LLVM Weekly - #362, December 7th 2020

Welcome to the three hundred and sixty-second 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 to asb@asbradbury.org, or @llvmweekly or @asbradbury on Twitter.

News and articles from around the web

A couple more videos from the 2020 LLVM Developers' Meeting were added to the YouTube channel.

On the mailing lists

• Mike Edwards provided an update on the transition to the 'main' branch, linking to the LLVM Foundation page on the transition.

• There's been substantial new discussion on the RFC about SVec<T> and Vec<T> convenience wrappers. Chris Lattner summarises the parallel discussions taking place in this thread.

• Tom Stellard explained how to disable GitHub Action notifications, noting people may be getting notifications due to an action being introduced to help with the transition to the 'main' branch name.

• Nikita Popov proposes changing the LLVM coding style for argument alignment.

• Rong Xu posted an RFC on adding a 'hot' function attribute to LLVM IR in addition to the currently supported 'cold' attribute.

• Armand Behroozi is seeking guidance on using LLVM to collect dynamic spill and instruction counts from LLVM. Quentin Colombet suggests combining PGO data with emitted assembly annotations.

• Min-Yih Hsu reports that the M68k patches are almost ready to land, and is seeking additional help in reviewing and approving this patches.

• ORC JIT Weekly #27 is out, giving an update on the status of the ORC runtime.

LLVM commits

• Initial infrastructure for code generation of the RISC-V V extension was committed. 5baef63.

• Documentation was added for the AMDGPU object V4 ABI. 04424c6.

• A new attribute, llvm.loop.vectorize.scalable.enable was added. 71bd59f.

• Prologue/epilogue sequences are better optimised for VE. 686988a, 6834b3d.

• A pseudo probe implementation pass was introduced, as part of the ongoing context-sensitive sample PGO work. 64fa8cc.

• The MemCpyOptimizer was ported to MemorySSA. 624af93.

• Epilogue vectorization was added to the loop vectorizer. a7e2c26.

• Support was added for the experimental RISC-V half precision floating-point extension (Zfh). f7bc7c2.

• The 'code' type was removed from TableGen. 415fab6.

• The BPF backend gained support for atomics. 286daaf.

• An arm64e AArch64 sub-arch for Pointer Authentication was defined. It defaults to the apple-a12 CPU. f77c948.

• llvm-objdump for RISC-V will now print pc-relative immediates as absolute addresses. ad923ed.

Clang commits

• The new clang-format option PenaltyIndentedWhitespace assigns a penalty to each character of new whitespace indentation, which in practice will alter thresholds for preferring right-indenting multiple lines vs introducing a line-break before the block. 1e4d6d1.

• 'auto' can now be specified as the -fdiagnostic-hotness-threshold. 93dc1b5.

• CUDA overloading resolution was fixed. acb6f80.

• clang-format's handling of C++ concepts was improved. 840e651.

• clang-tidy gained a concurrency-mt-unsafe check that warns about usage of functions known to be thread-unsafe. cac5be4.

Other project commits

• LLVM's libc gained implementations of mktime, strncpy, and hypot. 6f0f844, 60cef89, 3b487d5.

• A C++2b status page was added to libcxx. 590bbfe.