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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
11<div class="doc_title">LLVM Developer Policy</div>
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 <li><a href="#devagree">Developer Agreements</a></li>
33 </ol></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]34</ol>
Chris Lattner2ae49dd2007-02-19 06:24:23 +0000[diff] [blame]35<div class="doc_author">Written by the LLVM Oversight Team</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]36
37<!--=========================================================================-->
Reid Spencere7bd7d62007-02-14 17:24:04 +0000[diff] [blame]38<div class="doc_section"><a name="introduction">Introduction</a></div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]39<!--=========================================================================-->
40<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]41<p>This document contains the LLVM Developer Policy which defines the project's
42 policy towards developers and their contributions. The intent of this policy
43 is to eliminate miscommunication, rework, and confusion that might arise from
44 the distributed nature of LLVM's development. By stating the policy in clear
45 terms, we hope each developer can know ahead of time what to expect when
46 making LLVM contributions.</p>
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<!--=========================================================================-->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]66<div class="doc_section"><a name="policies">Developer Policies</a></div>
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<!-- _______________________________________________________________________ -->
78<div class="doc_subsection"> <a name="informed">Stay Informed</a> </div>
79<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]80<p>Developers should stay informed by reading at least the
81 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> email
82 list. If you are doing anything more than just casual work on LLVM, it is
83 suggested that you also subscribe to the
84 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]85 list and pay attention to changes being made by others.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]86
87<p>We recommend that active developers register an email account with
88 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
89 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
90 email list to keep track of bugs and enhancements occurring in LLVM.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]91</div>
92
93<!-- _______________________________________________________________________ -->
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]94<div class="doc_subsection"> <a name="patches">Making a Patch</a></div>
95
96<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]97<p>When making a patch for review, the goal is to make it as easy for the
98 reviewer to read it as possible. As such, we recommend that you:</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]99
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]100<ol>
101 <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]102 version of LLVM. This makes it easy to apply the patch. For information
103 on how to check out SVN trunk, please see the <a
104 href="GettingStarted.html#checkout">Getting Started Guide</a>.</li>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]105
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]106 <li>Similarly, patches should be submitted soon after they are generated. Old
107 patches may not apply correctly if the underlying code changes between the
108 time the patch was created and the time it is applied.</li>
109
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]110 <li>Patches should be made with <tt>svn diff</tt>, or similar. If you use
111 a different tool, make sure it uses the <tt>diff -u</tt> format and
112 that it doesn't contain clutter which makes it hard to read.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]113
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]114 <li>If you are modifying generated files, such as the top-level
115 <tt>configure</tt> script, please separate out those changes into
116 a separate patch from the rest of your changes.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]117</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]118
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]119<p>When sending a patch to a mailing list, it is a good idea to send it as an
120 <em>attachment</em> to the message, not embedded into the text of the
121 message. This ensures that your mailer will not mangle the patch when it
122 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
123
124<p><em>For Thunderbird users:</em> Before submitting a patch, please open
125 <em>Preferences &#8594; Advanced &#8594; General &#8594; Config Editor</em>,
126 find the key <tt>mail.content_disposition_type</tt>, and set its value to
127 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
128 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
129 attachment</tt>. Apple Mail gamely displays such a file inline, making it
130 difficult to work with for reviewers using that program.</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]131</div>
132
133<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]134<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
135<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]136<p>LLVM has a code review policy. Code review is one way to increase the quality
137 of software. We generally follow these policies:</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]138
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]139<ol>
140 <li>All developers are required to have significant changes reviewed before
141 they are committed to the repository.</li>
142
143 <li>Code reviews are conducted by email, usually on the llvm-commits
144 list.</li>
145
146 <li>Code can be reviewed either before it is committed or after. We expect
147 major changes to be reviewed before being committed, but smaller changes
148 (or changes where the developer owns the component) can be reviewed after
149 commit.</li>
150
151 <li>The developer responsible for a code change is also responsible for making
152 all necessary review-related changes.</li>
153
154 <li>Code review can be an iterative process, which continues until the patch
155 is ready to be committed.</li>
156</ol>
157
158<p>Developers should participate in code reviews as both reviewers and
159 reviewees. If someone is kind enough to review your code, you should return
160 the favor for someone else. Note that anyone is welcome to review and give
161 feedback on a patch, but only people with Subversion write access can approve
162 it.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]163</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]164
165<!-- _______________________________________________________________________ -->
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]166<div class="doc_subsection"> <a name="owners">Code Owners</a></div>
167<div class="doc_text">
168
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]169<p>The LLVM Project relies on two features of its process to maintain rapid
170 development in addition to the high quality of its source base: the
171 combination of code review plus post-commit review for trusted maintainers.
