On Thu, 28 Apr 2022, J. Dekker wrote:

bench on AWS Graviton:

hevc_sao_edge_8x8_8_c: 516.0
hevc_sao_edge_8x8_8_neon: 81.0

Signed-off-by: J. Dekker <j...@itanimul.li>
---
libavcodec/aarch64/hevcdsp_init_aarch64.c |  3 ++
libavcodec/aarch64/hevcdsp_sao_neon.S     | 51 +++++++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/libavcodec/aarch64/hevcdsp_init_aarch64.c 
b/libavcodec/aarch64/hevcdsp_init_aarch64.c
index df521bb083..2002530266 100644
--- a/libavcodec/aarch64/hevcdsp_init_aarch64.c
+++ b/libavcodec/aarch64/hevcdsp_init_aarch64.c
@@ -59,6 +59,8 @@ void ff_hevc_sao_band_filter_8x8_8_neon(uint8_t *_dst, 
uint8_t *_src,
                                  int width, int height);
void ff_hevc_sao_edge_filter_16x16_8_neon(uint8_t *dst, uint8_t *src, ptrdiff_t 
stride_dst,
                                          int16_t *sao_offset_val, int eo, int 
width, int height);
+void ff_hevc_sao_edge_filter_8x8_8_neon(uint8_t *dst, uint8_t *src, ptrdiff_t 
stride_dst,
+                                          int16_t *sao_offset_val, int eo, int 
width, int height);

av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
{
@@ -80,6 +82,7 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, 
const int bit_depth)
        c->sao_band_filter[2]          =
        c->sao_band_filter[3]          =
        c->sao_band_filter[4]          = ff_hevc_sao_band_filter_8x8_8_neon;
+        c->sao_edge_filter[0]          = ff_hevc_sao_edge_filter_8x8_8_neon;
        c->sao_edge_filter[1]          =
        c->sao_edge_filter[2]          =
        c->sao_edge_filter[3]          =
diff --git a/libavcodec/aarch64/hevcdsp_sao_neon.S 
b/libavcodec/aarch64/hevcdsp_sao_neon.S
index 0315c479df..efd8112af4 100644
--- a/libavcodec/aarch64/hevcdsp_sao_neon.S
+++ b/libavcodec/aarch64/hevcdsp_sao_neon.S
@@ -140,3 +140,54 @@ function ff_hevc_sao_edge_filter_16x16_8_neon, export=1
        // no lines to filter
        ret
endfunc
+
+// ff_hevc_sao_edge_filter_8x8_8_neon(char *dst, char *src, ptrdiff stride_dst,
+//                                    int16 *sao_offset_val, int eo, int 
width, int height)
+function ff_hevc_sao_edge_filter_8x8_8_neon, export=1
+        adr             x7, .Lsao_edge_pos
+        ldr             w4, [x7, w4, uxtw #2]
+        ld1             {v3.8h}, [x3]
+        mov             v3.h[7], v3.h[0]
+        mov             v3.h[0], v3.h[1]
+        mov             v3.h[1], v3.h[2]
+        mov             v3.h[2], v3.h[7]
+        uzp2            v1.16b, v3.16b, v3.16b
+        uzp1            v0.16b, v3.16b, v3.16b
+        movi            v2.16b, #2
+        add             x16, x0, x2
+        lsl             x2,  x2, #1
+        mov             x15, #192
+        mov             x8,  x1
+        sub             x9,  x1, x4
+        add             x10, x1, x4
+        lsr             w17, w6, #1

Compared with the previously applied (and reverted) patch, here, you previously had "mov x17, #4". I guess that'd mean the function only ever produced 8 output rows, while it now uses the real height parameter? Was this change a no-op (height is always 8?) or was this another hidden bug in the previous implementation?

+1:      ld1             {v3.d}[0], [ x8], x15
+        ld1             {v4.d}[0], [ x9], x15
+        ld1             {v5.d}[0], [x10], x15
+        ld1             {v3.d}[1], [ x8], x15
+        ld1             {v4.d}[1], [ x9], x15
+        ld1             {v5.d}[1], [x10], x15
+        cmhi            v16.16b, v4.16b, v3.16b
+        cmhi            v17.16b, v3.16b, v4.16b
+        cmhi            v18.16b, v5.16b, v3.16b
+        cmhi            v19.16b, v3.16b, v5.16b
+        sub             v20.16b, v16.16b, v17.16b
+        sub             v21.16b, v18.16b, v19.16b
+        add             v20.16b, v20.16b, v21.16b
+        add             v20.16b, v20.16b, v2.16b
+        tbl             v16.16b, {v0.16b}, v20.16b
+        tbl             v17.16b, {v1.16b}, v20.16b
+        uxtl            v20.8h, v3.8b
+        uxtl2           v21.8h, v3.16b
+        zip1            v18.16b, v16.16b, v17.16b
+        zip2            v19.16b, v16.16b, v17.16b
+        sqadd           v20.8h, v18.8h, v20.8h
+        sqadd           v21.8h, v19.8h, v21.8h
+        sqxtun          v6.8b, v20.8h
+        sqxtun          v7.8b, v21.8h
+        st1             {v6.8b}, [ x0], x2
+        st1             {v7.8b}, [x16], x2
+        subs            x17, x17, #1

This could be "subs w6, w6, #2" and you wouldn't need the lsr instruction at all. And you could place the subs before the two st1 instructions to reduce latency between them a little. (The same thing goes for moving subs further away from the branch that uses its outcome in the previous patch too.) But as this is just a reapply of a previously committed and reverted patch, I guess it's fine this way too...

The patchset otherwise looks good to me, modulo the question about the difference to the previous patchset above.

// Martin

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