[clang] [SPIR-V] Add clang builtin for subgroup shuffles (PR #174655)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

> Random question, why are the intrinsics called `spv.wave` when the spec seems to use `subgroup`? I wasn't sure if I should keep that convention or change it in #174862

subgroup (SPIRV), wave (DX), warp (Nvidia), wavefront (AMD). Are all the same thing. We picked wave because its the only one that seems to be used as an api-level name and not a harware unit. It was also the only one that shares a name with a harware unit.

More importantly the intrinsic toggling we are doing is very basic between DirectX and SPIRV so the intrinsic names need to match.



https://github.com/llvm/llvm-project/pull/174655