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/Streams.h"
  22 #include <ostream>
  23 using namespace llvm;
  24
  25 namespace {
  26
  27 //===----------------------------------------------------------------------===//
  28 // BasicCallGraph class definition
  29 //
  30 class VISIBILITY_HIDDEN BasicCallGraph : public CallGraph, public ModulePass {
  31   // Root is root of the call graph, or the external node if a 'main' function
  32   // couldn't be found.
  33   //
  34   CallGraphNode *Root;
  35
  36   // ExternalCallingNode - This node has edges to all external functions and
  37   // those internal functions that have their address taken.
  38   CallGraphNode *ExternalCallingNode;
  39
  40   // CallsExternalNode - This node has edges to it from all functions making
  41   // indirect calls or calling an external function.
  42   CallGraphNode *CallsExternalNode;
  43
  44 public:
  45   static char ID; // Class identification, replacement for typeinfo
  46   BasicCallGraph() : ModulePass(&ID), Root(0),
  47     ExternalCallingNode(0), CallsExternalNode(0) {}
  48
  49   // runOnModule - Compute the call graph for the specified module.
  50   virtual bool runOnModule(Module &M) {
  51     CallGraph::initialize(M);
  52
  53     ExternalCallingNode = getOrInsertFunction(0);
  54     CallsExternalNode = new CallGraphNode(0);
  55     Root = 0;
  56
  57     // Add every function to the call graph...
  58     for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  59       addToCallGraph(I);
  60
  61     // If we didn't find a main function, use the external call graph node
  62     if (Root == 0) Root = ExternalCallingNode;
  63
  64     return false;
  65   }
  66
  67   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  68     AU.setPreservesAll();
  69   }
  70
  71   void print(std::ostream *o, const Module *M) const {
  72     if (o) print(*o, M);
  73   }
  74
  75   virtual void print(std::ostream &o, const Module *M) const {
  76     o << "CallGraph Root is: ";
  77     if (Function *F = getRoot()->getFunction())
  78       o << F->getNameStr() << "\n";
  79     else
  80       o << "<<null function: 0x" << getRoot() << ">>\n";
  81
  82     CallGraph::print(o, M);
  83   }
  84
  85   virtual void releaseMemory() {
  86     destroy();
  87   }
  88
  89   /// dump - Print out this call graph.
  90   ///
  91   inline void dump() const {
  92     print(cerr, Mod);
  93   }
  94
  95   CallGraphNode* getExternalCallingNode() const { return ExternalCallingNode; }
  96   CallGraphNode* getCallsExternalNode()   const { return CallsExternalNode; }
  97
  98   // getRoot - Return the root of the call graph, which is either main, or if
  99   // main cannot be found, the external node.
 100   //
 101   CallGraphNode *getRoot()             { return Root; }
 102   const CallGraphNode *getRoot() const { return Root; }
 103
 104 private:
 105   //===---------------------------------------------------------------------
 106   // Implementation of CallGraph construction
 107   //
 108
 109   // addToCallGraph - Add a function to the call graph, and link the node to all
 110   // of the functions that it calls.
 111   //
 112   void addToCallGraph(Function *F) {
 113     CallGraphNode *Node = getOrInsertFunction(F);
 114
 115     // If this function has external linkage, anything could call it.
 116     if (!F->hasLocalLinkage()) {
 117       ExternalCallingNode->addCalledFunction(CallSite(), Node);
 118
 119       // Found the entry point?
 120       if (F->getName() == "main") {
 121         if (Root)    // Found multiple external mains?  Don't pick one.
 122           Root = ExternalCallingNode;
 123         else
 124           Root = Node;          // Found a main, keep track of it!
 125       }
 126     }
 127
 128     // Loop over all of the users of the function, looking for non-call uses.
 129     for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I)
 130       if ((!isa<CallInst>(I) && !isa<InvokeInst>(I))
 131           || !CallSite(cast<Instruction>(I)).isCallee(I)) {
 132         // Not a call, or being used as a parameter rather than as the callee.
 133         ExternalCallingNode->addCalledFunction(CallSite(), Node);
 134         break;
 135       }
 136
 137     // If this function is not defined in this translation unit, it could call
 138     // anything.
 139     if (F->isDeclaration() && !F->isIntrinsic())
 140       Node->addCalledFunction(CallSite(), CallsExternalNode);
 141
 142     // Look for calls by this function.
 143     for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
 144       for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
 145            II != IE; ++II) {
 146         CallSite CS = CallSite::get(II);
 147         if (CS.getInstruction() && !isa<DbgInfoIntrinsic>(II)) {
 148           const Function *Callee = CS.getCalledFunction();
 149           if (Callee)
 150             Node->addCalledFunction(CS, getOrInsertFunction(Callee));
 151           else
 152             Node->addCalledFunction(CS, CallsExternalNode);
 153         }
 154       }
 155   }
 156
 157   //
 158   // destroy - Release memory for the call graph
 159   virtual void destroy() {
 160     /// CallsExternalNode is not in the function map, delete it explicitly.
