[llvm-dev] LLVM Weekly - #325, Mar 23rd 2020

[Alex Bradbury via llvm-dev]

LLVM Weekly - #325, Mar 23rd 2020
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/325>.

Welcome to the three hundred and twenty-fifth 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

LLVM 10.0.0-rc6 [has been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2020-March/140191.html).


## On the mailing lists

* The 3rd MLIR newsletter is [now
out](https://llvm.discourse.group/t/mlir-news-3rd-edition-3-20-2020/670).

* ORC JIT Weekly #9 [is
out](http://lists.llvm.org/pipermail/llvm-dev/2020-March/140162.html). OrcV2
JITEventListener support (with fixes) has landed.

* Anton Korobeynikov has sent a note out [for students thinking of submitting
proposals for LLVM in
GSoC](http://lists.llvm.org/pipermail/llvm-dev/2020-March/140029.html).

* Rahman Lavaee shared a plan for [handling Intel JCC mitigation using
Propeller](http://lists.llvm.org/pipermail/llvm-dev/2020-March/140134.html).

* Farzad Sadeghi posted an RFC on [adding his cgrep utility to
clang-tools-extra](http://lists.llvm.org/pipermail/cfe-dev/2020-March/064878.html).

* Kristóf Umann has [shared a patch implementing reaching definitions
calculation for
C++](http://lists.llvm.org/pipermail/cfe-dev/2020-March/064913.html) and is
seeking feedback.

* Ties Stuij proposes [adding a new bfloat IR type for the C bfloat16 format
in Armv8.6-a](http://lists.llvm.org/pipermail/cfe-dev/2020-March/064948.html).
Respondents discussed whether an IR type was necessary.

* Evandro Menezes shared a [draft proposal for a compact code model for
RISC-V](http://lists.llvm.org/pipermail/llvm-dev/2020-March/140109.html).


## LLVM commits

* The register data flow (RDF) framework was moved from the Hexagon backend to
the shared CodeGen library, to enable it to be used by other targets.
[080dd10](https://reviews.llvm.org/rG080dd10f7df).

* Known bits constant folding was removed on the basis that it is incredibly
expensive but almost never has an impact on generated code. As a further
follow-up, the ExpensiveCombines option was removed altogether.
[2b52e4e](https://reviews.llvm.org/rG2b52e4e629e),
[dc81923](https://reviews.llvm.org/rGdc81923659c).

* Lit gained support for flaky tests through the `ALLOW_RETRIES` keyword.
[f951b0f](https://reviews.llvm.org/rGf951b0f82df).

* Documentation was added to explain loop rotation.
[7fa2045](https://reviews.llvm.org/rG7fa204580df).

* The second in a series of patches to enable basic block sections (one BB per
ELF section) was committed. [df082ac](https://reviews.llvm.org/rGdf082ac45aa).

* Arm learned to spill extra registers when compiling for `-Oz` in cases where
inter-procedural register allocation may benefit from this.
[73cea83](https://reviews.llvm.org/rG73cea83a6f5).

* The RISC-V backend gained improved codegen for materialising +0.0 floating
point immediates. [3c24aee](https://reviews.llvm.org/rG3c24aee7ee8).


## Clang commits

* A tablegen backend was added to generated builtins and a header for SVE.
[8b409ea](https://reviews.llvm.org/rG8b409eabaf7).

* Support was added for the `-mdouble=x` flag to set the width of double types
for AVR. [4add249](https://reviews.llvm.org/rG4add2492055).

* clang-format can now handle C# generic type constraints.
[dcbcec4](https://reviews.llvm.org/rGdcbcec4822f).

* The Clang driver now accepts and `-mstall-data-limit` argument for RISC-V,
which will put global and static data smaller than the limit into a special
section. [fc37526](https://reviews.llvm.org/rGfc3752665f4).


## Other project commits

* libc gained implementations of `memcpy`, `sigaction`, and `signal`.
[04a309d](https://reviews.llvm.org/rG04a309dd0be),
[4d35055](https://reviews.llvm.org/rG4d35055635a),
[ca04d0c](https://reviews.llvm.org/rGca04d0c8fd2).

* libc now has a range of Arm optimised routines.
[0928368](https://reviews.llvm.org/rG0928368f623).

* MLIR gained support for out of tree projects embedding it using CMake.
[7ca473a](https://reviews.llvm.org/rG7ca473a27bd).