LLVM API Documentation

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 {
00068 protected:
00069   Module *Mod;              // The module this call graph represents
00070 
00071   typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
00072   FunctionMapTy FunctionMap;    // Map from a function to its node
00073 
00074 public:
00075   //===---------------------------------------------------------------------
00076   // Accessors...
00077   //
00078   typedef FunctionMapTy::iterator iterator;
00079   typedef FunctionMapTy::const_iterator const_iterator;
00080 
00081   /// getModule - Return the module the call graph corresponds to.
00082   ///
00083   Module &getModule() const { return *Mod; }
00084 
00085   inline       iterator begin()       { return FunctionMap.begin(); }
00086   inline       iterator end()         { return FunctionMap.end();   }
00087   inline const_iterator begin() const { return FunctionMap.begin(); }
00088   inline const_iterator end()   const { return FunctionMap.end();   }
00089 
00090   // Subscripting operators, return the call graph node for the provided
00091   // function
00092   inline const CallGraphNode *operator[](const Function *F) const {
00093     const_iterator I = FunctionMap.find(F);
00094     assert(I != FunctionMap.end() && "Function not in callgraph!");
00095     return I->second;
00096   }
00097   inline CallGraphNode *operator[](const Function *F) {
00098     const_iterator I = FunctionMap.find(F);
00099     assert(I != FunctionMap.end() && "Function not in callgraph!");
00100     return I->second;
00101   }
00102 
00103   //Returns the CallGraphNode which is used to represent undetermined calls 
00104   // into the callgraph.  Override this if you want behavioural inheritance.
00105   virtual CallGraphNode* getExternalCallingNode() const { return 0; }
00106   
00107   //Return the root/main method in the module, or some other root node, such
00108   // as the externalcallingnode.  Overload these if you behavioural 
00109   // inheritance.
00110   virtual CallGraphNode* getRoot() { return 0; }
00111   virtual const CallGraphNode* getRoot() const { return 0; }
00112   
00113   //===---------------------------------------------------------------------
00114   // Functions to keep a call graph up to date with a function that has been
00115   // modified.
00116   //
00117 
00118   /// removeFunctionFromModule - Unlink the function from this module, returning
00119   /// it.  Because this removes the function from the module, the call graph
00120   /// node is destroyed.  This is only valid if the function does not call any
00121   /// other functions (ie, there are no edges in it's CGN).  The easiest way to
00122   /// do this is to dropAllReferences before calling this.
00123   ///
00124   Function *removeFunctionFromModule(CallGraphNode *CGN);
00125   Function *removeFunctionFromModule(Function *F) {
00126     return removeFunctionFromModule((*this)[F]);
00127   }
00128 
00129   /// changeFunction - This method changes the function associated with this
00130   /// CallGraphNode, for use by transformations that need to change the
00131   /// prototype of a Function (thus they must create a new Function and move the
00132   /// old code over).
00133   void changeFunction(Function *OldF, Function *NewF);
00134 
00135   /// getOrInsertFunction - This method is identical to calling operator[], but
00136   /// it will insert a new CallGraphNode for the specified function if one does
00137   /// not already exist.
00138   CallGraphNode *getOrInsertFunction(const Function *F);
00139   
00140   //===---------------------------------------------------------------------
00141   // Pass infrastructure interface glue code...
00142   //
00143 protected:
00144   CallGraph() {}
00145   
00146 public:
00147   virtual ~CallGraph() { destroy(); }
00148 
00149   /// initialize - Call this method before calling other methods, 
00150   /// re/initializes the state of the CallGraph.
00151   ///
00152   void initialize(Module &M);
00153 
00154   virtual void print(std::ostream &o, const Module *M) const;
00155   void dump() const;
00156   
00157   // stub - dummy function, just ignore it
00158   static void stub();
00159 protected:
00160 
00161   // destroy - Release memory for the call graph
00162   virtual void destroy();
00163 };
00164 
00165 //===----------------------------------------------------------------------===//
00166 // CallGraphNode class definition
00167 //
00168 class CallGraphNode {
00169   Function *F;
00170   std::vector<CallGraphNode*> CalledFunctions;
00171 
00172   CallGraphNode(const CallGraphNode &);           // Do not implement
00173 public:
00174   //===---------------------------------------------------------------------
00175   // Accessor methods...
00176   //
00177 
00178   typedef std::vector<CallGraphNode*>::iterator iterator;
00179   typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
00180 
00181   // getFunction - Return the function that this call graph node represents...
