1 //===- CallGraph.cpp - Build a Module's call graph ------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Analysis/CallGraph.h"
11 #include "llvm/IR/CallSite.h"
12 #include "llvm/IR/Instructions.h"
13 #include "llvm/IR/IntrinsicInst.h"
14 #include "llvm/IR/Module.h"
15 #include "llvm/Support/Debug.h"
16 #include "llvm/Support/raw_ostream.h"
19 //===----------------------------------------------------------------------===//
20 // Implementations of the CallGraph class methods.
23 CallGraph::CallGraph(Module &M)
24 : M(M), Root(nullptr), ExternalCallingNode(getOrInsertFunction(nullptr)),
25 CallsExternalNode(llvm::make_unique<CallGraphNode>(nullptr)) {
26 // Add every function to the call graph.
30 // If we didn't find a main function, use the external call graph node
32 Root = ExternalCallingNode;
35 CallGraph::CallGraph(CallGraph &&Arg)
36 : M(Arg.M), FunctionMap(std::move(Arg.FunctionMap)), Root(Arg.Root),
37 ExternalCallingNode(Arg.ExternalCallingNode),
38 CallsExternalNode(std::move(Arg.CallsExternalNode)) {
39 Arg.FunctionMap.clear();
41 Arg.ExternalCallingNode = nullptr;
44 CallGraph::~CallGraph() {
45 // CallsExternalNode is not in the function map, delete it explicitly.
46 if (CallsExternalNode)
47 CallsExternalNode->allReferencesDropped();
49 // Reset all node's use counts to zero before deleting them to prevent an
50 // assertion from firing.
52 for (auto &I : FunctionMap)
53 I.second->allReferencesDropped();
57 void CallGraph::addToCallGraph(Function *F) {
58 CallGraphNode *Node = getOrInsertFunction(F);
60 // If this function has external linkage, anything could call it.
61 if (!F->hasLocalLinkage()) {
62 ExternalCallingNode->addCalledFunction(CallSite(), Node);
64 // Found the entry point?
65 if (F->getName() == "main") {
66 if (Root) // Found multiple external mains? Don't pick one.
67 Root = ExternalCallingNode;
69 Root = Node; // Found a main, keep track of it!
73 // If this function has its address taken, anything could call it.
74 if (F->hasAddressTaken())
75 ExternalCallingNode->addCalledFunction(CallSite(), Node);
77 // If this function is not defined in this translation unit, it could call
79 if (F->isDeclaration() && !F->isIntrinsic())
80 Node->addCalledFunction(CallSite(), CallsExternalNode.get());
82 // Look for calls by this function.
83 for (BasicBlock &BB : *F)
84 for (Instruction &I : BB) {
85 if (auto CS = CallSite(&I)) {
86 const Function *Callee = CS.getCalledFunction();
87 if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
88 // Indirect calls of intrinsics are not allowed so no need to check.
89 // We can be more precise here by using TargetArg returned by
91 Node->addCalledFunction(CS, CallsExternalNode.get());
92 else if (!Callee->isIntrinsic())
93 Node->addCalledFunction(CS, getOrInsertFunction(Callee));
98 void CallGraph::print(raw_ostream &OS) const {
99 OS << "CallGraph Root is: ";
100 if (Function *F = Root->getFunction())
101 OS << F->getName() << "\n";
103 OS << "<<null function: 0x" << Root << ">>\n";
106 // Print in a deterministic order by sorting CallGraphNodes by name. We do
107 // this here to avoid slowing down the non-printing fast path.
109 SmallVector<CallGraphNode *, 16> Nodes;
110 Nodes.reserve(FunctionMap.size());
112 for (const auto &I : *this)
113 Nodes.push_back(I.second.get());
115 std::sort(Nodes.begin(), Nodes.end(),
116 [](CallGraphNode *LHS, CallGraphNode *RHS) {
117 if (Function *LF = LHS->getFunction())
118 if (Function *RF = RHS->getFunction())
119 return LF->getName() < RF->getName();
121 return RHS->getFunction() != nullptr;
124 for (CallGraphNode *CN : Nodes)
129 void CallGraph::dump() const { print(dbgs()); }
131 // removeFunctionFromModule - Unlink the function from this module, returning
132 // it. Because this removes the function from the module, the call graph node
133 // is destroyed. This is only valid if the function does not call any other
134 // functions (ie, there are no edges in it's CGN). The easiest way to do this
135 // is to dropAllReferences before calling this.
137 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
138 assert(CGN->empty() && "Cannot remove function from call "
139 "graph if it references other functions!");
140 Function *F = CGN->getFunction(); // Get the function for the call graph node
141 FunctionMap.erase(F); // Remove the call graph node from the map
143 M.getFunctionList().remove(F);
147 /// spliceFunction - Replace the function represented by this node by another.
148 /// This does not rescan the body of the function, so it is suitable when
149 /// splicing the body of the old function to the new while also updating all
150 /// callers from old to new.
