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Re: [avr-gcc-list] cbr and negative numbers

From: Ruud Vlaming
Subject: Re: [avr-gcc-list] cbr and negative numbers
Date: Wed, 10 Sep 2008 22:20:50 +0200
User-agent: KMail/1.9.1

On Wednesday 10 September 2008 16:01, you wrote:
> > -----Original Message-----
> > However, if you activate the 8 bit integer option -mint8 
> Full halt.
> -mint8 is not really supported. Yes, we know it causes all sorts of 
> problems. It should never be used. I'd really like to see it ripped 
> out of the AVR port of GCC.  

Me too. I assume you will replace it by true eight bit arithmetic?

Since we don't live in an ideal world we have to stick with mint8 
for a while. If you care to complete reading my original post
you will see that this has nothing to with the usual complaints
about mint8, most of which i am aware of. The problem i am pointing
out can (easily) be solved by letting gcc emit only positive/hexadecimal 
operands or by a minimal change in the way the cbr instruction
calculates its operand: (0xFF-x) -> (0xFF - (x & 0xFF)).
If you do not care to read it to the end, well, in any case it is known
from know on, that you cannot use the cbr instruction reliably with mint8.


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