[llvm] [LLVM][AMDGPU] AMDGPUInstCombineIntrinsic for *lane intrinsics (PR #99878)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Is this PR still active? The general direction looks okay to me, but every place that uses UI needs to show why it is _safe_ to continue using UI after each local change to the code.

We probably shouldn't be doing this in InstCombine, if we're doing to do this anywhere. It's going to trigger infrequently 

https://github.com/llvm/llvm-project/pull/99878