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DragASprite_Start (ARMv7)

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  DragASprite_Start (ARMv7) Ian Hamilton <Ian.Hamilton@AAUG.net> - 2011-11-30 11:19 +0000
    Re: DragASprite_Start (ARMv7) Martin Wuerthner <spamtrap@mw-software.com> - 2011-11-30 14:09 +0100
      Re: DragASprite_Start (ARMv7) Ian Hamilton <Ian.Hamilton@AAUG.net> - 2011-11-30 13:22 +0000

#1108 — DragASprite_Start (ARMv7)

What limitations are there for DragASprite_Start under ARMv7? Which
elements need to be word aligned?

-- 
Ian Hamilton (Iyonix/ARMini) http://www.hamiltoni.pwp.blueyonder.co.uk/

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#1110

In message <523a3825deIan.Hamilton@AAUG.Net>
          Ian Hamilton <Ian.Hamilton@AAUG.net> wrote:

> What limitations are there for DragASprite_Start under ARMv7? Which
> elements need to be word aligned?

I am not aware of any API differences caused by ARMv7. Unless stated 
otherwise, all pointers to word sized fields or structures that 
contain word sized fields at word aligned offsets need to be word 
aligned on entry to any RISC OS SWI on any processor.

ARMv7 does not make any difference. Earlier processors could not read 
a word sized field from an unaligned address using a single load 
instruction either, so it never made sense to have unaligned pointers 
to word sized fields.

-- 
Martin
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Martin Wuerthner         MW Software      http://www.mw-software.com/
        RISC OS Software for Design, Printing and Publishing
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#1111

In article <6b3a423a52.martin@bach.planiverse.com>,
   Martin Wuerthner <spamtrap@mw-software.com> wrote:
> In message <523a3825deIan.Hamilton@AAUG.Net>
>           Ian Hamilton <Ian.Hamilton@AAUG.net> wrote:

> > What limitations are there for DragASprite_Start under ARMv7? Which
> > elements need to be word aligned?

> I am not aware of any API differences caused by ARMv7. Unless stated 
> otherwise, all pointers to word sized fields or structures that 
> contain word sized fields at word aligned offsets need to be word 
> aligned on entry to any RISC OS SWI on any processor.

> ARMv7 does not make any difference. Earlier processors could not read 
> a word sized field from an unaligned address using a single load 
> instruction either, so it never made sense to have unaligned pointers 
> to word sized fields.

I've just discovered the cause of the problem. I'm using Mode 28 sprites
and it was crashing on some drags but not others. I initially thought it
might be related to word alignment. 

It turns out a few of the sprites had palettes and it's dragging those
which crash. I've removed the palettes and the problem appears to be
resolved. 

Ian

-- 
Ian Hamilton (Iyonix/ARMini) http://www.hamiltoni.pwp.blueyonder.co.uk/

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