How do we access higher order bits of a register?

[Ayonam Ray]

Hi,

I wanted to write an RTL that would access the higher order bits of a
register.  I saw that high:<mode> works only with constants or labels.
 The subreg:<mode> only takes the lower order bits.  Can't find any
way to address the higher order bits.  Any help would be appreciated.

Thanks and regards
Ayonam