[Bug target/45263] registers used in __do_global_ctors can get clobbered

[eric.weddington at atmel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45263

--- Comment #10 from Eric Weddington <eric.weddington at atmel dot com> 2010-12-05 19:52:33 UTC ---
(In reply to comment #9)

> Is R15 used anywhere else in startup code that might not obey the register save
> conventions (ie does do_global_ctors need to preserve R15)

I strongly suggest not using R15. The ATtiny10 Family of devices
(ATtiny10/4/5/9/20/40) only has R16-R31. So using R15 won't work for this class
of devices. It would be best if we can find a register that will for all AVR
devices.