Re: [avr-gcc-list] __zero_reg__

[Joerg Wunsch]

As Anich Gregor <address@hidden> wrote:

>When the program is interrupted it is absolutely possible that the
>zero-reg is not zero at this time because it is defined to be zero
>whenever a C function is called - you can do with it whatever you
>want to as long as you make sure that you set it to zero again before
>giving control back to compiler-generated code because it depends on
>that ;)

The biggest problem is that zero_reg as r0 is a poor choice because it
can be clobbered by the hardware multiplication result in the ATmega.
(IMHO, this detail has been unknown to the AVR-GCC developers by the
time they've chosen about zero_reg.)
-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/

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