How To Release LLVM To The Public

1. Introduction
2. Release Timeline
3. Release Process
4. Distribution Targets

Written by Reid Spencer, John Criswell, Tanya Lattner

Introduction

This document collects information about successfully releasing LLVM to the public. It is the release manager's guide to ensuring that a high quality build of LLVM is released.

The following is the basic criteria for releasing LLVM:

1. Successful configure and build.
2. Clean 'make check'.
3. No regressions in the testsuite from the previous release. This may include performance regressions for major benchmarks.

Release Timeline
The release manager should attempt to have a release every 3-4 months because LLVM does time based releases (instead of feature based). The release schedule should be roughly as follows:

1. Set code freeze and branch creation date for 3 months after last release date. Announce release schedule to the LLVM community and update the website.
2. Create release branch and begin release process.
3. Send out pre-release for first round of testing. Testing will last 7-10 days. During the first round of testing, regressions should be found and fixed. Patches are merged from mainline to the release branch.
4. Generate and send out second pre-release. Bugs found during this time will not be fixed unless absolutely critical. Bugs introduce by patches merged in will be fixed and if so, a 3rd round of testing is needed.
5. The release notes should be updated during the first and second round of pre-release testing.
6. Finally, release!

Release Process
Process Overview

1. Create Release Branch
2. Update LLVM Version
3. Build the LLVM Source Distributions
4. Build LLVM
5. Build the LLVM GCC Binary Distribution
6. Build RPM Packages (optional)
7. Run 'make check'
8. Run LLVM Test Suite
9. Pre-Release Testing
10. Tag the LLVM Release Branch
11. Update Documentation
12. Update the LLVM Demo Page
13. Update the LLVM Website
14. Announce the Release

Create Release Branch

Branch the Subversion HEAD using the following procedure:

1. Verify that the current Subversion HEAD is in decent shape by examining nightly tester results.

2. Request all developers to refrain from committing. Offenders get commit rights taken away (temporarily).

3. Create the release branch for `llvm`, `llvm-gcc4.2`, and the `test-suite`. The branch name will be `release_XX`, where `XX` is the major and minor release numbers. These branches can be created without checking out anything from subversion.

       svn copy https://llvm.org/svn/llvm-project/llvm/trunk \
                https://llvm.org/svn/llvm-project/llvm/branches/release_XX
       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_XX
       svn copy https://llvm.org/svn/llvm-project/test-suite/trunk \
                https://llvm.org/svn/llvm-project/test-suite/branches/release_XX

4. Advise developers they can work on Subversion HEAD again.

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

       svn co https://llvm.org/svn/llvm-project/llvm/branches/release_XX
       svn co https://llvm.org/svn/llvm-project/llvm-gcc-4.2/branches/release_XX
       svn co https://llvm.org/svn/llvm-project/test-suite/branches/release_XX

Update LLVM Version

After creating the LLVM release branch, update the release branches' autoconf/configure.ac version from X.Xsvn to just X.X. Update it on mainline as well to be the next version (X.X+1svn). Regenerated the configure script for both. This must be done for both llvm and the test-suite.

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

Build the LLVM Source Distributions

Create source distributions for LLVM, LLVM GCC, and the LLVM Test Suite by exporting the source from Subversion and archiving it. This can be done with the following commands:

    svn export https://llvm.org/svn/llvm-project/llvm/branches/release_XX llvm-X.X
    svn export https://llvm.org/svn/llvm-project/llvm-gcc-4.2/branches/release_XX llvm-gcc4.2-X.X.source
    svn export https://llvm.org/svn/llvm-project/test-suite/branches/release_XX llvm-test-X.X
    tar -cvf - llvm-X.X          | gzip > llvm-X.X.tar.gz
    tar -cvf - llvm-test-X.X     | gzip > llvm-test-X.X.tar.gz
    tar -cvf - llvm-gcc4.2-X.X.source | gzip > llvm-gcc-4.2-X.X.source.tar.gz

Build LLVM

Build both debug and release (optimized) versions of LLVM on all platforms. Ensure the build is warning and error free on each platform. Note that when building the LLVM GCC Binary, use a release build of LLVM.

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. Be sure to build with LLVM_VERSION_INFO=X.X, where X is the major and minor release numbers.
2. 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-gcc4.0-2.1-x86-linux-RHEL4`. Archive and compress the new directory.

Run 'make check'

Using the newly built llvm-gcc and llvm, reconfigure llvm to locate llvm-gcc. Run `make check` and ensure there are no unexpected failures. If there are, resolve the failures or file a bug. If there is a fix commited to mainline, merge back into the release branch, and restart testing by re-building LLVM and llvm-gcc. If no fix will be made, XFAIL the test and commit back to the release branch.

