LLVM Weekly - #291, July 29th 2019

Welcome to the two hundred and ninety-first 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

Botond Ballo has written up a trip report from the Cologne C++ standards meeting. You might also be interested in the results of Herb Sutter's survey to find the top five ISO C++ feature proposals.

On the mailing lists

• The discussion on changing variable naming rules in LLVM spawned a sub-thread on the interaction with git blame, with Chris Lattner giving further insight into why he now prefers a sweeping change and his concerns about avoiding codebase improvements due to concerns about history.

• Andrew Wei has been adding GlobalISel support to the RISC-V backend and iss seeking feedback.

• Hans Wennborg reports that 9.0.0-rc1 is coming a little bit later than expected, but should appear soon.

• Paul Kirth proposes a new clang-mispredict tool that would identify and warn on potentially incorrect uses of __builtin_expect(). The tool would be built on top of the PGO infrastructure.

• Jon Korous shares an RFC on adding frontend insight remarks to Clang, e.g. to explicitly indicate when implict constructors are generated.

LLVM commits

• Arm MVE codegen support continues, with the addition of MVE predicate register support. r366890.

• LLVM's documentation gained definitions of commonly used terminology related to loops. r366960.

• SanitizerCoverage has been ported to the new pass manager (the patch re-landed). r367053.

• The Attributor can now deduce the "dereferenceable" attribute. r366788.

• TargetLowering gained a SimplifyMultipleUseDemandedBits function, which can peek through operations that contribute to the demanded bits of a node. r366799.

• The PowerPC backend now has a new peephole to remove redundant load immediate instructions. r366840.

• Basic definitions were added for the Cortex-A64, Cortex-A65AE, Neoverse E1 and Neoverse N1. r367007.

Clang commits

• Clang now implements P1771, [[nodiscard]] for constructors. r367027.

• firstprivate OpenMP variables are now supported. r366689.

Other project commits

• LLVM's OpenMP implementation now has RISCV64 support. r367021.

• The libc++ std::vector implementation was updated to workaround suboptimal codegen for vector<unsigned char>. r367183.

• The libc++ c++2a status page was updated. r366696.

• TableGen is now used to generate LLDB property definitions. r367058.