[llvm] [RISCV][TTI] Implement getAddressComputationCost() in RISCV TTI. (PR #149955)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

LGTM. I looked at the two loops in the diff and it does look like they were probably unprofitably vectorized. gather_scatter needs a vsll.vi to scale the offsets, and store_factor_4_reverse needs a vwmulsu.vx.

https://github.com/llvm/llvm-project/pull/149955