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

Finkel, Hal J. via llvm-dev llvm-dev at lists.llvm.org
Thu Dec 26 14:45:56 PST 2019

I would like to thank everyone who provided feedback on this thread. I 
attempted to incorporate all of it. If I missed something, please let me 

I've posted a patch to our documentation here: 


On 11/14/19 9:45 PM, Hal Finkel 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 code reviews is both out of date and not as helpful as it could be to 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).
>  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.
>  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
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

More information about the llvm-dev mailing list