1 //===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===//
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 //===----------------------------------------------------------------------===//
11 /// This file provides interfaces used to build and manipulate a call graph,
12 /// which is a very useful tool for interprocedural optimization.
14 /// Every function in a module is represented as a node in the call graph. The
15 /// callgraph node keeps track of which functions are called by the function
16 /// corresponding to the node.
18 /// A call graph may contain nodes where the function that they correspond to
19 /// is null. These 'external' nodes are used to represent control flow that is
20 /// not represented (or analyzable) in the module. In particular, this
21 /// analysis builds one external node such that:
22 /// 1. All functions in the module without internal linkage will have edges
23 /// from this external node, indicating that they could be called by
24 /// functions outside of the module.
25 /// 2. All functions whose address is used for something more than a direct
26 /// call, for example being stored into a memory location will also have
27 /// an edge from this external node. Since they may be called by an
28 /// unknown caller later, they must be tracked as such.
30 /// There is a second external node added for calls that leave this module.
31 /// Functions have a call edge to the external node iff:
32 /// 1. The function is external, reflecting the fact that they could call
33 /// anything without internal linkage or that has its address taken.
34 /// 2. The function contains an indirect function call.
36 /// As an extension in the future, there may be multiple nodes with a null
37 /// function. These will be used when we can prove (through pointer analysis)
38 /// that an indirect call site can call only a specific set of functions.
40 /// Because of these properties, the CallGraph captures a conservative superset
41 /// of all of the caller-callee relationships, which is useful for
44 //===----------------------------------------------------------------------===//
46 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
47 #define LLVM_ANALYSIS_CALLGRAPH_H
49 #include "llvm/ADT/GraphTraits.h"
50 #include "llvm/ADT/STLExtras.h"
51 #include "llvm/IR/CallSite.h"
52 #include "llvm/IR/Function.h"
53 #include "llvm/IR/Intrinsics.h"
54 #include "llvm/IR/PassManager.h"
55 #include "llvm/IR/ValueHandle.h"
56 #include "llvm/Pass.h"
69 /// \brief The basic data container for the call graph of a \c Module of IR.
71 /// This class exposes both the interface to the call graph for a module of IR.
73 /// The core call graph itself can also be updated to reflect changes to the IR.
78 std::map<const Function *, std::unique_ptr<CallGraphNode>>;
80 /// \brief A map from \c Function* to \c CallGraphNode*.
81 FunctionMapTy FunctionMap;
83 /// \brief This node has edges to all external functions and those internal
84 /// functions that have their address taken.
85 CallGraphNode *ExternalCallingNode;
87 /// \brief This node has edges to it from all functions making indirect calls
88 /// or calling an external function.
89 std::unique_ptr<CallGraphNode> CallsExternalNode;
91 /// \brief Replace the function represented by this node by another.
93 /// This does not rescan the body of the function, so it is suitable when
94 /// splicing the body of one function to another while also updating all
95 /// callers from the old function to the new.
96 void spliceFunction(const Function *From, const Function *To);
98 /// \brief Add a function to the call graph, and link the node to all of the
99 /// functions that it calls.
100 void addToCallGraph(Function *F);
103 explicit CallGraph(Module &M);
104 CallGraph(CallGraph &&Arg);
107 void print(raw_ostream &OS) const;
110 using iterator = FunctionMapTy::iterator;
111 using const_iterator = FunctionMapTy::const_iterator;
113 /// \brief Returns the module the call graph corresponds to.
114 Module &getModule() const { return M; }
116 inline iterator begin() { return FunctionMap.begin(); }
117 inline iterator end() { return FunctionMap.end(); }
118 inline const_iterator begin() const { return FunctionMap.begin(); }
119 inline const_iterator end() const { return FunctionMap.end(); }
121 /// \brief Returns the call graph node for the provided function.
122 inline const CallGraphNode *operator[](const Function *F) const {
123 const_iterator I = FunctionMap.find(F);
124 assert(I != FunctionMap.end() && "Function not in callgraph!");
125 return I->second.get();
128 /// \brief Returns the call graph node for the provided function.
