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Re: What to do with new-ra for GCC 4.0


On Sun, 2005-01-16 at 22:09 +0100, Ulrich Weigand wrote:
> Bernd Schmidt wrote:
> 
> > I'm attaching a proof-of-concept patch, against a checkout from 
> > 20050106.  The main things this patch does
> >   * replace reload insn ordering using RELOAD_FOR_blah by dependencies
> >     automatically generated from the replacements
> >   * replace reload inheritance by a separate pass that is run on data
> >     collected by find_reloads
> >   * try to make inheritance powerful enough that many other random
> >     optimizations scattered across reload can be deleted (I hope that
> >     eventually, reload_cse_regs can go as well)
> 
> This is very nice!  I've tried the patch on s390; here's what I found
> until now ...
> 
> > The changes in genoutput.c are necessary to deal with the fact that some 
> > machine descriptions have output operands without a "=" constraint letter.
> 
> Wouldn't it be better to simply fix the backends?  Testing your patch
> revealed a bug in s390.md where I had a superfluous "=" ...
Agreed.  The backends really need to be fixed.  I'm pretty sure missing
a '=' can create incorrect code; I don't know offhand if a superflous
'=' could create incorrect code.


Jeff


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