RFC: AVR interrupt handling issue

[Ian Molton]

Replying to myself for a moment - it would appear that
-fcall-used-reg="rXX" would do what I want (in theory), except for:

1) It doesnt appear to be documented much, or even work on AVR.

2) It applies to entire files, but I just want it to apply to one function.

Does anyone know if any work has been done in that direction? or is it
just abandoned?

-Ian