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Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]6 <title>LLVM Developer Policy</title>
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8</head>
9<body>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]10
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]11<h1>LLVM Developer Policy</h1>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]12<ol>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]13 <li><a href="#introduction">Introduction</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]14 <li><a href="#policies">Developer Policies</a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]15 <ol>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]16 <li><a href="#informed">Stay Informed</a></li>
17 <li><a href="#patches">Making a Patch</a></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]18 <li><a href="#reviews">Code Reviews</a></li>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]19 <li><a href="#owners">Code Owners</a></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]20 <li><a href="#testcases">Test Cases</a></li>
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]21 <li><a href="#quality">Quality</a></li>
22 <li><a href="#commitaccess">Obtaining Commit Access</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]23 <li><a href="#newwork">Making a Major Change</a></li>
24 <li><a href="#incremental">Incremental Development</a></li>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]25 <li><a href="#attribution">Attribution of Changes</a></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]26 </ol></li>
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]27 <li><a href="#clp">Copyright, License, and Patents</a>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]28 <ol>
29 <li><a href="#copyright">Copyright</a></li>
30 <li><a href="#license">License</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]31 <li><a href="#patents">Patents</a></li>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]32 </ol></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]33</ol>
Chris Lattner2ae49dd2007-02-19 06:24:23 +0000[diff] [blame]34<div class="doc_author">Written by the LLVM Oversight Team</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]35
36<!--=========================================================================-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]37<h2><a name="introduction">Introduction</a></h2>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]38<!--=========================================================================-->
39<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]40<p>This document contains the LLVM Developer Policy which defines the project's
41 policy towards developers and their contributions. The intent of this policy
42 is to eliminate miscommunication, rework, and confusion that might arise from
43 the distributed nature of LLVM's development. By stating the policy in clear
44 terms, we hope each developer can know ahead of time what to expect when
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]45 making LLVM contributions. This policy covers all llvm.org subprojects,
46 including Clang, LLDB, etc.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]47<p>This policy is also designed to accomplish the following objectives:</p>
48
49<ol>
50 <li>Attract both users and developers to the LLVM project.</li>
51
52 <li>Make life as simple and easy for contributors as possible.</li>
53
54 <li>Keep the top of Subversion trees as stable as possible.</li>
55</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]56
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]57<p>This policy is aimed at frequent contributors to LLVM. People interested in
58 contributing one-off patches can do so in an informal way by sending them to
59 the
60 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits
61 mailing list</a> and engaging another developer to see it through the
62 process.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]63</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]64
65<!--=========================================================================-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]66<h2><a name="policies">Developer Policies</a></h2>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]67<!--=========================================================================-->
68<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]69<p>This section contains policies that pertain to frequent LLVM developers. We
70 always welcome <a href="#patches">one-off patches</a> from people who do not
71 routinely contribute to LLVM, but we expect more from frequent contributors
72 to keep the system as efficient as possible for everyone. Frequent LLVM
73 contributors are expected to meet the following requirements in order for
74 LLVM to maintain a high standard of quality.<p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]75</div>
76
77<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]78<h3><a name="informed">Stay Informed</a></h3>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]79<div class="doc_text">
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]80<p>Developers should stay informed by reading at least the "dev" mailing list
81 for the projects you are interested in, such as
82 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> for
83 LLVM, <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
84 for Clang, or <a
85 href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev">lldb-dev</a>
86 for LLDB. If you are doing anything more than just casual work on LLVM, it
87 is suggested that you also subscribe to the "commits" mailing list for the
88 subproject you're interested in, such as
89 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>,
90 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>,
91 or <a href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits">lldb-commits</a>.
