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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
110 <li>Patches should be made with this command:
111<div class="doc_code">
112<pre>
Chris Lattner87922322009-06-15 04:18:54 +0000[diff] [blame]113svn diff
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]114</pre>
115</div>
116 or with the utility <tt>utils/mkpatch</tt>, which makes it easy to read
117 the diff.</li>
118
119 <li>Patches should not include differences in generated code such as the code
120 generated by <tt>autoconf</tt> or <tt>tblgen</tt>. The
121 <tt>utils/mkpatch</tt> utility takes care of this for you.</li>
122</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]123
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]124<p>When sending a patch to a mailing list, it is a good idea to send it as an
125 <em>attachment</em> to the message, not embedded into the text of the
126 message. This ensures that your mailer will not mangle the patch when it
127 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
128
129<p><em>For Thunderbird users:</em> Before submitting a patch, please open
130 <em>Preferences &#8594; Advanced &#8594; General &#8594; Config Editor</em>,
131 find the key <tt>mail.content_disposition_type</tt>, and set its value to
132 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using
133 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition:
134 attachment</tt>. Apple Mail gamely displays such a file inline, making it
135 difficult to work with for reviewers using that program.</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]136</div>
137
138<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]139<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
140<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]141<p>LLVM has a code review policy. Code review is one way to increase the quality
142 of software. We generally follow these policies:</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]143
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]144<ol>
145 <li>All developers are required to have significant changes reviewed before
146 they are committed to the repository.</li>
147
148 <li>Code reviews are conducted by email, usually on the llvm-commits
149 list.</li>
150
151 <li>Code can be reviewed either before it is committed or after. We expect
152 major changes to be reviewed before being committed, but smaller changes
153 (or changes where the developer owns the component) can be reviewed after
154 commit.</li>
155
156 <li>The developer responsible for a code change is also responsible for making
157 all necessary review-related changes.</li>
158
159 <li>Code review can be an iterative process, which continues until the patch
160 is ready to be committed.</li>
161</ol>
162
163<p>Developers should participate in code reviews as both reviewers and
164 reviewees. If someone is kind enough to review your code, you should return
165 the favor for someone else. Note that anyone is welcome to review and give
166 feedback on a patch, but only people with Subversion write access can approve
167 it.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]168</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]169
170<!-- _______________________________________________________________________ -->
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]171<div class="doc_subsection"> <a name="owners">Code Owners</a></div>
172<div class="doc_text">
173
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]174<p>The LLVM Project relies on two features of its process to maintain rapid
175 development in addition to the high quality of its source base: the
176 combination of code review plus post-commit review for trusted maintainers.
177 Having both is a great way for the project to take advantage of the fact that
178 most people do the right thing most of the time, and only commit patches
179 without pre-commit review when they are confident they are right.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]180
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]181<p>The trick to this is that the project has to guarantee that all patches that
182 are committed are reviewed after they go in: you don't want everyone to
183 assume someone else will review it, allowing the patch to go unreviewed. To
184 solve this problem, we have a notion of an 'owner' for a piece of the code.
