FFmpeg/libavcodec/exrdsp.c
Rémi Denis-Courmont ce467421dc lavc/exrdsp: unroll predictor
With explicit unrolling, we can skip half of the sign bit flips, and
the compiler is then better able to optimise the scalar loop:

predictor_c: 31376.0 (before)
predictor_c: 23703.0 (after)
2023-11-14 19:15:51 +02:00

70 lines
1.8 KiB
C

/*
* This file is part of FFmpeg.
*
* Copyright (c) 2006 Industrial Light & Magic, a division of Lucas Digital Ltd. LLC
*
* 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 <stdint.h>
#include "libavutil/attributes.h"
#include "exrdsp.h"
#include "config.h"
static void reorder_pixels_scalar(uint8_t *dst, const uint8_t *src, ptrdiff_t size)
{
const uint8_t *t1 = src;
int half_size = size / 2;
const uint8_t *t2 = src + half_size;
uint8_t *s = dst;
int i;
for (i = 0; i < half_size; i++) {
*(s++) = *(t1++);
*(s++) = *(t2++);
}
}
static void predictor_scalar(uint8_t *src, ptrdiff_t size)
{
/* Unrolled: `src[i + 1] += src[i] - 128;` */
if ((size & 1) == 0) {
src[1] += src[0] ^ 0x80;
src++;
size--;
}
for (ptrdiff_t i = 1; i < size; i += 2) {
uint8_t a = src[i] + src[i - 1];
src[i] = a;
src[i + 1] += a;
src[i] ^= 0x80;
}
}
av_cold void ff_exrdsp_init(ExrDSPContext *c)
{
c->reorder_pixels = reorder_pixels_scalar;
c->predictor = predictor_scalar;
#if ARCH_RISCV
ff_exrdsp_init_riscv(c);
#elif ARCH_X86
ff_exrdsp_init_x86(c);
#endif
}