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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
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]46 making LLVM contributions. This policy covers all llvm.org subprojects,
47 including Clang, LLDB, etc.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]48<p>This policy is also designed to accomplish the following objectives:</p>
49
50<ol>
51 <li>Attract both users and developers to the LLVM project.</li>
52
53 <li>Make life as simple and easy for contributors as possible.</li>
54
55 <li>Keep the top of Subversion trees as stable as possible.</li>
56</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]57
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]58<p>This policy is aimed at frequent contributors to LLVM. People interested in
59 contributing one-off patches can do so in an informal way by sending them to
60 the
61 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits
62 mailing list</a> and engaging another developer to see it through the
63 process.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]64</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]65
66<!--=========================================================================-->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]67<div class="doc_section"><a name="policies">Developer Policies</a></div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]68<!--=========================================================================-->
69<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]70<p>This section contains policies that pertain to frequent LLVM developers. We
71 always welcome <a href="#patches">one-off patches</a> from people who do not
72 routinely contribute to LLVM, but we expect more from frequent contributors
73 to keep the system as efficient as possible for everyone. Frequent LLVM
74 contributors are expected to meet the following requirements in order for
75 LLVM to maintain a high standard of quality.<p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]76</div>
77
78<!-- _______________________________________________________________________ -->
79<div class="doc_subsection"> <a name="informed">Stay Informed</a> </div>
80<div class="doc_text">
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]81<p>Developers should stay informed by reading at least the "dev" mailing list
82 for the projects you are interested in, such as
83 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> for
84 LLVM, <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
85 for Clang, or <a
86 href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev">lldb-dev</a>
87 for LLDB. If you are doing anything more than just casual work on LLVM, it
88 is suggested that you also subscribe to the "commits" mailing list for the
89 subproject you're interested in, such as
90 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>,
91 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>,
92 or <a href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits">lldb-commits</a>.
93 Reading the "commits" list and paying attention to changes being made by
94 others is a good way to see what other people are interested in and watching
95 the flow of the project as a whole.</p>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]96
97<p>We recommend that active developers register an email account with
98 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
99 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]100 email list to keep track of bugs and enhancements occurring in LLVM. We
101 really appreciate people who are proactive at catching incoming bugs in their
102 components and dealing with them promptly.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]103</div>
104
105<!-- _______________________________________________________________________ -->
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]106<div class="doc_subsection"> <a name="patches">Making a Patch</a></div>
107
108<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]109<p>When making a patch for review, the goal is to make it as easy for the
110 reviewer to read it as possible. As such, we recommend that you:</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]111
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]112<ol>
113 <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]114 version of LLVM. This makes it easy to apply the patch. For information
115 on how to check out SVN trunk, please see the <a
116 href="GettingStarted.html#checkout">Getting Started Guide</a>.</li>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]117
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]118 <li>Similarly, patches should be submitted soon after they are generated. Old
119 patches may not apply correctly if the underlying code changes between the
120 time the patch was created and the time it is applied.</li>
121
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]122 <li>Patches should be made with <tt>svn diff</tt>, or similar. If you use
123 a different tool, make sure it uses the <tt>diff -u</tt> format and
124 that it doesn't contain clutter which makes it hard to read.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]125
Dan Gohmanc1076ea2010-08-04 16:07:22 +0000[diff] [blame]126 <li>If you are modifying generated files, such as the top-level
127 <tt>configure</tt> script, please separate out those changes into
128 a separate patch from the rest of your changes.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]129</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]130
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]131<p>When sending a patch to a mailing list, it is a good idea to send it as an
132 <em>attachment</em> to the message, not embedded into the text of the
133 message. This ensures that your mailer will not mangle the patch when it
134 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
135
136<p><em>For Thunderbird users:</em> Before submitting a patch, please open
137 <em>Preferences &#8594; Advanced &#8594; General &#8594; Config Editor</em>,
138 find the key <tt>mail.content_disposition_type</tt>, and set its value to
139 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
140 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
141 attachment</tt>. Apple Mail gamely displays such a file inline, making it
142 difficult to work with for reviewers using that program.</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]143</div>
144
145<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]146<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
147<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]148<p>LLVM has a code review policy. Code review is one way to increase the quality
149 of software. We generally follow these policies:</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]150
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]151<ol>
152 <li>All developers are required to have significant changes reviewed before
153 they are committed to the repository.</li>
154
155 <li>Code reviews are conducted by email, usually on the llvm-commits
156 list.</li>
157
158 <li>Code can be reviewed either before it is committed or after. We expect
159 major changes to be reviewed before being committed, but smaller changes
160 (or changes where the developer owns the component) can be reviewed after
161 commit.</li>
162
163 <li>The developer responsible for a code change is also responsible for making
164 all necessary review-related changes.</li>
165
166 <li>Code review can be an iterative process, which continues until the patch
167 is ready to be committed.</li>
168</ol>
169
170<p>Developers should participate in code reviews as both reviewers and
171 reviewees. If someone is kind enough to review your code, you should return
172 the favor for someone else. Note that anyone is welcome to review and give
173 feedback on a patch, but only people with Subversion write access can approve
174 it.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]175</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]176
177<!-- _______________________________________________________________________ -->
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]178<div class="doc_subsection"> <a name="owners">Code Owners</a></div>
179<div class="doc_text">
180
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]181<p>The LLVM Project relies on two features of its process to maintain rapid
182 development in addition to the high quality of its source base: the
183 combination of code review plus post-commit review for trusted maintainers.
