1 //===- CallGraph.cpp - Build a Module's call graph ------------------------===//
3 // This interface is used to build and manipulate a call graph, which is a very
4 // useful tool for interprocedural optimization.
6 // Every method in a module is represented as a node in the call graph. The
7 // callgraph node keeps track of which methods the are called by the method
8 // corresponding to the node.
10 // A call graph will contain nodes where the method that they correspond to is
11 // null. This 'external' node is used to represent control flow that is not
12 // represented (or analyzable) in the module. As such, the external node will
13 // have edges to methods with the following properties:
14 // 1. All methods in the module without internal linkage, since they could
15 // be called by methods outside of the our analysis capability.
16 // 2. All methods whose address is used for something more than a direct call,
17 // for example being stored into a memory location. Since they may be
18 // called by an unknown caller later, they must be tracked as such.
20 // Similarly, methods have a call edge to the external node iff:
21 // 1. The method is external, reflecting the fact that they could call
22 // anything without internal linkage or that has its address taken.
23 // 2. The method contains an indirect method call.
25 // As an extension in the future, there may be multiple nodes with a null
26 // method. These will be used when we can prove (through pointer analysis) that
27 // an indirect call site can call only a specific set of methods.
29 // Because of these properties, the CallGraph captures a conservative superset
30 // of all of the caller-callee relationships, which is useful for
33 // The CallGraph class also attempts to figure out what the root of the
34 // CallGraph is, which is currently does by looking for a method named 'main'.
35 // If no method named 'main' is found, the external node is used as the entry
36 // node, reflecting the fact that any method without internal linkage could
37 // be called into (which is common for libraries).
39 //===----------------------------------------------------------------------===//
41 #include "llvm/Analysis/CallGraph.h"
42 #include "llvm/Module.h"
43 #include "llvm/Method.h"
44 #include "llvm/iOther.h"
45 #include "llvm/iTerminators.h"
46 #include "Support/STLExtras.h"
50 AnalysisID CallGraph::ID(AnalysisID::create<CallGraph>());
52 // getNodeFor - Return the node for the specified method or create one if it
53 // does not already exist.
55 CallGraphNode *CallGraph::getNodeFor(Method *M) {
56 CallGraphNode *&CGN = MethodMap[M];
59 assert((!M || M->getParent() == Mod) && "Method not in current module!");
60 return CGN = new CallGraphNode(M);
63 // addToCallGraph - Add a method to the call graph, and link the node to all of
64 // the methods that it calls.
66 void CallGraph::addToCallGraph(Method *M) {
67 CallGraphNode *Node = getNodeFor(M);
69 // If this method has external linkage,
70 if (!M->hasInternalLinkage()) {
71 ExternalNode->addCalledMethod(Node);
73 // Found the entry point?
74 if (M->getName() == "main") {
76 Root = ExternalNode; // Found multiple external mains? Don't pick one.
78 Root = Node; // Found a main, keep track of it!
80 } else if (M->isExternal()) { // Not defined in this xlation unit?
81 Node->addCalledMethod(ExternalNode); // It could call anything...
84 // Loop over all of the users of the method... looking for callers...
86 for (Value::use_iterator I = M->use_begin(), E = M->use_end(); I != E; ++I) {
88 if (CallInst *CI = dyn_cast<CallInst>(U))
89 getNodeFor(CI->getParent()->getParent())->addCalledMethod(Node);
90 else if (InvokeInst *II = dyn_cast<InvokeInst>(U))
91 getNodeFor(II->getParent()->getParent())->addCalledMethod(Node);
92 else // Can't classify the user!
93 ExternalNode->addCalledMethod(Node);
96 // Look for an indirect method call...
97 for (Method::iterator BBI = M->begin(), BBE = M->end(); BBI != BBE; ++BBI) {
98 BasicBlock *BB = *BBI;
99 for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II){
100 Instruction *I = *II;
102 if (CallInst *CI = dyn_cast<CallInst>(I)) {
103 if (CI->getCalledMethod() == 0)
104 Node->addCalledMethod(ExternalNode);
105 } else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) {
106 if (II->getCalledMethod() == 0)
107 Node->addCalledMethod(ExternalNode);
113 bool CallGraph::run(Module *TheModule) {
117 ExternalNode = getNodeFor(0);
120 // Add every method to the call graph...
121 for_each(Mod->begin(), Mod->end(), bind_obj(this,&CallGraph::addToCallGraph));
123 // If we didn't find a main method, use the external call graph node
124 if (Root == 0) Root = ExternalNode;
129 void CallGraph::destroy() {
130 for (MethodMapTy::iterator I = MethodMap.begin(), E = MethodMap.end();
137 void WriteToOutput(const CallGraphNode *CGN, std::ostream &o) {
138 if (CGN->getMethod())
139 o << "Call graph node for method: '" << CGN->getMethod()->getName() <<"'\n";
141 o << "Call graph node null method:\n";
143 for (unsigned i = 0; i < CGN->size(); ++i)
144 if ((*CGN)[i]->getMethod())
145 o << " Calls method '" << (*CGN)[i]->getMethod()->getName() << "'\n";
147 o << " Calls external node\n";
151 void WriteToOutput(const CallGraph &CG, std::ostream &o) {
152 for (CallGraph::const_iterator I = CG.begin(), E = CG.end(); I != E; ++I)
157 //===----------------------------------------------------------------------===//
158 // Implementations of public modification methods
161 // Methods to keep a call graph up to date with a method that has been
164 void CallGraph::addMethodToModule(Method *Meth) {
165 assert(0 && "not implemented");
169 // removeMethodFromModule - Unlink the method from this module, returning it.
170 // Because this removes the method from the module, the call graph node is
171 // destroyed. This is only valid if the method does not call any other
172 // methods (ie, there are no edges in it's CGN). The easiest way to do this
173 // is to dropAllReferences before calling this.
175 Method *CallGraph::removeMethodFromModule(CallGraphNode *CGN) {
176 assert(CGN->CalledMethods.empty() && "Cannot remove method from call graph"
177 " if it references other methods!");
178 Method *M = CGN->getMethod(); // Get the method for the call graph node
179 delete CGN; // Delete the call graph node for this method
180 MethodMap.erase(M); // Remove the call graph node from the map
182 Mod->getMethodList().remove(M);