[FFmpeg-devel] [PATCH 3/3] ac3enc: add SIMD-optimized shifting functions for use with the fixed-point AC3 encoder

[Ronald S. Bultje]

Hi,

On Tue, Mar 8, 2011 at 2:38 PM, Justin Ruggles <justin.ruggles at gmail.com> wrote:
> On 03/08/2011 02:15 PM, Michael Niedermayer wrote:
>
>> On Tue, Mar 08, 2011 at 01:59:44PM -0500, Ronald S. Bultje wrote:
>>> Hi,
>>>
>>> On Tue, Mar 8, 2011 at 1:18 PM, Justin Ruggles <justin.ruggles at gmail.com> wrote:
>>>> +%macro AC3_LSHIFT_INT16 1
>>>> +cglobal ac3_lshift_int16_%1, 3,3,5, src, len, shift
>>>> + ? ?test ? shiftd, shiftd
>>>> + ? ?jz .end
>>>> + ? ?movd ? ? ? m0, shiftd
>>>> + ? ?ALIGN 8
>>>> +.loop:
>>>> + ? ?AC3_SHIFT_4MM srcq, psllw, m0
>>>> + ? ?sub ? ? ?lend, mmsize*2
>>>> + ? ?ja .loop
>>>
>>> If it's not a multiple of mmsize*2, this will loop forever. Making
>>> this jg (= signed) would fix that.
>>
>> really?
>> i want that CPU on which ja behaves liek that
>
>
> in testing, it did not cause an infinite loop. ?i think because ja also
> checks the carry flag?

Could be, then it's fine.

Ronald