LLVM Weekly - #352, September 28th 2020

Welcome to the three hundred and fifty-second 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

Registration closes for the Virtual LLVM Developers' Meeting on October 1st.

Marek Polacek wrote up a summary of new C++ features in GCC 10.

On the mailing lists

• Min-Yih Hsu proposed a Motorola 68000 backend for inclusion in LLVM.

• Fatih Bakir proposed a basic block cloning enhancement for the Propeller link time function layout optimisations.

• Alan Phipps started a discussion about improving jump-threading optimisation in LLVM to help with e.g. CoreMark core_state_transition. Sjoerd Meijer mentioned some in-progress work related to this.

• LLVM 11.0.0-rc3 is now available.

• Anton Zabaznov wrote an RFC on OpenCL C 3.0 support in Clang.

LLVM commits

• A TableGen Backend Developer's Guide was added. 848d66f.

• A scheduling model was added for the Cortex-A55. 4b8ade8.

• DeadInstEliminationPass was removed. DeadCodeEliminationPass should be used instead. f4f7df0.

• ThinLTO will now sort modules in order of largest first, allowing better multi-thread load balancing and faster builds. 6537004.

• LLVM's JSON library gained support for tracking position within an object and reporting errors. 16619e7, fa69b60.

• Codegen support was added for AArch64 PAC/BTI (Pointer Authentication Code / Branch Target Identification). a88c722.

• Scheduler definitions were added for the RISC-V Bullet microarchitecture. 764c1b7.

Clang commits

• A new cppcoreguidelines-prefer-member-initializer check was added to identify member initialisations in the constructor body that can be placed in the initialisation list instead. 4fc0214.

• Sema support was added for a new __swift_name__, __swift_newtype__, and __swift_private__ attributes. 9bb5ecf, 296d883, 58cdbf5.

• A new alpha.webkit.UncountedLocalVarsChecker was added. This check aims to ensure any uncounted local variable is backed by a ref-counted object with sufficient lifetime. 8a64689.

• String tables are now used for static diagnostic descriptions, removing about 120KB of relocations in Clang. 31a3c5f.

• Support was added for a new function coverage groups XRay mode. 6f7fbdd.

• clang-format gained a MacroExpander capable of expanding simple non-recursive macro definitions. e336b74.

Other project commits

• A "trace" plugin was added to LLDB, providing the starting point for process trace support. 74c9395.

• The Mach-O LLD linker implemented support for PIC and absolute symbols. e4e673e, 62a3f0c.

• MLIR now has a new kind of pass - a dynamic pass pipeline. 385c3f4.

• libcxx gained more constexpr containers (C++20 P0784). 0724f8b.

• libcxx gained initial pre-commit CI infrastructure using BuildKite. 9f21d34.