[llvm-dev] LLVM Weekly - #417, December 27th 2021

[Alex Bradbury via llvm-dev]

LLVM Weekly - #417, December 27th 2021
======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/417>.

Welcome to the four hundred and seventeenth 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

Videos from the 2021 LLVM Developers' Meeting have [are starting to be posted
online](https://www.youtube.com/playlist?list=PL_R5A0lGi1AATJX6-tY7IkYjpRjv30ziN).

The call for papers for the FOSDEM 2022 LLVM devroom [has been
extended](https://lists.llvm.org/pipermail/llvm-dev/2021-December/154435.html)
to the 28th of December.


## On the mailing lists

* Y Song wrote up [the reasoning for adding Clang extensions to support BPF
  CO-RE](https://lists.llvm.org/pipermail/cfe-dev/2021-December/069635.html).
  Although the feature has already been implemented and merged, the write-up
  steps through each of the agreed criteria for justifying Clang extensions.

* Y Song proposed [adding a new bpf_dominating_decl
  attribute](https://lists.llvm.org/pipermail/cfe-dev/2021-December/069636.html).

* Nikita Ermoshkin asked a series of questions about [submitting an
  experimental target for the Propeller 2
  microcontroller](https://lists.llvm.org/pipermail/llvm-dev/2021-December/154478.html).

* Nuno Lopes [shared his
  thoughts](https://lists.llvm.org/pipermail/llvm-dev/2021-December/154457.html)
  on the RFC to add a new memory region declaration intrinsic.


## LLVM commits

* A new llvm-mca-compare.py script was added, using llvm-mca to print
  and compare statistics for multiple files.
  [0e34347](https://reviews.llvm.org/rG0e343479a7ea).

* The `no_cfi` constant was introduced, representing a function reference that
  doesn't get replaced with a reference to the CFI jump table. This may be
  used in low-level programs such as OS kernels.
  [5dc8aaa](https://reviews.llvm.org/rG5dc8aaac39c5).

* The areFunctionArgsABICompatible TargetTransformInfo hook has been replaced
  with a new areTypesABICompatible hook, which is designed to be compatible
  with opaque pointer types, giving a list of types rather than pointer
  arguments (that must be inspected).
  [f5ac23b](https://reviews.llvm.org/rGf5ac23b5ae09).

* VE support was added to update_llc_test_checks.py.
  [2810c34](https://reviews.llvm.org/rG2810c3403e42).

* Strict FP conversion operations are now supported for RISC-V.
  [b7b260e](https://reviews.llvm.org/rGb7b260e19a74).

* The Hexagon backend gained support for the Hexagon v69 ISA.
  [f766bc0](https://reviews.llvm.org/rGf766bc093c8c).


## Clang commits

* The `__builtin_function_start` builtin was added. It accepts an argument
  that can be constant-evaluated to a function and returns the address of the
  function body. [9fa15e0](https://reviews.llvm.org/rG9fa15e0073b9).

* A SPIR-V toolchain was defined.
  [0045d01](https://reviews.llvm.org/rG0045d01af96f).

* A new sugar 'Type' AST node was added representing types accessed via a C++
  `using` declaration. [e1600db](https://reviews.llvm.org/rGe1600db19d63).


## Other project commits

* LLVM's libc now implements a modified form of the Eisel-Lemire algorithm for
  converting from strings to long doubles.
  [9b39737](https://reviews.llvm.org/rG9b39737129f5).

* A helper class, `__transaction`, was added to libcxx to help write code with
  the strong exception guarantee.
  [37e6bd8](https://reviews.llvm.org/rG37e6bd8bc8da).

* A new CMake option was added to enable installation of libunwind headers.
  [1c4867e](https://reviews.llvm.org/rG1c4867e6fc50).

* Support was added for using libkvm with LLDB on FreeBSD.
  [fb78587](https://reviews.llvm.org/rGfb785877a95d).