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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<!--=========================================================================-->
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]39<div>
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<!--=========================================================================-->
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]68<div>
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
76<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]77<h3><a name="informed">Stay Informed</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]78<div>
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]79<p>Developers should stay informed by reading at least the "dev" mailing list
80 for the projects you are interested in, such as
81 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> for
82 LLVM, <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
83 for Clang, or <a
84 href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev">lldb-dev</a>
85 for LLDB. If you are doing anything more than just casual work on LLVM, it
86 is suggested that you also subscribe to the "commits" mailing list for the
87 subproject you're interested in, such as
88 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>,
89 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>,
90 or <a href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits">lldb-commits</a>.
91 Reading the "commits" list and paying attention to changes being made by
92 others is a good way to see what other people are interested in and watching
93 the flow of the project as a whole.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]94
95<p>We recommend that active developers register an email account with
96 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
97 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]98 email list to keep track of bugs and enhancements occurring in LLVM. We
99 really appreciate people who are proactive at catching incoming bugs in their
100 components and dealing with them promptly.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]101</div>
102
103<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]104<h3><a name="patches">Making a Patch</a></h3>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]105
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]106<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]107<p>When making a patch for review, the goal is to make it as easy for the
108 reviewer to read it as possible. As such, we recommend that you:</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]109
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]110<ol>
111 <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]112 version of LLVM. This makes it easy to apply the patch. For information
113 on how to check out SVN trunk, please see the <a
114 href="GettingStarted.html#checkout">Getting Started Guide</a>.</li>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]115
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]116 <li>Similarly, patches should be submitted soon after they are generated. Old
117 patches may not apply correctly if the underlying code changes between the
118 time the patch was created and the time it is applied.</li>
119
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]120 <li>Patches should be made with <tt>svn diff</tt>, or similar. If you use
121 a different tool, make sure it uses the <tt>diff -u</tt> format and
122 that it doesn't contain clutter which makes it hard to read.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]123
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]124 <li>If you are modifying generated files, such as the top-level
125 <tt>configure</tt> script, please separate out those changes into
126 a separate patch from the rest of your changes.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]127</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]128
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]129<p>When sending a patch to a mailing list, it is a good idea to send it as an
130 <em>attachment</em> to the message, not embedded into the text of the
131 message. This ensures that your mailer will not mangle the patch when it
132 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
133
134<p><em>For Thunderbird users:</em> Before submitting a patch, please open
135 <em>Preferences &#8594; Advanced &#8594; General &#8594; Config Editor</em>,
136 find the key <tt>mail.content_disposition_type</tt>, and set its value to
137 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
138 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
139 attachment</tt>. Apple Mail gamely displays such a file inline, making it
140 difficult to work with for reviewers using that program.</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]141</div>
142
143<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]144<h3><a name="reviews">Code Reviews</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]145<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]146<p>LLVM has a code review policy. Code review is one way to increase the quality
147 of software. We generally follow these policies:</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]148
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]149<ol>
150 <li>All developers are required to have significant changes reviewed before
151 they are committed to the repository.</li>
152
153 <li>Code reviews are conducted by email, usually on the llvm-commits
154 list.</li>
155
156 <li>Code can be reviewed either before it is committed or after. We expect
157 major changes to be reviewed before being committed, but smaller changes
158 (or changes where the developer owns the component) can be reviewed after
159 commit.</li>
160
161 <li>The developer responsible for a code change is also responsible for making
162 all necessary review-related changes.</li>
163
164 <li>Code review can be an iterative process, which continues until the patch
165 is ready to be committed.</li>
166</ol>
167
168<p>Developers should participate in code reviews as both reviewers and
169 reviewees. If someone is kind enough to review your code, you should return
170 the favor for someone else. Note that anyone is welcome to review and give
171 feedback on a patch, but only people with Subversion write access can approve
172 it.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]173</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]174
175<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]176<h3><a name="owners">Code Owners</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]177<div>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]178
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]179<p>The LLVM Project relies on two features of its process to maintain rapid
180 development in addition to the high quality of its source base: the
181 combination of code review plus post-commit review for trusted maintainers.
