[llvm-dev] LLVM Weekly - #391, June 28th 2021

Mon Jun 28 14:14:31 PDT 2021

LLVM Weekly - #391, June 28th 2021
==================================

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<http://llvmweekly.org/issue/391>.

Welcome to the three hundred and ninety-first 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
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@llvmweekly or @asbradbury on Twitter.

## News and articles from around the web

No particular news to highlight this week.

## On the mailing lists

* Leonard Chan started an RFC discussion on [building LLVM tools into a single
  binary
  (busybox-style)](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151321.html),
  and followed up with a [WIP
  prototype](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151404.html).

* Tom Stellard proposed [only changing the libclang.so SONAME when the ABI
  changes](https://lists.llvm.org/pipermail/cfe-dev/2021-June/068423.html).

* LLVM 12.0.1-rc3 [has been
  tagged](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151530.html).

* Andrew Kaylor started a thread about [floating point variance in the test
  suite](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151441.html),
  noting that it's still the case that some tests fail if the floating point
  calculations don't exactly match the reference results.

* Nick Desaulniers created an RFC about [inlining and mismatched function
  attributes](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151509.html),
  noting several cases where inlining can produce unexpected or surprising
  results.

* Luke Drummond helpfully [summarised the various
  responses](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151440.html)
  on the thread about appropriate use of the 'NFC' tag.

* Arthur Eubanks initiated a discussion on [ABI attributes on arguments vs
  parameters](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151411.html).

* Alexander Yermolovich is seeking feedback on [refactoring llvm-dwp into a
  library](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151344.html) in
  order to aid the implementation of BOLT.

* Arthur Eubanks is [advertising for help in completing the opaque pointers
  implementation
  plan](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151310.html).

* There's been yet more discussion on moving the LLVM mailing lists to
  Discourse. Aaron Ballman [raised a concern about fracturing the
  community](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151429.html).

* Anirudh Prasad proposed [a new mechanism for tieing a particular inline asm
  operand to a specific
  register](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151370.html),
  that has also been proposed in GCC. Responses so far have been positive.

* David Spickett sent an [update on the patches adding AArch64 memory tagging
  support to
  LLDB](https://lists.llvm.org/pipermail/lldb-dev/2021-June/016924.html),
  nothing they are awaiting review.

## LLVM commits

* A new flag was added to force all pointers to be opaque pointers, in order
  to help with testing. [4c8174f](https://reviews.llvm.org/rG4c8174f54b4e).

* The AMDGPU backend gained a new pass to optimise the live ranges of VGPRs.
  [208332d](https://reviews.llvm.org/rG208332de8abf).

* The IR verifier will now fail on overrunning and invalid indices for the
  insert/extract vector intrinsics.
  [3c4dbf6](https://reviews.llvm.org/rG3c4dbf6ea9a0).

* An initial implementation of llvm-sim, an IR similarity visualisation tool,
  was committed. [9e73f7c](https://reviews.llvm.org/rG9e73f7c8d2d7).

* New documentation was added on the use of opt and the new pass manager.
  [e15673d](https://reviews.llvm.org/rGe15673df2797).

## Clang commits

* clang-format now has basic support for formatting JSON.
  [8b7881a](https://reviews.llvm.org/rG8b7881a084d0).

* Install targets were created for scan-build-py.
  [d9cf829](https://reviews.llvm.org/rGd9cf8291e7ef).

* clang-format gained a new LambdaBodyIndentation option and an IfMacros
  option (a list of macros that should be interpreted as conditionals instead
  of function calls). [64cf5eb](https://reviews.llvm.org/rG64cf5eba06bd),
  [be9a87f](https://reviews.llvm.org/rGbe9a87fe9bc3).

## Other project commits

* A Bazel build configuration was added to the repo, following approval of
  [the proposal to do
  so](https://github.com/llvm/llvm-www/blob/main/proposals/LP0002-BazelBuildConfiguration.md).
  [4aeb2e6](https://reviews.llvm.org/rG4aeb2e60df98).

* LLDB can now use LLVM's demangling library to demangle symbols using Rust's
  v0 scheme. [0a2d4f3](https://reviews.llvm.org/rG0a2d4f3f24a3).

* The DFSan shadow and origin memory layouts were modified to match MSan.
  [45f6d55](https://reviews.llvm.org/rG45f6d5522f8d).

* Benchmarks for memcmp and bzero were added to LLVM's libc.
  [87065c0](https://reviews.llvm.org/rG87065c0d242d).

* Libcxx's status ranges implementation status page was updated.
  [e7091da](https://reviews.llvm.org/rGe7091da10b30).

* MLIR's async-parallel-for pass was updated to implement recursive async work
  splitting for scf.parallel operations.
  [86ad0af](https://reviews.llvm.org/rG86ad0af87054).