[clang] [llvm] [AMDGPU][WIP] Add support for i64/f64 readlane, writelane and readfirstlane operations. (PR #89217)

[Vikram Hegde via cfe-commits]

vikramRH wrote:

new commit extends @jayfoad's implementation with GIsel support.  yet to add tests for half, floats and some vectors

https://github.com/llvm/llvm-project/pull/89217