dhomeier / llvmlite

A lightweight LLVM python binding for writing JIT compilers

llvmlite

A lightweight LLVM python binding for writing JIT compilers

Old llvmpy binding exposes a lot of LLVM but the mapping of C++ style memory management to python is error prone. Numba and many JIT compiler does 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

• llvmlite IR builder is pure python
• llvmlite uses LLVM assembly parser which provide better error messages (no more segfault due to bad IR construction)
• Most of llvmlite uses the LLVM C API which is small but very stable and backward compatible (low maintenance when changing LLVM version)
• The binding is not a python C-extension (no need to wrestle with Python's compiler requirement and C++11 compatibility)
• llvmlite binding memory management is explicit obj.close() or with-context
• llvmlite is quite faster in early benchmarks (the Numba test suite is twice faster)

LLVMPY Compatibility Layer

llvmlite.llvmpy.* provides a minimal LLVMPY compatibility layer.

Dependencies

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

Build dependencies

• LLVM 3.5
• A C compiler, and possibly other tools (see below)

Runtime dependencies

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

Build

Run python setup.py build. This will build the llvmlite C wrapper, which will contain 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 executable.

Unix requirements

You must have a LLVM 3.5 build (libraries and header files) available somewhere. If it is not installed in a standard location, you may have to tweak the build script. Under Ubuntu 14.10 and Debian unstable, you can install llvm-3.5-dev. Versions shipped with earlier versions (Ubuntu 14.04, Debian stable) may not be good enough.

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.