Before and after:
A78
ac3_sum_square_bufferfly_int32_neon: 484.8 ( 2.00x)
ac3_sum_square_bufferfly_int32_neon: 468.2 ( 2.08x)
A72
ac3_sum_square_bufferfly_int32_neon: 793.6 ( 1.26x)
ac3_sum_square_bufferfly_int32_neon: 527.3 ( 1.92x)
---
Instead of calculating a^2, b^2, (a+b)^2 and (a-b)^2, calculate only
a^2, b^2 and 2*a*b in each iteration and derive the latter parts from
these three at the end.
Krzysztof
libavcodec/aarch64/ac3dsp_neon.S | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/libavcodec/aarch64/ac3dsp_neon.S b/libavcodec/aarch64/ac3dsp_neon.S
index b2ac9edc55..2128eab528 100644
--- a/libavcodec/aarch64/ac3dsp_neon.S
+++ b/libavcodec/aarch64/ac3dsp_neon.S
@@ -80,21 +80,20 @@ function ff_ac3_sum_square_butterfly_int32_neon, export=1
movi v0.2d, #0
movi v1.2d, #0
movi v2.2d, #0
- movi v3.2d, #0
1: ld1 {v4.2s}, [x1], #8
ld1 {v5.2s}, [x2], #8
- add v6.2s, v4.2s, v5.2s
- sub v7.2s, v4.2s, v5.2s
- smlal v0.2d, v4.2s, v4.2s
- smlal v1.2d, v5.2s, v5.2s
- smlal v2.2d, v6.2s, v6.2s
- smlal v3.2d, v7.2s, v7.2s
subs w3, w3, #2
+ smlal v0.2d, v4.2s, v4.2s // sum of a^2
+ smlal v1.2d, v5.2s, v5.2s // sum of b^2
+ sqdmlal v2.2d, v4.2s, v5.2s // sum of 2ab
b.gt 1b
addp d0, v0.2d
addp d1, v1.2d
addp d2, v2.2d
- addp d3, v3.2d
+ sub d3, d0, d2 // a^2 + b^2 - 2ab
+ add d2, d0, d2
+ add d3, d3, d1 // a^2 + b^2 + 2ab
+ add d2, d2, d1
st1 {v0.1d-v3.1d}, [x0]
ret
endfunc
--
2.47.2
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