Re: [Qemu-devel] QEMU state of ARM NEON support.

[Juha.Riihimaki]

On Mar 25, 2010, at 12:27, ext Dmitry Zhurikhin wrote:

> address@hidden wrote:
>> - vqdmlsl yields different results for some specific input values, however I 
>> think QEMU is producing correct results. For example, 
>> 1431655765-(2*-32768*-32768)=-715827883 but your reference hardware results 
>> say it should be -715827882.
> From what I understand hardware gets such result because saturation occurs on 
> the (2*-32768*-32768) step.  The result is not 0x80000000 as expected but 
> because of overflow is set as the largest 32-bit signed integer 0x7FFFFFFF.  
> It 
> seems that QEMU just doesn't perform saturation (in this particular case at 
> least).

Yes I see, I overlooked the fact that -32768*-32768 changes the sign and so 
doubling the result of that overflows the signed 32-bit integer even if the 
result still fits in 32 bits. Thanks, I'll fix that as well.


Regards,
Juha