How To Release LLVM To The Public

Introduction

This document contains information about successfully releasing LLVM — including subprojects: e.g., clang and dragonegg — 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 critial 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!

The release process will be accelerated for dot releases. If the first round of testing finds no critical bugs and no regressions since the last major release, then additional rounds of testing will not be required.

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:

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

Create Release Branch

Branch the Subversion 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 Subversion trunk is in decent shape by examining nightly tester and buildbot results.

  3. Create the release branch for llvm, clang, the test-suite, and dragonegg from the last known good revision. The branch’s name is release_XY, where X is the major and Y the minor release numbers. The branches should be created using the following commands:

    $ svn copy https://llvm.org/svn/llvm-project/llvm/trunk \
           https://llvm.org/svn/llvm-project/llvm/branches/release_XY

$ svn copy https://llvm.org/svn/llvm-project/cfe/trunk \
           https://llvm.org/svn/llvm-project/cfe/branches/release_XY

$ svn copy https://llvm.org/svn/llvm-project/dragonegg/trunk \
           https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY

$ svn copy https://llvm.org/svn/llvm-project/test-suite/trunk \
           https://llvm.org/svn/llvm-project/test-suite/branches/release_XY

  4. Advise developers that they may now check their patches into the Subversion tree again.

  5. The Release Manager should switch to the release branch, because all changes to the release will now be done in the branch. The easiest way to do this is to grab a working copy using the following commands:

    $ svn co https://llvm.org/svn/llvm-project/llvm/branches/release_XY llvm-X.Y

$ svn co https://llvm.org/svn/llvm-project/cfe/branches/release_XY clang-X.Y

$ svn co https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY dragonegg-X.Y

$ svn co https://llvm.org/svn/llvm-project/test-suite/branches/release_XY test-suite-X.Y

Update LLVM Version

After creating the LLVM release branch, update the release branches’ autoconf and configure.ac versions from ‘X.Ysvn‘ to ‘X.Y‘. Update it on mainline as well to be the next version (‘X.Y+1svn‘). Regenerate the configure scripts for both llvm and the test-suite.

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 using the tag.sh script in utils/release.

$ ./tag.sh -release X.Y.Z -rc $RC

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

$ ./export.sh -release X.Y.Z -rc $RC

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

Building the Release

The builds of llvm, clang, and dragonegg must be free of errors and warnings in Debug, Release+Asserts, and Release builds. If all builds are clean, then the release passes Build Qualification.

The make options for building the different modes:

Mode Options
Debug ENABLE_OPTIMIZED=0
Release+Asserts ENABLE_OPTIMIZED=1
Release ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1

Build LLVM

Build Debug, Release+Asserts, and Release versions of llvm on all supported platforms. Directions to build llvm are here.

Build Clang Binary Distribution

Creating the clang binary distribution (Debug/Release+Asserts/Release) requires performing the following steps for each supported platform:

  1. Build clang according to the directions here.
  2. Build both a Debug and Release version of clang. The binary will be the Release build.
  3. Package clang (details to follow).

Target Specific Build Details

The table below specifies which compilers are used for each Arch/OS combination when qualifying the build of llvm, clang, and dragonegg.

Architecture OS compiler
x86-32 Mac OS 10.5 gcc 4.0.1
x86-32 Linux gcc 4.2.X, gcc 4.3.X
x86-32 FreeBSD gcc 4.2.X
x86-32 mingw gcc 3.4.5
x86-64 Mac OS 10.5 gcc 4.0.1
x86-64 Linux gcc 4.2.X, gcc 4.3.X
x86-64 FreeBSD gcc 4.2.X
ARMv7 Linux gcc 4.6.X, gcc 4.7.X

Release Qualification Criteria

A release is qualified when it has no regressions from the previous release (or baseline). Regressions are related to correctness first and performance second. (We may tolerate some minor performance regressions if they are deemed necessary for the general quality of the compiler.)

Regressions are new failures in the set of tests that are used to qualify each product and only include things on the list. Every release will have some bugs in it. It is the reality of developing a complex piece of software. We need a very concrete and definitive release criteria that ensures we have monotonically improving quality on some metric. The metric we use is described below. This doesn’t mean that we don’t care about other criteria, but these are the criteria which we found to be most important and which must be satisfied before a release can go out.

Qualify LLVM

LLVM is qualified when it has a clean test run without a front-end. And it has no regressions when using either clang or dragonegg with the test-suite from the previous release.

Qualify Clang

Clang is qualified when front-end specific tests in the llvm regression test suite all pass, clang’s own test suite passes cleanly, and there are no regressions in the test-suite.

Specific Target Qualification Details

Architecture OS clang baseline tests
x86-32 Linux last release llvm regression tests, clang regression tests, test-suite (including spec)
x86-32 FreeBSD last release llvm regression tests, clang regression tests, test-suite
x86-32 mingw none QT
x86-64 Mac OS 10.X last release llvm regression tests, clang regression tests, test-suite (including spec)
x86-64 Linux last release llvm regression tests, clang regression tests, test-suite (including spec)
x86-64 FreeBSD last release llvm regression tests, clang regression tests, test-suite
ARMv7A Linux last release llvm regression tests, clang regression tests, test-suite

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. Ask that all LLVM developers test the release in 2 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).

Ask LLVM developers to submit the test suite report and make check results to the list. Verify that there are no regressions from the previous release. The results are not used to qualify a release, but to spot other potential problems. For unsupported targets, verify that make check is at least clean.

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

If this is the second round of testing, 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.

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.
  2. During the first round of testing, patches that fix regressions or that are small and relatively risk free (verified by the appropriate code owner) are applied to the branch. Code owners are asked to be very conservative in approving patches for the branch. We reserve the right to reject any patch that does not fix a regression as previously defined.
  3. During the remaining rounds of testing, only patches that fix critical regressions may be applied.
  4. For dot releases all patches must maintain both API and ABI compatibility with the previous major release. Only bugfixes will be accepted.

Merging Patches

The utils/release/merge.sh script can be used to merge individual revisions into any one of the llvm projects. To merge revision $N into project $PROJ, do:

  1. svn co https://llvm.org/svn/llvm-project/$PROJ/branches/release_XX $PROJ.src
  2. $PROJ.src/utils/release/merge.sh --proj $PROJ --rev $N
  3. Run regression tests.
  4. cd $PROJ.src. Run the svn commit command printed out by merge.sh in step 2.

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 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. Merge both changes from mainline into the release branch.

Tag the LLVM Final Release

Tag the final release sources using the tag.sh script in utils/release.

$ ./tag.sh -release X.Y.Z -final

Update the LLVM Demo Page

The LLVM demo page must be updated to use the new release. This consists of using the new clang binary and building LLVM.

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 module from Subversion.
  2. Create a new subdirectory X.Y in the releases directory.
  3. Commit the llvm, test-suite, clang source, clang binaries, dragonegg source, and dragonegg binaries in this new directory.
  4. Copy and commit the llvm/docs and LICENSE.txt files into this new directory. The docs should be built with BUILD_FOR_WEBSITE=1.
  5. Commit the index.html to the release/X.Y directory to redirect (use from previous release).
  6. Update the releases/download.html file with the new release.
  7. Update the releases/index.html with the new release and link to release documentation.
  8. Finally, update the main page (index.html and sidebar) to point to the new release and release announcement. Make sure this all gets committed back into Subversion.

Announce the Release

Have Chris send out the release announcement when everything is finished.