How To Release LLVM To The Public

Introduction

This document contains information about successfully releasing LLVM — including sub-projects: e.g., clang and compiler-rt — to the public. It is the Release Manager’s responsibility to ensure that a high quality build of LLVM is released.

If you’re looking for the document on how to test the release candidates and create the binary packages, please refer to the How To Validate a New Release instead.

Release Timeline

LLVM is released on a time based schedule — with major releases roughly every 6 months. In between major releases there may be dot releases. The release manager will determine if and when to make a dot release based on feedback from the community. Typically, dot releases should be made if there are large number of bug-fixes in the stable branch or a critical bug has been discovered that affects a large number of users.

Unless otherwise stated, dot releases will follow the same procedure as major releases.

The release process is roughly as follows:

  • Set code freeze and branch creation date for 6 months after last code freeze date. Announce release schedule to the LLVM community and update the website.
  • Create release branch and begin release process.
  • Send out release candidate sources for first round of testing. Testing lasts 7-10 days. During the first round of testing, any regressions found should be fixed. Patches are merged from mainline into the release branch. Also, all features need to be completed during this time. Any features not completed at the end of the first round of testing will be removed or disabled for the release.
  • Generate and send out the second release candidate sources. Only critical bugs found during this testing phase will be fixed. Any bugs introduced by merged patches will be fixed. If so a third round of testing is needed.
  • The release notes are updated.
  • Finally, release!
  • Announce bug fix release schedule to the LLVM community and update the website.
  • Tag bug fix -rc1 after 4 weeks have passed.
  • Tag bug fix -rc2 4 weeks after -rc1.
  • Tag additional -rc candidates, if needed, to fix critical issues in previous -rc releases.
  • Tag final release.

Release Process

Release Administrative Tasks

This section describes a few administrative tasks that need to be done for the release process to begin. Specifically, it involves:

  • Updating version numbers,
  • Creating the release branch, and
  • Tagging release candidates for the release team to begin testing.

Create Release Branch

Branch the Git trunk using the following procedure:

  1. Remind developers that the release branching is imminent and to refrain from committing patches that might break the build. E.g., new features, large patches for works in progress, an overhaul of the type system, an exciting new TableGen feature, etc.
  2. Verify that the current git trunk is in decent shape by examining nightly tester and buildbot results.
  3. Bump the version in trunk to N.0.0git and tag the commit with llvmorg-N-init. If X is the version to be released, then N is X + 1.
$ git tag -a llvmorg-N-init
  1. Clear the release notes in trunk.
  2. Create the release branch from the last known good revision from before the version bump. The branch’s name is release/X.x where X is the major version number and x is just the letter x.
  3. All tags and branches need to be created in both the llvm/llvm-project and llvm/llvm-test-suite repos.

Update LLVM Version

After creating the LLVM release branch, update the release branches’ CMakeLists.txt versions from ‘X.0.0git’ to ‘X.0.0’.

In addition, the version numbers of all the Bugzilla components must be updated for the next release.

Tagging the LLVM Release Candidates

Tag release candidates:

$ git tag -a llvmorg-X.Y.Z-rcN

The Release Manager must supply pre-packaged source tarballs for users. This can be done with the export.sh script in utils/release.

Tarballs, release binaries, or any other release artifacts must be uploaded to GitHub. This can be done using the github-upload-release.py script in utils/release.

$ github-upload-release.py upload --token <github-token> --release X.Y.Z-rcN --files <release_files>
$ ./export.sh -release X.Y.Z -rc $RC

This will generate source tarballs for each LLVM project being validated, which can be uploaded to github for further testing.

Build The Binary Distribution

Creating the binary distribution requires following the instructions here.

That process will perform both Release+Asserts and Release builds but only pack the Release build for upload. You should use the Release+Asserts sysroot, normally under final/Phase3/Release+Asserts/llvmCore-3.8.1-RCn.install/, for test-suite and run-time benchmarks, to make sure nothing serious has passed through the net. For compile-time benchmarks, use the Release version.

The minimum required version of the tools you’ll need are here

Release Qualification Criteria

There are no official release qualification criteria. It is up to the the release manager to determine when a release is ready. The release manager should pay attention to the results of community testing, the number of outstanding bugs, and then number of regressions when determining whether or not to make a release.

The community values time based releases, so releases should not be delayed for too long unless there are critical issues remaining. In most cases, the only kind of bugs that are critical enough to block a release would be a major regression from a previous release.

Official Testing

A few developers in the community have dedicated time to validate the release candidates and volunteered to be the official release testers for each architecture.

These will be the ones testing, generating and uploading the official binaries to the server, and will be the minimum tests necessary for the release to proceed.

This will obviously not cover all OSs and distributions, so additional community validation is important. However, if community input is not reached before the release is out, all bugs reported will have to go on the next stable release.

The official release managers are:

  • Major releases (X.0): Hans Wennborg
  • Stable releases (X.n): Tom Stellard

The official release testers are volunteered from the community and have consistently validated and released binaries for their targets/OSs. To contact them, you should email the release-testers@lists.llvm.org mailing list.

The official testers list is in the file RELEASE_TESTERS.TXT, in the LLVM repository.

