LLVM Weekly - #320, Feb 17th 2020

Welcome to the three hundred and twentieth 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 10.0.0 RC2 has been tagged.

Don't forget to register for EuroLLVM'20. The early brid rate will end on Feb 28th.

Trip reports are now being posted from the Prague ISO C++ meeting. See the /r/cpp trip report and Herb Sutter's. Technical work on C++20 was finished at this meeting, and a schedule and set of priorities for C++23 were agreed.

On the mailing lists

• Tanya Lattner notes that the LLVM Code of Conduct has been in draft for several years now, and outlines the steps and feedback needed to adopt it. She requests that feedback be given within the next two weeks.

• Raphael Isemann proposed that the llgo Go frontend implementation be removed from LLVM. Respondents, including its original author agreed and it has now been removed.

• Vinay Madhusudan started a discussion about the design of the OpenMP dialect in MLIR. The post helpfully starts by summarising the state of various efforts related to this.

• Nico Weber suggests it may be time to move the AVR backend out of experimental.

• The 5th installment of the ORC JIT Weekly is out. Discussion of the new JIT initializer system continues in D74300.

• Reid Kleckner proposes storing basic block order in llvm::Instruction for faster local dominance. All respondents so far are in favour.

• Simon Moll kicked off an RFC thread on adding optional named parameter tuples for intrinsics.

• Simon Cook proposes extending TableGen's AssemblerPredictes to support combining feature with ORs.

• The thread on representations for loop transformations generated much more discussion. See e.g. Chris Lattner's latest comments.

• Stephan T. Lavavej shares that the list of libcxx test suite tests skipped in MSVC's STL testing environment is now available.

LLVM commits

• A document including a proposal and roadmap towards vector predication in LLVM was committed. c49b9e0.

• A first version of MemorySSA-based dead store elimination (DSE) was implemented. d0c4d4f.

• The update_test_check scripts were updated to allow arguments to be specified within the file, and to allow processing to be turned on/off for parts of the file. 1698cc7.

• An initial MASM parser was committed. ee2c0f7.

• Documentation was added on git bisecting across the MLIR merge. 45c6c82.

• LLVM's libraries were updated to use C++14-style return type deduction. fb45968.

• Support for -msave-restore was added to the RISC-V backend. This uses libcalls to implement common save/restore sequences in function prologues and epilogues, reducing code size. 07f7c00.

• A new DWARF transformer class was added to convert DWARF to GSYM. 19602b7.

• The responsibility for fixing issues in experimental targets was clarified in the developers' policy. 4e1c49c.

• TableGen now allows register class weighting to be overridden. 922197d.

Clang commits

• clang-tidy gained a new misc-no-recursion check that flags when recursion is used. 49bffa5.

• The outdated document comparing Clang with other compilers was removed. 42ca012.

• Clang gained an -fignore-exceptions flag. 55e2678.

• Papers from the Prague 2020 C++ workgroup meeting were added to the Clan status page. b74a381.

Other project commits

• llgo was deleted. 372bfc6.

• A new utility was added to the libcxx directory to generate and display a header dependency graph. 99382e4.

• The SharingPtr class used in LLDB was removed in favour of a regular std::shared_ptr. 363f05b.

• LLVM's OpenMP library now builds in C++14 mode by default. 3ff4e2e.