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f0ef11ea83
Simply taking the Zbb REV8 instruction into use in a simple loop gives some significant savings: bswap_buf_c: 1081.0 bswap_buf_rvb_b: 771.0 But we can also use the 64-bit REV8 as a pseudo-SIMD instruction with just one additional shift, and one fewer load, effectively doubling the bandwidth. Consequently, this patch is useful even if the compile-time target has Zbb enabled for C code: bswap_buf_c: 1081.0 bswap_buf_rvb_b: 341.0 (this patch) On the other hand, this approach fails miserably for bswap16_buf as the ratio of shifts and stores becomes unfavorable compared to naïve C: bswap16_buf_c: 1542.0 bswap16_buf_rvb_b: 1803.7 Unrolling to process 128 bits (4 samples) at a time actually worsens performance ever so slightly: bswap_buf_c: 1081.0 bswap_buf_rvb_b: 408.5
60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <stdint.h>
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#include "libavutil/attributes.h"
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#include "libavutil/bswap.h"
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#include "bswapdsp.h"
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static void bswap_buf(uint32_t *dst, const uint32_t *src, int w)
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{
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int i;
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for (i = 0; i + 8 <= w; i += 8) {
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dst[i + 0] = av_bswap32(src[i + 0]);
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dst[i + 1] = av_bswap32(src[i + 1]);
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dst[i + 2] = av_bswap32(src[i + 2]);
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dst[i + 3] = av_bswap32(src[i + 3]);
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dst[i + 4] = av_bswap32(src[i + 4]);
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dst[i + 5] = av_bswap32(src[i + 5]);
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dst[i + 6] = av_bswap32(src[i + 6]);
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dst[i + 7] = av_bswap32(src[i + 7]);
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}
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for (; i < w; i++)
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dst[i + 0] = av_bswap32(src[i + 0]);
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}
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static void bswap16_buf(uint16_t *dst, const uint16_t *src, int len)
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{
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while (len--)
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*dst++ = av_bswap16(*src++);
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}
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av_cold void ff_bswapdsp_init(BswapDSPContext *c)
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{
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c->bswap_buf = bswap_buf;
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c->bswap16_buf = bswap16_buf;
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#if ARCH_RISCV
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ff_bswapdsp_init_riscv(c);
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#elif ARCH_X86
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ff_bswapdsp_init_x86(c);
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#endif
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}
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