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5 <title>LLVM Developer Policy</title>
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7</head>
8<body>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]9
10<div class="doc_title">LLVM Developer Policy</div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]11<ol>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]12 <li><a href="#introduction">Introduction</a></li>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]13 <li><a href="#policies">Developer Policies</a>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]14 <ol>
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]15 <li><a href="#informed">Stay Informed</a></li>
16 <li><a href="#patches">Making a Patch</a></li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]17 <li><a href="#reviews">Code Reviews</a></li>
Chris Lattnerb39e02b2007-12-03 19:00:47 +0000[diff] [blame]18 <li><a href="#owners">Code Owners</a></li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]19 <li><a href="#testcases">Test Cases</a></li>
Chris Lattner10f15142007-02-19 05:49:11 +0000[diff] [blame]20 <li><a href="#quality">Quality</a></li>
21 <li><a href="#commitaccess">Obtaining Commit Access</a></li>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]22 <li><a href="#newwork">Making a Major Change</a></li>
23 <li><a href="#incremental">Incremental Development</a></li>
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]24 <li><a href="#attribution">Attribution of Changes</a></li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]25 </ol></li>
Chris Lattner83967802007-02-19 06:19:16 +0000[diff] [blame]26 <li><a href="#clp">Copyright, License, and Patents</a>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]27 <ol>
28 <li><a href="#copyright">Copyright</a></li>
29 <li><a href="#license">License</a></li>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]30 <li><a href="#patents">Patents</a></li>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]31 <li><a href="#devagree">Developer Agreements</a></li>
32 </ol></li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]33</ol>
Chris Lattnerf54ba982007-02-19 06:24:23 +0000[diff] [blame]34<div class="doc_author">Written by the LLVM Oversight Team</div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]35
36<!--=========================================================================-->
Reid Spencer1e7306d2007-02-14 17:24:04 +0000[diff] [blame]37<div class="doc_section"><a name="introduction">Introduction</a></div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]38<!--=========================================================================-->
39<div class="doc_text">
40 <p>This document contains the LLVM Developer Policy which defines the
Reid Spencer6e0c66d2007-02-13 17:04:09 +0000[diff] [blame]41 project's policy towards developers and their contributions. The intent of
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]42 this policy is to eliminate mis-communication, rework, and confusion that
43 might arise from the distributed nature of LLVM's development. By stating
44 the policy in clear terms, we hope each developer can know ahead of time
45 what to expect when making LLVM contributions.</p>
Reid Spencer05cc0992007-02-14 22:55:40 +0000[diff] [blame]46 <p>This policy is also designed to accomplish the following objectives:</p>
47 <ol>
48 <li>Attract both users and developers to the LLVM project.</li>
49 <li>Make life as simple and easy for contributors as possible.</li>
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]50 <li>Keep the top of Subversion trees as stable as possible.</li>
Reid Spencer05cc0992007-02-14 22:55:40 +0000[diff] [blame]51 </ol>
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]52
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]53 <p>This policy is aimed at frequent contributors to LLVM. People interested in
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]54 contributing one-off patches can do so in an informal way by sending them to
55 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
56 llvm-commits mailing list</a> and engaging another developer to see it through
57 the process.</p>
58
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]59</div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]60
61<!--=========================================================================-->
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]62<div class="doc_section"><a name="policies">Developer Policies</a></div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]63<!--=========================================================================-->
64<div class="doc_text">
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]65 <p>This section contains policies that pertain to frequent LLVM
Reid Spencer68812c72007-02-19 17:38:38 +0000[diff] [blame]66 developers. We always welcome <a href="#patches">one-off patches</a> from
67 people who do not routinely contribute to LLVM, but we expect more from
68 frequent contributors to keep the system as efficient as possible for
69 everyone.