00182   Function *getFunction() const { return F; }
00183 
00184   inline iterator begin() { return CalledFunctions.begin(); }
00185   inline iterator end()   { return CalledFunctions.end();   }
00186   inline const_iterator begin() const { return CalledFunctions.begin(); }
00187   inline const_iterator end()   const { return CalledFunctions.end();   }
00188   inline unsigned size() const { return CalledFunctions.size(); }
00189 
00190   // Subscripting operator - Return the i'th called function...
00191   //
00192   CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
00193 
00194   /// dump - Print out this call graph node.
00195   ///
00196   void dump() const;
00197   void print(std::ostream &OS) const;
00198 
00199   //===---------------------------------------------------------------------
00200   // Methods to keep a call graph up to date with a function that has been
00201   // modified
00202   //
00203 
00204   /// removeAllCalledFunctions - As the name implies, this removes all edges
00205   /// from this CallGraphNode to any functions it calls.
00206   void removeAllCalledFunctions() {
00207     CalledFunctions.clear();
00208   }
00209 
00210   /// addCalledFunction add a function to the list of functions called by this
00211   /// one.
00212   void addCalledFunction(CallGraphNode *M) {
00213     CalledFunctions.push_back(M);
00214   }
00215 
00216   /// removeCallEdgeTo - This method removes a *single* edge to the specified
00217   /// callee function.  Note that this method takes linear time, so it should be
00218   /// used sparingly.
00219   void removeCallEdgeTo(CallGraphNode *Callee);
00220 
00221   /// removeAnyCallEdgeTo - This method removes any call edges from this node to
00222   /// the specified callee function.  This takes more time to execute than
00223   /// removeCallEdgeTo, so it should not be used unless necessary.
00224   void removeAnyCallEdgeTo(CallGraphNode *Callee);
00225 
00226   friend class CallGraph;
00227 
00228   // CallGraphNode ctor - Create a node for the specified function...
00229   inline CallGraphNode(Function *f) : F(f) {}
00230 };
00231 
00232 //===----------------------------------------------------------------------===//
00233 // GraphTraits specializations for call graphs so that they can be treated as
00234 // graphs by the generic graph algorithms...
00235 //
00236 
00237 // Provide graph traits for tranversing call graphs using standard graph
00238 // traversals.
00239 template <> struct GraphTraits<CallGraphNode*> {
00240   typedef CallGraphNode NodeType;
00241   typedef NodeType::iterator ChildIteratorType;
00242 
00243   static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
00244   static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
00245   static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
00246 };
00247 
00248 template <> struct GraphTraits<const CallGraphNode*> {
00249   typedef const CallGraphNode NodeType;
00250   typedef NodeType::const_iterator ChildIteratorType;
00251 
00252   static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
00253   static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
00254   static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
00255 };
00256 
00257 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
00258   static NodeType *getEntryNode(CallGraph *CGN) {
00259     return CGN->getExternalCallingNode();  // Start at the external node!
00260   }
00261   typedef std::pair<const Function*, CallGraphNode*> PairTy;
00262   typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
00263 
00264   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
00265   typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
00266   static nodes_iterator nodes_begin(CallGraph *CG) {
00267     return map_iterator(CG->begin(), DerefFun(CGdereference));
00268   }
00269   static nodes_iterator nodes_end  (CallGraph *CG) {
00270     return map_iterator(CG->end(), DerefFun(CGdereference));
00271   }
00272 
00273   static CallGraphNode &CGdereference (std::pair<const Function*,
00274                                        CallGraphNode*> P) {
00275     return *P.second;
00276   }
00277 };
00278 
00279 template<> struct GraphTraits<const CallGraph*> :
00280   public GraphTraits<const CallGraphNode*> {
00281   static NodeType *getEntryNode(const CallGraph *CGN) {
00282     return CGN->getExternalCallingNode();
00283   }
00284   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
00285   typedef CallGraph::const_iterator nodes_iterator;
00286   static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
00287   static nodes_iterator nodes_end  (const CallGraph *CG) { return CG->end(); }
00288 };
00289 
00290 // Make sure that any clients of this file link in CallGraph.cpp
00291 static IncludeFile
00292 CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub);
00293 
00294 extern void BasicCallGraphStub();
00295 static IncludeFile HDR_INCLUDE_CALLGRAPH_CPP((void*)&BasicCallGraphStub);
00296 
00297 } // End llvm namespace
00298 
00299 #endif