src/llvm/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 #include "llvm/Analysis/CallGraph.h"
  11 #include "llvm/IR/CallSite.h"
  12 #include "llvm/IR/Instructions.h"
  13 #include "llvm/IR/IntrinsicInst.h"
  14 #include "llvm/IR/Module.h"
  15 #include "llvm/Support/Debug.h"
  16 #include "llvm/Support/raw_ostream.h"
  17 using namespace llvm;
  18
  19 //===----------------------------------------------------------------------===//
  20 // Implementations of the CallGraph class methods.
  21 //
  22
  23 CallGraph::CallGraph(Module &M)
  24     : M(M), Root(nullptr), ExternalCallingNode(getOrInsertFunction(nullptr)),
  25       CallsExternalNode(new CallGraphNode(nullptr)) {
  26   // Add every function to the call graph.
  27   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  28     addToCallGraph(I);
  29
  30   // If we didn't find a main function, use the external call graph node
  31   if (!Root)
  32     Root = ExternalCallingNode;
  33 }
  34
  35 CallGraph::~CallGraph() {
  36   // CallsExternalNode is not in the function map, delete it explicitly.
  37   CallsExternalNode->allReferencesDropped();
  38   delete CallsExternalNode;
  39
  40 // Reset all node's use counts to zero before deleting them to prevent an
  41 // assertion from firing.
  42 #ifndef NDEBUG
  43   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
  44        I != E; ++I)
  45     I->second->allReferencesDropped();
  46 #endif
  47   for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
  48        I != E; ++I)
  49     delete I->second;
  50 }
  51
  52 void CallGraph::addToCallGraph(Function *F) {
  53   CallGraphNode *Node = getOrInsertFunction(F);
  54
  55   // If this function has external linkage, anything could call it.
  56   if (!F->hasLocalLinkage()) {
  57     ExternalCallingNode->addCalledFunction(CallSite(), Node);
  58
  59     // Found the entry point?
  60     if (F->getName() == "main") {
  61       if (Root) // Found multiple external mains?  Don't pick one.
  62         Root = ExternalCallingNode;
  63       else
  64         Root = Node; // Found a main, keep track of it!
  65     }
  66   }
  67
  68   // If this function has its address taken, anything could call it.
  69   if (F->hasAddressTaken())
  70     ExternalCallingNode->addCalledFunction(CallSite(), Node);
  71
  72   // If this function is not defined in this translation unit, it could call
  73   // anything.
  74   if (F->isDeclaration() && !F->isIntrinsic())
  75     Node->addCalledFunction(CallSite(), CallsExternalNode);
  76
  77   // Look for calls by this function.
  78   for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
  79     for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;
  80          ++II) {
  81       CallSite CS(cast<Value>(II));
  82       if (CS) {
  83         const Function *Callee = CS.getCalledFunction();
  84         if (!Callee)
  85           // Indirect calls of intrinsics are not allowed so no need to check.
  86           Node->addCalledFunction(CS, CallsExternalNode);
  87         else if (!Callee->isIntrinsic())
  88           Node->addCalledFunction(CS, getOrInsertFunction(Callee));
  89       }
  90     }
  91 }
  92
  93 void CallGraph::print(raw_ostream &OS) const {
  94   OS << "CallGraph Root is: ";
  95   if (Function *F = Root->getFunction())
  96     OS << F->getName() << "\n";
  97   else {
  98     OS << "<<null function: 0x" << Root << ">>\n";
  99   }
 100
 101   for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
 102     I->second->print(OS);
 103 }
 104
 105 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 106 void CallGraph::dump() const { print(dbgs()); }
 107 #endif
 108
 109 // removeFunctionFromModule - Unlink the function from this module, returning
 110 // it.  Because this removes the function from the module, the call graph node
 111 // is destroyed.  This is only valid if the function does not call any other
 112 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
 113 // is to dropAllReferences before calling this.
 114 //
 115 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
 116   assert(CGN->empty() && "Cannot remove function from call "
 117          "graph if it references other functions!");
 118   Function *F = CGN->getFunction(); // Get the function for the call graph node
 119   delete CGN;                       // Delete the call graph node for this func
 120   FunctionMap.erase(F);             // Remove the call graph node from the map
 121
 122   M.getFunctionList().remove(F);
 123   return F;
 124 }
 125
 126 /// spliceFunction - Replace the function represented by this node by another.
 127 /// This does not rescan the body of the function, so it is suitable when
 128 /// splicing the body of the old function to the new while also updating all
 129 /// callers from old to new.
