CallGraph.h revision 1570cb14d7e1ce8041533baeeefcb19cee7a414c
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 // Accessors... 89 // 90 typedef FunctionMapTy::iterator iterator; 91 typedef FunctionMapTy::const_iterator const_iterator; 92 93 CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; } 94 CallGraphNode *getCallsExternalNode() const { return CallsExternalNode; } 95 96 // getRoot - Return the root of the call graph, which is either main, or if 97 // main cannot be found, the external node. 98 // 99 CallGraphNode *getRoot() { return Root; } 100 const CallGraphNode *getRoot() const { return Root; } 101 102 /// getModule - Return the module the call graph corresponds to. 103 /// 104 Module &getModule() const { return *Mod; } 105 106 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(); } 110 111 112 // Subscripting operators, return the call graph node for the provided 113 // function 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!"); 117 return I->second; 118 } 119 inline CallGraphNode *operator[](const Function *F) { 120 const_iterator I = FunctionMap.find(F); 121 assert(I != FunctionMap.end() && "Function not in callgraph!"); 122 return I->second; 123 } 124 125 //===--------------------------------------------------------------------- 126 // Functions to keep a call graph up to date with a function that has been 127 // modified 128 // 129 void addFunctionToModule(Function *F); 130 131 132 // 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. 137 // 138 Function *removeFunctionFromModule(CallGraphNode *CGN); 139 Function *removeFunctionFromModule(Function *F) { 140 return removeFunctionFromModule((*this)[F]); 141 } 142 143 144 //===--------------------------------------------------------------------- 145 // Pass infrastructure interface glue code... 146 // 147 CallGraph() : Root(0), CallsExternalNode(0) {} 148 ~CallGraph() { destroy(); } 149 150 // run - Compute the call graph for the specified module. 151 virtual bool run(Module &M); 152 153 // getAnalysisUsage - This obviously provides a call graph 154 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 155 AU.setPreservesAll(); 156 } 157 158 // releaseMemory - Data structures can be large, so free memory aggressively. 159 virtual void releaseMemory() { 160 destroy(); 161 } 162 163 /// 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. 166 /// 167 void print(std::ostream &o, const Module *M) const; 168 169 // stub - dummy function, just ignore it 170 static void stub(); 171private: 172 //===--------------------------------------------------------------------- 173 // Implementation of CallGraph construction 174 // 175 176 // getNodeFor - Return the node for the specified function or create one if it 177 // does not already exist. 178 // 179 CallGraphNode *getNodeFor(Function *F); 180 181 // addToCallGraph - Add a function to the call graph, and link the node to all 182 // of the functions that it calls. 183 // 184 void addToCallGraph(Function *F); 185 186 // destroy - Release memory for the call graph 187 void destroy(); 188}; 189 190 191//===----------------------------------------------------------------------===// 192// CallGraphNode class definition 193// 194class CallGraphNode { 195 Function *F; 196 std::vector<CallGraphNode*> CalledFunctions; 197 198 CallGraphNode(const CallGraphNode &); // Do not implement 199public: 200 //===--------------------------------------------------------------------- 201 // Accessor methods... 202 // 203 204 typedef std::vector<CallGraphNode*>::iterator iterator; 205 typedef std::vector<CallGraphNode*>::const_iterator const_iterator; 206 207 // getFunction - Return the function that this call graph node represents... 208 Function *getFunction() const { return F; } 209 210 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(); } 215 216 // Subscripting operator - Return the i'th called function... 217 // 218 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];} 219 220 221 //===--------------------------------------------------------------------- 222 // Methods to keep a call graph up to date with a function that has been 223 // modified 224 // 225 226 void removeAllCalledFunctions() { 227 CalledFunctions.clear(); 228 } 229 230 // addCalledFunction add a function to the list of functions called by this 231 // one 232 void addCalledFunction(CallGraphNode *M) { 233 CalledFunctions.push_back(M); 234 } 235 236 void removeCallEdgeTo(CallGraphNode *Callee); 237 238private: // Stuff to construct the node, used by CallGraph 239 friend class CallGraph; 240 241 // CallGraphNode ctor - Create a node for the specified function... 242 inline CallGraphNode(Function *f) : F(f) {} 243}; 244 245 246 247//===----------------------------------------------------------------------===// 248// GraphTraits specializations for call graphs so that they can be treated as 249// graphs by the generic graph algorithms... 250// 251 252// Provide graph traits for tranversing call graphs using standard graph 253// traversals. 254template <> struct GraphTraits<CallGraphNode*> { 255 typedef CallGraphNode NodeType; 256 typedef NodeType::iterator ChildIteratorType; 257 258 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(); } 261}; 262 263template <> struct GraphTraits<const CallGraphNode*> { 264 typedef const CallGraphNode NodeType; 265 typedef NodeType::const_iterator ChildIteratorType; 266 267 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(); } 270}; 271 272template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> { 273 static NodeType *getEntryNode(CallGraph *CGN) { 274 return CGN->getExternalCallingNode(); // Start at the external node! 275 } 276 typedef std::pair<const Function*, CallGraphNode*> PairTy; 277 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun; 278 279 // 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)); 283 } 284 static nodes_iterator nodes_end (CallGraph *CG) { 285 return map_iterator(CG->end(), DerefFun(CGdereference)); 286 } 287 288 static CallGraphNode &CGdereference (std::pair<const Function*, 289 CallGraphNode*> P) { 290 return *P.second; 291 } 292}; 293template<> struct GraphTraits<const CallGraph*> : 294 public GraphTraits<const CallGraphNode*> { 295 static NodeType *getEntryNode(const CallGraph *CGN) { 296 return CGN->getExternalCallingNode(); 297 } 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(); } 302}; 303 304// Make sure that any clients of this file link in PostDominators.cpp 305static IncludeFile 306CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub); 307 308} // End llvm namespace 309 310#endif 311