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

[Ryan Buchner via llvm-commits]

bababuck 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?

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