Community Testing

Once all testing has been completed and appropriate bugs filed, the release candidate tarballs are put on the website and the LLVM community is notified.

We ask that all LLVM developers test the release in any the following ways:

  1. Download llvm-X.Y, llvm-test-X.Y, and the appropriate clang binary. Build LLVM. Run make check and the full LLVM test suite (make TEST=nightly report).
  2. Download llvm-X.Y, llvm-test-X.Y, and the clang sources. Compile everything. Run make check and the full LLVM test suite (make TEST=nightly report).
  3. Download llvm-X.Y, llvm-test-X.Y, and the appropriate clang binary. Build whole programs with it (ex. Chromium, Firefox, Apache) for your platform.
  4. Download llvm-X.Y, llvm-test-X.Y, and the appropriate clang binary. Build your programs with it and check for conformance and performance regressions.
  5. Run the release process, if your platform is different than that which is officially supported, and report back errors only if they were not reported by the official release tester for that architecture.

We also ask that the OS distribution release managers test their packages with the first candidate of every release, and report any new errors in Bugzilla. If the bug can be reproduced with an unpatched upstream version of the release candidate (as opposed to the distribution’s own build), the priority should be release blocker.

During the first round of testing, all regressions must be fixed before the second release candidate is tagged.

In the subsequent stages, the testing is only to ensure that bug fixes previously merged in have not created new major problems. This is not the time to solve additional and unrelated bugs! If no patches are merged in, the release is determined to be ready and the release manager may move onto the next stage.

Reporting Regressions

Every regression that is found during the tests (as per the criteria above), should be filled in a bug in Bugzilla with the priority release blocker and blocking a specific release.

To help manage all the bugs reported and which ones are blockers or not, a new “[meta]” bug should be created and all regressions blocking that Meta. Once all blockers are done, the Meta can be closed.

If a bug can’t be reproduced, or stops being a blocker, it should be removed from the Meta and its priority decreased to normal. Debugging can continue, but on trunk.

Merge Requests

You can use any of the following methods to request that a revision from trunk be merged into a release branch:

  1. Use the utils/release/merge-request.sh script which will automatically file a bug requesting that the patch be merged. e.g. To request revision 12345 be merged into the branch for the 5.0.1 release: llvm.src/utils/release/merge-request.sh -stable-version 5.0 -r 12345 -user bugzilla@example.com
  2. Manually file a bug with the subject: “Merge r12345 into the X.Y branch”, enter the commit(s) that you want merged in the “Fixed by Commit(s)” and mark it as a blocker of the current release bug. Release bugs are given aliases in the form of release-x.y.z, so to mark a bug as a blocker for the 5.0.1 release, just enter release-5.0.1 in the “Blocks” field.
  3. Reply to the commit email on llvm-commits for the revision to merge and cc the release manager.

Release Patch Rules

Below are the rules regarding patching the release branch:

  1. Patches applied to the release branch may only be applied by the release manager, the official release testers or the code owners with approval from the release manager.
  2. Release managers are encouraged, but not required, to get approval from code owners before approving patches. If there is no code owner or the code owner is unreachable then release managers can ask approval from patch reviewers or other developers active in that area.
  3. Before RC1 Patches should be limited to bug fixes, important optimization improvements, or completion of features that were started before the branch was created. As with all phases, release managers and code owners can reject patches that are deemed too invasive.
  4. Before RC2 Patches should be limited to bug fixes or backend specific improvements that are determined to be very safe.
  5. Before RC3/Final Major Release Patches should be limited to critical bugs or regressions.
  6. Bug fix releases Patches should be limited to bug fixes or very safe and critical performance improvements. Patches must maintain both API and ABI compatibility with the previous major release.

Merging Patches

Use the git cherry-pick -x command to merge patches to the release branch:

  1. git cherry-pick -x abcdef0
  2. Run regression tests.

Release Final Tasks

The final stages of the release process involves tagging the “final” release branch, updating documentation that refers to the release, and updating the demo page.

Update Documentation

Review the documentation in the release branch and ensure that it is up to date. The “Release Notes” must be updated to reflect new features, bug fixes, new known issues, and changes in the list of supported platforms. The “Getting Started Guide” should be updated to reflect the new release version number tag available from Subversion and changes in basic system requirements.

Tag the LLVM Final Release

Tag the final release sources:

$ git tag -a llvmorg-X.Y.Z
$ git push https://github.com/llvm/llvm-project.git llvmorg-X.Y.Z

Update the LLVM Website

The website must be updated before the release announcement is sent out. Here is what to do:

  1. Check out the www-releases module from GitHub.
  2. Create a new sub-directory X.Y.Z in the releases directory.
  3. Copy and commit the llvm/docs and LICENSE.txt files into this new directory.
  4. Update the releases/download.html file with links to the release binaries on GitHub.
  5. Update the releases/index.html with the new release and link to release documentation.
  6. Finally checkout the llvm-www repo and update the main page (index.html and sidebar) to point to the new release and release announcement.

Announce the Release

Send an email to the list announcing the release, pointing people to all the relevant documentation, download pages and bugs fixed.