.hi .lo notations

[Hiroshi Yamauchi]

Hi,

In PrintOptoAssembly output, I see .hi and .lo notations used for
handling 64 bit long values on 32 bit Linux x86. For example, EAX.hi
or EBP.lo.

I heard that they are aliases to other registers. If so, what are the
exact rules about the aliases?

Thanks,
Hiroshi