[llvm] [WIP][SPARC] Add basic TTI implementation (PR #178843)

[via llvm-commits]

koachan wrote:

Tagging as WIP for now since I'm a bit lost on how to make the `LoopVectorizePass` test; I want to verify that it doesn't try to vectorize anything, so it's the opposite of the tests I've read.

Any advices?

https://github.com/llvm/llvm-project/pull/178843