[llvm-dev] LLVM Weekly - #174, May 1st 2017

[Alex Bradbury via llvm-dev]

LLVM Weekly - #174, May 1st 2017
================================

If you prefer, you can read a HTML version of this email at
<http://llvmweekly.org/issue/174>.

Welcome to the one hundred and seventy-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](http://asbradbury.org). 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

Tanya Lattner is [looking for
volunteers](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112336.html)
to help with system administration, documentation generation and maintenance,
and bugzilla and software management.


## On the mailing lists

* James Molloy has written up an [incredibly helpful description of
GVNSink](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112471.html),
complete with neat ASCII art diagrams.

* Peter Collingbourne has written an RFC on [moving the module summary into
the
irsymtab](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112361.html).

* Tom Stellard has [summarised the outstanding merge requests for
4.0.1-rc1](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112426.html).

* David Gwyne is [looking for
feedback](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112431.html) on
his efforts to support the -msave-args command line option on x86-64.

* Daniel Berlin
[reports](http://lists.llvm.org/pipermail/llvm-dev/2017-April/112481.html) the
old SimplifyInstruction API is about to be removed and documents how to update
any out-of-tree code.


## LLVM commits

* A new, simpler loop unswitching pass has been introduced.
[r301576](http://reviews.llvm.org/rL301576).

* The scalar evolution verifier should no longer suffers from false positives,
though is not yet enabled by default for `EXPENSIVE_CHECKS` builds pending
investigation of a failure triggered in the Hexagon tests.
[r301146](http://reviews.llvm.org/rL301146).

* llvm-xray gained a new graph-diff tool for comparing function graphs
produced by llvm-xray graph. [r301160](http://reviews.llvm.org/rL301160).

* Size and alignment information of register classes has moved to
TargetRegisterInfo. [r301221](http://reviews.llvm.org/rL301221).

* The newly added 'speculatable' function attribute indicates a function has
no side-effects beyond computing its result and has no undefined behaviour.
[r301680](http://reviews.llvm.org/rL301680).


## Clang commits

* Initial code generation for OpenMP's 'distribute parallel for' was added.
[r301223](http://reviews.llvm.org/rL301223).

* More unnecessary UBSan checks have been removed. This time, alignment checks
on allocas with known alignment. [r301377](http://reviews.llvm.org/rL301377).


## Other project commits

* LLD implemented the `--defsym` command-line option.
[r301391](http://reviews.llvm.org/rL301391).

* Linking when using LLD's `-Map` option has been sped up significantly. The
overhead of this option is now about 3x less than before, based on a benchmark
of linking clang. [r301659](http://reviews.llvm.org/rL301659).

* Initial APIs for tracing have been added to LLDB.
[r301389](http://reviews.llvm.org/rL301389).