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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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<head>
<title>LLVM Developer Policy</title>
<link rel="stylesheet" href="llvm.css" type="text/css">
</head>
<body>
<div class="doc_warning">DRAFT Only. DRAFT Only. DRAFT Only. DRAFT Only.</div>
<div class="doc_title">LLVM Developer Policy</div>
<table class="layout"><tr class="layout"><td class="layout">
<h2>Contents</h2>
<ol>
<li><a href="#introduction">Introduction</a></li>
<li><a href="#general">General Policies</a>
<ol>
<li><a href="#informed">Stay Informed</a> </li>
<li><a href="#newwork">Starting New Work</a></li>
<li><a href="#reviews">Code Reviews</a></li>
<li><a href="#incremental">Incremental Development</a></li>
<li><a href="#quality">Quality</a></li>
<li><a href="#testcases">Test Cases</a></li>
</ol></li>
<li><a href="#patches">Patch Policies</a>
<ol>
<li><a href="#p_form">Patch Form</a></li>
<li><a href="#p_testing">Patch Testing</a></li>
<li><a href="#p_submission">Patch Submission</a></li>
<li><a href="#p_aftersub">After Submission</a></li>
<li><a href="#p_aftercommit">After Commit</a></li>
<li><a href="#c_access">Obtaining Commit Access</a></li>
<li><a href="#c_new">New Committers</a></li>
</ol></li>
<li><a href="#candl">Copyright and License</a>
<ol>
<li><a href="#attribution">Attribution</a></li>
<li><a href="#copyright">Copyright</a></li>
<li><a href="#license">License</a></li>
<li><a href="#devagree">Developer Agreements</a></li>
</ol></li>
<li><a href="#terms">Terminology</a></li>
<li><a href="#polnotes">Policy Notes</a></li>
</ol>
<div class="doc_author">Written by LLVM Oversight Team</div>
</td><td class="layout">
<!--=========================================================================-->
<div class="doc_section"><a name="introduction">Introduction</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>This document contains the LLVM Developer Policy which defines the
project's policy towards developers and their contributions. The intent of
this policy is to eliminate mis-communication, rework, and confusion that
might arise from the distributed nature of LLVM's development. By stating
the policy in clear terms, we hope each developer can know ahead of time
what to expect when making LLVM contributions.</p>
<p>This policy is also designed to accomplish the following objectives:</p>
<ol>
<li>Attract both users and developers to the LLVM project.</li>
<li>Make life as simple and easy for contributors as possible.</li>
<li>Indicate that LLVM is a mature project with a thriving community and
sensible policies directing its ongoing development.</li>
</ol>
</div>
<!--=========================================================================-->
<div class="doc_section"><a name="general">General Policies</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>This section contains policies that pertain generally to LLVM developers.
LLVM Developers are expected to meet the following obligations in order
for LLVM to maintain a high standard of quality.<p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="informed">Stay Informed</a> </div>
<div class="doc_text">
<p>Developers should stay informed by reading at least the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
email list. If you are doing anything more than just casual work on LLVM,
it is suggested that you also subscribe to the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
list and pay attention to changes being made by others.</p>
<p>We recommend that active developers register an email account with
<a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
email list to keep track of bugs and enhancements occurring in LLVM.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="newwork">Starting New Work</a></div>
<div class="doc_text">
<p>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 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvm-dev</a>
email list, to the extent possible. The reason for this is to:
<ul>
<li>keep the community informed about future changes to LLVM, </li>
<li>avoid duplication of effort by having multiple parties working on the
same thing and not knowing about it, and</li>
<li>ensure that any technical issues around the proposed work are
discussed and resolved before any significant work is done.</li>
</ul>
<p>The design of LLVM is carefully controlled to ensure that all the pieces
fit together well. If you plan to make a major change to the way LLVM works or
a major new extension, it is a good idea to get consensus with the development
community before you start working on it.</p>
</div>
</td></tr></table>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
<div class="doc_text">
<p>LLVM has a code review policy. Code review is an excellent way to ensure
high quality in the software. The following policies apply:</p>
<ol>
<li>All developers are required to have significant changes reviewed
before they are committed to the repository.</li>
<li>Code reviews are conducted by email.</li>
<li>Code can be reviewed either before it is committed or after.</li>
<li>The developer responsible for a code change is also responsible for
making all necessary review changes.</li>
<li>Developers should participate in code reviews as both a reviewer and
a reviewee. We don't have a dedicated team of reviewers. If someone is
kind enough to review your code, you should return the favor for someone
else.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
</div>
<div class="doc_text">
<p>LLVM uses an incremental development style and all developers are expected
to follow this practice. Incremental development is a big key to LLVM's
success and it is essential that developers submit incremental patches. The
