This section contains policies that pertain generally to LLVM developers.
- LLVM Developers are expected to meet the following obligations in order
- for LLVM to maintain a high standard of quality.
+
This section contains policies that pertain generally to regular LLVM
+ developers. We always welcome random patches from
+ people who do not routinely contribute to LLVM, but expect more from regular
+ contributors to keep the system as efficient as possible for everyone.
+ Regular LLVM developers are expected to meet the following obligations in
+ order for LLVM to maintain a high standard of quality.
@@ -95,78 +90,61 @@
it back to LLVM, s/he should inform the community with an email to
the llvm-dev
email list, to the extent possible. The reason for this is to:
-
+
keep the community informed about future changes to LLVM,
avoid duplication of effort by having multiple parties working on the
same thing and not knowing about it, and
ensure that any technical issues around the proposed work are
discussed and resolved before any significant work is done.
-
+
The design of LLVM is carefully controlled to ensure that all the pieces
- fit together well. If you plan to make a major change to the way LLVM works or
+ fit together well and are as consistent as possible. If you plan to make a
+ major change to the way LLVM works or
a major new extension, it is a good idea to get consensus with the development
community before you start working on it.
LLVM has a code review policy. Code review is an excellent way to ensure
- high quality in the software. The following policies apply:
+
LLVM has a code review policy. Code review is one way to increase the
+ quality of software. We generally follow these policies:
All developers are required to have significant changes reviewed
before they are committed to the repository.
-
Code reviews are conducted by email.
-
Code can be reviewed either before it is committed or after.
+
Code reviews are conducted by email, usually on the llvm-commits
+ list.
+
Code can be reviewed either before it is committed or after. We expect
+ major changes to be reviewed before being committed, but smaller
+ changes (or changes where the developer owns the component) can be
+ reviewed after commit.
The developer responsible for a code change is also responsible for
- making all necessary review changes.
+ making all necessary review-related changes.
Developers should participate in code reviews as both a reviewer and
a reviewee. We don't have a dedicated team of reviewers. If someone is
kind enough to review your code, you should return the favor for someone
else.
LLVM uses an incremental development style and all developers are expected
- to follow this practice. Incremental development is a big key to LLVM's
- success and it is essential that developers submit incremental patches. The
- following defines the incremental development approach:
-
-
The first task is to define the increment and get consensus (with the
- LLVM development community) on what the end goal of the change is. Making
- random small changes that go nowhere is not useful for anyone.
-
An increment is the smallest patch size necessary to effect one change
- in LLVM.
-
Increments can be stand alone (e.g. to fix a bug), or part of a planned
- series of increments towards some development goal.
-
Increments should be kept as small as possible. This simplifies your
- work (into a logical progression), simplifies code review and reduces the
- chance that you will get negative feedback on the change. Small increments
- also facilitate the maintenance of a high quality code base.
-
Larger increments require a larger testing effort.
Code must compile cleanly (no errors, no warnings) on at least one
platform.
Code must pass the deja gnu (llvm/test) test suite.
+
The code must not cause regressions on a reasonable subset of llvm-test,
+ where "reasonable" depends on the contributor's judgement and the scope
+ of the change (more invasive changes require more testing). A reasonable
+ subset is "llvm-test/MultiSource/Benchmarks".
-
Additionally, the committer is responsible for addressing all of the
- following items (preferably before submission):
-
+
Additionally, the committer is responsible for addressing any problems
+ found that the change is responsible for. For example:
+
The code should compile cleanly on all platforms.
The changes should not cause regressions in the llvm-test
suite including SPEC CINT2000, SPEC CFP2000, SPEC CINT2006, and
@@ -175,15 +153,26 @@
for the LLVM tools.
The changes should not cause performance or correctness regressions in
code compiled by LLVM on all applicable targets.
-
+
You are expected to address any bugzilla
+ bugs that result from your change.
+
+
+
We prefer for this to be handled before submission but understand that it's
+ not possible to test all of this for every submission. Our nightly testing
+ infrastructure normally finds these problems. A good rule of thumb is to
+ check the nightly testers for regressions the day after your change.
