-.. _developer_policy:
-
=====================
LLVM Developer Policy
=====================
#. Keep the top of Subversion trees as stable as possible.
-#. Establish awareness of the project's `copyright, license, and patent
- policies`_ with contributors to the project.
+#. Establish awareness of the project's :ref:`copyright, license, and patent
+ policies <copyright-license-patents>` with contributors to the project.
This policy is aimed at frequent contributors to LLVM. People interested in
contributing one-off patches can do so in an informal way by sending them to the
`llvm-commits mailing list
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_ and engaging another
+<http://lists.llvm.org/mailman/listinfo/llvm-commits>`_ and engaging another
developer to see it through the process.
Developer Policies
-------------
Developers should stay informed by reading at least the "dev" mailing list for
-the projects you are interested in, such as `llvmdev
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ for LLVM, `cfe-dev
-<http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev>`_ for Clang, or `lldb-dev
-<http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev>`_ for LLDB. If you are
+the projects you are interested in, such as `llvm-dev
+<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ for LLVM, `cfe-dev
+<http://lists.llvm.org/mailman/listinfo/cfe-dev>`_ for Clang, or `lldb-dev
+<http://lists.llvm.org/mailman/listinfo/lldb-dev>`_ for LLDB. If you are
doing anything more than just casual work on LLVM, it is suggested that you also
subscribe to the "commits" mailing list for the subproject you're interested in,
such as `llvm-commits
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_, `cfe-commits
-<http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits>`_, or `lldb-commits
-<http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits>`_. Reading the
+<http://lists.llvm.org/mailman/listinfo/llvm-commits>`_, `cfe-commits
+<http://lists.llvm.org/mailman/listinfo/cfe-commits>`_, or `lldb-commits
+<http://lists.llvm.org/mailman/listinfo/lldb-commits>`_. Reading the
"commits" list and paying attention to changes being made by others is a good
way to see what other people are interested in and watching the flow of the
project as a whole.
We recommend that active developers register an email account with `LLVM
Bugzilla <http://llvm.org/bugs/>`_ and preferably subscribe to the `llvm-bugs
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs>`_ email list to keep track
+<http://lists.llvm.org/mailman/listinfo/llvm-bugs>`_ email list to keep track
of bugs and enhancements occurring in LLVM. We really appreciate people who are
proactive at catching incoming bugs in their components and dealing with them
promptly.
+Please be aware that all public LLVM mailing lists are public and archived, and
+that notices of confidentiality or non-disclosure cannot be respected.
+
.. _patch:
.. _one-off patches:
-Making a Patch
---------------
+Making and Submitting a Patch
+-----------------------------
When making a patch for review, the goal is to make it as easy for the reviewer
to read it as possible. As such, we recommend that you:
script, please separate out those changes into a separate patch from the rest
of your changes.
+Once your patch is ready, submit it by emailing it to the appropriate project's
+commit mailing list (or commit it directly if applicable). Alternatively, some
+patches get sent to the project's development list or component of the LLVM bug
+tracker, but the commit list is the primary place for reviews and should
+generally be preferred.
+
When sending a patch to a mailing list, it is a good idea to send it as an
*attachment* to the message, not embedded into the text of the message. This
ensures that your mailer will not mangle the patch when it sends it (e.g. by
a file inline, making it difficult to work with for reviewers using that
program.
+When submitting patches, please do not add confidentiality or non-disclosure
+notices to the patches themselves. These notices conflict with the `LLVM
+License`_ and may result in your contribution being excluded.
+
.. _code review:
Code Reviews
#. All developers are required to have significant changes reviewed before they
are committed to the repository.
-#. Code reviews are conducted by email, usually on the llvm-commits list.
+#. Code reviews are conducted by email on the relevant project's commit mailing
+ list, or alternatively on the project's development list or bug tracker.
#. Code can be reviewed either before it is committed or after. We expect major
changes to be reviewed before being committed, but smaller changes (or
all necessary review-related changes.
#. Code review can be an iterative process, which continues until the patch is
- ready to be committed.
+ ready to be committed. Specifically, once a patch is sent out for review, it
+ needs an explicit "looks good" before it is submitted. Do not assume silent
+ approval, or request active objections to the patch with a deadline.
