<div class="doc_title">LLVM Developer Policy</div>
<ol>
<li><a href="#introduction">Introduction</a></li>
- <li><a href="#general">General Policies</a>
+ <li><a href="#policies">Developer Policies</a>
<ol>
- <li><a href="#informed">Stay Informed</a> </li>
+ <li><a href="#informed">Stay Informed</a></li>
+ <li><a href="#patches">Making a Patch</a></li>
<li><a href="#reviews">Code Reviews</a></li>
- <li><a href="#quality">Quality</a></li>
<li><a href="#testcases">Test Cases</a></li>
- <li><a href="#c_new">Obtaining Commit Access</a></li>
- <li><a href="#newwork">Making a Major Change</a>
- <ol>
- <li><a href="#incremental">Incremental Development</a></li>
- </ol></li>
+ <li><a href="#quality">Quality</a></li>
+ <li><a href="#commitaccess">Obtaining Commit Access</a></li>
+ <li><a href="#newwork">Making a Major Change</a></li>
+ <li><a href="#incremental">Incremental Development</a></li>
<li><a href="#attribution">Attribution of Changes</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_submission">Patch Submission</a></li>
- <li><a href="#p_aftersub">After Submission</a></li>
- <li><a href="#p_aftercommit">After Commit</a></li>
- </ol></li>
- <li><a href="#candl">Copyright and License</a>
+ <li><a href="#clp">Copyright, License, and Patents</a>
<ol>
<li><a href="#copyright">Copyright</a></li>
<li><a href="#license">License</a></li>
+ <li><a href="#patents">Patents</a></li>
<li><a href="#devagree">Developer Agreements</a></li>
</ol></li>
</ol>
-<div class="doc_author">Written by LLVM Oversight Team</div>
+<div class="doc_author">Written by the LLVM Oversight Team</div>
<!--=========================================================================-->
<div class="doc_section"><a name="introduction">Introduction</a></div>
<li>Keep the top of tree CVS/SVN trees as stable as possible.</li>
</ol>
- <p>This policy is aimed at regular contributors to LLVM. People interested in
+ <p>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 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
llvm-commits mailing list</a> and engaging another developer to see it through
</div>
<!--=========================================================================-->
-<div class="doc_section"><a name="general">General Policies</a></div>
+<div class="doc_section"><a name="policies">Developer Policies</a></div>
<!--=========================================================================-->
<div class="doc_text">
- <p>This section contains policies that pertain generally to regular LLVM
- developers. We always welcome <a href="#patches">random patches</a> from
- people who do not routinely contribute to LLVM, but expect more from regular
- contributors to keep the system as efficient as possible for everyone.
- Regular LLVM developers are expected to meet the following obligations in
+ <p>This section contains policies that pertain to frequent LLVM
+ developers. We always welcome <a href="#patches">one-off patches</a> from
+ people who do not routinely contribute to LLVM, but we expect more from
+ frequent contributors to keep the system as efficient as possible for
+ everyone.
+ Frequent LLVM contributors are expected to meet the following requirements in
order for LLVM to maintain a high standard of quality.<p>
</div>
email list to keep track of bugs and enhancements occurring in LLVM.</p>
</div>
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"> <a name="patches">Making a Patch</a></div>
+
+<div class="doc_text">
+
+<p>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:</p>
+ <ol>
+ <li>Make your patch against the CVS HEAD (main development trunk),
+ not a branch, and not an old version of LLVM. This makes it easy to
+ apply the patch.</li>
+
+ <li>Similarly, patches should be submitted soon after they are generated.
