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324899b748
This adds runtime support to use Zbb REV8 for 32- and 64-bit byte-wise
swaps. The result is about five times slower than if targetting Zbb
statically, but still a lot faster than the default bespoke C code or a
call to GCC run-time functions.
For 16-bit swap, this is however unsurprisingly a lot worse, and so this
sticks to the baseline. In fact, even using REV8 statically does not
seem to be beneficial in that case.
Zbb static Zbb dynamic I baseline
bswap16: 0.668184765 3.340764069 0.668029012
bswap32: 0.668174014 3.340763319 9.353855435
bswap64: 0.668221765 3.340496313 14.698672283
(seconds for 1 billion iterations on a SiFive-U74 core)
73 lines
2.0 KiB
C
73 lines
2.0 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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#ifndef AVUTIL_RISCV_BSWAP_H
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#define AVUTIL_RISCV_BSWAP_H
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#include <stdint.h>
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#include "config.h"
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#include "libavutil/attributes.h"
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#include "libavutil/riscv/cpu.h"
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#if defined (__GNUC__) || defined (__clang__)
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#define av_bswap16 __builtin_bswap16
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static av_always_inline av_const uint32_t av_bswap32_rv(uint32_t x)
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{
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#if HAVE_RV && !defined(__riscv_zbb)
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if (!__builtin_constant_p(x) &&
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__builtin_expect(ff_rv_zbb_support(), 1)) {
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uintptr_t y;
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__asm__ (
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".option push\n"
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".option arch, +zbb\n"
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"rev8 %0, %1\n"
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".option pop" : "=r" (y) : "r" (x));
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return y >> (__riscv_xlen - 32);
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}
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#endif
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return __builtin_bswap32(x);
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}
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#define av_bswap32 av_bswap32_rv
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#if __riscv_xlen >= 64
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static av_always_inline av_const uint64_t av_bswap64_rv(uint64_t x)
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{
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#if HAVE_RV && !defined(__riscv_zbb)
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if (!__builtin_constant_p(x) &&
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__builtin_expect(ff_rv_zbb_support(), 1)) {
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uintptr_t y;
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__asm__ (
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".option push\n"
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".option arch, +zbb\n"
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"rev8 %0, %1\n"
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".option pop" : "=r" (y) : "r" (x));
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return y >> (__riscv_xlen - 64);
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}
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#endif
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return __builtin_bswap64(x);
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}
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#define av_bswap64 av_bswap64_rv
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#endif
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#endif
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#endif /* AVUTIL_RISCV_BSWAP_H */
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