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/* filter_rvv_intrinsics.c - RISC-V Vector optimized filter functions
*
* Copyright (c) 2023 Google LLC
* Written by Manfred SCHLAEGL, 2022
* Revised by:
* - Dragoș Tiselice <dtiselice@google.com>, May 2023
* - Filip Wasil <f.wasil@samsung.com>, March 2025
* - Liang Junzhao <junzhao.liang@spacemit.com>, November 2025
* - Alexander Smorkalov <alexander.smorkalov@opencv.ai>, December 2025
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
#include "../pngpriv.h"
#ifdef PNG_READ_SUPPORTED
#if PNG_RISCV_RVV_IMPLEMENTATION == 1 /* intrinsics code from pngpriv.h */
#include <riscv_vector.h>
void
png_read_filter_row_up_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
for (size_t vl; len > 0; len -= vl, row += vl, prev_row += vl)
{
vl = __riscv_vsetvl_e8m8(len);
vuint8m8_t prev_vals = __riscv_vle8_v_u8m8(prev_row, vl);
vuint8m8_t row_vals = __riscv_vle8_v_u8m8(row, vl);
row_vals = __riscv_vadd_vv_u8m8(row_vals, prev_vals, vl);
__riscv_vse8_v_u8m8(row, row_vals, vl);
}
}
static inline void
png_read_filter_row_sub_rvv(size_t len, size_t bpp, unsigned char *row)
{
png_bytep rp_end = row + len;
/*
* row: | a | x |
*
* a = a + x
*
* a .. [v0](e8)
* x .. [v8](e8)
*/
size_t vl = __riscv_vsetvl_e8m1(bpp);
/* a = *row */
vuint8m1_t a = __riscv_vle8_v_u8m1(row, vl);
row += bpp;
while (row < rp_end)
{
/* x = *row */
vuint8m1_t x = __riscv_vle8_v_u8m1(row, vl);
/* a = a + x */
a = __riscv_vadd_vv_u8m1(a, x, vl);
/* *row = a */
__riscv_vse8_v_u8m1(row, a, vl);
row += bpp;
}
}
void
png_read_filter_row_sub3_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_sub_rvv(len, 3, row);
PNG_UNUSED(prev_row)
}
void
png_read_filter_row_sub4_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_sub_rvv(len, 4, row);
PNG_UNUSED(prev_row)
}
static inline void
png_read_filter_row_avg_rvv(size_t len, size_t bpp, unsigned char *row,
const unsigned char *prev_row)
{
png_bytep rp_end = row + len;
/*
* row: | a | x |
* prev_row: | | b |
*
* a .. [v2](e8)
* b .. [v4](e8)
* x .. [v8](e8)
* tmp .. [v12-v13](e16)
*/
/* first pixel */
size_t vl = __riscv_vsetvl_e8m1(bpp);
/* b = *prev_row */
vuint8m1_t b = __riscv_vle8_v_u8m1(prev_row, vl);
prev_row += bpp;
/* x = *row */
vuint8m1_t x = __riscv_vle8_v_u8m1(row, vl);
/* b = b / 2 */
b = __riscv_vsrl_vx_u8m1(b, 1, vl);
/* a = x + b */
vuint8m1_t a = __riscv_vadd_vv_u8m1(b, x, vl);
/* *row = a */
__riscv_vse8_v_u8m1(row, a, vl);
row += bpp;
/* remaining pixels */
while (row < rp_end)
{
/* b = *prev_row */
b = __riscv_vle8_v_u8m1(prev_row, vl);
prev_row += bpp;
/* x = *row */
x = __riscv_vle8_v_u8m1(row, vl);
/* a = (a + b) / 2, round to zero with vxrm = 2 */
a = __riscv_vaaddu_vv_u8m1(a, b, 2, vl);
