[llvm-dev] LLVM Weekly - #396, August 2nd 2021

Mon Aug 2 10:36:26 PDT 2021

On Mon, 2 Aug 2021 at 18:00, Alex Bradbury <asb at asbradbury.org> wrote:
>
> LLVM Weekly - #396, August 2nd 2021
> ===================================
>
> If you prefer, you can read a HTML version of this email at
> <http://llvmweekly.org/issue/396>.
>
> Welcome to the three hundred and ninety-sixth 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](https://www.linkedin.com/in/alex-bradbury/). Subscribe to future
> issues at <http://llvmweekly.org> and pass it on to anyone else you think may
> be interested. Please send any tips or feedback to <asb at asbradbury.org>, or
> @llvmweekly or @asbradbury on Twitter.
>
>
> ## News and articles from around the web
>
> LLVM 13.0.0 [has
> branched](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151956.html) and
> the first release candidate is [expected
> today](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151983.html).
>
>
> ## On the mailing lists
>
> * Jeremy Morse is [seeking
>   testers](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151965.html)
>   for the new variable location tracking solution that has been added to LLVM,
>   but is off by default.
>
> * Luke Kenneth Casson Leighton posted an RFC on a proposed [vector/SIMD ISA
>   context
>   abstraction](https://lists.llvm.org/pipermail/llvm-dev/2021-July/152008.html).
>
> * Ben Gamari wrote to llvm-dev about a proposed change to the GHC calling
>   convention, [querying if this may cause an issue for
>   LLVM](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151995.html).
>
> * Michał Górny
>   [shared](https://lists.llvm.org/pipermail/lldb-dev/2021-July/016975.html)
>   that Mortiz Systems has been contracted to enable KGDB compatibility in LLDB
>   and so will be working on improving compatibility between LDB and the
>   gdbserver protocol as part of this.
>
> * Thomas Goodfellow [asked for
>   advice](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151945.html) on
>   building compiler-rt for RISC-V and received answers from [Fāng-ruì
>   Sòng](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151950.html) and
>   [Luís
>   Marques](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151962.html).
>
> * Teresa Johnson provided [input from an ThinLTO
>   perspective](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151948.html)
>   on function specialization.
>
> * Geoffrey Martin-Noble shared that [pre-merge checks have been set up for the
>   Bazel build of
>   LLVM](https://lists.llvm.org/pipermail/llvm-dev/2021-July/151982.html).
>
>
> ## LLVM commits
>
> * A jump-threading optimisation was added for deterministic finite automata
>   was added. One well-known input where this optimisation may be triggered is
>   the `core_state_transition` function of coremark.
>   [02077da](https://reviews.llvm.org/rG02077da7e7a8).
>
> * Graph reordering in the SLP vectorizer has been improved.
>   [e408d1d](https://reviews.llvm.org/rGe408d1dfab42).
>
> * AArch64 GlobalISel will no longer optimise away redundant branches at `-O0`,
>   in order to improve the debuggability of emitted code.
>   [c5d84d2](https://reviews.llvm.org/rGc5d84d2eb35c).
>
> * The CallPenalty for the inliner is now configurable.
>   [46c0366](https://reviews.llvm.org/rG46c03668774c).
>
> * Support for the arch14 SystemZ architecture was added to the SystemZ
>   backend. [8cd8120](https://reviews.llvm.org/rG8cd8120a7b5d).
>
> * Emscripten exception handling now works with Emscripten SjLJ
>   (setjmp/longjmp). [c285a11](https://reviews.llvm.org/rGc285a11efdb0).
>
> * Initial code was added to generate assembly files on z/OS.
>   [a8cfa4b](https://reviews.llvm.org/rGa8cfa4b9bda3).
>
> * `LLVM_ATTRIBUTE_NORETURN` has been replaced with `[[noreturn]]` in the LLVM
>   codebase. [6da3d8b](https://reviews.llvm.org/rG6da3d8b19c32).
>
> * A new feature was introduced in AArch64 for Scalable Matrix Extension (SME)
>   streaming mode. [3a349d2](https://reviews.llvm.org/rG3a349d22692c).
>
>
> ## Clang commits
>
> * `#pragma include_instead` was introduced, which can be used by system
>   headers to indicate to a tool that the file including this pragma shouldn't
>   be directly included by user code.
>   [e8a64e5](https://reviews.llvm.org/rGe8a64e549126).
>
> * `#pragma clang deprecated` was added in order to enable deprecation of
>   preprocessor macros. [26c695b](https://reviews.llvm.org/rG26c695b78930).
>
> * Clang option `-ffp-model=precise` now enables `-ffp-contract=on`.
>   [48ad446a](https://reviews.llvm.org/rG48ad446a0fb2).
>
> * Support was added for the `-ffp-eval-method` command-line option.
>   [66ddac2](https://reviews.llvm.org/rG66ddac22e2a7).
>
>
> ## Other project commits
>
> * A new on-by-default libc++ CMake option was added to disable the usage of
>   incomplete headers which aren't guaranteed to be ABI stable.
>   [71909de](https://reviews.llvm.org/rG71909de37495).

A slight correction - I'd got the wrong end of the stick from reading
the commit message on this one. You have to opt-in to disable
incomplete headers.

> * The Hierarchical Trace Representation (HTR) format for large traces (e.g.
>   processor traces from Intel PT) was introduced to LLDB.
>   [aad17c5](https://reviews.llvm.org/rGaad17c55a811).
>
> * A prototype of a new OpenMP GPU device runtime library was introduced.
>   [67ab875](https://reviews.llvm.org/rG67ab875ff578).
>
> * Initial Objective-C and Swift support was added to the ORC runtime's
>   MachOPlatform. [cdcc354](https://reviews.llvm.org/rGcdcc35476833).
>
> * The migration of Flang's tests to GTest has been completed.
>   [65436e6](https://reviews.llvm.org/rG65436e6ba127).
>
> * A new `-Bsymbolic-non-weak-functions` option was added to the LLD ELF
>   linker. [b06426d](https://reviews.llvm.org/rGb06426da764a).
>
> * LLDB gained a new option to write memory tags (when Arm's Memory Tagging
>   Extension is supported). [6a7a2ee](https://reviews.llvm.org/rG6a7a2ee8161d).
>
> * MLIR's Python build support was reworked.
>   [310c949](https://reviews.llvm.org/rG310c9496d809).
>
> * The llvm-omp-device-info tool was added.
>   [313c523](https://reviews.llvm.org/rG313c5239959b).