[clang] [llvm] [AMDGPU] Implement 'llvm.get.fpenv' and 'llvm.set.fpenv' (PR #83906)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

Note that this patch is not quite ready to land. I encountered issues when working with `s_setreg`. The listing of `SOPK` instructions should have this as an instruction that takes a 16-bit zero extended immediate value. However, this was apparently not the case for the `s_setreg` node despite the fact that it was set for the `s_getreg` node. I made the necessary changes to consider this zero extended which makes it work in my case. However, this has exposed some failures in tests mostly relating to flat storage. These tests now fail due to being given a negative immediate value. I'm unsure where the necessary changes need to go to resolve that.

https://github.com/llvm/llvm-project/pull/83906