LLVM Weekly - #322, Mar 2nd 2020
Welcome to the three hundred and twenty-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
IBM have announced that their C/C++ and Fortran compilers will be adopting the LLVM open source infrastructure. "IBM intends to fully incorporate the LLVM Core and Clang sub-projects in future C/C++ offerings on z/OS, Linux on Power, and AIX platforms."
Guidance has been issued for EuroLLVM 2020 and Coronavirus (COVID-19).
Alex Denisov released llvm2graphml, a new tool for exploring LLVM bitcode interactively
On the mailing lists
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Shoaib Meenai wrote to announce Facebook's intention to contribute an implementation of LLD for Mach-O.
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Jeremy Morse wrote an RFC on a new way of specifying variable locations for debuginfo post-isel, moving away from the current
DBG_VALUErepresentation. -
Florian Hahn updated the proposal for matrix support in Clang in response to feedback.
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Christian Kühnel reports that pre-merge testing is enabled by default on Phabricator, after 3 months of beta testing.
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Galina Kistanova shared that zorg will be ugrading to a recent buildbot version, and indicated steps for bot owners to take to help with the transition.
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Pierre van Houtryve asked for guidance on how to help improve debug experience for optimised code and received useful responses.
LLVM commits
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The callbr instruction can now return non-void values. 23c2a5c.
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A new CoalescingBitVector datatype was implemented and used to solve a compile-time explosion issue in LiveDebugValues. b0142cd, 210c485, a993720.
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The coverage mapping format was changed to reduce binary size. This shrinks the size of llc's coverage segment by 82%. 9931712.
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Fixed point saturating division intrinsics were added. 6e561d1.
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Infrastructure was added to print and parse MIR MachineOperand comments. 7efabe5.
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The MachineVerifier was passed up by about 35% through optimisations to calcRegsPassed (converting it reverse post order traversal). It was then sped up by another 15-20% by optimising the set representation. 6f87b16, b3bce6a.
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The scalar evolution expander gained new cost models. cc29600, 756af2f, 0f3c9b5, and more.
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An llvm-gsymutil was started that can convert object files to GSYM and perform lookups. 2f6cc21.
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InstCombine was altered to eliminate dead instructions earlier. 4ef272e.
Clang commits
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Clang now supports output constraints on
asm goto. 50cac24. -
LLVM IR for C++ operator new now contains additional attributes beyond
noalias, when appropriate. 3dd5a29.