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Re: [avr-gcc-list] saving __zero_reg__ in interrupt

From: Frieder Ferlemann
Subject: Re: [avr-gcc-list] saving __zero_reg__ in interrupt
Date: Tue Jan 30 21:46:04 2001

> ATMega161 has a set of MUL instructions. They return the result in R0:R1.
Thats why I don't see it on a 90S2313...

> A better solution would probably be to use a different register as the
> zero-register in the future. But that will raise more compability
> issues...
And they will be hard to debug....

On the other hand if one ever plans to change the register usage 
it would be a good time to do it now? 
(I'm not familiar with the release policy of gcc, but looking from
the outside: there was the avr patch to 2.95 and the next official
gcc version is not yet released. 
So it is the last chance before an official gcc with AVR goes out?)

If R0:R1 got a special meaning for the Atmel Mega series, which registers
get a special meaning next? 
Would it be save to use R2 as __zero_reg__ or rather R4 (in the hope
there will be a AVR Giga series)?



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