LLVM Weekly - #667, October 12th 2026

Welcome to the six hundred and sixty-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

Prasoon Kumar wrote on the LLVM Project blog about their GSoC project to improve lit.

Registration for the 2026 LLVM Developers' Meeting closes on October 16th.

The next Women in Compilers and Tools meetup will take place on October 16th. Ankita Nayak will present “Agentic Kernel Generation for Diverse AI Accelerators”.

According to the LLVM Calendar in the coming week there will be the following:

• Office hours with the following hosts: Clang maintainers, Alexey Bader, Alina Sbirlea, Kristof Beyls.
• Online sync-ups on the following topics: Flang, LLVM qualification, lifetime safety, massive binaries, modules, LLVM/Offload, BOLT, pattern matching, 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

• The Clang area team have accepted the RFC to enable the ClangIR build by default, although building with ClangIR disabled will still be a supported configuration for the forseeable future.

• Alex Langford started an RFC discussion on rewriting LLDB’s debugserver (the debug stub for Apple platforms) in Swift.

• The 78th edition of the MLIR newsletter is now available, giving plenty of detail on recent notable RFCs and commits.

• Simon Tatham posted a second take on an RFC for fixing function size estimation for Arm.

• Fangrui Song provided an update on making RegAllocFast consume MachineIR in SSA form.

• There’s been substantial further discussion on the RFC to forbid AI-generated communication. Relatedly, an anonymous maintainer workload survey was proposed.

• LLVM 23.1.3 was released.

• Nikita Popov proposes explicitly specifying the bitwidth for zeroext/signext annotations which can be ambiguous currently.

• Nico Weber would like to add Chromium C++ code to CTMark.

LLVM commits

• X86 and AArch64 command line option definitions were moved to TableGen. 2771c75, 7bc59c9.

• It’s now possible for targets to add a MachineScheduler before PHI elimination (i.e. in SSA mode). c01b6605.

• RegAllocFast can now lower tied operands meaning the TwoAddressInstructionPass doesn’t need to be run for it. 8ad6c58, 82046be.

• The constexpr GEP APIs are deprecated. 5b07ba7.

• SystemZ support for .insn was expanded. 0e7e59d.

• IRBuilder is being moved to take a Module for construction as it needs access to a datalayout. ecc201f.

• AArch64 return address authentication hardening was implemented. 645c5b1.

• An @llvm.mask.beforefirst intrinsic was added. 701fe27.

• An -instnamer-after-each-pass option was added to name unnamed arguments, basic blocks, and non-void instructions making text snapshots easier to compare. fefeef2.

Clang commits

• HLSL interpolation modifiers are now supported. c4d9267.

• -Wunsafe-buffer-usage will now warn on annotated unsafe container construction. f6ccb23.

• clangd now supports dynamic plugins. 9f3af63.

Other project commits

• LLVM’s libc gained optimised hot paths for exp2f and exp10f. 643e9dc.

• libcxx now has an implementation of <debugging> featuring is_debugger_present and is_replaceable. e65c4e3.

• The process for testing LLDB with WebAssembly was documented. c6c3eac.

• Documentation was added for LLDB’s Data Inspection Language (DIL). 05b62b2.