This patch integrates so called double bufferring when we are loading
2 batch of elements at a time and then processing them in parallel. On the
moden arm processors especially Apple Silicon it gives a visible
benefit, for subsampled pixel processing it is especially nice because
it allows to read elements w/ 2 instructions and write with a single one
(especially visible on a platforms with slower memory like ios).
Including the previous patch in a stack on macbook pro m4 max rgb_to_yuv_half
in checkasm goes up 2x of the c version
---
libswscale/aarch64/input.S | 105 ++++++++++++++++++++++++++++---------
1 file changed, 80 insertions(+), 25 deletions(-)
diff --git a/libswscale/aarch64/input.S b/libswscale/aarch64/input.S
index d61f8b3dba..00aab26ce1 100644
--- a/libswscale/aarch64/input.S
+++ b/libswscale/aarch64/input.S
@@ -197,40 +197,94 @@ function ff_\fmt_rgb\()ToUV_half_neon, export=1
ldp w12, w13, [x6, #20] // w12: bu, w13: rv
ldp w14, w15, [x6, #28] // w14: gv, w15: bv
4:
- cmp w5, #8
rgb_set_uv_coeff half=1
- b.lt 2f
-1: // load 16 pixels and prefetch memory for the next block
+
+ cmp w5, #16
+ b.lt 2f // Go directly to scalar if <
16
+
+1:
.if \element == 3
- ld3 { v16.16b, v17.16b, v18.16b }, [x3], #48
- prfm pldl1strm, [x3, #48]
+ ld3 { v16.16b, v17.16b, v18.16b }, [x3], #48 // First 16
pixels
+ ld3 { v26.16b, v27.16b, v28.16b }, [x3], #48 // Second 16
pixels
+ prfm pldl1keep, [x3, #96]
.else
- ld4 { v16.16b, v17.16b, v18.16b, v19.16b }, [x3], #64
- prfm pldl1strm, [x3, #64]
+ ld4 { v16.16b, v17.16b, v18.16b, v19.16b }, [x3], #64 //
First 16 pixels
+ ld4 { v26.16b, v27.16b, v28.16b, v29.16b }, [x3], #64 //
Second 16 pixels
+ prfm pldl1keep, [x3, #128]
.endif
-
+
+ // **Sum adjacent pixel pairs**
.if \alpha_first
- uaddlp v21.8h, v19.16b // v21: summed b pairs
- uaddlp v20.8h, v18.16b // v20: summed g pairs
- uaddlp v19.8h, v17.16b // v19: summed r pairs
+ uaddlp v21.8h, v19.16b // Block 1: B sums
+ uaddlp v20.8h, v18.16b // Block 1: G sums
+ uaddlp v19.8h, v17.16b // Block 1: R sums
+ uaddlp v31.8h, v29.16b // Block 2: B sums
+ uaddlp v30.8h, v28.16b // Block 2: G sums
+ uaddlp v29.8h, v27.16b // Block 2: R sums
.else
- uaddlp v19.8h, v16.16b // v19: summed r pairs
- uaddlp v20.8h, v17.16b // v20: summed g pairs
- uaddlp v21.8h, v18.16b // v21: summed b pairs
+ uaddlp v19.8h, v16.16b // Block 1: R sums
+ uaddlp v20.8h, v17.16b // Block 1: G sums
+ uaddlp v21.8h, v18.16b // Block 1: B sums
+ uaddlp v29.8h, v26.16b // Block 2: R sums
+ uaddlp v30.8h, v27.16b // Block 2: G sums
+ uaddlp v31.8h, v28.16b // Block 2: B sums
