[llvm-dev] LLVM Weekly - #160, Jan 23rd 2017

[Alex Bradbury via llvm-dev]

LLVM Weekly - #160, Jan 23rd 2017
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/160>.

Welcome to the one 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](http://asbradbury.org). 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 4.0.0-rc1 has [now been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109217.html).

Details are now
[available](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109374.html)
for EuroLLVM2017 student travel grants.

The Polly project has gained a new ARM64 buildbot, sponsored by the Qualcomm
Innovation Center. This [blog
post](http://pollylabs.org/2017/01/18/New-ARM64-Buildbot-for-Polly.html) goes
into some extra detail about Polly's continuous integration setup.

The next Cambridge LLVM social will [take
place](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109163.html) on
Wednesday, Jan 25th.

The next [Berlin LLVM
social](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109384.html)
will take place on the 26th of January.


## On the mailing lists

* Quentin Colombet has shared a [status update on global instruction
selection](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109366.html).
The plan remains to enable it by default for `-O0` on AArch64 by the end of
the year.

* Vassil Vasilev is [looking for
help](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109080.html) in
revitalising the list of open LLVM projects.

* There have been further discussion on the proposal for IR-level region
annotations. I can't summarise it all here, but the input from [the Tapir and
PIR team](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109264.html)
and [Vikram Adve's
response](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109276.html)
is worth reading.

* John Regehr, as secretary of the LLVM Foundation, has [written to confirm
Chris Lattner will remain on the LLVM Foundation Board of
Directors](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109138.html).
The question was raised due to the fact Chris has recently announced a move
from Apple to Tesla.

* The discussion about enabling GlobalISel by default has continued, with
Quentin Colombet giving a [helpful
summary](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109279.html) of
the key points.

* Dmitry Golovin reports on his [attempts to link the Linux kernel with
LLD](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109288.html). A
working kernel isn't produced, but with the listed changes the buidl process
does at least complete.

* Piotr Padlewski has proposed an RFC on [improving how vtable loads are
decorated](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109332.html)
in order to handle devirtualisation better.

* Mikhail Zolotukhin has shared a [new analysis of recent compile time
regressions in
LLVM](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109188.html).

* Discussion on the git transition continues, with Chris Lattner [advocating
the monorepo
approach](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109115.html).


## LLVM commits

* A new `-debug-info-for-profiling` option was added. This will cause a larger
amount of debug info to be generated which will be used in profile-guided
optimisations. [r292457](http://reviews.llvm.org/rL292457).

* Partial unrolling now has its own threshold.
[r292293](http://reviews.llvm.org/rL292293).

* Literals generated AArch64 targets are now constructed started from their
little end, in order to meet the recommendation of the Cortex A57 software
optimisation guide. [r292422](http://reviews.llvm.org/rL292422).

* The LiveRegUnits class has been factored out of RegisterScavenging.
[r292542](http://reviews.llvm.org/rL292542).

* Support for profile-guided optimisation in the new inliner has been
improved. [r292666](http://reviews.llvm.org/rL292666).

* LoopSink has been ported to the new pass manager.
[r292589](http://reviews.llvm.org/rL292589).


## Clang commits

* Support for constexpr evaluation of string builtins was documented.
[r292558](http://reviews.llvm.org/rL292558).

* Sadly, Clang's Python bindings don't currently work in Python 3. They will
now explicitly check the Python version an raise an error if it's not '2'.
[r292247](http://reviews.llvm.org/rL292247).

* Support for OpenMP 'target parallel' on the host and the NVPTX device was
added. [r292419](http://reviews.llvm.org/rL292419),
[r292428](http://reviews.llvm.org/rL292428).


## Other project commits

* There have been a number of improvements for CMake and Lit with libcxx on
Windows. [r292157](http://reviews.llvm.org/rL292157).

* The 'buildit' and 'testit' scripts will be removed from libcxx in the next
week. [r292181](http://reviews.llvm.org/rL292181).

* A new macro for succinct logging was added to the LLDB codebase.
[r292360](http://reviews.llvm.org/rL292360).