[Bug target/56439] global and local register variables don't work in a useful way -- AVR

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56439

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2013-02-25 03:53:25 UTC ---
(In reply to comment #2)
> Any specific sections you can point me to? I'd be interested to hear a
> justification for this behavior.

Simple answer, an interrupt can happen any time after the access/assignment of
the global register variable so it needs to be set to the value and treated as
a volatile variable.