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5 <title>LLVM Developer Policy</title>
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7</head>
8<body>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]9
10<div class="doc_title">LLVM Developer Policy</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]11<ol>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]12 <li><a href="#introduction">Introduction</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]13 <li><a href="#policies">Developer Policies</a>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]14 <ol>
Chris Lattner1653fec2007-02-19 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 Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]17 <li><a href="#reviews">Code Reviews</a></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]18 <li><a href="#testcases">Test Cases</a></li>
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]19 <li><a href="#quality">Quality</a></li>
20 <li><a href="#commitaccess">Obtaining Commit Access</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]21 <li><a href="#newwork">Making a Major Change</a></li>
22 <li><a href="#incremental">Incremental Development</a></li>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]23 <li><a href="#attribution">Attribution of Changes</a></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]24 </ol></li>
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]25 <li><a href="#clp">Copyright, License, and Patents</a>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]26 <ol>
27 <li><a href="#copyright">Copyright</a></li>
28 <li><a href="#license">License</a></li>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]29 <li><a href="#patents">Patents</a></li>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]30 <li><a href="#devagree">Developer Agreements</a></li>
31 </ol></li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]32</ol>
Chris Lattner2ae49dd2007-02-19 06:24:23 +0000[diff] [blame]33<div class="doc_author">Written by the LLVM Oversight Team</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]34
35<!--=========================================================================-->
Reid Spencere7bd7d62007-02-14 17:24:04 +0000[diff] [blame]36<div class="doc_section"><a name="introduction">Introduction</a></div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]37<!--=========================================================================-->
38<div class="doc_text">
39 <p>This document contains the LLVM Developer Policy which defines the
Reid Spencerbed92532007-02-13 17:04:09 +0000[diff] [blame]40 project's policy towards developers and their contributions. The intent of
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]41 this policy is to eliminate mis-communication, rework, and confusion that
42 might arise from the distributed nature of LLVM's development. By stating
43 the policy in clear terms, we hope each developer can know ahead of time
44 what to expect when making LLVM contributions.</p>
Reid Spencer5b9a6092007-02-14 22:55:40 +0000[diff] [blame]45 <p>This policy is also designed to accomplish the following objectives:</p>
46 <ol>
47 <li>Attract both users and developers to the LLVM project.</li>
48 <li>Make life as simple and easy for contributors as possible.</li>
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]49 <li>Keep the top of Subversion trees as stable as possible.</li>
Reid Spencer5b9a6092007-02-14 22:55:40 +0000[diff] [blame]50 </ol>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]51
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]52 <p>This policy is aimed at frequent contributors to LLVM. People interested in
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]53 contributing one-off patches can do so in an informal way by sending them to
54 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
55 llvm-commits mailing list</a> and engaging another developer to see it through
56 the process.</p>
57
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]58</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]59
60<!--=========================================================================-->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]61<div class="doc_section"><a name="policies">Developer Policies</a></div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]62<!--=========================================================================-->
63<div class="doc_text">
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]64 <p>This section contains policies that pertain to frequent LLVM
Reid Spencercb069bb2007-02-19 17:38:38 +0000[diff] [blame]65 developers. We always welcome <a href="#patches">one-off patches</a> from
66 people who do not routinely contribute to LLVM, but we expect more from
67 frequent contributors to keep the system as efficient as possible for
68 everyone.
69 Frequent LLVM contributors are expected to meet the following requirements in
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]70 order for LLVM to maintain a high standard of quality.<p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]71</div>
72
73<!-- _______________________________________________________________________ -->
74<div class="doc_subsection"> <a name="informed">Stay Informed</a> </div>
75<div class="doc_text">
76 <p>Developers should stay informed by reading at least the
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]77 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
78 email list. If you are doing anything more than just casual work on LLVM,
79 it is suggested that you also subscribe to the
80 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
81 list and pay attention to changes being made by others.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]82 <p>We recommend that active developers register an email account with
83 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to
84 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a>
85 email list to keep track of bugs and enhancements occurring in LLVM.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]86</div>
87
88<!-- _______________________________________________________________________ -->
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]89<div class="doc_subsection"> <a name="patches">Making a Patch</a></div>
90
91<div class="doc_text">
92
93<p>When making a patch for review, the goal is to make it as easy for the
94 reviewer to read it as possible. As such, we recommend that you:</p>
95 <ol>
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]96 <li>Make your patch against the Subversion trunk, not a branch, and not an
97 old version of LLVM. This makes it easy to apply the patch.</li>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]98
99 <li>Similarly, patches should be submitted soon after they are generated.
