The LLVM 64-bit back-end merging that they have been doing over the past several weeks is merging all of the features/improvements found within the existing AArch64 compiler back-end into Apple's "ARM64" back-end that was overall in better shape and easier to be on the receiving end of this work. All of those improvements have now landed into the ARM64 back-end where there's no regressions compared to either back-end previously and everything is in good shape. With that aligned, within the LLVM code-base the Apple ARM64 back-end was then renamed to AArch64 to reflect the official 64-bit ARM architecture title.
The change-over happened this morning with nuking the old back-end and then the renaming. There were also changed to Clang that happened this Saturday morning for the back-end shake-up.
This new and improved 64-bit ARM back-end will be part of LLVM 3.5 that should be officially released in August.