[llvm] [SelectionDAG] Change SSUBO to do (LHS < RHS) XOR (RESULT < 0) (PR #191747)

[Jay Foad via llvm-commits]

jayfoad wrote:

I guess checking `result < 0` is cheaper than `RHS > 0` when you're working with multi-word values. Was that the reason?

https://github.com/llvm/llvm-project/pull/191747