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

[Vladimir N. Makarov]

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.
>  
>