LLVM Weekly - #386, May 24th 2021

Welcome to the three hundred and eighty-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 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

Francesco Bertolaccini created ClangQL, a proof-of-concept SQLite extension for querying C++ codebases that have been indexed using clangd.

Nelson Hage blogged about using AWS Lambda to build LLVM in 90 seconds.

Pekka Jääskeläinen announced the release of PoCL v1.7, a portable open source implementation of OpenCL. This release features support for Clang/LLVM 12.0 and has improved support for cross-compiling and SPIR-V binaries when using CPU devices.

On the mailing lists

• Tanya Latter is seeking input to inform planning of the 2021 LLVM Developers' Meeting, sharing a survey for input.

• Krzysztof Parzyszek postd an RFC on deprecating pre-commit email code reviews in favour of Phabricator. This limits the scope of a similar RFC that preceded it, with the goal of getting full consensus. There are no major objections so far.

• The list of accepted LLVM GSoC projects is now available. Congratulations! A number of the accepted students have been posting details of their projects (apologies if I’ve missed your mailing list message!):

  • Ajay Arasanipalai - Modernising the ‘building a JIT’ tutorial
  • Liqiang Tao - Locally optimal inlining decisions
  • Tarindu Jayatilaka - Optimising LLVM’s pass pipeline using machine learning
  • Pratyush Das - Integrating custom derivatives of numerical computing routines into Enzyme
  • Toshiki Maekawa - Utilise LoopNest pass
  • Hyeongyu Kim - Fix miscompilation issues in LLVM IR using the ‘freeze’ instructions
  • Deep Majumder - Making smart spointer checkers default checkers in the static analyzer
  • Manas - Constraint solver improvements for the Clang static analyzer
  • Omar Emara - Evolving the LLDB GUI.

• LLVM GPU News Issue #12 is out with a range of GPU-related LLVM development highlights.

• Sam Powell posted an RFC proposing a new llvm-tapi-diff tool.

LLVM commits

• AArch64 and X86 gained support for a newly added ‘swifttailcc’ calling convention. 82a0e80.

• Loads and stores, GEPs, cmpxchg, and atomicrmw all now work with opaque pointers. 6013d84, 28b9771, 1b25fce. 0bebda1.

• The loop idiom recognizer can now spot the ‘shift until zero’ idiom. 0633d5c.

• C bindings were added for the new pass manager. 0c557db.

• Initial work was committed for flow-sensitive SampleFDO. 886629a.

• A new hook was added and used in CodeGenPrepare to convert comparison of branches to prefer icmp eq zero if possible. dd5c520.

Clang commits

• Support was added for MSVC’s -EHa exception handling. 797ad70.

• -Wunused-but-set-parameter and -Wunused-but-set-variable warnings were introduced. 14dfb38. REVERTED

• The -fextend-arguments command line option was introduced to specify widening of integer arguments of unprototyped function calls. d30dfa8.

Other project commits

• MATMUL, PACK, SPREAD, TRANSPOSE, and more were implemented in the flang runtime. 5e1421b, c1db35f.

• The MLIR pass management infrastructure gained support for a -print-ir-after-failure flag. 64ce90e.