following defines the incremental development approach:</p>
<ol>
<li>The first task is to define the increment and get consensus (with the
LLVM development community) on what the end goal of the change is. Making
random small changes that go nowhere is not useful for anyone.</li>
<li>An increment is the smallest patch size necessary to effect one change
in LLVM.</li>
<li>Increments can be stand alone (e.g. to fix a bug), or part of a planned
series of increments towards some development goal.</li>
<li>Increments should be kept as small as possible. This simplifies your
work (into a logical progression), simplifies code review and reduces the
chance that you will get negative feedback on the change. Small increments
also facilitate the maintenance of a high quality code base.</li>
<li>Larger increments require a larger testing effort.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="quality">Quality</a></div>
<div class="doc_text">
<p>The minimum quality standards for any change to the main development
branch are:</p>
<ol>
<li>Code must adhere to the
<a href="CodingStandards.html">LLVM Coding Standards</a>.</li>
<li>Code must compile cleanly (no errors, no warnings) on at least one
platform.</li>
<li>Code must pass the deja gnu (llvm/test) test suite.</li>
</ol>
<p>Additionally, the committer is responsible for addressing all of the
following items (preferably before submission):</p>
<ol>
<li>The code should compile cleanly on all platforms.</li>
<li>The changes should not cause regressions in the <tt>llvm-test</tt>
suite including SPEC CINT2000, SPEC CFP2000, SPEC CINT2006, and
SPEC CFP2006.</li>
<li>The change set should not cause performance or correctness regressions
for the LLVM tools.</li>
<li>The changes should not cause performance or correctness regressions in
code compiled by LLVM on all applicable targets.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
<div class="doc_text">
<p>Developers are required to create test cases for regressions and new
features and include them with their changes. The following policies
apply:</p>
<ol>
<li>All feature and regression test cases must be added to the
<tt>llvm/test</tt> directory. The appropriate sub-directory should be
selected (see the <a href="TestingGuide.html">Testing Guide</a> for
details).</li>
<li>Test cases should be written in
<a href="LangRef.html">LLVM assembly language</a> unless the
feature or regression being tested requires another language (e.g. the
bug being fixed or feature being implemented is in the lvm-gcc C++
front-end).</li>
<li>Test cases, especially for regressions, should be reduced as much as
possible, by <a href="CommandGuide/html/bugpoint.html">bugpoint</a> or
manually. It is unacceptable
to place an entire failing program into <tt>llvm/test</tt> as this creates
a <i>time-to-test</i> burden on all developers. Please keep them short.</li>
<li>More extensive test cases (applications, benchmarks, etc.) should be
added to the <tt>llvm-test</tt> test suite. This test suite is for
coverage not features or regressions.</li>
</ol>
</div>
<!--=========================================================================-->
<div class="doc_section"><a name="patches">Patch Policies</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>This section contains policies that pertain to submitting patches
to LLVM and committing code to the repository</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="p_form">Patch Form</a></div>
<div class="doc_text">
<p>When submitting a patch, developers must follow these rules:</p>
<ol>
<li>Patches must be made against the CVS HEAD (main development trunk),
not a branch.</li>
<li>Patches should be made with this command:<pre>
cvs diff -Ntdup -5</pre> or with the utility <tt>utils/mkpatch</tt>.</li>
<li>Patches should not include differences in generated code such as the
code generated by <tt>flex</tt>, <tt>bison</tt> or <tt>tblgen</tt>. The
<tt>utils/mkpatch</tt> utility takes care of this for you.</li>
<li>Patches must not include any patent violations. To the best of our
knowledge, LLVM is free of any existing patent violations and it is our
intent to keep it that way. </li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="p_testing">Patch Testing</a></div>
<div class="doc_text">
<p>Before a patch is submitted for review, it should be tested to ensure
that:</p>
<ol>
<li>The patch must compile against the CVS HEAD cleanly (zero warnings, zero
errors).</li>
<li>All the llvm/test (Deja Gnu) tests must pass.</li>
<li>The patch should cause no regressions in the llvm-test test suite. How
much testing is appropriate depends on the nature of the patch. We leave it
to your good judgement, but you will be responsible for fixing any
regressions or reverting the patch.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="p_submission">Patch Submission</a></div>
<div class="doc_text">
<p>When a patch is ready to be submitted, these policies apply:</p>
<ol>
<li>Patches should be submitted immediately after they are generated. Stale
patches may not apply correctly if the underlying code changes between the
time the patch was created and the time it is applied.</li>
<li>Patches should be submitted by e-mail to the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
llvm-commits</a> list.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="p_aftersub">After Submission</a></div>
<div class="doc_text">
<p>After a patch has been submitted, these policies apply:</p>
<ol>
<li>The patch is subject to review by anyone on the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
email list.</li>
<li>Changes recommended by a reviewer should be incorporated into your
patch or you should explain why the reviewer is incorrect.
