LLVM Weekly - #477, February 20th 2023

Welcome to the four hundred and seventy-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 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 and events

Registration for the 2023 EuroLLVM Developers' Meeting is now open.

An in-personal LLVM meetup will be held on Feb 25th in Wuhan, China. A meetup will also be taking place in Bangalore on the same day.

Jonas Hahnfeld writes about making enough of Cling and ROOT work on RISC-V to re-discover the Higgs boson.

The /r/cpp Reddit moderators have posted a trip report from the 2023-02 Issaquah ISO C++ committee meeting (highlight: C++23 is done!).

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

• Office hours with the following hosts: Kristof Beyls, Johannes Doerfert.
• Online sync-ups on the following topics: Flang, LLVM security group, OpenMP, loop optimisation, OpenMP in Flang, MLIR, and SPIR-V.
• For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.

On the forums

• The first LLVM Foundation strategic planning session will be held on Feb 27th/28th, focusing on grants and scholarships.

• Nick Desaulniers announced that the work to match GCC’s support for asm goto is complete.

• A public Google calendar is now available for MLIR open meetings.

• Renato Golin proposed that LLVM sub-directories provide up-to-date README.md files to aid navigation and discoverability, particularly for people using a web UI like GitHub.

• Piotr Zegar started an RFC discussion on excluding issues from system headers as early as possible in clang-tidy.

• Alex Bradbury posted an RFC on resolving issues related to extension versioning in RISC-V.

• The RFC from Vasileios Porpodas on lightweight LLVM IR checkpointing generated a lot of discussion this week, with some concerns raised about the support burden and whether it might encourage inefficient implementation approaches.

• Christudasan Devadasan suggested introducing a generic predicated COPY opcode for targets where a COPY operation is more than just a copy between two registers.

LLVM commits

• The CallBrPrepare pass was introduced. fb47115, 0a39af0, 094190c, 28d45c8, 5cc1016, a3a84c9.

• A build for Windows on Arm was added to the LLVM release packaging script. c5e1000.

• New pass manager support was added to the HardwareLoops pass. 2a58be4.

• MC layer support was added for the RISC-V vendor-specific XTHeadBs and XTHeadBb, and XTHeaadMAC extensions. Initial support was also added for Zfa. 04a2baf, fc02eeb, d4012bc, c0947dc, df56b55.

• PPC’s GISel gained support for fpconstant. 6ee2f77.

• The hasBitPreservingFPLogic hook was removed. 09dd4d8.

• Additional parts of the llvm-debuginfo-analyzer implementation were committed. 7fbcc24.

• Zicsr and Zifencei extensions are now accepted as command-line options in the RISC-V backend, increasing compatibility with GCC. 22e199e.

• The PlaceSafepoints pass was ported to the new pass manager. 1ceb79e.

Clang commits

• Documentation was added for clang-scan-deps -format=p1689. 9c4f0d8.

• The deprecated -fmodules-ts flag was removed. 612f3ac.

• Clang now supports WebAssembly externrefs. 890146b.

Other project commits

• LLVM’s libc gained a loader utility for AMDHSA architectures for testing. 67d78e3.

• Thread-safety annotations were added to the Scudo allocator. 6a4c395.

• An RFC on -fstack-arrays was committed to the Flang documentation. 5922b88.

• HLFIR array constructor lowering started to land in Flang. ffde9f1, a9e4bb3.

• LLDB now has architecture-specific watchpoint behaviour defaults. eaeb8dd.

• LLDB support for Renderscript was removed, as it is deprecated in Android. 17e2497.