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 will contain nodes where the function that they correspond to is
18 // null. This 'external' node is used to represent control flow that is not
19 // represented (or analyzable) in the module. As such, the external node will
20 // have edges to functions with the following properties:
21 // 1. All functions in the module without internal linkage, since they could
22 // be called by functions outside of the our analysis capability.
23 // 2. All functions whose address is used for something more than a direct
24 // call, for example being stored into a memory location. Since they may
25 // be called by an unknown caller later, they must be tracked as such.
27 // Similarly, functions have a call edge to the external node iff:
28 // 1. The function is external, reflecting the fact that they could call
29 // anything without internal linkage or that has its address taken.
30 // 2. The function contains an indirect function call.
32 // As an extension in the future, there may be multiple nodes with a null
33 // function. These will be used when we can prove (through pointer analysis)
34 // that an indirect call site can call only a specific set of functions.
36 // Because of these properties, the CallGraph captures a conservative superset
37 // of all of the caller-callee relationships, which is useful for
40 // The CallGraph class also attempts to figure out what the root of the
41 // CallGraph is, which is currently does by looking for a function named 'main'.
42 // If no function named 'main' is found, the external node is used as the entry
43 // node, reflecting the fact that any function without internal linkage could
44 // be called into (which is common for libraries).
46 //===----------------------------------------------------------------------===//
48 #ifndef LLVM_ANALYSIS_CALLGRAPH_H
49 #define LLVM_ANALYSIS_CALLGRAPH_H
51 #include "Support/GraphTraits.h"
52 #include "Support/STLExtras.h"
53 #include "llvm/Pass.h"
58 //===----------------------------------------------------------------------===//
59 // CallGraph class definition
61 class CallGraph : public Pass {
62 Module *Mod; // The module this call graph represents
64 typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
65 FunctionMapTy FunctionMap; // Map from a function to its node
67 // Root is root of the call graph, or the external node if a 'main' function
68 // couldn't be found. ExternalNode is equivalent to (*this)[0].
70 CallGraphNode *Root, *ExternalNode;
73 //===---------------------------------------------------------------------
76 typedef FunctionMapTy::iterator iterator;
77 typedef FunctionMapTy::const_iterator const_iterator;
79 // getExternalNode - Return the node that points to all functions that are
80 // accessable from outside of the current program.
82 CallGraphNode *getExternalNode() { return ExternalNode; }
83 const CallGraphNode *getExternalNode() const { return ExternalNode; }
85 // getRoot - Return the root of the call graph, which is either main, or if
86 // main cannot be found, the external node.
88 CallGraphNode *getRoot() { return Root; }
89 const CallGraphNode *getRoot() const { return Root; }
91 inline iterator begin() { return FunctionMap.begin(); }
92 inline iterator end() { return FunctionMap.end(); }
93 inline const_iterator begin() const { return FunctionMap.begin(); }
94 inline const_iterator end() const { return FunctionMap.end(); }
97 // Subscripting operators, return the call graph node for the provided
99 inline const CallGraphNode *operator[](const Function *F) const {
100 const_iterator I = FunctionMap.find(F);
101 assert(I != FunctionMap.end() && "Function not in callgraph!");
104 inline CallGraphNode *operator[](const Function *F) {
105 const_iterator I = FunctionMap.find(F);
106 assert(I != FunctionMap.end() && "Function not in callgraph!");
110 //===---------------------------------------------------------------------
111 // Functions to keep a call graph up to date with a function that has been
114 void addFunctionToModule(Function *F);
117 // removeFunctionFromModule - Unlink the function from this module, returning
118 // it. Because this removes the function from the module, the call graph node
119 // is destroyed. This is only valid if the function does not call any other
120 // functions (ie, there are no edges in it's CGN). The easiest way to do this
121 // is to dropAllReferences before calling this.
123 Function *removeFunctionFromModule(CallGraphNode *CGN);
124 Function *removeFunctionFromModule(Function *F) {
125 return removeFunctionFromModule((*this)[F]);
129 //===---------------------------------------------------------------------
130 // Pass infrastructure interface glue code...
132 CallGraph() : Root(0) {}
133 ~CallGraph() { destroy(); }
135 // run - Compute the call graph for the specified module.
