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jfdctfst-neon.c
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/*
* jfdctfst-neon.c - fast integer FDCT (Arm Neon)
*
* Copyright (C) 2020, Arm Limited. All Rights Reserved.
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#define JPEG_INTERNALS
#include "../../jinclude.h"
#include "../../jpeglib.h"
#include "../../jsimd.h"
#include "../../jdct.h"
#include "../../jsimddct.h"
#include "../jsimd.h"
#include "align.h"
#include <arm_neon.h>
/* jsimd_fdct_ifast_neon() performs a fast, not so accurate forward DCT
* (Discrete Cosine Transform) on one block of samples. It uses the same
* calculations and produces exactly the same output as IJG's original
* jpeg_fdct_ifast() function, which can be found in jfdctfst.c.
*
* Scaled integer constants are used to avoid floating-point arithmetic:
* 0.382683433 = 12544 * 2^-15
* 0.541196100 = 17795 * 2^-15
* 0.707106781 = 23168 * 2^-15
* 0.306562965 = 9984 * 2^-15
*
* See jfdctfst.c for further details of the DCT algorithm. Where possible,
* the variable names and comments here in jsimd_fdct_ifast_neon() match up
* with those in jpeg_fdct_ifast().
*/
#define F_0_382 12544
#define F_0_541 17792
#define F_0_707 23168
#define F_0_306 9984
ALIGN(16) static const int16_t jsimd_fdct_ifast_neon_consts[] = {
F_0_382, F_0_541, F_0_707, F_0_306
};
void jsimd_fdct_ifast_neon(DCTELEM *data)
{
/* Load an 8x8 block of samples into Neon registers. De-interleaving loads
* are used, followed by vuzp to transpose the block such that we have a
* column of samples per vector - allowing all rows to be processed at once.
*/
int16x8x4_t data1 = vld4q_s16(data);
int16x8x4_t data2 = vld4q_s16(data + 4 * DCTSIZE);
int16x8x2_t cols_04 = vuzpq_s16(data1.val[0], data2.val[0]);
int16x8x2_t cols_15 = vuzpq_s16(data1.val[1], data2.val[1]);
int16x8x2_t cols_26 = vuzpq_s16(data1.val[2], data2.val[2]);
int16x8x2_t cols_37 = vuzpq_s16(data1.val[3], data2.val[3]);
int16x8_t col0 = cols_04.val[0];
int16x8_t col1 = cols_15.val[0];
int16x8_t col2 = cols_26.val[0];
int16x8_t col3 = cols_37.val[0];
int16x8_t col4 = cols_04.val[1];
int16x8_t col5 = cols_15.val[1];
int16x8_t col6 = cols_26.val[1];
int16x8_t col7 = cols_37.val[1];
/* Pass 1: process rows. */
/* Load DCT conversion constants. */
const int16x4_t consts = vld1_s16(jsimd_fdct_ifast_neon_consts);
int16x8_t tmp0 = vaddq_s16(col0, col7);
int16x8_t tmp7 = vsubq_s16(col0, col7);
int16x8_t tmp1 = vaddq_s16(col1, col6);
int16x8_t tmp6 = vsubq_s16(col1, col6);
int16x8_t tmp2 = vaddq_s16(col2, col5);
int16x8_t tmp5 = vsubq_s16(col2, col5);
int16x8_t tmp3 = vaddq_s16(col3, col4);
int16x8_t tmp4 = vsubq_s16(col3, col4);
/* Even part */
int16x8_t tmp10 = vaddq_s16(tmp0, tmp3); /* phase 2 */
int16x8_t tmp13 = vsubq_s16(tmp0, tmp3);
int16x8_t tmp11 = vaddq_s16(tmp1, tmp2);
int16x8_t tmp12 = vsubq_s16(tmp1, tmp2);
col0 = vaddq_s16(tmp10, tmp11); /* phase 3 */
col4 = vsubq_s16(tmp10, tmp11);
int16x8_t z1 = vqdmulhq_lane_s16(vaddq_s16(tmp12, tmp13), consts, 2);
col2 = vaddq_s16(tmp13, z1); /* phase 5 */
col6 = vsubq_s16(tmp13, z1);
/* Odd part */
tmp10 = vaddq_s16(tmp4, tmp5); /* phase 2 */
tmp11 = vaddq_s16(tmp5, tmp6);
tmp12 = vaddq_s16(tmp6, tmp7);
int16x8_t z5 = vqdmulhq_lane_s16(vsubq_s16(tmp10, tmp12), consts, 0);
int16x8_t z2 = vqdmulhq_lane_s16(tmp10, consts, 1);