172 Having both is a great way for the project to take advantage of the fact that
173 most people do the right thing most of the time, and only commit patches
174 without pre-commit review when they are confident they are right.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]175
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]176<p>The trick to this is that the project has to guarantee that all patches that
177 are committed are reviewed after they go in: you don't want everyone to
178 assume someone else will review it, allowing the patch to go unreviewed. To
179 solve this problem, we have a notion of an 'owner' for a piece of the code.
180 The sole responsibility of a code owner is to ensure that a commit to their
181 area of the code is appropriately reviewed, either by themself or by someone
182 else. The current code owners are:</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]183
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]184<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]185 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
186
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]187 <li><b>Doug Gregor</b>: Clang Basic, Lex, Parse, and Sema Libraries.</li>
188
Chris Lattnerb2030432009-09-16 05:37:13 +0000[diff] [blame]189 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
190 Windows codegen.</li>
191
Chris Lattnerf86a7782009-09-16 05:42:12 +0000[diff] [blame]192 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
193
Chris Lattner941f4cd2009-09-16 05:36:54 +0000[diff] [blame]194 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]195
196 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]197</ol>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]198
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]199<p>Note that code ownership is completely different than reviewers: anyone can
200 review a piece of code, and we welcome code review from anyone who is
201 interested. Code owners are the "last line of defense" to guarantee that all
202 patches that are committed are actually reviewed.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]203
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]204<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
205 important for the ongoing success of the project. Because people get busy,
206 interests change, and unexpected things happen, code ownership is purely
207 opt-in, and anyone can choose to resign their "title" at any time. For now,
208 we do not have an official policy on how one gets elected to be a code
209 owner.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]210</div>
211
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]212<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]213<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
214<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]215<p>Developers are required to create test cases for any bugs fixed and any new
216 features added. Some tips for getting your testcase approved:</p>
217
218<ol>
219 <li>All feature and regression test cases are added to the
220 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
221 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
222 details).</li>
223
224 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
225 language</a> unless the feature or regression being tested requires
226 another language (e.g. the bug being fixed or feature being implemented is
227 in the llvm-gcc C++ front-end, in which case it must be written in
228 C++).</li>
229
230 <li>Test cases, especially for regressions, should be reduced as much as
231 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
232 unacceptable to place an entire failing program into <tt>llvm/test</tt> as
233 this creates a <i>time-to-test</i> burden on all developers. Please keep
234 them short.</li>
235</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]236
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]237<p>Note that llvm/test is designed for regression and small feature tests
238 only. More extensive test cases (e.g., entire applications, benchmarks, etc)
239 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is
240 for coverage (correctness, performance, etc) testing, not feature or
241 regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]242</div>
243
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]244<!-- _______________________________________________________________________ -->
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]245<div class="doc_subsection"> <a name="quality">Quality</a></div>
246<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]247<p>The minimum quality standards that any change must satisfy before being
248 committed to the main development branch are:</p>
249
250<ol>
251 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
252 Standards</a>.</li>
253
254 <li>Code must compile cleanly (no errors, no warnings) on at least one
255 platform.</li>
256
257 <li>Bug fixes and new features should <a href="#testcases">include a
258 testcase</a> so we know if the fix/feature ever regresses in the
259 future.</li>
260
261 <li>Code must pass the dejagnu (<tt>llvm/test</tt>) test suite.</li>
262
263 <li>The code must not cause regressions on a reasonable subset of llvm-test,
264 where "reasonable" depends on the contributor's judgement and the scope of
265 the change (more invasive changes require more testing). A reasonable
266 subset might be something like
267 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
268</ol>
269
270<p>Additionally, the committer is responsible for addressing any problems found
271 in the future that the change is responsible for. For example:</p>
272
273<ul>
274 <li>The code should compile cleanly on all supported platforms.</li>
275
276 <li>The changes should not cause any correctness regressions in the
277 <tt>llvm-test</tt> suite and must not cause any major performance
278 regressions.</li>
279
280 <li>The change set should not cause performance or correctness regressions for
281 the LLVM tools.</li>
282
283 <li>The changes should not cause performance or correctness regressions in
284 code compiled by LLVM on all applicable targets.</li>
285
286 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
287 bugs</a> that result from your change.</li>
288</ul>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]289
