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/Debug.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 using namespace llvm;
  23
  24 namespace {
  25
  26 //===----------------------------------------------------------------------===//
  27 // BasicCallGraph class definition
  28 //
  29 class BasicCallGraph : public ModulePass, public CallGraph {
  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       initializeBasicCallGraphPass(*PassRegistry::getPassRegistry());
  48     }
  49
  50   // runOnModule - Compute the call graph for the specified module.
  51   virtual bool runOnModule(Module &M) {
  52     CallGraph::initialize(M);
  53
  54     ExternalCallingNode = getOrInsertFunction(0);
  55     CallsExternalNode = new CallGraphNode(0);
  56     Root = 0;
  57
  58     // Add every function to the call graph.
  59     for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  60       addToCallGraph(I);
  61
  62     // If we didn't find a main function, use the external call graph node
  63     if (Root == 0) Root = ExternalCallingNode;
  64
  65     return false;
  66   }
  67
  68   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  69     AU.setPreservesAll();
  70   }
  71
  72   virtual void print(raw_ostream &OS, const Module *) const {
  73     OS << "CallGraph Root is: ";
  74     if (Function *F = getRoot()->getFunction())
  75       OS << F->getName() << "\n";
  76     else {
  77       OS << "<<null function: 0x" << getRoot() << ">>\n";
  78     }
  79
  80     CallGraph::print(OS, 0);
  81   }
  82
  83   virtual void releaseMemory() {
  84     destroy();
  85   }
  86
  87   /// getAdjustedAnalysisPointer - This method is used when a pass implements
  88   /// an analysis interface through multiple inheritance.  If needed, it should
  89   /// override this to adjust the this pointer as needed for the specified pass
  90   /// info.
  91   virtual void *getAdjustedAnalysisPointer(AnalysisID PI) {
  92     if (PI == &CallGraph::ID)
  93       return (CallGraph*)this;
  94     return this;
  95   }
  96
  97   CallGraphNode* getExternalCallingNode() const { return ExternalCallingNode; }
  98   CallGraphNode* getCallsExternalNode()   const { return CallsExternalNode; }
  99
 100   // getRoot - Return the root of the call graph, which is either main, or if
 101   // main cannot be found, the external node.
 102   //
 103   CallGraphNode *getRoot()             { return Root; }
 104   const CallGraphNode *getRoot() const { return Root; }
 105
 106 private:
 107   //===---------------------------------------------------------------------
 108   // Implementation of CallGraph construction
 109   //
 110
 111   // addToCallGraph - Add a function to the call graph, and link the node to all
 112   // of the functions that it calls.
 113   //
 114   void addToCallGraph(Function *F) {
 115     CallGraphNode *Node = getOrInsertFunction(F);
 116
 117     // If this function has external linkage, anything could call it.
 118     if (!F->hasLocalLinkage()) {
 119       ExternalCallingNode->addCalledFunction(CallSite(), Node);
 120
 121       // Found the entry point?
 122       if (F->getName() == "main") {
 123         if (Root)    // Found multiple external mains?  Don't pick one.
 124           Root = ExternalCallingNode;
 125         else
 126           Root = Node;          // Found a main, keep track of it!
 127       }
 128     }
 129
 130     // Loop over all of the users of the function, looking for non-call uses.
 131     for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I){
 132       User *U = *I;
 133       if ((!isa<CallInst>(U) && !isa<InvokeInst>(U))
 134           || !CallSite(cast<Instruction>(U)).isCallee(I)) {
 135         // Not a call, or being used as a parameter rather than as the callee.
 136         ExternalCallingNode->addCalledFunction(CallSite(), Node);
 137         break;
 138       }
 139     }
 140
 141     // If this function is not defined in this translation unit, it could call
 142     // anything.
 143     if (F->isDeclaration() && !F->isIntrinsic())
 144       Node->addCalledFunction(CallSite(), CallsExternalNode);
 145
 146     // Look for calls by this function.
 147     for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
 148       for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
 149            II != IE; ++II) {
 150         CallSite CS(cast<Value>(II));
 151         if (CS && !isa<IntrinsicInst>(II)) {
 152           const Function *Callee = CS.getCalledFunction();
 153           if (Callee)
 154             Node->addCalledFunction(CS, getOrInsertFunction(Callee));
 155           else
 156             Node->addCalledFunction(CS, CallsExternalNode);
 157         }
 158       }
 159   }
 160
 161   //
 162   // destroy - Release memory for the call graph
 163   virtual void destroy() {
 164     /// CallsExternalNode is not in the function map, delete it explicitly.
 165     if (CallsExternalNode) {
 166       CallsExternalNode->allReferencesDropped();
 167       delete CallsExternalNode;
 168       CallsExternalNode = 0;
 169     }
 170     CallGraph::destroy();
 171   }
 172 };
 173
 174 } //End anonymous namespace
 175
 176 INITIALIZE_ANALYSIS_GROUP(CallGraph, "Call Graph", BasicCallGraph)
 177 INITIALIZE_AG_PASS(BasicCallGraph, CallGraph, "basiccg",
 178                    "Basic CallGraph Construction", false, true, true)
 179
 180 char CallGraph::ID = 0;
 181 char BasicCallGraph::ID = 0;
 182
 183 void CallGraph::initialize(Module &M) {
 184   Mod = &M;
 185 }
 186
 187 void CallGraph::destroy() {
 188   if (FunctionMap.empty()) return;
 189
 190   // Reset all node's use counts to zero before deleting them to prevent an
 191   // assertion from firing.