185 The sole responsibility of a code owner is to ensure that a commit to their
186 area of the code is appropriately reviewed, either by themself or by someone
187 else. The current code owners are:</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]188
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]189<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]190 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
191
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]192 <li><b>Doug Gregor</b>: Clang Basic, Lex, Parse, and Sema Libraries.</li>
193
Chris Lattnerb2030432009-09-16 05:37:13 +0000[diff] [blame]194 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
195 Windows codegen.</li>
196
Chris Lattnerf86a7782009-09-16 05:42:12 +0000[diff] [blame]197 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li>
198
Chris Lattner941f4cd2009-09-16 05:36:54 +0000[diff] [blame]199 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li>
Chris Lattneraf5bd672009-09-16 05:36:07 +0000[diff] [blame]200
201 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]202</ol>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]203
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]204<p>Note that code ownership is completely different than reviewers: anyone can
205 review a piece of code, and we welcome code review from anyone who is
206 interested. Code owners are the "last line of defense" to guarantee that all
207 patches that are committed are actually reviewed.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]208
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]209<p>Being a code owner is a somewhat unglamorous position, but it is incredibly
210 important for the ongoing success of the project. Because people get busy,
211 interests change, and unexpected things happen, code ownership is purely
212 opt-in, and anyone can choose to resign their "title" at any time. For now,
213 we do not have an official policy on how one gets elected to be a code
214 owner.</p>
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]215</div>
216
Chris Lattnere268a402007-12-03 19:00:47 +0000[diff] [blame]217<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]218<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
219<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]220<p>Developers are required to create test cases for any bugs fixed and any new
221 features added. Some tips for getting your testcase approved:</p>
222
223<ol>
224 <li>All feature and regression test cases are added to the
225 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
226 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
227 details).</li>
228
229 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly
230 language</a> unless the feature or regression being tested requires
231 another language (e.g. the bug being fixed or feature being implemented is
232 in the llvm-gcc C++ front-end, in which case it must be written in
233 C++).</li>
234
235 <li>Test cases, especially for regressions, should be reduced as much as
236 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is
237 unacceptable to place an entire failing program into <tt>llvm/test</tt> as
238 this creates a <i>time-to-test</i> burden on all developers. Please keep
239 them short.</li>
240</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]241
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]242<p>Note that llvm/test is designed for regression and small feature tests
243 only. More extensive test cases (e.g., entire applications, benchmarks, etc)
244 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is
245 for coverage (correctness, performance, etc) testing, not feature or
246 regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]247</div>
248
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]249<!-- _______________________________________________________________________ -->
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]250<div class="doc_subsection"> <a name="quality">Quality</a></div>
251<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]252<p>The minimum quality standards that any change must satisfy before being
253 committed to the main development branch are:</p>
254
255<ol>
256 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding
257 Standards</a>.</li>
258
259 <li>Code must compile cleanly (no errors, no warnings) on at least one
260 platform.</li>
261
262 <li>Bug fixes and new features should <a href="#testcases">include a
263 testcase</a> so we know if the fix/feature ever regresses in the
264 future.</li>
265
266 <li>Code must pass the dejagnu (<tt>llvm/test</tt>) test suite.</li>
267
268 <li>The code must not cause regressions on a reasonable subset of llvm-test,
269 where "reasonable" depends on the contributor's judgement and the scope of
270 the change (more invasive changes require more testing). A reasonable
271 subset might be something like
272 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
273</ol>
274
275<p>Additionally, the committer is responsible for addressing any problems found
276 in the future that the change is responsible for. For example:</p>
277
278<ul>
279 <li>The code should compile cleanly on all supported platforms.</li>
280
281 <li>The changes should not cause any correctness regressions in the
282 <tt>llvm-test</tt> suite and must not cause any major performance
283 regressions.</li>
284
285 <li>The change set should not cause performance or correctness regressions for
286 the LLVM tools.</li>
287
288 <li>The changes should not cause performance or correctness regressions in
289 code compiled by LLVM on all applicable targets.</li>
290
291 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
292 bugs</a> that result from your change.</li>
293</ul>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]294
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]295<p>We prefer for this to be handled before submission but understand that it
Chris Lattnerd7f10d32009-08-01 19:25:25 +0000[diff] [blame]296 isn't possible to test all of this for every submission. Our build bots and
297 nightly testing infrastructure normally finds these problems. A good rule of
298 thumb is to check the nightly testers for regressions the day after your