70 Frequent LLVM contributors are expected to meet the following requirements in
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]71 order for LLVM to maintain a high standard of quality.<p>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]72</div>
73
74<!-- _______________________________________________________________________ -->
75<div class="doc_subsection"> <a name="informed">Stay Informed</a> </div>
76<div class="doc_text">
77 <p>Developers should stay informed by reading at least the
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]78 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
79 email list. If you are doing anything more than just casual work on LLVM,
80 it is suggested that you also subscribe to the
81 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
82 list and pay attention to changes being made by others.</p>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]83 <p>We recommend that active developers register an email account with
84 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
85 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
86 email list to keep track of bugs and enhancements occurring in LLVM.</p>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]87</div>
88
89<!-- _______________________________________________________________________ -->
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]90<div class="doc_subsection"> <a name="patches">Making a Patch</a></div>
91
92<div class="doc_text">
93
94<p>When making a patch for review, the goal is to make it as easy for the
95 reviewer to read it as possible. As such, we recommend that you:</p>
96 <ol>
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]97 <li>Make your patch against the Subversion trunk, not a branch, and not an
98 old version of LLVM. This makes it easy to apply the patch.</li>
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]99
100 <li>Similarly, patches should be submitted soon after they are generated.
101 Old patches may not apply correctly if the underlying code changes between
102 the time the patch was created and the time it is applied.</li>
103
104 <li>Patches should be made with this command:
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]105 <pre>svn diff -x -u</pre>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]106 or with the utility <tt>utils/mkpatch</tt>, which makes it easy to read the
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]107 diff.</li>
108
109 <li>Patches should not include differences in generated code such as the
110 code generated by <tt>flex</tt>, <tt>bison</tt> or <tt>tblgen</tt>. The
111 <tt>utils/mkpatch</tt> utility takes care of this for you.</li>
112
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]113 </ol>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]114
115 <p>When sending a patch to a mailing list, it is a good idea to send it as an
116 <em>attachment</em> to the message, not embedded into the text of the
117 message. This ensures that your mailer will not mangle the patch when it
118 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]119</div>
120
121<!-- _______________________________________________________________________ -->
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]122<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
123<div class="doc_text">
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]124 <p>LLVM has a code review policy. Code review is one way to increase the
125 quality of software. We generally follow these policies:</p>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]126 <ol>
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]127 <li>All developers are required to have significant changes reviewed
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]128 before they are committed to the repository.</li>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]129 <li>Code reviews are conducted by email, usually on the llvm-commits
130 list.</li>
131 <li>Code can be reviewed either before it is committed or after. We expect
132 major changes to be reviewed before being committed, but smaller
133 changes (or changes where the developer owns the component) can be
134 reviewed after commit.</li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]135 <li>The developer responsible for a code change is also responsible for
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]136 making all necessary review-related changes.</li>
Reid Spencer68812c72007-02-19 17:38:38 +0000[diff] [blame]137 <li>Code review can be an iterative process, which continues until the patch
Chris Lattnera3338192007-02-19 05:57:29 +0000[diff] [blame]138 is ready to be committed.</li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]139 </ol>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]140
141 <p>Developers should participate in code reviews as both reviewers and
Reid Spencer68812c72007-02-19 17:38:38 +0000[diff] [blame]142 reviewees. If someone is kind enough to review your code, you should
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]143 return the favor for someone else. Note that anyone is welcome to review
Reid Spencerc7f87f22007-07-09 08:04:31 +0000[diff] [blame]144 and give feedback on a patch, but only people with Subversion write access
145 can approve it.</p>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]146
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]147</div>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]148
149<!-- _______________________________________________________________________ -->
Chris Lattnerb39e02b2007-12-03 19:00:47 +0000[diff] [blame]150<div class="doc_subsection"> <a name="owners">Code Owners</a></div>
151<div class="doc_text">
152
153 <p>The LLVM Project relies on two features of its process to maintain rapid
154 development in addition to the high quality of its source base: the
155 combination of code review plus post-commit review for trusted maintainers.
156 Having both is a great way for the project to take advantage of the fact
157 that most people do the right thing most of the time, and only commit
158 patches without pre-commit review when they are confident they are
159 right.</p>
160
161 <p>The trick to this is that the project has to guarantee that all patches
162 that are committed are reviewed after they go in: you don't want everyone
163 to assume someone else will review it, allowing the patch to go unreviewed.