100 Old patches may not apply correctly if the underlying code changes between
101 the time the patch was created and the time it is applied.</li>
102
103 <li>Patches should be made with this command:
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]104 <pre>svn diff -x -u</pre>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]105 or with the utility <tt>utils/mkpatch</tt>, which makes it easy to read the
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]106 diff.</li>
107
108 <li>Patches should not include differences in generated code such as the
109 code generated by <tt>flex</tt>, <tt>bison</tt> or <tt>tblgen</tt>. The
110 <tt>utils/mkpatch</tt> utility takes care of this for you.</li>
111
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]112 </ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]113
114 <p>When sending a patch to a mailing list, it is a good idea to send it as an
115 <em>attachment</em> to the message, not embedded into the text of the
116 message. This ensures that your mailer will not mangle the patch when it
117 sends it (e.g. by making whitespace changes or by wrapping lines).</p>
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]118</div>
119
120<!-- _______________________________________________________________________ -->
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]121<div class="doc_subsection"> <a name="reviews">Code Reviews</a></div>
122<div class="doc_text">
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]123 <p>LLVM has a code review policy. Code review is one way to increase the
124 quality of software. We generally follow these policies:</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]125 <ol>
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]126 <li>All developers are required to have significant changes reviewed
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]127 before they are committed to the repository.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]128 <li>Code reviews are conducted by email, usually on the llvm-commits
129 list.</li>
130 <li>Code can be reviewed either before it is committed or after. We expect
131 major changes to be reviewed before being committed, but smaller
132 changes (or changes where the developer owns the component) can be
133 reviewed after commit.</li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]134 <li>The developer responsible for a code change is also responsible for
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]135 making all necessary review-related changes.</li>
Reid Spencercb069bb2007-02-19 17:38:38 +0000[diff] [blame]136 <li>Code review can be an iterative process, which continues until the patch
Chris Lattner1653fec2007-02-19 05:57:29 +0000[diff] [blame]137 is ready to be committed.</li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]138 </ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]139
140 <p>Developers should participate in code reviews as both reviewers and
Reid Spencercb069bb2007-02-19 17:38:38 +0000[diff] [blame]141 reviewees. If someone is kind enough to review your code, you should
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]142 return the favor for someone else. Note that anyone is welcome to review
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]143 and give feedback on a patch, but only people with Subversion write access
144 can approve it.</p>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]145
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]146</div>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]147
148<!-- _______________________________________________________________________ -->
149<div class="doc_subsection"> <a name="testcases">Test Cases</a></div>
150<div class="doc_text">
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]151 <p>Developers are required to create test cases for any bugs fixed and any new
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]152 features added. Some tips for getting your testcase approved:</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]153 <ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]154 <li>All feature and regression test cases are added to the
Reid Spencer80483bb2007-02-13 09:20:14 +0000[diff] [blame]155 <tt>llvm/test</tt> directory. The appropriate sub-directory should be
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]156 selected (see the <a href="TestingGuide.html">Testing Guide</a> for
Reid Spencer40602962007-02-13 20:57:57 +0000[diff] [blame]157 details).</li>
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]158 <li>Test cases should be written in
159 <a href="LangRef.html">LLVM assembly language</a> unless the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]160 feature or regression being tested requires another language (e.g. the
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]161 bug being fixed or feature being implemented is in the llvm-gcc C++
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]162 front-end, in which case it must be written in C++).</li>
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]163 <li>Test cases, especially for regressions, should be reduced as much as
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]164 possible, by <a href="Bugpoint.html">bugpoint</a> or
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]165 manually. It is unacceptable
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]166 to place an entire failing program into <tt>llvm/test</tt> as this creates
