LLVM Propeller

Propeller is a profile-guided, relinking optimizer for warehouse-scale applications. It is built on top of LLVM and provides a framework for computing whole-program optimizations for applications built with LLVM.

For artifact evaluation, see ArtifactEvaluation/README.md

Quickstart

Prerequisites and dependencies

Operating System	Version
Ubuntu	22.04 or newer

While the Propeller build system automatically pulls in most of its dependencies, you will need to install a few packages manually:

# Common dependencies
sudo apt install -y wget lsb-release software-properties-common gnupg

# Propeller builds with Clang 19.0.0 or newer.
wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
sudo ./llvm.sh 19
export CC=clang-19
export CXX=clang++-19

# For the CMake build
sudo apt-get update && sudo apt-get install -y \
    libelf-dev \
    libssl-dev \
    libzstd-dev

Building Propeller from source

The Propeller repository provides both CMake and Bazel build configurations. The CMake build requires CMake 3.24 or newer, and the Bazel build requires Bazel 5.0 or newer.

CMake

cmake -G Ninja -B build
ninja -C build generate_propeller_profiles

# Build and run tests (optional)
ninja -C build
ninja -C build test

Bazel

bazel build //propeller:generate_propeller_profiles

# Build and run tests (optional)
bazel test //propeller/...:all

Generating a Propeller profile

./generate_propeller_profiles \
    --binary=/path/to/profiled/binary \
    --profile=/path/to/input/profile.txt \
    --cc_profile=/path/to/out/cc_profile.txt \
    --ld_profile=/path/to/out/ld_profile.txt

Propeller generates compiler profiles (cc_profile.txt) and linker profiles (ld_profile.txt). The compiler profile is used by LLVM to guide optimizations and is described in Propeller Profile Format.