+
+Sometimes code reviews will take longer than you would hope for, especially for
+larger features. Accepted ways to speed up review times for your patches are:
+
+* Review other people's patches. If you help out, everybody will be more
+ willing to do the same for you; goodwill is our currency.
+* Ping the patch. If it is urgent, provide reasons why it is important to you to
+ get this patch landed and ping it every couple of days. If it is
+ not urgent, the common courtesy ping rate is one week. Remember that you're
+ asking for valuable time from other professional developers.
+* Ask for help on IRC. Developers on IRC will be able to either help you
+ directly, or tell you who might be a good reviewer.
+* Split your patch into multiple smaller patches that build on each other. The
+ smaller your patch, the higher the probability that somebody will take a quick
+ look at it.
Developers should participate in code reviews as both reviewers and
reviewees. If someone is kind enough to review your code, you should return the
favor for someone else. Note that anyone is welcome to review and give feedback
on a patch, but only people with Subversion write access can approve it.
+There is a web based code review tool that can optionally be used
+for code reviews. See :doc:`Phabricator`.
+
Code Owners
-----------
responsibility of a code owner is to ensure that a commit to their area of the
code is appropriately reviewed, either by themself or by someone else. The list
of current code owners can be found in the file
-`CODE_OWNERS.TXT <http://llvm.org/viewvc/llvm-project/llvm/trunk/CODE_OWNERS.TXT>`_
+`CODE_OWNERS.TXT <http://llvm.org/viewvc/llvm-project/llvm/trunk/CODE_OWNERS.TXT?view=markup>`_
in the root of the LLVM source tree.
Note that code ownership is completely different than reviewers: anyone can
features added. Some tips for getting your testcase approved:
* All feature and regression test cases are added to the ``llvm/test``
- directory. The appropriate sub-directory should be selected (see the `Testing
- Guide <TestingGuide.html>`_ for details).
+ directory. The appropriate sub-directory should be selected (see the
+ :doc:`Testing Guide <TestingGuide>` for details).
-* Test cases should be written in `LLVM assembly language <LangRef.html>`_
- unless the feature or regression being tested requires another language
- (e.g. the bug being fixed or feature being implemented is in the llvm-gcc C++
- front-end, in which case it must be written in C++).
+* Test cases should be written in :doc:`LLVM assembly language <LangRef>`.
* Test cases, especially for regressions, should be reduced as much as possible,
- by `bugpoint <Bugpoint.html>`_ or manually. It is unacceptable to place an
+ by :doc:`bugpoint <Bugpoint>` or manually. It is unacceptable to place an
entire failing program into ``llvm/test`` as this creates a *time-to-test*
burden on all developers. Please keep them short.
progress. The developer is welcome to re-commit the change after the problem has
been fixed.
+.. _commit messages:
+
+Commit messages
+---------------
+
+Although we don't enforce the format of commit messages, we prefer that
+you follow these guidelines to help review, search in logs, email formatting
+and so on. These guidelines are very similar to rules used by other open source
+projects.
+
+Most importantly, the contents of the message should be carefully written to
+convey the rationale of the change (without delving too much in detail). It
+also should avoid being vague or overly specific. For example, "bits were not
+set right" will leave the reviewer wondering about which bits, and why they
+weren't right, while "Correctly set overflow bits in TargetInfo" conveys almost
+all there is to the change.
+
+Below are some guidelines about the format of the message itself:
+
+* Separate the commit message into title, body and, if you're not the original
+ author, a "Patch by" attribution line (see below).
+
+* The title should be concise. Because all commits are emailed to the list with
+ the first line as the subject, long titles are frowned upon. Short titles
+ also look better in `git log`.
+
+* When the changes are restricted to a specific part of the code (e.g. a
+ back-end or optimization pass), it is customary to add a tag to the
+ beginning of the line in square brackets. For example, "[SCEV] ..."
+ or "[OpenMP] ...". This helps email filters and searches for post-commit
+ reviews.
+
+* The body, if it exists, should be separated from the title by an empty line.
+
+* The body should be concise, but explanatory, including a complete
+ reasoning. Unless it is required to understand the change, examples,
+ code snippets and gory details should be left to bug comments, web
+ review or the mailing list.
+
+* If the patch fixes a bug in bugzilla, please include the PR# in the message.
+
+* `Attribution of Changes`_ should be in a separate line, after the end of
+ the body, as simple as "Patch by John Doe.". This is how we officially
+ handle attribution, and there are automated processes that rely on this
+ format.