+ Old 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 made with this command:
+ <pre>cvs diff -Ntdup -5</pre>
+ or with the utility <tt>utils/mkpatch</tt>, which makes it easy to read the
+ diff.</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>
+
+ </ol>
+
+ <p>When sending a patch to a mailing list, it is a good idea to send it as an
+ <em>attachment</em> 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 making whitespace changes or by wrapping lines).</p>
+</div>
+
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
<div class="doc_text">
changes (or changes where the developer owns the component) can be
reviewed after commit.</li>
<li>The developer responsible for a code change is also responsible for
- making all necessary review-related 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>
+ making all necessary review-related changes.</li>
+ <li>Code review can be an iterative process, which continues until the patch
+ is ready to be committed.</li>
</ol>
+
+ <p>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 CVS write access can
+ approve it.</p>
+
</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 any bugs fixed and any new
- features added. The following policies apply:</p>
+ features added. Some tips for getting your testcase approved:</p>
<ol>
- <li>All feature and regression test cases must be added to the
+ <li>All feature and regression test cases are 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>
<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 llvm-gcc C++
- front-end).</li>
+ front-end, in which case it must be written in C++).</li>
<li>Test cases, especially for regressions, should be reduced as much as
- possible, by <a href="CommandGuide/html/bugpoint.html">bugpoint</a> or
+ possible, by <a href="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>
+
+ <p>Note that llvm/test is designed for regression and small feature tests
+ only. More extensive test cases (e.g., entire applications, benchmarks,
+ etc) should be added to the <tt>llvm-test</tt> test suite. The llvm-test
+ suite is for coverage (correctness, performance, etc) testing, not feature
+ or regression testing.</p>
</div>
<!-- _______________________________________________________________________ -->
<li>Bug fixes and new features should <a href="#testcases">include a
testcase</a> so we know if the fix/feature ever regresses in the
future.</li>
- <li>Code must pass the dejagnu (llvm/test) test suite.</li>
+ <li>Code must pass the dejagnu (<tt>llvm/test</tt>) test suite.</li>
<li>The code must not cause regressions on a reasonable subset of llvm-test,
where "reasonable" depends on the contributor's judgement and the scope
of the change (more invasive changes require more testing). A reasonable
<p>Additionally, the committer is responsible for addressing any problems
found in the future that the change is responsible for. For example:</p>
<ul>
- <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 code should compile cleanly on all supported platforms.</li>
+ <li>The changes should not cause any correctness regressions in the
+ <tt>llvm-test</tt> suite and must not cause any major performance
+ regressions.</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
bugs</a> that result from your change.</li>
</ul>
- <p>We prefer for this to be handled before submission but understand that it's
- not possible to test all of this for every submission. Our nightly testing
+ <p>We prefer for this to be handled before submission but understand that it
+ isn't possible to test all of this for every submission. Our nightly
+ testing
infrastructure normally finds these problems. A good rule of thumb is to
check the nightly testers for regressions the day after your change.</p>
</div>
<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"> <a name="c_new">Obtaining Commit Access</a></div>
+<div class="doc_subsection">
+ <a name="commitaccess">Obtaining Commit Access</a></div>
<div class="doc_text">
<p>
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
llvm-commits</a>. 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. Examples include: fixing build breakage, reverting
+ obvious. This is clearly a subjective decision — we simply expect you
+ to use good judgement. Examples include: fixing build breakage, reverting
obviously broken patches, documentation/comment changes, any other minor
changes.</li>
<li>You are allowed to commit patches without approval to those portions
- of LLVM that you have contributed or maintain (have been assigned
+ 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
reviewed after they are committed.</li>
<li>Multiple violations of these policies or a single egregious violation
may cause commit access to be revoked.</li>
</ol>
+
+<p>In any case, your changes are still subject to <a href="#reviews">code
+review</a> (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.</p>
</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>
+ the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
email list, to the extent possible. The reason for this is to:
<ol>
<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>avoid duplication of effort by preventing 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>
</ol>
<p>The design of LLVM is carefully controlled to ensure that all the pieces
fit together well and are as consistent as possible. 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
+ major change to the way LLVM works or want to add a major new extension, it
+ is a good idea to get consensus with the development
community before you start working on it.</p>
+ <p>Once the design of the new feature is finalized, the work itself should be
+ done as a series of <a href="#incremental">incremental changes</a>, not as
+ a long-term development branch.</p>
+
</div>
<!-- _______________________________________________________________________ -->
-<div class="doc_subs
ubsection"> <a name="incremental">Incremental Development</a>
+<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
</div>
<div class="doc_text">
- <p>Once the design of the new feature is finalized, the work itself should be
- done as a series of incremental changes, not as a long-term development
- branch. Long-term development branches have a number of drawbacks:</p>
+ <p>In the LLVM project, we do all significant changes as a series of
+ incremental patches. We have a strong dislike for huge changes or
+ long-term development branches. Long-term development branches have a
+ number of drawbacks:</p>
<ol>
<li>Branches must have mainline merged into them periodically. If the branch
<li>The remaining inter-related work should be decomposed into unrelated
sets of changes if possible. Once this is done, define the first increment
and get consensus on what the end goal of the change is.</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
+
+ <li>Each change in the set can be stand alone (e.g. to fix a bug), or part
+ of a planned series of changes that works towards the development goal.</li>
+
+ <li>Each change 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>Often, an independent precursor to a big change is to add a new API and
slowly migrate clients to use the new API. Each change to use the new
API is often "obvious" and can be committed without review. Once the
- new API is in place and used, it is often easy to replace the underlying
- implementation of the API.</li>
+ new API is in place and used, it is much easier to replace the
+ underlying implementation of the API. This implementation change is
+ logically separate from the API change.</li>
</ul>
<p>If you are interested in making a large change, and this scares you, please
make sure to first <a href="#newwork">discuss the change/gather
- consensus</a> then feel free to ask about the best way to go about making
+ consensus</a> then ask about the best way to go about making
the change.</p>
</div>
<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 <a
- href="#candl">copyright</a>: it is only used to attribute the file to
+ href="#clp">copyright</a>: it is only used to attribute the file to
its original 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. Revision control keeps an accurate history of contributions.</li>
+ changes. Despite this, once set, the attribution of a file never changes.
