* [FFmpeg-devel] [PATCH 1/2] aarch64/hevcdsp_idct_neon: Optimize idct dc
@ 2025-02-19 16:50 Zhao Zhili
2025-03-01 21:39 ` Martin Storsjö
0 siblings, 1 reply; 2+ messages in thread
From: Zhao Zhili @ 2025-02-19 16:50 UTC (permalink / raw)
To: ffmpeg-devel; +Cc: Zhao Zhili
From: Zhao Zhili <zhilizhao@tencent.com>
clang does better than the assembly code before the patch, especially
for small size:
hevc_idct_4x4_dc_8_c: 11.2 ( 1.00x)
hevc_idct_4x4_dc_8_neon: 15.5 ( 0.73x)
hevc_idct_4x4_dc_10_c: 12.0 ( 1.00x)
hevc_idct_4x4_dc_10_neon: 15.2 ( 0.79x)
hevc_idct_8x8_dc_8_c: 13.2 ( 1.00x)
hevc_idct_8x8_dc_8_neon: 18.2 ( 0.73x)
hevc_idct_8x8_dc_10_c: 13.5 ( 1.00x)
hevc_idct_8x8_dc_10_neon: 17.2 ( 0.78x)
hevc_idct_16x16_dc_8_c: 41.8 ( 1.00x)
hevc_idct_16x16_dc_8_neon: 37.8 ( 1.11x)
hevc_idct_16x16_dc_10_c: 41.8 ( 1.00x)
hevc_idct_16x16_dc_10_neon: 37.8 ( 1.11x)
hevc_idct_32x32_dc_8_c: 130.2 ( 1.00x)
hevc_idct_32x32_dc_8_neon: 132.2 ( 0.98x)
hevc_idct_32x32_dc_10_c: 130.2 ( 1.00x)
hevc_idct_32x32_dc_10_neon: 132.2 ( 0.98x)
This patch basically clone what the compiler does, so the performance
is the same.
---
libavcodec/aarch64/hevcdsp_idct_neon.S | 59 ++++++++++++++------------
1 file changed, 33 insertions(+), 26 deletions(-)
diff --git a/libavcodec/aarch64/hevcdsp_idct_neon.S b/libavcodec/aarch64/hevcdsp_idct_neon.S
index 3cac6e6db9..4543ab6b07 100644
--- a/libavcodec/aarch64/hevcdsp_idct_neon.S
+++ b/libavcodec/aarch64/hevcdsp_idct_neon.S
@@ -888,38 +888,45 @@ function ff_hevc_transform_luma_4x4_neon_8, export=1
ret
endfunc
+.macro idct_8x8_dc_store offset
+.irp i, 0x0, 0x20, 0x40, 0x60
+ stp q0, q0, [x0, #(\offset + \i)]
+.endr
+.endm
+
+.macro idct_16x16_dc_store
+.irp index, 0x0, 0x80, 0x100, 0x180
+ idct_8x8_dc_store offset=\index
+.endr
+.endm
+
// void ff_hevc_idct_NxN_dc_DEPTH_neon(int16_t *coeffs)
.macro idct_dc size, bitdepth
function ff_hevc_idct_\size\()x\size\()_dc_\bitdepth\()_neon, export=1
- ld1r {v4.8h}, [x0]
- srshr v4.8h, v4.8h, #1
- srshr v0.8h, v4.8h, #(14 - \bitdepth)
- srshr v1.8h, v4.8h, #(14 - \bitdepth)
-.if \size > 4
- srshr v2.8h, v4.8h, #(14 - \bitdepth)
- srshr v3.8h, v4.8h, #(14 - \bitdepth)
-.if \size > 16 /* dc 32x32 */
- mov x2, #4
+ ldrsh w1, [x0]
+ add w1, w1, #1
+ asr w1, w1, #1
+ add w1, w1, #(1 << (13 - \bitdepth))
+ asr w1, w1, #(14 - \bitdepth)
+ dup v0.8h, w1
+
+.if \size < 8
+ stp q0, q0, [x0]
+.else
+.if \size < 16
+ idct_8x8_dc_store 0x0
+.else
+.if \size < 32
+ idct_16x16_dc_store
+.else
+ add x2, x0, #(32 * 32 * 2)
1:
- subs x2, x2, #1
+ idct_16x16_dc_store
+ add x0, x0, #(16 * 16 * 2)
+ cmp x0, x2
+ b.lt 1b
.endif
- add x12, x0, #64
- mov x13, #128
-.if \size > 8 /* dc 16x16 */
- st1 {v0.8h-v3.8h}, [x0], x13
- st1 {v0.8h-v3.8h}, [x12], x13
- st1 {v0.8h-v3.8h}, [x0], x13
- st1 {v0.8h-v3.8h}, [x12], x13
- st1 {v0.8h-v3.8h}, [x0], x13
- st1 {v0.8h-v3.8h}, [x12], x13
-.endif /* dc 8x8 */
- st1 {v0.8h-v3.8h}, [x0], x13
- st1 {v0.8h-v3.8h}, [x12], x13
-.if \size > 16 /* dc 32x32 */
- bne 1b
.endif
-.else /* dc 4x4 */
- st1 {v0.8h-v1.8h}, [x0]
