LLVM Weekly - #537, April 15th 2024

[asb]

LLVM Weekly - #537, April 15th 2024

If you prefer, you can read the canonical version of this issue at http://llvmweekly.org/issue/537.

Welcome to the five hundred and thirty-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, @llvmweekly or @asbradbury on Twitter, or @llvmweekly@fosstodon.org or @asb@fosstodon.org.

News and articles from around the web and events

No articles to highlight this week - tips always welcome.

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

• Office hours with the following hosts: Phoebe Wang, Johannes Doerfert, Aaron Ballman.
• Online sync-ups on the following topics: Flang, pointer authentication, SYCL, libc++, LLVM security group, new contributors, LLVM/offload, classic flang, Clang C/C++ language working group, loop optimisations, floating point, OpenMP in Flang, MLIR open meeting.
• For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.

On the forums

• Renato Golin is curious about interest in organising LLVM conferences in other regions, e.g. Asia, South America, Africa.

• Vy Nguyen shared an updated design proposal for LLDB telemetry/metrics.

• Tom Stellard shared a PSA on a reported suspicious login for llvmbot and the actions taken.

• Nick Desaulniers shared that he’s drafted a policy for hand-written assembly in libc

• Matthias Gehre posted an RFC on adding arithmetic, logical and comparison expressions in MLIR’s PDLL.

• Vitaly Buka is seeking to introduce a new clang builtin __builtin_allow_runtime_check which is intended to be used to guard expensive runtime checks.

• Kristof Beyls shared the slides of his keynote on a BOLT-based binary analysis tool.

• The 64th edition of MLIR News is now available.

• Guillaume Chatelet posted notes from the LLVM libc round table at EuroLLVM.

• Justin Bogner kicked off an RFC thread on adding a bunch of additional LLVM intrinsics for math operations present in C++ or HLSL.

• Andy Kaylor proposed modifications to the LLVM language reference to describe the allowed impact on fast math flags of transformations.

LLVM commits

• Initial support was added to the superword-level parallelism vectorizer for vectorization of non–power-of-2 ops. 6d66db3.

• uitofp now supports the nneg flag. 9170e38.

• An ExecutionSession state verified was added to ORC, enabled under EXPENSIVE_CHECKS builds. 649523f.

• ExpandLargeFpConvert gained support for bfloat types. 110c22f.

• Statepoint and patchpoint support was added for RISC-V. 53003e3.

Clang commits

• The _cpp_concepts macro is now set to 202002L which enables <expected> from libstdc++ to work correctly with Clang. 2875e24.

• Work started on implementing vector types in the clang interpreter. b7a93bc.

• The syntax difference between HIP and CUDA is now documented. 2bf4889.

• The CLANG_ENABLE_CIR CMake variable was added in preparation for allowing the building of Clang with ClangIR. 44de2bb.

• The ‘if’ clause was implemented for OpenACC compute constructs. daa8836.

Other project commits

• A design document for debug info generation in Flang was committed. 357f6c7.

• The scudo secure memory allocator now has an EnableContiguousRegions mode. bab0507.

• The libclc build system was refactored to allow in-tree builds. 72f9881.

• libcxx format was updated to Unicode 15.1. 59e66c5.

• The AMDGPU shared memory optimisation pass was removed from MLIR due to a range of issues. 4471831.

[rengolin]

Multiple round table notes from EuroLLVM have started to appear:

Community.o Workshop @ EuroLLVM 2024

This thread is an umbrella for the community.o workshop event at EuroLLVM 2024, similar in spirit to the one from the US dev meeting this fall. Copying @cishida 's guidance from the last event, please include in your post: The areas of improvement your group discussed Tasks and ideas to combat these problem areas How to measure or observe the impact of these tasks If applicable, please post action items on Issues · llvm/Community.o · GitHub

Notes from the LLVM libc round table @ EuroLLVM 2024

Attendance : Google, ARM, Fuchsia, mostly from the embedded word + a few desktop people as well For those present at the round table, feel free to add more questions or amend the notes as I’m not sure I covered it all. Questions & Answers How to package LLVM libc? Especially, how to release multilib for our IDEs? We don’t release packages as part of LLVM because the library is still incomplete. That would be up to a vendor to do the release (at least for now) How do we ensure conformance?…

Notes from the Embedded Systems round table @ Euro LLVM 2024

My notes from memory, please feel free to add anything important I’ve missed out in the thread. Configuration file based multilib General consensus that adding a way for the multilib configuration file to supply its own strings to select on was a reasonable idea. Please send RFC/pull-request. Alternative of selecting based on macro definitions on the command-line -D was considered an interesting idea, but too likely for names to clash accidentally, particulary if regular expressions were invo…

Notes from the MLIR Upstream Round Table @ EuroLLVM 2024

The two main topics that were discussed at the round table were cost models / target descriptors and named operations in Linalg. We ran out of time (1h) so had to stop. The examples below are not meant to be accurate, and it’s just an idea of what the design is. The actual implementation may end up very different and will be discussed in the respective PRs. Cost model / Target Descriptor Reasonable consensus that we need a generic way to represent multiple targets in MLIR and that cost models…

[daphnediane]

Is the link for BOLT supposed to be: [RFC] BOLT-based binary analysis tool to verify correctness of security hardening - #8 by kbeyls currently it points to runtime_check from the post above.

[asb]

Thank you, now fixed.