LLVM Project News and Details from the Trenches

Monday, May 16, 2016

LLVM Weekly - #124, May 16th 2016

Welcome to the one hundred and twenty-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. 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.

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News and articles from around the web

The main news this week is the announcement of Scala-native, an ahead-of-time compiler for Scala using LLVM. Jos Dirkens has written a getting started guide if you want to compile it and try it out. There's also more information in the slides from the announcement talk.

On the mailing lists

LLVM commits

  • The outdated guide on cross-compiling LLVM has been brought up to date. r269054.

  • The WebAssembly backend gained preliminary fast instruction selection (fast-isel) support. r269083, r269203, r269273.

  • Loop unrolling (other than in the case of explicit pragmas) is now disabled at -Os in LLVM. You may recall last week it was enabled for -Os in Clang, but with different thresholds. r269124.

  • A new cost-tracking system has been implemented for the loop unroller. r269388.

  • LLVM's Sparc backend has seen the addition of more LEON-specific features, e.g. signed and unsigned multiply-accumulate. r268908.

  • llc's -run-pass option will now work with any pass known to the pass registry. Previously it would silently do nothing if you specify indirectly added analysis passes or passes not present in the optimisation pipeline. r269003.

  • WebAssembly register stackification and coloring are now run very late in the optimisation pipeline. The commit message suggests it's useful to think of these passes as domain-specific liveness-based compression rather than a conventional optimisation. r269012.

  • When declaring global in textual LLVM IR, you must now assign them with e.g. @0 = global i32 42. r269096.

  • The internal assembler is now enabled by default for 32-bit MIPS targets. r269560.

Clang commits

  • Clang now supports __float128. r268898.

  • Clang gained a new warning that triggers when casting away calling conventions from a function. r269116.

  • The recently developed include-fixer tools now has documentation. r269167.

Other project commits

  • compiler-rt's CMake build system can now build builtins without a full toolchain, allowing you to bootstrap a cross-compiler. r268977.

  • LLD will now sort relocations to optimise dynamic linker performance. r269066.