However, all of this activity won't be found in next month's LLVM 3.8 release since it's already branched but rather is new work going into LLVM 3.9. This latest LLVM 3.9 code drops compatibility for the Mesa 11.0 series, adds some new intrinsics, some new tests were added, and more.
Interestingly a lot of the new work is being done by a name not familiar to those tracking the open-source AMD Linux driver development: Matt Arsenault. He's an engineer at AMD working on OpenCL and now seems to be contributing more to their AMDGPU LLVM back-end.
As mentioned in New AMDGPU Details & Looking Forward To Major Radeon Linux Improvements In 2016, they are investing heavily into their LLVM GPU back-end, getting more engineers working on this back-end, and will play a big role in their new compute compiler.
You can dig through all of the latest AMD GPU back-end code via the LLVM Git mirror.