LLVM Weekly - #302, October 14th 2019

Welcome to the three hundred and second 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 Call for Papers for for the LLVM Dev Room at FOSDEM 2020 is now open. The deadline is the 24th November, and the devroom will take place on Saturday 1st February in Brussels.

The next set of proposed papers for the C++ standard have now been posted.

On the mailing lists

• Tom Stellard shares an update on the GitHub migration schedule and plans. The plan is to make SVN read-only on the evening of October 21st.

• Jeremy Morse proposes that LLVM adopts Sony's Dexter tool and uses it to run debuginfo-tests.

• Tanya Lattner confirms that the LLVM Foundation Board of Directors has voted to accept MLIR as a project into LLVM.

• Sam Elliott reports that the GCC Torture Suite has now been imported into the LLVM test suite.

• Josef Eisl has written a patch to add support for embedding bitcode in a binary during LTO. This follows this earlier RFC. He's actively seeking reviewers.

• David Greene kicked off an RFC thread on end-to-end testing. This generated a lot of discussion that sadly I can't fully summarise.

• Galina Kistanova has sent out a note to buildbot owners to prepare their bot for the git switchover.

• David Tellenbach submitted a patch to enable scheduling of CFI instructions to try to address the issue where generated assembly differs depending on whether debug info is generated, but notes this approach seems to be a dead-end. He will next try to post-pone insertion of CFI instructions to after machine scheduling.

• Serge Guelton is seeking input on stack clash protection for X86 in LLVM.

• The LLVM Dev Meeting is taking place next week and Tanya Lattner is seeking volunteer moderators.

• Siva Chandra has posted the first RFC on the libc-dev mailing list, proposing "ground truth" description files for the public API.

LLVM commits

• A new pass adds support for elimination of dead virtual functions during LTO.r374539.

• Support for SVE in LLVM IR continues with the addition of scalable vector size queries and IR instruction support. r374042.

• The Attributor can now deduce memory behaviour of functions and arguments. r373965.

• The LLVM docs have seen more re-organisation, with the "subsystem documentation" content moving to the User Guides and Reference pages. r373872.

• Constrained intrinsics were added for lrint and lround. r373900.

• update_test_checks.py not accepts --preserve-names which means IR names aren't replaced. r373912.

• X86 gained a new "tailcc" calling convention that guarantees tail call optimisation. r373976.

• update_cc_test_checks.py can now handle a clang | opt | FileCheck pipeline. r374287.

• FileCheck now supports --ignore-case. r374538.

Clang commits

• The new -fgnuc-version= option allows control of __GNUC__ and other GCC macros. r374449.

• clang-format gained initial support for producing warnings for lines that need reformatting. r374663.

• The Clang interface stubs tooling now has end-to-end support for generating ELF interface stubs. r374061.

• Clang's OpenMP 5.0 implementation was updated with support for the "master taskloop" directive. r374437.

Other project commits

• The GCC C torture suite was imported into the LLVM test-suite. It can be built using CMake and run using Lit. r374155 and r374156.

• LLDB learned to read symbols from .gnu_debugdata if present. r373891.

• LLDB accelerator table lookups were sped up (accelerated!). r374401.