[oe] [PATCH/RFC] qt4-embedded: tune QT_ARCH for armv6

[Khem Raj]

On Thu, Nov 4, 2010 at 11:26 AM, Holger Freyther <holger+oe at freyther.de> wrote:
> On 11/04/2010 10:52 AM, Eric Bénard wrote:
>> this is a RFC, I think it can also be used on qt 4.6.x and on armv7.
>> Setting QT_ARCH to armv6 enable some asm optimized functions in QT.
>
> Do you know the consequences of this change? E.g. in the painting
> engine unaligned memory access will be allowed. I am not sure that Nokia has
> ever benchmarked what is faster (aligned/unaligned) access. So it would be
> very interesting to know the perf difference. E.g. use qttracereply to measure it.
>
> Phil do you happen to know why unaligned access got allowed starting from
> armv6? How fast will it be?
>

The instructions can cope with unaligned data so the performance will
not be impacted but its only upto
32-bit data above that the fault will still be generated and not all
instructions can operate on unaligned data
only ones operating on 32-bit data can do it.

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