 130 ///
 131 void CallGraph::spliceFunction(const Function *From, const Function *To) {
 132   assert(FunctionMap.count(From) && "No CallGraphNode for function!");
 133   assert(!FunctionMap.count(To) &&
 134          "Pointing CallGraphNode at a function that already exists");
 135   FunctionMapTy::iterator I = FunctionMap.find(From);
 136   I->second->F = const_cast<Function*>(To);
 137   FunctionMap[To] = I->second;
 138   FunctionMap.erase(I);
 139 }
 140
 141 // getOrInsertFunction - This method is identical to calling operator[], but
 142 // it will insert a new CallGraphNode for the specified function if one does
 143 // not already exist.
 144 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
 145   CallGraphNode *&CGN = FunctionMap[F];
 146   if (CGN)
 147     return CGN;
 148
 149   assert((!F || F->getParent() == &M) && "Function not in current module!");
 150   return CGN = new CallGraphNode(const_cast<Function*>(F));
 151 }
 152
 153 //===----------------------------------------------------------------------===//
 154 // Implementations of the CallGraphNode class methods.
 155 //
 156
 157 void CallGraphNode::print(raw_ostream &OS) const {
 158   if (Function *F = getFunction())
 159     OS << "Call graph node for function: '" << F->getName() << "'";
 160   else
 161     OS << "Call graph node <<null function>>";
 162
 163   OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
 164
 165   for (const_iterator I = begin(), E = end(); I != E; ++I) {
 166     OS << "  CS<" << I->first << "> calls ";
 167     if (Function *FI = I->second->getFunction())
 168       OS << "function '" << FI->getName() <<"'\n";
 169     else
 170       OS << "external node\n";
 171   }
 172   OS << '\n';
 173 }
 174
 175 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 176 void CallGraphNode::dump() const { print(dbgs()); }
 177 #endif
 178
 179 /// removeCallEdgeFor - This method removes the edge in the node for the
 180 /// specified call site.  Note that this method takes linear time, so it
 181 /// should be used sparingly.
 182 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
 183   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 184     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 185     if (I->first == CS.getInstruction()) {
 186       I->second->DropRef();
 187       *I = CalledFunctions.back();
 188       CalledFunctions.pop_back();
 189       return;
 190     }
 191   }
 192 }
 193
 194 // removeAnyCallEdgeTo - This method removes any call edges from this node to
 195 // the specified callee function.  This takes more time to execute than
 196 // removeCallEdgeTo, so it should not be used unless necessary.
 197 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
 198   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
 199     if (CalledFunctions[i].second == Callee) {
 200       Callee->DropRef();
 201       CalledFunctions[i] = CalledFunctions.back();
 202       CalledFunctions.pop_back();
 203       --i; --e;
 204     }
 205 }
 206
 207 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
 208 /// from this node to the specified callee function.
 209 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
 210   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 211     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
 212     CallRecord &CR = *I;
 213     if (CR.second == Callee && CR.first == nullptr) {
 214       Callee->DropRef();
 215       *I = CalledFunctions.back();
 216       CalledFunctions.pop_back();
 217       return;
 218     }
 219   }
 220 }
 221
 222 /// replaceCallEdge - This method replaces the edge in the node for the
 223 /// specified call site with a new one.  Note that this method takes linear
 224 /// time, so it should be used sparingly.
 225 void CallGraphNode::replaceCallEdge(CallSite CS,
 226                                     CallSite NewCS, CallGraphNode *NewNode){
 227   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 228     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 229     if (I->first == CS.getInstruction()) {
 230       I->second->DropRef();
 231       I->first = NewCS.getInstruction();
 232       I->second = NewNode;
 233       NewNode->AddRef();
 234       return;
 235     }
 236   }
 237 }
 238
 239 //===----------------------------------------------------------------------===//
 240 // Out-of-line definitions of CallGraphAnalysis class members.
 241 //
 242
 243 char CallGraphAnalysis::PassID;
 244
 245 //===----------------------------------------------------------------------===//
 246 // Implementations of the CallGraphWrapperPass class methods.
 247 //
 248
 249 CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
 250   initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
 251 }
 252
 253 CallGraphWrapperPass::~CallGraphWrapperPass() {}
 254
 255 void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 256   AU.setPreservesAll();
 257 }
 258
 259 bool CallGraphWrapperPass::runOnModule(Module &M) {
 260   // All the real work is done in the constructor for the CallGraph.
 261   G.reset(new CallGraph(M));
 262   return false;
 263 }
 264
 265 INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
 266                 false, true)
 267
 268 char CallGraphWrapperPass::ID = 0;
 269
 270 void CallGraphWrapperPass::releaseMemory() { G.reset(); }
 271
 272 void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
 273   if (!G) {
 274     OS << "No call graph has been built!\n";
 275     return;
 276   }
 277
 278   // Just delegate.
 279   G->print(OS);
 280 }
 281
 282 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 283 void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
 284 #endif