LLVM Weekly - #382, April 26th 2021

Welcome to the three hundred and eighty-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

Josh Haberman blogged about making use of the new musttail attribute in Clang for protobuf parsing.

On the mailing lists

• Christian Kühnel queries whether anyone is doing code review on the mailing lists any more, triggering a discussion about whether reviews by email should be phased out. Philip Reames pointed out that the commit lists do have email responses that don’t make it to Phabricator or post-commit email discussions.

• David Blaikie started a discussion on refining the definition of optnone with interprocedural transformations. A number of respondents were in favour of adding a ‘noipa’ attribute. Paul Robinson wrote up a proposal on optnone, following extensive discussion.

• Michał Górny posted an RFC thread on improving protocol-level compatibility between LLDB and GDB.

• Paul C. Anagnostopoulos is seeking feedback on the return value of the !find TableGen operator when there is no match.

• Tobias Hieta sought feedback on proposals to better automate LLVM releases.

• The discussion about emitting unaligned vector moves continued with Paul Robinson pointing out that the previous behaviour is needed in some cases for backwards compatibility.

• Arthur Eubanks split off a thread to discuss deprecation of the old pass manager.

LLVM commits

• The M68k disassembler was committed. 2221185.

• The CSKY backend gained an assembly parser and support for basic instructions. 8ba622b, 4216389, 4bb60c2.

• TableGen now supports the assert statement in multiclasses. a5aaec8.

• A new peephole optimisation was added to the AArch64 backend to remove redundant cmp after cset. 2ec1610.

• An implementation of MacOS’s ‘otool’ was added. 1a3f886.

• Documentation was added on LLVM’s CI system. 7f9717b.

• The memcpy optimiser was updated to work for variable sizes, as long as the sizes in the memcpy-memcpy or memcpy-memset pairs are equal. f5446b7.

• IR intrinsics were added for the RISC-V Zbp extension. b49337b.

• The X86 backend gained support for AMX fast register allocation. 3b8ec86.

Clang commits

• The new amdgpu-arch tool can list all AMD GPUs installed. 15be0c4.

• clang-scan-deps gained support for clang-cl. 8c16c8b.

• Collecting a profile without a filesystem is now documented. d4ee603.

• The clang_builtin_alias attribute was introduced, allowing an alias to be introduced for a Clang builtin. 1088643.

Other project commits

• A Language Server Protocol implementation and vscode language extension was added for MLIR. 751c14f, b810e3a, 52fad38.

• A status page was added for libcxx’s Format library. ca177dc.

• Initial ORC runtime directories and build system files were added to compiler-rt. 5e537ea.

• Platform-specific implementations of fma and fmaf were added to LLVM’s libc. 95934c3.