[FFmpeg-devel] [PATCH] avcodec/aarch64/opusdsp_neon: Simplify opus_postfilter_neon

[Krzysztof Pyrkosz via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

This change removes one extra floating point operation and simplifies
load operations at the beginning of the loop by using dedicated register
for each of the 5 pointers and interleaving it with calculations. The
first case seems to be a bit slower, but the performance increase is
substantial in the other two.

A78 before:
postfilter_15_neon:                                   1684.8 ( 4.23x)
postfilter_512_neon:                                  1395.5 ( 5.10x)
postfilter_1022_neon:                                 1357.0 ( 5.25x)

After:
postfilter_15_neon:                                   1742.2 ( 4.09x)
postfilter_512_neon:                                  1169.8 ( 6.09x)
postfilter_1022_neon:                                 1160.0 ( 6.12x)


A72 before:
postfilter_15_neon:                                   3144.8 ( 2.39x)
postfilter_512_neon:                                  3141.2 ( 2.39x)
postfilter_1022_neon:                                 3230.0 ( 2.33x)

After:
postfilter_15_neon:                                   2847.8 ( 2.64x)
postfilter_512_neon:                                  2877.8 ( 2.61x)
postfilter_1022_neon:                                 2837.2 ( 2.65x)


x13s before:
postfilter_15_neon:                                   1615.4 ( 2.61x)
postfilter_512_neon:                                   963.1 ( 4.39x)
postfilter_1022_neon:                                  963.6 ( 4.39x)

After:
postfilter_15_neon:                                   1749.6 ( 2.41x)
postfilter_512_neon:                                   707.1 ( 5.97x)
postfilter_1022_neon:                                  706.1 ( 5.99x)


Krzysztof

---
 libavcodec/aarch64/opusdsp_neon.S | 31 ++++++++++++-------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

diff --git a/libavcodec/aarch64/opusdsp_neon.S b/libavcodec/aarch64/opusdsp_neon.S
index 253825aa61..990fc44c70 100644
--- a/libavcodec/aarch64/opusdsp_neon.S
+++ b/libavcodec/aarch64/opusdsp_neon.S
@@ -55,35 +55,28 @@ endfunc
 
 function ff_opus_postfilter_neon, export=1
         ld1             {v0.4s}, [x2]
+        sub             x5, x0, w1, sxtw #2
+        sub             x1, x5, #8
         dup             v1.4s, v0.s[1]
         dup             v2.4s, v0.s[2]
         dup             v0.4s, v0.s[0]
 
-        add             w1, w1, #2
-        sub             x1, x0, x1, lsl #2
-
-        ld1             {v3.4s}, [x1]
+        ld1             {v3.4s}, [x1], #16
+        sub             x4, x5, #4
+        add             x6, x5, #4
         fmul            v3.4s, v3.4s, v2.4s
 
-1:      add             x1, x1, #4
-        ld1             {v4.4s}, [x1]
-        add             x1, x1, #4
-        ld1             {v5.4s}, [x1]
-        add             x1, x1, #4
-        ld1             {v6.4s}, [x1]
-        add             x1, x1, #4
-        ld1             {v7.4s}, [x1]
-
+1:      ld1             {v7.4s}, [x1], #16
+        ld1             {v4.4s}, [x4], #16
         fmla            v3.4s, v7.4s, v2.4s
+        ld1             {v6.4s}, [x6], #16
+        ld1             {v5.4s}, [x5], #16
         fadd            v6.4s, v6.4s, v4.4s
+        fmla            v3.4s, v5.4s, v0.4s
 
         ld1             {v4.4s}, [x0]
-        fmla            v4.4s, v5.4s, v0.4s
-
-        fmul            v6.4s, v6.4s, v1.4s
-        fadd            v6.4s, v6.4s, v3.4s
-
-        fadd            v4.4s, v4.4s, v6.4s
+        fmla            v3.4s, v6.4s, v1.4s
+        fadd            v4.4s, v4.4s, v3.4s
         fmul            v3.4s, v7.4s, v2.4s
 
         st1             {v4.4s}, [x0], #16
-- 
2.47.2

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