184 Having both is a great way for the project to take advantage of the fact that
185 most people do the right thing most of the time, and only commit patches
186 without pre-commit review when they are confident they are right.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]187
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]188<p>The trick to this is that the project has to guarantee that all patches that
189 are committed are reviewed after they go in: you don't want everyone to
190 assume someone else will review it, allowing the patch to go unreviewed. To
191 solve this problem, we have a notion of an 'owner' for a piece of the code.
192 The sole responsibility of a code owner is to ensure that a commit to their
193 area of the code is appropriately reviewed, either by themself or by someone
194 else. The current code owners are:</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]195
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]196<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]197 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
198
Chris Lattner5ce89812010-09-23 17:27:54 +0000[diff] [blame^]199 <li><b>Greg Clayton</b>: LLDB.</li>
200
201 <li><b>Doug Gregor</b>: Clang Frontend Libraries.</li>
202
203 <li><b>Howard Hinnant</b>: libc++.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]204
Chris Lattnerb2030432009-09-16 05:37:13 +0000[diff] [blame]205 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
206 Windows codegen.</li>
207
Chris Lattnerf86a7782009-09-16 05:42:12 +0000[diff] [blame]208 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
209
Chris Lattner941f4cd2009-09-16 05:36:54 +0000[diff] [blame]210 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]211
212 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]213</ol>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]214
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]215<p>Note that code ownership is completely different than reviewers: anyone can
216 review a piece of code, and we welcome code review from anyone who is
217 interested. Code owners are the "last line of defense" to guarantee that all
218 patches that are committed are actually reviewed.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]219
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]220<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
221 important for the ongoing success of the project. Because people get busy,
222 interests change, and unexpected things happen, code ownership is purely
223 opt-in, and anyone can choose to resign their "title" at any time. For now,
224 we do not have an official policy on how one gets elected to be a code
225 owner.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]226</div>
227
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]228<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]229<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
230<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]231<p>Developers are required to create test cases for any bugs fixed and any new
232 features added. Some tips for getting your testcase approved:</p>
233
234<ol>
235 <li>All feature and regression test cases are added to the
236 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
237 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
238 details).</li>
239
240 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
241 language</a> unless the feature or regression being tested requires
242 another language (e.g. the bug being fixed or feature being implemented is
243 in the llvm-gcc C++ front-end, in which case it must be written in
244 C++).</li>
245
246 <li>Test cases, especially for regressions, should be reduced as much as
247 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
248 unacceptable to place an entire failing program into <tt>llvm/test</tt> as
249 this creates a <i>time-to-test</i> burden on all developers. Please keep
250 them short.</li>
251</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]252
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]253<p>Note that llvm/test and clang/test are designed for regression and small
254 feature tests only. More extensive test cases (e.g., entire applications,
255 benchmarks, etc)
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]256 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is
257 for coverage (correctness, performance, etc) testing, not feature or
258 regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]259</div>
260
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]261<!-- _______________________________________________________________________ -->
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]262<div class="doc_subsection"> <a name="quality">Quality</a></div>
263<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]264<p>The minimum quality standards that any change must satisfy before being
265 committed to the main development branch are:</p>
266
267<ol>
268 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
269 Standards</a>.</li>
270
271 <li>Code must compile cleanly (no errors, no warnings) on at least one
272 platform.</li>
273
274 <li>Bug fixes and new features should <a href="#testcases">include a
275 testcase</a> so we know if the fix/feature ever regresses in the
276 future.</li>
277
Chris Lattnerb742ff02010-09-02 00:09:17 +0000[diff] [blame]278 <li>Code must pass the <tt>llvm/test</tt> test suite.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]279
280 <li>The code must not cause regressions on a reasonable subset of llvm-test,
