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</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>
+ <li><a href="#policies">Developer Policies</a>
<ol>
- <li><a href="#informed">Stay Informed</a> </li>
- <li><a href="#newwork">Starting New Work</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="#incremental">Incremental Development</a></li>
- <li><a href="#quality">Quality</a></li>
+ <li><a href="#owners">Code Owners</a></li>
<li><a href="#testcases">Test Cases</a></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_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>
+ <li><a href="#clp">Copyright, License, and Patents</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="#patents">Patents</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_author">Written by the LLVM Oversight Team</div>
<!--=========================================================================-->
<div class="doc_section"><a name="introduction">Introduction</a></div>
<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>
+ <li>Keep the top of Subversion trees as stable as possible.</li>
</ol>
+
+ <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
+ the process.</p>
+
</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 LLVM developers.
- LLVM Developers are expected to meet the following obligations in order
- for LLVM to maintain a high standard of quality.<p>
+ <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>
<!-- _______________________________________________________________________ -->
</div>
<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"> <a name="newwork">Starting New Work</a></div>
+<div class="doc_subsection"> <a name="patches">Making a Patch</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>
+
+<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 Subversion 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>svn diff -x -u</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>
+
+ <p><em>For Thunderbird users:</em> Before submitting a patch, please open
+ <em>Preferences → Advanced → General → Config Editor</em>,
+ find the key <tt>mail.content_disposition_type</tt>, and set its value to
+ <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
+ <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
+ attachment</tt>. Apple Mail gamely displays such a file inline, making it
+ difficult to work with for reviewers using that program.</p>
+</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>
+ <p>LLVM has a code review policy. Code review is one way to increase the
+ quality of software. We generally follow these policies:</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>Code reviews are conducted by email, usually on the llvm-commits
+ list.</li>
+ <li>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 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 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>
-</div>
+
+ <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 Subversion write access
+ can approve it.</p>
-<!-- _______________________________________________________________________ -->
-<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_subsection"> <a name="owners">Code Owners</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>
+
+ <p>The LLVM Project relies on two features of its process to maintain rapid
+ development in addition to the high quality of its source base: the
+ combination of code review plus post-commit review for trusted maintainers.
+ Having both is a great way for the project to take advantage of the fact
+ that most people do the right thing most of the time, and only commit
+ patches without pre-commit review when they are confident they are
+ right.</p>
+
+ <p>The trick to this is that the project has to guarantee that all patches
+ that are committed are reviewed after they go in: you don't want everyone
+ to assume someone else will review it, allowing the patch to go unreviewed.
+ To solve this problem, we have a notion of an 'owner' for a piece of the
+ code. The sole 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 current code owners are:</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>
+ <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
+ Windows codegen.</li>
+ <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
+ <li><b>Evan Cheng</b>: Code generator and all targets.</li>
+ <li><b>Chris Lattner</b>: Everything else.</li>
</ol>
+
+ <p>Note that code ownership is completely different than reviewers: anyone can
+ review a piece of code, and we welcome code review from anyone who is
+ interested. Code owners are the "last line of defense" to guarantee that
+ all patches that are committed are actually reviewed.</p>
+
+ <p>Being a code owner is a somewhat unglamorous position, but it is incredibly
+ important for the ongoing success of the project. Because people get busy,
+ interests change, and unexpected things happen, code ownership is purely
+ opt-in, and anyone can choose to resign their "title" at any time. For now,
+ we do not have an official policy on how one gets elected to be a code
+ owner.
+ </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 regressions and new
- features and include them with their changes. The following policies
- apply:</p>
+ <p>Developers are required to create test cases for any bugs fixed and any new
+ 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>
<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>
+ bug being fixed or feature being implemented is in the llvm-gcc C++
+ 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>
-<!--=========================================================================-->
-<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_subsection"> <a name="quality">Quality</a></div>
<div class="doc_text">
- <p>When a patch is ready to be submitted, these policies apply:</p>
+ <p>The minimum quality standards that any change must satisfy before being
+ committed to the main development branch are:</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>
+ <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>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 (<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
+ subset is "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
</ol>
+ <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 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
+ code compiled by LLVM on all applicable targets.</li>
+ <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
+ bugs</a> that result from your change.</li>
+ </ul>
+
+ <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>
+
+ <p>Commits that violate these quality standards (e.g. are very broken) 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.</p>
</div>
<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"> <a name="p_aftersub">After Submission</a></div>
+<div class="doc_subsection">
+ <a name="commitaccess">Obtaining Commit Access</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>
+
+<p>
+We grant commit access to contributors with a track record of submitting high
+quality patches. If you would like commit access, please send an email to
+<a href="mailto:sabre@nondot.org">Chris</a> with the following information:</p>
+
+<ol>
+ <li>The user name you want to commit with, e.g. "sabre".</li>
+ <li>The full name and email address you want message to llvm-commits to come
+ from, e.g. "Chris Lattner <sabre@nondot.org>".</li>
+ <li>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 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.</li>
+</ol>
+
+<p>Once you've been granted commit access, you should be able to check out an
+ LLVM 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, 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 time.</p>
+
+<p>If you have recently been granted commit access, these policies apply:</p>
+
+<ol>
+ <li>You are granted <i>commit-after-approval</i> to all parts of LLVM.