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]290<p>We prefer for this to be handled before submission but understand that it
Chris Lattnerd7f10d32009-08-01 19:25:25 +0000[diff] [blame]291 isn't possible to test all of this for every submission. Our build bots and
292 nightly testing infrastructure normally finds these problems. A good rule of
293 thumb is to check the nightly testers for regressions the day after your
294 change. Build bots will directly email you if a group of commits that
295 included yours caused a failure. You are expected to check the build bot
296 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]297
298<p>Commits that violate these quality standards (e.g. are very broken) may be
299 reverted. This is necessary when the change blocks other developers from
300 making progress. The developer is welcome to re-commit the change after the
301 problem has been fixed.</p>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]302</div>
303
304<!-- _______________________________________________________________________ -->
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]305<div class="doc_subsection">
306 <a name="commitaccess">Obtaining Commit Access</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]307<div class="doc_text">
308
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]309<p>We grant commit access to contributors with a track record of submitting high
310 quality patches. If you would like commit access, please send an email to
311 <a href="mailto:sabre@nondot.org">Chris</a> with the following
312 information:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]313
314<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]315 <li>The user name you want to commit with, e.g. "hacker".</li>
316
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]317 <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]318 from, e.g. "J. Random Hacker &lt;hacker@yoyodyne.com&gt;".</li>
319
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]320 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
321 Note that you don't ever tell us what your password is, you just give it
322 to us in an encrypted form. To get this, run "htpasswd" (a utility that
323 comes with apache) in crypt mode (often enabled with "-d"), or find a web
324 page that will do it for you.</li>
325</ol>
326
327<p>Once you've been granted commit access, you should be able to check out an
328 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
329 normal anonymous URL of "http://llvm.org/...". The first time you commit
330 you'll have to type in your password. Note that you may get a warning from
331 SVN about an untrusted key, you can ignore this. To verify that your commit
332 access works, please do a test commit (e.g. change a comment or add a blank
333 line). Your first commit to a repository may require the autogenerated email
334 to be approved by a mailing list. This is normal, and will be done when
335 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]336
337<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]338
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]339<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]340 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get
341 approval, submit a <a href="#patches">patch</a> to
342 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
343 When approved you may commit it yourself.</li>
344
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]345 <li>You are allowed to commit patches without approval which you think are
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]346 obvious. This is clearly a subjective decision &mdash; we simply expect
347 you to use good judgement. Examples include: fixing build breakage,
348 reverting obviously broken patches, documentation/comment changes, any
349 other minor changes.</li>
350
351 <li>You are allowed to commit patches without approval to those portions of
352 LLVM that you have contributed or maintain (i.e., have been assigned
353 responsibility for), with the proviso that such commits must not break the
354 build. This is a "trust but verify" policy and commits of this nature are
355 reviewed after they are committed.</li>
356
357 <li>Multiple violations of these policies or a single egregious violation may
358 cause commit access to be revoked.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]359</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]360
361<p>In any case, your changes are still subject to <a href="#reviews">code
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]362 review</a> (either before or after they are committed, depending on the
363 nature of the change). You are encouraged to review other peoples' patches
364 as well, but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]365</div>
366
367<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]368<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
369<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]370<p>When a developer begins a major new project with the aim of contributing it
371 back to LLVM, s/he should inform the community with an email to
372 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
373 email list, to the extent possible. The reason for this is to:
374
375<ol>
376 <li>keep the community informed about future changes to LLVM, </li>
377
378 <li>avoid duplication of effort by preventing multiple parties working on the
379 same thing and not knowing about it, and</li>
380
381 <li>ensure that any technical issues around the proposed work are discussed
382 and resolved before any significant work is done.</li>
383</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]384
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]385<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
386 together well and are as consistent as possible. If you plan to make a major
387 change to the way LLVM works or want to add a major new extension, it is a
388 good idea to get consensus with the development community before you start
389 working on it.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]390
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]391<p>Once the design of the new feature is finalized, the work itself should be
392 done as a series of <a href="#incremental">incremental changes</a>, not as a
