LLVM Weekly - #413, November 29th 2021

Welcome to the four hundred and thirteenth 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. 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@asbradbury.org, or @llvmweekly or @asbradbury on Twitter.

News and articles from around the web

I didn’t spot anything this week. As always, tips via email are greatly appreciated!

On the mailing lists

• James King posted an RFC on improving support for debugging Clang’s AST matchers.

• Dmitry Makogon proposed introducing new intrinsics for memory comparison operations such as memcmp.

• Simon Pilgrim shared an RFC to raise the minimum Visual Studio version to VS2019.. All respondents so far have been in favour.

• The LLVM bugzilla migration is underway. After much discussion about details of the conversion, Anton Korobeynikov shared a repository set up to act as a preview. Status of the migration can be tracked in this Google Doc. Anton has also sent a note to flag that people who filled out the Bugzilla transition survey (i.e. indicated they’d like to associate their Bugzilla email with a GitHub account) but aren’t LLVM committers can expect an invitation to join the LLVM GitHub organisation.

• Bardia Mahjour shared notes and outcomes from the Future of the Loop Optimization Working Group roundtable.

• Krishna (Chaitanya) Sankisa posted an RFC on allowing bitcasts between address spaces with the same point size.

• The TLX ‘Tensor LLVM eXtensions’ proposal generated more discussion. Florian Hahn posted a series of questions which were answered by Akash Kothari, and Christ Lattner shared some additional feedback.

LLVM commits

• Parallel chunk processing was added to llvm-reduce, significantly speeding up reductions for very large inputs. 8ef460f.

• Best practices for configuring a fast builder were documented. 73d52ee.

• The order of restoring callee-saved registers was reversed for the RISC-V backend, maximising the distance between the load of the return address and its use. 137d347.

Clang commits

• Support was added for -fplugin-arg- to pass arguments to plugins. 3e67cf2.

• The file documenting the clang-format status of each file in the repo was updated. 3c8666e.

Other project commits

• ThreadSanitizer switched to a new runtime offering 2x smaller shadow memory and faster fully vectorized race detection amongst other features. 66d4ce7.

• std::{strong,weak,partial}_order were implemented in libcxx. d8380ad.

• LLDB formatters were added for libstdc++ unordered_map, unordered_set, unordered_multimap, unordered_multiset, and optional. fcd288b, e3dea5c.

• Patches to support mutli-root PDL patterns for kernel matching in MLIR were committed. 842b686, 3eb1647, 6df7cc7, a76ee58.