FreeLists / openbeos / [openbeos] Re: app_server: MMX/SSE help wanted

[Adi Oanca <adioanca@xxxxxxxxxxxxxx>]

Axel Dörfler wrote:
> Adi Oanca <e2joseph@xxxxxxxxxx> wrote:
>
> > > So from the SIMD coders perspective, it would be very good if Haiku 
> > > would 
> > > offer some control over data alignment for bitmap allocations.
> > > This includes not only the base address of the bitmap, but should 
> > > ideally 
> > > extend to each bitmap row, in cases where each row has to be 
> > > processed 
> > > separately (e.g. by blur routines:). 
> > >
> > > Of course there'd be some 'waste', but I don't think this would 
> > > matter too 
> > > much on modern systems. Binary compatibility shouldn't be a problem 
> > > either, 
> > > as the BeBook already says that BytesPerRow() are decisive on 
> > > determing a 
> > > bitmaps actual size.
> > >
> > > This might be implemented by an additional constructor without too 
> > > much 
> > > fuss, I'd guess. It would be great if you could implement this, as 
> > > this 
> > > would make SIMD coding much easier and less bug-prone.
> >
> > 	OK, you'll have that. Now, I have to see how. :-) Axel, can you 
> > help?
>
>
> What he means is: we would need a change of the public API, that is add 
> another BBitmap constructor that allows an alignment. What we could 
> also do is to add another bitmap flag to force an ideal alignment for 
> the current CPU.

	What I mean is: I don't know how to align data to 8 or 16 byte boundaries.
	The only way I can think of is a kernel/VM function telling me the physical memory address for a 
virtual one, so I can start writing bitmap data at multiple of 8/16 depending of what we're using 
MMX/SSE.


Adi.