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 0.11.2 uses LLVM 3.2 (or at least 3.1). 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-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

  1. Get and extract LLVM 3.2 source tarball from llvm.org. Then, cd into the extracted directory.

  2. Run ./configure --enable-optimized --prefix=LLVM_INSTALL_PATH.

    Note: Without the --enable-optimized flag, debug build will be selected. Unless you are developing LLVM or llvmpy, it is recommended that the flag is used to reduce build time and binary size.

    Note: Use prefix to select the installation path. It is recommended to separate your custom build from the default system package. Please replace LLVM_INSTALL_PATH with your own path.

  3. Run REQUIRES_RTTI=1 make to build.

    Note: With LLVM 3.2, the default build configuration has C++ RTTI disabled. However, llvmpy requires RTTI.

  4. Get llvm-py and install it:

    $ git clone git@github.com:llvmpy/llvmpy.git
    $ cd llvmpy
    $ LLVM_CONFIG_PATH=LLVM_INSTALL_PATH/bin/llvm-config python setup.py install

    Run the tests:

    $ python -c "import llvm; llvm.test()"
  5. See documentation at ‘http://www.llvmpy.org‘ and examples under ‘test’.

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