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
jsimd_convsamp_neon(JSAMPARRAY sample_data,JDIMENSION start_col,DCTELEM * workspace)45 void 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
jsimd_quantize_neon(JCOEFPTR coef_block,DCTELEM * divisors,DCTELEM * workspace)94 void 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