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 "llvm/Pass.h"
50 //===----------------------------------------------------------------------===//
51 // CallGraph class definition
53 class CallGraph : public Pass {
54 Module *Mod; // The module this call graph represents
56 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
57 FunctionMapTy FunctionMap; // Map from a function to its node
59 // Root is root of the call graph, or the external node if a 'main' function
60 // couldn't be found. ExternalNode is equivalent to (*this)[0].
62 CallGraphNode *Root, *ExternalNode;
65 //===---------------------------------------------------------------------
68 typedef FunctionMapTy::iterator iterator;
69 typedef FunctionMapTy::const_iterator const_iterator;
71 // getExternalNode - Return the node that points to all functions that are
72 // accessable from outside of the current program.
74 CallGraphNode *getExternalNode() { return ExternalNode; }
75 const CallGraphNode *getExternalNode() const { return ExternalNode; }
77 // getRoot - Return the root of the call graph, which is either main, or if
78 // main cannot be found, the external node.
80 CallGraphNode *getRoot() { return Root; }
81 const CallGraphNode *getRoot() const { return Root; }
83 inline iterator begin() { return FunctionMap.begin(); }
84 inline iterator end() { return FunctionMap.end(); }
85 inline const_iterator begin() const { return FunctionMap.begin(); }
86 inline const_iterator end() const { return FunctionMap.end(); }
89 // Subscripting operators, return the call graph node for the provided
91 inline const CallGraphNode *operator[](const Function *F) const {
92 const_iterator I = FunctionMap.find(F);
93 assert(I != FunctionMap.end() && "Function not in callgraph!");
96 inline CallGraphNode *operator[](const Function *F) {
97 const_iterator I = FunctionMap.find(F);
98 assert(I != FunctionMap.end() && "Function not in callgraph!");
102 //===---------------------------------------------------------------------
103 // Functions to keep a call graph up to date with a function that has been
106 void addFunctionToModule(Function *Meth);
109 // removeFunctionFromModule - Unlink the function from this module, returning
110 // it. Because this removes the function from the module, the call graph node
111 // is destroyed. This is only valid if the function does not call any other
112 // functions (ie, there are no edges in it's CGN). The easiest way to do this
113 // is to dropAllReferences before calling this.
115 Function *removeFunctionFromModule(CallGraphNode *CGN);
116 Function *removeFunctionFromModule(Function *Meth) {
117 return removeFunctionFromModule((*this)[Meth]);
121 //===---------------------------------------------------------------------
122 // Pass infrastructure interface glue code...
124 static AnalysisID ID; // We are an analysis, we must have an ID
126 CallGraph() : Root(0) {}
127 ~CallGraph() { destroy(); }
129 // run - Compute the call graph for the specified module.
130 virtual bool run(Module &M);
132 // getAnalysisUsage - This obviously provides a call graph
133 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
134 AU.setPreservesAll();
137 // releaseMemory - Data structures can be large, so free memory aggressively.
138 virtual void releaseMemory() {
143 //===---------------------------------------------------------------------
144 // Implementation of CallGraph construction
147 // getNodeFor - Return the node for the specified function or create one if it
148 // does not already exist.
150 CallGraphNode *getNodeFor(Function *F);
152 // addToCallGraph - Add a function to the call graph, and link the node to all
153 // of the functions that it calls.
155 void addToCallGraph(Function *F);
157 // destroy - Release memory for the call graph
162 //===----------------------------------------------------------------------===//
163 // CallGraphNode class definition
165 class CallGraphNode {
167 std::vector<CallGraphNode*> CalledFunctions;
169 CallGraphNode(const CallGraphNode &); // Do not implement
171 //===---------------------------------------------------------------------
172 // Accessor methods...
175 typedef std::vector<CallGraphNode*>::iterator iterator;
176 typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
178 // getFunction - Return the function that this call graph node represents...
179 Function *getFunction() const { return Meth; }
181 inline iterator begin() { return CalledFunctions.begin(); }
182 inline iterator end() { return CalledFunctions.end(); }
183 inline const_iterator begin() const { return CalledFunctions.begin(); }
184 inline const_iterator end() const { return CalledFunctions.end(); }
185 inline unsigned size() const { return CalledFunctions.size(); }
187 // Subscripting operator - Return the i'th called function...
189 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
192 //===---------------------------------------------------------------------
193 // Methods to keep a call graph up to date with a function that has been
197 void removeAllCalledFunctions() {
198 CalledFunctions.clear();
201 private: // Stuff to construct the node, used by CallGraph
202 friend class CallGraph;
204 // CallGraphNode ctor - Create a node for the specified function...
205 inline CallGraphNode(Function *F) : Meth(F) {}
207 // addCalledFunction add a function to the list of functions called by this
209 void addCalledFunction(CallGraphNode *M) {
210 CalledFunctions.push_back(M);
216 //===----------------------------------------------------------------------===//
217 // GraphTraits specializations for call graphs so that they can be treated as
218 // graphs by the generic graph algorithms...
221 // Provide graph traits for tranversing call graphs using standard graph
223 template <> struct GraphTraits<CallGraphNode*> {
224 typedef CallGraphNode NodeType;
225 typedef NodeType::iterator ChildIteratorType;
227 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
228 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
229 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
232 template <> struct GraphTraits<const CallGraphNode*> {
233 typedef const CallGraphNode NodeType;
234 typedef NodeType::const_iterator ChildIteratorType;
236 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
237 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
238 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
242 template<> struct GraphTraits<CallGraph*> :
243 public GraphTraits<CallGraphNode*> {
244 static NodeType *getEntryNode(CallGraph *CGN) {
245 return CGN->getExternalNode(); // Start at the external node!
248 template<> struct GraphTraits<const CallGraph*> :
249 public GraphTraits<const CallGraphNode*> {
250 static NodeType *getEntryNode(const CallGraph *CGN) {
251 return CGN->getExternalNode();
256 //===----------------------------------------------------------------------===//
257 // Printing support for Call Graphs
260 // Stuff for printing out a callgraph...
262 void WriteToOutput(const CallGraph &, std::ostream &o);
263 inline std::ostream &operator <<(std::ostream &o, const CallGraph &CG) {
264 WriteToOutput(CG, o); return o;
267 void WriteToOutput(const CallGraphNode *, std::ostream &o);
268 inline std::ostream &operator <<(std::ostream &o, const CallGraphNode *CGN) {
269 WriteToOutput(CGN, o); return o;