164 To solve this problem, we have a notion of an 'owner' for a piece of the
165 code. The sole responsibility of a code owner is to ensure that a commit
166 to their area of the code is appropriately reviewed, either by themself or
167 by someone else. The current code owners are:</p>
168
169 <ol>
170 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and
171 Windows codegen.</li>
172 <li><b>Duncan Sands</b>: llvm-gcc 4.2.</li>
173 <li><b>Evan Cheng</b>: Code generator and all targets.</li>
174 <li><b>Chris Lattner</b>: Everything else.</li>
175 </ol>
176
177 <p>Note that code ownership is completely different than reviewers: anyone can
178 review a piece of code, and we welcome code review from anyone who is
179 interested. Code owners are the "last line of defense" to guarantee that
180 all patches that are committed are actually reviewed.</p>
181
182 <p>Being a code owner is a somewhat unglamorous position, but it is incredibly
183 important for the ongoing success of the project. Because people get busy,
184 interests change, and unexpected things happen, code ownership is purely
185 opt-in, and anyone can choose to resign their "title" at any time. For now,
186 we do not have an official policy on how one gets elected to be a code
187 owner.
188 </p>
189
190</div>
191
192
193<!-- _______________________________________________________________________ -->
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]194<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
195<div class="doc_text">
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]196 <p>Developers are required to create test cases for any bugs fixed and any new
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]197 features added. Some tips for getting your testcase approved:</p>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]198 <ol>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]199 <li>All feature and regression test cases are added to the
Reid Spencer767abe42007-02-13 09:20:14 +0000[diff] [blame]200 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]201 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
Reid Spencer102f05a2007-02-13 20:57:57 +0000[diff] [blame]202 details).</li>
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]203 <li>Test cases should be written in
204 <a href="LangRef.html">LLVM assembly language</a> unless the
Reid Spencerc4a1f8b2007-02-14 07:57:48 +0000[diff] [blame]205 feature or regression being tested requires another language (e.g. the
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]206 bug being fixed or feature being implemented is in the llvm-gcc C++
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]207 front-end, in which case it must be written in C++).</li>
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]208 <li>Test cases, especially for regressions, should be reduced as much as
Duncan Sands16f122e2007-03-30 12:22:09 +0000[diff] [blame]209 possible, by <a href="Bugpoint.html">bugpoint</a> or
Reid Spencerc4a1f8b2007-02-14 07:57:48 +0000[diff] [blame]210 manually. It is unacceptable
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]211 to place an entire failing program into <tt>llvm/test</tt> as this creates
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]212 a <i>time-to-test</i> burden on all developers. Please keep them short.</li>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]213 </ol>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]214
215 <p>Note that llvm/test is designed for regression and small feature tests
216 only. More extensive test cases (e.g., entire applications, benchmarks,
217 etc) should be added to the <tt>llvm-test</tt> test suite. The llvm-test
218 suite is for coverage (correctness, performance, etc) testing, not feature
Chris Lattner8d033d12007-02-19 06:57:46 +0000[diff] [blame]219 or regression testing.</p>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]220</div>
221
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]222<!-- _______________________________________________________________________ -->
Chris Lattnera90a7d62007-02-19 05:47:13 +0000[diff] [blame]223<div class="doc_subsection"> <a name="quality">Quality</a></div>
224<div class="doc_text">
225 <p>The minimum quality standards that any change must satisfy before being
226 committed to the main development branch are:</p>
227 <ol>
228 <li>Code must adhere to the
229 <a href="CodingStandards.html">LLVM Coding Standards</a>.</li>
