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