[LLVMdev] LLVM Weekly - #5, Feb 3rd 2014

Tue Feb 4 11:03:08 PST 2014

Alex,

Just wanted to say that this newsletter is *extremely* useful for someone
like me -- who is interested in clang / llvm evolution, but doesn't have
time to keep track of all the mailing lists.

Thank you! -- keep up the good work!

Andrey

On Mon, Feb 3, 2014 at 6:23 PM, Alex Bradbury <asb at asbradbury.org> wrote:

> LLVM Weekly - #5, Feb 3rd 2014
> ==============================
>
> If you prefer, you can read a HTML version of this email at
> <http://llvmweekly.org/issue/5>
>
> Welcome to the fifth 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. I've been
> keeping the [@llvmweekly Twitter account](https://twitter.com/llvmweekly)
> updated throughout the week, so follow that if you want more frequent news
> updates.
>
> I'm afraid my summary of mailing list activities is much less thorough than
> usual, as I've been rather busy this weekend both moving house and
> suffering
> from a cold. Do ping me if you think I've missed anything important.
>
> ## News and articles from around the web
>
> This weekend there was an LLVM devroom at FOSDEM 2014. Slides have [already
> been posted](http://llvm.org/devmtg/2014-02/) for some of the talks.
> Hopefully
> videos will follow.
>
> Pocl (Portable Computing Language) 0.9 has been
> [released](http://portablecl.org/pocl-0.9.html). Pocl aims to be an
> efficient
> MIT-licensed implementation of the OpenCL 1.2 standard.
>
> Mike Ash has published a useful [introduction to
> libclang](
> https://mikeash.com/pyblog/friday-qa-2014-01-24-introduction-to-libclang.html
> ).
>
> Ever wanted to use LLVM from within Rust? This [blog post will tell you
> how](http://hydrocodedesign.com/2014/01/31/llvm-with-rust/).
>
> Phoronix has published a [benchmark of Clang 3.4 vs GCC 4.9.0 20140126 on
> AMD
> Kaveri](
> http://www.phoronix.com/scan.php?page=article&item=amd_kaveri_gcc49clang34&num=1
> ).
>
> ## On the mailing lists
>
> * A question about the status of [SEH support in
> LLVM/Clang](
> http://article.gmane.org/gmane.comp.compilers.clang.devel/34747)
> was quickly derailed after the expiration of a key patent on SEH in June
> was
> brought up. The conversation moved to LLVM's [developer policy on
> patents](http://llvm.org/docs/DeveloperPolicy.html#patents) and whether
> the
> LLVM or Clang mailing lists are a suitable place for their discussion. In
> the
> end, Chris Lattner [chimes in to clarify the
> policy](http://article.gmane.org/gmane.comp.compilers.clang.devel/34810).
> The
> technical discussion [moved to this
> thread](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69945).
>
> * Pekka Jääskeläinen answers a bugpoint question with a [useful guide on
> using
> bugpoint with a custom exec-command
> option](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69807).
>
> * Nick Lewcky suggests [making datalayout a mandatory part of an LLVM
> module](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69890).
>
> * Chandler Carruth has proposed in an RFC that [BlockFrequency is the wrong
> metric](http://article.gmane.org/gmane.comp.compilers.llvm.devel/70027)
> for
> profile info.
>
> * Sara Elshobaky asks for advice on finding the [number of instructions
> executed when running LLVM bytecode under
> lli](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69797).
> There
> are a number of suggestions including callgrind, Pin, and other similar
> tools.
>
> * Markus Timpl raises an interesting question about [describing a load
> instruction that changes the value of two
> registers](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69852
> ).
>
> * Baoshan Pang writes to the LLVM list asking [how to start getting
> involved
> in LLVM](http://article.gmane.org/gmane.comp.compilers.llvm.devel/69973).
> If
> you've emailed me suggesting you'd like more pointers on how to get stuck
> in
> to LLVM, this thread is for you.
>
> ## LLVM commits
>
> * The ARM exception handling ABI
> ([EHABI](
> http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
> ))
> is now enabled by default.
> [r200388](http://llvm-reviews.chandlerc.com/rL200388).
>
> * TargetLowering gained a hook which targets can implement to indicate
> whether
> a load of a constant should be converted to just the constant.
> [r200271](http://llvm-reviews.chandlerc.com/rL200271).
>
> * Line table debug info is now supported for COFF files when targeting
> win32.
> [r200340](http://llvm-reviews.chandlerc.com/rL200340).
>
> * LLVM now has the beginnings of a line editor library, initially to be
> used
> by clang-query but possibly consumed by LLDB as well in the future.
> [r200595](http://llvm-reviews.chandlerc.com/rL200595).
>
> * The R600 backend learned intrinsics for `S_SENDMSG` and
> `BUFFER_LOAD_DWORD*`
> instructions. [r200195](http://llvm-reviews.chandlerc.com/rL200195),
> [r200196](http://llvm-reviews.chandlerc.com/rL200196).
>
> * The loop vectorizer gained a number of flags to help experiment with
> changing thresholds. It now also only unrolls by powers of 2.
> [r200212](http://llvm-reviews.chandlerc.com/rL200212),
> [r200213](http://llvm-reviews.chandlerc.com/rL200213).
>
> * The loop vectorizer now supports conditional stores by scalarizing (they
> are
> put behind an if). This improves performance on the SPEC libquantum
> benchmark
> by 4.15%.
> [r200270](http://llvm-reviews.chandlerc.com/rL200270).
>
> * MCSubtargetInfo is now explicitly passed to the `EmitInstruction`,
> `EmitInstTo*`, `EncodeInstruction` and other functions in the MC module.
> [r200345](http://llvm-reviews.chandlerc.com/rL200345) and others.
>
> * llvm-readobj learned to decode ARM attributes.
> [r200450](http://llvm-reviews.chandlerc.com/rL200450).
>
> * Speculative execution of llvm.{sqrt,fma,fmuladd} is now allowed.
> [r200501](http://llvm-reviews.chandlerc.com/rL200501).
>
> ## Clang commits
>
> * Position Independent Code (PIC) is now turned on by default for Android
> targets. [r200290](http://llvm-reviews.chandlerc.com/rL200290).
>
> * The Parser::completeExpression function was introduced, which returns a
> list
> of completions for a given expression and completion position.
> [r200497](http://llvm-reviews.chandlerc.com/rL200497).
>
> * The default CPU for 32-bit and 64-bit MIPS targets is now mips32r2 and
> mips64r2 respectively. [r200222](
> http://llvm-reviews.chandlerc.com/rL200222).
>
> * The ARM and AArch64 backends saw some refactoring to share NEON
> intrinsics.
> [r200524](http://llvm-reviews.chandlerc.com/rL200524) and others.
>
> ## Other project commits
>
> * Compiler-rt gained a cache invalidation implementation for AArch64
> [r200317](http://llvm-reviews.chandlerc.com/rL200317).
>
> * Compiler-rt now features an optimised implementation of `__clzdi2` and
> `__clzsi2` for ARM. [r200394](http://llvm-reviews.chandlerc.com/rL200394).
>
> * Compiler-rt's CMake files will now compile the library for ARM. Give it
> a go
> and see what breaks. [r200546](http://llvm-reviews.chandlerc.com/rL200546
> ).
>
> * The iohandler LLDB branch was merged in. The commit log describes the
> benefits. [r200263](http://llvm-reviews.chandlerc.com/rL200263).
>
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