 192 #ifndef NDEBUG
 193   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
 194        I != E; ++I)
 195     I->second->allReferencesDropped();
 196 #endif
 197
 198   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
 199       I != E; ++I)
 200     delete I->second;
 201   FunctionMap.clear();
 202 }
 203
 204 void CallGraph::print(raw_ostream &OS, Module*) const {
 205   for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
 206     I->second->print(OS);
 207 }
 208 void CallGraph::dump() const {
 209   print(dbgs(), 0);
 210 }
 211
 212 //===----------------------------------------------------------------------===//
 213 // Implementations of public modification methods
 214 //
 215
 216 // removeFunctionFromModule - Unlink the function from this module, returning
 217 // it.  Because this removes the function from the module, the call graph node
 218 // is destroyed.  This is only valid if the function does not call any other
 219 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
 220 // is to dropAllReferences before calling this.
 221 //
 222 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
 223   assert(CGN->empty() && "Cannot remove function from call "
 224          "graph if it references other functions!");
 225   Function *F = CGN->getFunction(); // Get the function for the call graph node
 226   delete CGN;                       // Delete the call graph node for this func
 227   FunctionMap.erase(F);             // Remove the call graph node from the map
 228
 229   Mod->getFunctionList().remove(F);
 230   return F;
 231 }
 232
 233 /// spliceFunction - Replace the function represented by this node by another.
 234 /// This does not rescan the body of the function, so it is suitable when
 235 /// splicing the body of the old function to the new while also updating all
 236 /// callers from old to new.
 237 ///
 238 void CallGraph::spliceFunction(const Function *From, const Function *To) {
 239   assert(FunctionMap.count(From) && "No CallGraphNode for function!");
 240   assert(!FunctionMap.count(To) &&
 241          "Pointing CallGraphNode at a function that already exists");
 242   FunctionMapTy::iterator I = FunctionMap.find(From);
 243   I->second->F = const_cast<Function*>(To);
 244   FunctionMap[To] = I->second;
 245   FunctionMap.erase(I);
 246 }
 247
 248 // getOrInsertFunction - This method is identical to calling operator[], but
 249 // it will insert a new CallGraphNode for the specified function if one does
 250 // not already exist.
 251 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
 252   CallGraphNode *&CGN = FunctionMap[F];
 253   if (CGN) return CGN;
 254
 255   assert((!F || F->getParent() == Mod) && "Function not in current module!");
 256   return CGN = new CallGraphNode(const_cast<Function*>(F));
 257 }
 258
 259 void CallGraphNode::print(raw_ostream &OS) const {
 260   if (Function *F = getFunction())
 261     OS << "Call graph node for function: '" << F->getName() << "'";
 262   else
 263     OS << "Call graph node <<null function>>";
 264
 265   OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
 266
 267   for (const_iterator I = begin(), E = end(); I != E; ++I) {
 268     OS << "  CS<" << I->first << "> calls ";
 269     if (Function *FI = I->second->getFunction())
 270       OS << "function '" << FI->getName() <<"'\n";
 271     else
 272       OS << "external node\n";
 273   }
 274   OS << '\n';
 275 }
 276
 277 void CallGraphNode::dump() const { print(dbgs()); }
 278
 279 /// removeCallEdgeFor - This method removes the edge in the node for the
 280 /// specified call site.  Note that this method takes linear time, so it
 281 /// should be used sparingly.
 282 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
 283   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 284     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 285     if (I->first == CS.getInstruction()) {
 286       I->second->DropRef();
 287       *I = CalledFunctions.back();
 288       CalledFunctions.pop_back();
 289       return;
 290     }
 291   }
 292 }
 293
 294 // removeAnyCallEdgeTo - This method removes any call edges from this node to
 295 // the specified callee function.  This takes more time to execute than
 296 // removeCallEdgeTo, so it should not be used unless necessary.
 297 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
 298   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
 299     if (CalledFunctions[i].second == Callee) {
 300       Callee->DropRef();
 301       CalledFunctions[i] = CalledFunctions.back();
 302       CalledFunctions.pop_back();
 303       --i; --e;
 304     }
 305 }
 306
 307 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
 308 /// from this node to the specified callee function.
 309 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
 310   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 311     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
 312     CallRecord &CR = *I;
 313     if (CR.second == Callee && CR.first == 0) {
 314       Callee->DropRef();
 315       *I = CalledFunctions.back();
 316       CalledFunctions.pop_back();
 317       return;
 318     }
 319   }
 320 }
 321
 322 /// replaceCallEdge - This method replaces the edge in the node for the
 323 /// specified call site with a new one.  Note that this method takes linear
 324 /// time, so it should be used sparingly.
 325 void CallGraphNode::replaceCallEdge(CallSite CS,
 326                                     CallSite NewCS, CallGraphNode *NewNode){
 327   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 328     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 329     if (I->first == CS.getInstruction()) {
 330       I->second->DropRef();
 331       I->first = NewCS.getInstruction();
 332       I->second = NewNode;
 333       NewNode->AddRef();
 334       return;
 335     }
 336   }
 337 }
 338
 339 // Enuse that users of CallGraph.h also link with this file
 340 DEFINING_FILE_FOR(CallGraph)