<li>Changes to the patch must be re-submitted to the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
email list.</li>
<li>This process iterates until all review issues have been addressed.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="p_aftercommit">After Commit</a></div>
<div class="doc_text">
<p>After a patch has been committed, these policies apply:</p>
<ol>
<li>The patch is subject to further review by anyone on the llvm-commits
email list.</li>
<li>The patch submitter is responsible for all aspects of the patch per
the <a href="quality">quality policy</a> above.</li>
<li>If the patch is discovered to not meet the
<a href="quality">quality policy</a> standards within a reasonable time
frame (24 hours), it may be subject to reversal.</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="c_access">Obtaining Commit Access</a></div>
<div class="doc_text">
<p>Commit access to the repository is granted according to this policy:</p>
<ol>
<li>Commit access is not granted to anyone unless they specifically ask for
it.</li>
<li>Requests for commit access must be sent to the
<a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</li>
<li>Granting commit access is at the sole discretion of the LLVM Oversight
Group.</li>
</ol>
<p>Submitting patches to LLVM via the patch policy above will greatly
increase the chance that your request for commit access is granted. Getting
to know the members of the LLVM community (email, IRC, in person contact,
etc.) will also increase your chances.</p>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="c_new">New Committers</a></div>
<div class="doc_text">
<p>For those who have recently obtained commit access, the following policies
apply:</p>
<ol>
<li>You are granted <i>commit-after-approval</i> to all parts of LLVM.
To get approval, submit a patch to
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
per the <a href="#patches">patch policies</a> above. When approved you
may commit it yourself.</li>
<li>You are allowed to commit patches without approval which you think are
obvious. This is clearly a subjective decision. We simply expect you to
use good judgement.</li>
<li>You are allowed to commit patches without approval to those portions
of LLVM that you own (contributed) or maintain (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
reviewed after they are committed.</li>
<li>Commits that violate the <a href="quality">quality standards</a> may
be reverted. This is necessary when the change blocks other developers from
making progress. The developer is welcome to re-commit the change after
the problem has been fixed.</li>
<li>Multiple violations of these policies or a single egregious violation
may cause commit access to be revoked.</li>
</ol>
</div>
<!--=========================================================================-->
<div class="doc_section"><a name="candl">Copyright and License</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>We address here the issues of copyright and license for the LLVM project.
The object of the copyright and license is the LLVM source code and
documentation.
Currently, the University of Illinois is the LLVM copyright holder and the
terms of its license to LLVM users and developers is the
<a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
Illinois/NCSA Open Source License</a>.
</div>
<div class="doc_notes">
<p>NOTE: This section deals with legal matters but does not provide legal
advice. It is intended only as a general guideline.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"><a name="attribution">Attribution</a></div>
<div class="doc_text">
<p>The LLVM project believes in correct attribution of contributions to
their contributors, as follows:</p>
<ol>
<li>Developers who originate new files in LLVM should place their name at
the top of the file per the
<a href="CodingStandards.html">Coding Standards</a>.</li>
<li>There should be only one name at the top of the file and it should be
the person who created the file.</li>
<li>Placing your name in the file does not imply copyright but does
correctly attribute the file to its author.</li>
<li>Developers should be aware that after some time has passed, the name at
the top of a file may become meaningless as maintenance/ownership of files
changes.</li>
<li>Developers should submit or commit patches to the
<a href="http://llvm.org/cvsweb/cvsweb.cgi/llvm/CREDITS.TXT?rev=1.67&content-type=text/x-cvsweb-markup">CREDITS.txt</a>
file to summarize their contributions.</li>
<li>Commit comments should contain correct attribution of the person who
submitted the patch if that person is not the committer (i.e. when a
developer with commit privileges commits a patch for someone else).</li>
</ol>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"><a name="copyright">Copyright</a></div>
<div class="doc_text">
<p>
<p>For consistency and ease of management, the project requires the
copyright for all LLVM software to be held by a single copyright holder.
