LLVM Weekly - #174, May 1st 2017

Welcome to the one hundred and seventy-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

Tanya Lattner is looking for volunteers to help with system administration, documentation generation and maintenance, and bugzilla and software management.

On the mailing lists

• James Molloy has written up an incredibly helpful description of GVNSink, complete with neat ASCII art diagrams.

• Peter Collingbourne has written an RFC on moving the module summary into the irsymtab.

• Tom Stellard has summarised the outstanding merge requests for 4.0.1-rc1.

• David Gwyne is looking for feedback on his efforts to support the -msave-args command line option on x86-64.

• Daniel Berlin reports the old SimplifyInstruction API is about to be removed and documents how to update any out-of-tree code.

LLVM commits

• A new, simpler loop unswitching pass has been introduced. r301576.

• The scalar evolution verifier should no longer suffers from false positives, though is not yet enabled by default for EXPENSIVE_CHECKS builds pending investigation of a failure triggered in the Hexagon tests. r301146.

• llvm-xray gained a new graph-diff tool for comparing function graphs produced by llvm-xray graph. r301160.

• Size and alignment information of register classes has moved to TargetRegisterInfo. r301221.

• The newly added 'speculatable' function attribute indicates a function has no side-effects beyond computing its result and has no undefined behaviour. r301680.

Clang commits

• Initial code generation for OpenMP's 'distribute parallel for' was added. r301223.

• More unnecessary UBSan checks have been removed. This time, alignment checks on allocas with known alignment. r301377.

Other project commits

• LLD implemented the --defsym command-line option. r301391.

• Linking when using LLD's -Map option has been sped up significantly. The overhead of this option is now about 3x less than before, based on a benchmark of linking clang. r301659.

• Initial APIs for tracing have been added to LLDB. r301389.