281 where "reasonable" depends on the contributor's judgement and the scope of
282 the change (more invasive changes require more testing). A reasonable
283 subset might be something like
284 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
285</ol>
286
287<p>Additionally, the committer is responsible for addressing any problems found
288 in the future that the change is responsible for. For example:</p>
289
290<ul>
291 <li>The code should compile cleanly on all supported platforms.</li>
292
293 <li>The changes should not cause any correctness regressions in the
294 <tt>llvm-test</tt> suite and must not cause any major performance
295 regressions.</li>
296
297 <li>The change set should not cause performance or correctness regressions for
298 the LLVM tools.</li>
299
300 <li>The changes should not cause performance or correctness regressions in
301 code compiled by LLVM on all applicable targets.</li>
302
303 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
304 bugs</a> that result from your change.</li>
305</ul>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]306
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]307<p>We prefer for this to be handled before submission but understand that it
Chris Lattnerd7f10d32009-08-01 19:25:25 +0000[diff] [blame]308 isn't possible to test all of this for every submission. Our build bots and
309 nightly testing infrastructure normally finds these problems. A good rule of
310 thumb is to check the nightly testers for regressions the day after your
311 change. Build bots will directly email you if a group of commits that
312 included yours caused a failure. You are expected to check the build bot
313 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]314
315<p>Commits that violate these quality standards (e.g. are very broken) may be
316 reverted. This is necessary when the change blocks other developers from
317 making progress. The developer is welcome to re-commit the change after the
318 problem has been fixed.</p>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]319</div>
320
321<!-- _______________________________________________________________________ -->
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]322<div class="doc_subsection">
323 <a name="commitaccess">Obtaining Commit Access</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]324<div class="doc_text">
325
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]326<p>We grant commit access to contributors with a track record of submitting high
327 quality patches. If you would like commit access, please send an email to
328 <a href="mailto:sabre@nondot.org">Chris</a> with the following
329 information:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]330
331<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]332 <li>The user name you want to commit with, e.g. "hacker".</li>
333
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]334 <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]335 from, e.g. "J. Random Hacker &lt;hacker@yoyodyne.com&gt;".</li>
336
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]337 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
338 Note that you don't ever tell us what your password is, you just give it
339 to us in an encrypted form. To get this, run "htpasswd" (a utility that
340 comes with apache) in crypt mode (often enabled with "-d"), or find a web
341 page that will do it for you.</li>
342</ol>
343
344<p>Once you've been granted commit access, you should be able to check out an
345 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
346 normal anonymous URL of "http://llvm.org/...". The first time you commit
347 you'll have to type in your password. Note that you may get a warning from
348 SVN about an untrusted key, you can ignore this. To verify that your commit
349 access works, please do a test commit (e.g. change a comment or add a blank
350 line). Your first commit to a repository may require the autogenerated email
351 to be approved by a mailing list. This is normal, and will be done when
352 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]353
354<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]355
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]356<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]357 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get
358 approval, submit a <a href="#patches">patch</a> to
359 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
360 When approved you may commit it yourself.</li>
361
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]362 <li>You are allowed to commit patches without approval which you think are
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]363 obvious. This is clearly a subjective decision &mdash; we simply expect
364 you to use good judgement. Examples include: fixing build breakage,
365 reverting obviously broken patches, documentation/comment changes, any
366 other minor changes.</li>
367
368 <li>You are allowed to commit patches without approval to those portions of
369 LLVM that you have contributed or maintain (i.e., have been assigned
370 responsibility for), with the proviso that such commits must not break the
371 build. This is a "trust but verify" policy and commits of this nature are
372 reviewed after they are committed.</li>
373
374 <li>Multiple violations of these policies or a single egregious violation may
375 cause commit access to be revoked.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]376</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]377
378<p>In any case, your changes are still subject to <a href="#reviews">code
