[llvm-dev] LLVM Weekly - #362, December 7th 2020

[Alex Bradbury via llvm-dev]

LLVM Weekly - #362, December 7th 2020
=====================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/362>.

Welcome to the three hundred and sixty-second 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

A couple more videos from the 2020 LLVM Developers' Meeting were added to the
[YouTube channel](https://www.youtube.com/channel/UCv2_41bSAa5Y_8BacJUZfjQ).


## On the mailing lists

* Mike Edwards [provided an update on the transition to the 'main'
branch](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147053.html),
linking to the [LLVM Foundation page on the
transition](https://foundation.llvm.org/docs/branch-rename/).

* There's been substantial new discussion on the RFC about `SVec<T>` and
`Vec<T>` convenience wrappers. Chris Lattner [summarises the parallel
discussions taking place in this
thread](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147006.html).

* Tom Stellard explained [how to disable GitHub Action
notifications](http://lists.llvm.org/pipermail/llvm-dev/2020-November/146953.html),
noting people may be getting notifications due to an action being introduced
to help with the transition to the 'main' branch name.

* Nikita Popov [proposes changing the LLVM coding style for argument
alignment](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147084.html).

* Rong Xu posted an RFC on [adding a 'hot' function attribute to LLVM
IR](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147104.html) in
addition to the currently supported 'cold' attribute.

* Armand Behroozi is [seeking guidance on using LLVM to collect dynamic spill
and instruction counts from
LLVM](http://lists.llvm.org/pipermail/llvm-dev/2020-November/146962.html).
Quentin Colombet [suggests combining PGO data with emitted assembly
annotations](http://lists.llvm.org/pipermail/llvm-dev/2020-November/146967.html).

* Min-Yih Hsu [reports that the M68k patches are almost ready to
land](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147110.html), and
is seeking additional help in reviewing and approving this patches.

* ORC JIT Weekly #27 [is
out](http://lists.llvm.org/pipermail/llvm-dev/2020-December/147183.html),
giving an update on the status of the ORC runtime.


## LLVM commits

* Initial infrastructure for code generation of the RISC-V V extension was
committed. [5baef63](https://reviews.llvm.org/rG5baef6353e8).

* Documentation was added for the AMDGPU object V4 ABI.
[04424c6](https://reviews.llvm.org/rG04424c69bc7).

* A new attribute, `llvm.loop.vectorize.scalable.enable` was added.
[71bd59f](https://reviews.llvm.org/rG71bd59f0cb6).

* Prologue/epilogue sequences are better optimised for VE.
[686988a](https://reviews.llvm.org/rG686988a50f5),
[6834b3d](https://reviews.llvm.org/rG6834b3d6d52).

* A pseudo probe implementation pass was introduced, as part of the ongoing
context-sensitive sample PGO work.
[64fa8cc](https://reviews.llvm.org/rG64fa8cce225).

* The MemCpyOptimizer was ported to MemorySSA.
[624af93](https://reviews.llvm.org/rG624af932a80).

* Epilogue vectorization was added to the loop vectorizer.
[a7e2c26](https://reviews.llvm.org/rGa7e2c269399).

* Support was added for the experimental RISC-V half precision floating-point
extension (Zfh). [f7bc7c2](https://reviews.llvm.org/rGf7bc7c2981d).

* The 'code' type was removed from TableGen.
[415fab6](https://reviews.llvm.org/rG415fab6f67b).

* The BPF backend gained support for atomics.
[286daaf](https://reviews.llvm.org/rG286daafd651).

* An arm64e AArch64 sub-arch for Pointer Authentication was defined. It
defaults to the apple-a12 CPU.
[f77c948](https://reviews.llvm.org/rGf77c948d56b).

* llvm-objdump for RISC-V will now print pc-relative immediates as absolute
addresses. [ad923ed](https://reviews.llvm.org/rGad923edfc1c).


## Clang commits

* The new clang-format option PenaltyIndentedWhitespace assigns a penalty to
each character of new whitespace indentation, which in practice will alter
thresholds for preferring right-indenting multiple lines vs introducing a
line-break before the block.
[1e4d6d1](https://reviews.llvm.org/rG1e4d6d1c1ff).

* 'auto' can now be specified as the `-fdiagnostic-hotness-threshold`.
[93dc1b5](https://reviews.llvm.org/rG93dc1b5b8cb).

* CUDA overloading resolution was fixed.
[acb6f80](https://reviews.llvm.org/rGacb6f80d96b).

* clang-format's handling of C++ concepts was improved.
[840e651](https://reviews.llvm.org/rG840e651dc6d).

* clang-tidy gained a concurrency-mt-unsafe check that warns about usage of
functions known to be thread-unsafe.
[cac5be4](https://reviews.llvm.org/rGcac5be495ed).


## Other project commits

* LLVM's libc gained implementations of mktime, strncpy, and hypot.
[6f0f844](https://reviews.llvm.org/rG6f0f844e9af),
[60cef89](https://reviews.llvm.org/rG60cef893627),
[3b487d5](https://reviews.llvm.org/rG3b487d51e2e).

* A C++2b status page was added to libcxx.
[590bbfe](https://reviews.llvm.org/rG590bbfe0d80).