136 virtual bool run(Module &M);
138 // getAnalysisUsage - This obviously provides a call graph
139 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
140 AU.setPreservesAll();
143 // releaseMemory - Data structures can be large, so free memory aggressively.
144 virtual void releaseMemory() {
148 /// Print the types found in the module. If the optional Module parameter is
149 /// passed in, then the types are printed symbolically if possible, using the
150 /// symbol table from the module.
152 void print(std::ostream &o, const Module *M) const;
154 // stub - dummy function, just ignore it
157 //===---------------------------------------------------------------------
158 // Implementation of CallGraph construction
161 // getNodeFor - Return the node for the specified function or create one if it
162 // does not already exist.
164 CallGraphNode *getNodeFor(Function *F);
166 // addToCallGraph - Add a function to the call graph, and link the node to all
167 // of the functions that it calls.
169 void addToCallGraph(Function *F);
171 // destroy - Release memory for the call graph
176 //===----------------------------------------------------------------------===//
177 // CallGraphNode class definition
179 class CallGraphNode {
181 std::vector<CallGraphNode*> CalledFunctions;
183 CallGraphNode(const CallGraphNode &); // Do not implement
185 //===---------------------------------------------------------------------
186 // Accessor methods...
189 typedef std::vector<CallGraphNode*>::iterator iterator;
190 typedef std::vector<CallGraphNode*>::const_iterator const_iterator;
192 // getFunction - Return the function that this call graph node represents...
193 Function *getFunction() const { return F; }
195 inline iterator begin() { return CalledFunctions.begin(); }
196 inline iterator end() { return CalledFunctions.end(); }
197 inline const_iterator begin() const { return CalledFunctions.begin(); }
198 inline const_iterator end() const { return CalledFunctions.end(); }
199 inline unsigned size() const { return CalledFunctions.size(); }
201 // Subscripting operator - Return the i'th called function...
203 CallGraphNode *operator[](unsigned i) const { return CalledFunctions[i];}
206 //===---------------------------------------------------------------------
207 // Methods to keep a call graph up to date with a function that has been
211 void removeAllCalledFunctions() {
212 CalledFunctions.clear();
215 private: // Stuff to construct the node, used by CallGraph
216 friend class CallGraph;
218 // CallGraphNode ctor - Create a node for the specified function...
219 inline CallGraphNode(Function *f) : F(f) {}
221 // addCalledFunction add a function to the list of functions called by this
223 void addCalledFunction(CallGraphNode *M) {
224 CalledFunctions.push_back(M);
230 //===----------------------------------------------------------------------===//
231 // GraphTraits specializations for call graphs so that they can be treated as
232 // graphs by the generic graph algorithms...
235 // Provide graph traits for tranversing call graphs using standard graph
237 template <> struct GraphTraits<CallGraphNode*> {
238 typedef CallGraphNode NodeType;
239 typedef NodeType::iterator ChildIteratorType;
241 static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
242 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
243 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
246 template <> struct GraphTraits<const CallGraphNode*> {
247 typedef const CallGraphNode NodeType;
248 typedef NodeType::const_iterator ChildIteratorType;
250 static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
251 static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
252 static inline ChildIteratorType child_end (NodeType *N) { return N->end(); }
255 template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
256 static NodeType *getEntryNode(CallGraph *CGN) {
257 return CGN->getExternalNode(); // Start at the external node!
259 typedef std::pair<const Function*, CallGraphNode*> PairTy;
260 typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
262 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
263 typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
264 static nodes_iterator nodes_begin(CallGraph *CG) {
265 return map_iterator(CG->begin(), DerefFun(CGdereference));
267 static nodes_iterator nodes_end (CallGraph *CG) {
268 return map_iterator(CG->end(), DerefFun(CGdereference));
271 static CallGraphNode &CGdereference (std::pair<const Function*,
276 template<> struct GraphTraits<const CallGraph*> :
277 public GraphTraits<const CallGraphNode*> {
278 static NodeType *getEntryNode(const CallGraph *CGN) {
279 return CGN->getExternalNode();
281 // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
282 typedef CallGraph::const_iterator nodes_iterator;
283 static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
284 static nodes_iterator nodes_end (const CallGraph *CG) { return CG->end(); }
287 // Make sure that any clients of this file link in PostDominators.cpp
289 CALLGRAPH_INCLUDE_FILE((void*)&CallGraph::stub);