LLVM Weekly - #36, Sep 8th 2014

Welcome to the thirty-sixth 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 https://llvmweekly.org and pass it on to anyone else you think may be interested. Please send any tips or feedback to [email protected], or @llvmweekly or @asbradbury on Twitter.

News and articles from around the web

The biggest news this week is of course undoubtedly the long-awaited release of LLVM/Clang 3.5. See the release notes for a full breakdown of what's changed.

Rhine, a Clojure-inspired Lisp with an LLVM JIT backend has been released (or at least, I wasn't aware of it before). There's plenty of discussion about it over at HN.

Intel have released a new version of their CilkPlus LLVM-basd compiler. This releases implements support for version 1.2 of Intel's Cilk Plus Language Extension Specification.

On the mailing lists

• Hal Finkel is calling for testers of the new contrext-free language pointer aliasing analysis algorithm. As well as some speedup, there are some benchmark slowdowns which sound worth of further investigation.

• Richard Pennington is seeking feedback on his proposal for a cross compiler config file format for Clang. The initial prototype spec is described over at his blog.

• Balaram Makam triggered an interesting discussion on whether a particular case of loop-invariant code motion can be considered safe.

LLVM commits

• LLVM gained a new alias analysis implementation, the CFL (Context-free language) alias analysis algorithm. When bootstrapping LLVM, this pass gives 7-8% NoAlias responses to queries that TBAA and BasicAA couldn't answer. r216970.

• The old JIT has finally been removed. r216982.

• FastISel gained the option to skip target-independent instruction selection. This is now used by AARch64, which uses target-dependent instruction selection only. r216947, r216955.

• MCAnalysis has been removed. The code was judged to be buggy and poorly tested. r216983.

• AArch64 gained a pass to try to remove redundant comparison operations. r217220.

• FastISel has seen some spring cleaning. r217060.

Clang commits

• VariantMatcher::MatcherOps was modified to reduce the amount of generated code. This reduces object size and compilation time. r217152.

• Support for the 'w' and 'h' length modifiers in MS format strings was added. r217195, r217196.

• A new warning is born. -Wunused-local-typedef will warn about unused local typedefs. r217298.

Other project commits

• LLDB has gained initial support for 'type validators'. To quote the commit message, "Type Validators have the purpose of looking at a ValueObject, and making sure that there is nothing semantically wrong about the object's contents For instance, if you have a class that represents a speed, the validator might trigger if the speed value is greater than the speed of light". r217277.

• It is now possible to build libc++ on systems without POSIX threads. r217271.

• A target.process.memory-cache-line-size option has been added to LLDB which changes the size of lldb's internal memory cache chunks read from the remote system. r217083.