[llvm-dev] LLVM Weekly - #412, November 22nd 2021

[Alex Bradbury via llvm-dev]

LLVM Weekly - #412, November 22nd 2021
======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/412>.

Welcome to the four hundred and twelfth 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

On the LLVM blog, Kristof Beyls provided an [update on the LLVM relicensing
effort](https://blog.llvm.org/posts/2021-11-18-relicensing-update/) along with
a call for help for closing off the "long tail" of contributions that haven't
yet been explicitly relicensed. Over 94% of all contributed lines of code have
been made available under the new license (Apache-2.0 with LLVM exception).

The 2021 LLVM Developers Meeting took place online last week. Videos [will be
posted](https://twitter.com/llvmorg/status/1461851531368615937) in the next
few weeks.


## On the mailing lists

* Anton Korebeynikov shared a [major update on the LLVM bugzilla
  migration](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153802.html).
  Assuming the proposed migration roadmap goes to plan, the LLVM GitHub repo
  should be open for new issues and have ingested all previous BugZilla issues
  on Monday November 29th.

* Yitzhak Mandelbaum [shared an update on the proposed dataflow analysis
  framework for the Clang
  AST](https://lists.llvm.org/pipermail/cfe-dev/2021-November/069357.html),
  linking to the first two patches.

* Gábor Horváth provided [notes from the Clang Static Analyzer round table
  discussion](https://lists.llvm.org/pipermail/cfe-dev/2021-November/069352.html).

* Momchil Velikov kicked off an RFC discussion on [introducing an LLVM IR
  attribute for asynchronous unwind
  tables](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153768.html),
  noting that while there's a 'uwtable' attribute, there's no attribute to
  indicate if the unwind tables should be asynchronous or not.

* Jeroen Dobbelaere posted an RFC on [introducing an 'unknown_provenance' LLVM
  IR
  constant](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153772.html),
  intended to be used as part of the ptr_provenance infrastructure used to
  implement full restrict support.

* Joshua Cranmer posted a [new proposal for introducing complex types into
  LLVM](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153793.html).
  Rather than introducing complex types directly, it proposes representing
  complex numbers as vectors and using intrinsics. This was shared ahead of an
  LLVM Dev Meeting roundtable discussion on the topic.

* Serge Guelton suggests [improving LLVM's handling of string IR
  attributes](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153773.html).
  Noting that freeform key=value attribuees are commonly used for relatively
  standard cases like "target-cpu" or "target-features", Serge proposes
  introducing private symbols to represent such common keys.

* Ying Yi provided an [update on the "Program Repository"
  project](https://lists.llvm.org/pipermail/llvm-dev/2021-November/153740.html).


## LLVM commits

* A constant value consecutive store-merging optimisation pass was added to
  GlobalISel and enabled for AArch64.
  [dc84770](https://reviews.llvm.org/rGdc84770d559b).

* The RISCVCompressEmitter tablegen backend was modified and renamed to
  CompressInstEmitter, so it can be reused for compressed instruction emission
  for the CSKY target. [24d1673](https://reviews.llvm.org/rG24d1673c8b9b).

* The PPC backend gained a peephole optimisation for conditional trap
  instructions. [ae27ca9](https://reviews.llvm.org/rGae27ca9a6783).


## Clang commits

* A tutorial was added on how to write a source-to-source translation tool
  using Clang Transformer. [2b49484](https://reviews.llvm.org/rG2b4948448f03).

* The `-masm=intel` flag now affects the inline asm style.
  [ae98182](https://reviews.llvm.org/rGae98182cf734).


## Other project commits

* LLVM's DenseMap was imported into and modified for use in compiler-rt
  sanitizers. [54adc16](https://reviews.llvm.org/rG54adc1675eb8),
  [c26dbc4a](https://reviews.llvm.org/rGc26dbc4ab4b8).

* libcxx's coroutine implementation was moved out of the std::experimental
  namespace. [2e6ae1d](https://reviews.llvm.org/rG2e6ae1d3f2de).

* libcxx's std::sort now uses introsort to avoid O(n^2) behaviour on
  adversarial inputs. [7f28739](https://reviews.llvm.org/rG7f287390d78d).

* libunwind gained an interface for dynamic .eh_frame registration.
  [bab3981](https://reviews.llvm.org/rGbab39816085d).

* Documentation for MLIR's shape dialect was expanded.
  [0d0c46a](https://reviews.llvm.org/rG0d0c46a35b3b).