llvm-cxxapi

Resurrected LLVM "Cpp Backend", rebuild as a LLVM tool, re implemented IR generation using IRBuilder, re implemented generation Type using TypeBuilder.

INSTALLATION INSTRUCTIONS

The llvm-cxxapi tool works with LLVM 3.8 ~ 7.0. You will have to compile these version of LLVM before you try to use llvm-cxxapi. This guide will walk you through the compilation and installation of both tools and show usage statements to verify that the llvm-cxxapi tool is compiled correctly.

It is known to compile on various Linux versions (Redhat, Ubuntu, etc), Mac OS X, and Windows (MSVC, Mingw-w64).

Step 1: Clone LLVM and llvm-cxxapi

The llvm-cxxapi relies on specific LLVM librarys, and so it is best to use it with a specific revision of the LLVM development tree. Currently, llvm-cxxapi works with the LLVM 3.8 ~ 7.0 release versions.

If you have never work with LLVM, the first step is to download LLVM on your machine.

cd $HOME
git clone https://github.com/llvm-mirror/llvm
cd llvm
git checkout release_60

Download llvm-cxxapi

cd $HOME/llvm/projects
git clone git@github.com:zhangjiantao/llvm-cxxapi.git

Step 2: Building

Now you can build the LLVM project, and the build target already contains llvm-cxxapi

cd $HOME/llvm/
mkdir build && cd build
cmake -G Ninja ..
ninja all

Step 3: Usage Examples

If llvm-cxxapi compiles, you should be able to run it with the following commands.

$ cd $ANYWHERE

$ echo "int test(int a) { return (((a ^ 4) * 3) ^ 2) + 1;}" > test.c

$ $HOME/llvm/bin/clang -emit-llvm -S -O3 test.c

$ $HOME/llvm/bin/llvm-cxxapi test.ll -o test.ll.cpp

Or use pipe

$ alias clang=$HOME/llvm/bin/clang

$ alias cxxapi=$HOME/llvm/bin/llvm-cxxapi

$ echo "int test(int a) { return (((a ^ 4) * 3) ^ 2) + 1;}" | clang -x c - -emit-llvm -S -O3 -o - | cxxapi -o test.ll.cpp

Now you get a C++ program to generate the IR of function "test", such as

IRBuilder<> IRB(Ctx);

auto FuncTy = TypeBuilder<int32_t(int32_t), false>::get(Ctx);
auto FuncTest = Function::Create(FuncTy, GlobalValue::ExternalLinkage, "test", M);

// Function: test
if (1) {
  SmallVector<Argument *, 1> Args;
  for (auto &Arg : FuncTest->args())
    Args.push_back(&Arg);
    
  // BasicBlocks
  auto Block = BasicBlock::Create(Ctx, "", FuncTest);
  
  // BasicBlock  (Block)
  IRB.SetInsertPoint(Block);
  auto XorInt32t = IRB.CreateXor(Args[0], IRB.getInt32(4));
  auto MulInt32t = IRB.CreateMul(XorInt32t, IRB.getInt32(3), "", false, true);
  auto XorInt32t1 = IRB.CreateXor(MulInt32t, IRB.getInt32(2));
  auto AddInt32t = IRB.CreateAdd(XorInt32t1, IRB.getInt32(1), "", false, true);
  IRB.CreateRet(AddInt32t);
}

Compile Generated C++ Code and Run

$ clang++ `llvm-config --cxxflags` -o test.ll.o -c test.ll.cpp

$ clang++ `llvm-config --ldflags` -o testcxx test.ll.o `llvm-config --system-libs --libs core support`

$ ./testcxx