LLVM Weekly - #324, Mar 16th 2020

Welcome to the three hundred and twenty-fourth 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

John Regehr and Nuno Lopes have written a blog post on Alive 2. It will take an unoptimised function in LLVM IR and either proves that it is refined by the optimized version of the function, or else shows a set of inputs that illustrate a failure of refinement.

EuroLLVM'20 has now been cancelled due to COVID-19.

LLVM 10.0.0-rc4 has now been tagged.

On the mailing lists

• Richard Barton reports that merging f18 in LLVM as flang has been delayed until Mon 23rd March.

• ORC JIT Weekly #8 is out. Basic OrcV2 C Bindings have been added, and a number of MachO and COFF bugs fixed.

• Scott Constable and Zola Bridges wrote separately about load value injection mitigation for x86.

• Nigel Perks sent an update on plans from XMOS for the XCore target.

• Chris Tetreault wrote an RFC on refactoring the class hierarchy of VectorType in the IR.

• Farzad Sadeghi announced cgrep, a grep-like tool for C language source files.

LLVM commits

• The AVR backend was promoted to a standard backend, built by default. dfecec6.

• Macro fusion was implemented for the PowerPC backend. 518292d.

• The attributor framework was extended to introduce propagation of known information based on path exploration. bdcbdb4.

• CPU definitions were added for the Fujitsu A64FX. c8cd1a9.

• IEEEFloat::roundToIntegral was made more standard conformant. 14a1b80.

• Support was added for placing every basic block in a unique ELF text section, allowing the linker to order them in an arbitrary sequence. 4dfe92e.

• AssemblerPredicates can now be combined with ORs. a26bd4e.

Clang commits

• Clang will now default to -fno-common for all targets, matching the GCC 10 default. 2c36c23.

• Clang's parsing of GNU C extended asm statement was improved. 246398e.

• clang-tidy gained a new module to enforce standards specific to the llvm-libc project. eb41cc6.

Other project commits

• libc now has a Linux implementation of thrd_create, thrd_join, mtc_lock, and mtx_unlock. fd8c133.

• libunwind performance was improved. 8ffdabd, c53c205.

• PGO is now disabled for compiler-rt, as it doesn't officially support it. 20dfcf1.

• In MLIR, HasNoSideEffect was replaced with MemoryEffectInterface. 0ddba0b.