92 Reading the "commits" list and paying attention to changes being made by
93 others is a good way to see what other people are interested in and watching
94 the flow of the project as a whole.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]95
96<p>We recommend that active developers register an email account with
97 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
98 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]99 email list to keep track of bugs and enhancements occurring in LLVM. We
100 really appreciate people who are proactive at catching incoming bugs in their
101 components and dealing with them promptly.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]102</div>
103
104<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]105<h3><a name="patches">Making a Patch</a></h3>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]106
107<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]108<p>When making a patch for review, the goal is to make it as easy for the
109 reviewer to read it as possible. As such, we recommend that you:</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]110
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]111<ol>
112 <li>Make your patch against the Subversion trunk, not a branch, and not an old
Chris Lattner9b96e802009-10-10 21:37:16 +0000[diff] [blame]113 version of LLVM. This makes it easy to apply the patch. For information
114 on how to check out SVN trunk, please see the <a
115 href="GettingStarted.html#checkout">Getting Started Guide</a>.</li>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]116
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]117 <li>Similarly, patches should be submitted soon after they are generated. Old
118 patches may not apply correctly if the underlying code changes between the
119 time the patch was created and the time it is applied.</li>
120
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]121 <li>Patches should be made with <tt>svn diff</tt>, or similar. If you use
122 a different tool, make sure it uses the <tt>diff -u</tt> format and
123 that it doesn't contain clutter which makes it hard to read.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]124
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]125 <li>If you are modifying generated files, such as the top-level
126 <tt>configure</tt> script, please separate out those changes into
127 a separate patch from the rest of your changes.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]128</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]129
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]130<p>When sending a patch to a mailing list, it is a good idea to send it as an
131 <em>attachment</em> to the message, not embedded into the text of the
132 message. This ensures that your mailer will not mangle the patch when it
133 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
134
135<p><em>For Thunderbird users:</em> Before submitting a patch, please open
136 <em>Preferences &#8594; Advanced &#8594; General &#8594; Config Editor</em>,
137 find the key <tt>mail.content_disposition_type</tt>, and set its value to
138 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
139 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
140 attachment</tt>. Apple Mail gamely displays such a file inline, making it
141 difficult to work with for reviewers using that program.</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]142</div>
143
144<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]145<h3><a name="reviews">Code Reviews</a></h3>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]146<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]147<p>LLVM has a code review policy. Code review is one way to increase the quality
148 of software. We generally follow these policies:</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]149
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]150<ol>
151 <li>All developers are required to have significant changes reviewed before
152 they are committed to the repository.</li>
153
154 <li>Code reviews are conducted by email, usually on the llvm-commits
155 list.</li>
156
157 <li>Code can be reviewed either before it is committed or after. We expect
158 major changes to be reviewed before being committed, but smaller changes
159 (or changes where the developer owns the component) can be reviewed after
160 commit.</li>
161
162 <li>The developer responsible for a code change is also responsible for making
163 all necessary review-related changes.</li>
164
165 <li>Code review can be an iterative process, which continues until the patch
166 is ready to be committed.</li>
167</ol>
168
169<p>Developers should participate in code reviews as both reviewers and
170 reviewees. If someone is kind enough to review your code, you should return
171 the favor for someone else. Note that anyone is welcome to review and give
172 feedback on a patch, but only people with Subversion write access can approve
173 it.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]174</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]175
176<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]177<h3><a name="owners">Code Owners</a></h3>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]178<div class="doc_text">
179
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]180<p>The LLVM Project relies on two features of its process to maintain rapid
181 development in addition to the high quality of its source base: the
182 combination of code review plus post-commit review for trusted maintainers.
183 Having both is a great way for the project to take advantage of the fact that
184 most people do the right thing most of the time, and only commit patches
185 without pre-commit review when they are confident they are right.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]186
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]187<p>The trick to this is that the project has to guarantee that all patches that
188 are committed are reviewed after they go in: you don't want everyone to
189 assume someone else will review it, allowing the patch to go unreviewed. To
190 solve this problem, we have a notion of an 'owner' for a piece of the code.
