conditional register usage via function attribute - how?

[Dylan_S_Cuthbert@hq.scei.sony.co.jp]

Anybody know the best way to implement conditional register usage via a function
attribute?

I was thinking along the lines of VALID_MACHINE_DECL_ATTRIBUTE doing the
disabling/enabling of fixed_regs - but what if the attribute *isn't* specified -
ie. how do I reset the fixed_regs flags to their defaults after the function?

If the worst comes to the worst I could always use a pragma directive I suppose
:-)

Regards

Dylan Cuthbert