llvm/docs/Contributing.rst - llvm-project - Git at Google

 ==================================
 Contributing to LLVM
 ==================================


 Thank you for your interest in contributing to LLVM! There are multiple ways to
 contribute, and we appreciate all contributions. In case you have questions,
 you can either use the `Forum`_ or, for a more interactive chat, go to our
 `Discord server`_ or the IRC #llvm channel on `irc.oftc.net`_.

 If you want to contribute code, please familiarize yourself with the :doc:`DeveloperPolicy`.

 .. contents::
   :local:


 Ways to Contribute
 ==================

 Bug Reports
 -----------
 If you are working with LLVM and run into a bug, we definitely want to know
 about it. Please let us know and follow the instructions in
 :doc:`HowToSubmitABug`  to create a bug report.

 Bug Fixes
 ---------
 If you are interested in contributing code to LLVM, bugs labeled with the
 `good first issue`_ keyword in the `bug tracker`_ are a good way to get familiar with
 the code base. If you are interested in fixing a bug please comment on it to
 let people know you are working on it.

 Then try to reproduce and fix the bug with upstream LLVM. Start by building
 LLVM from source as described in :doc:`GettingStarted` and
 use the built binaries to reproduce the failure described in the bug. Use
 a debug build (`-DCMAKE_BUILD_TYPE=Debug`) or a build with assertions
 (`-DLLVM_ENABLE_ASSERTIONS=On`, enabled for Debug builds).

 Reporting a Security Issue
 --------------------------

 There is a separate process to submit security-related bugs, see :ref:`report-security-issue`.

 Bigger Pieces of Work
 ---------------------
 In case you are interested in taking on a bigger piece of work, a list of
 interesting projects is maintained at the `LLVM's Open Projects page`_. In case
 you are interested in working on any of these projects, please post on the
 `Forum`_, so that we know the project is being worked on.

 .. _submit_patch:

 How to Submit a Patch
 =====================
 Once you have a patch ready, it is time to submit it. The patch should:

 * include a small unit test
 * conform to the :doc:`CodingStandards`. You can use the `clang-format-diff.py`_ or `git-clang-format`_ tools to automatically format your patch properly.
 * not contain any unrelated changes
 * be an isolated change. Independent changes should be submitted as separate patches as this makes reviewing easier.
 * have a single commit (unless stacked on another Differential), up-to-date with the upstream ``origin/main`` branch, and don't have merges.

 .. _format patches:

 Before sending a patch for review, please also try to ensure it is
 formatted properly. We use ``clang-format`` for this, which has git integration
 through the ``git-clang-format`` script. On some systems, it may already be
 installed (or be installable via your package manager). If so, you can simply
 run it -- the following command will format only the code changed in the most
 recent commit:

 .. code-block:: console

   % git clang-format HEAD~1

 Note that this modifies the files, but doesn't commit them -- you'll likely want
 to run

 .. code-block:: console

   % git commit --amend -a

 in order to update the last commit with all pending changes.

 .. note::
   If you don't already have ``clang-format`` or ``git clang-format`` installed
   on your system, the ``clang-format`` binary will be built alongside clang, and
   the git integration can be run from
   ``clang/tools/clang-format/git-clang-format``.

 The LLVM project has migrated to GitHub Pull Requests as its review process.
 For more information about the workflow of using GitHub Pull Requests see our
 :ref:`GitHub <github-reviews>` documentation. We still have an read-only
 `LLVM's Phabricator <https://reviews.llvm.org>`_ instance.

 To make sure the right people see your patch, please select suitable reviewers
 and add them to your patch when requesting a review. Suitable reviewers are the
 code owner (see CODE_OWNERS.txt) and other people doing work in the area your
 patch touches. Github will normally suggest some reviewers based on rules or
 people that have worked on the code before. If you are a new contributor, you
 will not be able to select reviewers in such a way, in which case you can still
 get the attention of potential reviewers by CC'ing them in a comment -- just
 @name them.

 A reviewer may request changes or ask questions during the review. If you are
 uncertain on how to provide test cases, documentation, etc., feel free to ask
 for guidance during the review. Please address the feedback and re-post an
 updated version of your patch. This cycle continues until all requests and comments
 have been addressed and a reviewer accepts the patch with a `Looks good to me` or `LGTM`.
 Once that is done the change can be committed. If you do not have commit
 access, please let people know during the review and someone should commit it
 on your behalf.

 If you have received no comments on your patch for a week, you can request a
 review by 'ping'ing the GitHub PR with "Ping". The common courtesy 'ping' rate
 is once a week. Please remember that you are asking for valuable time from other
 professional developers.

 For more information on LLVM's code-review process, please see :doc:`CodeReview`.

 .. _commit_from_git:

 For developers to commit changes from Git
 -----------------------------------------

 Once a patch is reviewed, you can select the "Squash and merge" button in the
 GitHub web interface. You might need to rebase your change before pushing
 it to the repo.