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]379 review</a> (either before or after they are committed, depending on the
380 nature of the change). You are encouraged to review other peoples' patches
381 as well, but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]382</div>
383
384<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]385<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
386<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]387<p>When a developer begins a major new project with the aim of contributing it
388 back to LLVM, s/he should inform the community with an email to
389 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
390 email list, to the extent possible. The reason for this is to:
391
392<ol>
393 <li>keep the community informed about future changes to LLVM, </li>
394
395 <li>avoid duplication of effort by preventing multiple parties working on the
396 same thing and not knowing about it, and</li>
397
398 <li>ensure that any technical issues around the proposed work are discussed
399 and resolved before any significant work is done.</li>
400</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]401
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]402<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
403 together well and are as consistent as possible. If you plan to make a major
404 change to the way LLVM works or want to add a major new extension, it is a
405 good idea to get consensus with the development community before you start
406 working on it.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]407
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]408<p>Once the design of the new feature is finalized, the work itself should be
409 done as a series of <a href="#incremental">incremental changes</a>, not as a
410 long-term development branch.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]411</div>
412
413<!-- _______________________________________________________________________ -->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]414<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]415</div>
416<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]417<p>In the LLVM project, we do all significant changes as a series of incremental
418 patches. We have a strong dislike for huge changes or long-term development
419 branches. Long-term development branches have a number of drawbacks:</p>
420
421<ol>
422 <li>Branches must have mainline merged into them periodically. If the branch
423 development and mainline development occur in the same pieces of code,
424 resolving merge conflicts can take a lot of time.</li>
425
426 <li>Other people in the community tend to ignore work on branches.</li>
427
428 <li>Huge changes (produced when a branch is merged back onto mainline) are
429 extremely difficult to <a href="#reviews">code review</a>.</li>
430
431 <li>Branches are not routinely tested by our nightly tester
432 infrastructure.</li>
433
434 <li>Changes developed as monolithic large changes often don't work until the
435 entire set of changes is done. Breaking it down into a set of smaller
436 changes increases the odds that any of the work will be committed to the
437 main repository.</li>
438</ol>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]439
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]440<p>To address these problems, LLVM uses an incremental development style and we
441 require contributors to follow this practice when making a large/invasive
442 change. Some tips:</p>
443
444<ul>
445 <li>Large/invasive changes usually have a number of secondary changes that are
446 required before the big change can be made (e.g. API cleanup, etc). These
447 sorts of changes can often be done before the major change is done,
448 independently of that work.</li>
449
450 <li>The remaining inter-related work should be decomposed into unrelated sets
451 of changes if possible. Once this is done, define the first increment and
452 get consensus on what the end goal of the change is.</li>
453
454 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
455 a planned series of changes that works towards the development goal.</li>
456
457 <li>Each change should be kept as small as possible. This simplifies your work
458 (into a logical progression), simplifies code review and reduces the
459 chance that you will get negative feedback on the change. Small increments
460 also facilitate the maintenance of a high quality code base.</li>
461
462 <li>Often, an independent precursor to a big change is to add a new API and
463 slowly migrate clients to use the new API. Each change to use the new API
464 is often "obvious" and can be committed without review. Once the new API
465 is in place and used, it is much easier to replace the underlying
466 implementation of the API. This implementation change is logically
467 separate from the API change.</li>
468</ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]469
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]470<p>If you are interested in making a large change, and this scares you, please
471 make sure to first <a href="#newwork">discuss the change/gather consensus</a>
472 then ask about the best way to go about making the change.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]473</div>
474
475<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]476<div class="doc_subsection"><a name="attribution">Attribution of
477Changes</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]478<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]479<p>We believe in correct attribution of contributions to their contributors.