191 The sole responsibility of a code owner is to ensure that a commit to their
192 area of the code is appropriately reviewed, either by themself or by someone
193 else. The current code owners are:</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]194
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]195<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]196 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
197
Chris Lattner5ce89812010-09-23 17:27:54 +0000[diff] [blame]198 <li><b>Greg Clayton</b>: LLDB.</li>
199
200 <li><b>Doug Gregor</b>: Clang Frontend Libraries.</li>
201
202 <li><b>Howard Hinnant</b>: libc++.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]203
Chris Lattnerb2030432009-09-16 05:37:13 +0000[diff] [blame]204 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
205 Windows codegen.</li>
206
Chris Lattnerf86a7782009-09-16 05:42:12 +0000[diff] [blame]207 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
208
Chris Lattner941f4cd2009-09-16 05:36:54 +0000[diff] [blame]209 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]210
211 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]212</ol>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]213
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]214<p>Note that code ownership is completely different than reviewers: anyone can
215 review a piece of code, and we welcome code review from anyone who is
216 interested. Code owners are the "last line of defense" to guarantee that all
217 patches that are committed are actually reviewed.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]218
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]219<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
220 important for the ongoing success of the project. Because people get busy,
221 interests change, and unexpected things happen, code ownership is purely
222 opt-in, and anyone can choose to resign their "title" at any time. For now,
223 we do not have an official policy on how one gets elected to be a code
224 owner.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]225</div>
226
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]227<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]228<h3><a name="testcases">Test Cases</a></h3>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]229<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]230<p>Developers are required to create test cases for any bugs fixed and any new
231 features added. Some tips for getting your testcase approved:</p>
232
233<ol>
234 <li>All feature and regression test cases are added to the
235 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
236 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
237 details).</li>
238
239 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
240 language</a> unless the feature or regression being tested requires
241 another language (e.g. the bug being fixed or feature being implemented is
242 in the llvm-gcc C++ front-end, in which case it must be written in
243 C++).</li>
244
245 <li>Test cases, especially for regressions, should be reduced as much as
246 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
247 unacceptable to place an entire failing program into <tt>llvm/test</tt> as
248 this creates a <i>time-to-test</i> burden on all developers. Please keep
249 them short.</li>
250</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]251
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]252<p>Note that llvm/test and clang/test are designed for regression and small
253 feature tests only. More extensive test cases (e.g., entire applications,
254 benchmarks, etc)
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]255 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is
256 for coverage (correctness, performance, etc) testing, not feature or
257 regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]258</div>
259
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]260<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]261<h3><a name="quality">Quality</a></h3>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]262<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]263<p>The minimum quality standards that any change must satisfy before being
264 committed to the main development branch are:</p>
265
266<ol>
267 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
268 Standards</a>.</li>
269
270 <li>Code must compile cleanly (no errors, no warnings) on at least one
271 platform.</li>
272
273 <li>Bug fixes and new features should <a href="#testcases">include a
274 testcase</a> so we know if the fix/feature ever regresses in the
275 future.</li>
276
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]277 <li>Code must pass the <tt>llvm/test</tt> test suite.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]278
279 <li>The code must not cause regressions on a reasonable subset of llvm-test,
280 where "reasonable" depends on the contributor's judgement and the scope of
281 the change (more invasive changes require more testing). A reasonable
282 subset might be something like
283 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
284</ol>
285
286<p>Additionally, the committer is responsible for addressing any problems found
287 in the future that the change is responsible for. For example:</p>
288
289<ul>
290 <li>The code should compile cleanly on all supported platforms.</li>
291
292 <li>The changes should not cause any correctness regressions in the
293 <tt>llvm-test</tt> suite and must not cause any major performance
294 regressions.</li>
295
296 <li>The change set should not cause performance or correctness regressions for
297 the LLVM tools.</li>
298
299 <li>The changes should not cause performance or correctness regressions in
300 code compiled by LLVM on all applicable targets.</li>
301
302 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
303 bugs</a> that result from your change.</li>
304</ul>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]305
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]306<p>We prefer for this to be handled before submission but understand that it
Chris Lattnerd7f10d32009-08-01 19:25:25 +0000[diff] [blame]307 isn't possible to test all of this for every submission. Our build bots and
308 nightly testing infrastructure normally finds these problems. A good rule of
309 thumb is to check the nightly testers for regressions the day after your
310 change. Build bots will directly email you if a group of commits that
311 included yours caused a failure. You are expected to check the build bot
312 messages to see if they are your fault and, if so, fix the breakage.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]313
314<p>Commits that violate these quality standards (e.g. are very broken) may be
315 reverted. This is necessary when the change blocks other developers from
316 making progress. The developer is welcome to re-commit the change after the
317 problem has been fixed.</p>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]318</div>
319
