lib/Analysis/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/ADT/STLExtras.h"
  12 #include "llvm/ADT/SmallVector.h"
  13 #include "llvm/Config/llvm-config.h"
  14 #include "llvm/IR/CallSite.h"
  15 #include "llvm/IR/Module.h"
  16 #include "llvm/IR/Function.h"
  17 #include "llvm/IR/Intrinsics.h"
  18 #include "llvm/IR/PassManager.h"
  19 #include "llvm/Pass.h"
  20 #include "llvm/Support/Compiler.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/raw_ostream.h"
  23 #include <algorithm>
  24 #include <cassert>
  25
  26 using namespace llvm;
  27
  28 //===----------------------------------------------------------------------===//
  29 // Implementations of the CallGraph class methods.
  30 //
  31
  32 CallGraph::CallGraph(Module &M)
  33     : M(M), ExternalCallingNode(getOrInsertFunction(nullptr)),
  34       CallsExternalNode(llvm::make_unique<CallGraphNode>(nullptr)) {
  35   // Add every function to the call graph.
  36   for (Function &F : M)
  37     addToCallGraph(&F);
  38 }
  39
  40 CallGraph::CallGraph(CallGraph &&Arg)
  41     : M(Arg.M), FunctionMap(std::move(Arg.FunctionMap)),
  42       ExternalCallingNode(Arg.ExternalCallingNode),
  43       CallsExternalNode(std::move(Arg.CallsExternalNode)) {
  44   Arg.FunctionMap.clear();
  45   Arg.ExternalCallingNode = nullptr;
  46 }
  47
  48 CallGraph::~CallGraph() {
  49   // CallsExternalNode is not in the function map, delete it explicitly.
  50   if (CallsExternalNode)
  51     CallsExternalNode->allReferencesDropped();
  52
  53 // Reset all node's use counts to zero before deleting them to prevent an
  54 // assertion from firing.
  55 #ifndef NDEBUG
  56   for (auto &I : FunctionMap)
  57     I.second->allReferencesDropped();
  58 #endif
  59 }
  60
  61 void CallGraph::addToCallGraph(Function *F) {
  62   CallGraphNode *Node = getOrInsertFunction(F);
  63
  64   // If this function has external linkage or has its address taken, anything
  65   // could call it.
  66   if (!F->hasLocalLinkage() || F->hasAddressTaken())
  67     ExternalCallingNode->addCalledFunction(CallSite(), Node);
  68
  69   // If this function is not defined in this translation unit, it could call
  70   // anything.
  71   if (F->isDeclaration() && !F->isIntrinsic())
  72     Node->addCalledFunction(CallSite(), CallsExternalNode.get());
  73
  74   // Look for calls by this function.
  75   for (BasicBlock &BB : *F)
  76     for (Instruction &I : BB) {
  77       if (auto CS = CallSite(&I)) {
  78         const Function *Callee = CS.getCalledFunction();
  79         if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
  80           // Indirect calls of intrinsics are not allowed so no need to check.
  81           // We can be more precise here by using TargetArg returned by
  82           // Intrinsic::isLeaf.
  83           Node->addCalledFunction(CS, CallsExternalNode.get());
  84         else if (!Callee->isIntrinsic())
  85           Node->addCalledFunction(CS, getOrInsertFunction(Callee));
  86       }
  87     }
  88 }
  89
  90 void CallGraph::print(raw_ostream &OS) const {
  91   // Print in a deterministic order by sorting CallGraphNodes by name.  We do
  92   // this here to avoid slowing down the non-printing fast path.