.endif
- mov v22.16b, v6.16b // U first half
- mov v23.16b, v6.16b // U second half
- mov v24.16b, v6.16b // V first half
- mov v25.16b, v6.16b // V second half
+ // init accumulatos for both blocks
+ mov v7.16b, v6.16b // U_low
+ mov v8.16b, v6.16b // U_high
+ mov v9.16b, v6.16b // V_low
+ mov v10.16b, v6.16b // V_high
+ mov v11.16b, v6.16b // U_low
+ mov v12.16b, v6.16b // U_high
+ mov v13.16b, v6.16b // V_low
+ mov v14.16b, v6.16b // V_high
+
+ smlal v7.4s, v0.4h, v19.4h // U += ru * r (0-3)
+ smlal v9.4s, v3.4h, v19.4h // V += rv * r (0-3)
+ smlal v11.4s, v0.4h, v29.4h // U += ru * r (0-3)
+ smlal v13.4s, v3.4h, v29.4h // V += rv * r (0-3)
+
+ smlal2 v8.4s, v0.8h, v19.8h // U += ru * r (4-7)
+ smlal2 v10.4s, v3.8h, v19.8h // V += rv * r (4-7)
+ smlal2 v12.4s, v0.8h, v29.8h // U += ru * r (4-7)
+ smlal2 v14.4s, v3.8h, v29.8h // V += rv * r (4-7)
+
+ smlal v7.4s, v1.4h, v20.4h // U += gu * g (0-3)
+ smlal v9.4s, v4.4h, v20.4h // V += gv * g (0-3)
+ smlal v11.4s, v1.4h, v30.4h // U += gu * g (0-3)
+ smlal v13.4s, v4.4h, v30.4h // V += gv * g (0-3)
+
+ smlal2 v8.4s, v1.8h, v20.8h // U += gu * g (4-7)
+ smlal2 v10.4s, v4.8h, v20.8h // V += gv * g (4-7)
+ smlal2 v12.4s, v1.8h, v30.8h // U += gu * g (4-7)
+ smlal2 v14.4s, v4.8h, v30.8h // V += gv * g (4-7)
+
+ smlal v7.4s, v2.4h, v21.4h // U += bu * b (0-3)
+ smlal v9.4s, v5.4h, v21.4h // V += bv * b (0-3)
+ smlal v11.4s, v2.4h, v31.4h // U += bu * b (0-3)
+ smlal v13.4s, v5.4h, v31.4h // V += bv * b (0-3)
+
+ smlal2 v8.4s, v2.8h, v21.8h // U += bu * b (4-7)
+ smlal2 v10.4s, v5.8h, v21.8h // V += bv * b (4-7)
+ smlal2 v12.4s, v2.8h, v31.8h // U += bu * b (4-7)
+ smlal2 v14.4s, v5.8h, v31.8h // V += bv * b (4-7)
+
+ sqshrn v16.4h, v7.4s, #10 // U (0-3)
+ sqshrn v17.4h, v9.4s, #10 // V (0-3)
+ sqshrn v22.4h, v11.4s, #10 // U (0-3)
+ sqshrn v23.4h, v13.4s, #10 // V (0-3)
+
+ sqshrn2 v16.8h, v8.4s, #10 // U (0-7)
+ sqshrn2 v17.8h, v10.4s, #10 // V (0-7)
+ sqshrn2 v22.8h, v12.4s, #10 // U (0-7)
+ sqshrn2 v23.8h, v14.4s, #10 // V (0-7)
+
+ stp q16, q22, [x0], #32 // Store all 16 U values
+ stp q17, q23, [x1], #32 // Store all 16 V values
- rgb_to_uv_interleaved_product v19, v20, v21, v0, v1, v2, v3, v4, v5,
v22, v23, v24, v25, v16, v17, #10
-
- str q16, [x0], #16 // store dst_u
- str q17, [x1], #16 // store dst_v
-
- sub w5, w5, #8 // width -= 8
- cmp w5, #8 // width >= 8 ?
+ sub w5, w5, #16 // width -= 16
+ cmp w5, #16 // width >= 16 ?
b.ge 1b
cbz w5, 3f // No pixels left? Exit
@@ -444,3 +498,4 @@ endfunc
DISABLE_DOTPROD
#endif
+
--
2.49.0
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