LLVM Weekly - #664, September 21st 2026
Welcome to the six hundred and sixty-fourth 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.
A little bit off-topic, but today is notable for being the 25th anniversary of the founding of Igalia. All this time later, we’re now heading towards 200 people working across huge swathes of the open source software stack. I’ve only been an Igalian for a comparatively short ~4.5 years but am proud to have been part of the story so far. Here’s to the next 25 years!
News and articles from around the web and events
Maria Fernanda Guimarães wrote on the LLVM blog about Improving HLSL Support in clangd and the progress made as part of GSoC.
Fangrui Song wrote about linker I/O tricks and their downsides.
According to the LLVM Calendar in the coming week there will be the following:
- Office hours with the following hosts: Kristof Beyls, Amara Emerson.
- Online sync-ups on the following topics: formal specification, pointer authentication, OpenMP, Flang, RISC-V, LLVM libc, HLSL, LLVM libc math.
- For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.
On the forums
LunaTheFoxgirl proposed the upstreaming of a Renesas SuperH backend.
The agenda has been announced for the LLVM/Offload workshop.
The LLVM security response group is proposing to add the idea of a ‘vendor observer’ who could attend meetings but not have voting rights.
Brooks Moses started a discussion about an LLVM libc dynamic loader for Linux.
Stephen Tozer provided an update on planned function-local metadata work.
Adam Siemieniuk shared an MLIR RFC on adding
vector.scaled_contract.Jules Merckx proposed a new MLIR dialect,
matchwhich would sit betweenpdlandpdl_interpand allow representing the scheduling of PDL constraints.Jinjie Huang kicked off an RFC thread on BRay, a tracing solution based on BOLT instrumentation.
Yashwant Singh shared a write-up of scripts and a dashboard for monitoring LLVM cost modeling.
Yassine is working on improving Windows asynchronous structured exception handling support and is seeking input.
Steffen Larsen wrote up an RFC on a replacement CLI library for LLVM and tools, which resulted in an alternative proposal from Fangrui Song.
Jiaxun Yang posted an RFC on handling multiple encoding families for Mips.
LLVM commits
The ESP32 S3 target was added for the Xtensa backend. 6a8b946.
The RISC-V backend learned to rewrite an ADD to SUB if the negated constant is already present in the DAG. 6e071ab.
llvm.pseudoprobewas documented in the LangRef. d86120d.TargetOptions::ThreadModelwas replaced with a module flag and anexception-modelmodule flag was also added. e733ceb, fe47933.llvm.[su]mulhintrinsics were added. 4510d55.A
--rerun-failed-seriallyoption was added tolit. 49923e9.LLVMToolSessionwas introduced, allowing a single process to initialise and invoke registered LLVM tools without constructing and destroyingInitLLVMfor every call. fce3fac.Speculative load intrinsics were added. 7e57486.
Clang now supports friend declarations with dependent nested-name-specifiers. 2e78e25.
Clang commits
Address space attributes were added for SYCL. c476f80.
A function frame allocator was added for the Clang bytecode interpreter. 66ccc4c.
clang-tidy docs moved to the Furo theme like most other LLVM subprojects. d4a85ae.