[llvm] [DAG] Extend the computeOverflowForSignedSub/computeOverflowForUnsignedSub implementations with ConstantRange (PR #67890)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> @RKSimon Do you have more issues/projects I can work on?

#66101 might be interesting - hopefully this can be addressed as a generic DAGCombine fold and not x86-specific

https://github.com/llvm/llvm-project/pull/67890