  93
  94   SmallVector<CallGraphNode *, 16> Nodes;
  95   Nodes.reserve(FunctionMap.size());
  96
  97   for (const auto &I : *this)
  98     Nodes.push_back(I.second.get());
  99
 100   llvm::sort(Nodes, [](CallGraphNode *LHS, CallGraphNode *RHS) {
 101     if (Function *LF = LHS->getFunction())
 102       if (Function *RF = RHS->getFunction())
 103         return LF->getName() < RF->getName();
 104
 105     return RHS->getFunction() != nullptr;
 106   });
 107
 108   for (CallGraphNode *CN : Nodes)
 109     CN->print(OS);
 110 }
 111
 112 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 113 LLVM_DUMP_METHOD void CallGraph::dump() const { print(dbgs()); }
 114 #endif
 115
 116 // removeFunctionFromModule - Unlink the function from this module, returning
 117 // it.  Because this removes the function from the module, the call graph node
 118 // is destroyed.  This is only valid if the function does not call any other
 119 // functions (ie, there are no edges in it's CGN).  The easiest way to do this
 120 // is to dropAllReferences before calling this.
 121 //
 122 Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
 123   assert(CGN->empty() && "Cannot remove function from call "
 124          "graph if it references other functions!");
 125   Function *F = CGN->getFunction(); // Get the function for the call graph node
 126   FunctionMap.erase(F);             // Remove the call graph node from the map
 127
 128   M.getFunctionList().remove(F);
 129   return F;
 130 }
 131
 132 /// spliceFunction - Replace the function represented by this node by another.
 133 /// This does not rescan the body of the function, so it is suitable when
 134 /// splicing the body of the old function to the new while also updating all
 135 /// callers from old to new.
 136 void CallGraph::spliceFunction(const Function *From, const Function *To) {
 137   assert(FunctionMap.count(From) && "No CallGraphNode for function!");
 138   assert(!FunctionMap.count(To) &&
 139          "Pointing CallGraphNode at a function that already exists");
 140   FunctionMapTy::iterator I = FunctionMap.find(From);
 141   I->second->F = const_cast<Function*>(To);
 142   FunctionMap[To] = std::move(I->second);
 143   FunctionMap.erase(I);
 144 }
 145
 146 // getOrInsertFunction - This method is identical to calling operator[], but
 147 // it will insert a new CallGraphNode for the specified function if one does
 148 // not already exist.
 149 CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
 150   auto &CGN = FunctionMap[F];
 151   if (CGN)
 152     return CGN.get();
 153
 154   assert((!F || F->getParent() == &M) && "Function not in current module!");
 155   CGN = llvm::make_unique<CallGraphNode>(const_cast<Function *>(F));
 156   return CGN.get();
 157 }
 158
 159 //===----------------------------------------------------------------------===//
 160 // Implementations of the CallGraphNode class methods.
 161 //
 162
 163 void CallGraphNode::print(raw_ostream &OS) const {
 164   if (Function *F = getFunction())
 165     OS << "Call graph node for function: '" << F->getName() << "'";
 166   else
 167     OS << "Call graph node <<null function>>";
 168
 169   OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
 170
 171   for (const auto &I : *this) {
 172     OS << "  CS<" << I.first << "> calls ";
 173     if (Function *FI = I.second->getFunction())
 174       OS << "function '" << FI->getName() <<"'\n";
 175     else
 176       OS << "external node\n";
 177   }
 178   OS << '\n';
 179 }
 180
 181 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 182 LLVM_DUMP_METHOD void CallGraphNode::dump() const { print(dbgs()); }
 183 #endif
 184
 185 /// removeCallEdgeFor - This method removes the edge in the node for the
 186 /// specified call site.  Note that this method takes linear time, so it
 187 /// should be used sparingly.
 188 void CallGraphNode::removeCallEdgeFor(CallSite CS) {
 189   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 190     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 191     if (I->first == CS.getInstruction()) {
 192       I->second->DropRef();
 193       *I = CalledFunctions.back();
 194       CalledFunctions.pop_back();
 195       return;
 196     }
 197   }
 198 }
 199
 200 // removeAnyCallEdgeTo - This method removes any call edges from this node to
 201 // the specified callee function.  This takes more time to execute than
 202 // removeCallEdgeTo, so it should not be used unless necessary.