320<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]321<h3><a name="commitaccess">Obtaining Commit Access</a></h3>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]322<div class="doc_text">
323
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]324<p>We grant commit access to contributors with a track record of submitting high
325 quality patches. If you would like commit access, please send an email to
326 <a href="mailto:sabre@nondot.org">Chris</a> with the following
327 information:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]328
329<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]330 <li>The user name you want to commit with, e.g. "hacker".</li>
331
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]332 <li>The full name and email address you want message to llvm-commits to come
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]333 from, e.g. "J. Random Hacker &lt;hacker@yoyodyne.com&gt;".</li>
334
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]335 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
336 Note that you don't ever tell us what your password is, you just give it
337 to us in an encrypted form. To get this, run "htpasswd" (a utility that
338 comes with apache) in crypt mode (often enabled with "-d"), or find a web
339 page that will do it for you.</li>
340</ol>
341
342<p>Once you've been granted commit access, you should be able to check out an
343 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
344 normal anonymous URL of "http://llvm.org/...". The first time you commit
345 you'll have to type in your password. Note that you may get a warning from
346 SVN about an untrusted key, you can ignore this. To verify that your commit
347 access works, please do a test commit (e.g. change a comment or add a blank
348 line). Your first commit to a repository may require the autogenerated email
349 to be approved by a mailing list. This is normal, and will be done when
350 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]351
352<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]353
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]354<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]355 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get
356 approval, submit a <a href="#patches">patch</a> to
357 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
358 When approved you may commit it yourself.</li>
359
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]360 <li>You are allowed to commit patches without approval which you think are
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]361 obvious. This is clearly a subjective decision &mdash; we simply expect
362 you to use good judgement. Examples include: fixing build breakage,
363 reverting obviously broken patches, documentation/comment changes, any
364 other minor changes.</li>
365
366 <li>You are allowed to commit patches without approval to those portions of
367 LLVM that you have contributed or maintain (i.e., have been assigned
368 responsibility for), with the proviso that such commits must not break the
369 build. This is a "trust but verify" policy and commits of this nature are
370 reviewed after they are committed.</li>
371
372 <li>Multiple violations of these policies or a single egregious violation may
373 cause commit access to be revoked.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]374</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]375
376<p>In any case, your changes are still subject to <a href="#reviews">code
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]377 review</a> (either before or after they are committed, depending on the
378 nature of the change). You are encouraged to review other peoples' patches
379 as well, but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]380</div>
381
382<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]383<h3><a name="newwork">Making a Major Change</a></h3>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]384<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]385<p>When a developer begins a major new project with the aim of contributing it
386 back to LLVM, s/he should inform the community with an email to
387 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
388 email list, to the extent possible. The reason for this is to:
389
390<ol>
391 <li>keep the community informed about future changes to LLVM, </li>
392
393 <li>avoid duplication of effort by preventing multiple parties working on the
394 same thing and not knowing about it, and</li>
395
396 <li>ensure that any technical issues around the proposed work are discussed
397 and resolved before any significant work is done.</li>
398</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]399
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]400<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
401 together well and are as consistent as possible. If you plan to make a major
402 change to the way LLVM works or want to add a major new extension, it is a
403 good idea to get consensus with the development community before you start
404 working on it.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]405
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]406<p>Once the design of the new feature is finalized, the work itself should be
407 done as a series of <a href="#incremental">incremental changes</a>, not as a
408 long-term development branch.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]409</div>
410
411<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]412<h3><a name="incremental">Incremental Development</a></h3>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]413<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]414<p>In the LLVM project, we do all significant changes as a series of incremental
415 patches. We have a strong dislike for huge changes or long-term development
416 branches. Long-term development branches have a number of drawbacks:</p>
417
418<ol>
419 <li>Branches must have mainline merged into them periodically. If the branch
420 development and mainline development occur in the same pieces of code,
421 resolving merge conflicts can take a lot of time.</li>
422
423 <li>Other people in the community tend to ignore work on branches.</li>
424
425 <li>Huge changes (produced when a branch is merged back onto mainline) are
426 extremely difficult to <a href="#reviews">code review</a>.</li>
427
428 <li>Branches are not routinely tested by our nightly tester
429 infrastructure.</li>
430
431 <li>Changes developed as monolithic large changes often don't work until the
432 entire set of changes is done. Breaking it down into a set of smaller
433 changes increases the odds that any of the work will be committed to the
434 main repository.</li>
435</ol>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]436
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]437<p>To address these problems, LLVM uses an incremental development style and we
438 require contributors to follow this practice when making a large/invasive
439 change. Some tips:</p>
440
441<ul>
442 <li>Large/invasive changes usually have a number of secondary changes that are
