LLVM Weekly - #311, December 16th 2019

Welcome to the three hundred and eleventh 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

All videos from the 2019 LLVM Developers' Meeting are now posted and available in a handy YouTube playlist.

LLVM 9.0.1-rc3 has been tagged.

On the mailing lists

• Teresa Johnson shared an RFC on supporting agressive whole program devirtualization without -fvsibility=hidden.

• Jonas Devlieghere wrote up an RFC on supporting Lua scripting in LLDB.

• Sam McCall starts a discussion on providing network RPC in LLVM projects, and is seeking feedback on depending on external libraries like Thrift, grpc etc.

• Sander De Smalen shares notes from last week's SVE sync-up call and the agenda for the next one.

• Raphael Isemann shared a summary detailing the future of modern-type-lookup in LLDB. "modern-type-lookup is a flag that makes LLDB use clang::ExternalASTMerger instead of directly using the clang::ASTImporter via our ClangASTImporter wrapper."

LLVM commits

• Initial matrix intrinsics and a lowering pass were added. 526244b.

• Initial work related to profile guided size opimization was committed. This adds instrumentation, but doesn't yet enable size optimisation. d9ae493.

• Support for a Vector Function Database was merged. 0be8196.

• The Arm cost model now understands cases where a shift can be folded into other instructions. be7a107.

• New tests were added for resolving of RISC-V relocations. 707e970.

• Dead loop update instructions are now removed from Arm low overhead loops. d97cf1f.

• getIntImmCost was renamed to getIntImmCostInst and getIntImmCostIntrin. 85ba5f6.

• Target-specific intrinsic enums were split into separate headers. This saves 222MB of object file size in a Windows optimised+debug build. 5d98695.

Clang commits

• A new TableGen backend was added for generating serialisation classes. 6404bd2, d505e57..

• Clang support was added for constrained FP builtins. 6515c52.

• Clang now defaults to -fuse-init-array, using -fno-use-init-array only for platforms known not to support .init_array. b2b5cac.

• Clang learned to synthesise defaulted comparison functions for C++20. cafc741.

Other project commits

• A new script was added for symbolising hwasan reports after the fact. 9ef451d.

• Fuzzing was added for parts of <random> in libcxx. daacf57.