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]167 a <i>time-to-test</i> burden on all developers. Please keep them short.</li>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]168 </ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]169
170 <p>Note that llvm/test is designed for regression and small feature tests
171 only. More extensive test cases (e.g., entire applications, benchmarks,
172 etc) should be added to the <tt>llvm-test</tt> test suite. The llvm-test
173 suite is for coverage (correctness, performance, etc) testing, not feature
Chris Lattner64113a52007-02-19 06:57:46 +0000[diff] [blame]174 or regression testing.</p>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]175</div>
176
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]177<!-- _______________________________________________________________________ -->
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]178<div class="doc_subsection"> <a name="quality">Quality</a></div>
179<div class="doc_text">
180 <p>The minimum quality standards that any change must satisfy before being
181 committed to the main development branch are:</p>
182 <ol>
183 <li>Code must adhere to the
184 <a href="CodingStandards.html">LLVM Coding Standards</a>.</li>
185 <li>Code must compile cleanly (no errors, no warnings) on at least one
186 platform.</li>
187 <li>Bug fixes and new features should <a href="#testcases">include a
188 testcase</a> so we know if the fix/feature ever regresses in the
189 future.</li>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]190 <li>Code must pass the dejagnu (<tt>llvm/test</tt>) test suite.</li>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]191 <li>The code must not cause regressions on a reasonable subset of llvm-test,
192 where "reasonable" depends on the contributor's judgement and the scope
193 of the change (more invasive changes require more testing). A reasonable
194 subset is "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li>
195 </ol>
196 <p>Additionally, the committer is responsible for addressing any problems
197 found in the future that the change is responsible for. For example:</p>
198 <ul>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]199 <li>The code should compile cleanly on all supported platforms.</li>
200 <li>The changes should not cause any correctness regressions in the
201 <tt>llvm-test</tt> suite and must not cause any major performance
202 regressions.</li>
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]203 <li>The change set should not cause performance or correctness regressions
204 for the LLVM tools.</li>
205 <li>The changes should not cause performance or correctness regressions in
206 code compiled by LLVM on all applicable targets.</li>
207 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla
208 bugs</a> that result from your change.</li>
209 </ul>
210
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]211 <p>We prefer for this to be handled before submission but understand that it
212 isn't possible to test all of this for every submission. Our nightly
213 testing
Chris Lattner39582bd2007-02-19 05:47:13 +0000[diff] [blame]214 infrastructure normally finds these problems. A good rule of thumb is to
215 check the nightly testers for regressions the day after your change.</p>
216
217 <p>Commits that violate these quality standards (e.g. are very broken) may
218 be reverted. This is necessary when the change blocks other developers from
219 making progress. The developer is welcome to re-commit the change after
220 the problem has been fixed.</p>
221</div>
222
223<!-- _______________________________________________________________________ -->
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]224<div class="doc_subsection">
225 <a name="commitaccess">Obtaining Commit Access</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]226<div class="doc_text">
227
228<p>
229We grant commit access to contributors with a track record of submitting high
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame^]230quality patches. If you would like commit access, please send an email to
231<a href="mailto:sabre@nondot.org">Chris</a> with the following information:</p>
232
233<ol>
234 <li>The user name you want to commit with, e.g. "sabre".</li>
235 <li>The full name and email address you want message to llvm-commits to come
236 from, e.g. "Chris Lattner &lt;sabre@nondot.org&gt;".</li>
237 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM".
238 Note that you don't ever tell us what your password is, you just give it
239 to us in an encrypted form. To get this, run "htpasswd" (a utility that
240 comes with apache) in crypt mode (often enabled with "-d"), or find a web
241 page that will do it for you.</li>
242</ol>
243
244<p>Once you've been granted commit access, you should be able to check out an
245 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the
246 normal anonymous URL of "http://llvm.org/...". The first time you commit
247 you'll have to type in your password. Note that you may get a warning from
248 SVN about an untrusted key, you can ignore this. To verify that your commit
249 access works, please do a test commit (e.g. change a comment or add a blank
250 line). Your first commit to a repository may require the autogenerated email
251 to be approved by a mailing list. This is normal, and will be done when
252 the mailing list owner has time.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]253
254<p>If you have recently been granted commit access, these policies apply:</p>
Chris Lattnerbebcdabd82007-12-03 00:36:20 +0000[diff] [blame^]255
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]256<ol>
257 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM.
