How To Release LLVM To The Public

NOTE: THIS DOCUMENT IS A WORK IN PROGRESS!

1. Introduction
2. Release Process
3. Distribution Targets

Written by Reid Spencer, John Criswell

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. Mostly, it's just a bunch of reminders of things to do at release time so we don't inadvertently ship something that is utility deficient.

There are three main tasks for building a release of LLVM:

1. Create the LLVM source distribution.
2. Create the LLVM GCC source distribtuion.
3. Create a set of LLVM GCC binary distribtuions for each supported platform. These binary distributions must include compiled versions of the libraries found in `llvm/runtime` from the LLVM source distribution created in Step 1.

Release Process
Process Overview

1. Update Documentation
2. Merge Branches
3. Make LibDeps.txt
4. Settle LLVM HEAD
5. Tag LLVM and Create the Release Branch
6. Build LLVM
7. Run 'make check'
8. Run LLVM Test Suite
9. Build the LLVM Source Distributions
10. Build the LLVM GCC Binary Distribution

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 CVS and changes in basic system requirements.

Merge Branches

Merge any work done on branches intended for release into mainline. Finish and commit all new features or bug fixes that are scheduled to go into the release. Work that is not to be incorporated into the release should not be merged from branchs or commited from developer's working directories.

From this point until the release branch is created, developers should not commit changes to the llvm and llvm-gcc CVS repositories unless it is a bug fix for the release.

Make LibDeps.txt

Rebuild the `LibDeps.txt` target in `utils/llvm-config`. This makes sure that the `llvm-config` utility remains relevant for the release, reflecting any changes in the library dependencies.

Settle CVS HEAD

Use the nightly test reports and 'make check' (deja-gnu based tests) to ensure that recent changes and merged branches have not destabilized LLVM. Platforms which are used less often should be given special attention as they are the most likely to break from commits from the previous step.

CVS Tag And Branch

Tag and branch the CVS HEAD using the following procedure:

1. Request all developers to refrain from committing. Offenders get commit rights taken away (temporarily).
2. The Release Manager updates his/her llvm, llvm-test, and llvm-gcc source trees with the latest sources from mainline CVS. The Release Manage may want to consider using a new working directory for this to keep current uncommitted work separate from release work.
3. The Release Manager tags his/her llvm, llvm-test, and llvm-gcc working directories with "ROOT_RELEASE_XX" where XX is the major and minor release numbers (you can't have . in a cvs tag name). So, for Release 1.2, XX=12 and for Release 1.10, XX=110.
4. Immediately create cvs branches based on the ROOT_RELEASE_XX tag. The tag should be "release_XX" (where XX matches that used for the ROOT_RELEASE_XX tag). This is where the release distribution will be created.
5. Advise developers they can work on CVS HEAD again.
6. The Release Manager and any developers working on the release 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:

   `cvs -d <CVS Repository> co -r release_XX llvm`
   `cvs -d <CVS Repository> co -r release_XX llvm-test`
   `cvs -d <CVS Repository> co -r release_XX llvm-gcc`

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.

Build a new version of the LLVM GCC front-end after building the LLVM tools. Once that is complete, go back to the LLVM source tree and build and install the `llvm/runtime` libraries.

Run 'make check'

Run `make check` and ensure there are no unexpected failures. If there are, resolve the failures, commit them back into the release branch, and restart testing by re-building LLVM.

Ensure that 'make check' passes on all platforms for all targets. If certain failures cannot be resolved before release time, determine if marking them XFAIL is appropriate. If not, fix the bug and go back. The test suite must complete with "0 unexpected failures" for release.

LLVM Test Suite

Run the llvm-test suite and ensure there are no unacceptable failures. If there are, resolve the failures and go back to re-building LLVM. The test suite should be run in Nightly Test mode. All tests must pass.

Build the LLVM Source Distributions

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

`cvs -d <CVS Repository> export -r release_XX llvm`
`cvs -d <CVS Repository> export -r release_XX llvm-test`
`cvs -d <CVS Repository> export -r release_XX llvm-gcc`
`mkdir cfrontend; mv llvm-gcc cfrontend/src`
`tar -cvf - llvm | gzip > llvm-X.X.tar.gz`
`tar -cvf - llvm-test | gzip > llvm-test-X.X.tar.gz`
`tar -cvf - cfrontend/src | gzip > cfrontend-X.X.source.tar.gz`

Build the LLVM GCC Binary Distribution

Creating the LLVM GCC binary distribution requires performing the following steps for each supported platform:

1. Build the LLVM GCC front-end. The LLVM GCC front-end must be installed in a directory named `cfrontend/<platform>/llvm-gcc`. For example, the Sparc/Solaris directory is named `cfrontend/sparc/llvm-gcc`.
2. Build the libraries in `llvm/runtime` and install them into the created LLVM GCC installation directory.
3. For systems with non-distributable header files (e.g. Solaris), manually remove header files that the GCC build process has "fixed." This process is admittedly painful, but not as bad as it looks; these header files are almost always easily identifiable with simple grep expressions and are installed in only a few directories in the GCC installation directory.
4. Add the copyright files and header file fix script.
5. Archive and compress the installation directory. These can be found in previous releases of the LLVM-GCC front-end.

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, CVS 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 its 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

## 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.