129 inline CallGraphNode *operator[](const Function *F) {
130 const_iterator I = FunctionMap.find(F);
131 assert(I != FunctionMap.end() && "Function not in callgraph!");
132 return I->second.get();
135 /// \brief Returns the \c CallGraphNode which is used to represent
136 /// undetermined calls into the callgraph.
137 CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
139 CallGraphNode *getCallsExternalNode() const {
140 return CallsExternalNode.get();
143 //===---------------------------------------------------------------------
144 // Functions to keep a call graph up to date with a function that has been
148 /// \brief Unlink the function from this module, returning it.
150 /// Because this removes the function from the module, the call graph node is
151 /// destroyed. This is only valid if the function does not call any other
152 /// functions (ie, there are no edges in it's CGN). The easiest way to do
153 /// this is to dropAllReferences before calling this.
154 Function *removeFunctionFromModule(CallGraphNode *CGN);
156 /// \brief Similar to operator[], but this will insert a new CallGraphNode for
157 /// \c F if one does not already exist.
158 CallGraphNode *getOrInsertFunction(const Function *F);
161 /// \brief A node in the call graph for a module.
163 /// Typically represents a function in the call graph. There are also special
164 /// "null" nodes used to represent theoretical entries in the call graph.
165 class CallGraphNode {
167 /// \brief A pair of the calling instruction (a call or invoke)
168 /// and the call graph node being called.
169 using CallRecord = std::pair<WeakTrackingVH, CallGraphNode *>;
172 using CalledFunctionsVector = std::vector<CallRecord>;
174 /// \brief Creates a node for the specified function.
175 inline CallGraphNode(Function *F) : F(F) {}
177 CallGraphNode(const CallGraphNode &) = delete;
178 CallGraphNode &operator=(const CallGraphNode &) = delete;
181 assert(NumReferences == 0 && "Node deleted while references remain");
184 using iterator = std::vector<CallRecord>::iterator;
185 using const_iterator = std::vector<CallRecord>::const_iterator;
187 /// \brief Returns the function that this call graph node represents.
188 Function *getFunction() const { return F; }
190 inline iterator begin() { return CalledFunctions.begin(); }
191 inline iterator end() { return CalledFunctions.end(); }
192 inline const_iterator begin() const { return CalledFunctions.begin(); }
193 inline const_iterator end() const { return CalledFunctions.end(); }
194 inline bool empty() const { return CalledFunctions.empty(); }
195 inline unsigned size() const { return (unsigned)CalledFunctions.size(); }
197 /// \brief Returns the number of other CallGraphNodes in this CallGraph that
198 /// reference this node in their callee list.
199 unsigned getNumReferences() const { return NumReferences; }
201 /// \brief Returns the i'th called function.
202 CallGraphNode *operator[](unsigned i) const {
203 assert(i < CalledFunctions.size() && "Invalid index");
204 return CalledFunctions[i].second;
207 /// \brief Print out this call graph node.
209 void print(raw_ostream &OS) const;
211 //===---------------------------------------------------------------------
212 // Methods to keep a call graph up to date with a function that has been
216 /// \brief Removes all edges from this CallGraphNode to any functions it
218 void removeAllCalledFunctions() {
219 while (!CalledFunctions.empty()) {
220 CalledFunctions.back().second->DropRef();
221 CalledFunctions.pop_back();
225 /// \brief Moves all the callee information from N to this node.
226 void stealCalledFunctionsFrom(CallGraphNode *N) {
227 assert(CalledFunctions.empty() &&
228 "Cannot steal callsite information if I already have some");
229 std::swap(CalledFunctions, N->CalledFunctions);
232 /// \brief Adds a function to the list of functions called by this one.
233 void addCalledFunction(CallSite CS, CallGraphNode *M) {
234 assert(!CS.getInstruction() || !CS.getCalledFunction() ||
235 !CS.getCalledFunction()->isIntrinsic() ||
236 !Intrinsic::isLeaf(CS.getCalledFunction()->getIntrinsicID()));
237 CalledFunctions.emplace_back(CS.getInstruction(), M);
241 void removeCallEdge(iterator I) {
242 I->second->DropRef();
243 *I = CalledFunctions.back();
244 CalledFunctions.pop_back();
247 /// \brief Removes the edge in the node for the specified call site.
249 /// Note that this method takes linear time, so it should be used sparingly.
