Re: i seem to have hit a problem with my new conflict finder.

["Vladimir N. Makarov" <vmakarov at redhat dot com>]

Kenneth Zadeck wrote:

> Andrew MacLeod wrote:
>  
>
> > On Fri, 2007-08-17 at 12:01 -0400, Kenneth Zadeck wrote:
> >
> >  
> >    
> >
> > > > In any case IRA can not use UREC because UREC is needed before IRA
> > > > calculates reg class info and the reg class info is needed for
> > > > calculation of UREC.  If you manage to use LIVE instead of UREC, it
> > > > would permit to use LIVE also in IRA instead of LR.  But I can not say
> > > > can we use LIVE instead of UREC because I don't know the
> > > > df-infrastructure well yet.
> > > >
> > > >      
> > > >        
> > > we should talk.  I am avail today.  i am leaving on vacation tomorrow
> > > for a week.
> > >
> > > Even if this patch does not get in this round, you should consider it as
> > > a starting point for building the interference graph for ira.  
> > >
> > > it does not use urec and a big part of the patch is just getting rid of
> > > urec,  It does a backwards scan using the live at bottom set as the
> > > starting point for the scan.
> > > This is the most accurate you can get so there really is no reason not
> > > to use it since it is also no more expensive than any weaker technique. 
> > >    
> > >      
> > It is the standard way of doing things. Out-Of-SSA has always used live
> > range info from the bottom up for its conflict graph. I'm marginally
> > suprised it is calculated any other way...
> >
> > Andrew
> >
> >  
> >    
> this is gcc, get a life. 
>
> bottom up is the way i was taught when i was a small child playing with
> compilers with training wheels. 
>
>  
I think it came from Pastel compiler of Livermoore Laboratories and that 
stuff in Pastel compiler was written by Fred Chow who is a very good 
specialist in RA.

Simply it is an old stuff and that time the backward scan was not so 
common (as graph based coloring).

> Gcc always seemed weird because you need reg_dead and reg_unused notes. 
> Note that my patch does not use reg_dead or unused notes.
>