 203 void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
 204   for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
 205     if (CalledFunctions[i].second == Callee) {
 206       Callee->DropRef();
 207       CalledFunctions[i] = CalledFunctions.back();
 208       CalledFunctions.pop_back();
 209       --i; --e;
 210     }
 211 }
 212
 213 /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
 214 /// from this node to the specified callee function.
 215 void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
 216   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 217     assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
 218     CallRecord &CR = *I;
 219     if (CR.second == Callee && CR.first == nullptr) {
 220       Callee->DropRef();
 221       *I = CalledFunctions.back();
 222       CalledFunctions.pop_back();
 223       return;
 224     }
 225   }
 226 }
 227
 228 /// replaceCallEdge - This method replaces the edge in the node for the
 229 /// specified call site with a new one.  Note that this method takes linear
 230 /// time, so it should be used sparingly.
 231 void CallGraphNode::replaceCallEdge(CallSite CS,
 232                                     CallSite NewCS, CallGraphNode *NewNode){
 233   for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
 234     assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
 235     if (I->first == CS.getInstruction()) {
 236       I->second->DropRef();
 237       I->first = NewCS.getInstruction();
 238       I->second = NewNode;
 239       NewNode->AddRef();
 240       return;
 241     }
 242   }
 243 }
 244
 245 // Provide an explicit template instantiation for the static ID.
 246 AnalysisKey CallGraphAnalysis::Key;
 247
 248 PreservedAnalyses CallGraphPrinterPass::run(Module &M,
 249                                             ModuleAnalysisManager &AM) {
 250   AM.getResult<CallGraphAnalysis>(M).print(OS);
 251   return PreservedAnalyses::all();
 252 }
 253
 254 //===----------------------------------------------------------------------===//
 255 // Out-of-line definitions of CallGraphAnalysis class members.
 256 //
 257
 258 //===----------------------------------------------------------------------===//
 259 // Implementations of the CallGraphWrapperPass class methods.
 260 //
 261
 262 CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
 263   initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
 264 }
 265
 266 CallGraphWrapperPass::~CallGraphWrapperPass() = default;
 267
 268 void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
 269   AU.setPreservesAll();
 270 }
 271
 272 bool CallGraphWrapperPass::runOnModule(Module &M) {
 273   // All the real work is done in the constructor for the CallGraph.
 274   G.reset(new CallGraph(M));
 275   return false;
 276 }
 277
 278 INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
 279                 false, true)
 280
 281 char CallGraphWrapperPass::ID = 0;
 282
 283 void CallGraphWrapperPass::releaseMemory() { G.reset(); }
 284
 285 void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
 286   if (!G) {
 287     OS << "No call graph has been built!\n";
 288     return;
 289   }
 290
 291   // Just delegate.
 292   G->print(OS);
 293 }
 294
 295 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 296 LLVM_DUMP_METHOD
 297 void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
 298 #endif
 299
 300 namespace {
 301
 302 struct CallGraphPrinterLegacyPass : public ModulePass {
 303   static char ID; // Pass ID, replacement for typeid
 304
 305   CallGraphPrinterLegacyPass() : ModulePass(ID) {
 306     initializeCallGraphPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
 307   }
 308
 309   void getAnalysisUsage(AnalysisUsage &AU) const override {
 310     AU.setPreservesAll();
 311     AU.addRequiredTransitive<CallGraphWrapperPass>();
 312   }
 313
 314   bool runOnModule(Module &M) override {
 315     getAnalysis<CallGraphWrapperPass>().print(errs(), &M);
 316     return false;
 317   }
 318 };
 319
 320 } // end anonymous namespace
 321
 322 char CallGraphPrinterLegacyPass::ID = 0;
 323
 324 INITIALIZE_PASS_BEGIN(CallGraphPrinterLegacyPass, "print-callgraph",
 325                       "Print a call graph", true, true)
 326 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
 327 INITIALIZE_PASS_END(CallGraphPrinterLegacyPass, "print-callgraph",
 328                     "Print a call graph", true, true)