1 //===- CallGraph.h - Build a Module's call graph -----------------*- C++ -*--=//
3 // This interface is used to build and manipulate a call graph, which is a very
4 // useful tool for interprocedural optimization.
6 // Every function in a module is represented as a node in the call graph. The
7 // callgraph node keeps track of which functions the are called by the function
8 // corresponding to the node.
10 // A call graph will contain nodes where the function that they correspond to is
11 // null. This 'external' node is used to represent control flow that is not
12 // represented (or analyzable) in the module. As such, the external node will
13 // have edges to functions with the following properties:
14 // 1. All functions in the module without internal linkage, since they could
15 // be called by functions outside of the our analysis capability.
16 // 2. All functions whose address is used for something more than a direct
17 // call, for example being stored into a memory location. Since they may
18 // be called by an unknown caller later, they must be tracked as such.
20 // Similarly, functions have a call edge to the external node iff:
21 // 1. The function is external, reflecting the fact that they could call
22 // anything without internal linkage or that has its address taken.
23 // 2. The function contains an indirect function call.
25 // As an extension in the future, there may be multiple nodes with a null
26 // function. These will be used when we can prove (through pointer analysis)
27 // that an indirect call site can call only a specific set of functions.
29 // Because of these properties, the CallGraph captures a conservative superset
30 // of all of the caller-callee relationships, which is useful for
33 // The CallGraph class also attempts to figure out what the root of the
34 // CallGraph is, which is currently does by looking for a function named 'main'.
35 // If no function named 'main' is found, the external node is used as the entry
36 // node, reflecting the fact that any function without internal linkage could
37 // be called into (which is common for libraries).
39 //===----------------------------------------------------------------------===//
41 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
42 #define LLVM_ANALYSIS_CALLGRAPH_H
46 #include "Support/GraphTraits.h"
47 #include "Support/STLExtras.h"
48 #include "llvm/Pass.h"
53 //===----------------------------------------------------------------------===//
54 // CallGraph class definition
56 class CallGraph : public Pass {
57 Module *Mod; // The module this call graph represents
59 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
60 FunctionMapTy FunctionMap; // Map from a function to its node
62 // Root is root of the call graph, or the external node if a 'main' function
63 // couldn't be found. ExternalNode is equivalent to (*this)[0].
65 CallGraphNode *Root, *ExternalNode;
68 //===---------------------------------------------------------------------
71 typedef FunctionMapTy::iterator iterator;
72 typedef FunctionMapTy::const_iterator const_iterator;
74 // getExternalNode - Return the node that points to all functions that are
75 // accessable from outside of the current program.
77 CallGraphNode *getExternalNode() { return ExternalNode; }
78 const CallGraphNode *getExternalNode() const { return ExternalNode; }
80 // getRoot - Return the root of the call graph, which is either main, or if
81 // main cannot be found, the external node.
83 CallGraphNode *getRoot() { return Root; }
84 const CallGraphNode *getRoot() const { return Root; }
86 inline iterator begin() { return FunctionMap.begin(); }
87 inline iterator end() { return FunctionMap.end(); }
88 inline const_iterator begin() const { return FunctionMap.begin(); }
89 inline const_iterator end() const { return FunctionMap.end(); }
92 // Subscripting operators, return the call graph node for the provided
94 inline const CallGraphNode *operator[](const Function *F) const {
95 const_iterator I = FunctionMap.find(F);
96 assert(I != FunctionMap.end() && "Function not in callgraph!");
99 inline CallGraphNode *operator[](const Function *F) {
100 const_iterator I = FunctionMap.find(F);
101 assert(I != FunctionMap.end() && "Function not in callgraph!");
105 //===---------------------------------------------------------------------
106 // Functions to keep a call graph up to date with a function that has been
109 void addFunctionToModule(Function *Meth);
112 // removeFunctionFromModule - Unlink the function from this module, returning
113 // it. Because this removes the function from the module, the call graph node
114 // is destroyed. This is only valid if the function does not call any other
115 // functions (ie, there are no edges in it's CGN). The easiest way to do this
116 // is to dropAllReferences before calling this.
