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

["Martin Storsjö" <martin@martin.st>]

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.

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.

> +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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