[llvm-dev] LLVM Weekly - #161, Jan 30th 2017

[Alex Bradbury via llvm-dev]

LLVM Weekly - #161, Jan 30th 2017
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/161>.

Welcome to the one hundred and sixty-first 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

Microsoft have
[announced](https://blogs.msdn.microsoft.com/directx/2017/01/23/new-directx-shader-compiler-based-on-clangllvm-now-available-as-open-source/)
a new open source DirectX shader compiler based on Clang and LLVM.

LLVM 4.0.0-rc1 source and binaries are [now
available](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109442.html).
Time to get testing!


## On the mailing lists

* Johannes Doerfert has posted an [RFC for adding parallel extensions to LLVM
IR](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109615.html).

* Chas Boyd has
[written](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109613.html)
to the mailing list to say a little more about Microsoft's use of LLVM and
Clang in the new DirectX Shader Compiler.

* Manuel Klimek reports that [work is starting on
ClangD](http://lists.llvm.org/pipermail/cfe-dev/2017-January/052458.html), a
daemon to provide access IDEs etc with access to Clang services.

* Philip Herron is curious about [selection of negative addition rather than
subtraction](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109511.html).
Matt Arsenault
[explains](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109512.html)
how this behaviour can be overridden.

* Guy Blank has posted an RFC on [making i1 illegal in X86
codegen](http://lists.llvm.org/pipermail/llvm-dev/2017-January/109461.html).


## LLVM commits

* NewGVN gained support for dead and redundant store elimination.
[r293258](http://reviews.llvm.org/rL293258).

* A new MemorySSA updater has been introduced.
[r293356](http://reviews.llvm.org/rL293356).

* A new guard-based loop predication optimisation has been added. This will
enable more guards to be hoisted out of loops.
[r293064](http://reviews.llvm.org/rL293064).

* lit has been expanded to allow boolean expressions in REQUIRES, XFAIL, and
UNSUPPORTED lines. [r292896](http://reviews.llvm.org/rL292896).

* Early if-conversion has been implemented for AMDGPU, but is disabled by
default for now. [r293016](http://reviews.llvm.org/rL293016).

* The llvm-xray graph subcommand now colors edges and vertices based on
statistics. [r293031](http://reviews.llvm.org/rL293031).

* A new OptimizationRemarkEmitter pass was added, allowing MIR passes to emit
optimisation remarks just like IR passes can.
[r293110](http://reviews.llvm.org/rL293110).

* The MIPS backend gained support for the static relocation model with the N64
ABI. [r293279](http://reviews.llvm.org/rL293279).

* A number of new intrinsics for constrained floating point operations have
been added. [r293226](http://reviews.llvm.org/rL293226).


## Clang commits

* A new TableGen-based generator for command line argument documentation was
added. [r292968](http://reviews.llvm.org/rL292968).

* Comment reflowing has been implemented for clang-format.
[r293055](http://reviews.llvm.org/rL293055).


## Other project commits

* XRay 'Flight Data Recorder' mode was implemented, which allows XRay to log
in-memory and then write out data on-demand as required.
[r293015](http://reviews.llvm.org/rL293015).

* LLD learned to handle the MEMORY linkerscript command.
[r292875](http://reviews.llvm.org/rL292875)

* LLDB now supports single stepping on ARM FreeBSD.
[r292937](http://reviews.llvm.org/rL292937).