[FFmpeg-devel] [PATCH] NEON: put_pixels_clamped

[Måns Rullgård]

David Conrad <lessen42 at gmail.com> writes:

> On Apr 16, 2009, at 4:23 PM, M?ns Rullg?rd wrote:
>
>> David Conrad <lessen42 at gmail.com> writes:
>>
>>> On Apr 16, 2009, at 3:44 PM, David Conrad wrote:
>>>
>>>> On Apr 16, 2009, at 3:32 PM, M?ns Rullg?rd wrote:
>>>>
>>>>> David Conrad <lessen42 at gmail.com> writes:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Apparently this is used for some wmv3 files in addition to the
>>>>>> signed variant.  < 1% faster decode.
>>>>>>
>>>>>>
>>>>>> diff --git a/libavcodec/arm/dsputil_neon_s.S b/libavcodec/arm/
>>>>>> dsputil_neon_s.S
>>>>>> index f16293d..159ee64 100644
>>>>>> --- a/libavcodec/arm/dsputil_neon_s.S
>>>>>> +++ b/libavcodec/arm/dsputil_neon_s.S
>>>>>> @@ -273,6 +273,30 @@ function ff_put_h264_qpel8_mc00_neon,
>>>>>> export=1
>>>>>>       pixfunc2 put_ pixels8_y2,   _no_rnd, vhadd.u8
>>>>>>       pixfunc2 put_ pixels8_xy2,  _no_rnd, vshrn.u16, 1
>>>>>>
>>>>>> +function ff_put_pixels_clamped_neon, export=1
>>>>>> +        vld1.64         {d16-d19}, [r0,:128]!
>>>>>> +        vqmovn.u16      d0, q8
>>>>>> +        vld1.64         {d20-d23}, [r0,:128]!
>>>>>> +        vqmovn.u16      d1, q9
>>>>>> +        vqmovn.u16      d2, q10
>>>>>> +        vld1.64         {d24-d27}, [r0,:128]!
>>>>>> +        vqmovn.u16      d3, q11
>>>>>> +        vqmovn.u16      d4, q12
>>>>>> +        vld1.64         {d28-d31}, [r0,:128]!
>>>>>> +        vqmovn.u16      d5, q13
>>>>>> +        vqmovn.u16      d6, q14
>>>>>> +        vst1.64         {d0},      [r1,:64], r2
>>>>>> +        vqmovn.u16      d7, q15
>>>>>> +        vst1.64         {d1},      [r1,:64], r2
>>>>>> +        vst1.64         {d2},      [r1,:64], r2
>>>>>> +        vst1.64         {d3},      [r1,:64], r2
>>>>>> +        vst1.64         {d4},      [r1,:64], r2
>>>>>> +        vst1.64         {d5},      [r1,:64], r2
>>>>>> +        vst1.64         {d6},      [r1,:64], r2
>>>>>> +        vst1.64         {d7},      [r1,:64], r2
>>>>>> +        bx              lr
>>>>>> +        .endfunc
>>>>>
>>>>> Shouldn't those be vqmovun.s16?  I'd also try to interleave them
>>>>> with the loads and stores a bit more for better dual-issue
>>>>> opportunities.
>>>>
>>>> Unsigned pixels; MMX does the same (packuswb for put_pixels_clamped
>>>> vs. packsswb for put_signed_pixels_clamped)
>>>
>>> Oops, you're right, I didn't read packuswb. New patch attached.
>>>
>>>> Also, the loads take two issue cycles since they're loading 4
>>>> registers; shouldn't they be able to dual issue on both cycles?
>>
>> On Cortex-A8 NEON instructions with more than one issue cycle can
>> dual-issue on the first or the last cycle but not both.
>
> As discussed on IRC, all the multicycle NEON instructions I've checked
> can dual issue on both their first and last cycles.

My mistake.

> I can't measure any speed difference doing it this way, but it looks a
> bit more consistent with the other put_/add_ pixels_clamped.

OK.

-- 
M?ns Rullg?rd
mans at mansr.com