Welcome to the 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.

The next Cambridge LLVM Social will take place on the 25th of June .

Evan Swick has written a blog post about Swift internals using information gleaned from reverse engineering Swift binaries and the runtime.

Philip Reames has written another blog post about the support for precise relocating GC he has been working on with his colleagues. In this post, he describes the IR restrictions for late safepoint placement .

Tim Northover has written an RFC on adding cmpxchg weak to the LLVM IR. This seems to have been rapidly accepted as patches were commited this week.

Mark Tullsen is working on a tool that allows programmers to write custom program properties in a high level DSL. They are using libclang but are missing the ability to perform transformations on the AST. David Chisnall gives a good motivation for why AST transformations are not supported.

Apple are advertising for engineers to join their Swift team. This started a discussion about what the rules about job postings to the LLVM list should be and also elicited another response from Chris Lattner on whether Swift will be open-sourced. "You can imagine that many of us want it to be open source and part of llvm, but the discussion hasn't happened yet, and won't for some time."

Alp Toker has announced to those using LLVM that the llvm/Config/config.h header is becoming internal to the LLVM source tree. Out-of-tree LLVM-based projects should be updated.

Tom Stellard has announced to the list that setOperationAction(ISD::SELECT_CC, MVT::Other, Expand) is no longer supported and you must explicitly set the SELECT_CC operations for each supported type.