der Mouse <mouse@Rodents.Montreal.QC.CA> writes:

I think the short version is:

> (a) hardware
 The zero register.

> (b) palcode
 No registers in the ordinarly avaliable register set.

> (c) kernel
 The only thing that seems likely to cause trouble here is signal
 delivery, which will depend on the stack pointer being okay and safe
 to write to addresses below it.

> (d) compiler
 This is trickier. AT and GP are the ones most likely to get you in
 trouble, but at this point you'll need to get a good sense for the
 ABI, and I'm not sure how you're planning for your asm code to
 interact with compiled code. Within a leaf function, I think you can
 bash everything except sp (see above) and you only need to restore
 s0-s6 and ra.

        - Nathan