230 <li>Code must compile cleanly (no errors, no warnings) on at least one
231 platform.</li>
232 <li>Bug fixes and new features should <a href="#testcases">include a
233 testcase</a> so we know if the fix/feature ever regresses in the
234 future.</li>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]235 <li>Code must pass the dejagnu (<tt>llvm/test</tt>) test suite.</li>
Chris Lattnera90a7d62007-02-19 05:47:13 +0000[diff] [blame]236 <li>The code must not cause regressions on a reasonable subset of llvm-test,
237 where "reasonable" depends on the contributor's judgement and the scope
238 of the change (more invasive changes require more testing). A reasonable
239 subset is "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
240 </ol>
241 <p>Additionally, the committer is responsible for addressing any problems
242 found in the future that the change is responsible for. For example:</p>
243 <ul>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]244 <li>The code should compile cleanly on all supported platforms.</li>
245 <li>The changes should not cause any correctness regressions in the
246 <tt>llvm-test</tt> suite and must not cause any major performance
247 regressions.</li>
Chris Lattnera90a7d62007-02-19 05:47:13 +0000[diff] [blame]248 <li>The change set should not cause performance or correctness regressions
249 for the LLVM tools.</li>
250 <li>The changes should not cause performance or correctness regressions in
251 code compiled by LLVM on all applicable targets.</li>
252 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
253 bugs</a> that result from your change.</li>
254 </ul>
255
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]256 <p>We prefer for this to be handled before submission but understand that it
257 isn't possible to test all of this for every submission. Our nightly
258 testing
Chris Lattnera90a7d62007-02-19 05:47:13 +0000[diff] [blame]259 infrastructure normally finds these problems. A good rule of thumb is to
260 check the nightly testers for regressions the day after your change.</p>
261
262 <p>Commits that violate these quality standards (e.g. are very broken) may
263 be reverted. This is necessary when the change blocks other developers from
264 making progress. The developer is welcome to re-commit the change after
265 the problem has been fixed.</p>
266</div>
267
268<!-- _______________________________________________________________________ -->
Chris Lattner10f15142007-02-19 05:49:11 +0000[diff] [blame]269<div class="doc_subsection">
270 <a name="commitaccess">Obtaining Commit Access</a></div>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]271<div class="doc_text">
272
273<p>
274We grant commit access to contributors with a track record of submitting high
Chris Lattner4b6d9652007-12-03 00:36:20 +0000[diff] [blame]275quality patches. If you would like commit access, please send an email to
276<a href="mailto:sabre@nondot.org">Chris</a> with the following information:</p>
277
278<ol>
279 <li>The user name you want to commit with, e.g. "sabre".</li>
280 <li>The full name and email address you want message to llvm-commits to come
281 from, e.g. "Chris Lattner &lt;sabre@nondot.org&gt;".</li>
282 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
283 Note that you don't ever tell us what your password is, you just give it
284 to us in an encrypted form. To get this, run "htpasswd" (a utility that
285 comes with apache) in crypt mode (often enabled with "-d"), or find a web
286 page that will do it for you.</li>
287</ol>
288
289<p>Once you've been granted commit access, you should be able to check out an
290 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
291 normal anonymous URL of "http://llvm.org/...". The first time you commit
292 you'll have to type in your password. Note that you may get a warning from
293 SVN about an untrusted key, you can ignore this. To verify that your commit
294 access works, please do a test commit (e.g. change a comment or add a blank
295 line). Your first commit to a repository may require the autogenerated email
296 to be approved by a mailing list. This is normal, and will be done when
297 the mailing list owner has time.</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]298
299<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattner4b6d9652007-12-03 00:36:20 +0000[diff] [blame]300
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]301<ol>
302 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM.
