910d281b21
Since the horizontal and vertical filters are identical except for a transposition, this uses a common subprocedure with an ad-hoc ABI. To preserve return-address stack prediction, a link register has to be used (c.f. the "Control Transfer Instructions" from the RISC-V ISA Manual). The alternate/temporary link register T0 is used here, so that the normal RA is preserved (something Arm cannot do!). To load the strength value based on `qscale`, the shortest possible and PIC-compatible sequence is used: AUIPC; ADD; LBU. The classic LLA; ADD; LBU sequence would add one more instruction since LLA is a convenience alias for AUIPC; ADDI. To ensure that this trick works, relocation relaxation is disabled. To implement the two signed divisions by a power of two toward zero: (x / (1 << SHIFT)) the code relies on the small range of integers involved, computing: (x + (x >> (16 - SHIFT))) >> SHIFT rather than the more general: (x + ((x >> (16 - 1)) & ((1 << SHIFT) - 1))) >> SHIFT Thus one ANDI instruction is avoided. T-Head C908: h263dsp.h_loop_filter_c: 228.2 h263dsp.h_loop_filter_rvv_i32: 144.0 h263dsp.v_loop_filter_c: 242.7 h263dsp.v_loop_filter_rvv_i32: 114.0 (C is probably worse in real use due to less predictible branches.)
42 lines
1.4 KiB
C
42 lines
1.4 KiB
C
/*
|
|
* 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/attributes.h"
|
|
#include "libavutil/cpu.h"
|
|
#include "libavutil/riscv/cpu.h"
|
|
#include "libavcodec/h263dsp.h"
|
|
|
|
void ff_h263_h_loop_filter_rvv(uint8_t *src, int stride, int q);
|
|
void ff_h263_v_loop_filter_rvv(uint8_t *src, int stride, int q);
|
|
|
|
av_cold void ff_h263dsp_init_riscv(H263DSPContext *c)
|
|
{
|
|
#if HAVE_RVV
|
|
int flags = av_get_cpu_flags();
|
|
|
|
if ((flags & AV_CPU_FLAG_RVV_I32) && ff_rv_vlen_least(128)) {
|
|
c->h263_h_loop_filter = ff_h263_h_loop_filter_rvv;
|
|
c->h263_v_loop_filter = ff_h263_v_loop_filter_rvv;
|
|
}
|
|
#endif
|
|
}
|