How To Release LLVM To The Public

1. Introduction
2. Qualification Criteria
3. Release Timeline
4. Release Process

Written by Tanya Lattner, Reid Spencer, John Criswell, & Bill Wendling

Introduction

This document contains information about successfully releasing LLVM — including subprojects: e.g., `llvm-gcc` and `clang` — to the public. It is the Release Manager's responsibility to ensure that a high quality build of LLVM is released.

Release Timeline

LLVM is released on a time based schedule — roughly every 6 months. We do not normally have dot releases because of the nature of LLVM's incremental development philosophy. That said, the only thing preventing dot releases for critical bug fixes from happening is a lack of resources — testers, machines, time, etc. And, because of the high quality we desire for LLVM releases, we cannot allow for a truncated form of release qualification.

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!

Release Process

1. Release Administrative Tasks
   1. Create Release Branch
   2. Update Version Numbers
2. Building the Release
   1. Build the LLVM Source Distributions
   2. Build LLVM
   3. Build the LLVM-GCC Binary Distribution
   4. Build the Clang Binary Distribution
   5. Target Specific Build Details
3. Release Qualification Criteria
   1. Qualify LLVM
   2. Qualify LLVM-GCC
   3. Qualify Clang
   4. Specific Target Qualification Details
4. Community Testing
5. Release Patch Rules
6. Release final tasks
   1. Update Documentation
   2. Tag the LLVM Final Release
   3. Update the LLVM Demo Page
   4. Update the LLVM Website
   5. Announce the Release

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`, `llvm-gcc-4.2`, `clang`, and the `test-suite` 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/llvm-gcc-4.2/trunk \
                  https://llvm.org/svn/llvm-project/llvm-gcc-4.2/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

       $ svn copy https://llvm.org/svn/llvm-project/cfe/trunk \
                  https://llvm.org/svn/llvm-project/cfe/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/llvm-gcc-4.2/branches/release_XY llvm-gcc-4.2-X.Y

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

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

Build the LLVM Release Candidates

Create release candidates for `llvm`, `llvm-gcc`, `clang`, and the LLVM `test-suite` by tagging the branch with the respective release candidate number. For instance, to create Release Candidate 1 you would issue the following commands:

    $ svn mkdir https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XY
    $ svn copy https://llvm.org/svn/llvm-project/llvm/branches/release_XY \
               https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XY/rc1

    $ svn mkdir https://llvm.org/svn/llvm-project/llvm-gcc-4.2/tags/RELEASE_XY
    $ svn copy https://llvm.org/svn/llvm-project/llvm-gcc-4.2/branches/release_XY \
               https://llvm.org/svn/llvm-project/llvm-gcc-4.2/tags/RELEASE_XY/rc1

    $ svn mkdir https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XY
    $ svn copy https://llvm.org/svn/llvm-project/test-suite/branches/release_XY \
               https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XY/rc1

    $ svn mkdir https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XY
    $ svn copy https://llvm.org/svn/llvm-project/cfe/branches/release_XY \
               https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XY/rc1

Similarly, Release Candidate 2 would be named `RC2` and so on. This keeps a permanent copy of the release candidate around for people to export and build as they wish. The final released sources will be tagged in the `RELEASE_XY` directory as `Final` (c.f. Tag the LLVM Final Release).

The Release Manager may supply pre-packaged source tarballs for users. This can be done with the following commands:

    $ svn export https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XY/rc1 llvm-X.Yrc1
    $ svn export https://llvm.org/svn/llvm-project/llvm-gcc-4.2/tags/RELEASE_XY/rc1 llvm-gcc4.2-X.Yrc1
    $ svn export https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XY/rc1 llvm-test-X.Yrc1
    $ svn export https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XY/rc1 clang-X.Yrc1

    $ tar -cvf - llvm-X.Yrc1        | gzip > llvm-X.Yrc1.src.tar.gz
    $ tar -cvf - llvm-test-X.Yrc1   | gzip > llvm-test-X.Yrc1.src.tar.gz
    $ tar -cvf - llvm-gcc4.2-X.Yrc1 | gzip > llvm-gcc-4.2-X.Yrc1.src.tar.gz
    $ tar -cvf - clang-X.Yrc1       | gzip > clang-X.Yrc1.src.tar.gz

Building the Release

The builds of `llvm`, `llvm-gcc`, and `clang` 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 the LLVM GCC Binary Distribution

Creating the `llvm-gcc` binary distribution (Release/Optimized) requires performing the following steps for each supported platform:

1. Build the `llvm-gcc` front-end by following the directions in the `README.LLVM` file. The front-end must be compiled with C, C++, Objective-C (Mac only), Objective-C++ (Mac only), and Fortran support.

2. Boostrapping must be enabled.

3. Be sure to build with `LLVM_VERSION_INFO=X.Y`, where `X` is the major and `Y` is the minor release numbers.

4. Copy the installation directory to a directory named for the specific target. For example on Red Hat Enterprise Linux, the directory would be named `llvm-gcc4.2-2.6-x86-linux-RHEL4`. Archive and compress the new directory.

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`, `llvm-gcc`, and `clang`.

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

Building the Release

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 `llvm-gcc` or `clang` with the `test-suite` from the previous release.

Qualify LLVM-GCC

`LLVM-GCC` is qualified when front-end specific tests in the `llvm` regression test suite all pass and there are no regressions in the `test-suite`.

We do not use the GCC DejaGNU test suite as release criteria.

Qualify Clang

`Clang` is qualified when front-end specific tests in the `llvm` dejagnu 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 | llvm-gcc baseline | clang baseline | tests
--- | --- | --- | --- | ---
x86-32 | Linux | last release | last release | llvm dejagnu, clang tests, test-suite (including spec)
x86-32 | FreeBSD | none | last release | llvm dejagnu, clang tests, test-suite
x86-32 | mingw | last release | none | QT
x86-64 | Mac OS 10.X | last release | last release | llvm dejagnu, clang tests, test-suite (including spec)
x86-64 | Linux | last release | last release | llvm dejagnu, clang tests, test-suite (including spec)
x86-64 | FreeBSD | none | last release | llvm dejagnu, clang 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 `llvm-gcc` and/or `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 `llvm-gcc` and/or `clang` source. 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.

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 avaiable 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 following procedure:

    $ svn copy https://llvm.org/svn/llvm-project/llvm/branches/release_XY \
               https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XY/Final

    $ svn copy https://llvm.org/svn/llvm-project/llvm-gcc-4.2/branches/release_XY \
               https://llvm.org/svn/llvm-project/llvm-gcc-4.2/tags/RELEASE_XY/Final

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

    $ svn copy https://llvm.org/svn/llvm-project/cfe/branches/release_XY \
               https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XY/Final

Update the LLVM Demo Page

The LLVM demo page must be updated to use the new release. This consists of using the new `llvm-gcc` 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`, `llvm-gcc` source, `clang source`, `clang binaries`, and `llvm-gcc` 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.