303 To get approval, submit a <a href="#patches">patch</a> to
304 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
305 llvm-commits</a>. When approved you may commit it yourself.</li>
306 <li>You are allowed to commit patches without approval which you think are
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]307 obvious. This is clearly a subjective decision &mdash; we simply expect you
308 to use good judgement. Examples include: fixing build breakage, reverting
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]309 obviously broken patches, documentation/comment changes, any other minor
310 changes.</li>
311 <li>You are allowed to commit patches without approval to those portions
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]312 of LLVM that you have contributed or maintain (i.e., have been assigned
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]313 responsibility for), with the proviso that such commits must not break the
314 build. This is a "trust but verify" policy and commits of this nature are
315 reviewed after they are committed.</li>
316 <li>Multiple violations of these policies or a single egregious violation
317 may cause commit access to be revoked.</li>
318</ol>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]319
320<p>In any case, your changes are still subject to <a href="#reviews">code
321review</a> (either before or after they are committed, depending on the nature
322of the change). You are encouraged to review other peoples' patches as well,
Chris Lattner73f28252007-03-02 02:57:34 +0000[diff] [blame]323but you aren't required to.</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]324
325</div>
326
327<!-- _______________________________________________________________________ -->
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]328<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
329<div class="doc_text">
330 <p>When a developer begins a major new project with the aim of contributing
331 it back to LLVM, s/he should inform the community with an email to
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]332 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]333 email list, to the extent possible. The reason for this is to:
334 <ol>
335 <li>keep the community informed about future changes to LLVM, </li>
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]336 <li>avoid duplication of effort by preventing multiple parties working on
337 the same thing and not knowing about it, and</li>
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]338 <li>ensure that any technical issues around the proposed work are
339 discussed and resolved before any significant work is done.</li>
340 </ol>
341
342 <p>The design of LLVM is carefully controlled to ensure that all the pieces
343 fit together well and are as consistent as possible. If you plan to make a
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]344 major change to the way LLVM works or want to add a major new extension, it
345 is a good idea to get consensus with the development
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]346 community before you start working on it.</p>
347
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]348 <p>Once the design of the new feature is finalized, the work itself should be
349 done as a series of <a href="#incremental">incremental changes</a>, not as
350 a long-term development branch.</p>
351
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]352</div>
353
354<!-- _______________________________________________________________________ -->
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]355<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]356</div>
357<div class="doc_text">
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]358 <p>In the LLVM project, we do all significant changes as a series of
359 incremental patches. We have a strong dislike for huge changes or
360 long-term development branches. Long-term development branches have a
361 number of drawbacks:</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]362
363 <ol>
364 <li>Branches must have mainline merged into them periodically. If the branch
365 development and mainline development occur in the same pieces of code,
366 resolving merge conflicts can take a lot of time.</li>
367 <li>Other people in the community tend to ignore work on branches.</li>
368 <li>Huge changes (produced when a branch is merged back onto mainline) are
369 extremely difficult to <a href="#reviews">code review</a>.</li>
370 <li>Branches are not routinely tested by our nightly tester
371 infrastructure.</li>
372 <li>Changes developed as monolithic large changes often don't work until the
373 entire set of changes is done. Breaking it down into a set of smaller
374 changes increases the odds that any of the work will be committed to the
375 main repository.</li>
376 </ol>
377
378 <p>
379 To address these problems, LLVM uses an incremental development style and we
380 require contributors to follow this practice when making a large/invasive
381 change. Some tips:</p>
382
383 <ul>
384 <li>Large/invasive changes usually have a number of secondary changes that
385 are required before the big change can be made (e.g. API cleanup, etc).