+
+* Text formatting and spelling should follow the same rules as documentation
+ and in-code comments, ex. capitalization, full stop, etc.
+
+* If the commit is a bug fix on top of another recently committed patch, or a
+ revert or reapply of a patch, include the svn revision number of the prior
+ related commit. This could be as simple as "Revert rNNNN because it caused
+ PR#".
+
+For minor violations of these recommendations, the community normally favors
+reminding the contributor of this policy over reverting. Minor corrections and
+omissions can be handled by sending a reply to the commits mailing list.
+
Obtaining Commit Access
-----------------------
from, e.g. "J. Random Hacker <hacker@yoyodyne.com>".
#. A "password hash" of the password you want to use, e.g. "``2ACR96qjUqsyM``".
- Note that you don't ever tell us what your password is, you just give it to
+ Note that you don't ever tell us what your password is; you just give it to
us in an encrypted form. To get this, run "``htpasswd``" (a utility that
comes with apache) in crypt mode (often enabled with "``-d``"), or find a web
page that will do it for you.
tree with an SVN URL of "https://username@llvm.org/..." instead of the normal
anonymous URL of "http://llvm.org/...". The first time you commit you'll have
to type in your password. Note that you may get a warning from SVN about an
-untrusted key, you can ignore this. To verify that your commit access works,
+untrusted key; you can ignore this. To verify that your commit access works,
please do a test commit (e.g. change a comment or add a blank line). Your first
commit to a repository may require the autogenerated email to be approved by a
-mailing list. This is normal, and will be done when the mailing list owner has
+mailing list. This is normal and will be done when the mailing list owner has
time.
If you have recently been granted commit access, these policies apply:
#. You are granted *commit-after-approval* to all parts of LLVM. To get
approval, submit a `patch`_ to `llvm-commits
- <http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_. When approved
- you may commit it yourself.</li>
+ <http://lists.llvm.org/mailman/listinfo/llvm-commits>`_. When approved,
+ you may commit it yourself.
#. You are allowed to commit patches without approval which you think are
obvious. This is clearly a subjective decision --- we simply expect you to
#. You are allowed to commit patches without approval to those portions of LLVM
that you have contributed or maintain (i.e., have been assigned
responsibility for), with the proviso that such commits must not break the
- build. This is a "trust but verify" policy and commits of this nature are
+ build. This is a "trust but verify" policy, and commits of this nature are
reviewed after they are committed.
#. Multiple violations of these policies or a single egregious violation may
In any case, your changes are still subject to `code review`_ (either before or
after they are committed, depending on the nature of the change). You are
encouraged to review other peoples' patches as well, but you aren't required
-to.
+to do so.
.. _discuss the change/gather consensus:
---------------------
When a developer begins a major new project with the aim of contributing it back
-to LLVM, s/he should inform the community with an email to the `llvmdev
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ email list, to the extent
+to LLVM, they should inform the community with an email to the `llvm-dev
+<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ email list, to the extent
possible. The reason for this is to:
#. keep the community informed about future changes to LLVM,
Attribution of Changes
----------------------
-We believe in correct attribution of contributions to their contributors.
-However, we do not want the source code to be littered with random attributions
-"this code written by J. Random Hacker" (this is noisy and distracting). In
-practice, the revision control system keeps a perfect history of who changed
-what, and the CREDITS.txt file describes higher-level contributions. If you
-commit a patch for someone else, please say "patch contributed by J. Random
-Hacker!" in the commit message.
+When contributors submit a patch to an LLVM project, other developers with
+commit access may commit it for the author once appropriate (based on the
+progression of code review, etc.). When doing so, it is important to retain
+correct attribution of contributions to their contributors. However, we do not
+want the source code to be littered with random attributions "this code written
+by J. Random Hacker" (this is noisy and distracting). In practice, the revision
+control system keeps a perfect history of who changed what, and the CREDITS.txt
+file describes higher-level contributions. If you commit a patch for someone
+else, please follow the attribution of changes in the simple manner as outlined
+by the `commit messages`_ section. Overall, please do not add contributor names
+to the source code.
+
+Also, don't commit patches authored by others unless they have submitted the
+patch to the project or you have been authorized to submit them on their behalf
+(you work together and your company authorized you to contribute the patches,
+etc.). The author should first submit them to the relevant project's commit
+list, development list, or LLVM bug tracker component. If someone sends you
+a patch privately, encourage them to submit it to the appropriate list first.