+
+
Commits that violate these quality standards (e.g. are very broken) may
+ be reverted. This is necessary when the change blocks other developers from
+ making progress. The developer is welcome to re-commit the change after
+ the problem has been fixed.
Developers are required to create test cases for regressions and new
- features and include them with their changes. The following policies
- apply:
+
Developers are required to create test cases for any bugs fixed and any new
+ features added. The following policies apply:
All feature and regression test cases must be added to the
llvm/test directory. The appropriate sub-directory should be
@@ -192,7 +181,7 @@
Test cases should be written in
LLVM assembly language unless the
feature or regression being tested requires another language (e.g. the
- bug being fixed or feature being implemented is in the lvm-gcc C++
+ bug being fixed or feature being implemented is in the llvm-gcc C++
front-end).
Test cases, especially for regressions, should be reduced as much as
possible, by bugpoint or
@@ -201,17 +190,136 @@
a time-to-test burden on all developers. Please keep them short.
More extensive test cases (applications, benchmarks, etc.) should be
added to the llvm-test test suite. This test suite is for
- coverage not features or regressions.
+We grant commit access to contributors with a track record of submitting high
+quality patches. If you would like commit access, please send an email to the
+LLVM oversight group.
+
+
If you have recently been granted commit access, these policies apply:
+
+
You are granted commit-after-approval to all parts of LLVM.
+ To get approval, submit a patch to
+
+ llvm-commits. When approved you may commit it yourself.
+
You are allowed to commit patches without approval which you think are
+ obvious. This is clearly a subjective decision. We simply expect you to
+ use good judgement. Examples include: fixing build breakage, reverting
+ obviously broken patches, documentation/comment changes, any other minor
+ changes.
+
You are allowed to commit patches without approval to those portions
+ of LLVM that you have contributed or maintain (have been assigned
+ responsibility for), with the proviso that such commits must not break the
+ build. This is a "trust but verify" policy and commits of this nature are
+ reviewed after they are committed.
+
Multiple violations of these policies or a single egregious violation
+ may cause commit access to be revoked.
When making a large change to LLVM, we use a incremental style of
+ development instead of having long-term development branches. Long-term
+ development branches have a number of drawbacks:
+
+
+
Branches must have mainline merged into them periodically. If the branch
+ development and mainline development occur in the same pieces of code,
+ resolving merge conflicts can take a lot of time.
+
Other people in the community tend to ignore work on branches.
+
Huge changes (produced when a branch is merged back onto mainline) are
+ extremely difficult to code review.
+
Branches are not routinely tested by our nightly tester
+ infrastructure.
+
Changes developed as monolithic large changes often don't work until the
+ entire set of changes is done. Breaking it down into a set of smaller
+ changes increases the odds that any of the work will be committed to the
+ main repository.
+
+
+
+ To address these problems, LLVM uses an incremental development style and we
+ require contributors to follow this practice when making a large/invasive
+ change. Some tips:
+
+
+
Large/invasive changes usually have a number of secondary changes that
+ are required before the big change can be made (e.g. API cleanup, etc).
+ These sorts of changes can often be done before the major change is done,
+ independently of that work.
+
The remaining inter-related work should be decomposed into unrelated
+ sets of changes if possible. Once this is done, define the first increment
+ and get consensus on what the end goal of the change is.
+
Increments can be stand alone (e.g. to fix a bug), or part of a planned
+ series of increments towards some development goal.
+
Increments should be kept as small as possible. This simplifies your
+ work (into a logical progression), simplifies code review and reduces the
+ chance that you will get negative feedback on the change. Small increments
+ also facilitate the maintenance of a high quality code base.
+
Often, an independent precursor to a big change is to add a new API and
+ slowly migrate clients to use the new API. Each change to use the new
+ API is often "obvious" and can be committed without review. Once the
+ new API is in place and used, it is often easy to replace the underlying
+ implementation of the API.
+
+
+
If you are interested in making a large change, and this scares you, please
+ make sure to first discuss the change/gather
+ consensus then feel free to ask about the best way to go about making
+ the change.
