mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-10-20 05:25:31 +00:00
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
69 lines
2.0 KiB
ArmAsm
69 lines
2.0 KiB
ArmAsm
/*
|
|
* Copyright © 2022 Rémi Denis-Courmont.
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
#include "config.h"
|
|
#include "libavutil/riscv/asm.S"
|
|
|
|
#if (__riscv_xlen >= 64)
|
|
func ff_bswap32_buf_rvb, zbb
|
|
andi t0, a1, 4
|
|
beqz t0, 1f
|
|
/* Align a1 (input) to 64-bit */
|
|
lwu t0, (a1)
|
|
addi a0, a0, 4
|
|
rev8 t0, t0
|
|
addi a2, a2, -1
|
|
srli t0, t0, __riscv_xlen - 32
|
|
addi a1, a1, 4
|
|
sw t0, -4(a0)
|
|
1:
|
|
andi a3, a2, -2
|
|
sh2add a2, a2, a0
|
|
beqz a3, 3f
|
|
sh2add a3, a3, a0
|
|
2: /* 2 elements (64 bits) at a time on a 64-bit boundary */
|
|
ld t0, (a1)
|
|
addi a0, a0, 8
|
|
rev8 t0, t0
|
|
#if (__riscv_xlen == 64)
|
|
srli t2, t0, 32
|
|
sw t0, -4(a0)
|
|
#else
|
|
srli t1, t0, __riscv_xlen - 64
|
|
srli t2, t0, __riscv_xlen - 32
|
|
sw t1, -4(a0)
|
|
#endif
|
|
addi a1, a1, 8
|
|
sw t2, -8(a0)
|
|
bne a0, a3, 2b
|
|
3:
|
|
beq a0, a2, 5f
|
|
4: /* Process last element */
|
|
lwu t0, (a1)
|
|
addi a0, a0, 4
|
|
rev8 t0, t0
|
|
addi a1, a1, 4
|
|
srli t0, t0, __riscv_xlen - 32
|
|
sw t0, -4(a0)
|
|
5:
|
|
ret
|
|
endfunc
|
|
#endif
|