That came out wrong.
I think a GDB debugging a remote 64 bit MIPS ISA should always expect 64
bit GPRs and 64 bit FPRs when the ISA is 64 bits, regardless of the ABI.
It is quite legitimate, for instance, for GDB to do something as sick-o
as clearing the FR bit and then resume the thread. The register
save/restore code needs to correctly handle this - be it reject the
operation or ``do the right thing''.
But when using rda or gdbserver to debug an o32 application, then for
all intents and purposes we are debugging a 32-bit ISA. The kernel
will not allow us to change the FR bit. The app will never see 64-bit
registers. The 32-bit protocol makes more sense here IMO.