>I got same problem on newsmips. mips_reg_t seems MIPS64 stuff
>in nisimura-pmax-wscons branch, Nisimura-san?

I had the same problem on pmax. I just removed the casts.  

I'd pull up types.h from the nisimura-pmax-wscons branch, but I dont
understand how the mips_reg_t is supposed to work on platforms which
(like pmax) can have either mips32 or mips64 [sic] CPUs.

If i understand it properly, the intent is to use 64-bit registers,
say in hand-tuned assembler (like bcopy).  So on a 64-bit mips, the
kernel needs to save all 64 bits of the integer registers.

Should we do `struct frame' as a union with space for both 32-bit or
64-bit registers, with runtime code to do the appropriate casts?  if
the trap-handling code saves the registers in the right width, that
should all just work...