We believe in correct attribution of contributions to
+ their contributors. However, we do not want the source code to be littered
+ with random attributions (this is noisy/distracting and revision control
+ keeps a perfect history of this anyway). As such, we follow these rules:
+
+
Developers who originate new files in LLVM should place their name at
+ the top of the file per the
+ Coding Standards.
+
There should be only one name at the top of the file and it should be
+ the person who created the file.
+
Placing your name in the file does not imply copyright: it is only used to attribute the file to
+ its original author.
+
Developers should be aware that after some time has passed, the name at
+ the top of a file may become meaningless as maintenance/ownership of files
+ changes. Revision control keeps an accurate history of contributions.
+
Developers should maintain their entry in the
+ CREDITS.txt
+ file to summarize their contributions.
+
Commit comments should contain correct attribution of the person who
+ submitted the patch if that person is not the committer (i.e. when a
+ developer with commit privileges commits a patch for someone else).
This section contains policies that pertain to submitting patches
- to LLVM and committing code to the repository
+
This section describes policies that apply to developers who regularly
+ contribute code to LLVM. As usual, we often accept small patches and
+ contributions that do not follow this policy. In this case, one of the
+ regular contributors has to get the code in shape.
Patches must be made against the CVS HEAD (main development trunk),
not a branch.
-
Patches should be made with this command:
- cvs diff -Ntdup -5
or with the utility utils/mkpatch.
+
Patches should be made with this command:
+
cvs diff -Ntdup -5
+ or with the utility utils/mkpatch.
Patches should not include differences in generated code such as the
code generated by flex, bison or tblgen. The
utils/mkpatch utility takes care of this for you.
-
Patches must not include any patent violations. To the best of our
- knowledge, LLVM is free of any existing patent violations and it is our
- intent to keep it that way.
Before a patch is submitted for review, it should be tested to ensure
- that:
-
-
The patch must compile against the CVS HEAD cleanly (zero warnings, zero
- errors).
-
All the llvm/test (Deja Gnu) tests must pass.
-
The patch should cause no regressions in the llvm-test test suite. How
- much testing is appropriate depends on the nature of the patch. We leave it
- to your good judgement, but you will be responsible for fixing any
- regressions or reverting the patch.
+
Contributions must not knowingly infringe on any patents. To the best of
+ our knowledge, LLVM is free of any existing patent violations and it is our
+ intent to keep it that way.
Granting commit access is at the sole discretion of the LLVM Oversight
- Group.
-
-
Submitting patches to LLVM via the patch policy above will greatly
- increase the chance that your request for commit access is granted. Getting
- to know the members of the LLVM community (email, IRC, in person contact,
- etc.) will also increase your chances.
For those who have recently obtained commit access, the following policies
- apply:
-
-
You are granted commit-after-approval to all parts of LLVM.
- To get approval, submit a patch to
- llvm-commits
- per the patch policies above. When approved you
- may commit it yourself.
-
You are allowed to commit patches without approval which you think are
- obvious. This is clearly a subjective decision. We simply expect you to
- use good judgement.
-
You are allowed to commit patches without approval to those portions
- of LLVM that you own (contributed) or maintain (have been assigned
- responsibility for), with the proviso that such commits must not break the
- build. This is a "trust but verify" policy and commits of this nature are
- reviewed after they are committed.
-
Commits that violate the quality standards may
- be reverted. This is necessary when the change blocks other developers from
- making progress. The developer is welcome to re-commit the change after
- the problem has been fixed.
-
Multiple violations of these policies or a single egregious violation
- may cause commit access to be revoked.
We address here the issues of copyright and license for the LLVM project.
The object of the copyright and license is the LLVM source code and
@@ -347,36 +397,13 @@
terms of its license to LLVM users and developers is the
University of
Illinois/NCSA Open Source License.
-
-
NOTE: This section deals with legal matters but does not provide legal
- advice. It is intended only as a general guideline.
+
NOTE: This section deals with legal matters but does not provide
+ official legal advice. We are not lawyers, please seek legal counsel from an
+ attorney.