250 void removeCallEdgeFor(CallSite CS);
252 /// \brief Removes all call edges from this node to the specified callee
255 /// This takes more time to execute than removeCallEdgeTo, so it should not
256 /// be used unless necessary.
257 void removeAnyCallEdgeTo(CallGraphNode *Callee);
259 /// \brief Removes one edge associated with a null callsite from this node to
260 /// the specified callee function.
261 void removeOneAbstractEdgeTo(CallGraphNode *Callee);
263 /// \brief Replaces the edge in the node for the specified call site with a
266 /// Note that this method takes linear time, so it should be used sparingly.
267 void replaceCallEdge(CallSite CS, CallSite NewCS, CallGraphNode *NewNode);
270 friend class CallGraph;
274 std::vector<CallRecord> CalledFunctions;
276 /// \brief The number of times that this CallGraphNode occurs in the
277 /// CalledFunctions array of this or other CallGraphNodes.
278 unsigned NumReferences = 0;
280 void DropRef() { --NumReferences; }
281 void AddRef() { ++NumReferences; }
283 /// \brief A special function that should only be used by the CallGraph class.
284 void allReferencesDropped() { NumReferences = 0; }
287 /// \brief An analysis pass to compute the \c CallGraph for a \c Module.
289 /// This class implements the concept of an analysis pass used by the \c
290 /// ModuleAnalysisManager to run an analysis over a module and cache the
292 class CallGraphAnalysis : public AnalysisInfoMixin<CallGraphAnalysis> {
293 friend AnalysisInfoMixin<CallGraphAnalysis>;
295 static AnalysisKey Key;
298 /// \brief A formulaic type to inform clients of the result type.
299 using Result = CallGraph;
301 /// \brief Compute the \c CallGraph for the module \c M.
303 /// The real work here is done in the \c CallGraph constructor.
304 CallGraph run(Module &M, ModuleAnalysisManager &) { return CallGraph(M); }
307 /// \brief Printer pass for the \c CallGraphAnalysis results.
308 class CallGraphPrinterPass : public PassInfoMixin<CallGraphPrinterPass> {
312 explicit CallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
314 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
317 /// \brief The \c ModulePass which wraps up a \c CallGraph and the logic to
320 /// This class exposes both the interface to the call graph container and the
321 /// module pass which runs over a module of IR and produces the call graph. The
322 /// call graph interface is entirelly a wrapper around a \c CallGraph object
323 /// which is stored internally for each module.
324 class CallGraphWrapperPass : public ModulePass {
325 std::unique_ptr<CallGraph> G;
328 static char ID; // Class identification, replacement for typeinfo
330 CallGraphWrapperPass();
331 ~CallGraphWrapperPass() override;
333 /// \brief The internal \c CallGraph around which the rest of this interface
335 const CallGraph &getCallGraph() const { return *G; }
336 CallGraph &getCallGraph() { return *G; }
338 using iterator = CallGraph::iterator;
339 using const_iterator = CallGraph::const_iterator;
341 /// \brief Returns the module the call graph corresponds to.
342 Module &getModule() const { return G->getModule(); }
344 inline iterator begin() { return G->begin(); }
345 inline iterator end() { return G->end(); }
346 inline const_iterator begin() const { return G->begin(); }
347 inline const_iterator end() const { return G->end(); }
349 /// \brief Returns the call graph node for the provided function.
350 inline const CallGraphNode *operator[](const Function *F) const {
354 /// \brief Returns the call graph node for the provided function.
355 inline CallGraphNode *operator[](const Function *F) { return (*G)[F]; }
357 /// \brief Returns the \c CallGraphNode which is used to represent
358 /// undetermined calls into the callgraph.
359 CallGraphNode *getExternalCallingNode() const {
360 return G->getExternalCallingNode();
363 CallGraphNode *getCallsExternalNode() const {
364 return G->getCallsExternalNode();
367 //===---------------------------------------------------------------------
368 // Functions to keep a call graph up to date with a function that has been
372 /// \brief Unlink the function from this module, returning it.
374 /// Because this removes the function from the module, the call graph node is
375 /// destroyed. This is only valid if the function does not call any other
376 /// functions (ie, there are no edges in it's CGN). The easiest way to do
377 /// this is to dropAllReferences before calling this.
