LLVM Weekly - #357, November 2nd 2020

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

News and articles from around the web

Videos from the 2020 LLVM Virtual Developers' Meeting have started to be posted on YouTube.

On the mailing lists

• Geoffrey Martin-Noble proposes contributing Bazel BUILD files for LLVM, suggesting they be maintained with a similar support level to the in-tree gn build system. This triggered a lengthy discussion, which inspired Renato Golin to create a new thread to discuss a more general policy on "support tiers".

• The nineteenth issue of the MLIR newsletter is out now, including info on sparse code generation work, Python bindings, and more.

• Anna Sophia Welker is considering a Master thesis topic related to VPlan and seeking input on goals for VPlan-based cost modelling.

• Mircea Trofin shared an RFC on disallowing unused prefixes in FileCheck.

• Gulfem Savrun Yeniceri suggests adding leaf attribute support to Clang/LLVM, outlining a high level design and sharing an initial patch.

• Reshabh Kumar Sharma shared a proposal to implement the sanitizer runtimes for heterogeneous devices.

• Anton Korebeynikov notes some changes to the Google Summer of Code 2021 program, and asks potential mentors start thinking about potential projects with these changes in mind.

• Nicolai Hähnle restarted discussions on his RFC thread about introducing convergence control bundles and intrinsics.

LLVM commits

• The patches introducing the CfgTraits abstraction were reverted pending more discussion. e025d09.

• A new per-basic-block optimisation remark was added, summarising the count for each machine opcode. b2bec7cec.

• Support was added for POWER10 set boolean condition instructions. 803cc3a.

• Implementation of the VE backend continues with support for many more vector instructions. c5fa6ba, 83cb423, 9d0db40, and many more.

• An AMDGPU late codegen preparation pass was added. 46c3d5c.

• Documentation on special treatment of PHIs in loop analyses was added. a334530.

Clang commits

• Driver commandline remarks options will now be passed to the linker when LTO is enabled, making it easier to collect remarks from both pre-LTO and LTO compilation. c486870.

• [[likely]] and [[unlikely]] attributes can now be used on while and for loops. b46fddf.

• __vector_pair and __vector_quad types were added for PowerPC. 40dd4d5.

• Various changes were made to the FileEntryRef API. 84e8257.

Other project commits

• A libc++ configuration that doesn't support localisation was introduced, meant for e.g. embedded systems. 88ffc72.

• Watchpoint support was enabled for LLDB on FreeBSD. 8e7ea99.

• An mlir-spirv-cpu-runner prototype was added, intended to run a GPU kernel on a CPU via GPU to SPIRV to LLVM conversions. 89808ce.