resurrected LLVM "C Backend", with improvements

This version of the LLVM-CBE library works with LLVM 8.0. You will have to compile this version of LLVM before you try to use LLVM-CBE. This guide will walk you through the compilation and installation of both tools and show usage statements to verify that the LLVM-CBE library is compiled correctly.

The library is known to compile on various Linux versions (Redhat, Mageia, Ubuntu, Debian), Mac OS X, and Windows (Mingw-w64).

LLVM-CBE relies on specific LLVM internals, and so it is best to use it with a specific revision of the LLVM development tree. Currently, llvm-cbe works with the LLVM 8.0 release version and autotools.

Note: to convert C to LLVM IR to run the tests, you will also need a C compiler such as clang.

The first step is to compile LLVM on your machine (this assumes an in-tree build, but out-of-tree will also work):

 cd $HOME
 git clone https://github.com/llvm/llvm-project.git
 cd llvm-project
 git checkout release/8.x
 mkdir llvm/build
 cd llvm/build
 cmake ..
 make

Next, download and compile llvm-cbe from the same folder:

cd $HOME/llvm-project/llvm/projects
git clone https://github.com/JuliaComputing/llvm-cbe
cd ../build
cmake ..
make llvm-cbe

To run tests, you will also need to build lli:

    make lli

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

$ cd $HOME/llvm-project/llvm/projects/llvm-cbe/test/selectionsort
$ ls
main.c
$ clang -S -emit-llvm -g main.c
$ ls
main.c main.ll
$ $(HOME)/llvm/build/bin/llvm-cbe main.ll

$ gcc -o main.cbe main.cbe.c
$ ls
main.c  main.cbe  main.cbe.c  main.ll
$ ./main.cbe

Unit tests:

    $ cd $HOME/llvm-project/llvm/build
    $ make CBEUnitTests && projects/llvm-cbe/unittests/CWriterTest

Other tests:

First, compile llvm-cbe, and install pytest. Then:

    $ cd $HOME/llvm-project/llvm/projects/llvm-cbe
    $ pytest