Introduction

LLVM (Low-Level Virtual Machine) provides enough infrastructure to use it as the backend for your compiled, or JIT-compiled language. It provides extensive optimization support, and static and dynamic (JIT) backends for many platforms. See the website at http://www.llvm.org/ to discover more.

Python bindings for LLVM provides a gentler learning curve for working with the LLVM APIs. It should also be easier to create working prototypes and experimental languages using this medium.

Together with clang or llvm-gcc it also a provides a means to quickly instrument C and C++ sources. For e.g., llvm-gcc can be used to generate the LLVM assembly for a given C source file, which can then be loaded and manipulated (adding profiling code to every function, say) using a llvmpy based Python script.

License

Both LLVM and llvmpy are distributed under (different) permissive open source licenses. llvmpy uses the new BSD license. More information is available here.

Platforms

llvmpy has been built/tested/reported to work on various GNU/Linux flavours, BSD, Mac OS X; on i386 and amd64 architectures. Windows is not supported, for a variety of reasons.

Versions

llvmpy 0.9 requires version 3.1 of LLVM. It may not work with previous versions.

llvmpy has been built and tested with Python 2.7 and 3.2. It should work with earlier versions.

Installation

The Git repo of llvmpy is at https://github.com/llvmpy/llvmpy.git. You’ll need to build and install it before it can be used. At least the following will be required for this:

  • C and C++ compilers (gcc/g++)
  • Python itself
  • Python development files (headers and libraries)
  • LLVM, either installed or built

On debian-based systems, the first three can be installed with the command sudo apt-get install gcc g++ python python-dev. Ensure that your distro’s repository has the appropriate version of LLVM!

It does not matter which compiler LLVM itself was built with (g++, llvm-g++ or any other); llvmpy can be built with any compiler. It has been tried only with gcc/g++ though.

LLVM and --enable-pic

The result of an LLVM build is a set of static libraries and object files. The llvmpy contains an extension package that is built into a shared object (_core.so) which links to these static libraries and object files. It is therefore required that the LLVM libraries and object files be built with the -fPIC option (generate position independent code). Be sure to use the --enable-pic option while configuring LLVM (default is no PIC), like this:

$ ~/llvm ./configure --enable-pic --enable-optimized

llvm-config

In order to build llvmpy, it’s build script needs to know from where it can invoke the llvm helper program, llvm-config. If you’ve installed LLVM, then this will be available in your PATH, and nothing further needs to be done. If you’ve built LLVM yourself, or for any reason llvm-config is not in your PATH, you’ll need to pass the full path of llvm-config to the build script.

You’ll need to be ‘root’ to install llvmpy. Remember that your PATH is different from that of ‘root’, so even if llvm-config is in your PATH, it may not be available when you do sudo.

Steps

Get 3.1 version of LLVM, build it. Make sure ‘–enable-pic’ is passed to LLVM’s ‘configure’.

Get llvmpy and install it:

$ git clone git@github.com:numba/llvmpy.git
$ cd llvmpy $ python setup.py install

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