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Contributing to IREElink

We'd love to accept your patches and contributions to this project.

Note - coordinating efforts

Please file issues or reach out on any of our other communication channels before doing substantial work; this will ensure that others don't duplicate the work and that there's a chance to discuss any design issues.

Developer policieslink

Code of conductlink

This project follows the OpenXLA Code of Conduct.

Contributor License Agreementlink

Contributions to this project must be accompanied by a Contributor License Agreement (CLA). Head over to to see your current agreements on file or to sign a new one.

  • You (or your employer) retain the copyright to your contribution; this simply gives us permission to use and redistribute your contributions as part of the project.
  • You generally only need to submit a CLA once, so if you've already submitted one (even if it was for a different project), you probably don't need to do it again.

Coding style guidelineslink

Most of the code style is derived from the Google Style Guides for the appropriate language and is generally not something we accept changes on (as clang-format and other linters set that for us). The C++ compiler portion of the project follows the MLIR/LLVM style guide.

Improvements to code structure and clarity are welcome but please file issues to track such work first. Pure style changes are unlikely to be accepted unless they are applied consistently across the project.

Tip - code formatters and lint scripts

Formatters like clang-format (C/C++) and Black (Python) can be set to run automatically in your editor of choice.

The script at build_tools/scripts/ can also be used to run the full suite of lint checks.

Code reviewslink

All submissions, including submissions by maintainers, require review. We use GitHub pull requests (PRs) for this purpose. Consult GitHub Help for more information on using pull requests.

  • Please keep PRs small (focused on a single issue) to make reviews and later culprit-finding easier.
  • You may see trusted core contributors bending this rule for project maintenance and major subsystem renovation. If you feel like the rules aren't working for a certain situation, please ask as we bias towards pragmatism for cases that require it.

Testing policylink

With few exceptions, features should be accompanied by automated tests.

We use a mix of in-tree and out-of-tree unit and integration tests. For more information about the types of tests used across the project, refer to the testing guide.

GitHub Actions workflowslink

We use GitHub Actions to automatically build and test various parts of the project.

  • Most presubmit workflows will only run automatically on PRs if you are a project collaborator. Otherwise a maintainer must approve workflow runs. If you are sending code changes to the project, please ask to be added as a collaborator, so that these can run automatically.
  • It is generally expected that PRs will only be merged when all checks are passing. In some cases, pre-existing failures may be bypassed by a maintainer.
Tip - adjusting workflow behavior

Some workflows only run on commits after they are merged. See the CI behavior manipulation section below to learn how to customize this behavior.

Merging approved changeslink

After review and presubmit checks, PRs should typically be merged using "squash and merge".

  • The squashed commit summary should match the PR title and the commit description should match the PR body (this is the default behavior). Accordingly, please write these as you would a helpful commit message.

It is assumed that the PR author will merge their change unless they ask someone else to merge it for them (e.g. because they don't have write access yet).

Obtaining commit accesslink

Access to affiliated repositories is divided into tiers:

Tier Description Team link
Triage New project members should typically start here
Can be assigned issues
Can apply labels to issues / PRs
Can run workflows without approval
Write Established project contributors should request this access
Can merge approved pull requests
Can create branches
Maintain/Admin Can edit repository settings
Can push to protected branches
Added case-by-case

All access tiers first require joining the iree-org GitHub organization.

Fill out this form to request access

Once you are a member of the iree-org GitHub organization, you can request to join any of the teams on

Note: other GitHub organizations

Work on IREE sometimes spans other GitHub organizations like shark-infra. Reach out to a project member if you would also like access to repositories in those organizations.

Credits in the AUTHORS filelink

If you would like additional recognition for your contributions, you may add yourself or your organization to the AUTHORS file that keeps track of those who have made significant contributions to the project.

  • Please add the entity who owns the copyright for your contribution.
  • The source control history remains the most accurate source for individual contributions.

