[LLVMdev] LLVM Weekly - #44, Nov 3rd 2014

[Alex Bradbury]

LLVM Weekly - #44, Nov 3rd 2014
===============================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/44>.

Welcome to the forty-fourth 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

The [2014 LLVM Dev meeting](http://llvm.org/devmtg/2014-10/) was held last
week. I couldn't make it, but it seems like there was a great selection of
talks. Sadly the keynote about Swift's high-level IR [was
cancelled](http://lists.cs.uiuc.edu/pipermail/llvm-devmeeting/2014-October/000176.html).
No word yet on when we can expect slides and videos online. However, slides by
Philip Reames and Sanjoy Das from their talk on on implementing fully
relocating garbage collection in LLVM [are
online](http://www.playingwithpointers.com/llvm-dev-2014-slides.pdf).

[Peter Zotov](http://whitequark.org/) has been doing lots of work on the LLVM
OCaml bindings recently, and is looking for additional help. Recently, he's
closed almost all open bugs for the bindings, migrated them to ocamlfind,
fixed `Lllvm_executionengine`, and ensured pretty much the whole LLM-C API is
exposed. Tasks on the todo list include writing tests in OUnit2 format,
migrating the Kaleidoscope tutorial off camlp4, and splitting up and adding
OCaml bindings to [this patch](http://reviews.llvm.org/D2176). More
ambitiously, it would be interesting to writing LLVM passes in OCaml and to
represent LLVM IR as pure AST. If any of this interests you, do get in touch
with Peter. He's able to review any patches, but could do with help on working
through this list of new features.

The LLVM Bay Area monthly social is [going to be held on 6th
November](http://article.gmane.org/gmane.comp.compilers.clang.devel/39524).


## On the mailing lists

* Reid Kleckner has [proposed dropping support for running LLVM on Windows
XP](http://article.gmane.org/gmane.comp.compilers.llvm.devel/78419). This
would allow the use of system APIs only available in Vista and above. Thus far
all responses have been positive, with one even suggesting raising the minimum
to Windows 7.

* Tom Stellard suggests [deprecating the autoconf build
system](http://article.gmane.org/gmane.comp.compilers.llvm.devel/78453). Right
now there is both an autotools based system and a CMake system, though CMake
seems most used by developers for LLVM at least. Bob Wilson [points
out](http://article.gmane.org/gmane.comp.compilers.llvm.devel/78459) that the
effort required to keep the existing makefiles working is much less than what
might be needed to update the CMake build to support all uses cases. Though
other replies make it seems that the CMake build supports pretty much all
configurations people use now. If there are people who actually enjoy fiddling
with build systems (far-fetched, I know), it seems like a little effort could
go a long way and allow the makefile system to be jettisoned.

* Betul Buyukkurt has posted an [RFC on indirect call target
profiling](http://article.gmane.org/gmane.comp.compilers.llvm.devel/78415).
The goal is to use the collected data for optimisation. Kostya Serebryany
[described how it can be used to provide feedback to
fuzzers](http://article.gmane.org/gmane.comp.compilers.clang.devel/39563) and
detailed properties that would be useful for this usecase.

* Chris Matthews
[announces](http://article.gmane.org/gmane.comp.compilers.llvm.devel/78319)
that a new Jenkins-based OSX build cluster is up and running. This includes
multiple build profiles and an O3 LTO performance tracker. The Jenkins config
should be committed to zorg soon.


## LLVM commits

* Support for writing sampling profiles has been committed. In the future,
support to read (and maybe write) profiles in GCC's gcov format will be added,
and llvm-profdata will get support to manipulate sampling profiles.
[r220915](http://reviews.llvm.org/rL220915).

* A comment has been added to X86AsmInstrumentation to describe how asm
instrumentation works. [r220670](http://reviews.llvm.org/rL220670).

* The Microsoft vectorcall calling convention has been implemented for x86 and
x86-64. [r220745](http://reviews.llvm.org/rL220745).

* The C (and OCaml) APIs gained functions to query and modify branches, and to
obtain the values for floating point constants. There have been a whole bunch
of additional commits related to the OCaml bindings, too many to pick out
anything representative.
[r220814](http://reviews.llvm.org/rL220814),
[r220815](http://reviews.llvm.org/rL220815),
[r220817](http://reviews.llvm.org/rL220817),
[r220818](http://reviews.llvm.org/rL220818).

* The loop and SLP (superword level parallelism) vectorizers are now enabled
in the Gold plugin. [r220886](http://reviews.llvm.org/rL220886),
[r220887](http://reviews.llvm.org/rL220887).


## Clang commits

* A refactoring of libTooling to reduce required dependencies means that
clang-format's binary is now roughly half the size.
[r220867](http://reviews.llvm.org/rL220867).


## Other project commits

* lldb has started to adopt the StringPrinter API.
[r220894](http://reviews.llvm.org/rL220894).

* Initial support for PowerPC/PowerPC64 on FreeBSD has been added to LLDB.
[r220944](http://reviews.llvm.org/rL220944).