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CallGraph.h

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00001 //===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This interface is used to build and manipulate a call graph, which is a very 
00011 // useful tool for interprocedural optimization.
00012 //
00013 // Every function in a module is represented as a node in the call graph.  The
00014 // callgraph node keeps track of which functions the are called by the function
00015 // corresponding to the node.
00016 //
00017 // A call graph may contain nodes where the function that they correspond to is
00018 // null.  These 'external' nodes are used to represent control flow that is not
00019 // represented (or analyzable) in the module.  In particular, this analysis
00020 // builds one external node such that:
00021 //   1. All functions in the module without internal linkage will have edges
00022 //      from this external node, indicating that they could be called by
00023 //      functions outside of the module.
00024 //   2. All functions whose address is used for something more than a direct
00025 //      call, for example being stored into a memory location will also have an
00026 //      edge from this external node.  Since they may be called by an unknown
00027 //      caller later, they must be tracked as such.
00028 //
00029 // There is a second external node added for calls that leave this module.
00030 // Functions have a call edge to the external node iff:
00031 //   1. The function is external, reflecting the fact that they could call
00032 //      anything without internal linkage or that has its address taken.
00033 //   2. The function contains an indirect function call.
00034 //
00035 // As an extension in the future, there may be multiple nodes with a null
00036 // function.  These will be used when we can prove (through pointer analysis)
00037 // that an indirect call site can call only a specific set of functions.
00038 //
00039 // Because of these properties, the CallGraph captures a conservative superset
00040 // of all of the caller-callee relationships, which is useful for
00041 // transformations.
00042 //
00043 // The CallGraph class also attempts to figure out what the root of the
00044 // CallGraph is, which it currently does by looking for a function named 'main'.
00045 // If no function named 'main' is found, the external node is used as the entry
00046 // node, reflecting the fact that any function without internal linkage could
00047 // be called into (which is common for libraries).
00048 //
00049 //===----------------------------------------------------------------------===//
00050 
00051 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
00052 #define LLVM_ANALYSIS_CALLGRAPH_H
00053 
00054 #include "llvm/ADT/GraphTraits.h"
00055 #include "llvm/ADT/STLExtras.h"
00056 #include "llvm/Pass.h"
00057 
00058 namespace llvm {
00059 
00060 class Function;
00061 class Module;
00062 class CallGraphNode;
00063 
00064 //===----------------------------------------------------------------------===//
00065 // CallGraph class definition
00066 //
00067 class CallGraph : public ModulePass {
00068   Module *Mod;              // The module this call graph represents
00069 
00070   typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
00071   FunctionMapTy FunctionMap;    // Map from a function to its node
00072 
00073   // Root is root of the call graph, or the external node if a 'main' function
00074   // couldn't be found.
00075   //
00076   CallGraphNode *Root;
00077 
00078   // ExternalCallingNode - This node has edges to all external functions and
00079   // those internal functions that have their address taken.
00080   CallGraphNode *ExternalCallingNode;
00081 
00082   // CallsExternalNode - This node has edges to it from all functions making
00083   // indirect calls or calling an external function.
00084   CallGraphNode *CallsExternalNode;
00085 
00086 public:
00087   //===---------------------------------------------------------------------
00088   // Accessors...
00089   //
00090   typedef FunctionMapTy::iterator iterator;
00091   typedef FunctionMapTy::const_iterator const_iterator;
00092 
00093   CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
00094   CallGraphNode *getCallsExternalNode()   const { return CallsExternalNode; }
00095 
00096   // getRoot - Return the root of the call graph, which is either main, or if
00097   // main cannot be found, the external node.
00098   //
00099         CallGraphNode *getRoot()       { return Root; }
00100   const CallGraphNode *getRoot() const { return Root; }
00101 
00102   /// getModule - Return the module the call graph corresponds to.