443 required before the big change can be made (e.g. API cleanup, etc). These
444 sorts of changes can often be done before the major change is done,
445 independently of that work.</li>
446
447 <li>The remaining inter-related work should be decomposed into unrelated sets
448 of changes if possible. Once this is done, define the first increment and
449 get consensus on what the end goal of the change is.</li>
450
451 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
452 a planned series of changes that works towards the development goal.</li>
453
454 <li>Each change should be kept as small as possible. This simplifies your work
455 (into a logical progression), simplifies code review and reduces the
456 chance that you will get negative feedback on the change. Small increments
457 also facilitate the maintenance of a high quality code base.</li>
458
459 <li>Often, an independent precursor to a big change is to add a new API and
460 slowly migrate clients to use the new API. Each change to use the new API
461 is often "obvious" and can be committed without review. Once the new API
462 is in place and used, it is much easier to replace the underlying
463 implementation of the API. This implementation change is logically
464 separate from the API change.</li>
465</ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]466
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]467<p>If you are interested in making a large change, and this scares you, please
468 make sure to first <a href="#newwork">discuss the change/gather consensus</a>
469 then ask about the best way to go about making the change.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]470</div>
471
472<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]473<h3><a name="attribution">Attribution of Changes</a></h3>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]474<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]475<p>We believe in correct attribution of contributions to their contributors.
476 However, we do not want the source code to be littered with random
477 attributions "this code written by J. Random Hacker" (this is noisy and
478 distracting). In practice, the revision control system keeps a perfect
479 history of who changed what, and the CREDITS.txt file describes higher-level
480 contributions. If you commit a patch for someone else, please say "patch
481 contributed by J. Random Hacker!" in the commit message.</p>
Chris Lattnerab2b10c2007-12-29 19:56:08 +0000[diff] [blame]482
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]483<p>Overall, please do not add contributor names to the source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]484</div>
485
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]486<!--=========================================================================-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]487<h2>
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]488 <a name="clp">Copyright, License, and Patents</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]489</h2>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]490<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]491
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]492<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]493<p>This section addresses the issues of copyright, license and patents for the
494 LLVM project. Currently, the University of Illinois is the LLVM copyright
495 holder and the terms of its license to LLVM users and developers is the
496 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
497 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]498
499<div class="doc_notes">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]500<p style="text-align:center;font-weight:bold">NOTE: This section deals with
501 legal matters but does not provide legal advice. We are not lawyers, please
502 seek legal counsel from an attorney.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]503</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]504</div>
505
506<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]507<h3><a name="copyright">Copyright</a></h3>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]508<div class="doc_text">
Chris Lattner305915b2008-05-20 20:06:53 +0000[diff] [blame]509
Chris Lattnerc226fc82010-09-27 21:17:15 +0000[diff] [blame]510<p>The LLVM project does not require copyright assignments, which means that the
511 copyright for the code in the project is held by its respective contributors
512 who have each agreed to release their contributed code under the terms of the
513 <a href="#license">LLVM License</a>.</p>
514
515<p>An implication of this is that the LLVM license is unlikely to ever change:
516 changing it would require tracking down all the contributors to LLVM and
517 getting them to agree that a license change is acceptable for their
518 contribution. Since there are no plans to change the license, this is not a
519 cause for concern.</p>
520
521<p>As a contributor to the project, this means that you (or your company) retain
522 ownership of the code you contribute, that it cannot be used in a way that
523 contradicts the license (which is a liberal BSD-style license), and that the
524 license for your contributions won't change without your approval in the
525 future.</p>
526
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]527</div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]528
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]529<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]530<h3><a name="license">License</a></h3>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]531<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]532<p>We intend to keep LLVM perpetually open source and to use a liberal open
Chris Lattnerac139f12010-11-16 21:32:53 +0000[diff] [blame]533 source license. All of the code in LLVM is available under the
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]534 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
Dan Gohman621a4152010-02-26 20:18:32 +0000[diff] [blame]535 Illinois/NCSA Open Source License</a>, which boils down to this:</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]536
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]537<ul>
538 <li>You can freely distribute LLVM.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]539 <li>You must retain the copyright notice if you redistribute LLVM.</li>
Chris Lattnerac139f12010-11-16 21:32:53 +0000[diff] [blame]540 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in an
541 included readme file).</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]542 <li>You can't use our names to promote your LLVM derived products.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]543 <li>There's no warranty on LLVM at all.</li>
544</ul>
545
546<p>We believe this fosters the widest adoption of LLVM because it <b>allows
547 commercial products to be derived from LLVM</b> with few restrictions and
548 without a requirement for making any derived works also open source (i.e.
