LLVM Weekly - #446, July 18th 2022

Welcome to the four hundred and forty-sixth 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 [email protected], or @llvmweekly or @asbradbury on Twitter.

News and articles from around the web

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Another talk from EuroLLVM is now available (I believe the final one). Jan Svoboda presents “Implicitly discovered, explicitly built Clang modules”.

On the forums

• As a reminder, LLVM 15.x will branch on July 26th.

• The first meeting about creating an MLIR based Clang IR will take place on Friday July 22nd.

• Stella Laurenzo provided detailed notes on the recent MLIR C/Python API registration overhaul.

• Jeremy Morse shared an idea for better tracking of source location ordering through LLVM.

• Kazu Hirata proposed deprecating llvm::Optional<X>::hasValue/getValue/getValueOr, instead recommending the use of has_value/value/value_or which matches the std::optional interface.

• Bharathi Seshadri is seeking participation from anyone interested in extending LLVM to support GitBOM (a tool for building “Artifact Dependency Graphs”).

• Tanya Lattner is seeking input from anyone interested in helping to get mentors for an expand LLVM in Outreachy.

• Kito Cheng shared that the RISC-V psABI public review period has now started.

• The July 2022 LLVM Code of Conduct Transparency report has been published.

• Various deprecations / removals are underway in MLIR - the tileAndFuseLinalgOps method, Linalg filter-based patterns, OpaqueElementsAttr (assuming no objections to the RFC), and removing legacy ops from the ‘quant’ dialect.

• Fernando Magno Quintão Pereira shared the publication fo the Jotai collection of executable benchmarks.

• Sheng posted an RFC focused on implementing C++20 P0960R3, for initialising aggregates with a parenthesised list of values.

LLVM commits

• Initial support was added for converting function returns with jumps to an architecture-specific symbol on X86 (e.g. __x86_return_thunk). This can be used to mitigate RetBleed. 2240d72.

• Initial support for COFF was added to JITLink. db995d7.

• LoongArch codegen functionality was further expanded, with support for FP conversions and atomics. 1df96ce, e147a0f, 47f3dc6.

• Support for float binop constant expressions was removed. 4bb7b6f.

• Instruction predicate verification was moved so it triggers for both assembly and object emission (rather than just object emission). 3e0bf1c.

• A RISC-V specific CodeGenPrepare pass was added, looking for opportunities for replacing zero-extension with sign-extension on RV64. 1a8468b.

Clang commits

• Documentation is now available for the git-clang-format. 422e6e7.

• Support was added for -mstack-protector-guard-symbol on X86. a45dd3d.

• A MacroUnexpander was added to clang-format. d6d0dc1.

• Clang’s dataflow analysis gained more readable pretty-printing. c9666d2, b8d83e80.

Other project commits

• A GDB plugin was written that uses libompd to provide debugging support for OpenMP programs. 51d3f42.

• MLIR’s C/Python registration APIs were overhauled. 5e83a5b.

• The Flang intrinsic types were documented. 9d24eba.

• pthread_equal and pthread_self were implemented in LLVM’s libc. 8dc4280.

• std::ranges::{set_union,find_end,search,set_symmetric_difference} were implemented. 101d1e9, a5c0638, 3151b95.