258 To get approval, submit a <a href="#patches">patch</a> to
259 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">
260 llvm-commits</a>. When approved you may commit it yourself.</li>
261 <li>You are allowed to commit patches without approval which you think are
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]262 obvious. This is clearly a subjective decision &mdash; we simply expect you
263 to use good judgement. Examples include: fixing build breakage, reverting
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]264 obviously broken patches, documentation/comment changes, any other minor
265 changes.</li>
266 <li>You are allowed to commit patches without approval to those portions
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]267 of LLVM that you have contributed or maintain (i.e., have been assigned
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]268 responsibility for), with the proviso that such commits must not break the
269 build. This is a "trust but verify" policy and commits of this nature are
270 reviewed after they are committed.</li>
271 <li>Multiple violations of these policies or a single egregious violation
272 may cause commit access to be revoked.</li>
273</ol>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]274
275<p>In any case, your changes are still subject to <a href="#reviews">code
276review</a> (either before or after they are committed, depending on the nature
277of the change). You are encouraged to review other peoples' patches as well,
Chris Lattnerd2dceea2007-03-02 02:57:34 +0000[diff] [blame]278but you aren't required to.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]279
280</div>
281
282<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]283<div class="doc_subsection"> <a name="newwork">Making a Major Change</a></div>
284<div class="doc_text">
285 <p>When a developer begins a major new project with the aim of contributing
286 it back to LLVM, s/he should inform the community with an email to
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]287 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]288 email list, to the extent possible. The reason for this is to:
289 <ol>
290 <li>keep the community informed about future changes to LLVM, </li>
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]291 <li>avoid duplication of effort by preventing multiple parties working on
292 the same thing and not knowing about it, and</li>
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]293 <li>ensure that any technical issues around the proposed work are
294 discussed and resolved before any significant work is done.</li>
295 </ol>
296
297 <p>The design of LLVM is carefully controlled to ensure that all the pieces
298 fit together well and are as consistent as possible. If you plan to make a
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]299 major change to the way LLVM works or want to add a major new extension, it
300 is a good idea to get consensus with the development
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]301 community before you start working on it.</p>
302
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]303 <p>Once the design of the new feature is finalized, the work itself should be
304 done as a series of <a href="#incremental">incremental changes</a>, not as
305 a long-term development branch.</p>
306
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]307</div>
308
309<!-- _______________________________________________________________________ -->
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]310<div class="doc_subsection"> <a name="incremental">Incremental Development</a>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]311</div>
312<div class="doc_text">
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]313 <p>In the LLVM project, we do all significant changes as a series of
314 incremental patches. We have a strong dislike for huge changes or
315 long-term development branches. Long-term development branches have a
316 number of drawbacks:</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]317
318 <ol>
319 <li>Branches must have mainline merged into them periodically. If the branch
320 development and mainline development occur in the same pieces of code,
321 resolving merge conflicts can take a lot of time.</li>
322 <li>Other people in the community tend to ignore work on branches.</li>
323 <li>Huge changes (produced when a branch is merged back onto mainline) are
324 extremely difficult to <a href="#reviews">code review</a>.</li>
325 <li>Branches are not routinely tested by our nightly tester
326 infrastructure.</li>
327 <li>Changes developed as monolithic large changes often don't work until the
328 entire set of changes is done. Breaking it down into a set of smaller
329 changes increases the odds that any of the work will be committed to the
330 main repository.</li>
331 </ol>
332
333 <p>
334 To address these problems, LLVM uses an incremental development style and we
335 require contributors to follow this practice when making a large/invasive
336 change. Some tips:</p>
337
338 <ul>
339 <li>Large/invasive changes usually have a number of secondary changes that
340 are required before the big change can be made (e.g. API cleanup, etc).
