[llvm] [RISCV] Cost UDIV/UREM by a constant power of 2 as a SHL/AND in getArithmeticInstrCost() (PR #179570)

[Craig Topper via llvm-commits]

topperc wrote:

> @topperc Ping! Do you think it would make sense to just duplicate the code in our RISCV backend and not worry about trying to pull out the redundant optimizations across backends for the sake of simplicity (i.e. not needing to get approval across all backends)

We can just put it in RISC-V.

https://github.com/llvm/llvm-project/pull/179570