[llvm-dev] LLVM Weekly - #401, September 6th 2021

[Alex Bradbury via llvm-dev]

LLVM Weekly - #401, September 6th 2021
======================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/401>.

Welcome to the four hundred and 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
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

Tanya Lattner provided a [summary of upcoming
events](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152483.html)
within the LLVM community.

JeanHeyd Meneide has summarised [recent progress on the ISO C23
standard](https://thephd.dev/c-the-improvements-june-september-virtual-c-meeting).

MaskRay has blogged about [building glibc with LLD
13](https://maskray.me/blog/2021-09-05-build-glibc-with-lld).


## On the mailing lists

* Sanjay Patel posted a [helpful summary of the intrinsic llvm::isnan
  discussion](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152431.html),
  and Serge Pavlov has now [initiated a new thread to discuss the path
  forwards](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152455.html).

* Nikita Popov is [seeking input on opaque pointers and i8
  GEPs](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152486.html).
  "My proposal here is that in opaque pointers mode, LLVM should consider i8
  GEPs canonical for GEPs with constant offsets. We should not attempt to
  'guess' a good GEP type to use, and we should not try to generate complex
  GEP structures if a simple one will do. I don't think there's really any
  disadvantages to this, apart from the fact that it makes the discrepancy
  between typed and opaque pointer mode larger."

* Evgueni Brevnov posted an RFC on [introducing a new call-site
  attribute](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152429.html)
  to provide greater flexibility than a single per-translation unit code
  model. Philip Reames [proposed a slightly more generalised
  formulation](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152448.html).

* Luke Benes [asked if clang would follow GCC 11 in adopting a recent change
  to
  `-Wnonnull`](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152437.html).

* ORC JIT Weekly #38 [is
  out](https://lists.llvm.org/pipermail/llvm-dev/2021-September/152496.html),
  highlighting developments since early August.


## LLVM commits

* A new tutorial was added on making your first change to LLVM.
  [3a6b722](https://reviews.llvm.org/rG3a6b722db856).

* Setjmp/longjmp support was implemented for WebAssembly.
  [28780e5](https://reviews.llvm.org/rG28780e59f615).

* Initial AArch64 JITLink support was committed.
  [2ed91da](https://reviews.llvm.org/rG2ed91da0f1f3).

* CMake targets for code coverage reports were added.
  [2856719](https://reviews.llvm.org/rG2856719d74f0).

* Support was added for a new LLVM-specific DWARF annotation.
  [89424a8](https://reviews.llvm.org/rG89424a829f3c).

* The LLVM_ENABLE_RUNTIMES build option was documented.
  [d396d09](https://reviews.llvm.org/rGd396d09fc227).

* A new -print-pipeline-pass option was added to opt.
  [c71869e](https://reviews.llvm.org/rGc71869ed4c24).

* The deprecation of the legacy pass manager deprecation was documented.
  [2413d60](https://reviews.llvm.org/rG2413d6063b78).

* The llvm.isnan patchset was reverted pending the conclusion of the RFC on
  llvm-dev. [3f1f08f](https://reviews.llvm.org/rG3f1f08f0ed6a).


## Clang commits

* A `-canonical-prefixes` option was added.
[3d157cf](https://reviews.llvm.org/rG3d157cfcc4ef).

* Loop unrolling was added to the OpenMPIRBuilder.
  [650bbc5](https://reviews.llvm.org/rG650bbc56203c).


## Other project commits

* The MLIR Cpp emitter was upstreamed.
  [2f0750d](https://reviews.llvm.org/rG2f0750dd2ec0).

* An initial implementation of std::formatter was added to libcxx.
  [d7444d9](https://reviews.llvm.org/rGd7444d9f41e3).

* LLDB gained a follow-fork-mode setting.
  [4a2a947](https://reviews.llvm.org/rG4a2a947317bf).

* LLVM's libc gained a skeleton for the C standard condition variable
  functions. [2f4f452](https://reviews.llvm.org/rG2f4f452f166b).

* The MLIR C/Python API was extended to allow for CFG construction.
  [8e6c55c](https://reviews.llvm.org/rG8e6c55c92c80).