[llvm-dev] LLVM Weekly - #347, August 24th 2020

[Alex Bradbury via llvm-dev]

LLVM Weekly - #347, August 24th 2020
====================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/347>.

Welcome to the three hundred and forty-seventh 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 LLVM Foundation's new Board of Directors [has been
announced](http://lists.llvm.org/pipermail/llvm-foundation/2020-August/000221.html).
The new board consists of Kit Barton, Kristof Beyls, Mike Edwards (Treasurer),
Hal Finkel, Cyndy Ishida, Anton Korobeynikov, Tanya Lattner (President), Chris
Lattner, Tom Stellard (Secretary).

LLVM 11.0.0-rc2 [has been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144477.html).


## On the mailing lists

* Leonard Chan posted an RFC on [adding a new Constant type to represent
function PLT
entries](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144469.html).
Fangrui Song [explained how the terminology may be
confusing](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144491.html).
Eric Christopher [expressed concerns about adding more complexity to the
IR](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144488.html), to
which Chris Lattner
[responded](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144518.html)
with motivations for the change in terms of expressivity and simplicity.

* The 14th MLIR newsletter is [now
available](https://llvm.discourse.group/t/mlir-news-14th-edition-8-21-2020/1560),
summarising recent MLIR developments.

* Florian Hahn proposes [switching to MemorySSA-backed Dead Store
Elimination](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144417.html),
which would allow the elimination of stores across basic blocks at the cost of
a small increase in compile time.

* Zi Xuan Wu [proposed the addition of a backend for the C-SKY processor
architecture](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144481.html).

* Filippo Costa [asks about adopting a third-party JSON library instead of
LLVM's homegrown
implementation](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144432.html).
The responses detail some of the concerns about adding external dependencies.

* Alexander Shaposhnikov posted an RFC on [contributing a `bitcode_strip`
utility](http://lists.llvm.org/pipermail/llvm-dev/2020-August/144490.html)
(currently part of Apple's cctools and distributed with XCode).


## LLVM commits

* DataLayout parsing will now fail gracefully rather than simply using
`report_fatal_error`. [874aef8](https://reviews.llvm.org/rG874aef875d0).

* llvm-objdump gained a `--symbolize-operands` option to print a label rather
than a real address for branch target operands.
[819b2d9](https://reviews.llvm.org/rG819b2d9c790).

* The TableGen Programmer's Reference document was created, combining the
previous language introduction and language reference documents.
[e0c01e6](https://reviews.llvm.org/rGe0c01e6cb07).

* InstCombine was updated to handle a common pattern in C++ exception lowering
code. [ae7f088](https://reviews.llvm.org/rGae7f08812e0).

* DemandedBits analysis was made more precise for addition.
[c1f6ce0](https://reviews.llvm.org/rGc1f6ce0c732).

* The Attributor learned to deduce the noundef attribute.
[5e361e2](https://reviews.llvm.org/rG5e361e2aa4f).

* A new `force-remove-attribute` argument was introduced to remove an
attribute from a function via the command line.
[7a028fe](https://reviews.llvm.org/rG7a028fe7029).

* The FixedPointBuilder helper class was introduced.
[f03b10f](https://reviews.llvm.org/rGf03b10f57eb).

* The legalization for FSHL and FSHR was improved.
[0819a64](https://reviews.llvm.org/rG0819a6416fd).

* The preferred syntax for an integer range in TableGen is now `{0...9}`
rather than `{0-9}`. [196e6f9](https://reviews.llvm.org/rG196e6f9f189).


## Clang commits

* Initial support for `-mtune` was added to the Clang driver for X86.
[4cbceb7](https://reviews.llvm.org/rG4cbceb74bb5).

* A non-exhaustive list of intrinsics that can be used in constant expressions
was documented. [f76adc2](https://reviews.llvm.org/rGf76adc2603f).

* `_ExtInt` is now disabled with `__atomic` builtins.
[ca77ab4](https://reviews.llvm.org/rGca77ab494aa).


## Other project commits

* libclc gained a Mesa/SPIR-V target.
[c37145c](https://reviews.llvm.org/rGc37145cab12).

* Standard MLIR types and attributes are now exposed in its C API.
[74f57784](https://reviews.llvm.org/rG74f577845e8),
[da56297](https://reviews.llvm.org/rGda562974628).

* A new Pattern Descriptor Language (PDL) MLIR dialect was added.
[3fb3927](https://reviews.llvm.org/rG3fb3927bd33).

* LLVM's OpenMP implementation gained a target memory manager, aiming to limit
the number of allocation and frees by not immediately freeing memory.
[0289696](https://reviews.llvm.org/rG0289696751e).

* LLVM's libc frexp and logb implementations were switched to use the new
NormalFloat class. [87bf0b0](https://reviews.llvm.org/rG87bf0b0ee98).