> I think determing whether CP1 registers exist or not may have additional
> runtime overhead.

It's simple since cpuinfo structure will handsomely encapsulate
processor characteristics.  Holding 'p->p_addr->u_pcb.pcb_fpregs.r_regs'
would bring a handy way to load/store 'FP register' value. 

> Anyway, current fp.S is very ugly, It needs completely rewritten.

You are the best person to do that in the right way.  64bit FP emulation
would be great.

Tohru Nishimura