llvmlite 0.5.0

lightweight wrapper around basic LLVM functionality

A lightweight LLVM python binding for writing JIT compilers

The old llvmpy binding exposes a lot of LLVM APIs but the mapping of C++-style memory management to Python is error prone. Numba and many JIT compilers do not need a full LLVM API. Only the IR builder, optimizer, and JIT compiler APIs are necessary.

llvmlite is a project originally tailored for Numba’s needs, using the following approach:

• A small C wrapper around the parts of the LLVM C++ API we need that are not already exposed by the LLVM C API.

• A ctypes Python wrapper around the C API.

• A pure Python implementation of the subset of the LLVM IR builder that we need for Numba.

Key Benefits

• The IR builder is pure Python code and decoupled from LLVM’s frequently-changing C++ APIs.

• Materializing a LLVM module calls LLVM’s IR parser which provides better error messages than step-by-step IR building through the C++ API (no more segfaults or process aborts).

• Most of llvmlite uses the LLVM C API which is small but very stable (low maintenance when changing LLVM version).

• The binding is not a Python C-extension, but a plain DLL accessed using ctypes (no need to wrestle with Python’s compiler requirements and C++ 11 compatibility).

• The Python binding layer has sane memory management.

• llvmlite is quite faster than llvmpy’s thanks to a much simpler architeture (the Numba test suite is twice faster than it was).

llvmpy Compatibility Layer

The llvmlite.llvmpy namespace provides a minimal llvmpy compatibility layer.

Documentation

You’ll find the documentation at http://llvmlite.pydata.org

Dependencies

You need Python 2.6 or greater (including Python 3.3 or greater).

Build dependencies

• LLVM 3.5

• A C++ 11 compiler, and possibly other tools (see below)

Runtime dependencies

• For Python versions before 3.4, the enum34 package is required

Pre-built binaries

We recommend you use the binaries provided by the Numba team for the Conda package manager. You can find them in Numba’s binstar channel <https://binstar.org/numba>. For example:

$ conda install --channel=numba llvmlite

(or, simply, the official llvmlite package provided in the Anaconda distribution)

Build

This section applies if you don’t want to use the pre-built binaries.

Run python setup.py build. This builds the llvmlite C wrapper, which contains a statically-linked copy of the required subset of LLVM.

If your LLVM is installed in a non-standard location, first point the LLVM_CONFIG environment variable to the path of the corresponding llvm-config (or llvm-config.exe) executable.

Unix requirements

You must have a LLVM 3.5 build (libraries and header files) available somewhere. Under Ubuntu 14.10 and Debian unstable, you can install llvm-3.5-dev. Versions shipped with some earlier distributions such as Ubuntu 14.04 are known to be broken.

When building on Ubuntu, the linker may report an error if the development version of libedit is not installed. Install libedit-dev if you run into this problem.

Windows requirements

You must have Visual Studio 2012 or later (the free “Express” edition is ok). In addition, you must have cmake installed, and LLVM should have been built using cmake, in Release mode. Be careful to use the right bitness (32- or 64-bit) for your Python installation.

Run tests

Run python runtests.py or python -m llvmlite.tests.

Install

Run python setup.py install.