Tips for contributorslink

Tool recommendationslink

Program or tool Description
Visual Studio Code (VSCode) The most commonly used editor amongst IREE developers
Ccache A fast C/C++ compiler cache. See the CMake with ccache page
GitHub CLI A CLI for interacting with GitHub
"Refined GitHub" browser extensions Extension that add features to the GitHub UI

Build systemslink

IREE supports building from source with both Bazel and CMake.

  • CMake is the preferred build system and offers the most flexible configuration options
  • Bazel is a stricter build system and helps with usage in Google's downstream source repository
  • Certain dependencies (think large/complex projects like CUDA, TensorFlow, PyTorch, etc.) may be difficult to support with one build system or the other, so the project may configure these as optional

Continuous integration (CI)link

IREE uses GitHub Actions for CI. The primary CI is configured in the ci.yml workflow file.

Self-hosted runnerslink

In addition to the default runners GitHub provides, IREE uses self-hosted runners to run many of its workflow jobs. These enable access to additional compute and custom configurations such as accelerators. Configuration scripting is checked in to this repository (see the README for that directory).

Custom managed runnerslink

In addition to our self-hosted runners, we use GitHub's large managed runners for some platforms.

CI behavior manipulationlink

The setup step of the CI determines which CI jobs to run. This is controlled by the script. It will generally run a pre-determined set of jobs on presubmit with some jobs kept as post-submit only. If changes are only to a certain set of excluded files that we know don't affect CI (e.g. Markdown files), then it will skip the jobs.

You can customize which jobs run using git trailers in the PR description.

The available options are

ci-skip: jobs,to,skip
ci-extra: extra,jobs,to,run
ci-exactly: exact,set,of,jobs,to,run
skip-ci: free form reason
skip-llvm-integrate-benchmark: free form reason
benchmark-extra: extra,benchmarks,to,run
runner-env: [testing|prod]
Using skip-ci

skip-ci skips all jobs. It is mutually exclusive with the other ci-* options and is synonomous with ci-skip: all.

skip-ci: free form reason
Using ci-skip, ci-extra, ci-exactly

The ci-* options instruct the setup script on which jobs to include or exclude from its run. They take a comma-separated list of jobs which must be from the set of top-level job identifiers in the ci.yml file or the special keyword "all" to indicate all jobs.

ci-skip: jobs,to,skip
ci-extra: extra,jobs,to,run
ci-exactly: exact,set,of,jobs,to,run
  • ci-skip removes jobs that would otherwise be included, though it is not an error to list jobs that would not be included by default.
  • ci-extra adds additional jobs that would not have otherwise been run, though it is not an error to list jobs that would have been included anyway. It is an error to list a job in both "skip" and "extra".
  • ci-exactly provides an exact list of jobs that should run. It is mutually exclusive with both "skip" and "extra".

In all these cases, the setup does not make any effort to ensure that job dependencies are satisfied. Thus, if you request skipping the build_all job, all the jobs that depend on it will fail, not be skipped.

Using benchmark-extra, skip-llvm-integrate-benchmark
benchmark-extra: extra,benchmarks,to,run
skip-llvm-integrate-benchmark: free form reason

Benchmarks don't run by default on PRs, and must be specifically requested.

The benchmark-extra option allows specifying additional benchmark presets to run as part of benchmarking. It accepts a comma-separated list of benchmark presets. This combines with labels added to the PR (which are a more limited set of options). See the benchmark suites documentation.

Benchmarks do run by default on PRs detected to be an integration of LLVM into IREE, but this behavior can be disabled with skip-llvm-integrate-benchmark.

Using runner-env

The runner-env option controls which runner environment to target for our self-hosted runners. We maintain a test environment to allow testing out new configurations prior to rolling them out. This trailer is for advanced users who are working on the CI infrastructure itself.

runner-env: [testing|prod]
CI configuration recipeslink

Copy/paste any of these at the bottom of a PR description to change what the CI runs.

