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FFmpeg/libavutil/riscv/bswap.h

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lavu/riscv: byte-swap operations If the target supports the Basic bit-manipulation (Zbb) extension, then the REV8 instruction is available to reverse byte order. Note that this instruction only exists at the "XLEN" register size, so we need to right shift the result down to the data width. If Zbb is not supported, then this patchset does nothing. Support for run-time detection is left for the future. Currently, there are no bits in auxv/ELF HWCAP for Z-extensions, so there are no clean ways to do this.
2 years ago
/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVUTIL_RISCV_BSWAP_H
#define AVUTIL_RISCV_BSWAP_H
#include <stdint.h>
#include "config.h"
#include "libavutil/attributes.h"
riscv/bswap: use compiler builtins av_bswapXX() are used in context that expect exact size types, notably variable arguments to av_log(). On Linux RV64, uint_fast32_t is an unsigned long, so the current inline assembler does not work properly. Since GCC and Clang gained their byte-swap built-ins before they supported RISC-V, we can simply defer to them. As an added bonus, the compiler can do instruction scheduling, which it couldn't with the Zbb inline assembler.
2 years ago
#if defined (__GNUC__) || defined (__clang__)
#define av_bswap16 __builtin_bswap16
#define av_bswap32 __builtin_bswap32
#define av_bswap64 __builtin_bswap64
#endif
lavu/riscv: byte-swap operations If the target supports the Basic bit-manipulation (Zbb) extension, then the REV8 instruction is available to reverse byte order. Note that this instruction only exists at the "XLEN" register size, so we need to right shift the result down to the data width. If Zbb is not supported, then this patchset does nothing. Support for run-time detection is left for the future. Currently, there are no bits in auxv/ELF HWCAP for Z-extensions, so there are no clean ways to do this.
2 years ago
#endif /* AVUTIL_RISCV_BSWAP_H */