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 /// The CallGraph class also attempts to figure out what the root of the
45 /// CallGraph is, which it currently does by looking for a function named
46 /// 'main'. If no function named 'main' is found, the external node is used as
47 /// the entry node, reflecting the fact that any function without internal
48 /// linkage could be called into (which is common for libraries).
50 //===----------------------------------------------------------------------===//
52 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
53 #define LLVM_ANALYSIS_CALLGRAPH_H
55 #include "llvm/ADT/GraphTraits.h"
56 #include "llvm/ADT/STLExtras.h"
57 #include "llvm/IR/CallSite.h"
58 #include "llvm/IR/Function.h"
59 #include "llvm/IR/ValueHandle.h"
60 #include "llvm/Pass.h"
61 #include "llvm/Support/IncludeFile.h"
70 /// \brief The basic data container for the call graph of a \c Module of IR.
72 /// This class exposes both the interface to the call graph for a module of IR.
74 /// The core call graph itself can also be updated to reflect changes to the IR.
78 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
80 /// \brief A map from \c Function* to \c CallGraphNode*.
81 FunctionMapTy FunctionMap;
83 /// \brief Root is root of the call graph, or the external node if a 'main'
84 /// function couldn't be found.
87 /// \brief This node has edges to all external functions and those internal
88 /// functions that have their address taken.
89 CallGraphNode *ExternalCallingNode;
91 /// \brief This node has edges to it from all functions making indirect calls
92 /// or calling an external function.
93 CallGraphNode *CallsExternalNode;
95 /// \brief Replace the function represented by this node by another.
97 /// This does not rescan the body of the function, so it is suitable when
98 /// splicing the body of one function to another while also updating all
99 /// callers from the old function to the new.
100 void spliceFunction(const Function *From, const Function *To);
102 /// \brief Add a function to the call graph, and link the node to all of the
103 /// functions that it calls.
104 void addToCallGraph(Function *F);
107 CallGraph(Module &M);
110 void print(raw_ostream &OS) const;
113 typedef FunctionMapTy::iterator iterator;
114 typedef FunctionMapTy::const_iterator const_iterator;
116 /// \brief Returns the module the call graph corresponds to.
117 Module &getModule() const { return M; }
119 inline iterator begin() { return FunctionMap.begin(); }
120 inline iterator end() { return FunctionMap.end(); }
121 inline const_iterator begin() const { return FunctionMap.begin(); }
122 inline const_iterator end() const { return FunctionMap.end(); }
124 /// \brief Returns the call graph node for the provided function.
125 inline const CallGraphNode *operator[](const Function *F) const {
126 const_iterator I = FunctionMap.find(F);
127 assert(I != FunctionMap.end() && "Function not in callgraph!");
131 /// \brief Returns the call graph node for the provided function.
132 inline CallGraphNode *operator[](const Function *F) {
133 const_iterator I = FunctionMap.find(F);
134 assert(I != FunctionMap.end() && "Function not in callgraph!");
138 /// \brief Returns the \c CallGraphNode which is used to represent
139 /// undetermined calls into the callgraph.
140 CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
142 CallGraphNode *getCallsExternalNode() const { return CallsExternalNode; }
144 //===---------------------------------------------------------------------
145 // Functions to keep a call graph up to date with a function that has been
149 /// \brief Unlink the function from this module, returning it.
151 /// Because this removes the function from the module, the call graph node is
152 /// destroyed. This is only valid if the function does not call any other
153 /// functions (ie, there are no edges in it's CGN). The easiest way to do
154 /// this is to dropAllReferences before calling this.
155 Function *removeFunctionFromModule(CallGraphNode *CGN);
157 /// \brief Similar to operator[], but this will insert a new CallGraphNode for
158 /// \c F if one does not already exist.
159 CallGraphNode *getOrInsertFunction(const Function *F);
162 /// \brief A node in the call graph for a module.
164 /// Typically represents a function in the call graph. There are also special
165 /// "null" nodes used to represent theoretical entries in the call graph.
166 class CallGraphNode {
168 /// \brief A pair of the calling instruction (a call or invoke)
169 /// and the call graph node being called.
170 typedef std::pair<WeakVH, CallGraphNode *> CallRecord;
173 typedef std::vector<CallRecord> CalledFunctionsVector;
175 /// \brief Creates a node for the specified function.
176 inline CallGraphNode(Function *F) : F(F), NumReferences(0) {}
179 assert(NumReferences == 0 && "Node deleted while references remain");
182 typedef std::vector<CallRecord>::iterator iterator;
183 typedef std::vector<CallRecord>::const_iterator const_iterator;
185 /// \brief Returns the function that this call graph node represents.
