[llvm-dev] LLVM Weekly - #278, April 29nd 2019

Alex Bradbury via llvm-dev llvm-dev at lists.llvm.org
Mon Apr 29 11:22:36 PDT 2019

LLVM Weekly - #278, April 29nd 2019

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Welcome to the two hundred and seventy-eighth 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

Videos from most talks at the 2019 EuroLLVM Developers' meeting are
[now available](https://www.youtube.com/playlist?list=PL_R5A0lGi1ADu1ccg_aykRC3dxhlIKShL),
including the [keynote on MLIR](https://www.youtube.com/watch?v=qzljG6DKgic).

On Red Hat's developer blog, Serge Guelton has an article on [LLVM's Advanced
Data Types and trivially copyable

## On the mailing lists

* Guillaume Chatelet posted an RFC on [allowing efficient implementation of
libc's memory functions in
Currently, you have to ensure that LLVM odesn't replace the implementation of
a libc memory function with a call to itself.

* Anja Gerbes is [looking for more
speakers](http://lists.llvm.org/pipermail/llvm-dev/2019-April/132002.html) for
an LLVM session at the ISC-HPC conference.

* Martin Storsjö is [seeking
advice](http://lists.llvm.org/pipermail/llvm-dev/2019-April/131974.html) on
automatically saving and restoring x18 around function calls on AArch64. This
is useful when running Windows ARM64 executables under Wine, as Windows treats
x18 as a reserved register.

* Alexandre Ganea wrote an RFC on [supporting clang-cl
/MP](http://lists.llvm.org/pipermail/llvm-dev/2019-April/131967.html) in order
to improve compile-time performance.

* Philip Reames
optimising TargetLibraryInfo getLibFunc lookups.

* Rui Ueyama [write an
RFC](http://lists.llvm.org/pipermail/llvm-dev/2019-April/131902.html) on
supporting mostly-concurrent symbol resolution in LLD.

* Andrei Damian [seeks
advice](http://lists.llvm.org/pipermail/cfe-dev/2019-April/062163.html) on
using libclang or libtooling for a transpiler.

## LLVM commits

* The AMDGPU backend started to gain support for gfx1010
[r359316](https://reviews.llvm.org/rL359316), and more.

* LLVM gained support for the AArch64 MTE (Memory Tagging Extension) via
intrinsics. [r358963](https://reviews.llvm.org/rL358960).

* The DAGCombiner learned to apply most ADD combines to an OR operation in the
case that the operands have no common bits set.

* LLVM's support library gained a JSON streaming output API.

## Clang commits

* `__builtin_is_constant_evaluated` was implemented for use in C++2a.

* MMX intrinsics were ported to PowerPC (using Altivec).

* The behaviour of interaction of `__builtin_constant_p` and `constexpr` was
updated to match trunk GCC. [r359367](https://reviews.llvm.org/rL359367).

* Clang gained support for the AArch64 MTE (Memory Tagging Extension)
intrinsics. [r359348](https://reviews.llvm.org/rL359348).

* clang-tidy gained a new llvm-prefer-isa-or-dyn-cast-in-conditionals checker.

## Other project commits

* The libcxxabi `cxa_guard` implementation was rewritten to use futexes and to
avoid a global lock. [r359060](https://reviews.llvm.org/rL359060).

* The compiler-rt builtins were reformatted with clang-format, and aliases are
now used for function redirects.

* libcxx gained an implementation of `std::is_constant_evaluated`.

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