393 long-term development branch.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]394</div>
395
396<!-- _______________________________________________________________________ -->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]397<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]398</div>
399<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]400<p>In the LLVM project, we do all significant changes as a series of incremental
401 patches. We have a strong dislike for huge changes or long-term development
402 branches. Long-term development branches have a number of drawbacks:</p>
403
404<ol>
405 <li>Branches must have mainline merged into them periodically. If the branch
406 development and mainline development occur in the same pieces of code,
407 resolving merge conflicts can take a lot of time.</li>
408
409 <li>Other people in the community tend to ignore work on branches.</li>
410
411 <li>Huge changes (produced when a branch is merged back onto mainline) are
412 extremely difficult to <a href="#reviews">code review</a>.</li>
413
414 <li>Branches are not routinely tested by our nightly tester
415 infrastructure.</li>
416
417 <li>Changes developed as monolithic large changes often don't work until the
418 entire set of changes is done. Breaking it down into a set of smaller
419 changes increases the odds that any of the work will be committed to the
420 main repository.</li>
421</ol>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]422
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]423<p>To address these problems, LLVM uses an incremental development style and we
424 require contributors to follow this practice when making a large/invasive
425 change. Some tips:</p>
426
427<ul>
428 <li>Large/invasive changes usually have a number of secondary changes that are
429 required before the big change can be made (e.g. API cleanup, etc). These
430 sorts of changes can often be done before the major change is done,
431 independently of that work.</li>
432
433 <li>The remaining inter-related work should be decomposed into unrelated sets
434 of changes if possible. Once this is done, define the first increment and
435 get consensus on what the end goal of the change is.</li>
436
437 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
438 a planned series of changes that works towards the development goal.</li>
439
440 <li>Each change should be kept as small as possible. This simplifies your work
441 (into a logical progression), simplifies code review and reduces the
442 chance that you will get negative feedback on the change. Small increments
443 also facilitate the maintenance of a high quality code base.</li>
444
445 <li>Often, an independent precursor to a big change is to add a new API and
446 slowly migrate clients to use the new API. Each change to use the new API
447 is often "obvious" and can be committed without review. Once the new API
448 is in place and used, it is much easier to replace the underlying
449 implementation of the API. This implementation change is logically
450 separate from the API change.</li>
451</ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]452
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]453<p>If you are interested in making a large change, and this scares you, please
454 make sure to first <a href="#newwork">discuss the change/gather consensus</a>
455 then ask about the best way to go about making the change.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]456</div>
457
458<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]459<div class="doc_subsection"><a name="attribution">Attribution of
460Changes</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]461<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]462<p>We believe in correct attribution of contributions to their contributors.
463 However, we do not want the source code to be littered with random
464 attributions "this code written by J. Random Hacker" (this is noisy and
465 distracting). In practice, the revision control system keeps a perfect
466 history of who changed what, and the CREDITS.txt file describes higher-level
467 contributions. If you commit a patch for someone else, please say "patch
468 contributed by J. Random Hacker!" in the commit message.</p>
Chris Lattnerab2b10c2007-12-29 19:56:08 +0000[diff] [blame]469
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]470<p>Overall, please do not add contributor names to the source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]471</div>
472
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]473<!--=========================================================================-->
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]474<div class="doc_section">
475 <a name="clp">Copyright, License, and Patents</a>
476</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]477<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]478
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]479<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]480<p>This section addresses the issues of copyright, license and patents for the
481 LLVM project. Currently, the University of Illinois is the LLVM copyright
482 holder and the terms of its license to LLVM users and developers is the
483 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
484 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]485
486<div class="doc_notes">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]487<p style="text-align:center;font-weight:bold">NOTE: This section deals with
488 legal matters but does not provide legal advice. We are not lawyers, please
489 seek legal counsel from an attorney.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]490</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]491</div>
492
493<!-- _______________________________________________________________________ -->
494<div class="doc_subsection"><a name="copyright">Copyright</a></div>
495<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]496<p>For consistency and ease of management, the project requires the copyright
497 for all LLVM software to be held by a single copyright holder: the University
498 of Illinois (UIUC).</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]499
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]500<p>Although UIUC may eventually reassign the copyright of the software to
