1 //===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This interface is used to build and manipulate a call graph, which is a very
11 // useful tool for interprocedural optimization.
13 // Every function in a module is represented as a node in the call graph. The
14 // callgraph node keeps track of which functions the are called by the function
15 // corresponding to the node.
17 // A call graph may contain nodes where the function that they correspond to is
18 // null. These 'external' nodes are used to represent control flow that is not
19 // represented (or analyzable) in the module. In particular, this analysis
20 // builds one external node such that:
21 // 1. All functions in the module without internal linkage will have edges
22 // from this external node, indicating that they could be called by
23 // functions outside of the module.
24 // 2. All functions whose address is used for something more than a direct
25 // call, for example being stored into a memory location will also have an
26 // edge from this external node. Since they may be called by an unknown
27 // caller later, they must be tracked as such.
29 // There is a second external node added for calls that leave this module.
30 // Functions have a call edge to the external node iff:
31 // 1. The function is external, reflecting the fact that they could call
32 // anything without internal linkage or that has its address taken.
33 // 2. The function contains an indirect function call.
35 // As an extension in the future, there may be multiple nodes with a null
36 // function. These will be used when we can prove (through pointer analysis)
37 // that an indirect call site can call only a specific set of functions.
39 // Because of these properties, the CallGraph captures a conservative superset
40 // of all of the caller-callee relationships, which is useful for
43 // The CallGraph class also attempts to figure out what the root of the
44 // CallGraph is, which it currently does by looking for a function named 'main'.
45 // If no function named 'main' is found, the external node is used as the entry
46 // node, reflecting the fact that any function without internal linkage could
47 // be called into (which is common for libraries).
49 //===----------------------------------------------------------------------===//
51 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
52 #define LLVM_ANALYSIS_CALLGRAPH_H
54 #include "Support/GraphTraits.h"
55 #include "Support/STLExtras.h"
56 #include "llvm/Pass.h"
64 //===----------------------------------------------------------------------===//
65 // CallGraph class definition
67 class CallGraph : public Pass {
68 Module *Mod; // The module this call graph represents
70 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
71 FunctionMapTy FunctionMap; // Map from a function to its node
73 // Root is root of the call graph, or the external node if a 'main' function
78 // ExternalCallingNode - This node has edges to all external functions and
79 // those internal functions that have their address taken.
80 CallGraphNode *ExternalCallingNode;
82 // CallsExternalNode - This node has edges to it from all functions making
83 // indirect calls or calling an external function.
84 CallGraphNode *CallsExternalNode;
87 //===---------------------------------------------------------------------
90 typedef FunctionMapTy::iterator iterator;
91 typedef FunctionMapTy::const_iterator const_iterator;
93 CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
94 CallGraphNode *getCallsExternalNode() const { return CallsExternalNode; }
96 // getRoot - Return the root of the call graph, which is either main, or if
97 // main cannot be found, the external node.
99 CallGraphNode *getRoot() { return Root; }
100 const CallGraphNode *getRoot() const { return Root; }
102 /// getModule - Return the module the call graph corresponds to.
104 Module &getModule() const { return *Mod; }
106 inline iterator begin() { return FunctionMap.begin(); }
107 inline iterator end() { return FunctionMap.end(); }
108 inline const_iterator begin() const { return FunctionMap.begin(); }
109 inline const_iterator end() const { return FunctionMap.end(); }
112 // Subscripting operators, return the call graph node for the provided
114 inline const CallGraphNode *operator[](const Function *F) const {
115 const_iterator I = FunctionMap.find(F);
116 assert(I != FunctionMap.end() && "Function not in callgraph!");
119 inline CallGraphNode *operator[](const Function *F) {
120 const_iterator I = FunctionMap.find(F);
121 assert(I != FunctionMap.end() && "Function not in callgraph!");
125 //===---------------------------------------------------------------------
126 // Functions to keep a call graph up to date with a function that has been
129 void addFunctionToModule(Function *F);
132 // removeFunctionFromModule - Unlink the function from this module, returning
133 // it. Because this removes the function from the module, the call graph node
134 // is destroyed. This is only valid if the function does not call any other
135 // functions (ie, there are no edges in it's CGN). The easiest way to do this
136 // is to dropAllReferences before calling this.
138 Function *removeFunctionFromModule(CallGraphNode *CGN);
139 Function *removeFunctionFromModule(Function *F) {
140 return removeFunctionFromModule((*this)[F]);
144 //===---------------------------------------------------------------------
145 // Pass infrastructure interface glue code...