182 Having both is a great way for the project to take advantage of the fact that
183 most people do the right thing most of the time, and only commit patches
184 without pre-commit review when they are confident they are right.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]185
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]186<p>The trick to this is that the project has to guarantee that all patches that
187 are committed are reviewed after they go in: you don't want everyone to
188 assume someone else will review it, allowing the patch to go unreviewed. To
189 solve this problem, we have a notion of an 'owner' for a piece of the code.
190 The sole responsibility of a code owner is to ensure that a commit to their
191 area of the code is appropriately reviewed, either by themself or by someone
192 else. The current code owners are:</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]193
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]194<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]195 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
196
Chris Lattner5ce89812010-09-23 17:27:54 +0000[diff] [blame]197 <li><b>Greg Clayton</b>: LLDB.</li>
198
199 <li><b>Doug Gregor</b>: Clang Frontend Libraries.</li>
200
201 <li><b>Howard Hinnant</b>: libc++.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]202
Chris Lattnerb2030432009-09-16 05:37:13 +0000[diff] [blame]203 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
204 Windows codegen.</li>
205
Chris Lattnerf86a7782009-09-16 05:42:12 +0000[diff] [blame]206 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
207
Chris Lattner941f4cd2009-09-16 05:36:54 +0000[diff] [blame]208 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]209
210 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]211</ol>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]212
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]213<p>Note that code ownership is completely different than reviewers: anyone can
214 review a piece of code, and we welcome code review from anyone who is
215 interested. Code owners are the "last line of defense" to guarantee that all
216 patches that are committed are actually reviewed.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]217
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]218<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
219 important for the ongoing success of the project. Because people get busy,
220 interests change, and unexpected things happen, code ownership is purely
221 opt-in, and anyone can choose to resign their "title" at any time. For now,
222 we do not have an official policy on how one gets elected to be a code
223 owner.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]224</div>
225
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]226<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]227<h3><a name="testcases">Test Cases</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]228<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]229<p>Developers are required to create test cases for any bugs fixed and any new
230 features added. Some tips for getting your testcase approved:</p>
231
232<ol>
233 <li>All feature and regression test cases are added to the
234 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
235 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
236 details).</li>
237
238 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
239 language</a> unless the feature or regression being tested requires
240 another language (e.g. the bug being fixed or feature being implemented is
241 in the llvm-gcc C++ front-end, in which case it must be written in
242 C++).</li>
243
244 <li>Test cases, especially for regressions, should be reduced as much as
245 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
246 unacceptable to place an entire failing program into <tt>llvm/test</tt> as
247 this creates a <i>time-to-test</i> burden on all developers. Please keep
248 them short.</li>
249</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]250
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]251<p>Note that llvm/test and clang/test are designed for regression and small
252 feature tests only. More extensive test cases (e.g., entire applications,
253 benchmarks, etc)
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]254 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is
255 for coverage (correctness, performance, etc) testing, not feature or
256 regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]257</div>
258
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]259<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]260<h3><a name="quality">Quality</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]261<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]262<p>The minimum quality standards that any change must satisfy before being
263 committed to the main development branch are:</p>
264
265<ol>
266 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
267 Standards</a>.</li>
268
269 <li>Code must compile cleanly (no errors, no warnings) on at least one
270 platform.</li>
271
272 <li>Bug fixes and new features should <a href="#testcases">include a
273 testcase</a> so we know if the fix/feature ever regresses in the
274 future.</li>
275
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]276 <li>Code must pass the <tt>llvm/test</tt> test suite.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]277
278 <li>The code must not cause regressions on a reasonable subset of llvm-test,
279 where "reasonable" depends on the contributor's judgement and the scope of
280 the change (more invasive changes require more testing). A reasonable
281 subset might be something like
282 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
283</ol>
284
285<p>Additionally, the committer is responsible for addressing any problems found
286 in the future that the change is responsible for. For example:</p>
287
288<ul>
289 <li>The code should compile cleanly on all supported platforms.</li>
290
291 <li>The changes should not cause any correctness regressions in the
292 <tt>llvm-test</tt> suite and must not cause any major performance
293 regressions.</li>
294
295 <li>The change set should not cause performance or correctness regressions for
296 the LLVM tools.</li>
297
298 <li>The changes should not cause performance or correctness regressions in
299 code compiled by LLVM on all applicable targets.</li>
300
301 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
302 bugs</a> that result from your change.</li>
303</ul>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]304