The LLVM project believes in correct attribution of contributions to
- their contributors, as follows:
-
-
Developers who originate new files in LLVM should place their name at
- the top of the file per the
- Coding Standards.
-
There should be only one name at the top of the file and it should be
- the person who created the file.
-
Placing your name in the file does not imply copyright but does
- correctly attribute the file to its author.
-
Developers should be aware that after some time has passed, the name at
- the top of a file may become meaningless as maintenance/ownership of files
- changes.
-
Developers should submit or commit patches to the
- CREDITS.txt
- file to summarize their contributions.
-
Commit comments should contain correct attribution of the person who
- submitted the patch if that person is not the committer (i.e. when a
- developer with commit privileges commits a patch for someone else).
-
@@ -384,24 +411,27 @@
For consistency and ease of management, the project requires the
- copyright for all LLVM software to be held by a single copyright holder.
- Although UIUC may assign the copyright of the software to another entity,
- the intent for the project is to always have a single entity hold the copy
- rights to LLVM at any given time.
-
Having multiple copyright holders for various portions of LLVM is
- problematic in the management of the software. Having a single copyright
+ copyright for all LLVM software to be held by a single copyright holder:
+ the University of Illinois (UIUC).
+
+
+ Although UIUC may eventually reassign the copyright of the software to another
+ entity (e.g. a dedicated non-profit "LLVM Organization", or something)
+ the intent for the project is to always have a single entity hold the
+ copyrights to LLVM at any given time.
+
+
We believe that having a single copyright
holder is in the best interests of all developers and users as it greatly
reduces the managerial burden for any kind of administrative or technical
- decisions about LLVM.
LLVM licensing decisions will be made by the LLVM Oversight Group. Any
- issues, comments or suggestions with the licensing should be sent to the
- LLVM Oversight Group.
-
The LLVM Oversight Group intends to keep LLVM perpetually open source
- and to use liberal open source licenses. The current license is the
+
We intend to keep LLVM perpetually open source
+ and to use a liberal open source license. The current license is the
University of Illinois/NCSA Open Source License, which boils
down to this:
@@ -412,22 +442,37 @@
You can't use our names to promote your LLVM derived products.
There's no warranty on LLVM at all.
-
We believe this fosters the widest adoption of LLVM because it allows
- commercial products to be derived from LLVM with few restrictions and
+
+
We believe this fosters the widest adoption of LLVM because it allows
+ commercial products to be derived from LLVM with few restrictions and
without a requirement for making any derived works also open source (i.e.
- LLVM's license is not a copyleft license). We suggest that you read
- the License
+ LLVM's license is not a "copyleft" license like the GPL). We suggest that you
+ read the License
if further clarification is needed.
+
+
Note that the LLVM Project does distribute some code that includes GPL
+ software (notably, llvm-gcc which is based on the GCC GPL source base).
+ This means that anything "linked" into to llvm-gcc must itself be compatible
+ with the GPL, and must be releasable under the terms of the GPL. This implies
+ that you any code linked into llvm-gcc and distributed may be subject to
+ the viral aspects of the GPL. This is not a problem for the main LLVM
+ distribution (which is already licensed under a more liberal license), but may
+ be a problem if you intend to do commercial development without redistributing
+ your source code.
+
+
We have no plans to change the license of LLVM. If you have questions
+ or comments about the license, please contact the LLVM Oversight Group.
With regards to the LLVM copyright and licensing, developers agree to:
-
-
assign their copy rights to UIUC for any contribution made so that
- the entire software base can be managed by a single copyright holder.
-
allow their contribution(s) to be licensed as open source by the then
- current license chosen by the LLVM Oversight Group.
+
With regards to the LLVM copyright and licensing, developers agree to
+ assign their copyrights to UIUC for any contribution made so that
+ the entire software base can be managed by a single copyright holder. This
+ implies that any contributions can be licensed under the license that the
+ project uses.
@@ -456,31 +497,12 @@
patch or commit, that are
related by a single common purpose. Increments are atomic as they
leave LLVM in a stable state (both compiling and working properly).
-