Alex Bradbury via llvm-dev
2017-Feb-27 12:22 UTC
[llvm-dev] LLVM Weekly - #165, Feb 27th 2017
LLVM Weekly - #165, Feb 27th 2017 ================================ If you prefer, you can read a HTML version of this email at <http://llvmweekly.org/issue/165>. Welcome to the one hundred and sixty-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. ## News and articles from around the web The list of [accepted sessions for EuroLLVM 2017](http://llvm.org/devmtg/2017-03//2017/02/20/accepted-sessions.html) has now been announced. Félix Cloutier has written a blog post about [how C compilers optimise divisions](https://zneak.github.io/fcd/2017/02/19/divisions.html). This post from Krister Walfridsson looks at [heuristics for estimating branch probabilities in GCC](https://kristerw.blogspot.co.uk/2017/02/branch-prediction.html), as well as discussing branch prediction more generally. ## On the mailing lists * Stephen Cross is looking for feedback on [his plans to refactor Clang's target-specific ABI logic](http://lists.llvm.org/pipermail/cfe-dev/2017-February/052772.html). * Paul Robinson has [proposed setting Clang's default C++ dialect to C++11](http://lists.llvm.org/pipermail/cfe-dev/2017-February/052820.html). * Johannes Doerfert is still seeking feedback on the Parallel IR proposal and has [updated the thread](http://lists.llvm.org/pipermail/llvm-dev/2017-February/110501.html) to note initial patches and a documentation draft are now available. * Ivan A. Kosarev has shared on RFC on [supporting sanitizers on systems without virtual memory support](http://lists.llvm.org/pipermail/llvm-dev/2017-February/110479.html). * Hans Wennborg has shared an update on the [status of the 4.0.0 release](http://lists.llvm.org/pipermail/llvm-dev/2017-February/110453.html), listing the current blockers. * Ashutosh Nema [proposes](http://lists.llvm.org/pipermail/llvm-dev/2017-February/110424.html) adding support for vectorising epilogue loops generated to handle remaining iterations for loops with unknown iteration counts. ## LLVM commits * A patch to enable splitting some critical edges from indirect branches has landed. This is motivated by the observation that a clang-compiled Python interpreter can be significantly (2.5x) slower on some workloads than a GCC-compiled interpreter, due to unnecessary spills around the computed goto in the main interpreter loop. [r296149](http://reviews.llvm.org/rL296149). * The WebAssembly backend now supports the experimental Wasm object file encoding. [r296190](http://reviews.llvm.org/rL296190). * The MemorySSA updater now allows aliasing stores to be added. [r295677](http://reviews.llvm.org/rL295677). * Propagation for poison values has been made more aggressive. [r295809](http://reviews.llvm.org/rL295809). * An initial X86InstructionSelector has been implemented as part of the work towards X86 GlobalISel support. [r295824](http://reviews.llvm.org/rL295824). * The AArch64RedundantCopyElimination pass learned to do simple copy propagation. [r295863](http://reviews.llvm.org/rL295863). ## Clang commits * When producing UBSan-instrumented code, checks for promoted arithmetic will no longer be generated. [r296213](http://reviews.llvm.org/rL296213). * Work has started on refactoring lib/Drive/Tools.cpp, splitting architecture-specific helpers out into separate files. [r296056](http://reviews.llvm.org/rL296056). ## Other project commits * The LLD introductory documentation has seen a large update, including new link-time performance benchmarks. e.g. a debug build of mysqld takes 7.09s with GNU ld, 2.49s with GNU gold, and 1.31s with LLD. [r296072](http://reviews.llvm.org/rL296072). * LLDB gained support for hardware breakpoints on ARM and AArch64 Linux. [r296119](http://reviews.llvm.org/rL296119). * New LLD code comments warn about the dangers of copy relocations. [r296522](http://reviews.llvm.org/rL295622), [r295632](http://reviews.llvm.org/rL295632).