[llvm] [RISCV][WIP] Enable sink-and-fold for RISC-V. (PR #67602)

[Mikhail Gudim via llvm-commits]

mgudim wrote:

@topperc Sorry for delay with the review, I was away last week. Thanks for working on this, looks great! I prefer this approach to https://github.com/llvm/llvm-project/pull/67024 . Have you seen any changes on  spec? In my testing, this is supposed to improve mcf (but I only have the instruction count, not cycles).

LGTM.

https://github.com/llvm/llvm-project/pull/67602