[llvm-dev] LLVM Weekly - #308, November 25th 2019

[Alex Bradbury via llvm-dev]

LLVM Weekly - #308, November 25th 2019
======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/308>.

Welcome to the three hundred and 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 the LLVM Dev Meeting 2019
[continue to be
posted](https://www.youtube.com/channel/UCv2_41bSAa5Y_8BacJUZfjQ/videos).

LLVM 9.0.1-rc1 [has been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2019-November/137166.html).

The call for presentations for EuroLLVM 2020 [is now
active](http://lists.llvm.org/pipermail/llvm-dev/2019-November/137142.html).
The event will take place April 6-7 in Paris and proposals are due by Jan
11th.


## On the mailing lists

* Chandler Carruth kicked off a lengthy RFC thread on [moving towards Discord
for real time chat and Discourse for forum/list-style
discussions](http://lists.llvm.org/pipermail/llvm-dev/2019-November/136880.html).
This proposal follows discussions at the LLVM Dev Meeting and the Women in
Compilers and Tools meeting. This proposal has resulted in a large number of
responses. A number of people raised concerns about Discord as a proprietary
solution. Several respondents suggest it would be productive to separate
discussion of the real time chat and the forum solution.

* Eric Astor is [proposing to add MASM (Microsoft Macro Assembler)
support](http://lists.llvm.org/pipermail/llvm-dev/2019-November/137112.html)
to the LLVM MC layer.

* Bardia Mahjour shared [minutes from the loop optimisation working group Nov
20th
meeting](http://lists.llvm.org/pipermail/llvm-dev/2019-November/137073.html).

* Sean Kilmurray posted an RFC on [adding a mock backend target to
LLVM](http://lists.llvm.org/pipermail/llvm-dev/2019-November/137002.html)
which could be used to test assumptions like the size of bytes or addressable
unit sizes.

* David Blaikie started a
[discussion about
DW_OP_implicit_pointer](http://lists.llvm.org/pipermail/llvm-dev/2019-November/136798.html),
both from a DWARF perspective and the LLVM implementation.


## LLVM commits

* A new API was introduced to determine if an instruction can be safely moved
before another instruction. [ae8a8c2](https://reviews.llvm.org/rGae8a8c2db6c).

* Scalable vector MVT size queries are now supported.
[3f08ad6](https://reviews.llvm.org/rG3f08ad611aa).

* llvm-objdump now prints relocation addends in hexadecimal, just like GNU
objdump. [6baec97](https://reviews.llvm.org/rG6baec971271).

* Scheduling and cost models were added for the Exynos M5.
[9bdfee2](https://reviews.llvm.org/rG9bdfee2a3bd).

* TableGen will no longer error in the case of duplicate includes.
[ee9b49e](https://reviews.llvm.org/rGee9b49eef04).

* The CMake build system was updated to explicitly mark libraries defined in
lib/ as "component libraries".
[ab41180](https://reviews.llvm.org/rGab411801b82).

* The new gen-opt-rst TableGen backend will generate "command guides" for
common line options, for use in documentation.
[64ada7a](https://reviews.llvm.org/rG64ada7accbc).


## Clang commits

* Debug info size for Sema was reduced by adding an `anchor()` method,
resulting in a 17% saving for Sema object files on Windows and 14.6% on Linux.
[586f65d](https://reviews.llvm.org/rG586f65d31f3).

* The new clang-tidy performance-no-automatic-move check will flag when
constructs prevent automatic move of local variables.
[95fe549](https://reviews.llvm.org/rG95fe54931fd).

* `-ffixed-rN` can now be used to reserve r6-r11 on ARM.
[2d739f9](https://reviews.llvm.org/rG2d739f98d8a).

* Support was added for `__attribute__((objc_direct))` and
`__attribute__((objc_direct_members))`.
[d4e1ba3](https://reviews.llvm.org/rGd4e1ba3fa9d).


## Other project commits

* LLVM libc now has a TableGen based header generator.
[b47f9eb](https://reviews.llvm.org/rGb47f9eb55d1).

* LLDB gained a document describing caveats related to the usage of Python.
[0aed648](https://reviews.llvm.org/rG0aed6486497).

* LLDB now has some documentation on reproducers.
[f19ea6e](https://reviews.llvm.org/rGf19ea6ea5f8).

* The Archer tool was added to LLVM's OpenMP implementation. It provides TSan
annotations for OpenMP synchronisation.
[2b8115b](https://reviews.llvm.org/rG2b8115b10b0).