[llvm-dev] LLVM Weekly - #332, May 11th 2020

[Alex Bradbury via llvm-dev]

LLVM Weekly - #332, May 11th 2020
=================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/332>.

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](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

Nikita Popov has written a detailed blog post on [making LLVM fast
again](https://nikic.github.io/2020/05/10/Make-LLVM-fast-again.html),
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](https://summerofcode.withgoogle.com/organizations/4674300587540480/#projects).
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](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141436.html).
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](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141497.html).
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](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141452.html).

* ORC JIT Weekly #15 [is
out](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141493.html), 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](http://lists.llvm.org/pipermail/llvm-dev/2020-May/141485.html)
which attracted detailed responses.

* Emre Kultursay queries if anyone has explored a ['just-my-code debugging
mode' for
LLDB](http://lists.llvm.org/pipermail/lldb-dev/2020-May/016194.html).

* Amy Huang wrote an RFC on [adding constructor homing to clang's limited
debug info
mode](http://lists.llvm.org/pipermail/cfe-dev/2020-May/065389.html). 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](http://lists.llvm.org/pipermail/cfe-dev/2020-May/065385.html).


## LLVM commits

* dsymutil gained a new option to print statistics about the `.debug_info`
size. [7fb9bcd](https://reviews.llvm.org/rG7fb9bcd3da6).

* Known bits constant folding in InstSimplify was removed on the basis that
the calculation is expensive but very rarely helps codegen.
[5a22656](https://reviews.llvm.org/rG5a2265647ed).

* More descriptive names are now used for machine basic block sections.
[c8ac29a](https://reviews.llvm.org/rGc8ac29ab1d7).

* LLD's parallel algorithm wrappers were moved up into
`llvm/Support/Parallel.h`. [932f027](https://reviews.llvm.org/rG932f0276ea2).


## Clang commits

* Support for `_ExtInt` was enabled for all in-tree targets.
[8a1c999](https://reviews.llvm.org/rG8a1c999c9b0).

* Support was added for `#pragma float_control`, allowing floating-point
semantics and exception behaviour to be specified for a section of source
code. [f5360d4](https://reviews.llvm.org/rGf5360d4bb33).

* Support for many additional SVE2 builtins was added.
[086722c](https://reviews.llvm.org/rG086722c18e4),
[e46043b](https://reviews.llvm.org/rGe46043bba7a), and many more.


## Other project commits

* Complex numbers, complex addition, and complex subtraction were added to the
standard MLIR dialect. [031265a](https://reviews.llvm.org/rG031265ad8a2),
[5d5f61f](https://reviews.llvm.org/rG5d5f61fc894).

* LLD's Mach-O linker now supports calls to functions in dylibs.
[b3e2fc9](https://reviews.llvm.org/rGb3e2fc931d2).

* LLD now enforces `--` prefixes for options not supported by GNU ld (where
`-option` doesn't need to be supported for compatibility).
[e20a215](https://reviews.llvm.org/rGe20a215992d).

* MLIR now supports merging identical blocks during canonicalisation.
[469c02d](https://reviews.llvm.org/rG469c02d0581).