Printing long double register pairs on s390x

Is there a way to print the long double value of a register pair?  If
I read the Principles of Operation correctly, that's how long double
values are stored.  I couldn't find any obvious way, and the manual
doesn't mention anything, either.

(I recently had to look into a floating point issue, but it turned out
that it was underlinking of libm, so that the compat double functions
were called with long double arguments, so not much actual debugging
needed.)