386 These sorts of changes can often be done before the major change is done,
387 independently of that work.</li>
388 <li>The remaining inter-related work should be decomposed into unrelated
389 sets of changes if possible. Once this is done, define the first increment
390 and get consensus on what the end goal of the change is.</li>
Chris Lattner4d67b162007-02-19 05:59:30 +0000[diff] [blame]391
392 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part
393 of a planned series of changes that works towards the development goal.</li>
394
395 <li>Each change should be kept as small as possible. This simplifies your
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]396 work (into a logical progression), simplifies code review and reduces the
397 chance that you will get negative feedback on the change. Small increments
398 also facilitate the maintenance of a high quality code base.</li>
Chris Lattner4d67b162007-02-19 05:59:30 +0000[diff] [blame]399
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]400 <li>Often, an independent precursor to a big change is to add a new API and
401 slowly migrate clients to use the new API. Each change to use the new
402 API is often "obvious" and can be committed without review. Once the
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]403 new API is in place and used, it is much easier to replace the
404 underlying implementation of the API. This implementation change is
405 logically separate from the API change.</li>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]406 </ul>
407
408 <p>If you are interested in making a large change, and this scares you, please
409 make sure to first <a href="#newwork">discuss the change/gather
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]410 consensus</a> then ask about the best way to go about making
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]411 the change.</p>
412</div>
413
414<!-- _______________________________________________________________________ -->
Chris Lattner793eead2007-02-19 05:43:04 +0000[diff] [blame]415<div class="doc_subsection"><a name="attribution">Attribution of
416Changes</a></div>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]417<div class="doc_text">
418 <p>We believe in correct attribution of contributions to
419 their contributors. However, we do not want the source code to be littered
Chris Lattnerebf56662007-12-29 19:56:08 +0000[diff] [blame]420 with random attributions "this code written by J Random Guy" (this is noisy
421 and distracting. In practice, the revision control system keeps a perfect
422 history of who change what, and the CREDITS.txt file describes higher-level
423 contributions.</p>
424
425 <p>Overall, please do not add contributor names to the source base.</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]426</div>
427
428
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]429
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]430<!--=========================================================================-->
Chris Lattner83967802007-02-19 06:19:16 +0000[diff] [blame]431<div class="doc_section">
432 <a name="clp">Copyright, License, and Patents</a>
433</div>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]434<!--=========================================================================-->
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]435
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]436<div class="doc_text">
Reid Spencer68812c72007-02-19 17:38:38 +0000[diff] [blame]437 <p>This section addresses the issues of copyright, license and patents for
438 the LLVM project.
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]439 Currently, the University of Illinois is the LLVM copyright holder and the
440 terms of its license to LLVM users and developers is the
441 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]442 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]443
444<div class="doc_notes">
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]445 <p><b>NOTE: This section deals with legal matters but does not provide
Reid Spencer68812c72007-02-19 17:38:38 +0000[diff] [blame]446 legal advice. We are not lawyers, please seek legal counsel from an
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]447 attorney.</b></p>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]448</div>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]449</div>
450
451<!-- _______________________________________________________________________ -->
452<div class="doc_subsection"><a name="copyright">Copyright</a></div>
453<div class="doc_text">
454 <p>
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]455 <p>For consistency and ease of management, the project requires the
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]456 copyright for all LLVM software to be held by a single copyright holder:
457 the University of Illinois (UIUC).</p>
458
459 <p>
460 Although UIUC may eventually reassign the copyright of the software to another
Chris Lattnere1d4c2e2008-05-20 20:06:53 +0000[diff] [blame^]461 entity (e.g. a dedicated non-profit "LLVM Organization")
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]462 the intent for the project is to always have a single entity hold the
463 copyrights to LLVM at any given time.</p>
464
465 <p>We believe that having a single copyright
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]466 holder is in the best interests of all developers and users as it greatly
467 reduces the managerial burden for any kind of administrative or technical
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]468 decisions about LLVM. The goal of the LLVM project is to always keep the code
469 open and <a href="#license">licensed under a very liberal license</a>.</p>
Chris Lattnere1d4c2e2008-05-20 20:06:53 +0000[diff] [blame^]470
471 <p>When contributing code, you also affirm that you are legally entitled to
472 grant this copyright, personally or on behalf of your employer. If the code
473 belongs to some other entity, please raise this issue with the oversight
474 group before the code is committed.</p>
475
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]476</div>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]477
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]478<!-- _______________________________________________________________________ -->
479<div class="doc_subsection"><a name="license">License</a></div>
480<div class="doc_text">
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]481 <p>We intend to keep LLVM perpetually open source
482 and to use a liberal open source license. The current license is the
Reid Spencer33610372007-02-14 16:21:10 +0000[diff] [blame]483 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">
484 University of Illinois/NCSA Open Source License</a>, which boils
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]485 down to this:</p>
486 <ul>
487 <li>You can freely distribute LLVM.</li>
488 <li>You must retain the copyright notice if you redistribute LLVM.</li>
Chris Lattnere1d4c2e2008-05-20 20:06:53 +0000[diff] [blame^]489 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g.