186 Function *getFunction() const { return F; }
188 inline iterator begin() { return CalledFunctions.begin(); }
189 inline iterator end() { return CalledFunctions.end(); }
190 inline const_iterator begin() const { return CalledFunctions.begin(); }
191 inline const_iterator end() const { return CalledFunctions.end(); }
192 inline bool empty() const { return CalledFunctions.empty(); }
193 inline unsigned size() const { return (unsigned)CalledFunctions.size(); }
195 /// \brief Returns the number of other CallGraphNodes in this CallGraph that
196 /// reference this node in their callee list.
197 unsigned getNumReferences() const { return NumReferences; }
199 /// \brief Returns the i'th called function.
200 CallGraphNode *operator[](unsigned i) const {
201 assert(i < CalledFunctions.size() && "Invalid index");
202 return CalledFunctions[i].second;
205 /// \brief Print out this call graph node.
207 void print(raw_ostream &OS) const;
209 //===---------------------------------------------------------------------
210 // Methods to keep a call graph up to date with a function that has been
214 /// \brief Removes all edges from this CallGraphNode to any functions it
216 void removeAllCalledFunctions() {
217 while (!CalledFunctions.empty()) {
218 CalledFunctions.back().second->DropRef();
219 CalledFunctions.pop_back();
223 /// \brief Moves all the callee information from N to this node.
224 void stealCalledFunctionsFrom(CallGraphNode *N) {
225 assert(CalledFunctions.empty() &&
226 "Cannot steal callsite information if I already have some");
227 std::swap(CalledFunctions, N->CalledFunctions);
230 /// \brief Adds a function to the list of functions called by this one.
231 void addCalledFunction(CallSite CS, CallGraphNode *M) {
232 assert(!CS.getInstruction() || !CS.getCalledFunction() ||
233 !CS.getCalledFunction()->isIntrinsic());
234 CalledFunctions.push_back(std::make_pair(CS.getInstruction(), M));
238 void removeCallEdge(iterator I) {
239 I->second->DropRef();
240 *I = CalledFunctions.back();
241 CalledFunctions.pop_back();
244 /// \brief Removes the edge in the node for the specified call site.
246 /// Note that this method takes linear time, so it should be used sparingly.
247 void removeCallEdgeFor(CallSite CS);
249 /// \brief Removes all call edges from this node to the specified callee
252 /// This takes more time to execute than removeCallEdgeTo, so it should not
253 /// be used unless necessary.
254 void removeAnyCallEdgeTo(CallGraphNode *Callee);
256 /// \brief Removes one edge associated with a null callsite from this node to
257 /// the specified callee function.
258 void removeOneAbstractEdgeTo(CallGraphNode *Callee);
260 /// \brief Replaces the edge in the node for the specified call site with a
263 /// Note that this method takes linear time, so it should be used sparingly.
264 void replaceCallEdge(CallSite CS, CallSite NewCS, CallGraphNode *NewNode);
267 friend class CallGraph;
269 AssertingVH<Function> F;
271 std::vector<CallRecord> CalledFunctions;
273 /// \brief The number of times that this CallGraphNode occurs in the
274 /// CalledFunctions array of this or other CallGraphNodes.
275 unsigned NumReferences;
277 CallGraphNode(const CallGraphNode &) LLVM_DELETED_FUNCTION;
278 void operator=(const CallGraphNode &) LLVM_DELETED_FUNCTION;
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 {
294 /// \brief A formulaic typedef to inform clients of the result type.
295 typedef CallGraph Result;
297 static void *ID() { return (void *)&PassID; }
299 /// \brief Compute the \c CallGraph for the module \c M.
301 /// The real work here is done in the \c CallGraph constructor.
302 CallGraph run(Module *M) { return CallGraph(*M); }
308 /// \brief The \c ModulePass which wraps up a \c CallGraph and the logic to
311 /// This class exposes both the interface to the call graph container and the
312 /// module pass which runs over a module of IR and produces the call graph. The
313 /// call graph interface is entirelly a wrapper around a \c CallGraph object
314 /// which is stored internally for each module.
315 class CallGraphWrapperPass : public ModulePass {
316 std::unique_ptr<CallGraph> G;
319 static char ID; // Class identification, replacement for typeinfo
321 CallGraphWrapperPass();
322 virtual ~CallGraphWrapperPass();
324 /// \brief The internal \c CallGraph around which the rest of this interface
326 const CallGraph &getCallGraph() const { return *G; }
327 CallGraph &getCallGraph() { return *G; }
329 typedef CallGraph::iterator iterator;
330 typedef CallGraph::const_iterator const_iterator;
332 /// \brief Returns the module the call graph corresponds to.