 LLVM currently has a linear-history policy, which means that merge commits are
 not allowed. The `llvm-project` repo on github is configured to reject pushes
 that include merges, so the `git rebase` step above is required.

 Please ask for help if you're having trouble with your particular git workflow.

 .. _git_pre_push_hook:

 Git pre-push hook
 ^^^^^^^^^^^^^^^^^

 We include an optional pre-push hook that run some sanity checks on the revisions
 you are about to push and ask confirmation if you push multiple commits at once.
 You can set it up (on Unix systems) by running from the repository root:

 .. code-block:: console

   % ln -sf ../../llvm/utils/git/pre-push.py .git/hooks/pre-push

 Helpful Information About LLVM
 ==============================
 :doc:`LLVM's documentation <index>` provides a wealth of information about LLVM's internals as
 well as various user guides. The pages listed below should provide a good overview
 of LLVM's high-level design, as well as its internals:

 :doc:`GettingStarted`
    Discusses how to get up and running quickly with the LLVM infrastructure.
    Everything from unpacking and compilation of the distribution to execution
    of some tools.

 :doc:`LangRef`
   Defines the LLVM intermediate representation.

 :doc:`ProgrammersManual`
   Introduction to the general layout of the LLVM sourcebase, important classes
   and APIs, and some tips & tricks.

 `LLVM for Grad Students`__
   This is an introduction to the LLVM infrastructure by Adrian Sampson. While it
   has been written for grad students, it provides  a good, compact overview of
   LLVM's architecture, LLVM's IR and how to write a new pass.

   .. __: http://www.cs.cornell.edu/~asampson/blog/llvm.html

 `Intro to LLVM`__
   Book chapter providing a compiler hacker's introduction to LLVM.

   .. __: http://www.aosabook.org/en/llvm.html

 .. _Forum: https://discourse.llvm.org
 .. _Discord server: https://discord.gg/xS7Z362
 .. _irc.oftc.net: irc://irc.oftc.net/llvm
 .. _good first issue: https://github.com/llvm/llvm-project/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22
 .. _bug tracker: https://github.com/llvm/llvm-project/issues
 .. _clang-format-diff.py: https://reviews.llvm.org/source/llvm-github/browse/main/clang/tools/clang-format/clang-format-diff.py
 .. _git-clang-format: https://reviews.llvm.org/source/llvm-github/browse/main/clang/tools/clang-format/git-clang-format
 .. _LLVM's GitHub: https://github.com/llvm/llvm-project
 .. _LLVM's Phabricator (read-only): https://reviews.llvm.org/
 .. _LLVM's Open Projects page: https://llvm.org/OpenProjects.html#what
	==================================
	Contributing to LLVM
	==================================


	Thank you for your interest in contributing to LLVM! There are multiple ways to
	contribute, and we appreciate all contributions. In case you have questions,
	you can either use the `Forum`_ or, for a more interactive chat, go to our
	`Discord server`_ or the IRC #llvm channel on `irc.oftc.net`_.

	If you want to contribute code, please familiarize yourself with the :doc:`DeveloperPolicy`.

	.. contents::
	:local:


	Ways to Contribute
	==================

	Bug Reports
	-----------
	If you are working with LLVM and run into a bug, we definitely want to know
	about it. Please let us know and follow the instructions in
	:doc:`HowToSubmitABug` to create a bug report.

	Bug Fixes
	---------
	If you are interested in contributing code to LLVM, bugs labeled with the
	`good first issue`_ keyword in the `bug tracker`_ are a good way to get familiar with
	the code base. If you are interested in fixing a bug please comment on it to
	let people know you are working on it.

	Then try to reproduce and fix the bug with upstream LLVM. Start by building
	LLVM from source as described in :doc:`GettingStarted` and
	use the built binaries to reproduce the failure described in the bug. Use
	a debug build (`-DCMAKE_BUILD_TYPE=Debug`) or a build with assertions
	(`-DLLVM_ENABLE_ASSERTIONS=On`, enabled for Debug builds).

	Reporting a Security Issue
	--------------------------

	There is a separate process to submit security-related bugs, see :ref:`report-security-issue`.

	Bigger Pieces of Work
	---------------------
	In case you are interested in taking on a bigger piece of work, a list of
	interesting projects is maintained at the `LLVM's Open Projects page`_. In case
	you are interested in working on any of these projects, please post on the
	`Forum`_, so that we know the project is being worked on.

	.. _submit_patch:

	How to Submit a Patch
	=====================
	Once you have a patch ready, it is time to submit it. The patch should:

	* include a small unit test
	* conform to the :doc:`CodingStandards`. You can use the `clang-format-diff.py`_ or `git-clang-format`_ tools to automatically format your patch properly.
	* not contain any unrelated changes
	* be an isolated change. Independent changes should be submitted as separate patches as this makes reviewing easier.
	* have a single commit (unless stacked on another Differential), up-to-date with the upstream ``origin/main`` branch, and don't have merges.

