1/* adler32_simd.c
2 *
3 * Copyright 2017 The Chromium Authors. All rights reserved.
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the Chromium source repository LICENSE file.
6 *
7 * Per http://en.wikipedia.org/wiki/Adler-32 the adler32 A value (aka s1) is
8 * the sum of N input data bytes D1 ... DN,
9 *
10 * A = A0 + D1 + D2 + ... + DN
11 *
12 * where A0 is the initial value.
13 *
14 * SSE2 _mm_sad_epu8() can be used for byte sums (see http://bit.ly/2wpUOeD,
15 * for example) and accumulating the byte sums can use SSE shuffle-adds (see
16 * the "Integer" section of http://bit.ly/2erPT8t for details). Arm NEON has
17 * similar instructions.
18 *
19 * The adler32 B value (aka s2) sums the A values from each step:
20 *
21 * B0 + (A0 + D1) + (A0 + D1 + D2) + ... + (A0 + D1 + D2 + ... + DN) or
22 *
23 * B0 + N.A0 + N.D1 + (N-1).D2 + (N-2).D3 + ... + (N-(N-1)).DN
24 *
25 * B0 being the initial value. For 32 bytes (ideal for garden-variety SIMD):
26 *
27 * B = B0 + 32.A0 + [D1 D2 D3 ... D32] x [32 31 30 ... 1].
28 *
29 * Adjacent blocks of 32 input bytes can be iterated with the expressions to
30 * compute the adler32 s1 s2 of M >> 32 input bytes [1].
31 *
32 * As M grows, the s1 s2 sums grow. If left unchecked, they would eventually
33 * overflow the precision of their integer representation (bad). However, s1
34 * and s2 also need to be computed modulo the adler BASE value (reduced). If
35 * at most NMAX bytes are processed before a reduce, s1 s2 _cannot_ overflow
36 * a uint32_t type (the NMAX constraint) [2].
37 *
38 * [1] the iterative equations for s2 contain constant factors; these can be
39 * hoisted from the n-blocks do loop of the SIMD code.
40 *
41 * [2] zlib adler32_z() uses this fact to implement NMAX-block-based updates
42 * of the adler s1 s2 of uint32_t type (see adler32.c).
43 */
44
45#include "adler32_simd.h"
46
47/* Definitions from adler32.c: largest prime smaller than 65536 */
48#define BASE 65521U
49/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
50#define NMAX 5552
51
52#if defined(ADLER32_SIMD_SSSE3)
53
54#include <tmmintrin.h>
55
56uint32_t ZLIB_INTERNAL adler32_simd_( /* SSSE3 */
57 uint32_t adler,
58 const unsigned char *buf,
59 z_size_t len)
60{
61 /*
62 * Split Adler-32 into component sums.
63 */
64 uint32_t s1 = adler & 0xffff;
65 uint32_t s2 = adler >> 16;
66
67 /*
68 * Process the data in blocks.
69 */
70 const unsigned BLOCK_SIZE = 1 << 5;
71
72 z_size_t blocks = len / BLOCK_SIZE;
73 len -= blocks * BLOCK_SIZE;
74
75 while (blocks)
76 {
77 unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */
78 if (n > blocks)
79 n = (unsigned) blocks;
80 blocks -= n;
81
82 const __m128i tap1 =
83 _mm_setr_epi8(32,31,30,29,28,27,26,25,24,23,22,21,20,19,18,17);
84 const __m128i tap2 =
85 _mm_setr_epi8(16,15,14,13,12,11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
86 const __m128i zero =
87 _mm_setr_epi8( 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
88 const __m128i ones =
89 _mm_set_epi16( 1, 1, 1, 1, 1, 1, 1, 1);
90
91 /*
92 * Process n blocks of data. At most NMAX data bytes can be
93 * processed before s2 must be reduced modulo BASE.
94 */
95 __m128i v_ps = _mm_set_epi32(0, 0, 0, s1 * n);
96 __m128i v_s2 = _mm_set_epi32(0, 0, 0, s2);
97 __m128i v_s1 = _mm_set_epi32(0, 0, 0, 0);
98
99 do {
100 /*
101 * Load 32 input bytes.
102 */
103 const __m128i bytes1 = _mm_loadu_si128((__m128i*)(buf));
104 const __m128i bytes2 = _mm_loadu_si128((__m128i*)(buf + 16));
105
106 /*
107 * Add previous block byte sum to v_ps.
108 */
109 v_ps = _mm_add_epi32(v_ps, v_s1);
110
111 /*
112 * Horizontally add the bytes for s1, multiply-adds the
113 * bytes by [ 32, 31, 30, ... ] for s2.