333 Module &getModule() const { return G->getModule(); }
335 inline iterator begin() { return G->begin(); }
336 inline iterator end() { return G->end(); }
337 inline const_iterator begin() const { return G->begin(); }
338 inline const_iterator end() const { return G->end(); }
340 /// \brief Returns the call graph node for the provided function.
341 inline const CallGraphNode *operator[](const Function *F) const {
345 /// \brief Returns the call graph node for the provided function.
346 inline CallGraphNode *operator[](const Function *F) { return (*G)[F]; }
348 /// \brief Returns the \c CallGraphNode which is used to represent
349 /// undetermined calls into the callgraph.
350 CallGraphNode *getExternalCallingNode() const {
351 return G->getExternalCallingNode();
354 CallGraphNode *getCallsExternalNode() const {
355 return G->getCallsExternalNode();
358 //===---------------------------------------------------------------------
359 // Functions to keep a call graph up to date with a function that has been
363 /// \brief Unlink the function from this module, returning it.
365 /// Because this removes the function from the module, the call graph node is
366 /// destroyed. This is only valid if the function does not call any other
367 /// functions (ie, there are no edges in it's CGN). The easiest way to do
368 /// this is to dropAllReferences before calling this.
369 Function *removeFunctionFromModule(CallGraphNode *CGN) {
370 return G->removeFunctionFromModule(CGN);
373 /// \brief Similar to operator[], but this will insert a new CallGraphNode for
374 /// \c F if one does not already exist.
375 CallGraphNode *getOrInsertFunction(const Function *F) {
376 return G->getOrInsertFunction(F);
379 //===---------------------------------------------------------------------
380 // Implementation of the ModulePass interface needed here.
383 void getAnalysisUsage(AnalysisUsage &AU) const override;
384 bool runOnModule(Module &M) override;
385 void releaseMemory() override;
387 void print(raw_ostream &o, const Module *) const override;
391 //===----------------------------------------------------------------------===//
392 // GraphTraits specializations for call graphs so that they can be treated as
393 // graphs by the generic graph algorithms.
396 // Provide graph traits for tranversing call graphs using standard graph
398 template <> struct GraphTraits<CallGraphNode *> {
399 typedef CallGraphNode NodeType;
401 typedef CallGraphNode::CallRecord CGNPairTy;
402 typedef std::pointer_to_unary_function<CGNPairTy, CallGraphNode *>
405 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
407 typedef mapped_iterator<NodeType::iterator, CGNDerefFun> ChildIteratorType;
409 static inline ChildIteratorType child_begin(NodeType *N) {
410 return map_iterator(N->begin(), CGNDerefFun(CGNDeref));
412 static inline ChildIteratorType child_end(NodeType *N) {
413 return map_iterator(N->end(), CGNDerefFun(CGNDeref));
416 static CallGraphNode *CGNDeref(CGNPairTy P) { return P.second; }
419 template <> struct GraphTraits<const CallGraphNode *> {
420 typedef const CallGraphNode NodeType;
421 typedef NodeType::const_iterator ChildIteratorType;
423 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
424 static inline ChildIteratorType child_begin(NodeType *N) {
427 static inline ChildIteratorType child_end(NodeType *N) { return N->end(); }
431 struct GraphTraits<CallGraph *> : public GraphTraits<CallGraphNode *> {
432 static NodeType *getEntryNode(CallGraph *CGN) {
433 return CGN->getExternalCallingNode(); // Start at the external node!
435 typedef std::pair<const Function *, CallGraphNode *> PairTy;
436 typedef std::pointer_to_unary_function<PairTy, CallGraphNode &> DerefFun;
438 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
439 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
440 static nodes_iterator nodes_begin(CallGraph *CG) {
441 return map_iterator(CG->begin(), DerefFun(CGdereference));
443 static nodes_iterator nodes_end(CallGraph *CG) {
444 return map_iterator(CG->end(), DerefFun(CGdereference));
447 static CallGraphNode &CGdereference(PairTy P) { return *P.second; }
451 struct GraphTraits<const CallGraph *> : public GraphTraits<
452 const CallGraphNode *> {
453 static NodeType *getEntryNode(const CallGraph *CGN) {
454 return CGN->getExternalCallingNode();
456 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
457 typedef CallGraph::const_iterator nodes_iterator;
458 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
459 static nodes_iterator nodes_end(const CallGraph *CG) { return CG->end(); }
462 } // End llvm namespace
464 // Make sure that any clients of this file link in CallGraph.cpp
465 FORCE_DEFINING_FILE_TO_BE_LINKED(CallGraph)