LLVM Weekly - #647, May 25th 2026
Welcome to the six hundred and forty-seventh 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 https://llvmweekly.org and pass it on to anyone else you think may be interested. Please send any tips or feedback via email: asb@asbradbury.org, or Mastodon: @llvmweekly@fosstodon.org / @asb@fosstodon.org, or Bluesky: @llvmweekly.org / @asbradbury.org.
News and articles from around the web and events
The Beijing LLVM meetup will take place on May 29th and feature two RISC-V focused talks.
The next Cambridge (UK) Compiler Social will take place on Thursday 4th June at the Computer Laboratory and feature a talk from Lana Josipović, “From Software Programs to Digital Circuits”.
According to the LLVM Calendar in the coming week there will be the following:
- Office hours with the following hosts: Johannes Doerfert, Amara Emerson.
- Online sync-ups on the following topics: Flang, modules, lifetime safety, LLVM/Offload, OpenMP for flang, HLSL, reflection.
- For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.
On the forums
Aaron Ballman is seeking to organise a testimonial to ISO on the importance of open access to ISO standards documents on behalf of the LLVM community. Per the timeline, please leave comments and recommended edits on the linked draft through to May 27th.
Reid Kleckner proposed transitioning from reST to Markdown for LLVM documentation. There’s a lot of support for this direction, but also some concerns about the churn, packaging issues, and the volume of existing reST documentation.
Vladimir Makaev started an RFC discussion on making clang-tidy’s
--header-filterimprove speed by disabling the AST matcher for matching files. Currently it controls only which diagnostics are displayed.Luke Lau shares that lnt.llvm.org is now tracking RISC-V performance for clang and GCC. Now that the official LLVM-hosted LNT instance is back up, reporting has moved from Igalia’s instance. Even more importantly, Luke gives a really great quick start guide on how to navigate the web interface and interpret the results.
There was further discussion on the requirements on bare-metal toolchain multilibs layouts with Petr Hosek sharing a history of previous discussions about the current layout.
Rahul Joshi is looking for input on a change in ovelroaded types for intrinsics, outlining three potential paths forward.
Trung Nguyen kicked off a discussion on adding support for the old GCC2 C++ ABI, motivated by projects like HaikuOS that need ABI compatibility.
Varad Rahul Kamthe posted an RFC on supporting default arguments in LLVM intrinsics as a way to help avoid breaking changes when new arguments are added to intrinsics.
LLVM 22.1.6 was released.
LLVM commits
GlobalISel match tables were reduced in size by up to 25% (in the case of AMDGPU) by performing additional optimisation. 06d50ac.
ISA mapping symbols are now used for per-region disassembly of RISC-V. This means that
-mattr=...only affects regions that don’t have an ISA mapping symbol. 041f41b.LLVM’s Unicode tables were updated to Unicode 18.0. 45426cc.
A new
-epilogue-tail-folding-policyflag was added. 499b2fa.The SLP Vectorizer learned to vectorise struct-returning intrinsics. 074b6be.
Windows Structured Exception Handling is now supported for the Arm target when building with Clang in MSVC mode. 6c34ed7.
Clang commits
breakandcontinueare now disallowed in loop conditions. 8a3f021.The MSVC driver will now use LLD as the linker if DWARF is requested. cdc2749.
A CallConvLowering pass was added for ClangIR. cfc03d6.
clang-tidy learned to detect uses of
llvm::isathat are aways true. 5a51136.