[llvm-dev] LLVM Weekly - #147, Oct 24th 2016

[Alex Bradbury via llvm-dev]

LLVM Weekly - #147, Oct 24th 2016
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/147>.

Welcome to the one hundred and forty-seventh 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.

I'm heading off to the US this week, first to attend the Google Summer of Code
Mentor Summit and then for the LLVM Developers' Meeting. Hope I'll see some of
you there.

## News and articles from around the web

The long-awaited survey on the move of LLVM development to GitHub is [now
online](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106135.html).
You are strongly encouraged to fill it out and share your views.

There is a lot of LLVM social activity going on this week. The next Cambridge
LLVM Social [will be
held](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106209.html) on
Wednesday, October 26th. On Thursday October 27th, the inaugural Bristol LLVM
Social [will be
held](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106181.html). Also
on Thursday is the [LLVM Social in
Berlin](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106412.html).

An LLVM Performance Workshop has been
[announced](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106174.html)
at CGO in 2017. The call for proposals is open until December 1st.

The Trail of Bits blog has a fantastic and detailed [overview of control-flow
integrity in
Clang](https://blog.trailofbits.com/2016/10/17/lets-talk-about-cfi-clang-edition/).


## On the mailing lists

* Nuno Lopes has kicked off an RFC thread on [getting rid of undef in
LLVM](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106182.html). This
proposal was a group effort, and there is a talk about it at the upcoming Dev
Meeting. A huge amount of discussion has been generated, I'm sorry I don't
have the time to summarise it.

* Tanya Lattner is [looking for
volunteers](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106394.html)
to help with the 'Hackers Lab' at the upcoming Developers' Meeting.

* Hal Finkel has proposed [removing PowerPC/Darwin
support](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106359.html)
from LLVM. There seem to be no objections.

* Johannes Doerfert has [shared an initial
document](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106386.html)
to collect thoughts in preparation for the BoF discussion on parallel IR.

* Rui Ueyama shared an RFC on [creating linker-generated sections as input
sections instead of output sections in
LLD](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106226.html). Peter
Smith reports that [the ARM proprietary linker uses a similar
scheme](http://lists.llvm.org/pipermail/llvm-dev/2016-October/106258.html).


## LLVM commits

* The minimum supported GCC version for building LLVM is now 4.8.
[r284497](http://reviews.llvm.org/rL284497).

* The SystemZ backend has gained a post-RA (register allocation) scheduler.
[r284704](http://reviews.llvm.org/rL284704).

* The machine code disassembler for the AVR backend has landed.
[r284930](http://reviews.llvm.org/rL284930).

* The internal `LLVM_ATTRIBUTE_UNUSED_RESULT` define has now been removed. If
you're using this in your out-of-tree code, switch to `LLVM_NODISCARD`.
[r284367](http://reviews.llvm.org/rL284367).

* A number of helpers for formatting numbers have been added to libSupport.
[r284425](http://reviews.llvm.org/rL284425). REVERTED

* A new pass has been added that eliminates library calls where the result
value isn't used. [r284542](http://reviews.llvm.org/rL284542).

* IndVarSimplify's ability to prove non-negativity has been improved.
[r284629](http://reviews.llvm.org/rL284629).

* The internal `LLVM_NOEXCEPT` macro has been removed in favour of `noexcept`,
which all supported compilers can now handle.
[r284672](http://reviews.llvm.org/rL284672).


## Clang commits

* A new check, readability-redundant-member-init, was added. This emits a
warning if a member-initializer calls the member's default constructor with no
arguments. [r284742](http://reviews.llvm.org/rL284742).

* The Python libclang bindings have been updated to add previously missing
cursor kinds. [r284464](http://reviews.llvm.org/rL284464).

* A new NumberObjectConversion checker, meant for use with classes like
Objective-C's NSNumber has been added.
[r284473](http://reviews.llvm.org/rL284473).

* Masses more doxygen comments have been added to the intrinsics described in
emmintrin.h. [r284754](http://reviews.llvm.org/rL284754),
[r284934](http://reviews.llvm.org/rL284934).


## Other project commits

* Partial support for the `--gdb-index` command line option was added to LLD.
This section is generated in order to allow gdb to locate separate .dwo files.
[r284708](http://reviews.llvm.org/rL284708).

* The LLDB formatters for libstdc++ smart pointers have been improved, and
will now display more useful information. Formatters have also been added for
libstdc++ tuple and `unique_ptr`.
[r284828](http://reviews.llvm.org/rL284828),
[r284829](http://reviews.llvm.org/rL284829),
[r284830](http://reviews.llvm.org/rL284830).