490 in an included readme file).</li>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]491 <li>You can't use our names to promote your LLVM derived products.</li>
492 <li>There's no warranty on LLVM at all.</li>
493 </ul>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]494
495 <p>We believe this fosters the widest adoption of LLVM because it <b>allows
496 commercial products to be derived from LLVM</b> with few restrictions and
Reid Spencer05cc0992007-02-14 22:55:40 +0000[diff] [blame]497 without a requirement for making any derived works also open source (i.e.
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]498 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
499 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
Reid Spencer77c01f42007-02-14 22:58:39 +0000[diff] [blame]500 if further clarification is needed.</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]501
Chris Lattner7d92b912007-02-22 06:33:23 +0000[diff] [blame]502 <p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
Bill Wendling0ae16352007-02-19 18:32:40 +0000[diff] [blame]503 This means that anything "linked" into llvm-gcc must itself be compatible
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]504 with the GPL, and must be releasable under the terms of the GPL. This implies
Chris Lattner7d92b912007-02-22 06:33:23 +0000[diff] [blame]505 that <b>any code linked into llvm-gcc and distributed to others may be subject
506 to the viral aspects of the GPL</b> (for example, a proprietary code generator
Chris Lattner072d5782007-02-23 06:53:06 +0000[diff] [blame]507 linked into llvm-gcc must be made available under the GPL). This is not a
508 problem for code already distributed under a more liberal license (like the
509 UIUC license), and does not affect code generated by llvm-gcc. It may be a
510 problem if you intend to base commercial development on llvm-gcc without
Chris Lattner78914c32007-02-19 06:57:16 +0000[diff] [blame]511 redistributing your source code.</p>
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]512
513 <p>We have no plans to change the license of LLVM. If you have questions
514 or comments about the license, please contact the <a
515 href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
516
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]517</div>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]518
519<!-- _______________________________________________________________________ -->
520<div class="doc_subsection"><a name="patents">Patents</a></div>
521<div class="doc_text">
522
Chris Lattnera65670e2007-02-19 06:13:50 +0000[diff] [blame]523<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
524 actually removed code from LLVM in the past that was found to infringe).
Chris Lattner30ff8f82007-02-19 06:15:33 +0000[diff] [blame]525 Having code in LLVM that infringes on patents would violate an important
526 goal of the project by making it hard or impossible to reuse the code for
527 arbitrary purposes (including commercial use).</p>
Chris Lattnera65670e2007-02-19 06:13:50 +0000[diff] [blame]528
529<p>When contributing code, we expect contributors to notify us of any potential
530 for patent-related trouble with their changes. If you own the rights to a
531 patent and would like to contribute code to LLVM that relies on it, we
532 require that you sign an agreement that allows any other user of LLVM to
533 freely use your patent. Please contact the <a
534 href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
535 details.</p>
Chris Lattner76fa27f2007-02-19 06:05:58 +0000[diff] [blame]536</div>
537
538
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]539<!-- _______________________________________________________________________ -->
540<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
541<div class="doc_text">
Chris Lattner8087c0b2007-02-19 03:50:31 +0000[diff] [blame]542 <p>With regards to the LLVM copyright and licensing, developers agree to
543 assign their copyrights to UIUC for any contribution made so that
544 the entire software base can be managed by a single copyright holder. This
545 implies that any contributions can be licensed under the license that the
Chris Lattner10f15142007-02-19 05:49:11 +0000[diff] [blame]546 project uses.</p>
Reid Spencer56e56552007-02-14 07:22:19 +0000[diff] [blame]547</div>
548
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]549<!-- *********************************************************************** -->
550<hr>
551<address>
552 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
553 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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555 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
Chris Lattner30ff8f82007-02-19 06:15:33 +0000[diff] [blame]556 Written by the
Reid Spencerc4a1f8b2007-02-14 07:57:48 +0000[diff] [blame]557 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
Reid Spencera0f02a32007-02-13 09:06:01 +0000[diff] [blame]558 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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560</address>
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