[llvm-dev] LLVM Weekly - #419, January 10th 2022

Alex Bradbury via llvm-dev llvm-dev at lists.llvm.org
Mon Jan 10 11:40:49 PST 2022 

LLVM Weekly - #419, January 10th 2022
=====================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/419>.

Welcome to the four hundred and nineteenth issue of LLVM Weekly, a weekly
newsletter (published every Monday) covering developments in LLVM, Clang, and
related projects. LLVM Weekly is brought to you by [Alex
Bradbury](https://www.linkedin.com/in/alex-bradbury/). Subscribe to future
issues at <http://llvmweekly.org> and pass it on to anyone else you think may
be interested. Please send any tips or feedback to <asb at asbradbury.org>, or
@llvmweekly or @asbradbury on Twitter.


## News and articles from around the web

Even more recordings from the 2021 LLVM Developers' Meeting [are now
available](https://www.youtube.com/playlist?list=PL_R5A0lGi1AATJX6-tY7IkYjpRjv30ziN).
A [tutorial on ORCv2 from the
meeting](https://www.youtube.com/watch?v=i-inxFudrgI) has also been published.

Arseny Kapoulkine [blogged about Proebsting's
Law](https://zeux.io/2022/01/08/on-proebstings-law/), putting it to test using
LLVM and Clang (is it really the case that compiler advances double computing
power every 18 years?). The overall conclusion was "LLVM 11 tends to take 2x
longer to compile code with optimizations, and as a result produces code that
runs 10-20% faster (with occasional outliers in either direction), compared to
LLVM 2.7 which is more than 10 years old."


## On the mailing lists

* Tanya Lattner posted about [LLVM's move to
  Discourse](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154582.html).
  There is also an [accompanying blog
  post](https://blog.llvm.org/posts/2022-01-07-moving-to-discourse/) and
  [migration guide](https://llvm.org/docs/DiscourseMigrationGuide.html). In
  the posted timeline, the mailing lists will be put into read-only mode from
  February 1st and the archives migrated into Discourse between January 10th
  and January 20th. People are encouraged to use Discourse rather than the
  mailing list from January 10th onwards. This might be the last LLVM Weekly
  posted to llvm-dev. Remember, you can always [subscribe at
  llvmweekly.org](https://llvmweekly.org/) too.

* Tom Stellard shared that [a system is now in place for subscribing to GitHub
  issue
  labels](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154537.html).
  Simply request membership of the appropriate issue-subscribers-$LABEL_NAME
  team. As discussed in the thread, it's not immediately obvious where to find
  the "Request to join button". You need to click on the team, then click
  "Members", then you'll see the necessary button.

* Augie Fackler posted an RFC on [adding support for marking allocator
  functions in LLVM
  IR](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154599.html). The
  intent is to better support languages like Rust that have allocator
  functions with symbol names that aren't recognised by LLVM as the libc
  allocator functions are. This generated a fair amount of discussion, for
  instance [this question from Philip
  Reames](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154557.html).

* Stella Stamenova kicked off a discussion about [the responsibilities of a
  buildbot
  owner](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154587.html),
  especially around where responsibility lies when there are flaky tests.

* Anastasia Stulova posted an RFC on [supporting linking of SPIR-V object
  files using spirv-link from the SPIRV-Tools
  project](https://lists.llvm.org/pipermail/cfe-dev/2022-January/069658.html).

* Stefan Gränitz provided an [overview of missing RISC-V functionality in
  LLVM's JIT
  libraries](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154517.html).

* Serge Guelton [advertised an upcoming change to the AttrBuilder
  API](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154549.html)
  intended to reduce the performance overhead.

* Tom Stellard [updated on the status of the 13.0.1
  release](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154586.html),
  noting rc2 is due on Monday (today) and will hopefully be the last release
  candidate.

* Kito Cheng and Jessica Clarke [invited the LLVM community to review v1.0-rc1
  of the RISC-V
  psABI](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154599.html).
  As noted in the email, this release is intended to mark a stable milestone,
  but future backwards-compatible changes or wording improvements will still
  be accepted and incorporated into future releases.

* Tom Stellard picked up an old thread on automating releases with a [tweaked
  suggestion](https://lists.llvm.org/pipermail/llvm-dev/2022-January/154583.html),
  proposing that testers upload directly to GitHub (and also email the sha512
  hash), and Tom later signs the binaries.


## LLVM commits

* MC layer support was added for the armv8.8-a hinted branch instruction and
  memcpy/memset acceleration instructions.
  [8c1e520](https://reviews.llvm.org/rG8c1e520c903e),
  [e35a3f1](https://reviews.llvm.org/rGe35a3f188f6a).

* As part of the opaque pointer type transition, indirect inline asm operands
  now take an elementtype attribute.
  [8484bab](https://reviews.llvm.org/rG8484bab9cd5e),
  [f430c1e](https://reviews.llvm.org/rGf430c1eb6443),
  [eddd5be](https://reviews.llvm.org/rGeddd5be1df06).

* Codegen for select/br/cmp as well as frame lowering infrastructure was added
  to the CSKY backend. [9566cf1](https://reviews.llvm.org/rG9566cf16ad39).

* A new pass was added to the RISC-V backend to replace redundant sext.w
  instructions with copies on RV64.
  [56ca11e](https://reviews.llvm.org/rG56ca11e31e6a).

* A Discourse migration guide was committed.
  [645c845](https://reviews.llvm.org/rG645c845d45ae).


## Clang commits

* clang-format now accepts an option to explicitly specify a configuration
  file. [b9e173f](https://reviews.llvm.org/rGb9e173fcd46b).

* `__builtin_trap` and `__builtin_debugtrap` were documented.
  [491984c](https://reviews.llvm.org/rG491984c4e60c).


## Other project commits

* `std::basic_string::resize_and_overwrite` was implemented in libcxx.
  [bec50db](https://reviews.llvm.org/rGbec50db2edf6).

* Using llvm-config to detect the LLVM installation is now deprecated in LLD's
  CMake build system. [a1da5f3](https://reviews.llvm.org/rGa1da5f3c2d65).

* Summary formatters were added to LLDB for libcxx std::string_view.
  [7244e9c](https://reviews.llvm.org/rG7244e9c2f5f3).

* LLDB's data formatter documentation was expanded.
  [69c8e64](https://reviews.llvm.org/rG69c8e64ba6be).

* A script was added to run clang-tidy on the whole MLIR codebase.
  [590a62d](https://reviews.llvm.org/rG590a62d1b253).

* C and Python bindings were added for the MLIR quantization dialect types.
  [9bcf13b](https://reviews.llvm.org/rG9bcf13bf3e63),
  [66d4090](https://reviews.llvm.org/rG66d4090d9b15).

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