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

From: Bernt Hustad Hembre
Subject: Re: [avr-gcc-list] saving __zero_reg__ in interrupt
Date: Tue Jan 30 06:43:04 2001

On Mon, 29 Jan 2001, Frieder Ferlemann wrote:

> > zero it after use).  Interrupt comes in at the right moment (when r1 is
> > nonzero) and you lose.
> ... seems I'm looking for trouble:) 
> I did a scan with grep r1 *.lst and grep __zero_ *.lst over my listfiles
> und luckily my code doesn't modify this register. 
> Guess my C-source is not too exotic:)
> So it would work for me right now (TM).

ATMega161 has a set of MUL instructions. They return the result in R0:R1.

> > Don't ;)
> it shurely is not wise to switch saving and restoring off,
> without knowing when the compiler inserts it, but...

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

Tlf.: 92648923

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