[llvm-dev] LLVM Weekly - #288, July 8th 2019

[Alex Bradbury via llvm-dev]

LLVM Weekly - #288, July 8th 2019
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/288>.

Welcome to the two hundred and eighty-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

As mentioned last week, registration is
[open](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133566.html) for the
2019 LLVM Developers' Meeting, to be held October 22-23rd in the Bay Area. The
call for presentations is [also
open](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133585.html). Get
your submissions in by August 12th.

The next HelloLLVM/HelloGCC social in China will [take
place](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133638.html) in
Hangzhou on July 20th.


## On the mailing lists

* I have
[proposed](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133724.html)
that the RISC-V backend be promoted from 'experimental' to 'official' in time
for the 9.0 branch and release. See the mailing list for full details on the
current status. At lowRISC, we've recently been putting it through its paces
with with buildroot, where we can compile over 90% of its over 2000 packages.

* Nandor Licker kicked off an RFC on
[ConstExprPreter](http://lists.llvm.org/pipermail/cfe-dev/2019-July/062799.html),
a fast interpreter for C++ constexpr to replace the existing tree evaluator.

* David Greene [wrote an RFC on first-class complex number support in LLVM
IR](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133558.html).

* Simon Tatham
[queried](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133648.html)
whether it is acceptable to have Python as a build dependency of LLVM. His
motivation is to write a TableGen backend in Python, processing the output of
`llvm-tblgen -dump-json`.

* Rui Ueyama has [tried
out](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133645.html) the
proposed new LLVM variable naming scheme on the LLD codebase.

* Bardia Mahjour
[shared](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133611.html)
meeting minutes from the loop optimisation working group.

* Simon Pilgrim started to enumerate [reasons why tablegen is
slow](http://lists.llvm.org/pipermail/llvm-dev/2019-July/133576.html).


## LLVM commits

* The scalable vector IR type was recommited again.
[r365203](https://reviews.llvm.org/rL365203).

* TableGen now allows DAG ISel patterns to override default operands.
[r365114](https://reviews.llvm.org/rL365114).

* The llvm-readelf and llvm-objcopy documentation was expanded.
[r364800](https://reviews.llvm.org/rL364800),
[r365042](https://reviews.llvm.org/rL365042).

* BitCode/BitStream was moved to a separate library, to avoid a circular
dependency when using it to parse optimisation remarks.
[r365091](https://reviews.llvm.org/rL365091).

* The X86 backend learned to avoid folding immediate operands to
ADD/SUB/AND/OR/XOR when they have multiple uses and compiling for optsize.
[r365163](https://reviews.llvm.org/rL365163).

* The RISC-V backend now supports the llvm.readcyclecounter intrinsic.
[r365201](https://reviews.llvm.org/rL365201).


## Clang commits

* clang-format gained a new AlignConsecutiveMacros style option.
[r364938](https://reviews.llvm.org/rL364938).

* `__builtin_bit_cast` was added, which is used to implement `std::bit_cast`.
[r364954](https://reviews.llvm.org/rL364954).

* A new bugprone-posix-return checker was implemented.
[r365007](https://reviews.llvm.org/rL365007).


## Other project commits

* Support for C++20 bit operations was added to libcxx.
[r364862](https://reviews.llvm.org/rL364862).

* LLD gained a number of improvements in its RISC-V support. e.g. support for
PLT, GOT, copy and relative relocations, and for GD/LD/IE/LE TLS models.
[r364812](https://reviews.llvm.org/rL364812),
[r364813](https://reviews.llvm.org/rL364813).