Ensure that '`make check`' passes on all platforms for all targets. The test suite must complete with "0 unexpected failures" before sending out the pre-releases for testing.

LLVM Test Suite

Run the `llvm-test` suite and ensure there are no unacceptable failures. Unacceptable failures are regression from the previous release and (optionally) major performance regressions from the previous release. If a regression is found a bug is filled, but the pre-releases may still go out.

Building RPM packages (optional)

You can, optionally, create source and binary RPM packages for LLVM. These may make it easier to get LLVM into a distribution. This can be done with the following commands:

    make dist        # Build the distribution source tarball
    make dist-check  # Check that the source tarball can build itself.
    cp llvm-M.m.tar.gz /usr/src/redhat/SOURCES  # Required by rpmbuild
    make srpm # for source rpm
    make rpm  # for binary rpm

First, use `make dist` to simply build the distribution. Any failures need to be corrected (on the branch). Once `make dist` can be successful, do `make dist-check`. This target will do the same thing as the 'dist' target but also test that distribution to make sure it can build itself and runs `make check` as well. This ensures that needed files are not missing and that the src tarball can be successfully unpacked, built, installed, and cleaned. Once you have a reliable tarball, you need to copy it to the `/usr/src/redhat/SOURCES` directory which is a requirement of the rpmbuild tool. The last two `make` invocations just run rpmbuild to build either a source (`srpm`) or binary (`rpm`) RPM package.

Pre-Release Testing

Once all testing has been completed and appropriate bugs filed, the pre-release tar balls may be 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.X, llvm-test-X.X, and the appropriate llvm-gcc4 binary. Run "make check" and the full llvm-test suite (make TEST=nightly report).
3. Download llvm-X.X, llvm-test-X.X, and the llvm-gcc4 source. Compile everything. Run "make check" and the full llvm-test suite (make TEST=nightly report).

Ask LLVM developers to submit the report and make check results to the list. Verify that there are no regressions from the previous release. For unsupported targets, verify that make check at least is clean.

The first round of pre-release testing will be the longest. During this time, all regressions must be fixed before the second pre-release is created (repeat steps 4-8).

If this is the second round of testing, this is only to ensure the 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 step.

Tag the Release Branch

Tag the release branch using the following procedure:

    svn copy https://llvm.org/svn/llvm-project/llvm/branches/release_XX \
             https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XX
    svn copy https://llvm.org/svn/llvm-project/llvm-gcc-4.2/branches/release_XX \
             https://llvm.org/svn/llvm-project/llvm-gcc-4.2/tags/RELEASE_XX
    svn copy https://llvm.org/svn/llvm-project/test-suite/branches/release_XX \
             https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XX

Update Documentation

Review the documentation and ensure that it is up to date. The Release Notes must be updated to reflect 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.

Update the LLVM Demo Page

The LLVM demo page must be updated to use the new release. This consists of using the llvm-gcc binary and building LLVM. Update the website demo page configuration to use the new release.

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 `website` module from CVS.
2. Create a new subdirectory X.X in the releases directory.
3. Commit the `llvm`, `test-suite`, `llvm-gcc` source, 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.X 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 commited back into Subversion.

Announce the Release

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

Distribution Targets
Overview

The first thing you need to understand is that there are multiple make targets to support this feature. Here's an overview, we'll delve into the details later.

- distdir - builds the distribution directory from which the distribution will be packaged
- dist - builds each of the distribution tarballs (tar.gz, tar.bzip2, .zip). These can be built individually as well, with separate targets.
- dist-check - this is identical to `dist` but includes a check on the distribution that ensures the tarball can: unpack successfully, compile correctly, pass '`make check`', and pass '`make clean`'.
- dist-clean- this just does a normal clean but also cleans up the stuff generated by the other three `dist` targets (above).

Okay, that's the basic functionality. When making a release, we want to ensure that the tree you build the distribution from passes `dist-check`. Beyond fixing the usual bugs, there is generally one impediment to making the release in this fashion: missing files. The `dist-check` process guards against that possibility. It will either fail and that failure will indicate what's missing, or it will succeed meaning that it has proved that the tarballs can actually succeed in building LLVM correctly and that it passes `make check`.

distdir

This target builds the distribution directory which is the directory from which the tarballs are generated. The distribution directory has the same name as the release, e.g. LLVM-1.7). This target goes through the following process:

1. First, if there was an old distribution directory (for the current release), it is removed in its entirety and you see `Removing old LLVM-1.7`
2. Second, it issues a `make all ENABLE_OPTIMIZED=3D1` to ensure that the everything in your tree can be built in release mode. Often times there are discrepancies in building between debug and release modes so it enforces release mode first. If that fails, the `distdir` target fails too. This is preceded by the message `Making 'all' to verify build`.
3. Next, it traverses your source tree and copies it to a new directory that has the name of the release (`LLVM-M.m` in our current case). This is the directory that will get tar'd. It contains all the software that needs to be in the distribution. During the copying process, it omits generated files, SVN directories, and any other "cruft" that's in your build tree. This is done to eliminate the possibility of huge distribution tarballs that include useless or irrelevant stuff in them. This is the trickiest part of making the distribution. Done manually you will either include stuff that shouldn't be in the distribution or exclude stuff that should. This step is preceded by the message `Building Distribution Directory LLVM-1.7`
4. The distribution directory is then traversed and all `CVS` or `.svn` directories are removed. You see: `Eliminating CVS/.svn directories from distribution`
5. The recursive `dist-hook` target is executed. This gives each directory a chance to modify the distribution in some way (more on this below).
6. The distribution directory is traversed and the correct file permissions and modes are set based on the type of file.

To control the process of making the distribution directory correctly, each Makefile can utilize two features:

1. `EXTRA_DIST` - this make variable specifies which files it should distribute. By default, all source files are automatically included for distribution as well as certain `well known` files (see DistAlways variable in Makefile.rules for details). Each Makefile specifies, via the `EXTRA_DIST` variable, which additional files need to be distributed. Only those files that are needed to build LLVM should be added to `EXTRA_DIST`. `EXTRA_DIST` contains a list of file or directory names that should be distributed. For example, the top level Makefile contains `EXTRA_DIST := test llvm.spec include`. This means that in addition to regular things that are distributed at the top level (`CREDITS.txt, LICENSE.txt`, etc.) the distribution should contain the entire `test` and `include` directories as well as the `llvm.spec` file.
2. `dist-hook` - this make target can be used to alter the content of the distribution directory. For example, in the top level Makefile there is some logic to eliminate files in the `include` subtree that are generated by the configure script. These should not be distributed. Similarly, any `dist-hook` target found in any directory can add or remove or modify things just before it gets packaged. Any transformation is permitted. Generally, not much is needed.

You will see various messages if things go wrong:

1. During the copying process, any files that are missing will be flagged with: `===== WARNING: Distribution Source 'dir/file' Not Found!` These must be corrected by either adding the file or removing it from `EXTRA_DIST`.
2. If you build the distribution with `VERBOSE=1`, then you might also see: `Skipping non-existent 'dir/file'` in certain cases where it's okay to skip the file.
3. The target can fail if any of the things it does fail. Error messages should indicate what went wrong.

dist

This target does exactly what `distdir` target does, but also includes assembling the tarballs. There are actually four related targets here:

- `dist-gzip`: package the gzipped distribution tar file. The distribution directory is packaged into a single file ending in `.tar.gz` which is gzip compressed.
- `dist-bzip2`: package the bzip2 distribution tar file. The distribution directory is packaged into a single file ending in `.tar.bzip2` which is bzip2 compressed.
- `dist-zip`: package the zip distribution file. The distribution directory is packaged into a single file ending in `.zip` which is zip compressed.
- `dist`: does all three, dist-gzip, dist-bzip2, dist-zip

dist-check

This target checks the distribution. The basic idea is that it unpacks the distribution tarball and ensures that it can build. It takes the following actions:

1. It depends on the `dist-gzip` target which, if it hasn't already been built, builds the gzip tar bundle (see dist and distdir above).
2. removes any pre-existing `_distcheckdir` at the top level.
3. creates a new `_distcheckdir` directory at the top level.
4. creates a `build` subdirectory and an `install` subdirectory under `_distcheckdir`.
5. unzips and untars the release tarball into `_distcheckdir`, creating `LLVM-1.7` directory (from the tarball).
6. in the build subdirectory, it configures with appropriate options to build from the unpacked source tarball into the `build` directory with installation in the `install` directory.
7. runs `make all`
8. runs `make` `check`
9. runs `make install`
10. runs `make uninstall`
11. runs `make dist`
12. runs `make clean`
13. runs `make dist-clean`

If it can pass all that, the distribution will be deemed distribution worth y and you will see:

    ===== LLVM-1.7.tar.gz Ready For Distribution =====

This means the tarball should then be tested on other platforms and have the nightly test run against it. If those all pass, THEN it is ready for distribution.

A note about disk space: using `dist-check` will easily triple the amount of disk space your build tree is using. You might want to check available space before you begin.

dist-clean

In addition to doing a normal `clean`, this target will clean up the files and directories created by the distribution targets. In particular the distribution directory (`LLVM-X.X`), check directory (`_distcheckdir`), and the various tarballs will be removed. You do this after the release has shipped and you no longer need this stuff in your build tree.