Re: [avr-gcc-list] testsuite saga continues

[Andrew Hutchinson]

I believe the issue with cc0 is that you would have to create parallel 
compare expression for all operation that set status. Otherwise, gcc 
would try and insert redundant compare instructions before every 
conditional jump.  This parallel RTL is likely to mess up other things - 
like optimization.

So I would not worry about it until some of the other targets have shown 
it to work effectively.
To be honest we don't see to many problems in this code for avr. So the 
reward is small.

Andy


Weddington, Eric wrote:
>  
>
>   
> > -----Original Message-----
> > From: 
> > address@hidden 
> > [mailto:address@hidden
> > org] On Behalf Of Andrew Hutchinson
> > Sent: Wednesday, January 30, 2008 3:55 PM
> > To: Wouter van Gulik
> > Cc: address@hidden
> > Subject: Re: [avr-gcc-list] testsuite saga continues
> >
> > gcc uses its own status register cc0 that is set as a result of 
> > "compares" and operators such as EQ,LT,GT. 
> >     
>
> <snip>
>
>   
> > There has been some suggestion of changing gcc cc0 based 
> > system, But as 
> > yet, nobody has completely figured out a way of doing it.
> >
> >     
>
> See this page on the GCC web site:
> <http://gcc.gnu.org/projects/beginner.html>
> "This page lists projects which are feasible for people who aren't
> intimately familiar with GCC's internals. Many of them are things which
> would be extremely helpful if they got done, but the core team never
> seems to get around to them. "
>
> This page lists this item:
> "- Convert md files that use (cc0) so they don't anymore."
>
> And it give some suggestion on how to do it, but it also says that it
> would be difficult.
>
> The AVR is one of the ports that uses the cc0 system. It would be great
> if we could move to the new system eventually.
>
> Eric Weddington
>
>
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