/* a += x */
a = __riscv_vadd_vv_u8m1(a, x, vl);
/* *row = a */
__riscv_vse8_v_u8m1(row, a, vl);
row += bpp;
}
}
void
png_read_filter_row_avg3_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_avg_rvv(len, 3, row, prev_row);
PNG_UNUSED(prev_row)
}
void
png_read_filter_row_avg4_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_avg_rvv(len, 4, row, prev_row);
PNG_UNUSED(prev_row)
}
static inline void
png_read_filter_row_paeth_rvv(size_t len, size_t bpp, unsigned char *row,
const unsigned char *prev)
{
png_bytep rp_end = row + len;
/*
* row: | a | x |
* prev: | c | b |
*
* a .. [v2](e8)
* b .. [v4](e8)
* c .. [v6](e8)
* x .. [v8](e8)
* p .. [v12-v13](e16)
* pa, pb, pc .. [v16-v17, v20-v21, v24-v25](e16)
*/
/* first pixel */
size_t vl = __riscv_vsetvl_e8m1(bpp);
/* a = *row */
vuint8m1_t a = __riscv_vle8_v_u8m1(row, vl);
/* c = *prev */
vuint8m1_t c = __riscv_vle8_v_u8m1(prev, vl);
/* a += c */
a = __riscv_vadd_vv_u8m1(a, c, vl);
/* *row = a */
__riscv_vse8_v_u8m1(row, a, vl);
row += bpp;
prev += bpp;
/* remaining pixels */
while (row < rp_end)
{
/* b = *prev */
vuint8m1_t b = __riscv_vle8_v_u8m1(prev, vl);
prev += bpp;
/* x = *row */
vuint8m1_t x = __riscv_vle8_v_u8m1(row, vl);
/* p = b - c and pc = a - c */
vuint16m2_t p = __riscv_vwsubu_vv_u16m2(b, c, vl);
vuint16m2_t pc = __riscv_vwsubu_vv_u16m2(a, c, vl);
/* pa = |p| */
vuint16m2_t tmp = __riscv_vrsub_vx_u16m2(p, 0, vl);
vuint16m2_t pa = __riscv_vminu_vv_u16m2(p, tmp, vl);
/* pb = |pc| */
tmp = __riscv_vrsub_vx_u16m2(pc, 0, vl);
vuint16m2_t pb = __riscv_vminu_vv_u16m2(pc, tmp, vl);
/* pc = |p + pc| */
pc = __riscv_vadd_vv_u16m2(p, pc, vl);
tmp = __riscv_vrsub_vx_u16m2(pc, 0, vl);
pc = __riscv_vminu_vv_u16m2(pc, tmp, vl);
/*
* The key insight is that we want the minimum of pa, pb, pc.
* - If pa <= pb and pa <= pc, use a
* - Else if pb <= pc, use b
* - Else use c
*/
/* if (pb < pa) { pa = pb; a = b; } */
vbool8_t m1 = __riscv_vmsltu_vv_u16m2_b8(pb, pa, vl);
pa = __riscv_vmerge_vvm_u16m2(pa, pb, m1, vl);
a = __riscv_vmerge_vvm_u8m1(a, b, m1, vl);
/* if (pc < pa) a = c; */
vbool8_t m2 = __riscv_vmsltu_vv_u16m2_b8(pc, pa, vl);
a = __riscv_vmerge_vvm_u8m1(a, c, m2, vl);
/* a = result + x */
a = __riscv_vadd_vv_u8m1(a, x, vl);
/* *row = a */
__riscv_vse8_v_u8m1(row, a, vl);
row += bpp;
/* c = b for next iteration */
c = b;
}
}
void
png_read_filter_row_paeth3_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_paeth_rvv(len, 3, row, prev_row);
}
void
png_read_filter_row_paeth4_rvv(png_row_infop row_info, png_bytep row,
png_const_bytep prev_row)
{
size_t len = row_info->rowbytes;
png_read_filter_row_paeth_rvv(len, 4, row, prev_row);
}
#endif /* PNG_RISCV_RVV_IMPLEMENTATION == 1 */
#endif /* PNG_READ_SUPPORTED */