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]305<p>We prefer for this to be handled before submission but understand that it
Chris Lattnerd7f10d32009-08-01 19:25:25 +0000[diff] [blame]306 isn't possible to test all of this for every submission. Our build bots and
307 nightly testing infrastructure normally finds these problems. A good rule of
308 thumb is to check the nightly testers for regressions the day after your
309 change. Build bots will directly email you if a group of commits that
310 included yours caused a failure. You are expected to check the build bot
311 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]312
313<p>Commits that violate these quality standards (e.g. are very broken) may be
314 reverted. This is necessary when the change blocks other developers from
315 making progress. The developer is welcome to re-commit the change after the
316 problem has been fixed.</p>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]317</div>
318
319<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]320<h3><a name="commitaccess">Obtaining Commit Access</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]321<div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]322
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]323<p>We grant commit access to contributors with a track record of submitting high
324 quality patches. If you would like commit access, please send an email to
325 <a href="mailto:sabre@nondot.org">Chris</a> with the following
326 information:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]327
328<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]329 <li>The user name you want to commit with, e.g. "hacker".</li>
330
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]331 <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]332 from, e.g. "J. Random Hacker &lt;hacker@yoyodyne.com&gt;".</li>
333
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]334 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
335 Note that you don't ever tell us what your password is, you just give it
336 to us in an encrypted form. To get this, run "htpasswd" (a utility that
337 comes with apache) in crypt mode (often enabled with "-d"), or find a web
338 page that will do it for you.</li>
339</ol>
340
341<p>Once you've been granted commit access, you should be able to check out an
342 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
343 normal anonymous URL of "http://llvm.org/...". The first time you commit
344 you'll have to type in your password. Note that you may get a warning from
345 SVN about an untrusted key, you can ignore this. To verify that your commit
346 access works, please do a test commit (e.g. change a comment or add a blank
347 line). Your first commit to a repository may require the autogenerated email
348 to be approved by a mailing list. This is normal, and will be done when
349 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]350
351<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]352
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]353<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]354 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get
355 approval, submit a <a href="#patches">patch</a> to
356 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
357 When approved you may commit it yourself.</li>
358
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]359 <li>You are allowed to commit patches without approval which you think are
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]360 obvious. This is clearly a subjective decision &mdash; we simply expect
361 you to use good judgement. Examples include: fixing build breakage,
362 reverting obviously broken patches, documentation/comment changes, any
363 other minor changes.</li>
364
365 <li>You are allowed to commit patches without approval to those portions of
366 LLVM that you have contributed or maintain (i.e., have been assigned
367 responsibility for), with the proviso that such commits must not break the
368 build. This is a "trust but verify" policy and commits of this nature are
369 reviewed after they are committed.</li>
370
371 <li>Multiple violations of these policies or a single egregious violation may
372 cause commit access to be revoked.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]373</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]374
375<p>In any case, your changes are still subject to <a href="#reviews">code
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]376 review</a> (either before or after they are committed, depending on the
377 nature of the change). You are encouraged to review other peoples' patches
378 as well, but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]379</div>
380
381<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]382<h3><a name="newwork">Making a Major Change</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]383<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]384<p>When a developer begins a major new project with the aim of contributing it
385 back to LLVM, s/he should inform the community with an email to
386 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
387 email list, to the extent possible. The reason for this is to:
388
389<ol>
390 <li>keep the community informed about future changes to LLVM, </li>
391
392 <li>avoid duplication of effort by preventing multiple parties working on the
393 same thing and not knowing about it, and</li>
394
395 <li>ensure that any technical issues around the proposed work are discussed
396 and resolved before any significant work is done.</li>
397</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]398
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]399<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
400 together well and are as consistent as possible. If you plan to make a major
401 change to the way LLVM works or want to add a major new extension, it is a
402 good idea to get consensus with the development community before you start
403 working on it.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]404
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]405<p>Once the design of the new feature is finalized, the work itself should be
406 done as a series of <a href="#incremental">incremental changes</a>, not as a
407 long-term development branch.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]408</div>
409
410<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]411<h3><a name="incremental">Incremental Development</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]412<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]413<p>In the LLVM project, we do all significant changes as a series of incremental
