CallGraph.h revision e0baeec4fec4088b2da21645ec0e6fb8c1d9c631
1//===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 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. 7// 8//===----------------------------------------------------------------------===// 9// 10// This interface is used to build and manipulate a call graph, which is a very 11// useful tool for interprocedural optimization. 12// 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. 16// 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. 28// 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. 34// 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. 38// 39// Because of these properties, the CallGraph captures a conservative superset 40// of all of the caller-callee relationships, which is useful for 41// transformations. 42// 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). 48// 49//===----------------------------------------------------------------------===// 50 51#ifndef LLVM_ANALYSIS_CALLGRAPH_H 52#define LLVM_ANALYSIS_CALLGRAPH_H 53 54#include "Support/GraphTraits.h" 55#include "Support/STLExtras.h" 56#include "llvm/Pass.h" 57 58namespace llvm { 59 60class Function; 61class Module; 62class CallGraphNode; 63 64//===----------------------------------------------------------------------===// 65// CallGraph class definition 66// 67class CallGraph : public Pass { 68 Module *Mod; // The module this call graph represents 69 70 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy; 71 FunctionMapTy FunctionMap; // Map from a function to its node 72 73 // Root is root of the call graph, or the external node if a 'main' function 74 // couldn't be found. 75 // 76 CallGraphNode *Root; 77 78 // ExternalCallingNode - This node has edges to all external functions and 79 // those internal functions that have their address taken. 80 CallGraphNode *ExternalCallingNode; 81 82 // CallsExternalNode - This node has edges to it from all functions making 83 // indirect calls or calling an external function. 84 CallGraphNode *CallsExternalNode; 85 86public: 87 88 //===--------------------------------------------------------------------- 89 // Accessors... 90 // 91 typedef FunctionMapTy::iterator iterator; 92 typedef FunctionMapTy::const_iterator const_iterator; 93 94 CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; } 95 CallGraphNode *getCallsExternalNode() const { return CallsExternalNode; } 96 97 // getRoot - Return the root of the call graph, which is either main, or if 98 // main cannot be found, the external node. 99 // 100 CallGraphNode *getRoot() { return Root; } 101 const CallGraphNode *getRoot() const { return Root; } 102 103 /// getModule - Return the module the call graph corresponds to. 104 /// 105 Module &getModule() const { return *Mod; } 106 107 inline iterator begin() { return FunctionMap.begin(); } 108 inline iterator end() { return FunctionMap.end(); } 109 inline const_iterator begin() const { return FunctionMap.begin(); } 110 inline const_iterator end() const { return FunctionMap.end(); } 111 112 113 // Subscripting operators, return the call graph node for the provided 114 // function 115 inline const CallGraphNode *operator[](const Function *F) const { 116 const_iterator I = FunctionMap.find(F); 117 assert(I != FunctionMap.end() && "Function not in callgraph!"); 118 return I->second; 119 } 120 inline CallGraphNode *operator[](const Function *F) { 121 const_iterator I = FunctionMap.find(F); 122 assert(I != FunctionMap.end() && "Function not in callgraph!"); 123 return I->second; 124 } 125 126 //===--------------------------------------------------------------------- 127 // Functions to keep a call graph up to date with a function that has been 128 // modified 129 // 130 void addFunctionToModule(Function *F); 131 132 133 // removeFunctionFromModule - Unlink the function from this module, returning 134 // it. Because this removes the function from the module, the call graph node 135 // is destroyed. This is only valid if the function does not call any other 136 // functions (ie, there are no edges in it's CGN). The easiest way to do this 137 // is to dropAllReferences before calling this. 138 // 139 Function *removeFunctionFromModule(CallGraphNode *CGN); 140 Function *removeFunctionFromModule(Function *F) { 141 return removeFunctionFromModule((*this)[F]); 142 } 143 144 145 //===--------------------------------------------------------------------- 146 // Pass infrastructure interface glue code... 147 // 148 CallGraph() : Root(0) {} 149 ~CallGraph() { destroy(); } 150 151 // run - Compute the call graph for the specified module. 152 virtual bool run(Module &M); 153 154 // getAnalysisUsage - This obviously provides a call graph 155 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 156 AU.setPreservesAll(); 157 } 158 159 // releaseMemory - Data structures can be large, so free memory aggressively. 160 virtual void releaseMemory() { 161 destroy(); 162 } 163 164 /// Print the types found in the module. If the optional Module parameter is 165 /// passed in, then the types are printed symbolically if possible, using the 166 /// symbol table from the module. 