[llvm] [ExpandMemCmp] Recognize canonical form of (icmp sle/sge X, 0) in getMemCmpOneBlock. (PR #121540)

[Philip Reames via llvm-commits]

preames wrote:

We seem to have UCMP and SCMP SelectionDAG nodes, are these cases simply missing generic DAG combines?  No objection to this patch, just wondering about possible followup.  

https://github.com/llvm/llvm-project/pull/121540