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FFmpeg/libavcodec/aarch64/hevcdsp_sao_neon.S

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/* -*-arm64-*-
* vim: syntax=arm64asm
*
* AArch64 NEON optimised SAO functions for HEVC decoding
*
* Copyright (c) 2020 Josh Dekker <josh@itanimul.li>
*
* 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 "libavutil/aarch64/asm.S"
// void sao_band_filter(uint8_t *_dst, uint8_t *_src,
// ptrdiff_t stride_dst, ptrdiff_t stride_src,
// int16_t *sao_offset_val, int sao_left_class,
// int width, int height)
function ff_hevc_sao_band_filter_8x8_8_neon, export=1
sub sp, sp, #64
stp xzr, xzr, [sp]
stp xzr, xzr, [sp, #16]
stp xzr, xzr, [sp, #32]
stp xzr, xzr, [sp, #48]
mov w8, #4
0:
ldrsh x9, [x4, x8, lsl #1] // x9 = sao_offset_val[k+1]
subs w8, w8, #1
add w10, w8, w5 // x10 = k + sao_left_class
and w10, w10, #0x1F
strh w9, [sp, x10, lsl #1]
bne 0b
ld1 {v16.16b-v19.16b}, [sp], #64
movi v20.8h, #1
1: // beginning of line
mov w8, w6
2:
// Simple layout for accessing 16bit values
// with 8bit LUT.
//
// 00 01 02 03 04 05 06 07
// +----------------------------------->
// |xDE#xAD|xCA#xFE|xBE#xEF|xFE#xED|....
// +----------------------------------->
// i-0 i-1 i-2 i-3
// dst[x] = av_clip_pixel(src[x] + offset_table[src[x] >> shift]);
ld1 {v2.8b}, [x1]
// load src[x]
uxtl v0.8h, v2.8b
// >> shift
ushr v2.8h, v0.8h, #3 // BIT_DEPTH - 3
// x2 (access lower short)
shl v1.8h, v2.8h, #1 // low (x2, accessing short)
// +1 access upper short
add v3.8h, v1.8h, v20.8h
// shift insert index to upper byte
sli v1.8h, v3.8h, #8
// table
tbx v2.16b, {v16.16b-v19.16b}, v1.16b
// src[x] + table
add v1.8h, v0.8h, v2.8h
// clip + narrow
sqxtun v4.8b, v1.8h
// store
st1 {v4.8b}, [x0]
// done 8 pixels
subs w8, w8, #8
bne 2b
// finished line
subs w7, w7, #1
add x0, x0, x2 // dst += stride_dst
add x1, x1, x3 // src += stride_src
bne 1b
ret
endfunc
// ASSUMES STRIDE_SRC = 192
.Lsao_edge_pos:
.word 1 // horizontal
.word 192 // vertical
.word 192 + 1 // 45 degree
.word 192 - 1 // 135 degree
// ff_hevc_sao_edge_filter_16x16_8_neon(char *dst, char *src, ptrdiff stride_dst,
// int16 *sao_offset_val, int eo, int width, int height)
function ff_hevc_sao_edge_filter_16x16_8_neon, export=1
adr x7, .Lsao_edge_pos
ld1 {v3.8h}, [x3] // load sao_offset_val
sxtw x5, w5
ldr w4, [x7, w4, uxtw #2] // stride_src
mov v3.h[7], v3.h[0] // reorder to [1,2,0,3,4]
mov v3.h[0], v3.h[1]
mov v3.h[1], v3.h[2]
mov v3.h[2], v3.h[7]
// split 16bit values into two tables
uzp2 v1.16b, v3.16b, v3.16b // sao_offset_val -> upper
uzp1 v0.16b, v3.16b, v3.16b // sao_offset_val -> lower
movi v2.16b, #2
mov x15, #192
// strides between end of line and next src/dst
sub x15, x15, x5 // stride_src - width
sub x16, x2, x5 // stride_dst - width
mov x11, x1 // copy base src
1: // new line
mov x14, x5 // copy width
sub x12, x11, x4 // src_a (prev) = src - sao_edge_pos
add x13, x11, x4 // src_b (next) = src + sao_edge_pos
2: // process 16 bytes
ld1 {v3.16b}, [x11], #16 // load src
ld1 {v4.16b}, [x12], #16 // load src_a (prev)
ld1 {v5.16b}, [x13], #16 // load src_b (next)
cmhi v16.16b, v4.16b, v3.16b // (prev > cur)
cmhi v17.16b, v3.16b, v4.16b // (cur > prev)
cmhi v18.16b, v5.16b, v3.16b // (next > cur)
cmhi v19.16b, v3.16b, v5.16b // (cur > next)
sub v20.16b, v16.16b, v17.16b // diff0 = CMP(cur, prev) = (cur > prev) - (cur < prev)
sub v21.16b, v18.16b, v19.16b // diff1 = CMP(cur, next) = (cur > next) - (cur < next)
add v20.16b, v20.16b, v21.16b // diff = diff0 + diff1
add v20.16b, v20.16b, v2.16b // offset_val = diff + 2
tbl v16.16b, {v0.16b}, v20.16b
tbl v17.16b, {v1.16b}, v20.16b
uxtl v20.8h, v3.8b // src[0:7]
uxtl2 v21.8h, v3.16b // src[7:15]
zip1 v18.16b, v16.16b, v17.16b // sao_offset_val lower ->
zip2 v19.16b, v16.16b, v17.16b // sao_offset_val upper ->
sqadd v20.8h, v18.8h, v20.8h // + sao_offset_val
sqadd v21.8h, v19.8h, v21.8h
sqxtun v3.8b, v20.8h
sqxtun2 v3.16b, v21.8h
st1 {v3.16b}, [x0], #16
subs x14, x14, #16 // filtered 16 bytes
b.ne 2b // do we have width to filter?
// no width to filter, setup next line
add x11, x11, x15 // stride src to next line
add x0, x0, x16 // stride dst to next line
subs w6, w6, #1 // filtered line
b.ne 1b // do we have lines to process?
// no lines to filter
ret
endfunc