Alex Bradbury via llvm-dev
2021-Jun-21 17:57 UTC
[llvm-dev] LLVM Weekly - #390, June 21st 2021
LLVM Weekly - #390, June 21st 2021
=================================
If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/390>.
Welcome to the three hundred and ninetieth 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
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@llvmweekly or @asbradbury on Twitter.
## News and articles from around the web
Uma Srinivasan will be presenting "From Packing Decimals With Cobol to
Optimizing Tweets With Scala: A Journey Through Space, Time, & Culture with
Compilers" at the [Women in Compilers and Tools June
Meetup](https://www.meetup.com/meetup-group-ifwtlvwd/events/278899544/). June
24th, 6pm PDT.
A new book on LLVM has been published - [Learn LLVM 12 by Kai
Nacke](https://www.packtpub.com/product/learn-llvm-12/9781839213502).
## On the mailing lists
* The [thread suggesting a migration to
Discourse](https://lists.llvm.org/pipermail/llvm-dev/2021-June/150823.html)
has seen continued discussions. To pick a few messages:
* Christian Kühnel
[shared](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151172.html)
a [draft migration
user-guide](https://github.com/llvm/llvm-iwg/blob/main/discourse_migration/userguide.md).
* James Y Knight
[reported](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151150.html)
that the [Open Source Community
Infrastructure](https://www.osci.io/tenants/) would be willing to provide
Mailman3 hosting.
* John McCall provided a [summary of issues with mailing
lists](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151215.html).
"Now, forums have their own usability annoyances, without question.
[...]
My point is that those problems should not be treated as blockers when we
have equal or worse problems with mailing lists that we've just come to
accept."
* Reid Kleckner [summarised responses to the RFC on
LLD-as-a-library](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html).
* Tom Stellard announced that [12.0.1-rc2 has been
tagged](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151223.html) and
an extended deadline for requesting backports.
* Matt Morehouse responded to an old thread on first-class metadata with a
[list of potential use
cases](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151198.html).
* Gulfem Savrun Yeniceri
[proposes](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151154.html)
adding a binary id to profiles, in order to aid matching executables to
profiles.
* John McCall responded to the RFC thread on byte types in LLVM, [summarising
how this may relate to work to add a provenance model to
C](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151199.html), and
arguing that it would be better to start by considering inttoptr and
ptrtoint casts.
* Luke Drummond started a conversation about [when it is appropriate to use the
[NFC] tag](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151234.html).
* LLVM GPU News Issue #14 [is
out](https://lists.llvm.org/pipermail/llvm-dev/2021-June/151294.html).
* Kito Cheng posted an [RFC on providing a #pragma to implement the
riscv_vector.h
contents](https://lists.llvm.org/pipermail/cfe-dev/2021-June/068340.html),
avoiding the parsing of ~60k lines. David Rector [pointed
to](https://lists.llvm.org/pipermail/cfe-dev/2021-June/068346.html) recent
work to solve a similar problem in OpenCL.
## LLVM commits
* A CustomBehaviour class was added llvm-mca, intended to allow developers to
implement modelling for instructions that require special handling.
[f7a23ec](https://reviews.llvm.org/rGf7a23ecece52).
* The SpeculateAroundPHIs pass was removed, with the commit message noting
some of the regressions observed with the NewPM transition may have been
caused by it. [e523645](https://reviews.llvm.org/rGe52364532afb).
* `DW_CFA_LLVM_` was added, as part of the work to add extensions for
heterogeneous debugging on AMDGPU.
[167e7af](https://reviews.llvm.org/rG167e7afcd52b).
* DebugInfo handling was added for IR outlined functions.
[2c21278](https://reviews.llvm.org/rG2c21278e7471).
* Initial GlobalISel infrastructure was added for M68k.
[2193347](https://reviews.llvm.org/rG2193347e72fa).
* Relocation emission for RISC-V was refactored and improved, bringing it more
closely in line with GNU as.
[bbea642](https://reviews.llvm.org/rGbbea64250f65).
* The MIRPrinter gained machine metadata support.
[b9c05af](https://reviews.llvm.org/rGb9c05aff205b).
## Clang commits
* Improvements were made for named return value optimisation.
[12c90e2](https://reviews.llvm.org/rG12c90e2e25df).
* The performance-unnecessary-copy-initialization checker was updated to fix
some false positive cases.
[bdd5da9](https://reviews.llvm.org/rGbdd5da9dec61).
## Other project commits
* EmitC, an MLIR dialect for emitting C++, was upstreamed to MLIR.
[876de06](https://reviews.llvm.org/rG876de062f946).
* Identical code folding was implemented in lld-macho.
[f27e454](https://reviews.llvm.org/rGf27e4548fc42).
* An implementation of a two-level distributed barrier was added to LLVM's
OpenMP library. [25073a4](https://reviews.llvm.org/rG25073a4ecfc9).
* LLVM's libc gained implementation of a set of abstract elementary
operations
acting on fixed chunks of memory, intended to be used as building blocks for
higher level abstractions.
[454d92a](https://reviews.llvm.org/rG454d92ac3b3b).