LLVM Weekly - #587, March 31st 2025

If you prefer, you can read a HTML version of this email at https://llvmweekly.org/issue/587.

Welcome to the five hundred and eighty-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

“walnut356” blogged about an attempt to implement LLDB’s TypeSystem implement for Rust (TypeSystemRust).

JP Lehr announced that MetaCG development has now moved out into the open. MetaCG offers an annotated whole program call-graph tool for Clang/LLVM.

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

• Office hours with the following hosts: Quentin Colombet, Johannes Doerfert, Renato Golin.
• Online sync-ups on the following topics: Flang, modules, LLVM/Offload, Clang C/C++ language working group, SPIR-V, OpenMP for Flang, HLSL, memory safety working group, MLGO.
• For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.

On the forums

• Peter Collingbourne published a set of pointer authentication code or memory safety related RFCs: the structure protection family of UAF mitigation techniques, deactivation symbols, and emulated PAC.

• Vasileios Porpodas provided an update on the Sandbox Vectorizer project, noting that IR coverage is at 90% and the vectorizer is stable enough to compile and run the llvm-test-suite and clang as a workload.

• Mike Urbach raised the issue of overflow of orderIndex in MLIR for very large (100s of millions of ops!) basic blocks.

• Tom Stellard has a proposed incident response guide aimed for LLVM project admins looking to handle a security incident.

• Yingwei Zheng shared news of clang-i18n, a plugin for a dynamically linked clang/LLVM to translate diagnostic messages to other languages.

• Florian Mayer proposed adding a ‘review notes’ bot which would flag things for reviewers to consider based on predefined rules.

• Andrzej Warzynski is working to document stacked PR practices.

• The issue of report_fatal_error and whether it should emit backtraces by default was raised again, still with strongly differing viewpoints.

• Yeoul Na is looking for feedback on a proposal to allow forward-referencing a struct member without bounds annotations.

• Balazs Benics gave a report on upgrading Z3 from 4.13.0 to 4.14.1, nothing that runtime characteristics remain roughly the same.

• “dpthinker” asked about why applying BOLT to libart.so on Android devices didn’t seem to show much improvement and received good advice.

• ChuanqiXu updated their proposal for extensions to export macros/preprocessor states for C++20 modules.

• Alex Zinenko proposed allowing arbitrary vector element types in MLIR, following on from the previous RFC on allowing pointers as vector element types.

• Orlando Cazalet-Hyams is putting out a call for final feedback / suggested path forward for the is_stmt placement for better debugging RFC.

• Rolf Morel made an MLIR RFC on generalising TilingInterface and tileUsingSCF driver to operate on ShapedType.

LLVM commits

• A Mustache Templating Language parser was added to llvm/Support. ece59a8.

• Documentation was added for the sandbox vectorizer. 31fe0d2.

• A new late branch optimisation pass was added for RISC-V, cleaning up conditional branches that can be statically evaluated with an unconditional branch. d8e44a9.

• Copy and pasting a failing command from a lit test is now ever so slightly easier, as RUN: at line N: was moved to a comment after the command, allowing the command to be directly copied without deleting the prefix. 8d3dc1e.

• SystemZ started to implement the isCopyInstrImpl hook. c0a7ccb.

• The llvm-mca -instruction-tables option now accepts verbosity levels. f4bb9b5.

• .option [no]exact is now supported for RISC-V assembler input. 6a371c7.

• The static data splitter pass gained some support for constant pool partitioning. 9747bb1.

Clang commits

• The _Countof operator from C2y is now implemented, and provided as an extension in earlier C language modes. 00c43ae.

• Binary operators were implemented in ClangIR. 2f3c937.

• The alpha.core.FixedAddressDereference checker is no longer marked as alpha. 322b2fe.

• Clang’s requirements for freestanding builds (-ffreestanding) were documented. Notably, 85c54a5.

Other project commits

• LLD’s ELF linker now has a --why-live flag much like the Mach-O linker, which prints the reasons symbols matching the given globs survived GC. 074af0f.

• Experimental support was added for compiling flang-rt directly for the GPU, similar to the method used for libc and libc++. 85974a0.

• In libclc, a number of helpers were moved to the CLC library. 70c325b, d46a699, 3013458, 3284559, and more.

• LLDB started to provide a statusline that displays information about the current state of the debugger at the bottom of the screen. 9c18edc.

• OpenMP was enabled for the Haiku OS. 9b7a7e4.