[libre-riscv-dev] power pc

[Jacob Lifshay]

one other unusual thing about Power, the FP status register has a
whole pile of additional fp status bits that are set by operations,
implementations will need to calculate all the extra bits (not hard,
just means we can't use the FP units we developed without
modification).

Also, 32-bit floats are stored in the FP registers in 64-bit format
(but otherwise behave like 32-bit floats should), this means it will
be more complex to store multiple smaller FP values in a single FP
register.