On Sun, Aug 23, 2015 at 5:28 PM, Clément Bœsch <u...@pkh.me> wrote:
> On Sun, Aug 23, 2015 at 11:23:54PM +0200, Clément Bœsch wrote:
>> On Sun, Aug 23, 2015 at 11:58:23AM -0400, Ganesh Ajjanagadde wrote:
>> [...]
>> > diff --git a/libavfilter/vf_hqx.c b/libavfilter/vf_hqx.c
>> > index fa15d9c..0178793 100644
>> > --- a/libavfilter/vf_hqx.c
>> > +++ b/libavfilter/vf_hqx.c
>> > @@ -65,9 +65,9 @@ static av_always_inline int yuv_diff(uint32_t yuv1,
>> > uint32_t yuv2)
>> > #define YMASK 0xff0000
>> > #define UMASK 0x00ff00
>> > #define VMASK 0x0000ff
>> > - return abs((yuv1 & YMASK) - (yuv2 & YMASK)) > (48 << 16) ||
>> > - abs((yuv1 & UMASK) - (yuv2 & UMASK)) > ( 7 << 8) ||
>> > - abs((yuv1 & VMASK) - (yuv2 & VMASK)) > ( 6 << 0);
>> > + return FFUABSDIFF(yuv1 & YMASK, yuv2 & YMASK) > (48 << 16) ||
>> > + FFUABSDIFF(yuv1 & UMASK, yuv2 & UMASK) > ( 7 << 8) ||
>> > + FFUABSDIFF(yuv1 & VMASK, yuv2 & VMASK) > ( 6 << 0);
>>
>> This is one of the bottleneck function of the filter. How does it affect
>> speed? Can you compare the generated ASM?
>>
>
> To answer my second question:
>
> [/tmp]☭ cat a.c
> #include <stdlib.h>
> #include <stdint.h>
>
> #define YMASK 0xff0000
> #define UMASK 0x00ff00
> #define VMASK 0x0000ff
>
> #define FFUABSDIFF(a,b) (((a) > (b)) ? ((a)-(b)) : ((b)-(a)))
>
> int yuv_diff_0(uint32_t yuv1, uint32_t yuv2)
> {
> return abs((yuv1 & YMASK) - (yuv2 & YMASK)) > (48 << 16) ||
> abs((yuv1 & UMASK) - (yuv2 & UMASK)) > ( 7 << 8) ||
> abs((yuv1 & VMASK) - (yuv2 & VMASK)) > ( 6 << 0);
> }
>
> int yuv_diff_1(uint32_t yuv1, uint32_t yuv2)
> {
> return FFUABSDIFF(yuv1 & YMASK, yuv2 & YMASK) > (48 << 16) ||
> FFUABSDIFF(yuv1 & UMASK, yuv2 & UMASK) > ( 7 << 8) ||
> FFUABSDIFF(yuv1 & VMASK, yuv2 & VMASK) > ( 6 << 0);
> }
> [/tmp]☭ gcc -Wall -O2 -c a.c && objdump -d -Mintel a.o
>
> a.o: file format elf64-x86-64
>
>
> Disassembly of section .text:
>
> 0000000000000000 <yuv_diff_0>:
> 0: 89 f8 mov eax,edi
> 2: 89 f2 mov edx,esi
> 4: 81 e2 00 00 ff 00 and edx,0xff0000
> a: 25 00 00 ff 00 and eax,0xff0000
> f: 29 d0 sub eax,edx
> 11: 99 cdq
> 12: 31 d0 xor eax,edx
> 14: 29 d0 sub eax,edx
> 16: 89 c2 mov edx,eax
> 18: b8 01 00 00 00 mov eax,0x1
> 1d: 81 fa 00 00 30 00 cmp edx,0x300000
> 23: 7f 3e jg 63 <yuv_diff_0+0x63>
> 25: 89 fa mov edx,edi
> 27: 89 f1 mov ecx,esi
> 29: 81 e1 00 ff 00 00 and ecx,0xff00
> 2f: 81 e2 00 ff 00 00 and edx,0xff00
> 35: 29 ca sub edx,ecx
> 37: 89 d1 mov ecx,edx
> 39: c1 f9 1f sar ecx,0x1f
> 3c: 31 ca xor edx,ecx
> 3e: 29 ca sub edx,ecx
> 40: 81 fa 00 07 00 00 cmp edx,0x700