378 Function *removeFunctionFromModule(CallGraphNode *CGN) {
379 return G->removeFunctionFromModule(CGN);
382 /// \brief Similar to operator[], but this will insert a new CallGraphNode for
383 /// \c F if one does not already exist.
384 CallGraphNode *getOrInsertFunction(const Function *F) {
385 return G->getOrInsertFunction(F);
388 //===---------------------------------------------------------------------
389 // Implementation of the ModulePass interface needed here.
392 void getAnalysisUsage(AnalysisUsage &AU) const override;
393 bool runOnModule(Module &M) override;
394 void releaseMemory() override;
396 void print(raw_ostream &o, const Module *) const override;
400 //===----------------------------------------------------------------------===//
401 // GraphTraits specializations for call graphs so that they can be treated as
402 // graphs by the generic graph algorithms.
405 // Provide graph traits for tranversing call graphs using standard graph
407 template <> struct GraphTraits<CallGraphNode *> {
408 using NodeRef = CallGraphNode *;
409 using CGNPairTy = CallGraphNode::CallRecord;
411 static NodeRef getEntryNode(CallGraphNode *CGN) { return CGN; }
412 static CallGraphNode *CGNGetValue(CGNPairTy P) { return P.second; }
414 using ChildIteratorType =
415 mapped_iterator<CallGraphNode::iterator, decltype(&CGNGetValue)>;
417 static ChildIteratorType child_begin(NodeRef N) {
418 return ChildIteratorType(N->begin(), &CGNGetValue);
421 static ChildIteratorType child_end(NodeRef N) {
422 return ChildIteratorType(N->end(), &CGNGetValue);
426 template <> struct GraphTraits<const CallGraphNode *> {
427 using NodeRef = const CallGraphNode *;
428 using CGNPairTy = CallGraphNode::CallRecord;
430 static NodeRef getEntryNode(const CallGraphNode *CGN) { return CGN; }
431 static const CallGraphNode *CGNGetValue(CGNPairTy P) { return P.second; }
433 using ChildIteratorType =
434 mapped_iterator<CallGraphNode::const_iterator, decltype(&CGNGetValue)>;
436 static ChildIteratorType child_begin(NodeRef N) {
437 return ChildIteratorType(N->begin(), &CGNGetValue);
440 static ChildIteratorType child_end(NodeRef N) {
441 return ChildIteratorType(N->end(), &CGNGetValue);
446 struct GraphTraits<CallGraph *> : public GraphTraits<CallGraphNode *> {
448 std::pair<const Function *const, std::unique_ptr<CallGraphNode>>;
450 static NodeRef getEntryNode(CallGraph *CGN) {
451 return CGN->getExternalCallingNode(); // Start at the external node!
454 static CallGraphNode *CGGetValuePtr(const PairTy &P) {
455 return P.second.get();
458 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
459 using nodes_iterator =
460 mapped_iterator<CallGraph::iterator, decltype(&CGGetValuePtr)>;
462 static nodes_iterator nodes_begin(CallGraph *CG) {
463 return nodes_iterator(CG->begin(), &CGGetValuePtr);
466 static nodes_iterator nodes_end(CallGraph *CG) {
467 return nodes_iterator(CG->end(), &CGGetValuePtr);
472 struct GraphTraits<const CallGraph *> : public GraphTraits<
473 const CallGraphNode *> {
475 std::pair<const Function *const, std::unique_ptr<CallGraphNode>>;
477 static NodeRef getEntryNode(const CallGraph *CGN) {
478 return CGN->getExternalCallingNode(); // Start at the external node!
481 static const CallGraphNode *CGGetValuePtr(const PairTy &P) {
482 return P.second.get();
485 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
486 using nodes_iterator =
487 mapped_iterator<CallGraph::const_iterator, decltype(&CGGetValuePtr)>;
489 static nodes_iterator nodes_begin(const CallGraph *CG) {
490 return nodes_iterator(CG->begin(), &CGGetValuePtr);
493 static nodes_iterator nodes_end(const CallGraph *CG) {
494 return nodes_iterator(CG->end(), &CGGetValuePtr);
498 } // end namespace llvm
500 #endif // LLVM_ANALYSIS_CALLGRAPH_H