 161     delete CallsExternalNode;
 162     CallsExternalNode = 0;
 163     CallGraph::destroy();
 164   }
 165 };
 166
 167 } //End anonymous namespace
 168
 169 static RegisterAnalysisGroup<CallGraph> X("Call Graph");
 170 static RegisterPass<BasicCallGraph>
 171 Y("basiccg", "Basic CallGraph Construction", false, true);
 172 static RegisterAnalysisGroup<CallGraph, true> Z(Y);
 173
 174 char CallGraph::ID = 0;
 175 char BasicCallGraph::ID = 0;
 176
 177 void CallGraph::initialize(Module &M) {
 178   Mod = &M;
 179 }
 180
 181 void CallGraph::destroy() {
 182   if (!FunctionMap.empty()) {
 183     for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
 184         I != E; ++I)
 185       delete I->second;
 186     FunctionMap.clear();
 187   }
 188 }
 189
 190 void CallGraph::print(std::ostream &OS, const Module *M) const {
 191   for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
 192     I->second->print(OS);
 193 }
 194
 195 void CallGraph::dump() const {
 196   print(cerr, 0);
 197 }
 198
 199 //===----------------------------------------------------------------------===//
 200 // Implementations of public modification methods
 201 //
 202
 203 // removeFunctionFromModule - Unlink the function from this module, returning
 204 // it.  Because this removes the function from the module, the call graph node
 205 // is destroyed.  This is only valid if the function does not call any other
 206 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
 207 // is to dropAllReferences before calling this.
 208 //
 209 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
 210   assert(CGN->CalledFunctions.empty() && "Cannot remove function from call "
 211          "graph if it references other functions!");
 212   Function *F = CGN->getFunction(); // Get the function for the call graph node
 213   delete CGN;                       // Delete the call graph node for this func
 214   FunctionMap.erase(F);             // Remove the call graph node from the map
 215
 216   Mod->getFunctionList().remove(F);
 217   return F;
 218 }
 219
 220 // changeFunction - This method changes the function associated with this
 221 // CallGraphNode, for use by transformations that need to change the prototype
 222 // of a Function (thus they must create a new Function and move the old code
 223 // over).
 224 void CallGraph::changeFunction(Function *OldF, Function *NewF) {
 225   iterator I = FunctionMap.find(OldF);
 226   CallGraphNode *&New = FunctionMap[NewF];
 227   assert(I != FunctionMap.end() && I->second && !New &&
 228          "OldF didn't exist in CG or NewF already does!");
 229   New = I->second;
 230   New->F = NewF;
 231   FunctionMap.erase(I);
 232 }
 233
 234 // getOrInsertFunction - This method is identical to calling operator[], but
 235 // it will insert a new CallGraphNode for the specified function if one does
 236 // not already exist.
 237 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
 238   CallGraphNode *&CGN = FunctionMap[F];
 239   if (CGN) return CGN;
 240
 241   assert((!F || F->getParent() == Mod) && "Function not in current module!");
 242   return CGN = new CallGraphNode(const_cast<Function*>(F));
 243 }
 244
 245 void CallGraphNode::print(std::ostream &OS) const {
 246   if (Function *F = getFunction())
 247     OS << "Call graph node for function: '" << F->getNameStr() <<"'\n";
 248   else
 249     OS << "Call graph node <<null function: 0x" << this << ">>:\n";
 250
 251   for (const_iterator I = begin(), E = end(); I != E; ++I)
 252     if (Function *FI = I->second->getFunction())
 253       OS << "  Calls function '" << FI->getNameStr() <<"'\n";
 254   else
 255     OS << "  Calls external node\n";
 256   OS << "\n";
 257 }
 258
 259 void CallGraphNode::dump() const { print(cerr); }
 260
 261 /// removeCallEdgeFor - This method removes the edge in the node for the
 262 /// specified call site.  Note that this method takes linear time, so it
 263 /// should be used sparingly.
 264 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
 265   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 266     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 267     if (I->first == CS) {
 268       CalledFunctions.erase(I);
 269       return;
 270     }
 271   }
 272 }
 273
 274
 275 // removeAnyCallEdgeTo - This method removes any call edges from this node to
 276 // the specified callee function.  This takes more time to execute than
 277 // removeCallEdgeTo, so it should not be used unless necessary.
 278 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
 279   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
 280     if (CalledFunctions[i].second == Callee) {
 281       CalledFunctions[i] = CalledFunctions.back();
 282       CalledFunctions.pop_back();
 283       --i; --e;
 284     }
 285 }
 286
 287 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
 288 /// from this node to the specified callee function.
 289 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
 290   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 291     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
 292     CallRecord &CR = *I;
 293     if (CR.second == Callee && !CR.first.getInstruction()) {
 294       CalledFunctions.erase(I);
 295       return;
 296     }
 297   }
 298 }
 299
 300 /// replaceCallSite - Make the edge in the node for Old CallSite be for
 301 /// New CallSite instead.  Note that this method takes linear time, so it
 302 /// should be used sparingly.
 303 void CallGraphNode::replaceCallSite(CallSite Old, CallSite New) {
 304   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 305     assert(I != CalledFunctions.end() && "Cannot find callsite to replace!");
 306     if (I->first == Old) {
 307       I->first = New;
 308       return;
 309     }
 310   }
 311 }
 312
 313 // Enuse that users of CallGraph.h also link with this file
 314 DEFINING_FILE_FOR(CallGraph)