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avcodec/bswapdsp: improve performance by remove manually unroll

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Manually unrolling loops increases code size, which can sometimes
improve performance, but more often than not, it degrades performance.
Keep the C version simple, and add assembly optimizations when needed.

                 x86-clang    x86-gcc-arch-native  x86-msvc     m1-clang      rpi5-clang       pi5-gcc-14
-------------------------------------------------------------------------------------------------------------
bswap_buf_c      57.3 ( 1.00x)  19.4 ( 1.00x)   55.4 ( 1.00x)   0.5 ( 1.00x)  143.5 ( 1.00x)   59.8 ( 1.00x)
bswap_buf_this*  49.0 ( 1.17x)  12.5 ( 1.56x)   17.7 ( 3.13x)   0.3 ( 2.04x)   57.9 ( 2.48x)   73.5 ( 0.81x)
bswap_buf_sse2   28.4 ( 2.02x)  24.3 ( 0.80x)   25.5 ( 2.18x)   -              -               -
bswap_buf_ssse3  24.6 ( 2.32x)  16.0 ( 1.22x)   19.0 ( 2.92x)   -              -               -
bswap_buf_avx2   21.2 ( 2.70x)  11.1 ( 1.74x)   11.2 ( 4.95x)   -              -               -

bswap_buf_c: C implementation before this patch
bswap_buf_this: C implementation after this patch

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
This commit is contained in:
Zhao Zhili
2026-01-10 18:56:26 +00:00
committed by James Almer
co-authored by James Almer
parent bba42ce036
commit 8777fa60e6
1 changed files with 1 additions and 13 deletions
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libavcodec/bswapdsp.c
+1 -13
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@@ -24,19 +24,7 @@
static void bswap_buf(uint32_t *dst, const uint32_t *src, int w)
{
int i;
for (i = 0; i + 8 <= w; i += 8) {
dst[i + 0] = av_bswap32(src[i + 0]);
dst[i + 1] = av_bswap32(src[i + 1]);
dst[i + 2] = av_bswap32(src[i + 2]);
dst[i + 3] = av_bswap32(src[i + 3]);
dst[i + 4] = av_bswap32(src[i + 4]);
dst[i + 5] = av_bswap32(src[i + 5]);
dst[i + 6] = av_bswap32(src[i + 6]);
dst[i + 7] = av_bswap32(src[i + 7]);
}
for (; i < w; i++)
for (int i = 0; i < w; i++)
dst[i + 0] = av_bswap32(src[i + 0]);
}