[LLVMdev] LLVM Weekly - #53, Jan 5th 2015

[Alex Bradbury]

LLVM Weekly - #53, Jan 5th 2015
===============================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/53>.

Welcome to the fifty-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](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 going to be in California next week for the [RISC-V
workshop](http://riscv.org/workshop). I'm arriving at SFO on Monday 12th and
leaving on Sunday the 18th. Do let me know if you want to meet and talk
[lowRISC](http://www.lowrisc.org)/RISC-V or LLVM, and we'll see what we can
do.


## News and articles from around the web

I was getting ready to break out gitstats for some analysis of the LLVM repo
and I find to my delight that Phoronix has saved me the trouble and has
[shared some stats on activity in the LLVM repo over the past
year](http://www.phoronix.com/scan.php?page=news_item&px=MTg3OTA).

Tom Stellard has made a blog post [announcing some recent RadeonSI performance
improvements](http://www.stellard.net/tom/blog/?p=69) on his LLVM development
branch. This includes 60% improvement in one OpenCL benchmark and 10-25% in a
range of other OpenCL tests.

Gaëtan Lehmann has written a blog post about [getting started with libclang
using the Python
bindings](http://blog.glehmann.net/2014/12/29/Playing-with-libclang/).

The C++ Filesystem Technical Specification, based on the Boost.Filesystem
library [has been
approved](http://article.gmane.org/gmane.comp.lib.boost.devel/256220).


## On the mailing lists

* Virgile Bello has some questions on [how he can control the calling
convention in LLVM](http://article.gmane.org/gmane.comp.compilers.llvm.devel/80215).
In this case, he has an CLR frontend and is trying to pass an object on the
CLR stack to a native Win32 function. Reid Kleckner
[suggests](http://article.gmane.org/gmane.comp.compilers.llvm.devel/80217) the
best way may be to just link with Clang and use its implementation. In another
followup, he links to the [talk on this
topic](http://llvm.org/devmtg/2014-10/Slides/Skip%20the%20FFI.pdf) at the last
LLVM dev meeting.

* [Is anybody using the ModuleBuilder class in
Clang?](http://article.gmane.org/gmane.comp.compilers.clang.devel/40426). If
so, now is the time to speak up as it's slated to be removed.

* Sami Liedes has [set up a new bot to test Clang with fuzzed
inputs](http://article.gmane.org/gmane.comp.compilers.clang.devel/40474). A
report from the bot is available
[here](http://sli.dy.fi/~sliedes/clang-triage/triage_report.xhtml) and the
code is [here](https://github.com/sliedes/clang-triage).

* The release of LLVM/Clang 3.5.1 may be slightly delayed due to the addition
of new patches late in the process. Chandler Carruth [points
out](http://article.gmane.org/gmane.comp.compilers.llvm.devel/80202) that
there are some unpleasant bugs in InstCombine in the current 3.5.1 release
candidate. If there is a release candidate 3, the patch in question will
definitely make it in.


## LLVM commits

* Instruction selection for bit-permuting operations on PowerPC has been
improved. [r225056](http://reviews.llvm.org/rL225056).

* The scalar replacement of aggregates (SROA) pass has started to learn how to
more intelligently handle split loads and stores. As explained in detail in
the commit message, the old approach lead to complex IR that can be difficult
for the optimizer to work with. SROA is now also more aggressive in its
splitting of loads. [r225061](http://reviews.llvm.org/rL225061),
[r225074](http://reviews.llvm.org/rL225074).

* InstCombine will now try to transform `A-B < 0` in to `A < B`.
[r225034](http://reviews.llvm.org/rL225034).

* The Hexagon (a Qualcomm DSP) backend has seen quite a lot of work recently.
Interested parties are best of flicking through the commit log of
lib/Target/Hexagon. [r225005](http://reviews.llvm.org/rL225005),
[r225006](http://reviews.llvm.org/rL225006), etc.


## Clang commits

* More crash bugs have been uncovered and fixed by the [naive fuzzing
technique](http://article.gmane.org/gmane.comp.compilers.llvm.devel/79491)
previously covered in LLVM Weekly. e.g.
[r224915](http://reviews.llvm.org/rL224915).


## Other project commits

* The lldb website has been updated with more information about LLDB on
windows, including [build
instructions](http://lldb.llvm.org/build.html#BuildingLldbOnWindows).
[r225023](http://reviews.llvm.org/rL225023).