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Re: SMS improvements branch


On Thu, Dec 09, 2004 at 09:45:41PM +0200, Mostafa Hagog wrote:
> 
>     6. Port tree data dependency analysis routines to the RTL level
>        so we can have better dependancy. (Future, Beyond 4.1)

Seems a reasonable alternative approach to the transmission of data
dependence information from GIMPLE to the RTL level.

However (the following is just a guess, I have no numbers ;-) at RTL
level, a data dependence analyzer would obtain less precise
information than at tree level, because the informations such as the
dimensions of arrays are lost.  There are solutions for each of the
problems that could occur during the data dependence analysis at RTL
level, and this is why I have said that it was just a guess.

> II. SMS related work :
>    1. Use of alias sets to remove memory dependencies. (DONE, for 4.1)
>    2. Remove register anti-dependencies. (DONE, for 4.1)
>    3. Add backtracking to the SMS. (DONE, for 4.1)
>    4. Consider register pressure in SMS. (Beyond 4.1)
> 

Sid-Ahmed-Ali Touati has pointed me to the following report by the
author of the SMS algorithm, that shows some drawbacks of the SMS
algorithm:

http://www.hpl.hp.com/techreports/2002/HPL-2002-239.html

but anyway, you're probably aware of this work.

Sebastian


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