[llvm-dev] [RFC] Script to match open Phabricator reviews with potential reviewers

[Kristof Beyls via llvm-dev]

Hi,

At the last EuroLLVM, I gave a lightning talk about code review
statistics on Phabricator reviews and what we could derive from that
to try and reduce waiting-for-review bottlenecks. (see
https://llvm.org/devmtg/2018-04/talks.html#Lightning_2).

One of the items I pointed to is a script we've been using internally
for a little while to try and match open Phabricator reviews to people
who might be able to review them well. I received quite a few requests
to share that script, so I've decided to do so, see https://reviews.llvm.org/D46192.

The script uses 2 similar heuristics to try and match open reviews with
potential reviewers:

- If there is overlap between the lines of code touched by the
  patch-under-review and lines of code that a person has written, that
  person may be a good reviewer.
- If there is overlap between the files touched by the patch-under-review
  and the source files that a person has made changes to, that person may
  be a good reviewer.

The script provides a percentage for each of the above heuristics and
emails a summary. For example, this morning, I received the following
summary from the script in my inbox for patches-under-review where some
change was made in the past 24 hours:

SUMMARY FOR kristof.beyls at arm.com<mailto:kristof.beyls at arm.com> (found 8 reviews):
[3.37%/41.67%] https://reviews.llvm.org/D46018 '[GlobalISel][IRTranslator] Split aggregates during IR translation' by Amara Emerson
[0.00%/100.00%] https://reviews.llvm.org/D46111 '[ARM] Enable misched for R52.' by Dave Green
[0.00%/50.00%] https://reviews.llvm.org/D45770 '[AArch64] Disable spill slot scavenging when stack realignment required.' by Paul Walker
[0.00%/40.00%] https://reviews.llvm.org/D42759 '[CGP] Split large data structres to sink more GEPs' by Haicheng Wu
[0.00%/25.00%] https://reviews.llvm.org/D45189 '[MachineOutliner][AArch64] Keep track of functions that use a red zone in AArch64MachineFunctionInfo and use that instead of checking for noredzone in the MachineOutliner' by Jessica Paquette
[0.00%/25.00%] https://reviews.llvm.org/D46107 '[AArch64] Codegen for v8.2A dot product intrinsics' by Oliver Stannard
[0.00%/12.50%] https://reviews.llvm.org/D45541 '[globalisel] Update GlobalISel emitter to match new representation of extending loads' by Daniel Sanders
[0.00%/6.25%] https://reviews.llvm.org/D44386 '[x86] Introduce the pconfig/enclv instructions' by Gabor Buella


The first percentage in square brackers is the percentage of lines in
the patch-under-review that changes lines that I wrote. The second
percentage is the percentage of files that I made at least some
changes to out of all of the files touched by the patch-under-review.

Both the script and the heuristics are far from perfect, but I've
heard positive feedback from the few colleagues my script has been
sending a summary to every day - hearing that this does help them to
quickly find patches-under-review they can help to review.

Some more details are at https://reviews.llvm.org/D46192.

I hope that by sharing this, more and better ideas will arise to
automatically match open reviews with people able to review them.

Thanks,

Kristof

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