341 These sorts of changes can often be done before the major change is done,
342 independently of that work.</li>
343 <li>The remaining inter-related work should be decomposed into unrelated
344 sets of changes if possible. Once this is done, define the first increment
345 and get consensus on what the end goal of the change is.</li>
Chris Lattner8bb16ff2007-02-19 05:59:30 +0000[diff] [blame]346
347 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part
348 of a planned series of changes that works towards the development goal.</li>
349
350 <li>Each change should be kept as small as possible. This simplifies your
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]351 work (into a logical progression), simplifies code review and reduces the
352 chance that you will get negative feedback on the change. Small increments
353 also facilitate the maintenance of a high quality code base.</li>
Chris Lattner8bb16ff2007-02-19 05:59:30 +0000[diff] [blame]354
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]355 <li>Often, an independent precursor to a big change is to add a new API and
356 slowly migrate clients to use the new API. Each change to use the new
357 API is often "obvious" and can be committed without review. Once the
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]358 new API is in place and used, it is much easier to replace the
359 underlying implementation of the API. This implementation change is
360 logically separate from the API change.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]361 </ul>
362
363 <p>If you are interested in making a large change, and this scares you, please
364 make sure to first <a href="#newwork">discuss the change/gather
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]365 consensus</a> then ask about the best way to go about making
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]366 the change.</p>
367</div>
368
369<!-- _______________________________________________________________________ -->
Chris Lattnerc7d954e2007-02-19 05:43:04 +0000[diff] [blame]370<div class="doc_subsection"><a name="attribution">Attribution of
371Changes</a></div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]372<div class="doc_text">
373 <p>We believe in correct attribution of contributions to
374 their contributors. However, we do not want the source code to be littered
375 with random attributions (this is noisy/distracting and revision control
376 keeps a perfect history of this anyway). As such, we follow these rules:</p>
377 <ol>
378 <li>Developers who originate new files in LLVM should place their name at
379 the top of the file per the
380 <a href="CodingStandards.html#scf_commenting">Coding Standards</a>.</li>
381 <li>There should be only one name at the top of the file and it should be
382 the person who created the file.</li>
383 <li>Placing your name in the file does not imply <a
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]384 href="#clp">copyright</a>: it is only used to attribute the file to
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]385 its original author.</li>
386 <li>Developers should be aware that after some time has passed, the name at
387 the top of a file may become meaningless as maintenance/ownership of files
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]388 changes. Despite this, once set, the attribution of a file never changes.
389 Revision control keeps an accurate history of contributions.</li>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]390 <li>Developers should maintain their entry in the
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]391 <a href="http://llvm.org/svn/llvm-project/llvm/trunk/CREDITS.TXT">CREDITS.txt</a>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]392 file to summarize their contributions.</li>
393 <li>Commit comments should contain correct attribution of the person who
394 submitted the patch if that person is not the committer (i.e. when a
395 developer with commit privileges commits a patch for someone else).</li>
396 </ol>
397</div>
398
399
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]400
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]401<!--=========================================================================-->
Chris Lattner793aa382007-02-19 06:19:16 +0000[diff] [blame]402<div class="doc_section">
403 <a name="clp">Copyright, License, and Patents</a>
404</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]405<!--=========================================================================-->
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]406
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]407<div class="doc_text">
Reid Spencercb069bb2007-02-19 17:38:38 +0000[diff] [blame]408 <p>This section addresses the issues of copyright, license and patents for
409 the LLVM project.
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]410 Currently, the University of Illinois is the LLVM copyright holder and the
411 terms of its license to LLVM users and developers is the
412 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]413 Illinois/NCSA Open Source License</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]414
415<div class="doc_notes">
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]416 <p><b>NOTE: This section deals with legal matters but does not provide
Reid Spencercb069bb2007-02-19 17:38:38 +0000[diff] [blame]417 legal advice. We are not lawyers, please seek legal counsel from an
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]418 attorney.</b></p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]419</div>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]420</div>
421
422<!-- _______________________________________________________________________ -->
423<div class="doc_subsection"><a name="copyright">Copyright</a></div>
424<div class="doc_text">
425 <p>
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]426 <p>For consistency and ease of management, the project requires the
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]427 copyright for all LLVM software to be held by a single copyright holder:
428 the University of Illinois (UIUC).</p>
429
430 <p>
431 Although UIUC may eventually reassign the copyright of the software to another
432 entity (e.g. a dedicated non-profit "LLVM Organization", or something)
433 the intent for the project is to always have a single entity hold the
434 copyrights to LLVM at any given time.</p>
435
436 <p>We believe that having a single copyright
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]437 holder is in the best interests of all developers and users as it greatly
438 reduces the managerial burden for any kind of administrative or technical
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]439 decisions about LLVM. The goal of the LLVM project is to always keep the code
440 open and <a href="#license">licensed under a very liberal license</a>.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]441</div>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]442
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]443<!-- _______________________________________________________________________ -->
444<div class="doc_subsection"><a name="license">License</a></div>
445<div class="doc_text">
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]446 <p>We intend to keep LLVM perpetually open source
447 and to use a liberal open source license. The current license is the
Reid Spencer01f56be2007-02-14 16:21:10 +0000[diff] [blame]448 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">
449 University of Illinois/NCSA Open Source License</a>, which boils
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]450 down to this:</p>
451 <ul>
452 <li>You can freely distribute LLVM.</li>
453 <li>You must retain the copyright notice if you redistribute LLVM.</li>
454 <li>Binaries derived from LLVM must reproduce the copyright notice.</li>
455 <li>You can't use our names to promote your LLVM derived products.</li>
456 <li>There's no warranty on LLVM at all.</li>
457 </ul>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]458
459 <p>We believe this fosters the widest adoption of LLVM because it <b>allows
460 commercial products to be derived from LLVM</b> with few restrictions and
Reid Spencer5b9a6092007-02-14 22:55:40 +0000[diff] [blame]461 without a requirement for making any derived works also open source (i.e.