299 change. Build bots will directly email you if a group of commits that
300 included yours caused a failure. You are expected to check the build bot
301 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]302
303<p>Commits that violate these quality standards (e.g. are very broken) may be
304 reverted. This is necessary when the change blocks other developers from
305 making progress. The developer is welcome to re-commit the change after the
306 problem has been fixed.</p>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]307</div>
308
309<!-- _______________________________________________________________________ -->
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]310<div class="doc_subsection">
311 <a name="commitaccess">Obtaining Commit Access</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]312<div class="doc_text">
313
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]314<p>We grant commit access to contributors with a track record of submitting high
315 quality patches. If you would like commit access, please send an email to
316 <a href="mailto:sabre@nondot.org">Chris</a> with the following
317 information:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]318
319<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]320 <li>The user name you want to commit with, e.g. "hacker".</li>
321
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]322 <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]323 from, e.g. "J. Random Hacker &lt;hacker@yoyodyne.com&gt;".</li>
324
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]325 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
326 Note that you don't ever tell us what your password is, you just give it
327 to us in an encrypted form. To get this, run "htpasswd" (a utility that
328 comes with apache) in crypt mode (often enabled with "-d"), or find a web
329 page that will do it for you.</li>
330</ol>
331
332<p>Once you've been granted commit access, you should be able to check out an
333 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
334 normal anonymous URL of "http://llvm.org/...". The first time you commit
335 you'll have to type in your password. Note that you may get a warning from
336 SVN about an untrusted key, you can ignore this. To verify that your commit
337 access works, please do a test commit (e.g. change a comment or add a blank
338 line). Your first commit to a repository may require the autogenerated email
339 to be approved by a mailing list. This is normal, and will be done when
340 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]341
342<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame]343
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]344<ol>
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]345 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get
346 approval, submit a <a href="#patches">patch</a> to
347 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>.
348 When approved you may commit it yourself.</li>
349
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]350 <li>You are allowed to commit patches without approval which you think are
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]351 obvious. This is clearly a subjective decision &mdash; we simply expect
352 you to use good judgement. Examples include: fixing build breakage,
353 reverting obviously broken patches, documentation/comment changes, any
354 other minor changes.</li>
355
356 <li>You are allowed to commit patches without approval to those portions of
357 LLVM that you have contributed or maintain (i.e., have been assigned
358 responsibility for), with the proviso that such commits must not break the
359 build. This is a "trust but verify" policy and commits of this nature are
360 reviewed after they are committed.</li>
361
362 <li>Multiple violations of these policies or a single egregious violation may
363 cause commit access to be revoked.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]364</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]365
366<p>In any case, your changes are still subject to <a href="#reviews">code
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]367 review</a> (either before or after they are committed, depending on the
368 nature of the change). You are encouraged to review other peoples' patches
369 as well, but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]370</div>
371
372<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]373<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
374<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]375<p>When a developer begins a major new project with the aim of contributing it
376 back to LLVM, s/he should inform the community with an email to
377 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
378 email list, to the extent possible. The reason for this is to:
379
380<ol>
381 <li>keep the community informed about future changes to LLVM, </li>
382
383 <li>avoid duplication of effort by preventing multiple parties working on the
384 same thing and not knowing about it, and</li>
385
386 <li>ensure that any technical issues around the proposed work are discussed
387 and resolved before any significant work is done.</li>
388</ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]389
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]390<p>The design of LLVM is carefully controlled to ensure that all the pieces fit
391 together well and are as consistent as possible. If you plan to make a major
392 change to the way LLVM works or want to add a major new extension, it is a
393 good idea to get consensus with the development community before you start
394 working on it.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]395
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]396<p>Once the design of the new feature is finalized, the work itself should be
397 done as a series of <a href="#incremental">incremental changes</a>, not as a
398 long-term development branch.</p>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]399</div>
400
401<!-- _______________________________________________________________________ -->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]402<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]403</div>
