LLVM Weekly - #296, September 2nd 2019

Welcome to the two hundred and ninety-sixth 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 LLVM 9.0.0 release candidate 3 is available.

On the mailing lists

• Tom Stellard has posted instructions for requesting GitHub commit access. If you currently have SVN commit access, you are requested to add your information to the github-usernames.txt file prior to SVN becoming read-only on October 21st.

• Philipp Reames has proposed changes to atomic load/store in SelectionDAG. Atomic loads and stores will be treated as normal LoadSDNode or StoreSDNodes, but this change will be enabled on a per-backend basis.

• Sam Elliott posted an RFC on adding the GCC C Torture Suite to the external LLVM test suites. As Sam notes, we've found the torture execution tests incredibly useful in backend development. Sam has an initial patch for review.

• Reshabh Sharma provided a summary of his GSoC work to support 64-bit pointers in the RISC-V 32-bit backend.

• Seiya Nuta posted a final report on their GSoC project to improve LLVM binary utilities like llvm-objcopy, llvm-objdump.

• Csaba Dabis has posted a final report for their GSoC project to apply the Clang Static Analyzer to LLVM.

• Vic (Chun-Ju) Yang suggests moving the RELRO segment to immediate alfter the read-only segment. While Rui Ueyama was in favour, David Chisnall raised some concerns.

• Graham Hunter started a discussion on codegen for a scalable vector splat. Renato Golin recapped the main argument about the trade-offs of introducing new constructs / node types.

LLVM commits

• The LoopIdiomRecognize pass can now recognise a BCmp loop. r370454.

• llvm-ifs, an LLVM Interface Stubs merging and object file generation tool was committed. r370499.

• A new shouldExtendTypeInLibCall hook was added and used to ensure libcall lowering on RV64 properly respects the ABI r370275.

• The GlobalISel importer learned to handled patterns containing INSERT_SUBREG and SUBREG_TO_REG r369973, r370254.

• Scalable vectors are now supported in intrinsics. r370053.

• The return values of allocation functions are now annotated with dereferenceable_or_null. r370168.

• Arm MTE support was updated with an optimisation for unchecked load/stores of stack offsets. r370490.

Clang commits

• Clang will now warn when it is about to exhaust the stack and can allocate a new stack by spawning a new thread. This improves the user experience when dealing with e.g. heavily recursive template instantiations. r369940.

• The clang-tidy-vs Visual Studio plugin was removed. Users are encouraged to use Clang Power Tools instead. r370096.

• The new -gen-cdb-fragment-path option can be used to emit a fragment of a compilation database for each compilation. r369938.

• MaxAtomicInlineWidth and MaxAtomicPromoteWidth are now set appropriately for RISC-V targets. r370073.

• Semantic restrictions were implemented for C++20 designated initializers. r370544.

Other project commits

• std::vector in libcxx will now unconditionally move elements when exceptions are disabled. r370502.

• LLDB's dotest.py saw lots of refactoring and updates. r370234, r370259, and more.