[llvm-dev] LLVM Weekly - #293, August 12th 2019

[Alex Bradbury via llvm-dev]

LLVM Weekly - #293, August 12th 2019
===================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/293>.

Welcome to the two hundred and ninety-third 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

The deadline for submissions to the 2019 LLVM Dev Meeting [is
today](http://lists.llvm.org/pipermail/llvm-dev/2019-August/134470.html),
Monday 12th August. Applications for [student travel
grants](http://llvm.org/devmtg/2019-10/index.html#grant) close on August 16th.

Serge Guelton has authored a blog post on [Clang optimisation
options](https://developers.redhat.com/blog/2019/08/05/customize-the-compilation-process-with-clang-optimization-options/).


## On the mailing lists

* Michael Paszkowski [describes the
llvm-canon](http://lists.llvm.org/pipermail/llvm-dev/2019-August/134475.html),
developed after seeing Puyan Lotfi's talk on mir-canon. Michal is looking for
feedback from the community on the design and implementation of the tool, and
has [posted it to Phabricator](https://reviews.llvm.org/D66029).

* Richard Trieu has been working on [new clang warnings and improvements to
default
warnings](http://lists.llvm.org/pipermail/cfe-dev/2019-August/063065.html) and
would like further comments and review.

* Medhi Amini
[summarises](http://lists.llvm.org/pipermail/llvm-dev/2019-August/134452.html)
some key elements of the EuroLLVM round table discussion on the use of the
Bazel build system for LLVM.

* Sjoerd Meijer is [looking for
thoughts](http://lists.llvm.org/pipermail/cfe-dev/2019-August/063054.html) on
whether setting a transformation option should also imply the transformation
(and proposes that it should, and this should be done consistently).

* Happy Mahto and a group of other IIT Hyderabad students started an RFC
thread on [adding new vectorization pragms to
LLVM](http://lists.llvm.org/pipermail/llvm-dev/2019-August/134432.html). Hal
Finkel
[responded](http://lists.llvm.org/pipermail/llvm-dev/2019-August/134441.html)
with some feedback.


## LLVM commits

* llvm-readelf learned a new `--stack-sizes` option.
[r367942](https://reviews.llvm.org/rL367942).

* Initial SVE calling convention support was committed.
[r367859](https://reviews.llvm.org/rL367859).

* `update_test_checks.py` can now be run in an `--update-only` mode where it
will skip any tests that weren't automatically generated. This functionality
has also been made available to other `update_*_checks.py` scripts.
[r367900](https://reviews.llvm.org/rL367900),
[r368174](https://reviews.llvm.org/rL368174).

* The new Loop Cache Analysis pass can be used to estimate the number of cache
lines required by a loop nest.[r368439](https://reviews.llvm.org/rL368439).

* As part of the effort to redesign bugpoint, a new delta IR reduction tool was
committed (llvm-reduce). [r368358](https://reviews.llvm.org/rL368358).

* x86-experimental-vector-widening-legalization is now enabled by default,
which changes the default legalization behaviour for 16/32/64-bit vectors with
i8/i16/i32/i64 scalar types from promotion to widening.
[r367901](https://reviews.llvm.org/rL367901).

* A new KnownBits analysis pass was added for GlobalISel.
[r368065](https://reviews.llvm.org/rL368065).

* A new llvm.licm.disable metadata was reduced to indicate loop-invariant code
motion shouldn't be performed on the indicated loop.
[r368296](https://reviews.llvm.org/rL368296).

* ABI register names can now be used in assembly constraints for the RISC-V
target, meaning frontends no longer need to convert to architectural register
names. [r368303](https://reviews.llvm.org/rL368303).


## Clang commits

* SVE built-in types have been introduced, which are intended to become
sizeless types. [r368413](https://reviews.llvm.org/rL368413).

* A new `-stdlib++-isystem` command line option was introduced, allowing
explicit control over the C++ standard library search paths.
[r367982](https://reviews.llvm.org/rL367982).

* ASTImporter now has documentation.
[r368009](https://reviews.llvm.org/rL368009).

* clang-scan-deps gained a new fast scanning mode, where preprocessing is done
on file that are minimised using the dependency directives source minimiser.
[r368086](https://reviews.llvm.org/rL368086).


## Other project commits

* HWASan learned to instrument globals.
[r368102](https://reviews.llvm.org/rL368102).

* LLDB was updated to support loading binaries that were linked
deterministically on macOS. [r368199](https://reviews.llvm.org/rL368199).