Calculates the offset from a pointer, potentially wrapping.
This is implemented as an intrinsic to avoid converting to and from an integer, since the conversion inhibits certain optimizations.
offset intrinsic, this intrinsic does not restrict the
resulting pointer to point into or one byte past the end of an allocated
object, and it wraps with two’s complement arithmetic. The resulting
value is not necessarily valid to be used to actually access memory.
The stabilized version of this intrinsic is