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List:       kde-kimageshop
Subject:    Re: cpu detection
From:       Andre Gemuend <scroogie () scroogie ! de>
Date:       2012-10-31 9:12:26
Message-ID: 5090EB7A.60109 () scroogie ! de
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On 10/30/2012 11:49 PM, JL VT wrote:
> On Mon, Oct 29, 2012 at 9:18 AM, Dmitry Kazakov <dimula73@gmail.com> wrot=
e:
>> Well, the integer solution might be quite good idea for some of the
>> composite ops. When I investigated into the topic, I thought about it, b=
ut I
>> faced with two problems I had no idea how to solve it:
>>
>> 1) The sse instruction set does not have integer division instruction. S=
o it
>> will have to be workarounded somehow.
>> 2) Integer multiplication instructions change the size of the operands. I
>> didn't know how to solve it properly.
> Forgive me if I say something completely out of place, but if you mean
> you get out-of-bond errors with integer multiplication, there are MMX
> operations that solve the bound problem by clipping values.

Yes, for multiplication you use a biased keep-low 16 bit unsigned =

multiplication (there is no keep high unsigned version) and subsequent =

shifts. It does not change the size of the operands (though you need to =

use 16 bit anyway).

But the division is not so easy. You either cast to float and back or =

have to implement your own division algorithm.

Greetings
Andr=E9
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