167 /// 168 void print(std::ostream &o, const Module *M) const; 169 170 // stub - dummy function, just ignore it 171 static void stub(); 172private: 173 //===--------------------------------------------------------------------- 174 // Implementation of CallGraph construction 175 // 176 177 // getNodeFor - Return the node for the specified function or create one if it 178 // does not already exist. 179 // 180 CallGraphNode *getNodeFor(Function *F); 181 182 // addToCallGraph - Add a function to the call graph, and link the node to all 183 // of the functions that it calls. 184 // 185 void addToCallGraph(Function *F); 186 187 // destroy - Release memory for the call graph 188 void destroy(); 189}; 190 191 192//===----------------------------------------------------------------------===// 193// CallGraphNode class definition 194// 195class CallGraphNode { 196 Function *F; 197 std::vector<CallGraphNode*> CalledFunctions; 198 199 CallGraphNode(const CallGraphNode &); // Do not implement 200public: 201 //===--------------------------------------------------------------------- 202 // Accessor methods... 203 // 204 205 typedef std::vector<CallGraphNode*>::iterator iterator; 206 typedef std::vector<CallGraphNode*>::const_iterator const_iterator; 207 208 // getFunction - Return the function that this call graph node represents... 209 Function *getFunction() const { return F; } 210 211 inline iterator begin() { return CalledFunctions.begin(); } 212 inline iterator end() { return CalledFunctions.end(); } 213 inline const_iterator begin() const { return CalledFunctions.begin(); } 214 inline const_iterator end() const { return CalledFunctions.end(); } 215 inline unsigned size() const { return CalledFunctions.size(); } 216 217 // Subscripting operator - Return the i'th called function... 218 // 219 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];} 220 221 222 //===--------------------------------------------------------------------- 223 // Methods to keep a call graph up to date with a function that has been 224 // modified 225 // 226 227 void removeAllCalledFunctions() { 228 CalledFunctions.clear(); 229 } 230 231 // addCalledFunction add a function to the list of functions called by this 232 // one 233 void addCalledFunction(CallGraphNode *M) { 234 CalledFunctions.push_back(M); 235 } 236 237 void removeCallEdgeTo(CallGraphNode *Callee); 238 239private: // Stuff to construct the node, used by CallGraph 240 friend class CallGraph; 241 242 // CallGraphNode ctor - Create a node for the specified function... 243 inline CallGraphNode(Function *f) : F(f) {} 244}; 245 246 247 248//===----------------------------------------------------------------------===// 249// GraphTraits specializations for call graphs so that they can be treated as 250// graphs by the generic graph algorithms... 251// 252 253// Provide graph traits for tranversing call graphs using standard graph 254// traversals. 255template <> struct GraphTraits<CallGraphNode*> { 256 typedef CallGraphNode NodeType; 257 typedef NodeType::iterator ChildIteratorType; 258 259 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; } 260 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();} 261 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); } 262}; 263 264template <> struct GraphTraits<const CallGraphNode*> { 265 typedef const CallGraphNode NodeType; 266 typedef NodeType::const_iterator ChildIteratorType; 267 268 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; } 269 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();} 270 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); } 271}; 272 273template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> { 274 static NodeType *getEntryNode(CallGraph *CGN) { 275 return CGN->getExternalCallingNode(); // Start at the external node! 276 } 277 typedef std::pair<const Function*, CallGraphNode*> PairTy; 278 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun; 279 280 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph 281 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator; 282 static nodes_iterator nodes_begin(CallGraph *CG) { 283 return map_iterator(CG->begin(), DerefFun(CGdereference)); 284 } 285 static nodes_iterator nodes_end (CallGraph *CG) { 286 return map_iterator(CG->end(), DerefFun(CGdereference)); 287 } 288 289 static CallGraphNode &CGdereference (std::pair<const Function*, 290 CallGraphNode*> P) { 291 return *P.second; 292 } 293}; 294template<> struct GraphTraits<const CallGraph*> : 295 public GraphTraits<const CallGraphNode*> { 296 static NodeType *getEntryNode(const CallGraph *CGN) { 297 return CGN->getExternalCallingNode(); 298 } 299 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph 300 typedef CallGraph::const_iterator nodes_iterator; 301 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); } 302 static nodes_iterator nodes_end (const CallGraph *CG) { return CG->end(); } 303}; 304 305// Make sure that any clients of this file link in PostDominators.cpp 306static IncludeFile 307CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub); 308 309} // End llvm namespace 310 311#endif 312