Re: [FFmpeg-devel] [PATCH 1/2] avcodec/vvc: Remove NOP condition check in alf_filter_luma

[Zhao Zhili <quinkblack@foxmail.com>]

> On Jul 16, 2024, at 20:31, Nuo Mi <nuomi2021@gmail.com> wrote:
> 
> On Tue, Jul 16, 2024 at 10:50 AM Zhao Zhili <quinkblack@foxmail.com <mailto:quinkblack@foxmail.com>> wrote:
> 
>> From: Zhao Zhili <zhilizhao@tencent.com <mailto:zhilizhao@tencent.com>>
>> 
>> If (y + i == vb_above) or (y + i == vb_below), the if body has no
>> operation.
>> 
> 👍, How did you find this? From a compiler warning or by reading the code?

There is compiler warning. I found this issue when trying to simplify the logic
before rewrite in ARM assembly.

> 
> 
>> ---
>> libavcodec/vvc/filter_template.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/libavcodec/vvc/filter_template.c
>> b/libavcodec/vvc/filter_template.c
>> index 9b3a0e46f7..32777452b7 100644
>> --- a/libavcodec/vvc/filter_template.c
>> +++ b/libavcodec/vvc/filter_template.c
>> @@ -77,7 +77,7 @@ static void FUNC(alf_filter_luma)(uint8_t *_dst,
>> ptrdiff_t dst_stride, const uin
>>                 const int is_near_vb_below = (y + i >= vb_pos) && (y + i
>> <= vb_pos);
>>                 const int is_near_vb = is_near_vb_above ||
>> is_near_vb_below;
>> 
>> -                if ((y + i < vb_pos) && ((y + i) >= vb_above)) {
>> +                if ((y + i < vb_pos) && ((y + i) > vb_above)) {
>>                     p1 = (y + i == vb_pos - 1) ? p0 : p1;
>>                     p3 = (y + i >= vb_pos - 2) ? p1 : p3;
>>                     p5 = (y + i >= vb_pos - 3) ? p3 : p5;
>> @@ -85,7 +85,7 @@ static void FUNC(alf_filter_luma)(uint8_t *_dst,
>> ptrdiff_t dst_stride, const uin
>>                     p2 = (y + i == vb_pos - 1) ? p0 : p2;
>>                     p4 = (y + i >= vb_pos - 2) ? p2 : p4;
>>                     p6 = (y + i >= vb_pos - 3) ? p4 : p6;
>> -                } else if ((y + i >= vb_pos) && ((y + i) <= vb_below)) {
>> +                } else if ((y + i >= vb_pos) && ((y + i) < vb_below)) {
>>                     p2 = (y + i == vb_pos    ) ? p0 : p2;
>>                     p4 = (y + i <= vb_pos + 1) ? p2 : p4;
>>                     p6 = (y + i <= vb_pos + 2) ? p4 : p6;
>> --
>> 2.42.0
>> 
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