404<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]405<p>In the LLVM project, we do all significant changes as a series of incremental
406 patches. We have a strong dislike for huge changes or long-term development
407 branches. Long-term development branches have a number of drawbacks:</p>
408
409<ol>
410 <li>Branches must have mainline merged into them periodically. If the branch
411 development and mainline development occur in the same pieces of code,
412 resolving merge conflicts can take a lot of time.</li>
413
414 <li>Other people in the community tend to ignore work on branches.</li>
415
416 <li>Huge changes (produced when a branch is merged back onto mainline) are
417 extremely difficult to <a href="#reviews">code review</a>.</li>
418
419 <li>Branches are not routinely tested by our nightly tester
420 infrastructure.</li>
421
422 <li>Changes developed as monolithic large changes often don't work until the
423 entire set of changes is done. Breaking it down into a set of smaller
424 changes increases the odds that any of the work will be committed to the
425 main repository.</li>
426</ol>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]427
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]428<p>To address these problems, LLVM uses an incremental development style and we
429 require contributors to follow this practice when making a large/invasive
430 change. Some tips:</p>
431
432<ul>
433 <li>Large/invasive changes usually have a number of secondary changes that are
434 required before the big change can be made (e.g. API cleanup, etc). These
435 sorts of changes can often be done before the major change is done,
436 independently of that work.</li>
437
438 <li>The remaining inter-related work should be decomposed into unrelated sets
439 of changes if possible. Once this is done, define the first increment and
440 get consensus on what the end goal of the change is.</li>
441
442 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of
443 a planned series of changes that works towards the development goal.</li>
444
445 <li>Each change should be kept as small as possible. This simplifies your work
446 (into a logical progression), simplifies code review and reduces the
447 chance that you will get negative feedback on the change. Small increments
448 also facilitate the maintenance of a high quality code base.</li>
449
450 <li>Often, an independent precursor to a big change is to add a new API and
451 slowly migrate clients to use the new API. Each change to use the new API
452 is often "obvious" and can be committed without review. Once the new API
453 is in place and used, it is much easier to replace the underlying
454 implementation of the API. This implementation change is logically
455 separate from the API change.</li>
456</ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]457
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]458<p>If you are interested in making a large change, and this scares you, please
459 make sure to first <a href="#newwork">discuss the change/gather consensus</a>
460 then ask about the best way to go about making the change.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]461</div>
462
463<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]464<div class="doc_subsection"><a name="attribution">Attribution of
465Changes</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]466<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]467<p>We believe in correct attribution of contributions to their contributors.
468 However, we do not want the source code to be littered with random
469 attributions "this code written by J. Random Hacker" (this is noisy and
470 distracting). In practice, the revision control system keeps a perfect
471 history of who changed what, and the CREDITS.txt file describes higher-level
472 contributions. If you commit a patch for someone else, please say "patch
473 contributed by J. Random Hacker!" in the commit message.</p>
Chris Lattnerab2b10c2007-12-29 19:56:08 +0000[diff] [blame]474
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]475<p>Overall, please do not add contributor names to the source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]476</div>
477
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]478<!--=========================================================================-->
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]479<div class="doc_section">
480 <a name="clp">Copyright, License, and Patents</a>
481</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]482<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]483
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]484<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]485<p>This section addresses the issues of copyright, license and patents for the
486 LLVM project. Currently, the University of Illinois is the LLVM copyright
487 holder and the terms of its license to LLVM users and developers is the
488 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
489 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]490
491<div class="doc_notes">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]492<p style="text-align:center;font-weight:bold">NOTE: This section deals with
493 legal matters but does not provide legal advice. We are not lawyers, please
494 seek legal counsel from an attorney.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]495</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]496</div>
497
498<!-- _______________________________________________________________________ -->
499<div class="doc_subsection"><a name="copyright">Copyright</a></div>
500<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]501<p>For consistency and ease of management, the project requires the copyright
502 for all LLVM software to be held by a single copyright holder: the University
503 of Illinois (UIUC).</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]504
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]505<p>Although UIUC may eventually reassign the copyright of the software to
506 another entity (e.g. a dedicated non-profit "LLVM Organization") the intent
