lib/Analysis/IPA/CallGraph.cpp

   1 //===- CallGraph.cpp - Build a Module's call graph ------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the CallGraph class and provides the BasicCallGraph
  11 // default implementation.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Analysis/CallGraph.h"
  16 #include "llvm/Module.h"
  17 #include "llvm/Instructions.h"
  18 #include "llvm/IntrinsicInst.h"
  19 #include "llvm/Support/CallSite.h"
  20 #include "llvm/Support/Compiler.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 using namespace llvm;
  23
  24 namespace {
  25
  26 //===----------------------------------------------------------------------===//
  27 // BasicCallGraph class definition
  28 //
  29 class VISIBILITY_HIDDEN BasicCallGraph : public CallGraph, public ModulePass {
  30   // Root is root of the call graph, or the external node if a 'main' function
  31   // couldn't be found.
  32   //
  33   CallGraphNode *Root;
  34
  35   // ExternalCallingNode - This node has edges to all external functions and
  36   // those internal functions that have their address taken.
  37   CallGraphNode *ExternalCallingNode;
  38
  39   // CallsExternalNode - This node has edges to it from all functions making
  40   // indirect calls or calling an external function.
  41   CallGraphNode *CallsExternalNode;
  42
  43 public:
  44   static char ID; // Class identification, replacement for typeinfo
  45   BasicCallGraph() : ModulePass(&ID), Root(0),
  46     ExternalCallingNode(0), CallsExternalNode(0) {}
  47
  48   // runOnModule - Compute the call graph for the specified module.
  49   virtual bool runOnModule(Module &M) {
  50     CallGraph::initialize(M);
  51
  52     ExternalCallingNode = getOrInsertFunction(0);
  53     CallsExternalNode = new CallGraphNode(0);
  54     Root = 0;
  55
  56     // Add every function to the call graph.
  57     for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  58       addToCallGraph(I);
  59
  60     // If we didn't find a main function, use the external call graph node
  61     if (Root == 0) Root = ExternalCallingNode;
  62
  63     return false;
  64   }
  65
  66   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  67     AU.setPreservesAll();
  68   }
  69
  70   virtual void print(raw_ostream &OS, const Module *) const {
  71     OS << "CallGraph Root is: ";
  72     if (Function *F = getRoot()->getFunction())
  73       OS << F->getName() << "\n";
  74     else {
  75       OS << "<<null function: 0x" << getRoot() << ">>\n";
  76     }
  77
  78     CallGraph::print(OS, 0);
  79   }
  80
  81   virtual void releaseMemory() {
  82     destroy();
  83   }
  84
  85   CallGraphNode* getExternalCallingNode() const { return ExternalCallingNode; }
  86   CallGraphNode* getCallsExternalNode()   const { return CallsExternalNode; }
  87
  88   // getRoot - Return the root of the call graph, which is either main, or if
  89   // main cannot be found, the external node.
  90   //
  91   CallGraphNode *getRoot()             { return Root; }
  92   const CallGraphNode *getRoot() const { return Root; }
  93
  94 private:
  95   //===---------------------------------------------------------------------
  96   // Implementation of CallGraph construction
  97   //
  98
  99   // addToCallGraph - Add a function to the call graph, and link the node to all
 100   // of the functions that it calls.
 101   //
 102   void addToCallGraph(Function *F) {
 103     CallGraphNode *Node = getOrInsertFunction(F);
 104
 105     // If this function has external linkage, anything could call it.
 106     if (!F->hasLocalLinkage()) {
 107       ExternalCallingNode->addCalledFunction(CallSite(), Node);
 108
 109       // Found the entry point?
 110       if (F->getName() == "main") {
 111         if (Root)    // Found multiple external mains?  Don't pick one.
 112           Root = ExternalCallingNode;
 113         else
 114           Root = Node;          // Found a main, keep track of it!
 115       }
 116     }
 117
 118     // Loop over all of the users of the function, looking for non-call uses.
 119     for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I)
 120       if ((!isa<CallInst>(I) && !isa<InvokeInst>(I))
 121           || !CallSite(cast<Instruction>(I)).isCallee(I)) {
 122         // Not a call, or being used as a parameter rather than as the callee.
 123         ExternalCallingNode->addCalledFunction(CallSite(), Node);
 124         break;
 125       }
 126
 127     // If this function is not defined in this translation unit, it could call
 128     // anything.
 129     if (F->isDeclaration() && !F->isIntrinsic())
 130       Node->addCalledFunction(CallSite(), CallsExternalNode);
 131
 132     // Look for calls by this function.
 133     for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
 134       for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
 135            II != IE; ++II) {
 136         CallSite CS = CallSite::get(II);
 137         if (CS.getInstruction() && !isa<DbgInfoIntrinsic>(II)) {
 138           const Function *Callee = CS.getCalledFunction();
 139           if (Callee)
 140             Node->addCalledFunction(CS, getOrInsertFunction(Callee));
 141           else
 142             Node->addCalledFunction(CS, CallsExternalNode);
 143         }
 144       }
 145   }
 146
 147   //
 148   // destroy - Release memory for the call graph
 149   virtual void destroy() {
 150     /// CallsExternalNode is not in the function map, delete it explicitly.
