Method runOnModule

lib/DynamicCallCounter.cpp:76–214

----------------------------------------------------------------------------- DynamicCallCounter implementation -----------------------------------------------------------------------------

// DynamicCallCounter implementation
//-----------------------------------------------------------------------------
bool DynamicCallCounter::runOnModule(Module &M) {
  bool Instrumented = false;

  // Function name <--> IR variable that holds the call counter
  llvm::StringMap<Constant *> CallCounterMap;
  // Function name <--> IR variable that holds the function name
  llvm::StringMap<Constant *> FuncNameMap;

  auto &CTX = M.getContext();

  // STEP 1: For each function in the module, inject a call-counting code
  // --------------------------------------------------------------------
  for (auto &F : M) {
    if (F.isDeclaration())
      continue;

    // Get an IR builder. Sets the insertion point to the top of the function
    IRBuilder<> Builder(&*F.getEntryBlock().getFirstInsertionPt());

    // Create a global variable to count the calls to this function
    std::string CounterName = "CounterFor_" + std::string(F.getName());
    Constant *Var = CreateGlobalCounter(M, CounterName);
    CallCounterMap[F.getName()] = Var;

    // Create a global variable to hold the name of this function
    auto FuncName = Builder.CreateGlobalString(F.getName());
    FuncNameMap[F.getName()] = FuncName;

    // Inject instruction to increment the call count each time this function
    // executes
    LoadInst *Load2 = Builder.CreateLoad(IntegerType::getInt32Ty(CTX), Var);
    Value *Inc2 = Builder.CreateAdd(Builder.getInt32(1), Load2);
    Builder.CreateStore(Inc2, Var);

    // The following is visible only if you pass -debug on the command line
    // *and* you have an assert build.
    LLVM_DEBUG(dbgs() << " Instrumented: " << F.getName() << "\n");

    Instrumented = true;
  }

  // Stop here if there are no function definitions in this module
  if (false == Instrumented)
    return Instrumented;

  // STEP 2: Inject the declaration of printf
  // ----------------------------------------
  // Create (or _get_ in cases where it's already available) the following
  // declaration in the IR module:
  //    declare i32 @printf(i8*, ...)
  // It corresponds to the following C declaration:
  //    int printf(char *, ...)
  PointerType *PrintfArgTy = PointerType::getUnqual(Type::getInt8Ty(CTX));
  FunctionType *PrintfTy =
      FunctionType::get(IntegerType::getInt32Ty(CTX), PrintfArgTy,
                        /*IsVarArgs=*/true);

  FunctionCallee Printf = M.getOrInsertFunction("printf", PrintfTy);