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A set of scripts to build LLVM and binutils
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README.md
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README.md

Toolchain build scripts

There are times where a tip of tree LLVM build will have some issue fixed and it isn't available to you, maybe because it isn't in a release or it isn't available through your distribution's package management system. At that point, to get that fix, LLVM needs to be compiled, which sounds scary but is rather simple. The build-llvm.py script takes it a step farther by trying to optimize both LLVM's build time by:

  • Trimming down a lot of things that kernel developers don't care about:
    • Documentation
    • LLVM tests
    • Ocaml bindings
    • libfuzzer
  • Building with the faster tools available (in order of fastest to slowest):
    • clang + lld
    • clang/gcc + ld.gold
    • clang/gcc + ld.bfd

Getting started

These scripts have been tested in a Docker image of the following distributions, with the following packages installed:

  • Debian/Ubuntu

    apt install ca-certificates ccache clang cmake curl file gcc g++ git make ninja-build python3 texinfo zlib1g-dev
    

    On Debian Buster or Ubuntu Bionic/Cosmic/Disco, apt install lld should be added as well for faster compiles.

  • Fedora

    dnf install ccache clang cmake gcc gcc-c++ git lld make ninja-build python3 zlib-devel
    
  • Arch Linux

    pacman -S base-devel ccache clang cmake git lld ninja python3
    

If you intend to compile with PGO, please ensure that you also have bc, bison,flex, and libssl-dev (or equivalent) installed as you will be building some Linux kernels. If you are building for PowerPC (which the script does by default), make sure mkimage is available as well; the package is u-boot-tools on Debian/Ubuntu.

Python 3.5.3+ is recommended, as that is what the script has been tested against. These scripts should be distribution agnostic. Please feel free to add different distribution install commands here through a pull request.

build-llvm.py

By default, ./build-llvm.py will clone LLVM, grab the latest binutils tarball (for the LLVMgold.so plugin), and build LLVM, clang, and lld, and install them into install. Run ./build-llvm.py -h for more options.

build-binutils.py

This script builds a standalone copy of binutils. By default, ./build-binutils.py will download binutils 2.32, build for all architectures we currently care about (arm32, aarch64, powerpc32, powerpc64le, and x86_64), and install them into install. Run ./build-binutils.py -h for more options.

Building a standalone copy of binutils might be needed because certain distributions like Arch Linux (whose options the script uses) might symlink /usr/lib/LLVMgold.so to /usr/lib/bfd-plugins (source), which can cause issues when using the system's linker for LTO (even with LD_LIBRARY_PATH):

bfd plugin: LLVM gold plugin has failed to create LTO module: Unknown attribute kind (60) (Producer: 'LLVM9.0.0svn' Reader: 'LLVM 7.0.1')

Having a standalone copy of binutils (ideally in the same folder at the LLVM toolchain so that only one PATH modification is needed) works around this without any adverse side effects. Another workaround is bind mounting the new LLVMgold.so to /usr/lib/LLVMgold.so.

Getting help

Please open an issue on this repo and include your distribution, shell, the command you ran, and the error output.

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