Loop rotation clones instruction from the old header into the preheader. If there were uses of values produced by these instructions that were outside the loop, we have to insert PHI nodes to merge the two values. If the values are used by DbgIntrinsics they will be used as a MetadataAsValue of a ValueAsMetadata of the original values, and iterating all of the uses of the original value will not update the DbgIntrinsics. The new code checks if the values are used by DbgIntrinsics and if so, updates them using essentially the same logic as the original code.
The attached testcase demonstrates the issue. Without the fix, the DbgIntrinic outside the loop uses values computed inside the loop, even though these values do not dominate the DbgIntrinsic.