	.. _format patches:

	Before sending a patch for review, please also try to ensure it is
	formatted properly. We use ``clang-format`` for this, which has git integration
	through the ``git-clang-format`` script. On some systems, it may already be
	installed (or be installable via your package manager). If so, you can simply
	run it -- the following command will format only the code changed in the most
	recent commit:

	.. code-block:: console

	% git clang-format HEAD~1

	Note that this modifies the files, but doesn't commit them -- you'll likely want
	to run

	.. code-block:: console

	% git commit --amend -a

	in order to update the last commit with all pending changes.

	.. note::
	If you don't already have ``clang-format`` or ``git clang-format`` installed
	on your system, the ``clang-format`` binary will be built alongside clang, and
	the git integration can be run from
	``clang/tools/clang-format/git-clang-format``.

	The LLVM project has migrated to GitHub Pull Requests as its review process.
	For more information about the workflow of using GitHub Pull Requests see our
	:ref:`GitHub <github-reviews>` documentation. We still have an read-only
	`LLVM's Phabricator <https://reviews.llvm.org>`_ instance.

	To make sure the right people see your patch, please select suitable reviewers
	and add them to your patch when requesting a review. Suitable reviewers are the
	code owner (see CODE_OWNERS.txt) and other people doing work in the area your
	patch touches. Github will normally suggest some reviewers based on rules or
	people that have worked on the code before. If you are a new contributor, you
	will not be able to select reviewers in such a way, in which case you can still
	get the attention of potential reviewers by CC'ing them in a comment -- just
	@name them.

	A reviewer may request changes or ask questions during the review. If you are
	uncertain on how to provide test cases, documentation, etc., feel free to ask
	for guidance during the review. Please address the feedback and re-post an
	updated version of your patch. This cycle continues until all requests and comments
	have been addressed and a reviewer accepts the patch with a `Looks good to me` or `LGTM`.
	Once that is done the change can be committed. If you do not have commit
	access, please let people know during the review and someone should commit it
	on your behalf.

	If you have received no comments on your patch for a week, you can request a
	review by 'ping'ing the GitHub PR with "Ping". The common courtesy 'ping' rate
	is once a week. Please remember that you are asking for valuable time from other
	professional developers.

	For more information on LLVM's code-review process, please see :doc:`CodeReview`.

	.. _commit_from_git:

	For developers to commit changes from Git
	-----------------------------------------

	Once a patch is reviewed, you can select the "Squash and merge" button in the
	GitHub web interface. You might need to rebase your change before pushing
	it to the repo.

	LLVM currently has a linear-history policy, which means that merge commits are
	not allowed. The `llvm-project` repo on github is configured to reject pushes
	that include merges, so the `git rebase` step above is required.

	Please ask for help if you're having trouble with your particular git workflow.

	.. _git_pre_push_hook:

	Git pre-push hook
	^^^^^^^^^^^^^^^^^

	We include an optional pre-push hook that run some sanity checks on the revisions
	you are about to push and ask confirmation if you push multiple commits at once.
	You can set it up (on Unix systems) by running from the repository root:

	.. code-block:: console

	% ln -sf ../../llvm/utils/git/pre-push.py .git/hooks/pre-push

	Helpful Information About LLVM
	==============================
	:doc:`LLVM's documentation <index>` provides a wealth of information about LLVM's internals as
	well as various user guides. The pages listed below should provide a good overview
	of LLVM's high-level design, as well as its internals:

	:doc:`GettingStarted`
	Discusses how to get up and running quickly with the LLVM infrastructure.
	Everything from unpacking and compilation of the distribution to execution
	of some tools.

	:doc:`LangRef`
	Defines the LLVM intermediate representation.

	:doc:`ProgrammersManual`
	Introduction to the general layout of the LLVM sourcebase, important classes
	and APIs, and some tips & tricks.

	`LLVM for Grad Students`__
	This is an introduction to the LLVM infrastructure by Adrian Sampson. While it
	has been written for grad students, it provides a good, compact overview of
	LLVM's architecture, LLVM's IR and how to write a new pass.

	.. __: http://www.cs.cornell.edu/~asampson/blog/llvm.html

	`Intro to LLVM`__
	Book chapter providing a compiler hacker's introduction to LLVM.

	.. __: http://www.aosabook.org/en/llvm.html

	.. _Forum: https://discourse.llvm.org
	.. _Discord server: https://discord.gg/xS7Z362
	.. _irc.oftc.net: irc://irc.oftc.net/llvm
	.. _good first issue: https://github.com/llvm/llvm-project/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22
	.. _bug tracker: https://github.com/llvm/llvm-project/issues
	.. _clang-format-diff.py: https://reviews.llvm.org/source/llvm-github/browse/main/clang/tools/clang-format/clang-format-diff.py
	.. _git-clang-format: https://reviews.llvm.org/source/llvm-github/browse/main/clang/tools/clang-format/git-clang-format
	.. _LLVM's GitHub: https://github.com/llvm/llvm-project
	.. _LLVM's Phabricator (read-only): https://reviews.llvm.org/
	.. _LLVM's Open Projects page: https://llvm.org/OpenProjects.html#what