Installing LLVM Compiler Infrastructure

This blog walks you through how to install LLVM Compiler Infrastructure from scratch

Prerequisites

• I assume you have installed git in your system

  sudo apt install git-all  # To install git

• Running a Linux Machine (This installation tested on Ubuntu 20 LTS)
• Make sure you have sufficient storage (around 20 GB free)
• While building, your CPU might freeze; it better to close all programs before installation.

Clone (Check out) the llvm source from git repository

We first need to clone the repository. To save space, we do a shallow clone. If you want the complete source code, go check this link Getting the source code and building LLVM Doing this will also pull llvm subprojects such as Clang and others.

Create a directory and clone

Create a new directory in your home folder

mkdir llvm
cd llvm
git clone --depth 1 https://github.com/llvm/llvm-project.git

Configure and build LLVM and Clang

Once you have clone successfully, you can now execute the following commands in your terminal.

cd llvm-project
mkdir build
cd build
cmake -G Ninja ../llvm

Note that -G Ninja is a build system generator; you can choose others as well. Check the official documentation ¹ if you would like to build llvm other than Ninja

If you haven’t installed cmake, go ahead and install it

sudo apt install cmake

Once done, run.

 cmake -G Ninja ../llvm

If you haven’t installed Ninja, you will get errors as follows:

Error: CMake was unable to find a build program corresponding to "Ninja". 

CMAKE_MAKE_PROGRAM is not set. You probably need to select a different build tool. CMake 

Error: CMAKE_C_COMPILER not set, after EnableLanguage CMake Error: CMAKE_CXX_COMPILER not 

set, after EnableLanguage CMake Error: CMAKE_ASM_COMPILER not set, after EnableLanguage -- Configuring incomplete, errors occurred!

Install Ninja

sudo apt-get install -y ninja-build

Once done, run the following command to generate the build files.

 cmake -G Ninja ../llvm

Building llvm and clang

cmake --build  .

This might takes hours, depending on your machine.

It took 1 hr (approx) in my machine (Intel Xeon, 32GB Ram).

I also encountered an error in linking, error similar to the following

FAILED: lib/libLTO.so.13git

Do the following ²

cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_PARALLEL_LINK_JOBS=1 ../llvm
cmake --build .

This error happens likely that you’re running out of memory ².