[llvm] [AMDGPU][TTI] Add Target Hook for Instruction Uniformity (getInstructionUniformity) (PR #137639)

[Jay Foad via llvm-commits]

jayfoad wrote:

> I don't know what this new hook gives that the existing ones do not handle already

I think this is supposed to address #131779 (but in its current form it does not).

https://github.com/llvm/llvm-project/pull/137639