549 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
550 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
551 if further clarification is needed.</p>
Chris Lattnerac139f12010-11-16 21:32:53 +0000[diff] [blame]552
553<p>In addition to the UIUC license, the runtime library components of LLVM
554 (<b>compiler_rt and libc++</b>) are also licensed under the <a
555 href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>,
556 which does not contain the binary redistribution clause. As a user of these
557 runtime libraries, it means that you can choose to use the code under either
558 license (and thus don't need the binary redistribution clause), and as a
559 contributor to the code that you agree that any contributions to these
560 libraries be licensed under both licenses. We feel that this is important
561 for runtime libraries, because they are implicitly linked into applications
562 and therefore should not subject those applications to the binary
563 redistribution clause. This also means that it is ok to move code from (e.g.)
564 libc++ to the LLVM core without concern, but that code cannot be moved from
565 the LLVM core to libc++ without the copyright owner's permission.
566</p>
567
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]568<p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
569 This means that anything "linked" into llvm-gcc must itself be compatible
570 with the GPL, and must be releasable under the terms of the GPL. This
571 implies that <b>any code linked into llvm-gcc and distributed to others may
572 be subject to the viral aspects of the GPL</b> (for example, a proprietary
573 code generator linked into llvm-gcc must be made available under the GPL).
574 This is not a problem for code already distributed under a more liberal
575 license (like the UIUC license), and does not affect code generated by
576 llvm-gcc. It may be a problem if you intend to base commercial development
577 on llvm-gcc without redistributing your source code.</p>
578
579<p>We have no plans to change the license of LLVM. If you have questions or
580 comments about the license, please contact the
Chris Lattnerac139f12010-11-16 21:32:53 +0000[diff] [blame]581 <a href="mailto:llvmdev@cs.uiuc.edu">LLVM Developer's Mailing List</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]582</div>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]583
584<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame^]585<h3><a name="patents">Patents</a></h3>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]586<div class="doc_text">
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]587<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
588 actually removed code from LLVM in the past that was found to infringe).
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]589 Having code in LLVM that infringes on patents would violate an important goal
590 of the project by making it hard or impossible to reuse the code for
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]591 arbitrary purposes (including commercial use).</p>
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]592
593<p>When contributing code, we expect contributors to notify us of any potential
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]594 for patent-related trouble with their changes. If you or your employer own
595 the rights to a patent and would like to contribute code to LLVM that relies
596 on it, we require that the copyright owner sign an agreement that allows any
597 other user of LLVM to freely use your patent. Please contact
598 the <a href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]599 details.</p>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]600</div>
601
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]602<!-- *********************************************************************** -->
603<hr>
604<address>
605 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]606 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]607 <a href="http://validator.w3.org/check/referer"><img
Misha Brukmanf00ddb02008-12-11 18:23:24 +0000[diff] [blame]608 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]609 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]610 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]611 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]612 Last modified: $Date$
613</address>
614</body>
615</html>