1/*
2 * jquanti-neon.c - sample data conversion and quantization (Arm Neon)
3 *
4 * Copyright (C) 2020, Arm Limited.  All Rights Reserved.
5 *
6 * This software is provided 'as-is', without any express or implied
7 * warranty.  In no event will the authors be held liable for any damages
8 * arising from the use of this software.
9 *
10 * Permission is granted to anyone to use this software for any purpose,
11 * including commercial applications, and to alter it and redistribute it
12 * freely, subject to the following restrictions:
13 *
14 * 1. The origin of this software must not be misrepresented; you must not
15 *    claim that you wrote the original software. If you use this software
16 *    in a product, an acknowledgment in the product documentation would be
17 *    appreciated but is not required.
18 * 2. Altered source versions must be plainly marked as such, and must not be
19 *    misrepresented as being the original software.
20 * 3. This notice may not be removed or altered from any source distribution.
21 */
22
23#define JPEG_INTERNALS
24#include "../../jinclude.h"
25#include "../../jpeglib.h"
26#include "../../jsimd.h"
27#include "../../jdct.h"
28#include "../../jsimddct.h"
29#include "../jsimd.h"
30
31#include <arm_neon.h>
32
33
34/* After downsampling, the resulting sample values are in the range [0, 255],
35 * but the Discrete Cosine Transform (DCT) operates on values centered around
36 * 0.
37 *
38 * To prepare sample values for the DCT, load samples into a DCT workspace,
39 * subtracting CENTERJSAMPLE (128).  The samples, now in the range [-128, 127],
40 * are also widened from 8- to 16-bit.
41 *
42 * The equivalent scalar C function convsamp() can be found in jcdctmgr.c.
43 */
44
45void jsimd_convsamp_neon(JSAMPARRAY sample_data, JDIMENSION start_col,
46                         DCTELEM *workspace)
47{
48  uint8x8_t samp_row0 = vld1_u8(sample_data[0] + start_col);
49  uint8x8_t samp_row1 = vld1_u8(sample_data[1] + start_col);
50  uint8x8_t samp_row2 = vld1_u8(sample_data[2] + start_col);
51  uint8x8_t samp_row3 = vld1_u8(sample_data[3] + start_col);
52  uint8x8_t samp_row4 = vld1_u8(sample_data[4] + start_col);
53  uint8x8_t samp_row5 = vld1_u8(sample_data[5] + start_col);
54  uint8x8_t samp_row6 = vld1_u8(sample_data[6] + start_col);
55  uint8x8_t samp_row7 = vld1_u8(sample_data[7] + start_col);
56
57  int16x8_t row0 =
58    vreinterpretq_s16_u16(vsubl_u8(samp_row0, vdup_n_u8(CENTERJSAMPLE)));
59  int16x8_t row1 =
60    vreinterpretq_s16_u16(vsubl_u8(samp_row1, vdup_n_u8(CENTERJSAMPLE)));
61  int16x8_t row2 =
62    vreinterpretq_s16_u16(vsubl_u8(samp_row2, vdup_n_u8(CENTERJSAMPLE)));
63  int16x8_t row3 =
64    vreinterpretq_s16_u16(vsubl_u8(samp_row3, vdup_n_u8(CENTERJSAMPLE)));
65  int16x8_t row4 =
66    vreinterpretq_s16_u16(vsubl_u8(samp_row4, vdup_n_u8(CENTERJSAMPLE)));
67  int16x8_t row5 =
68    vreinterpretq_s16_u16(vsubl_u8(samp_row5, vdup_n_u8(CENTERJSAMPLE)));
69  int16x8_t row6 =
70    vreinterpretq_s16_u16(vsubl_u8(samp_row6, vdup_n_u8(CENTERJSAMPLE)));
71  int16x8_t row7 =
72    vreinterpretq_s16_u16(vsubl_u8(samp_row7, vdup_n_u8(CENTERJSAMPLE)));
73
74  vst1q_s16(workspace + 0 * DCTSIZE, row0);
75  vst1q_s16(workspace + 1 * DCTSIZE, row1);
76  vst1q_s16(workspace + 2 * DCTSIZE, row2);
77  vst1q_s16(workspace + 3 * DCTSIZE, row3);
78  vst1q_s16(workspace + 4 * DCTSIZE, row4);
79  vst1q_s16(workspace + 5 * DCTSIZE, row5);
80  vst1q_s16(workspace + 6 * DCTSIZE, row6);
81  vst1q_s16(workspace + 7 * DCTSIZE, row7);
82}
83
84
85/* After the DCT, the resulting array of coefficient values needs to be divided
86 * by an array of quantization values.
87 *
88 * To avoid a slow division operation, the DCT coefficients are multiplied by
89 * the (scaled) reciprocals of the quantization values and then right-shifted.
90 *
91 * The equivalent scalar C function quantize() can be found in jcdctmgr.c.
