[llvm] [LoopVectorize][NFC] Centralize the setting of CostKind (PR #121937)

[David Sherwood via llvm-commits]

david-arm wrote:

Thanks for making the changes - I left one more comment about a couple more cases I think are missing and then it looks good to go!

One thing that might be worth considering - `getAddressComputationCost` doesn't currently take a cost kind parameter, but the function is used in a few places. It seems to assume a reciprocal throughput cost at the moment. However, I'm happy if you prefer to deal with this in a seperate patch.

https://github.com/llvm/llvm-project/pull/121937