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

[Zhao Zhili <quinkblack@foxmail.com>]

> On Jul 17, 2024, at 00:07, Zhao Zhili <quinkblack@foxmail.com> wrote:
> 
> 
> 
>> 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.

Oops, I mean there is “no" compiler warning.

> 
>> 
>> 
>>> ---
>>> 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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