LLVM Weekly - #408, October 25th 2021

Welcome to the four hundred and eighth 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, or @llvmweekly or @asbradbury on Twitter.

News and articles from around the web

Registration is now open for the 2021 LLVM Developers' Meeting and the schedule has been posted. It will be a 4 day online event, Tuesday 16th November 2021 - Friday 19th November 2021.

Krister Walfridsson blogged about optimisations enabled by -ffast-math.

On the mailing lists

• Ellis Hoag shared an RFC on adding a lightweight variant of IR instrumentation profile-guided optimisation (IRPGO), intended to be suitable for PGO on mobile devices.

• Florian Hahn provided an update on the RFC to add a new set of vector builtins, linking to the current patches under review. He hopes to land them this week.

• Björn Pettersson followed up on a discussion about non-determinism in DominatorTree, JumpThreading, and EarlyCSE with a summary of potential paths forward.

LLVM commits

• ThinLTO’s caching was moved to the LLVM Support library so it can be used elsewhere in LLVM. e678c51.

• An initial draft policy around creating new git repos and granting write access to them was added. dcc91dd.

• A scheduling model was added for Power10. 67c64d8.

• An experimental new option for the new pass manager was added, eagerly-invalidate-analyses. This will decrease maximum memory usage at the cost of higher compile time by eagerly invalidating function analyses. b8ce973.

• llvm-reduce gained reduction passes to reduce operands to undef/1/0. 9660563.

• ASM parser support was committed for the CSKY basic integer instruction set de10a02.

Clang commits

• A number of tests that are tied to the legacy pass manager were removed. cb5a101.

• It’s now possible to run a Clang plugin if specified on the command line before the main action. fe66433.

Other project commits

• A range of utility functions were added to FIRBuilder. f17f694, 45503fc, c983aed, a2e7af7.

• LLVM’s libc gained implementations of atof, strtof, and strtod. 87c0160.

• A short document was started to record deliberate differences between LD64 and lld-macho. 6b715e9.

• A “command container” hierarchy was added to LLDB, enabling users to organise their commands in a hierarchy rather than having to stick to just top-level commands. c5011ae.

• The new “runtimes” build is now the default way of building libc++. 79175f3.

• The unused parallel-libs project was removed. db0486c.