00103   ///
00104   Module &getModule() const { return *Mod; }
00105 
00106   inline       iterator begin()       { return FunctionMap.begin(); }
00107   inline       iterator end()         { return FunctionMap.end();   }
00108   inline const_iterator begin() const { return FunctionMap.begin(); }
00109   inline const_iterator end()   const { return FunctionMap.end();   }
00110 
00111 
00112   // Subscripting operators, return the call graph node for the provided
00113   // function
00114   inline const CallGraphNode *operator[](const Function *F) const {
00115     const_iterator I = FunctionMap.find(F);
00116     assert(I != FunctionMap.end() && "Function not in callgraph!");
00117     return I->second;
00118   }
00119   inline CallGraphNode *operator[](const Function *F) {
00120     const_iterator I = FunctionMap.find(F);
00121     assert(I != FunctionMap.end() && "Function not in callgraph!");
00122     return I->second;
00123   }
00124 
00125   //===---------------------------------------------------------------------
00126   // Functions to keep a call graph up to date with a function that has been
00127   // modified.
00128   //
00129 
00130   /// removeFunctionFromModule - Unlink the function from this module, returning
00131   /// it.  Because this removes the function from the module, the call graph
00132   /// node is destroyed.  This is only valid if the function does not call any
00133   /// other functions (ie, there are no edges in it's CGN).  The easiest way to
00134   /// do this is to dropAllReferences before calling this.
00135   ///
00136   Function *removeFunctionFromModule(CallGraphNode *CGN);
00137   Function *removeFunctionFromModule(Function *F) {
00138     return removeFunctionFromModule((*this)[F]);
00139   }
00140 
00141   /// changeFunction - This method changes the function associated with this
00142   /// CallGraphNode, for use by transformations that need to change the
00143   /// prototype of a Function (thus they must create a new Function and move the
00144   /// old code over).
00145   void changeFunction(Function *OldF, Function *NewF);
00146 
00147   //===---------------------------------------------------------------------
00148   // Pass infrastructure interface glue code...
00149   //
00150   CallGraph() : Root(0), CallsExternalNode(0) {}
00151   ~CallGraph() { destroy(); }
00152 
00153   // runOnModule - Compute the call graph for the specified module.
00154   virtual bool runOnModule(Module &M);
00155 
00156   // getAnalysisUsage - This obviously provides a call graph
00157   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
00158     AU.setPreservesAll();
00159   }
00160 
00161   // releaseMemory - Data structures can be large, so free memory aggressively.
00162   virtual void releaseMemory() {
00163     destroy();
00164   }
00165 
00166   /// Print the types found in the module.  If the optional Module parameter is
00167   /// passed in, then the types are printed symbolically if possible, using the
00168   /// symbol table from the module.
00169   ///
00170   void print(std::ostream &o, const Module *M) const;
00171 
00172   /// dump - Print out this call graph.
00173   ///
00174   void dump() const;
00175 
00176   // stub - dummy function, just ignore it
00177   static void stub();
00178 private:
00179   //===---------------------------------------------------------------------
00180   // Implementation of CallGraph construction
00181   //
00182 
00183   // getNodeFor - Return the node for the specified function or create one if it
00184   // does not already exist.
00185   //
00186   CallGraphNode *getNodeFor(Function *F);
00187 
00188   // addToCallGraph - Add a function to the call graph, and link the node to all
00189   // of the functions that it calls.
00190   //
00191   void addToCallGraph(Function *F);
00192 
00193   // destroy - Release memory for the call graph
00194   void destroy();
00195 };
00196 
00197 
00198 //===----------------------------------------------------------------------===//
00199 // CallGraphNode class definition
00200 //
00201 class CallGraphNode {
00202   Function *F;
00203   std::vector<CallGraphNode*> CalledFunctions;
00204 
00205   CallGraphNode(const CallGraphNode &);           // Do not implement
00206 public:
00207   //===---------------------------------------------------------------------
00208   // Accessor methods...
00209   //
00210 
00211   typedef std::vector<CallGraphNode*>::iterator iterator;
00212   typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
00213 
00214   // getFunction - Return the function that this call graph node represents...
