[llvm] [RISCV] custom scmp(x, 0) and scmp(0, x) lowering for RVV (PR #151753)

[Craig Topper via llvm-commits]

topperc wrote:

Please put the tests in a separate commit within the PR so we can see the original codegen and the change.

https://github.com/llvm/llvm-project/pull/151753