LLVM Weekly - #332, May 11th 2020

Welcome to the three hundred and thirty-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

Nikita Popov has written a detailed blog post on making LLVM fast again, detailing a series of work that improved compile times by ~10%.

The accepted Google Summer of Code projects with the LLVM Foundation have been announced. Congratulations to those who were accepted.

On the mailing lists

• On behalf of the LLVM Foundation board, Tanya Lattner announced that the 2020 LLVM Dev Meeting will be held virtually. Potential participants are encouraged to fill out the attached survey. "We realize that this may be a disappointment to many in our community and honestly, we feel the same way. We strongly believe that the most valuable part of our conferences is the in person 'hallway' discussions, round tables, networking, and socialization. An LLVM Developers’ Meeting might be one of the few times you see your LLVM Project co-workers in person. While a virtual event will not be the same, we do hope to make it as great as we can and to bring our community together to share each other's successes, ideas, and advice."

• Christian Kühnel provided an update on pre-merge testing. Amongst other improvements, Windows builds and tests are now enabled for all users. The plan is to next move to using BuildKite rather than a private Jenkins instance.

• Kai Wang shared an RFC on RISC-V vector intrinsics.

• ORC JIT Weekly #15 is out, giving an update on safe code removal. Lang also notes he intends to move status updates to Friday going forwards.

• Alex Renda had a question about the behaviour of llvm-mca on instructions with ProcResGroups which attracted detailed responses.

• Emre Kultursay queries if anyone has explored a 'just-my-code debugging mode' for LLDB.

• Amy Huang wrote an RFC on adding constructor homing to clang's limited debug info mode. As outlined in the post, this reduces object file size in debug builds by 30-50%.

• JF Bastien proposed adding volatile overloads of memcpy/memmove/memset builtins.

LLVM commits

• dsymutil gained a new option to print statistics about the .debug_info size. 7fb9bcd.

• Known bits constant folding in InstSimplify was removed on the basis that the calculation is expensive but very rarely helps codegen. 5a22656.

• More descriptive names are now used for machine basic block sections. c8ac29a.

• LLD's parallel algorithm wrappers were moved up into llvm/Support/Parallel.h. 932f027.

Clang commits

• Support for _ExtInt was enabled for all in-tree targets. 8a1c999.

• Support was added for #pragma float_control, allowing floating-point semantics and exception behaviour to be specified for a section of source code. f5360d4.

• Support for many additional SVE2 builtins was added. 086722c, e46043b, and many more.

Other project commits

• Complex numbers, complex addition, and complex subtraction were added to the standard MLIR dialect. 031265a, 5d5f61f.

• LLD's Mach-O linker now supports calls to functions in dylibs. b3e2fc9.

• LLD now enforces -- prefixes for options not supported by GNU ld (where -option doesn't need to be supported for compatibility). e20a215.

• MLIR now supports merging identical blocks during canonicalisation. 469c02d.