Environment Setting

LLVM+Clang Download

• You can build LLVM from source code by yourself on your machine or download the pre-build library from the website directly. [link 1(recommended)] [link 2]
• Be careful of the system of your machine and download the pre-build or source code applicable to your system. [A mistake I made]
• If you need Clang, make sure that the LLVM source code contains Clang src, so does prebuild.

Add LLVM path

After building the LLVM source code or downloading the prebuild, you should add the path of bin dir in build dir you created for the build or the prebuild your loaded. The bin dir contains the libraries you need for writing pass.

In Ubuntu or Mac OS, you can add the LLVM bin path to ~/.bashrc if you like. Attention the appending order of the LLVM path in $PATH

Testing installation

• Query llvm version: llvm-config --version
• Query Clang version: clang --version

BC generation by Clang

• memory mode: hello.bc contains load and store

  clang test hello.c -c -o hello.bc

• Mem2reg mode

  clang -Xclang -disable-O0-optnone -O0 -g -emit-llvm example.c -c -o /dev/stdout | opt -mem2reg -o example.bc

• generate .ll file for mannual reading

  llvm-dis hello.bc

• Remark: Options of clang

Write passes

CMakeList Configuration

The key difficulty of writing the pass is the configuration of CMakeLists.txt. In the CMake Project of LLVM pass, you need to use find_package(LLVM REQUIRED CONFIG) in your CMakeLists.txt so that the LLVM lib(located in the bin directory of LLVM-config