152 void CallGraph::spliceFunction(const Function *From, const Function *To) {
153 assert(FunctionMap.count(From) && "No CallGraphNode for function!");
154 assert(!FunctionMap.count(To) &&
155 "Pointing CallGraphNode at a function that already exists");
156 FunctionMapTy::iterator I = FunctionMap.find(From);
157 I->second->F = const_cast<Function*>(To);
158 FunctionMap[To] = std::move(I->second);
159 FunctionMap.erase(I);
162 // getOrInsertFunction - This method is identical to calling operator[], but
163 // it will insert a new CallGraphNode for the specified function if one does
164 // not already exist.
165 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
166 auto &CGN = FunctionMap[F];
170 assert((!F || F->getParent() == &M) && "Function not in current module!");
171 CGN = llvm::make_unique<CallGraphNode>(const_cast<Function *>(F));
175 //===----------------------------------------------------------------------===//
176 // Implementations of the CallGraphNode class methods.
179 void CallGraphNode::print(raw_ostream &OS) const {
180 if (Function *F = getFunction())
181 OS << "Call graph node for function: '" << F->getName() << "'";
183 OS << "Call graph node <<null function>>";
185 OS << "<<" << this << ">> #uses=" << getNumReferences() << '\n';
187 for (const auto &I : *this) {
188 OS << " CS<" << I.first << "> calls ";
189 if (Function *FI = I.second->getFunction())
190 OS << "function '" << FI->getName() <<"'\n";
192 OS << "external node\n";
198 void CallGraphNode::dump() const { print(dbgs()); }
200 /// removeCallEdgeFor - This method removes the edge in the node for the
201 /// specified call site. Note that this method takes linear time, so it
202 /// should be used sparingly.
203 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
204 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
205 assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
206 if (I->first == CS.getInstruction()) {
207 I->second->DropRef();
208 *I = CalledFunctions.back();
209 CalledFunctions.pop_back();
215 // removeAnyCallEdgeTo - This method removes any call edges from this node to
216 // the specified callee function. This takes more time to execute than
217 // removeCallEdgeTo, so it should not be used unless necessary.
218 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
219 for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
220 if (CalledFunctions[i].second == Callee) {
222 CalledFunctions[i] = CalledFunctions.back();
223 CalledFunctions.pop_back();
228 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
229 /// from this node to the specified callee function.
230 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
231 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
232 assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
234 if (CR.second == Callee && CR.first == nullptr) {
236 *I = CalledFunctions.back();
237 CalledFunctions.pop_back();
243 /// replaceCallEdge - This method replaces the edge in the node for the
244 /// specified call site with a new one. Note that this method takes linear
245 /// time, so it should be used sparingly.
246 void CallGraphNode::replaceCallEdge(CallSite CS,
247 CallSite NewCS, CallGraphNode *NewNode){
248 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
249 assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
250 if (I->first == CS.getInstruction()) {
251 I->second->DropRef();
252 I->first = NewCS.getInstruction();
260 // Provide an explicit template instantiation for the static ID.
261 AnalysisKey CallGraphAnalysis::Key;
263 PreservedAnalyses CallGraphPrinterPass::run(Module &M,
264 ModuleAnalysisManager &AM) {
265 AM.getResult<CallGraphAnalysis>(M).print(OS);
266 return PreservedAnalyses::all();
269 //===----------------------------------------------------------------------===//
270 // Out-of-line definitions of CallGraphAnalysis class members.
273 //===----------------------------------------------------------------------===//
274 // Implementations of the CallGraphWrapperPass class methods.
277 CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
278 initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
281 CallGraphWrapperPass::~CallGraphWrapperPass() {}
283 void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
284 AU.setPreservesAll();
287 bool CallGraphWrapperPass::runOnModule(Module &M) {
288 // All the real work is done in the constructor for the CallGraph.
289 G.reset(new CallGraph(M));
293 INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
296 char CallGraphWrapperPass::ID = 0;
298 void CallGraphWrapperPass::releaseMemory() { G.reset(); }
300 void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
302 OS << "No call graph has been built!\n";
311 void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
314 struct CallGraphPrinterLegacyPass : public ModulePass {
315 static char ID; // Pass ID, replacement for typeid
316 CallGraphPrinterLegacyPass() : ModulePass(ID) {
317 initializeCallGraphPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
320 void getAnalysisUsage(AnalysisUsage &AU) const override {
321 AU.setPreservesAll();
322 AU.addRequiredTransitive<CallGraphWrapperPass>();
324 bool runOnModule(Module &M) override {
325 getAnalysis<CallGraphWrapperPass>().print(errs(), &M);
331 char CallGraphPrinterLegacyPass::ID = 0;
333 INITIALIZE_PASS_BEGIN(CallGraphPrinterLegacyPass, "print-callgraph",
334 "Print a call graph", true, true)
335 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
336 INITIALIZE_PASS_END(CallGraphPrinterLegacyPass, "print-callgraph",
337 "Print a call graph", true, true)