[llvm-dev] LLVM Weekly - #127, June 6th 2016

[Alex Bradbury via llvm-dev]

LLVM Weekly - #127, June 6th 2016
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/127>.

Welcome to the one hundred and twenty-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.


## News and articles from around the web

Graham Markall at Embecosm has been comparing the code size of [RISC-V
binaries produced by the GCC and LLVM
ports](http://www.embecosm.com/2016/05/26/risc-v-compiler-performance-part-1-code-size-comparisons/),
as well as compared to ARM. GCC is currently ahead, though it is worth noting
the LLVM port has seen much less attention.

Matthias Reisinger is a Google Summer of Code student working on enabling
polyhedral optimisations for the Julia programming language. He's written a
blog post detailing his [initial steps and immediate future
plans](http://www.mreisinger.com/?p=43). Hopefully we'll see more posts over
the summer.

Loïc Hamot has been working on a [C++ to D
converter](http://forum.dlang.org/post/ngxvmfqusvhyezwdbvaq@forum.dlang.org),
implemented using Clang.

The MSVC team have blogged about the [latest release of Clang with Microsoft
CodeGen](https://blogs.msdn.microsoft.com/vcblog/2016/06/03/clang-3-8-in-the-may-release-of-clang-with-microsoft-codegen/),
based on Clang 3.8.

There is going to be a [clang-tidy code
dojo](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100647.html) in
Warsaw on Tuesday the 7th of June.


## On the mailing lists

* Renato Golin has kicked off a discussion on [moving LLVM's repository
hosting to
GitHub](http://lists.llvm.org/pipermail/llvm-dev/2016-May/100310.html). Chris
Lattner [came out in
favour](http://lists.llvm.org/pipermail/llvm-dev/2016-May/100314.html),
specifically motivated by GitHub's community aspects. Renato has very
helpfully [summarised the
discussion](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100507.html).

* Peter Smith has shared his [initial port of LLD to
ARM](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100598.html) along
with his planned roadmap. The currently submitted patch is just enough to link
a hello world executable on ARM Linux.

* The apt repo hosted at llvm.org has been [temporarily turned
off](http://lists.llvm.org/pipermail/llvm-foundation/2016-May/000020.html) as
it is resulting in excessive I/O and network activity. Some commenters ask
about setting up an Ubuntu PPA or using the OpenSUSE build service.

* David Blaikie has written a GDB pretty printer script for some common LLVM
types and [described how to use
it](http://lists.llvm.org/pipermail/llvm-dev/2016-May/100365.html).

* Michael LeMay has posted an [RFC on using segmentation to harden
SafeStack](http://lists.llvm.org/pipermail/llvm-dev/2016-May/100346.html).

* Rui Ueyama has been investigating [using sendfile to copy file contents in
LLD](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100700.html) and
shares his results. He concludes the performance improvement is too modest to
be worth the change.

* If you're interested in register allocation, then [delve in to this thread
on LLVM's PBQP allocator and copy
propagation](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100523.html).

* Daniel Dunbar is [suggesting some changes to the lit default
output](http://lists.llvm.org/pipermail/cfe-dev/2016-May/049135.html).

* Steven Wu shares a follow-up RFC on [embedded
bitcode](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100643.html).

* There's a useful discussion in [this thread on lowering loops to use a
hardware loop
instruction](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100470.html).

* Peter Collingbourne [proposes renaming and slightly redesigning the bitset
metadata](http://lists.llvm.org/pipermail/llvm-dev/2016-June/100462.html).


## LLVM commits

* LLVM gained support for 'SJLJ' (setjmp/longjmp) exception handling on x86
targets. [r271244](http://reviews.llvm.org/rL271244).

* LLVM now requires CMake 3.4.3 to build
[r271325](http://reviews.llvm.org/rL271325).

* Support was added for attaching metadata to global variables.
[r271348](http://reviews.llvm.org/rL271348).

* The AArch64 backend switched to use SubtargetFeatures rather than testing
for specific CPUs. [r271555](http://reviews.llvm.org/rL271555).


## Clang commits

* The release notes have been updated to explain the current level of OpenMP
support (full support of non-offloading features of OpenMP 4.5).
[r271263](http://reviews.llvm.org/rL271263).

* Clang's source-based code coverage has been documented.
[r271454](http://reviews.llvm.org/rL271454).


## Other project commits

* An `-fno-exceptions` libc++abi library variant was defined, to match the
`-fno-exceptions` libc++ build. [r271267](http://reviews.llvm.org/rL271267).

* LLDB's compact unwind printing tool gained support for ARMv7's compact
unwind format. [r271744](http://reviews.llvm.org/rL271744).