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Re: powerpc & unaligned block moves with fp registers




--On Friday, November 09, 2001 09:52:29 AM -0500 David Edelsohn 
<dje@watson.ibm.com> wrote:

>>>>>> Mark Mitchell writes:
>
> Mark> I would prefer to see GCC just ask the back end "How do you want to
> Mark> perform a memory-to-memory copy of thus and such many bits, knowing
> Mark> thus and such about the current alignment of the memory?"
>
> 	And I consider BLKmode move (movstrsi, etc.) the way to do that.
> It already provides an alignment and number of bytes.  On PowerPC, BLKmove
> chooses the most efficient method, including using DImode.

Yes, I think BLKmode is a fine way to implement the interface.

> 	One could call BLKmode move always, but my model was using
> SLOW_UNALIGNED_ACCESS to determine when the backend considred things
> "complicated" or "non-obvious" that the common code should punt to BLKmode
> move.

This would certainly work, but I think it would be nicer to just always
use BLKmode and have the back ends call back to a common routine if they
want command handling.  I would like the middle end/back end interface
to be small, and then provide a library of common routines that back
ends could use.

That's just my bias on the design; there's nothing terribly magic
about it.

-- 
Mark Mitchell                mark@codesourcery.com
CodeSourcery, LLC            http://www.codesourcery.com


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