[llvm-dev] LLVM Weekly - #230, May 28th 2018

[Alex Bradbury via llvm-dev]

LLVM Weekly - #230, May 28th 2018
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/230>.

Welcome to the two hundred and thirtieth 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](https://www.linkedin.com/in/alex-bradbury/). 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 [12th LLVM Social
Berlin](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123599.html) will be
held this Thursday 31st May. Stefan Gränitz will talk about ThinLTO and
Incremental JIT Compilation.


## On the mailing lists

* Martin Storsjö
[reports](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123457.html) that
a demonstration of Windows on ARM64 at the Microsoft Build conference showed
VLC build with Clang, LLD, and mingw-w64.

* Jessica Paquette is
[pinging](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123505.html) for
any remaining objections to turning on MachineOutliner by default for AArch64
under -Oz.

* Erich Keane would [like more
feedback](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123527.html) on
the [host compiler proposal](https://reviews.llvm.org/D47073).

* Ulrich Weigand has shared a [lengthy
update](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123529.html) on the
status of strict FP, ending with a detailed list of proposed next steps.

* Peter Collingbourne
[proposes](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123514.html)
support for adding a new section to object output which indicates which
symbols are address-significant, and so can't be safely merged using identical
code folding in the linker.

* Paul Robinson has shared an RFC on [formalizing FileCheck
features](http://lists.llvm.org/pipermail/llvm-dev/2018-May/123550.html),
proposing a clear conceptual model for its operation.


## LLVM commits

* Support for "thunk" outlining was added for AArch64. This uses a tail-call
when outlining a sequence that ends in a call.
[r333015](https://reviews.llvm.org/rL333015).

* A new machine instruction property 'isMoveReg' was introduced alongside a
new isCopyInstr hook. This support is a pre-requisite for a patch which allows
LiveDebugValues to follow a variable's value moving from one register to
another. [r333093](https://reviews.llvm.org/rL333093).

* A series of patches that aims to improve the performance of
InstructionSelect during GlobalISel have started to land.
[r332907](https://reviews.llvm.org/rL332907).

* The RISC-V backend gained support for tail call optimisation.
[r333137](https://reviews.llvm.org/rL333137).

* Floating point binary operations with undef operands now fold to NaN.
[r332920](https://reviews.llvm.org/rL332920).

* The llvm-exegesis analysis output now uses HTML in order to produce a more
readable report. [r332979](https://reviews.llvm.org/rL332979).

* The DEBUG macro has been removed now all in-tree users have been updated to
`LLVM_DEBUG`. [r333091](https://reviews.llvm.org/rL333091).

* The CostPerUse attribute is now set on RISC-V registers which are unlikely
to be accessible in compressed (16-bit) instructions.
[r333132](https://reviews.llvm.org/rL333132).

* The LoopInstSimplify pass has been restored and will see improvements and
integration into the loop pass pipeline.
[r333250](https://reviews.llvm.org/rL333250).


## Clang commits

* Support was committed for the GNUstep Objective-C ABI version 2.
[r332950](https://reviews.llvm.org/rL332950).

* `__builtin_classify_type` support was reworked to better match GCC.
[r333126](https://reviews.llvm.org/rL333126).

* The clang-interpreter example was converted to use the ORC JIT API.
[r333302](https://reviews.llvm.org/rL333302).


## Other project commits

* The compiler-rt CMake build system was updated to support libc++ as the
Clang default stdlib. [r333010](https://reviews.llvm.org/rL333010).

* LLDB gained support for resolving variable symbols in PDB.
[r333049](https://reviews.llvm.org/rL333049).