92 */
93
94void jsimd_quantize_neon(JCOEFPTR coef_block, DCTELEM *divisors,
95                         DCTELEM *workspace)
96{
97  JCOEFPTR out_ptr = coef_block;
98  UDCTELEM *recip_ptr = (UDCTELEM *)divisors;
99  UDCTELEM *corr_ptr = (UDCTELEM *)divisors + DCTSIZE2;
100  DCTELEM *shift_ptr = divisors + 3 * DCTSIZE2;
101  int i;
102
103  for (i = 0; i < DCTSIZE; i += DCTSIZE / 2) {
104    /* Load DCT coefficients. */
105    int16x8_t row0 = vld1q_s16(workspace + (i + 0) * DCTSIZE);
106    int16x8_t row1 = vld1q_s16(workspace + (i + 1) * DCTSIZE);
107    int16x8_t row2 = vld1q_s16(workspace + (i + 2) * DCTSIZE);
108    int16x8_t row3 = vld1q_s16(workspace + (i + 3) * DCTSIZE);
109    /* Load reciprocals of quantization values. */
110    uint16x8_t recip0 = vld1q_u16(recip_ptr + (i + 0) * DCTSIZE);
111    uint16x8_t recip1 = vld1q_u16(recip_ptr + (i + 1) * DCTSIZE);
112    uint16x8_t recip2 = vld1q_u16(recip_ptr + (i + 2) * DCTSIZE);
113    uint16x8_t recip3 = vld1q_u16(recip_ptr + (i + 3) * DCTSIZE);
114    uint16x8_t corr0 = vld1q_u16(corr_ptr + (i + 0) * DCTSIZE);
115    uint16x8_t corr1 = vld1q_u16(corr_ptr + (i + 1) * DCTSIZE);
116    uint16x8_t corr2 = vld1q_u16(corr_ptr + (i + 2) * DCTSIZE);
117    uint16x8_t corr3 = vld1q_u16(corr_ptr + (i + 3) * DCTSIZE);
118    int16x8_t shift0 = vld1q_s16(shift_ptr + (i + 0) * DCTSIZE);
119    int16x8_t shift1 = vld1q_s16(shift_ptr + (i + 1) * DCTSIZE);
120    int16x8_t shift2 = vld1q_s16(shift_ptr + (i + 2) * DCTSIZE);
121    int16x8_t shift3 = vld1q_s16(shift_ptr + (i + 3) * DCTSIZE);
122
123    /* Extract sign from coefficients. */
124    int16x8_t sign_row0 = vshrq_n_s16(row0, 15);
125    int16x8_t sign_row1 = vshrq_n_s16(row1, 15);
126    int16x8_t sign_row2 = vshrq_n_s16(row2, 15);
127    int16x8_t sign_row3 = vshrq_n_s16(row3, 15);
128    /* Get absolute value of DCT coefficients. */
129    uint16x8_t abs_row0 = vreinterpretq_u16_s16(vabsq_s16(row0));
130    uint16x8_t abs_row1 = vreinterpretq_u16_s16(vabsq_s16(row1));
131    uint16x8_t abs_row2 = vreinterpretq_u16_s16(vabsq_s16(row2));
132    uint16x8_t abs_row3 = vreinterpretq_u16_s16(vabsq_s16(row3));
133    /* Add correction. */
134    abs_row0 = vaddq_u16(abs_row0, corr0);
135    abs_row1 = vaddq_u16(abs_row1, corr1);
136    abs_row2 = vaddq_u16(abs_row2, corr2);
137    abs_row3 = vaddq_u16(abs_row3, corr3);
138
139    /* Multiply DCT coefficients by quantization reciprocals. */
140    int32x4_t row0_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row0),
141                                                       vget_low_u16(recip0)));
142    int32x4_t row0_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row0),
143                                                       vget_high_u16(recip0)));
144    int32x4_t row1_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row1),
145                                                       vget_low_u16(recip1)));
146    int32x4_t row1_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row1),
147                                                       vget_high_u16(recip1)));
148    int32x4_t row2_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row2),
149                                                       vget_low_u16(recip2)));
150    int32x4_t row2_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row2),
151                                                       vget_high_u16(recip2)));
152    int32x4_t row3_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row3),
153                                                       vget_low_u16(recip3)));
154    int32x4_t row3_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row3),
155                                                       vget_high_u16(recip3)));
156    /* Narrow back to 16-bit. */
157    row0 = vcombine_s16(vshrn_n_s32(row0_l, 16), vshrn_n_s32(row0_h, 16));
158    row1 = vcombine_s16(vshrn_n_s32(row1_l, 16), vshrn_n_s32(row1_h, 16));
159    row2 = vcombine_s16(vshrn_n_s32(row2_l, 16), vshrn_n_s32(row2_h, 16));
160    row3 = vcombine_s16(vshrn_n_s32(row3_l, 16), vshrn_n_s32(row3_h, 16));
161
162    /* Since VSHR only supports an immediate as its second argument, negate the
163     * shift value and shift left.
164     */
165    row0 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row0),
166                                           vnegq_s16(shift0)));
167    row1 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row1),
168                                           vnegq_s16(shift1)));
169    row2 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row2),
170                                           vnegq_s16(shift2)));
171    row3 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row3),
172                                           vnegq_s16(shift3)));
173
174    /* Restore sign to original product. */
175    row0 = veorq_s16(row0, sign_row0);
176    row0 = vsubq_s16(row0, sign_row0);
177    row1 = veorq_s16(row1, sign_row1);
178    row1 = vsubq_s16(row1, sign_row1);
179    row2 = veorq_s16(row2, sign_row2);
180    row2 = vsubq_s16(row2, sign_row2);
181    row3 = veorq_s16(row3, sign_row3);
182    row3 = vsubq_s16(row3, sign_row3);
183
184    /* Store quantized coefficients to memory. */
185    vst1q_s16(out_ptr + (i + 0) * DCTSIZE, row0);
186    vst1q_s16(out_ptr + (i + 1) * DCTSIZE, row1);
187    vst1q_s16(out_ptr + (i + 2) * DCTSIZE, row2);
188    vst1q_s16(out_ptr + (i + 3) * DCTSIZE, row3);
189  }
190}
191