414 patches. We have a strong dislike for huge changes or long-term development
415 branches. Long-term development branches have a number of drawbacks:</p>
416
417<ol>
418 <li>Branches must have mainline merged into them periodically. If the branch
419 development and mainline development occur in the same pieces of code,
420 resolving merge conflicts can take a lot of time.</li>
421
422 <li>Other people in the community tend to ignore work on branches.</li>
423
424 <li>Huge changes (produced when a branch is merged back onto mainline) are
425 extremely difficult to <a href="#reviews">code review</a>.</li>
426
427 <li>Branches are not routinely tested by our nightly tester
428 infrastructure.</li>
429
430 <li>Changes developed as monolithic large changes often don't work until the
431 entire set of changes is done. Breaking it down into a set of smaller
432 changes increases the odds that any of the work will be committed to the
433 main repository.</li>
434</ol>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]435
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]436<p>To address these problems, LLVM uses an incremental development style and we
437 require contributors to follow this practice when making a large/invasive
438 change. Some tips:</p>
439
440<ul>
441 <li>Large/invasive changes usually have a number of secondary changes that are
442 required before the big change can be made (e.g. API cleanup, etc). These
443 sorts of changes can often be done before the major change is done,
444 independently of that work.</li>
445
446 <li>The remaining inter-related work should be decomposed into unrelated sets
447 of changes if possible. Once this is done, define the first increment and
448 get consensus on what the end goal of the change is.</li>
449
450 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
451 a planned series of changes that works towards the development goal.</li>
452
453 <li>Each change should be kept as small as possible. This simplifies your work
454 (into a logical progression), simplifies code review and reduces the
455 chance that you will get negative feedback on the change. Small increments
456 also facilitate the maintenance of a high quality code base.</li>
457
458 <li>Often, an independent precursor to a big change is to add a new API and
459 slowly migrate clients to use the new API. Each change to use the new API
460 is often "obvious" and can be committed without review. Once the new API
461 is in place and used, it is much easier to replace the underlying
462 implementation of the API. This implementation change is logically
463 separate from the API change.</li>
464</ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]465
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]466<p>If you are interested in making a large change, and this scares you, please
467 make sure to first <a href="#newwork">discuss the change/gather consensus</a>
468 then ask about the best way to go about making the change.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]469</div>
470
471<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]472<h3><a name="attribution">Attribution of Changes</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]473<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]474<p>We believe in correct attribution of contributions to their contributors.
475 However, we do not want the source code to be littered with random
476 attributions "this code written by J. Random Hacker" (this is noisy and
477 distracting). In practice, the revision control system keeps a perfect
478 history of who changed what, and the CREDITS.txt file describes higher-level
479 contributions. If you commit a patch for someone else, please say "patch
480 contributed by J. Random Hacker!" in the commit message.</p>
Chris Lattnerab2b10c2007-12-29 19:56:08 +0000[diff] [blame]481
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]482<p>Overall, please do not add contributor names to the source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]483</div>
484
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]485</div>
486
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]487<!--=========================================================================-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]488<h2>
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]489 <a name="clp">Copyright, License, and Patents</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]490</h2>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]491<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]492
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]493<div>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]494<p>This section addresses the issues of copyright, license and patents for the
495 LLVM project. Currently, the University of Illinois is the LLVM copyright
496 holder and the terms of its license to LLVM users and developers is the
497 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
498 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]499
500<div class="doc_notes">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]501<p style="text-align:center;font-weight:bold">NOTE: This section deals with
502 legal matters but does not provide legal advice. We are not lawyers, please
503 seek legal counsel from an attorney.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]504</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]505
506<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]507<h3><a name="copyright">Copyright</a></h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]508<div>
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>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]531<div>
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>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]586<div>
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
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]602</div>
603
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]604<!-- *********************************************************************** -->
605<hr>
606<address>
607 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]608 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]609 <a href="http://validator.w3.org/check/referer"><img
Misha Brukmanf00ddb02008-12-11 18:23:24 +0000[diff] [blame]610 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]611 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]612 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]613 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]614 Last modified: $Date$
615</address>
616</body>
617</html>