A Haskell version of the llvm-tutor project using llvm-hs, the Haskell LLVM bindings.

Working directly with LLVM in C++ is tedious, unsafe, and highly error-prone. It is possible to write code that behaves like an out-of-source LLVM pass directly in Haskell.

The goal of this project is to showcase that LLVM can in fact be easy and fun to work with. This is demonstrated through a collection of self-contained testable passes which are implemented using idiomatic Haskell.

The HelloWorld pass in app/HelloWorld.hs demonstrates the basics of working with LLVM from Haskell.

If you are using your system-wide installed version of LLVM, you should not need to do any special setup. You can build the example passes by saying

stack build

If you have built LLVM from source, then you will need to tell stack where to look for the LLVM tools (such as the llvm-config utility), and shared libraries. The simplest way to do this is to prefix your stack commands like so:

LD_LIBRARY_PATH=$(realpath ../llvm-12.0.0-root/lib) PATH=$(realpath ../llvm-12.0.0-root/bin):$PATH stack build

Before you can test the HelloWorld pass, you need to prepare an input file:

clang -S -emit-llvm inputs/input_for_hello.c -o input_for_hello.ll

Run HelloWorld with stack like so:

stack exec -- helloworld input_for_hello.ll
Hello from: Name "foo"
  number of arguments: 1
Hello from: Name "bar"
  number of arguments: 2
Hello from: Name "fez"
  number of arguments: 3
Hello from: Name "main"
  number of arguments: 2