[llvm-dev] LLVM Weekly - #257, December 3rd 2018

[Alex Bradbury via llvm-dev]

LLVM Weekly - #257, December 3rd 2018
=====================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/257>.

Welcome to the two hundred and fifty-seventh 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

The EuroLLVM [call for
participation](http://lists.llvm.org/pipermail/llvm-dev/2018-November/128105.html)
is out. Talks, tutorials, student research competition entries, lightning
talks, birds of a feather sessions, and posters are all encouraged. The
submission deadline is January 13th. EuroLLVM will be held in Brussels on
April 8th-9th.

On Wednesday 12th December, the Zurich LLVM Compiler Social will host a talk
from Sebastian Ullrich "Towards Lean 4: An Optimized Object Model for an
Interactive Theorem Prover".
[Register](https://www.meetup.com/llvm-compiler-and-code-generation-socials-zurich/events/vxmqlqyxqbrb/)
on meetup.com if you'd like to attend.


## On the mailing lists

* Gábor Horváth has written up an RFC on [implementing Lifetime
Analysis](http://lists.llvm.org/pipermail/cfe-dev/2018-November/060355.html).
As proposed by Herb Sutter, this would diagnose many common cases of
user-after free in C++ code.

* Piotr Padlewski has a new RFC on [adding a 'supported optimizations'
attribute](http://lists.llvm.org/pipermail/llvm-dev/2018-December/128178.html).

* Oliver Stannard has written an RFC on [checking inline assembly for
validity](http://lists.llvm.org/pipermail/llvm-dev/2018-November/127968.html).
He follows up to explain [why he thinks this belogns in the assembler
parser](http://lists.llvm.org/pipermail/llvm-dev/2018-November/128007.html)
rather than the frontend.

* Daniel Sanders has updated his thread on tablegen-erated GlobalISel combine
rules with [examples rewritten to use
DAGs](http://lists.llvm.org/pipermail/llvm-dev/2018-November/128009.html).

* Brian Gesiak
[proposes](http://lists.llvm.org/pipermail/llvm-dev/2018-November/128139.html)
that bugpoint should be willing to look for 'opt' in the same directory as the
bugpoint executable rather than just the PATH.

* Francesco Ptrogalli
[proposes](http://lists.llvm.org/pipermail/llvm-dev/2018-November/128134.html)
re-implementing `-fveclib` with OpenMP.


## LLVM commits

* Support was added for profile-driven cache prefetching on X86.
[r347596](https://reviews.llvm.org/rL347596).

* A new stack safety analysis was implemented. It determines if stack
allocated variables can be considered "safe" from memory access bugs and can
be used by sanitizers to avoid unnecessary instrumentation.
[r347612](https://reviews.llvm.org/rL347612).

* TableGen gained basic support for preprocessing directives
(ifdef/else/endif/define). [r347686](https://reviews.llvm.org/rL347686).

* InstSimplify learned to fold a select with an implied condition.
[r347896](https://reviews.llvm.org/rL3447896).

* PatFrag predicate code can now access captured operands.
[r347992](https://reviews.llvm.org/rL347992).

* Codegen was implemented for cmpxchg on RISC-V RV32IA. This finishes the
series of patches providing new target-independent hooks for late expansion of
atomics as described in [this
RFC](https://lists.llvm.org/pipermail/llvm-dev/2018-June/123993.html).
[r347914](https://reviews.llvm.org/rL347914),
[r347971](https://reviews.llvm.org/rL347971).


## Clang commits

* All analyzer config options will now be evaluated before analysis, allowing
better error reporting. [r348031](https://reviews.llvm.org/rL348031),
[r348038](https://reviews.llvm.org/rL348038).

* clang-tidy got better at flagging narrowing conversions.
[r347570](https://reviews.llvm.org/rL347570).


## Other project commits

* A CMake build system was added for libclc.
[r347667](https://reviews.llvm.org/rL347667).

* dynarray was removed from libcxx as there are no longer plans for it to be
standardised. [r347783](https://reviews.llvm.org/rL347783).