's CGN). The easiest way to do this
+// is to dropAllReferences before calling this.
+//
+Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
+ assert(CGN->empty() && "Cannot remove function from call "
+ "graph if it references other functions!");
+ Function *F = CGN->getFunction(); // Get the function for the call graph node
+ FunctionMap.erase(F); // Remove the call graph node from the map
+
+ M.getFunctionList().remove(F);
+ return F;
+}
+
+// getOrInsertFunction - This method is identical to calling operator[], but
+// it will insert a new CallGraphNode for the specified function if one does
+// not already exist.
+CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
+ auto &CGN = FunctionMap[F];
+ if (CGN)
+ return CGN.get();
+
+ assert((!F || F->getParent() == &M) && "Function not in current module!");
+ CGN = std::make_unique<CallGraphNode>(this, const_cast<Function *>(F));
+ return CGN.get();
+}
+
+//===----------------------------------------------------------------------===//
+// Implementations of the CallGraphNode class methods.
+//
+
+void CallGraphNode::print(raw_ostream &OS) const {
+ if (Function *F = getFunction())
+ OS << "Call graph node for function: '" << F->getName() << "'";
+ else
+ OS << "Call graph node <<null function>>";
+
+ OS << "<<" << this << ">> #uses=" << getNumReferences() << '\n';
+
+ for (const auto &I : *this) {
+ OS << " CS<" << I.first << "> calls ";
+ if (Function *FI = I.second->getFunction())
+ OS << "function '" << FI->getName() <<"'\n";
+ else
+ OS << "external node\n";
+ }
+ OS << '\n';
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void CallGraphNode::dump() const { print(dbgs()); }
+#endif
+
+/// removeCallEdgeFor - This method removes the edge in the node for the
+/// specified call site. Note that this method takes linear time, so it
+/// should be used sparingly.
+void CallGraphNode::removeCallEdgeFor(CallBase &Call) {
+ for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
+ assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
+ if (I->first && *I->first == &Call) {
+ I->second->DropRef();
+ *I = CalledFunctions.back();
+ CalledFunctions.pop_back();
+
+ // Remove all references to callback functions if there are any.
+ forEachCallbackFunction(Call, [=](Function *CB) {
+ removeOneAbstractEdgeTo(CG->getOrInsertFunction(CB));
+ });
+ return;
+ }
+ }
+}
+
+// removeAnyCallEdgeTo - This method removes any call edges from this node to
+// the specified callee function. This takes more time to execute than
+// removeCallEdgeTo, so it should not be used unless necessary.
+void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
+ for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
+ if (CalledFunctions[i].second == Callee) {
+ Callee->DropRef();
+ CalledFunctions[i] = CalledFunctions.back();
+ CalledFunctions.pop_back();
+ --i; --e;
+ }
+}
+
+/// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
+/// from this node to the specified callee function.
+void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
+ for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
+ assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
+ CallRecord &CR = *I;
+ if (CR.second == Callee && !CR.first) {
+ Callee->DropRef();
+ *I = CalledFunctions.back();
+ CalledFunctions.pop_back();
+ return;
+ }
+ }
+}
+
+/// replaceCallEdge - This method replaces the edge in the node for the
+/// specified call site with a new one. Note that this method takes linear
+/// time, so it should be used sparingly.
+void CallGraphNode::replaceCallEdge(CallBase &Call, CallBase &NewCall,
+ CallGraphNode *NewNode) {
+ for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
+ assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
+ if (I->first && *I->first == &Call) {
+ I->second->DropRef();
+ I->first = &NewCall;
+ I->second = NewNode;
+ NewNode->AddRef();
+
+ // Refresh callback references. Do not resize CalledFunctions if the
+ // number of callbacks is the same for new and old call sites.
+ SmallVector<CallGraphNode *, 4u> OldCBs;
+ SmallVector<CallGraphNode *, 4u> NewCBs;
+ forEachCallbackFunction(Call, [this, &OldCBs](Function *CB) {
+ OldCBs.push_back(CG->getOrInsertFunction(CB));
+ });
+ forEachCallbackFunction(NewCall, [this, &NewCBs](Function *CB) {
+ NewCBs.push_back(CG->getOrInsertFunction(CB));
+ });
+ if (OldCBs.size() == NewCBs.size()) {
+ for (unsigned N = 0; N < OldCBs.size(); ++N) {
+ CallGraphNode *OldNode = OldCBs[N];
+ CallGraphNode *NewNode = NewCBs[N];
+ for (auto J = CalledFunctions.begin();; ++J) {
+ assert(J != CalledFunctions.end() &&
+ "Cannot find callsite to update!");
+ if (!J->first && J->second == OldNode) {
+ J->second = NewNode;
+ OldNode->DropRef();
+ NewNode->AddRef();
+ break;
+ }
+ }
+ }
+ } else {
+ for (auto *CGN : OldCBs)
+ removeOneAbstractEdgeTo(CGN);
+ for (auto *CGN : NewCBs)
+ addCalledFunction(nullptr, CGN);
+ }
+ return;
+ }
+ }
+}
+
+// Provide an explicit template instantiation for the static ID.
+AnalysisKey CallGraphAnalysis::Key;
+
+PreservedAnalyses CallGraphPrinterPass::run(Module &M,
+ ModuleAnalysisManager &AM) {
+ AM.getResult<CallGraphAnalysis>(M).print(OS);
+ return PreservedAnalyses::all();
+}
+
+PreservedAnalyses CallGraphSCCsPrinterPass::run(Module &M,
+ ModuleAnalysisManager &AM) {
+ auto &CG = AM.getResult<CallGraphAnalysis>(M);
+ unsigned sccNum = 0;
+ OS << "SCCs for the program in PostOrder:";
+ for (scc_iterator<CallGraph *> SCCI = scc_begin(&CG); !SCCI.isAtEnd();
+ ++SCCI) {
+ const std::vector<CallGraphNode *> &nextSCC = *SCCI;
+ OS << "\nSCC #" << ++sccNum << ": ";
+ bool First = true;
+ for (std::vector<CallGraphNode *>::const_iterator I = nextSCC.begin(),
+ E = nextSCC.end();
+ I != E; ++I) {
+ if (First)
+ First = false;
+ else
+ OS << ", ";
+ OS << ((*I)->getFunction() ? (*I)->getFunction()->getName()
+ : "external node");
+ }
+
+ if (nextSCC.size() == 1 && SCCI.hasCycle())
+ OS << " (Has self-loop).";
+ }
+ OS << "\n";
+ return PreservedAnalyses::all();
+}
+
+//===----------------------------------------------------------------------===//
+// Out-of-line definitions of CallGraphAnalysis class members.
+//
+
+//===----------------------------------------------------------------------===//
+// Implementations of the CallGraphWrapperPass class methods.
+//
+
+CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
+ initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
+}
+
+CallGraphWrapperPass::~CallGraphWrapperPass() = default;
+
+void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+}
+
+bool CallGraphWrapperPass::runOnModule(Module &M) {
+ // All the real work is done in the constructor for the CallGraph.
+ G.reset(new CallGraph(M));
+ return false;
+}
+
+INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
+ false, true)
+
+char CallGraphWrapperPass::ID = 0;
+
+void CallGraphWrapperPass::releaseMemory() { G.reset(); }
+
+void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
+ if (!G) {
+ OS << "No call graph has been built!\n";
+ return;
+ }
+
+ // Just delegate.
+ G->print(OS);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD
+void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
+#endif