00215   Function *getFunction() const { return F; }
00216 
00217   inline iterator begin() { return CalledFunctions.begin(); }
00218   inline iterator end()   { return CalledFunctions.end();   }
00219   inline const_iterator begin() const { return CalledFunctions.begin(); }
00220   inline const_iterator end()   const { return CalledFunctions.end();   }
00221   inline unsigned size() const { return CalledFunctions.size(); }
00222 
00223   // Subscripting operator - Return the i'th called function...
00224   //
00225   CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
00226 
00227   /// dump - Print out this call graph node.
00228   ///
00229   void dump() const;
00230   void print(std::ostream &OS) const;
00231 
00232   //===---------------------------------------------------------------------
00233   // Methods to keep a call graph up to date with a function that has been
00234   // modified
00235   //
00236 
00237   /// removeAllCalledFunctions - As the name implies, this removes all edges
00238   /// from this CallGraphNode to any functions it calls.
00239   void removeAllCalledFunctions() {
00240     CalledFunctions.clear();
00241   }
00242 
00243   /// addCalledFunction add a function to the list of functions called by this
00244   /// one.
00245   void addCalledFunction(CallGraphNode *M) {
00246     CalledFunctions.push_back(M);
00247   }
00248 
00249   /// removeCallEdgeTo - This method removes a *single* edge to the specified
00250   /// callee function.  Note that this method takes linear time, so it should be
00251   /// used sparingly.
00252   void removeCallEdgeTo(CallGraphNode *Callee);
00253 
00254   /// removeAnyCallEdgeTo - This method removes any call edges from this node to
00255   /// the specified callee function.  This takes more time to execute than
00256   /// removeCallEdgeTo, so it should not be used unless necessary.
00257   void removeAnyCallEdgeTo(CallGraphNode *Callee);
00258 
00259 private:                    // Stuff to construct the node, used by CallGraph
00260   friend class CallGraph;
00261 
00262   // CallGraphNode ctor - Create a node for the specified function...
00263   inline CallGraphNode(Function *f) : F(f) {}
00264 };
00265 
00266 
00267 
00268 //===----------------------------------------------------------------------===//
00269 // GraphTraits specializations for call graphs so that they can be treated as
00270 // graphs by the generic graph algorithms...
00271 //
00272 
00273 // Provide graph traits for tranversing call graphs using standard graph
00274 // traversals.
00275 template <> struct GraphTraits<CallGraphNode*> {
00276   typedef CallGraphNode NodeType;
00277   typedef NodeType::iterator ChildIteratorType;
00278 
00279   static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
00280   static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
00281   static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
00282 };
00283 
00284 template <> struct GraphTraits<const CallGraphNode*> {
00285   typedef const CallGraphNode NodeType;
00286   typedef NodeType::const_iterator ChildIteratorType;
00287 
00288   static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
00289   static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
00290   static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
00291 };
00292 
00293 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
00294   static NodeType *getEntryNode(CallGraph *CGN) {
00295     return CGN->getExternalCallingNode();  // Start at the external node!
00296   }
00297   typedef std::pair<const Function*, CallGraphNode*> PairTy;
00298   typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
00299 
00300   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
00301   typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
00302   static nodes_iterator nodes_begin(CallGraph *CG) {
00303     return map_iterator(CG->begin(), DerefFun(CGdereference));
00304   }
00305   static nodes_iterator nodes_end  (CallGraph *CG) {
00306     return map_iterator(CG->end(), DerefFun(CGdereference));
00307   }
00308 
00309   static CallGraphNode &CGdereference (std::pair<const Function*,
00310                                        CallGraphNode*> P) {
00311     return *P.second;
00312   }
00313 };
00314 template<> struct GraphTraits<const CallGraph*> :
00315   public GraphTraits<const CallGraphNode*> {
00316   static NodeType *getEntryNode(const CallGraph *CGN) {
00317     return CGN->getExternalCallingNode();
00318   }
00319   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
00320   typedef CallGraph::const_iterator nodes_iterator;
00321   static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
00322   static nodes_iterator nodes_end  (const CallGraph *CG) { return CG->end(); }
00323 };
00324 
00325 // Make sure that any clients of this file link in PostDominators.cpp
00326 static IncludeFile
00327 CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub);
00328 
00329 } // End llvm namespace
00330 
00331 #endif