On Tue, 16 Aug 2022, Hubert Mazur wrote:
Provide optimized implementation of pix_abs16_y2 function for arm64.
Performance comparison tests are shown below.
pix_abs_0_2_c: 317.2
pix_abs_0_2_neon: 37.5
Benchmarks and tests run with checkasm tool on AWS Graviton 3.
Signed-off-by: Hubert Mazur <h...@semihalf.com>
---
libavcodec/aarch64/me_cmp_init_aarch64.c | 3 +
libavcodec/aarch64/me_cmp_neon.S | 75 ++++++++++++++++++++++++
2 files changed, 78 insertions(+)
diff --git a/libavcodec/aarch64/me_cmp_init_aarch64.c
b/libavcodec/aarch64/me_cmp_init_aarch64.c
index 955592625a..1c36d3d7cb 100644
--- a/libavcodec/aarch64/me_cmp_init_aarch64.c
+++ b/libavcodec/aarch64/me_cmp_init_aarch64.c
@@ -29,6 +29,8 @@ int ff_pix_abs16_xy2_neon(MpegEncContext *s, const uint8_t
*blk1, const uint8_t
ptrdiff_t stride, int h);
int ff_pix_abs16_x2_neon(MpegEncContext *v, const uint8_t *pix1, const uint8_t
*pix2,
ptrdiff_t stride, int h);
+int ff_pix_abs16_y2_neon(MpegEncContext *v, const uint8_t *pix1, const uint8_t
*pix2,
+ ptrdiff_t stride, int h);
Misaligned function declaration.
diff --git a/libavcodec/aarch64/me_cmp_neon.S b/libavcodec/aarch64/me_cmp_neon.S
index 367924b3c2..0ec9c0465b 100644
--- a/libavcodec/aarch64/me_cmp_neon.S
+++ b/libavcodec/aarch64/me_cmp_neon.S
@@ -404,3 +404,78 @@ function sse4_neon, export=1
ret
endfunc
+
+function ff_pix_abs16_y2_neon, export=1
Why place this new function at the bottom of the file, instead of
logically following the other preexisting pix_abs16 function? In the
version I pushed, I moved it further up
+ // x0 unused
+ // x1 uint8_t *pix1
+ // x2 uint8_t *pix2
+ // x3 ptrdiff_t stride
+ // x4 int h
This should be w4. You had fixed this in a couple patches, but missed this
one.
+
+ // initialize buffers
+ movi v29.8h, #0 // clear the
accumulator
+ movi v28.8h, #0 // clear the
accumulator
+ movi d18, #0
Unused d18 here too
+ add x5, x2, x3 // pix2 + stride
+ cmp w4, #4
+ b.lt 2f
+
+// make 4 iterations at once
+1:
+
+ // abs(pix1[0], avg2(pix2[0], pix2[0 + stride]))
+ // avg2(a, b) = (((a) + (b) + 1) >> 1)
+ // abs(x) = (x < 0 ? (-x) : (x))
+
+ ld1 {v1.16b}, [x2], x3 // Load pix2 for first
iteration
+ ld1 {v2.16b}, [x5], x3 // Load pix3 for first
iteration
+ urhadd v30.16b, v1.16b, v2.16b // Rounding halving
add, first iteration
+ ld1 {v0.16b}, [x1], x3 // Load pix1 for first
iteration
+ uabal v29.8h, v0.8b, v30.8b // Absolute difference
of lower half, first iteration
This whole first sequence is almost entirely blocking, waiting for the
result of the previous operation - did you miss to interleave this with
the rest of the operations?
Normally I wouldn't bother with minor interleaving details, but here the
impact was rather big. I manually reinterleaved the whole function, and
got this speedup:
Before: Cortex A53 A72 A73
pix_abs_0_2_neon: 153.0 63.7 52.7
After:
pix_abs_0_2_neon: 141.0 61.7 51.7
// Martin
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