LLVM Weekly - #334, May 25th 2020

Welcome to the three hundred and thirty-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

LLVM 10.0.1-rc1 has been tagged.

Chris Colman wrote about improving firmware quality using LLVM and Clang.

Djordje Todorovic created a page tracking debug location coverage in optimised LLVM-produced code.

Min-Yih Hsu blogged about using LLVM Lit out-of-tree.

On the mailing lists

• Tom Stellard proposes changes to the LLVM release process, including creating a time-based bug-fix release schedule and eliminating release candidates for bug-fix releases. It also clarifies rules for what kinds of backports are accepted during each release phase.

• Nathan Sidwell shared an implementation of the C++20 module mapper. This was written for GCC, but he shares it under the standard LLVM license.

• Vishal Chebrolu will be working on LLVM under GSoC and shared a proposal for improving MergeFunctions to incorporate MergeSimilarFunction patches and ThinLTO support.

• Xing Guo shared an RFC on adding DWARF support for yaml2obj.

• Fangrui Song proposes an update to the -fuse-ld= semantics, to better specifiy the behaviour for prepending ld. or ld64..

• There was further discussion around refactoring the class hierarchy of VectorType. Eli Friedman's response is perhaps a good starting point.

LLVM commits

• More documentation on using git was added to the getting started guide. b2d733c.

• The Arm LowOverheadLoops pass can now handle VPT (vector predication) blocks. 835251f.

• CodeGen was added for the preallocated IR constructs for X86. 8a88755.

• A CanonicalizeFreezeInLoops pass was added to address a performance degradation. d9a4a24.

• It's now possible to generate reproducers for dsymutil. 92fd397.

• A new isMulhCheaperThanMulshift TargetLowering hook was added. b631f86.

Clang commits

• A new WebkitRefCntblBaseVirtualDtor static analyzer check was implemented, performing analysis of WebKit's reference counted smartpointers. f7c7e8a.

• Support for the nomerge function attribute was added. When added to a statement containing call expressions, those expressions won't be merged during optimisation. e36076ee.

• An addrspace_cast operator was added for OpenCL in C++ mode. a6a237f.

• ABIInfo and TargetCodeGenInfo were implemented for the AIX ABI. 7f5d91d.

Other project commits

• Work to improve LibFuzzer performance by changing how weights are assigned to seeds was committed. e2e38fc.

• LLVM's libc implementation gained memset and bzero. 6ca54e0.

• The LLD Mach-O linker gained support for -order_file and .subsections_via_symbols. 55e9eb4, 4eb6f48.