147 CallGraph() : Root(0), CallsExternalNode(0) {}
148 ~CallGraph() { destroy(); }
150 // run - Compute the call graph for the specified module.
151 virtual bool run(Module &M);
153 // getAnalysisUsage - This obviously provides a call graph
154 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
155 AU.setPreservesAll();
158 // releaseMemory - Data structures can be large, so free memory aggressively.
159 virtual void releaseMemory() {
163 /// Print the types found in the module. If the optional Module parameter is
164 /// passed in, then the types are printed symbolically if possible, using the
165 /// symbol table from the module.
167 void print(std::ostream &o, const Module *M) const;
169 // stub - dummy function, just ignore it
172 //===---------------------------------------------------------------------
173 // Implementation of CallGraph construction
176 // getNodeFor - Return the node for the specified function or create one if it
177 // does not already exist.
179 CallGraphNode *getNodeFor(Function *F);
181 // addToCallGraph - Add a function to the call graph, and link the node to all
182 // of the functions that it calls.
184 void addToCallGraph(Function *F);
186 // destroy - Release memory for the call graph
191 //===----------------------------------------------------------------------===//
192 // CallGraphNode class definition
194 class CallGraphNode {
196 std::vector<CallGraphNode*> CalledFunctions;
198 CallGraphNode(const CallGraphNode &); // Do not implement
200 //===---------------------------------------------------------------------
201 // Accessor methods...
204 typedef std::vector<CallGraphNode*>::iterator iterator;
205 typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
207 // getFunction - Return the function that this call graph node represents...
208 Function *getFunction() const { return F; }
210 inline iterator begin() { return CalledFunctions.begin(); }
211 inline iterator end() { return CalledFunctions.end(); }
212 inline const_iterator begin() const { return CalledFunctions.begin(); }
213 inline const_iterator end() const { return CalledFunctions.end(); }
214 inline unsigned size() const { return CalledFunctions.size(); }
216 // Subscripting operator - Return the i'th called function...
218 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
221 //===---------------------------------------------------------------------
222 // Methods to keep a call graph up to date with a function that has been
226 void removeAllCalledFunctions() {
227 CalledFunctions.clear();
230 // addCalledFunction add a function to the list of functions called by this
232 void addCalledFunction(CallGraphNode *M) {
233 CalledFunctions.push_back(M);
236 void removeCallEdgeTo(CallGraphNode *Callee);
238 private: // Stuff to construct the node, used by CallGraph
239 friend class CallGraph;
241 // CallGraphNode ctor - Create a node for the specified function...
242 inline CallGraphNode(Function *f) : F(f) {}
247 //===----------------------------------------------------------------------===//
248 // GraphTraits specializations for call graphs so that they can be treated as
249 // graphs by the generic graph algorithms...
252 // Provide graph traits for tranversing call graphs using standard graph
254 template <> struct GraphTraits<CallGraphNode*> {
255 typedef CallGraphNode NodeType;
256 typedef NodeType::iterator ChildIteratorType;
258 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
259 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
260 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
263 template <> struct GraphTraits<const CallGraphNode*> {
264 typedef const CallGraphNode NodeType;
265 typedef NodeType::const_iterator ChildIteratorType;
267 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
268 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
269 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
272 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
273 static NodeType *getEntryNode(CallGraph *CGN) {
274 return CGN->getExternalCallingNode(); // Start at the external node!
276 typedef std::pair<const Function*, CallGraphNode*> PairTy;
277 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
279 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
280 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
281 static nodes_iterator nodes_begin(CallGraph *CG) {
282 return map_iterator(CG->begin(), DerefFun(CGdereference));
284 static nodes_iterator nodes_end (CallGraph *CG) {
285 return map_iterator(CG->end(), DerefFun(CGdereference));
288 static CallGraphNode &CGdereference (std::pair<const Function*,
293 template<> struct GraphTraits<const CallGraph*> :
294 public GraphTraits<const CallGraphNode*> {
295 static NodeType *getEntryNode(const CallGraph *CGN) {
296 return CGN->getExternalCallingNode();
298 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
299 typedef CallGraph::const_iterator nodes_iterator;
300 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
301 static nodes_iterator nodes_end (const CallGraph *CG) { return CG->end(); }
304 // Make sure that any clients of this file link in PostDominators.cpp
306 CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub);
308 } // End llvm namespace