BOLT

BOLT is an open-source post-link binary optimization tool developed to speed up large applications. It does this by optimizing the application’s code layout based on performance profile samples collected during execution.

In this guide, you’ll learn how to download and install BOLT. The instructions are for Debian-based Linux distributions, but can be adapted for other Linux distributions.

Before you begin

Follow these steps:

1. Install Git

Install Git for your operating system.

Many Linux distributions include Git so you may not need to install it.

2. Install CMake

    

        
        
sudo apt install cmake -y

    

Check it is installed:

    

        
        
cmake --version

    

The output is similar to:

    

        
        cmake version 3.28.3

CMake suite maintained and supported by Kitware (kitware.com/cmake).

        
    

For more information, see CMake install guide.

3. Install Ninja

    

        
        
sudo apt install ninja-build -y

    

Check it is installed:

    

        
        
ninja --version

    

The output is similar to:

    

        
        1.11.1

        
    

4. Install Clang

    

        
        
sudo apt install clang -y

    

Check it is installed:

    

        
        
clang --version

    

The output is similar to:

    

        
        Ubuntu clang version 18.1.3 (1ubuntu1)
Target: aarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

        
    

5. Install xz-utils

    

        
        
sudo apt-get install xz-utils -y

    

Install BOLT

You can install BOLT by building the source code or by downloading a binary release from GitHub.

Build and install BOLT from source code

To build and install BOLT from source code, follow these steps:

1. Clone the repository

    

        
        
git clone https://github.com/llvm/llvm-project.git

    

2. Build BOLT and run it

    

        
        
cd llvm-project
mkdir build
cd build
cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="bolt;clang;lld"

    

    

        
        
ninja bolt

    

3. Add the path to BOLT in your .bashrc file

    

        
        
echo 'export PATH="$PATH:$HOME/llvm-project/build/bin"' >> ~/.bashrc
source ~/.bashrc

    

You are now ready to verify BOLT is installed .

Install BOLT using a binary release

To install BOLT using a binary release, follow these steps:

1. Download a binary release

For Arm Linux, use the file with ARM64 in the name:

    

        
        
wget https://github.com/llvm/llvm-project/releases/download/llvmorg-22.1.3/LLVM-22.1.3-Linux-ARM64.tar.xz

    

2. Extract the downloaded file

    

        
        
tar -xvf LLVM-22.1.3-Linux-ARM64.tar.xz

    

3. Add the path to BOLT in your .bashrc file

    

        
        
echo 'export PATH="$PATH:$HOME/LLVM-22.1.3-Linux-ARM64/bin"' >> ~/.bashrc
source ~/.bashrc

    

Verify BOLT is installed

To verify BOLT is installed, follow these steps:

1. Confirm BOLT applications perf2bolt and llvm-bolt are installed

Check the perf2bolt command:

    

        
        
perf2bolt

    

The output is similar to:

    

        
        perf2bolt: Not enough positional command line arguments specified!
Must specify at least 1 positional argument: See: perf2bolt --help

        
    

Check the llvm-bolt command:

    

        
        
llvm-bolt

    

The output is similar to:

    

        
        llvm-bolt: Not enough positional command line arguments specified!
Must specify at least 1 positional argument: See: llvm-bolt --help

        
    

2. Print the BOLT version

    

        
        
llvm-bolt --version

    

The output is similar to:

    

        
        LLVM (http://llvm.org/):
  LLVM version 22.1.3
  Optimized build.
BOLT revision e9846648fd6183ee6d8cbdb4502213fcf902a211

  Registered Targets:
    aarch64    - AArch64 (little endian)
    aarch64_32 - AArch64 (little endian ILP32)
    aarch64_be - AArch64 (big endian)
    arm64      - ARM64 (little endian)
    arm64_32   - ARM64 (little endian ILP32)
    riscv32    - 32-bit RISC-V
    riscv32be  - 32-bit big endian RISC-V
    riscv64    - 64-bit RISC-V
    riscv64be  - 64-bit big endian RISC-V
    x86        - 32-bit X86: Pentium-Pro and above
    x86-64     - 64-bit X86: EM64T and AMD64

        
    

You’ll see additional Registered Targets if you downloaded a binary release.

You are now ready to use BOLT on your Linux machine.