> 46: 7f 1b jg 63 <yuv_diff_0+0x63>
> 48: 40 0f b6 ff movzx edi,dil
> 4c: 40 0f b6 f6 movzx esi,sil
> 50: 29 f7 sub edi,esi
> 52: 89 f8 mov eax,edi
> 54: c1 f8 1f sar eax,0x1f
> 57: 31 c7 xor edi,eax
> 59: 29 c7 sub edi,eax
> 5b: 31 c0 xor eax,eax
> 5d: 83 ff 06 cmp edi,0x6
> 60: 0f 9f c0 setg al
> 63: f3 c3 repz ret
> 65: 90 nop
> 66: 66 2e 0f 1f 84 00 00 nop WORD PTR cs:[rax+rax*1+0x0]
> 6d: 00 00 00
>
> 0000000000000070 <yuv_diff_1>:
> 70: 89 fa mov edx,edi
> 72: 89 f0 mov eax,esi
> 74: 81 e2 00 00 ff 00 and edx,0xff0000
> 7a: 25 00 00 ff 00 and eax,0xff0000
> 7f: 39 c2 cmp edx,eax
> 81: 76 4d jbe d0 <yuv_diff_1+0x60>
> 83: 29 c2 sub edx,eax
> 85: b8 01 00 00 00 mov eax,0x1
> 8a: 81 fa 00 00 30 00 cmp edx,0x300000
> 90: 77 7e ja 110 <yuv_diff_1+0xa0>
> 92: 89 fa mov edx,edi
> 94: 89 f0 mov eax,esi
> 96: 81 e2 00 ff 00 00 and edx,0xff00
> 9c: 25 00 ff 00 00 and eax,0xff00
> a1: 39 c2 cmp edx,eax
> a3: 76 43 jbe e8 <yuv_diff_1+0x78>
> a5: 29 c2 sub edx,eax
> a7: b8 01 00 00 00 mov eax,0x1
> ac: 81 fa 00 07 00 00 cmp edx,0x700
> b2: 77 74 ja 128 <yuv_diff_1+0xb8>
> b4: 40 0f b6 ff movzx edi,dil
> b8: 40 0f b6 f6 movzx esi,sil
> bc: 39 f7 cmp edi,esi
> be: 76 58 jbe 118 <yuv_diff_1+0xa8>
> c0: 29 f7 sub edi,esi
> c2: 31 c0 xor eax,eax
> c4: 83 ff 06 cmp edi,0x6
> c7: 0f 97 c0 seta al
> ca: c3 ret
> cb: 0f 1f 44 00 00 nop DWORD PTR [rax+rax*1+0x0]
> d0: 29 d0 sub eax,edx
> d2: 89 c2 mov edx,eax
> d4: b8 01 00 00 00 mov eax,0x1
> d9: 81 fa 00 00 30 00 cmp edx,0x300000
> df: 76 b1 jbe 92 <yuv_diff_1+0x22>
> e1: f3 c3 repz ret
> e3: 0f 1f 44 00 00 nop DWORD PTR [rax+rax*1+0x0]
> e8: 29 d0 sub eax,edx
> ea: 89 c2 mov edx,eax
> ec: b8 01 00 00 00 mov eax,0x1
> f1: 81 fa 00 07 00 00 cmp edx,0x700
> f7: 77 e8 ja e1 <yuv_diff_1+0x71>
> f9: 40 0f b6 ff movzx edi,dil
> fd: 40 0f b6 f6 movzx esi,sil
> 101: 39 f7 cmp edi,esi
> 103: 76 13 jbe 118 <yuv_diff_1+0xa8>
> 105: eb b9 jmp c0 <yuv_diff_1+0x50>
> 107: 66 0f 1f 84 00 00 00 nop WORD PTR [rax+rax*1+0x0]
> 10e: 00 00
> 110: f3 c3 repz ret
> 112: 66 0f 1f 44 00 00 nop WORD PTR [rax+rax*1+0x0]
> 118: 29 fe sub esi,edi
> 11a: 31 c0 xor eax,eax
> 11c: 83 fe 06 cmp esi,0x6
> 11f: 0f 97 c0 seta al
> 122: c3 ret
> 123: 0f 1f 44 00 00 nop DWORD PTR [rax+rax*1+0x0]
> 128: f3 c3 repz ret
> [/tmp]☭
>
> I must say I'm slightly uncomfortable with that change.
I don't know much assembly at the moment, can you please explain the difference
and what makes you uncomfortable?
>
> --
> Clément B.
>
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