[llvm-dev] [RFC] High-Level Code-Review Documentation Update

Mehdi AMINI via llvm-dev llvm-dev at lists.llvm.org
Sat Nov 16 17:56:37 PST 2019

+1 in general, and Philip has good suggestions as well!


On Sat, Nov 16, 2019 at 8:37 AM Philip Reames via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> + 1 in general, a couple of suggestions
> On 11/14/19 7:46 PM, Finkel, Hal J. via llvm-dev wrote:
> > Hi, everyone,
> >
> > I've been fielding an increasing number of questions about how our
> > code-review process in LLVM works from people who are new to our
> > community, and it's been pointed out to me that our documentation on
> > code reviews is both out of date and not as helpful as it could be to
> > new developers.
> >
> >    http://llvm.org/docs/DeveloperPolicy.html#code-reviews
> >
> > I would like to compose a patch to update this, but before I do that, I
> > want to highlight some of my thoughts to get feedback. My intent is to
> > capture our community best practices in writing so that people new to
> > our community understand our processes and expectations. Here are some
> > things that I would like to capture:
> >
> >   1. You do not need to be an expert in some area of the compiler to
> > review patches; it's fine to ask questions about what some piece of code
> > is doing. If it's not clear to you what is going on, you're unlikely to
> > be the only one. Extra comments and/or test cases can often help (and
> > asking for comments in the test cases is fine as well).
> Authors are encouraged to interpret questions as reasons to reexamine
> the readability of the code in question.  Structural changes, or further
> comments may be appropriate.
> >
> >   2. If you review a patch, but don't intend for the review process to
> > block on your approval, please state that explicitly. Out of courtesy,
> > we generally wait on committing a patch until all reviewers are
> > satisfied, and if you don't intend to look at the patch again in a
> > timely fashion, please communicate that fact in the review.
> >
> >   3. All comments by reviewers should be addressed by the patch author.
> > It is generally expected that suggested changes will be incorporated
> > into the next revision of the patch unless the author and/or other
> > reviewers can articulate a good reason to do otherwise (and then the
> > reviewers must agree). If you suggest changes in a code review, but
> > don't wish the suggestion to be interpreted this strongly, please state
> > so explicitly.
> >
> >   4. Reviewers may request certain aspects of a patch to be broken out
> > into separate patches for independent review, and also, reviewers may
> > accept a patch conditioned on the author providing a follow-up patch
> > addressing some particular issue or concern (although no committed patch
> > should leave the project in a broken state). Reviewers can also accept a
> > patch conditioned on the author applying some set of minor updates prior
> > to committing, and when applicable, it is polite for reviewers to do so.
> >
> >   5. Aim to limit the number of iterations in the review process. For
> > example, when suggesting a change, if you want the author to make a
> > similar set of changes at other places in the code, please explain the
> > requested set of changes so that the author can make all of the changes
> > at once. If a patch will require multiple steps prior to approval (e.g.,
> > splitting, refactoring, posting data from specific performance tests),
> > please explain as many of these up front as possible. This allows the
> > patch author to make the most-efficient use of his or her time.
> If the path forward is not clear - because the patch is too large to
> meaningful review, or direction needs to be settled - it is fine to
> suggest a clear next step (e.g. landing a refactoring) followed by a
> re-review.  Please state explicitly if the path forward is unclear to
> prevent confusions on the part of the author.
> >
> >   6. Some changes are too large for just a code review. Changes that
> > should change the Language Reference (e.g., adding new
> > target-independent intrinsics), adding language extensions in Clang, and
> > so on, require an RFC on *-dev first. For changes that promise
> > significant impact on users and/or downstream code bases, reviewers can
> > request an RFC (Request for Comment) achieving consensus before
> > proceeding with code review. That having been said, posting initial
> > patches can help with discussions on an RFC.
> >
> > Lastly, the current text reads, "Code reviews are conducted by email on
> > the relevant project’s commit mailing list, or alternatively on the
> > project’s development list or bug tracker.", and then only later
> > mentions Phabricator. I'd like to move Phabricator to be mentioned on
> > this line before the other methods.
> >
> > Please let me know what you think.
> >
> > Thanks again,
> >
> > Hal
> A couple of additional things:
> Only a single LGTM is required.  Reviewers are expected to only LGTM
> patches they're confident in their knowledge of.  Reviewers may review
> and provide suggestions, but explicitly defer LGTM to someone else.
> This is encouraged and a good way for new contributors to learn the code.
> There is a cultural expectation that at least one reviewer is from a
> different organization than the author of the patch.  If that's not
> possible, care should be taken to ensure overall direction has been
> widely accepted.
> Post commit review is encouraged via either phabricator or email.  There
> is a strong expectation that authors respond promptly to post commit
> feedback and address it.  Failure to do so is cause for the patch to be
> reverted.  If substantial problems are identified, it is expected that
> the patch is reverted, fixed offline, and then recommitted (possibly
> after further review.)
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