480 However, we do not want the source code to be littered with random
481 attributions "this code written by J. Random Hacker" (this is noisy and
482 distracting). In practice, the revision control system keeps a perfect
483 history of who changed what, and the CREDITS.txt file describes higher-level
484 contributions. If you commit a patch for someone else, please say "patch
485 contributed by J. Random Hacker!" in the commit message.</p>
Chris Lattnerab2b10c2007-12-29 19:56:08 +0000[diff] [blame]486
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]487<p>Overall, please do not add contributor names to the source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]488</div>
489
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]490<!--=========================================================================-->
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]491<div class="doc_section">
492 <a name="clp">Copyright, License, and Patents</a>
493</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]494<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]495
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]496<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]497<p>This section addresses the issues of copyright, license and patents for the
498 LLVM project. Currently, the University of Illinois is the LLVM copyright
499 holder and the terms of its license to LLVM users and developers is the
500 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
501 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]502
503<div class="doc_notes">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]504<p style="text-align:center;font-weight:bold">NOTE: This section deals with
505 legal matters but does not provide legal advice. We are not lawyers, please
506 seek legal counsel from an attorney.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]507</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]508</div>
509
510<!-- _______________________________________________________________________ -->
511<div class="doc_subsection"><a name="copyright">Copyright</a></div>
512<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]513<p>For consistency and ease of management, the project requires the copyright
514 for all LLVM software to be held by a single copyright holder: the University
515 of Illinois (UIUC).</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]516
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]517<p>Although UIUC may eventually reassign the copyright of the software to
518 another entity (e.g. a dedicated non-profit "LLVM Organization") the intent
519 for the project is to always have a single entity hold the copyrights to LLVM
520 at any given time.</p>
Chris Lattner305915b2008-05-20 20:06:53 +0000[diff] [blame]521
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]522<p>We believe that having a single copyright holder is in the best interests of
523 all developers and users as it greatly reduces the managerial burden for any
524 kind of administrative or technical decisions about LLVM. The goal of the
525 LLVM project is to always keep the code open and <a href="#license">licensed
526 under a very liberal license</a>.</p>
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<!-- _______________________________________________________________________ -->
530<div class="doc_subsection"><a name="license">License</a></div>
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
533 source license. The current license is the
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>
539
540 <li>You must retain the copyright notice if you redistribute LLVM.</li>
541
542 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in
543 an included readme file).</li>
544
545 <li>You can't use our names to promote your LLVM derived products.</li>
546
547 <li>There's no warranty on LLVM at all.</li>
548</ul>
549
550<p>We believe this fosters the widest adoption of LLVM because it <b>allows
551 commercial products to be derived from LLVM</b> with few restrictions and
552 without a requirement for making any derived works also open source (i.e.
553 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
554 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
555 if further clarification is needed.</p>
556
557<p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
558 This means that anything "linked" into llvm-gcc must itself be compatible
559 with the GPL, and must be releasable under the terms of the GPL. This
560 implies that <b>any code linked into llvm-gcc and distributed to others may
561 be subject to the viral aspects of the GPL</b> (for example, a proprietary
562 code generator linked into llvm-gcc must be made available under the GPL).
563 This is not a problem for code already distributed under a more liberal
564 license (like the UIUC license), and does not affect code generated by
565 llvm-gcc. It may be a problem if you intend to base commercial development
566 on llvm-gcc without redistributing your source code.</p>
567
568<p>We have no plans to change the license of LLVM. If you have questions or
569 comments about the license, please contact the
570 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]571</div>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]572
573<!-- _______________________________________________________________________ -->
574<div class="doc_subsection"><a name="patents">Patents</a></div>
575<div class="doc_text">
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]576<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
577 actually removed code from LLVM in the past that was found to infringe).
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]578 Having code in LLVM that infringes on patents would violate an important goal
579 of the project by making it hard or impossible to reuse the code for
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]580 arbitrary purposes (including commercial use).</p>
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]581
582<p>When contributing code, we expect contributors to notify us of any potential
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]583 for patent-related trouble with their changes. If you or your employer own
584 the rights to a patent and would like to contribute code to LLVM that relies
585 on it, we require that the copyright owner sign an agreement that allows any
586 other user of LLVM to freely use your patent. Please contact
587 the <a href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]588 details.</p>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]589</div>
590
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]591<!-- _______________________________________________________________________ -->
592<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
593<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]594<p>With regards to the LLVM copyright and licensing, developers agree to assign
595 their copyrights to UIUC for any contribution made so that the entire
596 software base can be managed by a single copyright holder. This implies that
597 any contributions can be licensed under the license that the project
598 uses.</p>
Chris Lattner64a4c112008-05-22 03:06:14 +0000[diff] [blame]599
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]600<p>When contributing code, you also affirm that you are legally entitled to
601 grant this copyright, personally or on behalf of your employer. If the code
602 belongs to some other entity, please raise this issue with the oversight
603 group before the code is committed.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]604</div>
605
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]606<!-- *********************************************************************** -->
607<hr>
608<address>
609 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]610 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]611 <a href="http://validator.w3.org/check/referer"><img
Misha Brukmanf00ddb02008-12-11 18:23:24 +0000[diff] [blame]612 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]613 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]614 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]615 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
616 Last modified: $Date$
617</address>
618</body>
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