+
+
+IR Backwards Compatibility
+--------------------------
+
+When the IR format has to be changed, keep in mind that we try to maintain some
+backwards compatibility. The rules are intended as a balance between convenience
+for llvm users and not imposing a big burden on llvm developers:
+
+* The textual format is not backwards compatible. We don't change it too often,
+ but there are no specific promises.
+
+* Additions and changes to the IR should be reflected in
+ ``test/Bitcode/compatibility.ll``.
+
+* The bitcode format produced by a X.Y release will be readable by all
+ following X.Z releases and the (X+1).0 release.
+
+* After each X.Y release, ``compatibility.ll`` must be copied to
+ ``compatibility-X.Y.ll``. The corresponding bitcode file should be assembled
+ using the X.Y build and committed as ``compatibility-X.Y.ll.bc``.
+
+* Newer releases can ignore features from older releases, but they cannot
+ miscompile them. For example, if nsw is ever replaced with something else,
+ dropping it would be a valid way to upgrade the IR.
+
+* Debug metadata is special in that it is currently dropped during upgrades.
+
+* Non-debug metadata is defined to be safe to drop, so a valid way to upgrade
+ it is to drop it. That is not very user friendly and a bit more effort is
+ expected, but no promises are made.
+
+C API Changes
+----------------
+
+* Stability Guarantees: The C API is, in general, a "best effort" for stability.
+ This means that we make every attempt to keep the C API stable, but that
+ stability will be limited by the abstractness of the interface and the
+ stability of the C++ API that it wraps. In practice, this means that things
+ like "create debug info" or "create this type of instruction" are likely to be
+ less stable than "take this IR file and JIT it for my current machine".
+
+* Release stability: We won't break the C API on the release branch with patches
+ that go on that branch, with the exception that we will fix an unintentional
+ C API break that will keep the release consistent with both the previous and
+ next release.
+
+* Testing: Patches to the C API are expected to come with tests just like any
+ other patch.
+
+* Including new things into the API: If an LLVM subcomponent has a C API already
+ included, then expanding that C API is acceptable. Adding C API for
+ subcomponents that don't currently have one needs to be discussed on the
+ mailing list for design and maintainability feedback prior to implementation.
-Overall, please do not add contributor names to the source code.
+* Documentation: Any changes to the C API are required to be documented in the
+ release notes so that it's clear to external users who do not follow the
+ project how the C API is changing and evolving.
-.. _copyright, license, and patent policies:
+.. _copyright-license-patents:
Copyright, License, and Patents
===============================
cannot be moved from the LLVM core to libc++ without the copyright owner's
permission.
-Note that the LLVM Project does distribute llvm-gcc and dragonegg, **which are
-GPL.** This means that anything "linked" into llvm-gcc must itself be compatible
+Note that the LLVM Project does distribute dragonegg, **which is
+GPL.** This means that anything "linked" into dragonegg must itself be compatible
with the GPL, and must be releasable under the terms of the GPL. This implies
-that **any code linked into llvm-gcc and distributed to others may be subject to
+that **any code linked into dragonegg and distributed to others may be subject to
the viral aspects of the GPL** (for example, a proprietary code generator linked
-into llvm-gcc must be made available under the GPL). This is not a problem for
+into dragonegg must be made available under the GPL). This is not a problem for
code already distributed under a more liberal license (like the UIUC license),
and GPL-containing subprojects are kept in separate SVN repositories whose
LICENSE.txt files specifically indicate that they contain GPL code.
We have no plans to change the license of LLVM. If you have questions or
comments about the license, please contact the `LLVM Developer's Mailing
-List <mailto:llvmdev@cs.uiuc.edu>`_.
+List <mailto:llvm-dev@lists.llvm.org>`_.
Patents
-------
you or your employer own the rights to a patent and would like to contribute
code to LLVM that relies on it, we require that the copyright owner sign an
agreement that allows any other user of LLVM to freely use your patent. Please
-contact the `oversight group <mailto:llvm-oversight@cs.uiuc.edu>`_ for more
+contact the `LLVM Foundation Board of Directors <mailto:board@llvm.org>`_ for more
details.
projects / oota-llvm.git / blobdiff