[llvm-dev] LLVM Weekly - #408, October 25th 2021

[Alex Bradbury via llvm-dev]

LLVM Weekly - #408, October 25th 2021
=====================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/408>.

Welcome to the four 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

Registration is now open for the [2021 LLVM Developers'
Meeting](https://llvm.swoogo.com/2021devmtg/) and the schedule has been
posted. It will be a 4 day online event, Tuesday 16th November 2021 - Friday
19th November 2021.

Krister Walfridsson blogged about [optimisations enabled by
-ffast-math](https://kristerw.github.io/2021/10/19/fast-math/).


## On the mailing lists

* Ellis Hoag shared an RFC on [adding a lightweight variant of IR
  instrumentation profile-guided optimisation
  (IRPGO)](https://lists.llvm.org/pipermail/llvm-dev/2021-October/153317.html),
  intended to be suitable for PGO on mobile devices.

* Florian Hahn provided an [update on the RFC to add a new set of vector
  builtins](https://lists.llvm.org/pipermail/cfe-dev/2021-October/069147.html),
  linking to the current patches under review. He hopes to land them this
  week.

* Björn Pettersson followed up on a discussion about non-determinism in
  DominatorTree, JumpThreading, and EarlyCSE with a [summary of potential
  paths
  forward](https://lists.llvm.org/pipermail/llvm-dev/2021-October/153356.html).


## LLVM commits

* ThinLTO's caching was moved to the LLVM Support library so it can be used
  elsewhere in LLVM. [e678c51](https://reviews.llvm.org/rGe678c5117710).

* An initial draft policy around creating new git repos and granting write
  access to them was added.
  [dcc91dd](https://reviews.llvm.org/rGdcc91dd2a798).

* A scheduling model was added for Power10.
  [67c64d8](https://reviews.llvm.org/rG67c64d83378e).

* An experimental new option for the new pass manager was added,
  eagerly-invalidate-analyses. This will decrease maximum memory usage at the
  cost of higher compile time by eagerly invalidating function analyses.
  [b8ce973](https://reviews.llvm.org/rGb8ce97372d85).

* llvm-reduce gained reduction passes to reduce operands to undef/1/0.
  [9660563](https://reviews.llvm.org/rG9660563950aa).

* ASM parser support was committed for the CSKY basic integer instruction set
  [de10a02](https://reviews.llvm.org/rGde10a02fc067).


## Clang commits

* A number of tests that are tied to the legacy pass manager were removed.
  [cb5a101](https://reviews.llvm.org/rGcb5a10199b32).

* It's now possible to run a Clang plugin if specified on the command line
  before the main action. [fe66433](https://reviews.llvm.org/rGfe66433fe119).


## Other project commits

* A range of utility functions were added to FIRBuilder.
  [f17f694](https://reviews.llvm.org/rGf17f694a0fcf),
  [45503fc](https://reviews.llvm.org/rG45503fc04449),
  [c983aed](https://reviews.llvm.org/rGc983aeddcf5a),
  [a2e7af7](https://reviews.llvm.org/rGa2e7af75166d).

* LLVM's libc gained implementations of atof, strtof, and strtod.
  [87c0160](https://reviews.llvm.org/rG87c016078ad7).

* A short document was started to record deliberate differences between LD64
  and lld-macho. [6b715e9](https://reviews.llvm.org/rG6b715e9c4d9c).

* A "command container" hierarchy was added to LLDB, enabling users to
  organise their commands in a hierarchy rather than having to stick to just
  top-level commands. [c5011ae](https://reviews.llvm.org/rGc5011aed9c29).

* The new "runtimes" build is now the default way of building libc++.
  [79175f3](https://reviews.llvm.org/rG79175f336c1f).

* The unused parallel-libs project was removed.
  [db0486c](https://reviews.llvm.org/rGdb0486c46fe1).