[llvm-dev] LLVM Weekly - #260, December 24th 2018

[Alex Bradbury via llvm-dev]

LLVM Weekly - #260, December 24th 2018
======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/260>.

Welcome to the two hundred and sixtieth 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

Registration is [now open](http://llvm.org/devmtg/2019-04/#registration) for
EuroLLVM'19 and the call for papers [remains
open](http://llvm.org/devmtg/2019-04/#cfp).

LLVM 7.0.1 has been
[released](http://lists.llvm.org/pipermail/llvm-announce/2018-December/000081.html).


## On the mailing lists

* Nicolai Hähnle started an RFC discussion on [adding thread group semantics
to the
LangRef](http://lists.llvm.org/pipermail/llvm-dev/2018-December/128662.html),
motivated by GPU requirements.

* Chandler Carruth has shared a [holiday update on the LLVM relicensing
effort](http://lists.llvm.org/pipermail/llvm-dev/2018-December/128695.html).
Over 500 individual agreements have been completed, covering 73% of committers
and 80% of commits in the last 6 months and 63% of committers and 74% of
commits in the last 2 years. As explained in the email, please fill out the
individual agreement and forward the relicensing page to your employer if
they're
[not already listed](http://llvm.org/foundation/relicensing/#corporate_agreement)
as having signed or been contacted.

* JF Bastien shares that Intel's Parallel STL implementation has [now been
contributed to
LLVM](http://lists.llvm.org/pipermail/cfe-dev/2018-December/060606.html).

* Todd Snider is [seeking
comments](http://lists.llvm.org/pipermail/llvm-dev/2018-December/128632.html)
on the 'used' attribute semantics, which he observes seems to be used
inconsistently.

* Carey Williams wrote an RFC on [allocatable global register variable for
ARM](http://lists.llvm.org/pipermail/llvm-dev/2018-December/128706.html).
There is currently limited support for this for the stack pointer, but this
RFC proposes extended this for other registers.

## LLVM commits

* AArch64 now has a control flow speculation tracking pass aimed at mitigating
Spectre V1 style vulnerabilities.This tracks control flow miss speculation
into a taint regiter, which can be used to mask off registers with sensitive
data. See the detailed commit message for much more information.
[r349456](https://reviews.llvm.org/rL349456).

* FileCheck gained support for dumping its input annotated with diagnostics to
aid debugging. This helps to visualise FileCheck's matching behaviour.
[r349418](https://reviews.llvm.org/rL349418).

* The llvm-mca library was moved from tools/llvm-mca to lib/MCA.
[r349332](https://reviews.llvm.org/rL349332).

* AggressiveInstCombine learned to to convert a rorate with guard branch into
a funnel shift. [r349396](https://reviews.llvm.org/rL349396).

* TableGen will now only write output if it changed, instead of relying on
CMake to compare the previous output to the new output.
[r349624](https://reviews.llvm.org/rL349624).

* The BPF backend can now generated BTF (BPF Type Format) debug info.
[r349640](https://reviews.llvm.org/rL349640).

* `llvm.loop.parallel_accesses` and `llvm.access.group` metadata was
introduced. [r349725](https://reviews.llvm.org/rL349725).


## Clang commits

* Clang gained an option to initialise automatic variables with either a
pattern or with zeroes. The commit message does a fantastic job of summarising
the implementation choices and options considered, so is well worth a read.
[r349442](https://reviews.llvm.org/rL349442).

* Clang will now generate `llvm.loop.parallel_accesses` instead of
`llvm.mem.parallel_loop_access` metadata.
[r349823](https://reviews.llvm.org/rL349823).


## Other project commits

* The LLVM test suite now contains the 'CoMD' molecular dynamics DoE proxy
app. [r349922](https://reviews.llvm.org/rL349922).

* The sanitizer support code was updated to support running without only open
file descriptors (as may happen in the Linux 'init' process).
[r349817](https://reviews.llvm.org/rL349817).

* lld gained support for ARM v6m thunks.
[r349337](https://reviews.llvm.org/rL349337).