Re: [FFmpeg-devel] [PATCH 02/15] avfilter/vf_bwdif: Add common macros and consts for aarch64 neon

[John Cox <jc@kynesim.co.uk>]

On Sun, 2 Jul 2023 00:35:14 +0300 (EEST), you wrote:

>On Thu, 29 Jun 2023, John Cox wrote:
>
>> Add macros for dual scalar half->single multiply and accumulate
>> Add macro for shift, saturate and shorten single to byte
>> Add filter constants
>>
>> Signed-off-by: John Cox <jc@kynesim.co.uk>
>> ---
>> libavfilter/aarch64/vf_bwdif_neon.S | 46 +++++++++++++++++++++++++++++
>> 1 file changed, 46 insertions(+)
>>
>> diff --git a/libavfilter/aarch64/vf_bwdif_neon.S b/libavfilter/aarch64/vf_bwdif_neon.S
>> index 639ab22998..a8f0ed525a 100644
>> --- a/libavfilter/aarch64/vf_bwdif_neon.S
>> +++ b/libavfilter/aarch64/vf_bwdif_neon.S
>> @@ -23,3 +23,49 @@
>>
>> #include "libavutil/aarch64/asm.S"
>>
>> +.macro SQSHRUNN b, s0, s1, s2, s3, n
>> +        sqshrun         \s0\().4h, \s0\().4s, #\n - 8
>> +        sqshrun2        \s0\().8h, \s1\().4s, #\n - 8
>> +        sqshrun         \s1\().4h, \s2\().4s, #\n - 8
>> +        sqshrun2        \s1\().8h, \s3\().4s, #\n - 8
>> +        uzp2            \b\().16b, \s0\().16b, \s1\().16b
>> +.endm
>> +
>> +.macro SMULL4K a0, a1, a2, a3, s0, s1, k
>> +        smull           \a0\().4s, \s0\().4h, \k
>> +        smull2          \a1\().4s, \s0\().8h, \k
>> +        smull           \a2\().4s, \s1\().4h, \k
>> +        smull2          \a3\().4s, \s1\().8h, \k
>> +.endm
>> +
>> +.macro UMULL4K a0, a1, a2, a3, s0, s1, k
>> +        umull           \a0\().4s, \s0\().4h, \k
>> +        umull2          \a1\().4s, \s0\().8h, \k
>> +        umull           \a2\().4s, \s1\().4h, \k
>> +        umull2          \a3\().4s, \s1\().8h, \k
>> +.endm
>> +
>> +.macro UMLAL4K a0, a1, a2, a3, s0, s1, k
>> +        umlal           \a0\().4s, \s0\().4h, \k
>> +        umlal2          \a1\().4s, \s0\().8h, \k
>> +        umlal           \a2\().4s, \s1\().4h, \k
>> +        umlal2          \a3\().4s, \s1\().8h, \k
>> +.endm
>> +
>> +.macro UMLSL4K a0, a1, a2, a3, s0, s1, k
>> +        umlsl           \a0\().4s, \s0\().4h, \k
>> +        umlsl2          \a1\().4s, \s0\().8h, \k
>> +        umlsl           \a2\().4s, \s1\().4h, \k
>> +        umlsl2          \a3\().4s, \s1\().8h, \k
>> +.endm
>> +
>> +// static const uint16_t coef_lf[2] = { 4309, 213 };
>> +// static const uint16_t coef_hf[3] = { 5570, 3801, 1016 };
>> +// static const uint16_t coef_sp[2] = { 5077, 981 };
>> +
>> +        .align 16
>
>Note that .align for arm is power of two; this triggers a 2^16 byte 
>alignment here, which certainly isn't intended.

Yikes! I'll swap that for a .balign now I've looked that up

>But in general, the usual way of defining constants is with a 
>const/endconst block, which places them in the right rdata section instead 
>of in the text section. But that then requires you to use a movrel macro 
>for accessing the data, instead of a plain ldr instruction.

Yeah - arm has a history of mixing text & const - I went with the
simpler code. Is this a deal breaker or can I leave it as is?

JC

>> +coeffs:
>> +        .hword          4309 * 4, 213 * 4               // lf[0]*4 = v0.h[0]
>> +        .hword          5570, 3801, 1016, -3801         // hf[0] = v0.h[2], -hf[1] = v0.h[5]
>> +        .hword          5077, 981                       // sp[0] = v0.h[6]
>> +
>> --
>
>
>// Martin
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