.endif
ret
endfunc
--
2.46.0
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [FFmpeg-devel] [PATCH 1/2] aarch64/hevcdsp_idct_neon: Optimize idct dc
2025-02-19 16:50 [FFmpeg-devel] [PATCH 1/2] aarch64/hevcdsp_idct_neon: Optimize idct dc Zhao Zhili
@ 2025-03-01 21:39 ` Martin Storsjö
0 siblings, 0 replies; 2+ messages in thread
From: Martin Storsjö @ 2025-03-01 21:39 UTC (permalink / raw)
To: FFmpeg development discussions and patches; +Cc: Zhao Zhili
On Thu, 20 Feb 2025, Zhao Zhili wrote:
> From: Zhao Zhili <zhilizhao@tencent.com>
>
> clang does better than the assembly code before the patch, especially
> for small size:
>
> hevc_idct_4x4_dc_8_c: 11.2 ( 1.00x)
> hevc_idct_4x4_dc_8_neon: 15.5 ( 0.73x)
> hevc_idct_4x4_dc_10_c: 12.0 ( 1.00x)
> hevc_idct_4x4_dc_10_neon: 15.2 ( 0.79x)
> hevc_idct_8x8_dc_8_c: 13.2 ( 1.00x)
> hevc_idct_8x8_dc_8_neon: 18.2 ( 0.73x)
> hevc_idct_8x8_dc_10_c: 13.5 ( 1.00x)
> hevc_idct_8x8_dc_10_neon: 17.2 ( 0.78x)
> hevc_idct_16x16_dc_8_c: 41.8 ( 1.00x)
> hevc_idct_16x16_dc_8_neon: 37.8 ( 1.11x)
> hevc_idct_16x16_dc_10_c: 41.8 ( 1.00x)
> hevc_idct_16x16_dc_10_neon: 37.8 ( 1.11x)
> hevc_idct_32x32_dc_8_c: 130.2 ( 1.00x)
> hevc_idct_32x32_dc_8_neon: 132.2 ( 0.98x)
> hevc_idct_32x32_dc_10_c: 130.2 ( 1.00x)
> hevc_idct_32x32_dc_10_neon: 132.2 ( 0.98x)
>
> This patch basically clone what the compiler does, so the performance
> is the same.
> ---
> libavcodec/aarch64/hevcdsp_idct_neon.S | 59 ++++++++++++++------------
> 1 file changed, 33 insertions(+), 26 deletions(-)
>
> diff --git a/libavcodec/aarch64/hevcdsp_idct_neon.S b/libavcodec/aarch64/hevcdsp_idct_neon.S
> index 3cac6e6db9..4543ab6b07 100644
> --- a/libavcodec/aarch64/hevcdsp_idct_neon.S
> +++ b/libavcodec/aarch64/hevcdsp_idct_neon.S
> @@ -888,38 +888,45 @@ function ff_hevc_transform_luma_4x4_neon_8, export=1
> ret
> endfunc
>
> +.macro idct_8x8_dc_store offset
> +.irp i, 0x0, 0x20, 0x40, 0x60
> + stp q0, q0, [x0, #(\offset + \i)]
> +.endr
> +.endm
> +
> +.macro idct_16x16_dc_store
> +.irp index, 0x0, 0x80, 0x100, 0x180
> + idct_8x8_dc_store offset=\index
> +.endr
> +.endm
> +
> // void ff_hevc_idct_NxN_dc_DEPTH_neon(int16_t *coeffs)
> .macro idct_dc size, bitdepth
> function ff_hevc_idct_\size\()x\size\()_dc_\bitdepth\()_neon, export=1
> - ld1r {v4.8h}, [x0]
> - srshr v4.8h, v4.8h, #1
> - srshr v0.8h, v4.8h, #(14 - \bitdepth)
> - srshr v1.8h, v4.8h, #(14 - \bitdepth)
> -.if \size > 4
> - srshr v2.8h, v4.8h, #(14 - \bitdepth)
> - srshr v3.8h, v4.8h, #(14 - \bitdepth)
> -.if \size > 16 /* dc 32x32 */
> - mov x2, #4
> + ldrsh w1, [x0]
> + add w1, w1, #1
> + asr w1, w1, #1
> + add w1, w1, #(1 << (13 - \bitdepth))
> + asr w1, w1, #(14 - \bitdepth)
> + dup v0.8h, w1
> +
> +.if \size < 8
> + stp q0, q0, [x0]
> +.else
> +.if \size < 16
You can use .elseif instead of .else and a nested .if.
Other than that, this patch looks good to me, thanks!
// Martin
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2025-03-01 21:39 ` Martin Storsjö
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