507 for the project is to always have a single entity hold the copyrights to LLVM
508 at any given time.</p>
Chris Lattner305915b2008-05-20 20:06:53 +0000[diff] [blame]509
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]510<p>We believe that having a single copyright holder is in the best interests of
511 all developers and users as it greatly reduces the managerial burden for any
512 kind of administrative or technical decisions about LLVM. The goal of the
513 LLVM project is to always keep the code open and <a href="#license">licensed
514 under a very liberal license</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]515</div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]516
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]517<!-- _______________________________________________________________________ -->
518<div class="doc_subsection"><a name="license">License</a></div>
519<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]520<p>We intend to keep LLVM perpetually open source and to use a liberal open
521 source license. The current license is the
522 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
523 llinois/NCSA Open Source License</a>, which boils down to this:</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]524
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]525<ul>
526 <li>You can freely distribute LLVM.</li>
527
528 <li>You must retain the copyright notice if you redistribute LLVM.</li>
529
530 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in
531 an included readme file).</li>
532
533 <li>You can't use our names to promote your LLVM derived products.</li>
534
535 <li>There's no warranty on LLVM at all.</li>
536</ul>
537
538<p>We believe this fosters the widest adoption of LLVM because it <b>allows
539 commercial products to be derived from LLVM</b> with few restrictions and
540 without a requirement for making any derived works also open source (i.e.
541 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
542 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
543 if further clarification is needed.</p>
544
545<p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
546 This means that anything "linked" into llvm-gcc must itself be compatible
547 with the GPL, and must be releasable under the terms of the GPL. This
548 implies that <b>any code linked into llvm-gcc and distributed to others may
549 be subject to the viral aspects of the GPL</b> (for example, a proprietary
550 code generator linked into llvm-gcc must be made available under the GPL).
551 This is not a problem for code already distributed under a more liberal
552 license (like the UIUC license), and does not affect code generated by
553 llvm-gcc. It may be a problem if you intend to base commercial development
554 on llvm-gcc without redistributing your source code.</p>
555
556<p>We have no plans to change the license of LLVM. If you have questions or
557 comments about the license, please contact the
558 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]559</div>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]560
561<!-- _______________________________________________________________________ -->
562<div class="doc_subsection"><a name="patents">Patents</a></div>
563<div class="doc_text">
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]564<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
565 actually removed code from LLVM in the past that was found to infringe).
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]566 Having code in LLVM that infringes on patents would violate an important goal
567 of the project by making it hard or impossible to reuse the code for
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]568 arbitrary purposes (including commercial use).</p>
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]569
570<p>When contributing code, we expect contributors to notify us of any potential
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]571 for patent-related trouble with their changes. If you or your employer own
572 the rights to a patent and would like to contribute code to LLVM that relies
573 on it, we require that the copyright owner sign an agreement that allows any
574 other user of LLVM to freely use your patent. Please contact
575 the <a href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]576 details.</p>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]577</div>
578
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]579<!-- _______________________________________________________________________ -->
580<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
581<div class="doc_text">
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]582<p>With regards to the LLVM copyright and licensing, developers agree to assign
583 their copyrights to UIUC for any contribution made so that the entire
584 software base can be managed by a single copyright holder. This implies that
585 any contributions can be licensed under the license that the project
586 uses.</p>
Chris Lattner64a4c112008-05-22 03:06:14 +0000[diff] [blame]587
Bill Wendling78c8fce2009-04-05 12:37:44 +0000[diff] [blame]588<p>When contributing code, you also affirm that you are legally entitled to
589 grant this copyright, personally or on behalf of your employer. If the code
590 belongs to some other entity, please raise this issue with the oversight
591 group before the code is committed.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]592</div>
593
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]594<!-- *********************************************************************** -->
595<hr>
596<address>
597 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]598 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]599 <a href="http://validator.w3.org/check/referer"><img
Misha Brukmanf00ddb02008-12-11 18:23:24 +0000[diff] [blame]600 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]601 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]602 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]603 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
604 Last modified: $Date$
605</address>
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