[llvm-dev] LLVM Weekly - #404, September 27th 2021

Mon Sep 27 12:08:54 PDT 2021

LLVM Weekly - #404, September 27th 2021
=======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/404>.

Welcome to the four hundred and fourth 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

Michał Górny blogged about [improving GDB register model compatibility with
LLDB](https://www.moritz.systems/blog/improving-gdb-register-model-compatibility-in-lldb/).

The next Women in Compilers and Tools meetup will [take place on September
31st](https://www.meetup.com/meetup-group-ifwtlvwd/events/280793876/) (or
early morning October 1st for those in European timezones!). It will feature
and interview with Teresa Johnson, Senior Staff Engineer at Google and an
active contributor to the LLVM open source project.

The [call for proposals](https://llvm.org/devmtg/2021-11/#cfp) for the 2021
LLVM Developers' Meeting closes today (Sep 27th) at 5pm PDT.

## On the mailing lists

* Discussion [has
  continued](https://lists.llvm.org/pipermail/cfe-dev/2021-September/068992.html)
  on the suggestion to have clang clear the AST before running backed
  optimisations. David Blaikie suggests making it the default mode going
  forwards to ensure new features don't accidentally become dependent on
  access to the AST.

* Jayson Yan [proposed adding warnings to Clang against the use of the `%n`
  format string
  specifier](https://lists.llvm.org/pipermail/cfe-dev/2021-September/068986.html).

* Noah Shutty kicked off a discussion on [moving some LLDB libraries into the
  core LLVM
  project](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152909.html),
  e.g. TCPSocket and the IOObject hierarchy.

* Jonas Devlieghere wrote to the LLDB list to [update on LLDB
  reproducers](https://lists.llvm.org/pipermail/lldb-dev/2021-September/017045.html).
  As they will require a non-trivial investment to reach production quality
  and there isn't bandwidth for this, Jonas proposes transforming them into
  something resembling sysdiagnose on Apple platforms "an archive containing a
  variety of information to help diagnose a bug, but without the machinery to
  automatically reproduce the bug".

* LLVM 13.0.0-rc4 [has been
  tagged](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152932.html).

* LLVM GPU News issue 20 [is out
  now](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152945.html).

## LLVM commits

* The MergeICmps transformation was updated so it won't reorder unmerged
  comparisons. This change addresses correctness issues.
  [f2fa6ad](https://reviews.llvm.org/rGf2fa6ad0476b).

* Support was added for Armv8.4 Large System Extension 2 atomicity rules.
  [13aa102](https://reviews.llvm.org/rG13aa102e0769).

* The GlobalISel legalizer's `eraseInstr` utility function will delete
  trivially dead users after deleting an instruction.
  [e4c46dd](https://reviews.llvm.org/rGe4c46ddd91eb).

* A new RISCVGatherScatterLowering pass was added to help recognise vector
  length specified strided loads/stores from gather/scatter.
  [d85e347](https://reviews.llvm.org/rGd85e347a28dc).

* The commit to allow rematerialisation of virtual register uses was reverted.
  [08d7eec](https://reviews.llvm.org/rG08d7eec06e8c).

* The export.sh script was extended to allow the creation of source tarballs
  for unreleased or untagged code.
  [6deaebe](https://reviews.llvm.org/rG6deaebe5fe00).

## Clang commits

* clang-format gained the ability to reorder const/volatile qualifiers on
  either the left or the right.
  [a44ab17](https://reviews.llvm.org/rGa44ab1702539).

* `-Wunused-value` warnings are now diagnosed based on CFG reachability.
  [cbbf2e8](https://reviews.llvm.org/rGcbbf2e8c8ae7).
  REVERTED

* clang-offload-bundler documentation was expanded.
  [ee31ad0](https://reviews.llvm.org/rGee31ad0ab5f7).

* RISC-V vector intrinsics now have a tail policy argument.
  [7afa61e](https://reviews.llvm.org/rG7afa61e71877).

## Other project commits

* LLVM's libc gained implementations of div, ldiv, lldiv, imadiv, bsearch, and
  qsort. [74670e7](https://reviews.llvm.org/rG74670e79b0a0),
  [32a5007](https://reviews.llvm.org/rG32a50078657d),
  [5eb6b82](https://reviews.llvm.org/rG5eb6b8272931).

* A basic C REPL was added to the LLDB code base in order to act as a test
  case for LLDB's REPL infrastructure.
  [c223299](https://reviews.llvm.org/rGc22329972f02).

* Polly added support for user-direct loop distribution/fission.
  [e470f92](https://reviews.llvm.org/rGe470f9268a44).

* `--why-extract` was added to LLD's ELF linker to query why archive members
  or lazy object files are extracted.
  [a954bb1](https://reviews.llvm.org/rGa954bb18b143).