  • Also run Windows and macOS builds that are normally post-merge only:

    ci-extra: build_test_all_windows,build_test_all_macos_arm64,build_test_all_macos_x86_64
  • Also run GPU tests on NVIDIA A100 runners (opt-in due to low availability):

    ci-extra: test_nvidia_a100
  • Skip all CI builds and tests, e.g. for comment-only changes:

    skip-ci: Comment-only change.
  • Only run Bazel builds, e.g. for changes only affecting Bazel rules:

    ci-exactly: build_test_all_bazel

For example, this PR opted in to running the build_test_all_windows job:


The enabled jobs can be viewed from the Summary page of an action run:


Git workflowslink

We tend to use the "triangular" or "forking" workflow. Develop primarily on a clone of the repository on your development machine. Any local branches named the same as persistent branches from the main repository are pristine (though potentially stale) copies. You only fastforward these to match upstream and otherwise do development on other branches. When sending PRs, you push to a different branch on your public fork and create the PR from there.


  1. Create a fork of the main repository.

  2. Create a local git repository with remotes upstream (the main repository) and origin (your personal fork). To list your current remotes git remote -v.

    a. If you already cloned from the main repository (e.g. by following the getting started guide):

    # From your existing git repo
    $ git remote rename origin upstream
    $ git remote add origin<github_username>/iree.git

    b. If you haven't already cloned:

    # From whatever directory under which you want to nest your repo
    $ git clone<github_username>/iree.git
    $ cd iree
    $ git remote add upstream

    This is especially important for maintainers who have write access (so can push directly to the main repository) and admins who have elevated privileges (so can push directly to protected branches).

    These names are just suggestions, but you might find some scripts where the defaults are for remotes named like this.

    For extra safety, you can make it difficult to push directly to upstream by setting the push url to something invalid: git remote set-url --push upstream DISABLE, which requires re-enabling the push URL explicitly before pushing. You can wrap this behavior in a custom git command like git-sudo.

  3. Use a script like to easily synchronize main with upstream. Submodules make this is a little trickier than it should be. You can also turn this into a git command by adding it to your path as git-update.

Git configlink

These are some additional options you could put in your top-level .gitconfig or repository-specific .git/config files that are conducive the recommended workflow

  default = current
  # Delete branches that you pushed and have been deleted upstream, e.g. because
  # the PR was merged.
  gone = ! "git fetch -p  && git for-each-ref --format '%(refname:short) %(upstream:track)' | awk '$2 == \"[gone]\" {print $1}' | xargs -r git branch -D"
  # Update from upstream (custom command) and delete obsolete local branches.
  sync = ! (git update main && git gone)
  # Create a new branch based off of main (requires a clean working directory).
  new = "!f(){ \\\ngit checkout main && git switch -c $1; \\\n}; f"
  # Display branches in a useful "latest last" format
  br = for-each-ref --sort=committerdate refs/heads/ --format='%(HEAD) %(color:yellow)%(refname:short)%(color:reset) - %(color:red)%(objectname:short)%(color:reset) - %(contents:subject) (%(color:green)%(committerdate:relative)%(color:reset))'
  # `git git foo` -> `git foo` typo fixer
  git = "!f(){ \\\n git \"$@\"; \\\n}; f"
  # Get the git root directory
  root = rev-parse --show-toplevel
  # checkout, but also sync submodules
  ch = "!f() { \\\n git checkout \"$@\"; git submodule sync && git submodule update --init; \\\n}; f"
  # See the diff for a PR branch vs the main branch
  diffmain = diff --merge-base main
  # See only the files that differ vs the main branch
  whatsout = diffmain --name-only
  # If the checkout command
  defaultRemote = origin
  # When pulling, only complete the pull if its a clean fast forward.
  ff = only
  # Push to your fork (origin) by default
  pushDefault = origin
[url "ssh://"]
  # Pull with https (so no auth required), but push with ssh.
  pushInsteadOf =