z2 = vaddq_s16(z2, z5);
int16x8_t z4 = vqdmulhq_lane_s16(tmp12, consts, 3);
z5 = vaddq_s16(tmp12, z5);
z4 = vaddq_s16(z4, z5);
int16x8_t z3 = vqdmulhq_lane_s16(tmp11, consts, 2);
int16x8_t z11 = vaddq_s16(tmp7, z3); /* phase 5 */
int16x8_t z13 = vsubq_s16(tmp7, z3);
col5 = vaddq_s16(z13, z2); /* phase 6 */
col3 = vsubq_s16(z13, z2);
col1 = vaddq_s16(z11, z4);
col7 = vsubq_s16(z11, z4);
/* Transpose to work on columns in pass 2. */
int16x8x2_t cols_01 = vtrnq_s16(col0, col1);
int16x8x2_t cols_23 = vtrnq_s16(col2, col3);
int16x8x2_t cols_45 = vtrnq_s16(col4, col5);
int16x8x2_t cols_67 = vtrnq_s16(col6, col7);
int32x4x2_t cols_0145_l = vtrnq_s32(vreinterpretq_s32_s16(cols_01.val[0]),
vreinterpretq_s32_s16(cols_45.val[0]));
int32x4x2_t cols_0145_h = vtrnq_s32(vreinterpretq_s32_s16(cols_01.val[1]),
vreinterpretq_s32_s16(cols_45.val[1]));
int32x4x2_t cols_2367_l = vtrnq_s32(vreinterpretq_s32_s16(cols_23.val[0]),
vreinterpretq_s32_s16(cols_67.val[0]));
int32x4x2_t cols_2367_h = vtrnq_s32(vreinterpretq_s32_s16(cols_23.val[1]),
vreinterpretq_s32_s16(cols_67.val[1]));
int32x4x2_t rows_04 = vzipq_s32(cols_0145_l.val[0], cols_2367_l.val[0]);
int32x4x2_t rows_15 = vzipq_s32(cols_0145_h.val[0], cols_2367_h.val[0]);
int32x4x2_t rows_26 = vzipq_s32(cols_0145_l.val[1], cols_2367_l.val[1]);
int32x4x2_t rows_37 = vzipq_s32(cols_0145_h.val[1], cols_2367_h.val[1]);
int16x8_t row0 = vreinterpretq_s16_s32(rows_04.val[0]);
int16x8_t row1 = vreinterpretq_s16_s32(rows_15.val[0]);
int16x8_t row2 = vreinterpretq_s16_s32(rows_26.val[0]);
int16x8_t row3 = vreinterpretq_s16_s32(rows_37.val[0]);
int16x8_t row4 = vreinterpretq_s16_s32(rows_04.val[1]);
int16x8_t row5 = vreinterpretq_s16_s32(rows_15.val[1]);
int16x8_t row6 = vreinterpretq_s16_s32(rows_26.val[1]);
int16x8_t row7 = vreinterpretq_s16_s32(rows_37.val[1]);
/* Pass 2: process columns. */
tmp0 = vaddq_s16(row0, row7);
tmp7 = vsubq_s16(row0, row7);
tmp1 = vaddq_s16(row1, row6);
tmp6 = vsubq_s16(row1, row6);
tmp2 = vaddq_s16(row2, row5);
tmp5 = vsubq_s16(row2, row5);
tmp3 = vaddq_s16(row3, row4);
tmp4 = vsubq_s16(row3, row4);
/* Even part */
tmp10 = vaddq_s16(tmp0, tmp3); /* phase 2 */
tmp13 = vsubq_s16(tmp0, tmp3);
tmp11 = vaddq_s16(tmp1, tmp2);
tmp12 = vsubq_s16(tmp1, tmp2);
row0 = vaddq_s16(tmp10, tmp11); /* phase 3 */
row4 = vsubq_s16(tmp10, tmp11);
z1 = vqdmulhq_lane_s16(vaddq_s16(tmp12, tmp13), consts, 2);
row2 = vaddq_s16(tmp13, z1); /* phase 5 */
row6 = vsubq_s16(tmp13, z1);
/* Odd part */
tmp10 = vaddq_s16(tmp4, tmp5); /* phase 2 */
tmp11 = vaddq_s16(tmp5, tmp6);
tmp12 = vaddq_s16(tmp6, tmp7);
z5 = vqdmulhq_lane_s16(vsubq_s16(tmp10, tmp12), consts, 0);
z2 = vqdmulhq_lane_s16(tmp10, consts, 1);
z2 = vaddq_s16(z2, z5);
z4 = vqdmulhq_lane_s16(tmp12, consts, 3);
z5 = vaddq_s16(tmp12, z5);
z4 = vaddq_s16(z4, z5);
z3 = vqdmulhq_lane_s16(tmp11, consts, 2);
z11 = vaddq_s16(tmp7, z3); /* phase 5 */
z13 = vsubq_s16(tmp7, z3);
row5 = vaddq_s16(z13, z2); /* phase 6 */
row3 = vsubq_s16(z13, z2);
row1 = vaddq_s16(z11, z4);
row7 = vsubq_s16(z11, z4);
vst1q_s16(data + 0 * DCTSIZE, row0);
vst1q_s16(data + 1 * DCTSIZE, row1);
vst1q_s16(data + 2 * DCTSIZE, row2);
vst1q_s16(data + 3 * DCTSIZE, row3);
vst1q_s16(data + 4 * DCTSIZE, row4);
vst1q_s16(data + 5 * DCTSIZE, row5);
vst1q_s16(data + 6 * DCTSIZE, row6);
vst1q_s16(data + 7 * DCTSIZE, row7);
}