LLVM Weekly - #307, November 18th 2019

Welcome to the three hundred and 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 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

The next Toronto LLVM/Clang social meetup will take place on Tuesday November 26th and include a presentation on writing loop optimisations in LLVM.

The next HelloLLVM/HelloGCC social in Shanghai will take place on Nov 23rd.

Videos from the 2019 LLVM Dev Meeting have started to appear on the LLVM YouTube channel.

On the mailing lists

• Tom Stellard posted an RFC on using GitHub Actions for CI testing on the release branches.

• JF Bastien and the Apple LLVM team proposed a new security process and associated private LLVM Security Group.

• Andrzej Warzynski announced llvm-tutor, a collection of out-of-tree passes, plugins, and tools for LLVM aiming to make it easier for those looking to use LLVM for their own out-of-tree projects.

• Tom Stellard has posted the proposed 9.0.1 release schedule.

• Hal Finkel is working on a patch to better document LLVM's code review process and seeking input.

• David Rector shared a Clang 7.0 fork allowing reflection on the Clang AST. This thread triggered discussion on the stability of the Clang AST interface and on the ongoing C++ reflection standards work.

• Johannes Doerfert suggested two changes to the proposed restrict support.

• Mehdi Amini is seeking feedback on how to integrate MLIR into the monorepo. He is proposing to perform a git subtree merge, which would preserve MLIR history.

• Johannes Doerfert proposes creating llvm/lib/Frontend for code that can be shared between frontends (e.g. clang and flang). This would initially be populated with the OpenMP-IR-Builder.

• Andrew Kaylor is seeking feedback on his use of token arguments and operand bundles for constrained FP intrinsics.

LLVM commits

• An IRTransformations directory was added to the LLVM examples, to contains example transformation/analysis code used by tutorials. 7d0b1d7.

• LLVM's SHA1 implementation was optimised, resulting in a 10% improvement of linking time for LLD. 43ff634.

• The AArch64 backend can now spill/fill callee-saved SVE registers. 84a0c8e.

• InitializePasses.h includes were sunk in order to reduce the number of recompiles needed when it's modified. 05da2fe.

• More work has been done on MIPS GlobalISel, with support for selecting addiu, andri, ori, xori. dda8e95, 1f55935.

• The RISC-V backend can now handle variable sized objects on the stack in the case that the stack must be realigned. cf6cf0c.

Clang commits

• -Wtautological-compare was added to -Wall. 9740f9f.

• The -march and -mabi selection logic for RISC-V in the Clang driver was updated to more closely mirror GCC defaults. e3d5ff5.

• Clang gained intrinsics for Arm MVE contiguous load/stores, vector get/set lane, and more. a12f588, 9e37892.

Other project commits

• The imported GCC C Torture Suite was enabled for Mips. 45c8b76.

• The libcxx status page was updated with new papers from the Belfast C++ standards meting. 2f4fb20.