 151     delete CallsExternalNode;
 152     CallsExternalNode = 0;
 153     CallGraph::destroy();
 154   }
 155 };
 156
 157 } //End anonymous namespace
 158
 159 static RegisterAnalysisGroup<CallGraph> X("Call Graph");
 160 static RegisterPass<BasicCallGraph>
 161 Y("basiccg", "Basic CallGraph Construction", false, true);
 162 static RegisterAnalysisGroup<CallGraph, true> Z(Y);
 163
 164 char CallGraph::ID = 0;
 165 char BasicCallGraph::ID = 0;
 166
 167 void CallGraph::initialize(Module &M) {
 168   Mod = &M;
 169 }
 170
 171 void CallGraph::destroy() {
 172   if (FunctionMap.empty()) return;
 173
 174   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
 175       I != E; ++I)
 176     delete I->second;
 177   FunctionMap.clear();
 178 }
 179
 180 void CallGraph::print(raw_ostream &OS, Module*) const {
 181   for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
 182     I->second->print(OS);
 183 }
 184 void CallGraph::dump() const {
 185   print(errs(), 0);
 186 }
 187
 188 //===----------------------------------------------------------------------===//
 189 // Implementations of public modification methods
 190 //
 191
 192 // removeFunctionFromModule - Unlink the function from this module, returning
 193 // it.  Because this removes the function from the module, the call graph node
 194 // is destroyed.  This is only valid if the function does not call any other
 195 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
 196 // is to dropAllReferences before calling this.
 197 //
 198 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
 199   assert(CGN->empty() && "Cannot remove function from call "
 200          "graph if it references other functions!");
 201   Function *F = CGN->getFunction(); // Get the function for the call graph node
 202   delete CGN;                       // Delete the call graph node for this func
 203   FunctionMap.erase(F);             // Remove the call graph node from the map
 204
 205   Mod->getFunctionList().remove(F);
 206   return F;
 207 }
 208
 209 // getOrInsertFunction - This method is identical to calling operator[], but
 210 // it will insert a new CallGraphNode for the specified function if one does
 211 // not already exist.
 212 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
 213   CallGraphNode *&CGN = FunctionMap[F];
 214   if (CGN) return CGN;
 215
 216   assert((!F || F->getParent() == Mod) && "Function not in current module!");
 217   return CGN = new CallGraphNode(const_cast<Function*>(F));
 218 }
 219
 220 void CallGraphNode::print(raw_ostream &OS) const {
 221   if (Function *F = getFunction())
 222     OS << "Call graph node for function: '" << F->getName() << "'";
 223   else
 224     OS << "Call graph node <<null function>>";
 225
 226   OS << "<<0x" << this << ">>  #uses=" << getNumReferences() << '\n';
 227
 228   for (const_iterator I = begin(), E = end(); I != E; ++I)
 229     if (Function *FI = I->second->getFunction())
 230       OS << "  Calls function '" << FI->getName() <<"'\n";
 231   else
 232     OS << "  Calls external node\n";
 233   OS << "\n";
 234 }
 235
 236 void CallGraphNode::dump() const { print(errs()); }
 237
 238 /// removeCallEdgeFor - This method removes the edge in the node for the
 239 /// specified call site.  Note that this method takes linear time, so it
 240 /// should be used sparingly.
 241 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
 242   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 243     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 244     if (I->first == CS.getInstruction()) {
 245       I->second->DropRef();
 246       *I = CalledFunctions.back();
 247       CalledFunctions.pop_back();
 248       return;
 249     }
 250   }
 251 }
 252
 253
 254 // removeAnyCallEdgeTo - This method removes any call edges from this node to
 255 // the specified callee function.  This takes more time to execute than
 256 // removeCallEdgeTo, so it should not be used unless necessary.
 257 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
 258   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
 259     if (CalledFunctions[i].second == Callee) {
 260       Callee->DropRef();
 261       CalledFunctions[i] = CalledFunctions.back();
 262       CalledFunctions.pop_back();
 263       --i; --e;
 264     }
 265 }
 266
 267 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
 268 /// from this node to the specified callee function.
 269 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
 270   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 271     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
 272     CallRecord &CR = *I;
 273     if (CR.second == Callee && CR.first == 0) {
 274       Callee->DropRef();
 275       *I = CalledFunctions.back();
 276       CalledFunctions.pop_back();
 277       return;
 278     }
 279   }
 280 }
 281
 282 /// replaceCallEdge - This method replaces the edge in the node for the
 283 /// specified call site with a new one.  Note that this method takes linear
 284 /// time, so it should be used sparingly.
 285 void CallGraphNode::replaceCallEdge(CallSite CS,
 286                                     CallSite NewCS, CallGraphNode *NewNode){
 287   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 288     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 289     if (I->first == CS.getInstruction()) {
 290       I->second->DropRef();
 291       I->first = NewCS.getInstruction();
 292       I->second = NewNode;
 293       NewNode->AddRef();
 294       return;
 295     }
 296   }
 297 }
 298
 299 // Enuse that users of CallGraph.h also link with this file
 300 DEFINING_FILE_FOR(CallGraph)