LLVM Project News and Details from the Trenches

Monday, July 14, 2014

LLVM Weekly - #28, Jul 14th 2014

Welcome to the twenty-eighth 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.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@asbradbury.org, or @llvmweekly or @asbradbury on Twitter.

I'll be at the GNU Tools Cauldron 2014 next weekend, being held at the University of Cambridge Computer Laboratory (which handily is also where I work). If you're there, do say hi.

The canonical home for this issue can be found here at llvmweekly.org.

News and articles from around the web

An update on Clang/LLVM on Windows has been posted on the LLVM blog. Impressive progress has been made, and as I mentioned last week the MSVC compatibility page has been updated.

There is (somewhat amazingly) now a Pascal-86 frontend for LLVM. The compiler frontend is written entirely in Python. More information is available in the author's Master's thesis (via Phoronix).

On the mailing lists

LLVM commits

  • FastISel gained some infrastructure to support a target-independent call lowering hook as well as target-independent lowering for the patchpoint intrinsic. r212848, r212849.

  • DominanceFrontier has been templatified, so in theory it can now be used for MachineBasicBlocks (where previously it was only usable with BasicBlocks). r212885.

  • The quality of results for CallSite vs CallSite BasicAA queries has been improved by making use of knowledge about certain intrinsics such as memcpy and memset. r212572.

  • Work on overhauling x86 vector lowering continues. Chandler now reports that with the new codepath enabled, LLVM is now at performance pairty with GCC for the core C loops of the x264 code when compiling for SSE2/SSE3. r212610.

  • ASM instrumentation for AddressSanitizer is now generated entirely in MachineCode, without relying on runtime helper functions. r212455.

  • Generation of the new mips.abiflags section was added to the MIPS backend. r212519.

  • isDereferenceablePointer will now look through some bitcasts. r212686.

Clang commits

  • A new checker was added, to flag code that tests a variable for 0 after using it as a denominator (implying a potential division by zero). r212731.

  • Clang gained initial support for omp parallel for, the omp parallel sections directive, and omp task. r212453, r212516, r212804.

  • On the ARM target, LLVM's atomicrmw instructions will be used when ldrex/strex are available. r212598.

  • Support was adding for mips-img-linux-gnu toolchains. r212719.

Other project commits

  • ThreadSanitizer's deadlock detector is enabled by default after being battle-tested on the Chromium codebase for some time. r212533.

  • Support for Android's bionic C library has been added to libcxx. r212724.

  • LLDB's Python scripting interface should now work on Windows. r212785.

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