501 another entity (e.g. a dedicated non-profit "LLVM Organization") the intent
502 for the project is to always have a single entity hold the copyrights to LLVM
503 at any given time.</p>
Chris Lattner305915b2008-05-20 20:06:53 +0000[diff] [blame]504
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]505<p>We believe that having a single copyright holder is in the best interests of
506 all developers and users as it greatly reduces the managerial burden for any
507 kind of administrative or technical decisions about LLVM. The goal of the
508 LLVM project is to always keep the code open and <a href="#license">licensed
509 under a very liberal license</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]510</div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]511
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]512<!-- _______________________________________________________________________ -->
513<div class="doc_subsection"><a name="license">License</a></div>
514<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]515<p>We intend to keep LLVM perpetually open source and to use a liberal open
516 source license. The current license is the
517 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
Dan Gohman621a4152010-02-26 20:18:32 +0000[diff] [blame]518 Illinois/NCSA Open Source License</a>, which boils down to this:</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]519
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]520<ul>
521 <li>You can freely distribute LLVM.</li>
522
523 <li>You must retain the copyright notice if you redistribute LLVM.</li>
524
525 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in
526 an included readme file).</li>
527
528 <li>You can't use our names to promote your LLVM derived products.</li>
529
530 <li>There's no warranty on LLVM at all.</li>
531</ul>
532
533<p>We believe this fosters the widest adoption of LLVM because it <b>allows
534 commercial products to be derived from LLVM</b> with few restrictions and
535 without a requirement for making any derived works also open source (i.e.
536 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
537 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
538 if further clarification is needed.</p>
539
540<p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
541 This means that anything "linked" into llvm-gcc must itself be compatible
542 with the GPL, and must be releasable under the terms of the GPL. This
543 implies that <b>any code linked into llvm-gcc and distributed to others may
544 be subject to the viral aspects of the GPL</b> (for example, a proprietary
545 code generator linked into llvm-gcc must be made available under the GPL).
546 This is not a problem for code already distributed under a more liberal
547 license (like the UIUC license), and does not affect code generated by
548 llvm-gcc. It may be a problem if you intend to base commercial development
549 on llvm-gcc without redistributing your source code.</p>
550
551<p>We have no plans to change the license of LLVM. If you have questions or
552 comments about the license, please contact the
553 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]554</div>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]555
556<!-- _______________________________________________________________________ -->
557<div class="doc_subsection"><a name="patents">Patents</a></div>
558<div class="doc_text">
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]559<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
560 actually removed code from LLVM in the past that was found to infringe).
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]561 Having code in LLVM that infringes on patents would violate an important goal
562 of the project by making it hard or impossible to reuse the code for
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]563 arbitrary purposes (including commercial use).</p>
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]564
565<p>When contributing code, we expect contributors to notify us of any potential
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]566 for patent-related trouble with their changes. If you or your employer own
567 the rights to a patent and would like to contribute code to LLVM that relies
568 on it, we require that the copyright owner sign an agreement that allows any
569 other user of LLVM to freely use your patent. Please contact
570 the <a href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]571 details.</p>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]572</div>
573
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]574<!-- _______________________________________________________________________ -->
575<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
576<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]577<p>With regards to the LLVM copyright and licensing, developers agree to assign
578 their copyrights to UIUC for any contribution made so that the entire
579 software base can be managed by a single copyright holder. This implies that
580 any contributions can be licensed under the license that the project
581 uses.</p>
Chris Lattner64a4c112008-05-22 03:06:14 +0000[diff] [blame]582
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]583<p>When contributing code, you also affirm that you are legally entitled to
584 grant this copyright, personally or on behalf of your employer. If the code
585 belongs to some other entity, please raise this issue with the oversight
586 group before the code is committed.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]587</div>
588
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]589<!-- *********************************************************************** -->
590<hr>
591<address>
592 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]593 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]594 <a href="http://validator.w3.org/check/referer"><img
Misha Brukmanf00ddb02008-12-11 18:23:24 +0000[diff] [blame]595 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]596 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]597 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]598 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
599 Last modified: $Date$
600</address>
601</body>
602</html>