[llvm-dev] LLVM Weekly - #298, September 16th 2019

[Alex Bradbury via llvm-dev]

LLVM Weekly - #298, September 16th 2019
=======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/298>.

Welcome to the two hundred and ninety-eighth 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

LLVM 9.0.0 release candidate 5 [has been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2019-September/135121.html).


## On the mailing lists

* Michael Woerister has been implementing profile-guided optimisation support
in the Rust compiler. He found there was no measurable performance gain and is
[seeking feedback as to why this might
be](http://lists.llvm.org/pipermail/llvm-dev/2019-September/135078.html).

* Philip Reames outlined [plans to enhance the loop vectorizer to handle
multiple exit
loops](http://lists.llvm.org/pipermail/llvm-dev/2019-September/134998.html).

* Varun Gandhi has a [proposal to change the behaviour of lit.py's -v
flag](http://lists.llvm.org/pipermail/llvm-dev/2019-September/135098.html).

* Bardia Mahjour shares [loop optimisation working group meeting
minutes](http://lists.llvm.org/pipermail/llvm-dev/2019-September/135058.html),
covering topics such as loop invariant code motion vs loop sink strategy.

* Daan Sprenkels kicked off a discussion on [protecting against side channel
attacks on
values](http://lists.llvm.org/pipermail/llvm-dev/2019-September/135079.html).

## LLVM commits

* Support was added to the AArch64 backend for the `arm64_32` watchOS ABI.
[r371722](https://reviews.llvm.org/rL371722).

* LLVM gained infrastructure to performance profile guided validation of
performance annotations, as used in the clang-misexpect tool.
[r371484](https://reviews.llvm.org/rL371484).

* A parser was committed for bitstream remarks.
[r371429](https://reviews.llvm.org/rL371429).

* The initial patch in a series intending to overhaul SelectionDAG atomic
load/store handling has landed. [r371441](https://reviews.llvm.org/rL371441).

* TableGen's CodeEmitter can now support instruction widths greater than 64
bits. [r371928](https://reviews.llvm.org/rL371928).


## Clang commits

* The constexpr interpreter was committed.
[r371834](https://reviews.llvm.org/rL371834).

* clang-format gained a new IndentGotoLabels style option.
[r371719](https://reviews.llvm.org/rL371719).

* Codegen was improved for `thread_local` variables.
[r371767](https://reviews.llvm.org/rL371767).


## Other project commits

* std::vector in libcxx will now unconditionally move elements when exceptions
are disabled. [r371867](https://reviews.llvm.org/rL371867).

* LLDB gained a reproducer dump command, making it possible to inspect a
reproducer from within LLDB. [r371909](https://reviews.llvm.org/rL371909).