+ Revision control keeps an accurate history of contributions.</li>
<li>Developers should maintain their entry in the
<a href="http://llvm.org/cvsweb/cvsweb.cgi/llvm/CREDITS.TXT?rev=HEAD&content-type=text/x-cvsweb-markup">CREDITS.txt</a>
file to summarize their contributions.</li>
</div>
-<!--=========================================================================-->
-<div class="doc_section"><a name="patches">Patch Policies</a></div>
-<!--=========================================================================-->
-
-<div class="doc_text">
- <p>This section describes policies that apply to developers who regularly
- contribute code to LLVM. As usual, we often accept small patches and
- contributions that do not follow this policy. In this case, one of the
- regular contributors has to get the code in shape.</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>Contributions must not knowingly infringe on any patents. 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_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_section"><a name="candl">Copyright and License</a></div>
+<div class="doc_section">
+ <a name="clp">Copyright, License, and Patents</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.
+ <p>This section addresses the issues of copyright, license and patents for
+ the LLVM project.
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>.
+ Illinois/NCSA Open Source License</a>.</p>
<div class="doc_notes">
<p><b>NOTE: This section deals with legal matters but does not provide
- official legal advice. We are not lawyers, please seek legal counsel from an
+ legal advice. We are not lawyers, please seek legal counsel from an
attorney.</b></p>
</div>
-
</div>
<!-- _______________________________________________________________________ -->
read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
if further clarification is needed.</p>
- <p>Note that the LLVM Project does distribute some code that includes GPL
- software (notably, llvm-gcc which is based on the GCC GPL source base).
- This means that anything "linked" into to llvm-gcc must itself be compatible
+ <p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
+ This means that anything "linked" into llvm-gcc must itself be compatible
with the GPL, and must be releasable under the terms of the GPL. This implies
- that you <b>any code linked into llvm-gcc and distributed may be subject to
- the viral aspects of the GPL</b>. This is not a problem for the main LLVM
- distribution (which is already licensed under a more liberal license), but may
- be a problem if you intend to do commercial development without redistributing
- your source code.</p>
+ that <b>any code linked into llvm-gcc and distributed to others may be subject
+ to the viral aspects of the GPL</b> (for example, a proprietary code generator
+ linked into llvm-gcc 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 does not affect code generated by llvm-gcc. It may be a
+ problem if you intend to base commercial development on llvm-gcc without
+ redistributing your source code.</p>
<p>We have no plans to change the license of LLVM. If you have questions
or comments about the license, please contact the <a
href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
</div>
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="patents">Patents</a></div>
+<div class="doc_text">
+
+<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
+ actually removed code from LLVM in the past that was found to infringe).
+ Having code in LLVM that infringes on patents would violate an important
+ goal of the project by making it hard or impossible to reuse the code for
+ arbitrary purposes (including commercial use).</p>
+
+<p>When contributing code, we expect contributors to notify us of any potential
+ for patent-related trouble with their changes. If you own the rights to a
+ patent and would like to contribute code to LLVM that relies on it, we
+ require that you sign an agreement that allows any other user of LLVM to
+ freely use your patent. Please contact the <a
+ href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
+ details.</p>
+</div>
+
+
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
<div class="doc_text">
assign their copyrights to UIUC for any contribution made so that
the entire software base can be managed by a single copyright holder. This
implies that any contributions can be licensed under the license that the
- project uses.</li>
- </ul>
+ project uses.</p>
</div>
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- Written by: the
+ Written by the
<a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
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