Although UIUC may assign the copyright of the software to another entity,
the intent for the project is to always have a single entity hold the copy
rights to LLVM at any given time.
<p>Having multiple copyright holders for various portions of LLVM is
problematic in the management of the software. Having a single copyright
holder is in the best interests of all developers and users as it greatly
reduces the managerial burden for any kind of administrative or technical
decisions about LLVM.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"><a name="license">License</a></div>
<div class="doc_text">
<p>LLVM licensing decisions will be made by the LLVM Oversight Group. Any
issues, comments or suggestions with the licensing should be sent to the
<a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
<p>The LLVM Oversight Group intends to keep LLVM perpetually open source
and to use liberal open source licenses. The current license is the
<a href="http://www.opensource.org/licenses/UoI-NCSA.php">
University of Illinois/NCSA Open Source License</a>, which boils
down to this:</p>
<ul>
<li>You can freely distribute LLVM.</li>
<li>You must retain the copyright notice if you redistribute LLVM.</li>
<li>Binaries derived from LLVM must reproduce the copyright notice.</li>
<li>You can't use our names to promote your LLVM derived products.</li>
<li>There's no warranty on LLVM at all.</li>
</ul>
<p>We believe this fosters the widest adoption of LLVM because it allows
commercial products to be derived from LLVM with few restrictions and
without a requirement for making any derived works also open source (i.e.
LLVM' license is not a <i>copyleft</i> license). We suggest that you read the
<a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a> if
further clarification is needed.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
<div class="doc_text">
<p>With regards to the LLVM copyright and licensing, developers agree to:</p>
<ul>
<li>assign their copy rights to UIUC for any contribution made so that
the entire software base can be managed by a single copyright holder.</li>
<li>allow their contribution(s) to be licensed as open source by the then
current license chosen by the LLVM Oversight Group.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_section"><a name="terms">Terminology</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>So that the policies defined in this document are clear, we define some
terms here.</p>
<dl>
<dt><a name="t_change">Change</a></dt>
<dd>Any modification to LLVM including documentation, tests, build system,
etc. either in <a href="#t_patch">patch</a> or
<a href="#t_commit">commit</a> form.</dd>
<dt><a name="t_commit">Commit</a><dt>
<dd>A <a href="t_change">change</a> submitted directly to LLVM software
repository via the <tt>cvs commit</tt> command.</dd>
<dt><a name="t_copleft">Copyleft</a></dt>
<dd>A licensing policy that requires the licensee to adopt the terms of the
license for <i>derived</i> works. LLVM does not subscribe to this
policy.</dd>
<dt><a name="t_developer">Developer</a></dt>
<dd>Anyone who submits a <a href="#t_change">change</a> to LLVM.</dd>
<dt><a name="t_inrement">Increment</a></dt>
<dd>A <a href="#t_change">change</a> or set of changes, whether by
<a href="#t_patch">patch</a> or <a href="#t_commit">commit</a>, that are
related by a single common purpose. Increments are atomic as they
leave LLVM in a stable state (both compiling and working properly).</dd>
<dt><a name="t_must">Must</a></dt>
<dd>When used in a policy statement, the term <i>must</i> implies a
non-optional requirement on the developer.</dd>
<dt><a name="t_patch">Patch</a></dt>
<dd>A <a href="#t_change">change</a> submitted by email in patch (diff)
format generated by the <tt>cvs diff</tt> command.</dd>
<dt><a name="t_should">Should</a></dt>
<dd>When used in a policy statement, the term <i>should</i> implies a
recommended but optional requirement on the developer.</dd>
</dl>
</div>
<!--=========================================================================-->
<div class="doc_section"><a name="polnotes">Policy Notes</a></div>
<!--=========================================================================-->
<div class="doc_text">
<p>This section contains some notes on policy topics that need to be
resolved and incorporated into the main body of the document above.</p>
<ol>
<li>When to open a new bug and when to re-use an existing one. For example
PR1158. If the same assertion happens do you open a new bug or reopen
1158?</li>
</ol>
</div>
<!-- *********************************************************************** -->
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