Insert a printf into LLVM IR for debug purpose

insertPrint.cpp

static void insertPrint(BasicBlock *BB, StringRef S) {
  Module *M = BB->getModule();
  LLVMContext &Ctx = M->getContext();
  auto *CharPointerTy = PointerType::get(IntegerType::getInt8Ty(Ctx), 0);
  auto *PrintfTy =
      FunctionType::get(IntegerType::getInt32Ty(Ctx), {CharPointerTy}, true);
  auto Printf = M->getOrInsertFunction("printf", PrintfTy);
  auto Arr = ConstantDataArray::getString(Ctx, S);
  GlobalVariable *GV = new GlobalVariable(
      *M, Arr->getType(), true, GlobalValue::PrivateLinkage, Arr, ".str");
  GV->setAlignment(MaybeAlign(1));
  CallInst::Create(Printf, {ConstantExpr::getBitCast(GV, CharPointerTy)}, "",
                   BB);
}