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
44 #include "Support/GraphTraits.h"
45 #include "Support/STLExtras.h"
46 #include "llvm/Pass.h"
51 //===----------------------------------------------------------------------===//
52 // CallGraph class definition
54 class CallGraph : public Pass {
55 Module *Mod; // The module this call graph represents
57 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
58 FunctionMapTy FunctionMap; // Map from a function to its node
60 // Root is root of the call graph, or the external node if a 'main' function
61 // couldn't be found. ExternalNode is equivalent to (*this)[0].
63 CallGraphNode *Root, *ExternalNode;
66 //===---------------------------------------------------------------------
69 typedef FunctionMapTy::iterator iterator;
70 typedef FunctionMapTy::const_iterator const_iterator;
72 // getExternalNode - Return the node that points to all functions that are
73 // accessable from outside of the current program.
75 CallGraphNode *getExternalNode() { return ExternalNode; }
76 const CallGraphNode *getExternalNode() const { return ExternalNode; }
78 // getRoot - Return the root of the call graph, which is either main, or if
79 // main cannot be found, the external node.
81 CallGraphNode *getRoot() { return Root; }
82 const CallGraphNode *getRoot() const { return Root; }
84 inline iterator begin() { return FunctionMap.begin(); }
85 inline iterator end() { return FunctionMap.end(); }
86 inline const_iterator begin() const { return FunctionMap.begin(); }
87 inline const_iterator end() const { return FunctionMap.end(); }
90 // Subscripting operators, return the call graph node for the provided
92 inline const CallGraphNode *operator[](const Function *F) const {
93 const_iterator I = FunctionMap.find(F);
94 assert(I != FunctionMap.end() && "Function not in callgraph!");
97 inline CallGraphNode *operator[](const Function *F) {
98 const_iterator I = FunctionMap.find(F);
99 assert(I != FunctionMap.end() && "Function not in callgraph!");
103 //===---------------------------------------------------------------------
104 // Functions to keep a call graph up to date with a function that has been
107 void addFunctionToModule(Function *Meth);
110 // removeFunctionFromModule - Unlink the function from this module, returning
111 // it. Because this removes the function from the module, the call graph node
112 // is destroyed. This is only valid if the function does not call any other
113 // functions (ie, there are no edges in it's CGN). The easiest way to do this
114 // is to dropAllReferences before calling this.
116 Function *removeFunctionFromModule(CallGraphNode *CGN);
117 Function *removeFunctionFromModule(Function *Meth) {
118 return removeFunctionFromModule((*this)[Meth]);
122 //===---------------------------------------------------------------------
123 // Pass infrastructure interface glue code...
125 CallGraph() : Root(0) {}
126 ~CallGraph() { destroy(); }
128 // run - Compute the call graph for the specified module.
129 virtual bool run(Module &M);
131 // getAnalysisUsage - This obviously provides a call graph
132 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
133 AU.setPreservesAll();
136 // releaseMemory - Data structures can be large, so free memory aggressively.
137 virtual void releaseMemory() {
141 /// Print the types found in the module. If the optional Module parameter is
142 /// passed in, then the types are printed symbolically if possible, using the
143 /// symbol table from the module.
145 void print(std::ostream &o, const Module *M) const;
148 //===---------------------------------------------------------------------
149 // Implementation of CallGraph construction
152 // getNodeFor - Return the node for the specified function or create one if it
153 // does not already exist.
155 CallGraphNode *getNodeFor(Function *F);
157 // addToCallGraph - Add a function to the call graph, and link the node to all
158 // of the functions that it calls.
160 void addToCallGraph(Function *F);
162 // destroy - Release memory for the call graph
167 //===----------------------------------------------------------------------===//
168 // CallGraphNode class definition
170 class CallGraphNode {
172 std::vector<CallGraphNode*> CalledFunctions;
174 CallGraphNode(const CallGraphNode &); // Do not implement
176 //===---------------------------------------------------------------------
177 // Accessor methods...
180 typedef std::vector<CallGraphNode*>::iterator iterator;
181 typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
183 // getFunction - Return the function that this call graph node represents...
184 Function *getFunction() const { return Meth; }
186 inline iterator begin() { return CalledFunctions.begin(); }
187 inline iterator end() { return CalledFunctions.end(); }
188 inline const_iterator begin() const { return CalledFunctions.begin(); }
189 inline const_iterator end() const { return CalledFunctions.end(); }
190 inline unsigned size() const { return CalledFunctions.size(); }
192 // Subscripting operator - Return the i'th called function...
194 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
197 //===---------------------------------------------------------------------
198 // Methods to keep a call graph up to date with a function that has been
202 void removeAllCalledFunctions() {
203 CalledFunctions.clear();
206 private: // Stuff to construct the node, used by CallGraph
207 friend class CallGraph;
209 // CallGraphNode ctor - Create a node for the specified function...
210 inline CallGraphNode(Function *F) : Meth(F) {}
212 // addCalledFunction add a function to the list of functions called by this
214 void addCalledFunction(CallGraphNode *M) {
215 CalledFunctions.push_back(M);
221 //===----------------------------------------------------------------------===//
222 // GraphTraits specializations for call graphs so that they can be treated as
223 // graphs by the generic graph algorithms...
226 // Provide graph traits for tranversing call graphs using standard graph
228 template <> struct GraphTraits<CallGraphNode*> {
229 typedef CallGraphNode NodeType;
230 typedef NodeType::iterator ChildIteratorType;
232 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
233 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
234 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
237 template <> struct GraphTraits<const CallGraphNode*> {
238 typedef const CallGraphNode NodeType;
239 typedef NodeType::const_iterator ChildIteratorType;
241 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
242 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
243 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
246 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
247 static NodeType *getEntryNode(CallGraph *CGN) {
248 return CGN->getExternalNode(); // Start at the external node!
250 typedef std::pair<const Function*, CallGraphNode*> PairTy;
251 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
253 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
254 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
255 static nodes_iterator nodes_begin(CallGraph *CG) {
256 return map_iterator(CG->begin(), DerefFun(CGdereference));
258 static nodes_iterator nodes_end (CallGraph *CG) {
259 return map_iterator(CG->end(), DerefFun(CGdereference));
262 static CallGraphNode &CGdereference (std::pair<const Function*,
267 template<> struct GraphTraits<const CallGraph*> :
268 public GraphTraits<const CallGraphNode*> {
269 static NodeType *getEntryNode(const CallGraph *CGN) {
270 return CGN->getExternalNode();
272 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
273 typedef CallGraph::const_iterator nodes_iterator;
274 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
275 static nodes_iterator nodes_end (const CallGraph *CG) { return CG->end(); }