LLEVM

llevm is an erlang wrapper to the C API functions of llvm. The documentation of the functions can be found at the official llvm website. Unfortunately the documentation of the C functions seem to be very sparse, so when looking for what functions do one should try to find the corresponding C++ class function and read the documentation for it instead.

For examples on how to use llevm see the testcases, especially tests/kaleidoscope_SUITE.erl and tests/kaleidoscope_SUITE_data/kal_gen.erl contain lots of basics in how to generate llvm code and use the JIT execution engine from Erlang.

Most functions are converted to erlang and hopefully work as well :) There is a list of which functions are not as yet converted in api_gen/llvm_api.hrl. The functions are listed in the LIMIT macro.

Compiling

You should only have to run

./configure && make

to compile llevm. Make sure that the correct llvm version is in the path.

Some possible issues when compiling are:

• The erlang vm and llvm has to have the same arch (i.e. 64 vs 32 bit)
• You have to have the correct version of llvm. As of this writing that is 2.9. If you need another version you have to regenerate all the erlang and nif files.

Generating a new llevm

If you are not happy with the generated API you can regenerate it to suite your needs. To do this you have to have doxygen in your path then run:

./configure && (cd api_gen && make)

then new src/llevm.erl, csrc/llevm.c and include/llevm.hrl should be regerated. The code which generated the llevm interface is in the api_gen folder and divided into the different files that they generate.

Running test

llevm comes with a set of test which tests that everything works as it should. To run the tests type:

make test

The tests are very basic and are more there to provide examples than to test the actual interface. So just because they pass don't trust that llevm does what it should :)

Debugging

It is possible to enable lots of debug printouts in api_gen/llvm_api_nif.erl. Just search for printf and uncomment those lines and then regenerate llevm. It is also helpful to use gdb to step through execution, there are some example commands in os_lathund to show how I do it on my mac.