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      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/IR/Instructions.h"
     17 #include "llvm/IR/IntrinsicInst.h"
     18 #include "llvm/IR/Module.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     // If this function has its address taken, anything could call it.
    131     if (F->hasAddressTaken())
    132       ExternalCallingNode->addCalledFunction(CallSite(), Node);
    133 
    134     // If this function is not defined in this translation unit, it could call
    135     // anything.
    136     if (F->isDeclaration() && !F->isIntrinsic())
    137       Node->addCalledFunction(CallSite(), CallsExternalNode);
    138 
    139     // Look for calls by this function.
    140     for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
    141       for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
    142            II != IE; ++II) {
    143         CallSite CS(cast<Value>(II));
    144         if (CS) {
    145           const Function *Callee = CS.getCalledFunction();
    146           if (!Callee)
    147             // Indirect calls of intrinsics are not allowed so no need to check.
    148             Node->addCalledFunction(CS, CallsExternalNode);
    149           else if (!Callee->isIntrinsic())
    150             Node->addCalledFunction(CS, getOrInsertFunction(Callee));
    151         }
    152       }
    153   }
    154 
    155   //
    156   // destroy - Release memory for the call graph
    157   virtual void destroy() {
    158     /// CallsExternalNode is not in the function map, delete it explicitly.
    159     if (CallsExternalNode) {
    160       CallsExternalNode->allReferencesDropped();
    161       delete CallsExternalNode;
    162       CallsExternalNode = 0;
    163     }
    164     CallGraph::destroy();
    165   }
    166 };
    167 
    168 } //End anonymous namespace
    169 
    170 INITIALIZE_ANALYSIS_GROUP(CallGraph, "Call Graph", BasicCallGraph)
    171 INITIALIZE_AG_PASS(BasicCallGraph, CallGraph, "basiccg",
    172                    "Basic CallGraph Construction", false, true, true)
    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()) return;
    183 
    184   // Reset all node's use counts to zero before deleting them to prevent an
    185   // assertion from firing.
    186 #ifndef NDEBUG
    187   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
    188        I != E; ++I)
    189     I->second->allReferencesDropped();
    190 #endif
    191 
    192   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
    193       I != E; ++I)
    194     delete I->second;
    195   FunctionMap.clear();
    196 }
    197 
    198 void CallGraph::print(raw_ostream &OS, Module*) const {
    199   for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
    200     I->second->print(OS);
    201 }
    202 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    203 void CallGraph::dump() const {
    204   print(dbgs(), 0);
    205 }
    206 #endif
    207 
    208 //===----------------------------------------------------------------------===//
    209 // Implementations of public modification methods
    210 //
    211 
    212 // removeFunctionFromModule - Unlink the function from this module, returning
    213 // it.  Because this removes the function from the module, the call graph node
    214 // is destroyed.  This is only valid if the function does not call any other
    215 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
    216 // is to dropAllReferences before calling this.
    217 //
    218 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
    219   assert(CGN->empty() && "Cannot remove function from call "
    220          "graph if it references other functions!");
    221   Function *F = CGN->getFunction(); // Get the function for the call graph node
    222   delete CGN;                       // Delete the call graph node for this func
    223   FunctionMap.erase(F);             // Remove the call graph node from the map
    224 
    225   Mod->getFunctionList().remove(F);
    226   return F;
    227 }
    228 
    229 /// spliceFunction - Replace the function represented by this node by another.
    230 /// This does not rescan the body of the function, so it is suitable when
    231 /// splicing the body of the old function to the new while also updating all
    232 /// callers from old to new.
    233 ///
    234 void CallGraph::spliceFunction(const Function *From, const Function *To) {
    235   assert(FunctionMap.count(From) && "No CallGraphNode for function!");
    236   assert(!FunctionMap.count(To) &&
    237          "Pointing CallGraphNode at a function that already exists");
    238   FunctionMapTy::iterator I = FunctionMap.find(From);
    239   I->second->F = const_cast<Function*>(To);
    240   FunctionMap[To] = I->second;
    241   FunctionMap.erase(I);
    242 }
    243 
    244 // getOrInsertFunction - This method is identical to calling operator[], but
    245 // it will insert a new CallGraphNode for the specified function if one does
    246 // not already exist.
    247 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
    248   CallGraphNode *&CGN = FunctionMap[F];
    249   if (CGN) return CGN;
    250 
    251   assert((!F || F->getParent() == Mod) && "Function not in current module!");
    252   return CGN = new CallGraphNode(const_cast<Function*>(F));
    253 }
    254 
    255 void CallGraphNode::print(raw_ostream &OS) const {
    256   if (Function *F = getFunction())
    257     OS << "Call graph node for function: '" << F->getName() << "'";
    258   else
    259     OS << "Call graph node <<null function>>";
    260 
    261   OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
    262 
    263   for (const_iterator I = begin(), E = end(); I != E; ++I) {
    264     OS << "  CS<" << I->first << "> calls ";
    265     if (Function *FI = I->second->getFunction())
    266       OS << "function '" << FI->getName() <<"'\n";
    267     else
    268       OS << "external node\n";
    269   }
    270   OS << '\n';
    271 }
    272 
    273 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    274 void CallGraphNode::dump() const { print(dbgs()); }
    275 #endif
    276 
    277 /// removeCallEdgeFor - This method removes the edge in the node for the
    278 /// specified call site.  Note that this method takes linear time, so it
    279 /// should be used sparingly.
    280 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
    281   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
    282     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
    283     if (I->first == CS.getInstruction()) {
    284       I->second->DropRef();
    285       *I = CalledFunctions.back();
    286       CalledFunctions.pop_back();
    287       return;
    288     }
    289   }
    290 }
    291 
    292 // removeAnyCallEdgeTo - This method removes any call edges from this node to
    293 // the specified callee function.  This takes more time to execute than
    294 // removeCallEdgeTo, so it should not be used unless necessary.
    295 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
    296   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
    297     if (CalledFunctions[i].second == Callee) {
    298       Callee->DropRef();
    299       CalledFunctions[i] = CalledFunctions.back();
    300       CalledFunctions.pop_back();
    301       --i; --e;
    302     }
    303 }
    304 
    305 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
    306 /// from this node to the specified callee function.
    307 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
    308   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
    309     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
    310     CallRecord &CR = *I;
    311     if (CR.second == Callee && CR.first == 0) {
    312       Callee->DropRef();
    313       *I = CalledFunctions.back();
    314       CalledFunctions.pop_back();
    315       return;
    316     }
    317   }
    318 }
    319 
    320 /// replaceCallEdge - This method replaces the edge in the node for the
    321 /// specified call site with a new one.  Note that this method takes linear
    322 /// time, so it should be used sparingly.
    323 void CallGraphNode::replaceCallEdge(CallSite CS,
    324                                     CallSite NewCS, CallGraphNode *NewNode){
    325   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
    326     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
    327     if (I->first == CS.getInstruction()) {
    328       I->second->DropRef();
    329       I->first = NewCS.getInstruction();
    330       I->second = NewNode;
    331       NewNode->AddRef();
    332       return;
    333     }
    334   }
    335 }
    336 
    337 // Enuse that users of CallGraph.h also link with this file
    338 DEFINING_FILE_FOR(CallGraph)
    339