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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>LLVM Developer Policy</title>
<link rel="stylesheet" href="llvm.css" type="text/css">
</head>
<body>
<div class="doc_title">LLVM Developer Policy</div>
<ol>
<li><a href="#introduction">Introduction</a></li>
<li><a href="#policies">Developer Policies</a>
<ol>
<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="#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="#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 the LLVM Oversight Team</div>
<!--=========================================================================-->
<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>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="policies">Developer Policies</a></div>
<!--=========================================================================-->
<div class="doc_text">
<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 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="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 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>
</div>
<!-- _______________________________________________________________________ -->
<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 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, 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-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 Subversion write access
can approve it.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsection"> <a name="owners">Code Owners</a></div>
<div class="doc_text">
<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><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 any bugs fixed and any new
features added. Some tips for getting your testcase approved:</p>
<ol>
<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 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="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>
</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_subsection"> <a name="quality">Quality</a></div>
<div class="doc_text">
<p>The minimum quality standards that any change must satisfy before being
committed 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>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 "reas
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