+ To get approval, submit a <a href="#patches">patch</a> to
+ <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
+ 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 (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_subsection"> <a name="p_aftercommit">After Commit</a></div>
+<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
<div class="doc_text">
- <p>After a patch has been committed, these policies apply:</p>
+ <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">llvmdev</a>
+ email list, to the extent possible. The reason for this is to:
<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>
+ <li>keep the community informed about future changes to LLVM, </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 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_subsection"> <a name="c_access">Obtaining Commit Access</a></div>
+<div class="doc_subsection"> <a name="incremental">Incremental Development</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>
+ <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
+ development and mainline development occur in the same pieces of code,
+ resolving merge conflicts can take a lot of time.</li>
+ <li>Other people in the community tend to ignore work on branches.</li>
+ <li>Huge changes (produced when a branch is merged back onto mainline) are
+ extremely difficult to <a href="#reviews">code review</a>.</li>
+ <li>Branches are not routinely tested by our nightly tester
+ infrastructure.</li>
+ <li>Changes developed as monolithic large changes often don't work until the
+ entire set of changes is done. Breaking it down into a set of smaller
+ changes increases the odds that any of the work will be committed to the
+ main repository.</li>
+ </ol>
+
+ <p>
+ To address these problems, LLVM uses an incremental development style and we
+ require contributors to follow this practice when making a large/invasive
+ change. Some tips:</p>
+
+ <ul>
+ <li>Large/invasive changes usually have a number of secondary changes that
+ are required before the big change can be made (e.g. API cleanup, etc).
+ These sorts of changes can often be done before the major change is done,
+ independently of that work.</li>
+ <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>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 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 ask about the best way to go about making
+ the change.</p>
</div>
<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"> <a name="c_new">New Committers</a></div>
+<div class="doc_subsection"><a name="attribution">Attribution of
+Changes</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>
+ <p>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 Guy" (this is noisy
+ and distracting. In practice, the revision control system keeps a perfect
+ history of who change what, and the CREDITS.txt file describes higher-level
+ contributions.</p>
+
+ <p>Overall, please do not add contributor names to the source base.</p>
</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>.
-</div>
+ Illinois/NCSA Open Source License</a>.</p>
<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>
+ <p><b>NOTE: This section deals with legal matters but does not provide
+ legal advice. We are not lawyers, please seek legal counsel from an
+ attorney.</b></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_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
+ copyright for all LLVM software to be held by a single copyright holder:
+ the University of Illinois (UIUC).</p>
+
+ <p>
+ Although UIUC may eventually reassign the copyright of the software to another
+ entity (e.g. a dedicated non-profit "LLVM Organization")
+ the intent for the project is to always have a single entity hold the
+ copyrights to LLVM at any given time.</p>
+
+ <p>We believe that 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>
+ decisions about LLVM. The goal of the LLVM project is to always keep the code
+ open and <a href="#license">licensed under a very liberal license</a>.</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
+ <p>We intend to keep LLVM perpetually open source
+ and to use a liberal open source license. 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>Binaries derived from LLVM must reproduce the copyright notice (e.g.
+ in an included readme file).</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
+
+ <p>We believe this fosters the widest adoption of LLVM because it <b>allows
+ commercial products to be derived from LLVM</b> 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>
+ LLVM's license is not a "copyleft" license like the GPL). We suggest that you
+ 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 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 <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="devagree">Developer Agreements</a></div>
+<div class="doc_subsection"><a name="patents">Patents</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>
+<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 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 <a
+ href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
+ details.</p>
</div>
-<!--=========================================================================-->
-<div class="doc_section"><a name="polnotes">Policy Notes</a></div>
-<!--=========================================================================-->
+
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="devagree">Developer Agreements</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>
+ <p>With regards to the LLVM copyright and licensing, developers agree to
+ 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.</p>
+
+ <p>When contributing code, you also affirm that you are legally entitled to
+ grant this copyright, personally or on behalf of your employer. If the code
+ belongs to some other entity, please raise this issue with the oversight
+ group before the code is committed.</p>
</div>
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- Written By: the
+ Written by the
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