LLVM Weekly - #258, December 10th 2018
Welcome to the two hundred and fifty-eighth 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 7.0.1-rc3 has been tagged. The intent is that this is the last release candidate.
Stephen Kelly has blogged on using build tools with clang-tidy.
On the mailing lists
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John Brawn writes about a fascinating regalloc issue. A regression in bzip2 is triggered when there is one more available register, resulting in worse allocation behaviour. Quentin Colombet provides some insight.
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Adam Nemet kicks off a second round of discussions on matrix support in LLVM. This new proposal takes a more scaled back approach.
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Anastasia Stulova has started an RFC thread on preserving the address space of 'this' in C++ methods.
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Lingda Li is seeking feedback for an RFC on the implementation of the OpenMP 5.0 declare mapper directive.
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Hans Wennborg has proposed the 8.0 release schedule, which would see the branch taking place on 16th January and final tag on 27th Feb.
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James Y Knight is keen on moving forwards with the plan for the git monorepo. After another week with no extra concerns, it looks like there may be consensus.
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Tom Stellard reports that a bug fix for 7.0.0 will necessarily lead to an ABI change for a clang-build libLLVM-7.so. He proposes leaving the fix from 7.0.1 and shipping a special 7.0.2/7.1.0 release so users have the option of accepting this ABI change or not.
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Michael Kruse proposes to no longer use LoopIDs as identifiers.
LLVM commits
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A new llvm.experimental.widenable.condition intrinsic was added. This allows the choice between two alternative correct solutions for the same problem or to express guards. r348593.
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It is now possible to mark variadic register operands as defs. r348114.
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Initial support for the 'TAPI' TextAPI proposal landed. This allows conversion between binary shared object stubs and textual counterparts. r348170.
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SimpleLoopUnswitch learned to preserve MemorySSA. r348263.
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A new interface was introduced to observe changes in GISel passes. r348406.
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The IR constant folder no longer assumes all functions are 4-byte aligned. r348571.
Clang commits
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Support for pretokenized headers was removed. This was an experimental feature that was ultimately considered failed. r348266.
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Portability of the Clang python utility scripts to Python 3 was improved. r348126, r348127, r348129, and more.
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The iterator checker learned to warn on decrements past the begin() and end() of containers. r348425.