[llvm-dev] LLVM Weekly - #334, May 25th 2020

[Alex Bradbury via llvm-dev]

LLVM Weekly - #334, May 25th 2020
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/334>.

Welcome to the three hundred and thirty-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](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 10.0.1-rc1 [has been
tagged](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141683.html).

Chris Colman wrote about [improving firmware quality using LLVM and
Clang](https://interrupt.memfault.com/blog/arm-cortexm-with-llvm-clang).

Djordje Todorovic created a [page tracking debug location coverage in
optimised LLVM-produced
code](https://djolertrk.github.io/llvm-debug-loc-stats/).

Min-Yih Hsu blogged about [using LLVM Lit
out-of-tree](https://medium.com/@mshockwave/using-llvm-lit-out-of-tree-5cddada85a78).


## On the mailing lists

* Tom Stellard [proposes changes to the LLVM release
process](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141730.html),
including creating a time-based bug-fix release schedule and eliminating
release candidates for bug-fix releases. It also clarifies rules for what
kinds of backports are accepted during each release phase.

* Nathan Sidwell [shared an implementation of the C++20 module
mapper](http://lists.llvm.org/pipermail/cfe-dev/2020-May/065487.html). This
was written for GCC, but he shares it under the standard LLVM license.

* Vishal Chebrolu will be working on LLVM under GSoC and [shared a proposal
for improving MergeFunctions to incorporate MergeSimilarFunction patches and
ThinLTO
support](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141773.html).

* Xing Guo shared an RFC on [adding DWARF support for
yaml2obj](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141690.html).

* Fangrui Song proposes [an update to the -fuse-ld=
semantics](http://lists.llvm.org/pipermail/cfe-dev/2020-May/065518.html), to
better specifiy the behaviour for prepending `ld.` or `ld64.`.

* There was further discussion around refactoring the class hierarchy of
VectorType. Eli Friedman's
[response](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141783.html) is
perhaps a good starting point.


## LLVM commits

* More documentation on using git was added to the getting started guide.
[b2d733c](https://reviews.llvm.org/rGb2d733c3507).

* The Arm LowOverheadLoops pass can now handle VPT (vector predication)
blocks. [835251f](https://reviews.llvm.org/rG835251f7d99).

* CodeGen was added for the `preallocated` IR constructs for X86.
[8a88755](https://reviews.llvm.org/rG8a88755610d).

* A CanonicalizeFreezeInLoops pass was added to address a performance
degradation. [d9a4a24](https://reviews.llvm.org/rGd9a4a244138).

* It's now possible to generate reproducers for dsymutil.
[92fd397](https://reviews.llvm.org/rG92fd3971e0d).

* A new isMulhCheaperThanMulshift TargetLowering hook was added.
[b631f86](https://reviews.llvm.org/rGb631f86ac5b).


## Clang commits

* A new WebkitRefCntblBaseVirtualDtor static analyzer check was implemented,
performing analysis of WebKit's reference counted smartpointers.
[f7c7e8a](https://reviews.llvm.org/rGf7c7e8a523f).

* Support for the nomerge function attribute was added. When added to a
statement containing call expressions, those expressions won't be merged
during optimisation. [e36076ee](https://reviews.llvm.org/rGe36076ee3a2).

* An `addrspace_cast` operator was added for OpenCL in C++ mode.
[a6a237f](https://reviews.llvm.org/rGa6a237f2046).

* ABIInfo and TargetCodeGenInfo were implemented for the AIX ABI.
[7f5d91d](https://reviews.llvm.org/rG7f5d91d3ffe).


## Other project commits

* Work to improve LibFuzzer performance by changing how weights are assigned
to seeds was committed. [e2e38fc](https://reviews.llvm.org/rGe2e38fca64e).

* LLVM's libc implementation gained memset and bzero.
[6ca54e0](https://reviews.llvm.org/rG6ca54e01146).

* The LLD Mach-O linker gained support for `-order_file` and
`.sbuections_via_symbols`. [55e9eb4](https://reviews.llvm.org/rG55e9eb416ee),
[4eb6f48](https://reviews.llvm.org/rG4eb6f4854eb).