Installation

std::offload is partly available in nightly builds for users. For now, everyone however still needs to build rustc from source to use all features of it.

Build instructions

First you need to clone and configure the Rust repository:

git clone git@github.com:rust-lang/rust
cd rust
./configure --enable-llvm-link-shared --release-channel=nightly --enable-llvm-assertions --enable-llvm-offload --enable-llvm-enzyme --enable-clang --enable-lld --enable-option-checking --enable-ninja --disable-docs

Afterwards you can build rustc using:

./x build --stage 1 library

Afterwards rustc toolchain link will allow you to use it through cargo:

rustup toolchain link offload build/host/stage1
rustup toolchain install nightly # enables -Z unstable-options

Build instruction for LLVM itself

git clone git@github.com:llvm/llvm-project
cd llvm-project
mkdir build
cd build
cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="host;AMDGPU;NVPTX" -DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="offload;openmp" -DLLVM_ENABLE_PLUGINS=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=.
ninja
ninja install

This gives you a working LLVM build.

Testing

Run this test script for offload-specific tests:

./x test --stage 1 tests/codegen-llvm/gpu_offload

For testing the CI locally, you may use the commands outlined in Testing with Docker:

cargo run --manifest-path src/ci/citool/Cargo.toml run-local dist-x86_64-linux

This stores all compiler artifacts in the obj directory, however should you modify rustc-specific code, you may need to delete this directory as the Docker image will cache its state otherwise.

Submodules should also be checked out at this point.