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]462 LLVM's license is not a "copyleft" license like the GPL). We suggest that you
463 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a>
Reid Spencer853418d2007-02-14 22:58:39 +0000[diff] [blame]464 if further clarification is needed.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]465
Chris Lattner7d8012b2007-02-22 06:33:23 +0000[diff] [blame]466 <p>Note that the LLVM Project does distribute llvm-gcc, <b>which is GPL.</b>
Bill Wendlingd932aab2007-02-19 18:32:40 +0000[diff] [blame]467 This means that anything "linked" into llvm-gcc must itself be compatible
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]468 with the GPL, and must be releasable under the terms of the GPL. This implies
Chris Lattner7d8012b2007-02-22 06:33:23 +0000[diff] [blame]469 that <b>any code linked into llvm-gcc and distributed to others may be subject
470 to the viral aspects of the GPL</b> (for example, a proprietary code generator
Chris Lattnerd5e2d402007-02-23 06:53:06 +0000[diff] [blame]471 linked into llvm-gcc must be made available under the GPL). This is not a
472 problem for code already distributed under a more liberal license (like the
473 UIUC license), and does not affect code generated by llvm-gcc. It may be a
474 problem if you intend to base commercial development on llvm-gcc without
Chris Lattner0cca50c2007-02-19 06:57:16 +0000[diff] [blame]475 redistributing your source code.</p>
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]476
477 <p>We have no plans to change the license of LLVM. If you have questions
478 or comments about the license, please contact the <a
479 href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a>.</p>
480
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]481</div>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]482
483<!-- _______________________________________________________________________ -->
484<div class="doc_subsection"><a name="patents">Patents</a></div>
485<div class="doc_text">
486
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]487<p>To the best of our knowledge, LLVM does not infringe on any patents (we have
488 actually removed code from LLVM in the past that was found to infringe).
Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]489 Having code in LLVM that infringes on patents would violate an important
490 goal of the project by making it hard or impossible to reuse the code for
491 arbitrary purposes (including commercial use).</p>
Chris Lattnerb87fb2a2007-02-19 06:13:50 +0000[diff] [blame]492
493<p>When contributing code, we expect contributors to notify us of any potential
494 for patent-related trouble with their changes. If you own the rights to a
495 patent and would like to contribute code to LLVM that relies on it, we
496 require that you sign an agreement that allows any other user of LLVM to
497 freely use your patent. Please contact the <a
498 href="mailto:llvm-oversight@cs.uiuc.edu">oversight group</a> for more
499 details.</p>
Chris Lattner1ff20cd2007-02-19 06:05:58 +0000[diff] [blame]500</div>
501
502
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]503<!-- _______________________________________________________________________ -->
504<div class="doc_subsection"><a name="devagree">Developer Agreements</a></div>
505<div class="doc_text">
Chris Lattner450f40a2007-02-19 03:50:31 +0000[diff] [blame]506 <p>With regards to the LLVM copyright and licensing, developers agree to
507 assign their copyrights to UIUC for any contribution made so that
508 the entire software base can be managed by a single copyright holder. This
509 implies that any contributions can be licensed under the license that the
Chris Lattner1acdc952007-02-19 05:49:11 +0000[diff] [blame]510 project uses.</p>
Reid Spencer78bade22007-02-14 07:22:19 +0000[diff] [blame]511</div>
512
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]513<!-- *********************************************************************** -->
514<hr>
515<address>
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Chris Lattnerd0742ce2007-02-19 06:15:33 +0000[diff] [blame]520 Written by the
Reid Spencer3eedbd32007-02-14 07:57:48 +0000[diff] [blame]521 <a href="mailto:llvm-oversight@cs.uiuc.edu">LLVM Oversight Group</a><br>
Reid Spencer8d0ac692007-02-13 09:06:01 +0000[diff] [blame]522 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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