118 Function *removeFunctionFromModule(CallGraphNode *CGN);
119 Function *removeFunctionFromModule(Function *Meth) {
120 return removeFunctionFromModule((*this)[Meth]);
124 //===---------------------------------------------------------------------
125 // Pass infrastructure interface glue code...
127 CallGraph() : Root(0) {}
128 ~CallGraph() { destroy(); }
130 // run - Compute the call graph for the specified module.
131 virtual bool run(Module &M);
133 // getAnalysisUsage - This obviously provides a call graph
134 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
135 AU.setPreservesAll();
138 // releaseMemory - Data structures can be large, so free memory aggressively.
139 virtual void releaseMemory() {
143 /// Print the types found in the module. If the optional Module parameter is
144 /// passed in, then the types are printed symbolically if possible, using the
145 /// symbol table from the module.
147 void print(std::ostream &o, const Module *M) const;
150 //===---------------------------------------------------------------------
151 // Implementation of CallGraph construction
154 // getNodeFor - Return the node for the specified function or create one if it
155 // does not already exist.
157 CallGraphNode *getNodeFor(Function *F);
159 // addToCallGraph - Add a function to the call graph, and link the node to all
160 // of the functions that it calls.
162 void addToCallGraph(Function *F);
164 // destroy - Release memory for the call graph
169 //===----------------------------------------------------------------------===//
170 // CallGraphNode class definition
172 class CallGraphNode {
174 std::vector<CallGraphNode*> CalledFunctions;
176 CallGraphNode(const CallGraphNode &); // Do not implement
178 //===---------------------------------------------------------------------
179 // Accessor methods...
182 typedef std::vector<CallGraphNode*>::iterator iterator;
183 typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
185 // getFunction - Return the function that this call graph node represents...
186 Function *getFunction() const { return Meth; }
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 unsigned size() const { return CalledFunctions.size(); }
194 // Subscripting operator - Return the i'th called function...
196 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
199 //===---------------------------------------------------------------------
200 // Methods to keep a call graph up to date with a function that has been
204 void removeAllCalledFunctions() {
205 CalledFunctions.clear();
208 private: // Stuff to construct the node, used by CallGraph
209 friend class CallGraph;
211 // CallGraphNode ctor - Create a node for the specified function...
212 inline CallGraphNode(Function *F) : Meth(F) {}
214 // addCalledFunction add a function to the list of functions called by this
216 void addCalledFunction(CallGraphNode *M) {
217 CalledFunctions.push_back(M);
223 //===----------------------------------------------------------------------===//
224 // GraphTraits specializations for call graphs so that they can be treated as
225 // graphs by the generic graph algorithms...
228 // Provide graph traits for tranversing call graphs using standard graph
230 template <> struct GraphTraits<CallGraphNode*> {
231 typedef CallGraphNode NodeType;
232 typedef NodeType::iterator ChildIteratorType;
234 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
235 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
236 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
239 template <> struct GraphTraits<const CallGraphNode*> {
240 typedef const CallGraphNode NodeType;
241 typedef NodeType::const_iterator ChildIteratorType;
243 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
244 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
245 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
248 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
249 static NodeType *getEntryNode(CallGraph *CGN) {
250 return CGN->getExternalNode(); // Start at the external node!
252 typedef std::pair<const Function*, CallGraphNode*> PairTy;
253 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
255 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
256 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
257 static nodes_iterator nodes_begin(CallGraph *CG) {
258 return map_iterator(CG->begin(), DerefFun(CGdereference));
260 static nodes_iterator nodes_end (CallGraph *CG) {
261 return map_iterator(CG->end(), DerefFun(CGdereference));
264 static CallGraphNode &CGdereference (std::pair<const Function*,
269 template<> struct GraphTraits<const CallGraph*> :
270 public GraphTraits<const CallGraphNode*> {
271 static NodeType *getEntryNode(const CallGraph *CGN) {
272 return CGN->getExternalNode();
274 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
275 typedef CallGraph::const_iterator nodes_iterator;
276 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
277 static nodes_iterator nodes_end (const CallGraph *CG) { return CG->end(); }