This is similar to what was already done in foldSelectICmpAndOr. Ultimately I'd like to see if we can call foldSelectICmpAnd from foldSelectIntoOp if we detect a power of 2 constant. This would allow us to remove foldSelectICmpAndOr entirely.
As I'm writing this I wonder if we're also missing (icmp slt X, 0) and (icmp sgt X, -1) without any truncates.
The vector tests added should already work without this change since we don't turn compares with ands into truncate for vectors.