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() {
36 // CallsExternalNode is not in the function map, delete it explicitly.
37 if (CallsExternalNode)
38 CallsExternalNode->allReferencesDropped();
40 // Reset all node's use counts to zero before deleting them to prevent an
41 // assertion from firing.
43 for (auto &I : FunctionMap)
44 I.second->allReferencesDropped();
48 void CallGraph::addToCallGraph(Function *F) {
49 CallGraphNode *Node = getOrInsertFunction(F);
51 // If this function has external linkage, anything could call it.
52 if (!F->hasLocalLinkage()) {
53 ExternalCallingNode->addCalledFunction(CallSite(), Node);
55 // Found the entry point?
56 if (F->getName() == "main") {
57 if (Root) // Found multiple external mains? Don't pick one.
58 Root = ExternalCallingNode;
60 Root = Node; // Found a main, keep track of it!
64 // If this function has its address taken, anything could call it.
65 if (F->hasAddressTaken())
66 ExternalCallingNode->addCalledFunction(CallSite(), Node);
68 // If this function is not defined in this translation unit, it could call
70 if (F->isDeclaration() && !F->isIntrinsic())
71 Node->addCalledFunction(CallSite(), CallsExternalNode.get());
73 // Look for calls by this function.
74 for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
75 for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;
77 CallSite CS(cast<Value>(II));
79 const Function *Callee = CS.getCalledFunction();
80 if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
81 // Indirect calls of intrinsics are not allowed so no need to check.
82 // We can be more precise here by using TargetArg returned by
84 Node->addCalledFunction(CS, CallsExternalNode.get());
85 else if (!Callee->isIntrinsic())
86 Node->addCalledFunction(CS, getOrInsertFunction(Callee));
91 void CallGraph::print(raw_ostream &OS) const {
92 OS << "CallGraph Root is: ";
93 if (Function *F = Root->getFunction())
94 OS << F->getName() << "\n";
96 OS << "<<null function: 0x" << Root << ">>\n";
99 // Print in a deterministic order by sorting CallGraphNodes by name. We do
100 // this here to avoid slowing down the non-printing fast path.
102 SmallVector<CallGraphNode *, 16> Nodes;
103 Nodes.reserve(FunctionMap.size());
105 for (auto I = begin(), E = end(); I != E; ++I)
106 Nodes.push_back(I->second.get());
108 std::sort(Nodes.begin(), Nodes.end(),
109 [](CallGraphNode *LHS, CallGraphNode *RHS) {
110 if (Function *LF = LHS->getFunction())
111 if (Function *RF = RHS->getFunction())
112 return LF->getName() < RF->getName();
114 return RHS->getFunction() != nullptr;
117 for (CallGraphNode *CN : Nodes)
121 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
122 void CallGraph::dump() const { print(dbgs()); }
125 // removeFunctionFromModule - Unlink the function from this module, returning
126 // it. Because this removes the function from the module, the call graph node
127 // is destroyed. This is only valid if the function does not call any other
128 // functions (ie, there are no edges in it's CGN). The easiest way to do this
129 // is to dropAllReferences before calling this.
131 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
132 assert(CGN->empty() && "Cannot remove function from call "
133 "graph if it references other functions!");
134 Function *F = CGN->getFunction(); // Get the function for the call graph node
135 FunctionMap.erase(F); // Remove the call graph node from the map
137 M.getFunctionList().remove(F);
141 /// spliceFunction - Replace the function represented by this node by another.
142 /// This does not rescan the body of the function, so it is suitable when
143 /// splicing the body of the old function to the new while also updating all
144 /// callers from old to new.
146 void CallGraph::spliceFunction(const Function *From, const Function *To) {
147 assert(FunctionMap.count(From) && "No CallGraphNode for function!");
148 assert(!FunctionMap.count(To) &&
149 "Pointing CallGraphNode at a function that already exists");
150 FunctionMapTy::iterator I = FunctionMap.find(From);
151 I->second->F = const_cast<Function*>(To);
152 FunctionMap[To] = std::move(I->second);
153 FunctionMap.erase(I);
156 // getOrInsertFunction - This method is identical to calling operator[], but
157 // it will insert a new CallGraphNode for the specified function if one does
158 // not already exist.
159 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
160 auto &CGN = FunctionMap[F];
164 assert((!F || F->getParent() == &M) && "Function not in current module!");
165 CGN = llvm::make_unique<CallGraphNode>(const_cast<Function *>(F));
169 //===----------------------------------------------------------------------===//
170 // Implementations of the CallGraphNode class methods.
173 void CallGraphNode::print(raw_ostream &OS) const {
174 if (Function *F = getFunction())
175 OS << "Call graph node for function: '" << F->getName() << "'";
177 OS << "Call graph node <<null function>>";
179 OS << "<<" << this << ">> #uses=" << getNumReferences() << '\n';
181 for (const_iterator I = begin(), E = end(); I != E; ++I) {
182 OS << " CS<" << I->first << "> calls ";
183 if (Function *FI = I->second->getFunction())
184 OS << "function '" << FI->getName() <<"'\n";
186 OS << "external node\n";
191 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
192 void CallGraphNode::dump() const { print(dbgs()); }
195 /// removeCallEdgeFor - This method removes the edge in the node for the
196 /// specified call site. Note that this method takes linear time, so it
197 /// should be used sparingly.
198 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
199 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
200 assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
201 if (I->first == CS.getInstruction()) {
202 I->second->DropRef();
203 *I = CalledFunctions.back();
204 CalledFunctions.pop_back();
210 // removeAnyCallEdgeTo - This method removes any call edges from this node to
211 // the specified callee function. This takes more time to execute than
212 // removeCallEdgeTo, so it should not be used unless necessary.
213 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
214 for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
215 if (CalledFunctions[i].second == Callee) {
217 CalledFunctions[i] = CalledFunctions.back();
218 CalledFunctions.pop_back();
223 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
224 /// from this node to the specified callee function.
225 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
226 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
227 assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
229 if (CR.second == Callee && CR.first == nullptr) {
231 *I = CalledFunctions.back();
232 CalledFunctions.pop_back();
238 /// replaceCallEdge - This method replaces the edge in the node for the
239 /// specified call site with a new one. Note that this method takes linear
240 /// time, so it should be used sparingly.
241 void CallGraphNode::replaceCallEdge(CallSite CS,
242 CallSite NewCS, CallGraphNode *NewNode){
243 for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
244 assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
245 if (I->first == CS.getInstruction()) {
246 I->second->DropRef();
247 I->first = NewCS.getInstruction();
255 //===----------------------------------------------------------------------===//
256 // Implementations of the CallGraphWrapperPass class methods.
259 CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
260 initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
263 CallGraphWrapperPass::~CallGraphWrapperPass() {}
265 void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
266 AU.setPreservesAll();
269 bool CallGraphWrapperPass::runOnModule(Module &M) {
270 // All the real work is done in the constructor for the CallGraph.
271 G.reset(new CallGraph(M));
275 INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
278 char CallGraphWrapperPass::ID = 0;
280 void CallGraphWrapperPass::releaseMemory() { G.reset(); }
282 void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
284 OS << "No call graph has been built!\n";
292 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
293 void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }