[llvm] [AMDGPU] Enable vectorization of i8 values. (PR #134934)

[Gheorghe-Teodor Bercea via llvm-commits]

doru1004 wrote:

> LGTM with nits. I think the load/store costs need to be revisited, we're treating them as as cheap as cheap ALU instructions which they certainly are not (also ignoring unaligned cost)

Since this is a problem which affects all load/store instructions regardless of type we will address this in a future PR to maintain consistency.

https://github.com/llvm/llvm-project/pull/134934