114 */
115 v_s1 = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes1, zero));
116 const __m128i mad1 = _mm_maddubs_epi16(bytes1, tap1);
117 v_s2 = _mm_add_epi32(v_s2, _mm_madd_epi16(mad1, ones));
118
119 v_s1 = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes2, zero));
120 const __m128i mad2 = _mm_maddubs_epi16(bytes2, tap2);
121 v_s2 = _mm_add_epi32(v_s2, _mm_madd_epi16(mad2, ones));
122
123 buf += BLOCK_SIZE;
124
125 } while (--n);
126
127 v_s2 = _mm_add_epi32(v_s2, _mm_slli_epi32(v_ps, 5));
128
129 /*
130 * Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
131 */
132
133#define S23O1 _MM_SHUFFLE(2,3,0,1) /* A B C D -> B A D C */
134#define S1O32 _MM_SHUFFLE(1,0,3,2) /* A B C D -> C D A B */
135
136 v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S23O1));
137 v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S1O32));
138
139 s1 += _mm_cvtsi128_si32(v_s1);
140
141 v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S23O1));
142 v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S1O32));
143
144 s2 = _mm_cvtsi128_si32(v_s2);
145
146#undef S23O1
147#undef S1O32
148
149 /*
150 * Reduce.
151 */
152 s1 %= BASE;
153 s2 %= BASE;
154 }
155
156 /*
157 * Handle leftover data.
158 */
159 if (len) {
160 if (len >= 16) {
161 s2 += (s1 += *buf++);
162 s2 += (s1 += *buf++);
163 s2 += (s1 += *buf++);
164 s2 += (s1 += *buf++);
165
166 s2 += (s1 += *buf++);
167 s2 += (s1 += *buf++);
168 s2 += (s1 += *buf++);
169 s2 += (s1 += *buf++);
170
171 s2 += (s1 += *buf++);
172 s2 += (s1 += *buf++);
173 s2 += (s1 += *buf++);
174 s2 += (s1 += *buf++);
175
176 s2 += (s1 += *buf++);
177 s2 += (s1 += *buf++);
178 s2 += (s1 += *buf++);
179 s2 += (s1 += *buf++);
180
181 len -= 16;
182 }
183
184 while (len--) {
185 s2 += (s1 += *buf++);
186 }
187
188 if (s1 >= BASE)
189 s1 -= BASE;
190 s2 %= BASE;
191 }
192
193 /*
194 * Return the recombined sums.
195 */
196 return s1 | (s2 << 16);
197}
198
199#elif defined(ADLER32_SIMD_NEON)
200
201#include <arm_neon.h>
202
203uint32_t ZLIB_INTERNAL adler32_simd_( /* NEON */
204 uint32_t adler,
205 const unsigned char *buf,
206 z_size_t len)
207{
208 /*
209 * Split Adler-32 into component sums.
210 */
211 uint32_t s1 = adler & 0xffff;
212 uint32_t s2 = adler >> 16;
213
214 /*
215 * Serially compute s1 & s2, until the data is 16-byte aligned.
216 */
217 if ((uintptr_t)buf & 15) {
218 while ((uintptr_t)buf & 15) {
219 s2 += (s1 += *buf++);
220 --len;
221 }
222
223 if (s1 >= BASE)
224 s1 -= BASE;
225 s2 %= BASE;
226 }
227
228 /*
229 * Process the data in blocks.
230 */
231 const unsigned BLOCK_SIZE = 1 << 5;
232
233 z_size_t blocks = len / BLOCK_SIZE;
234 len -= blocks * BLOCK_SIZE;
235
236 while (blocks)
237 {
238 unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */
239 if (n > blocks)
240 n = (unsigned) blocks;
241 blocks -= n;
242
243 /*
244 * Process n blocks of data. At most NMAX data bytes can be
245 * processed before s2 must be reduced modulo BASE.
246 */
247 uint32x4_t v_s2 = (uint32x4_t) { 0, 0, 0, s1 * n };
248 uint32x4_t v_s1 = (uint32x4_t) { 0, 0, 0, 0 };
249
250 uint16x8_t v_column_sum_1 = vdupq_n_u16(0);
251 uint16x8_t v_column_sum_2 = vdupq_n_u16(0);
252 uint16x8_t v_column_sum_3 = vdupq_n_u16(0);
253 uint16x8_t v_column_sum_4 = vdupq_n_u16(0);
254
255 do {
256 /*
257 * Load 32 input bytes.
258 */
259 const uint8x16_t bytes1 = vld1q_u8((uint8_t*)(buf));
260 const uint8x16_t bytes2 = vld1q_u8((uint8_t*)(buf + 16));
261
262 /*
263 * Add previous block byte sum to v_s2.
264 */
265 v_s2 = vaddq_u32(v_s2, v_s1);
266
267 /*
268 * Horizontally add the bytes for s1.
269 */
270 v_s1 = vpadalq_u16(v_s1, vpadalq_u8(vpaddlq_u8(bytes1), bytes2));
271
272 /*
273 * Vertically add the bytes for s2.
274 */
275 v_column_sum_1 = vaddw_u8(v_column_sum_1, vget_low_u8 (bytes1));
276 v_column_sum_2 = vaddw_u8(v_column_sum_2, vget_high_u8(bytes1));
277 v_column_sum_3 = vaddw_u8(v_column_sum_3, vget_low_u8 (bytes2));
278 v_column_sum_4 = vaddw_u8(v_column_sum_4, vget_high_u8(bytes2));
279
280 buf += BLOCK_SIZE;
281
282 } while (--n);
283
284 v_s2 = vshlq_n_u32(v_s2, 5);
285
286 /*
287 * Multiply-add bytes by [ 32, 31, 30, ... ] for s2.
288 */
289 v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_1),
290 (uint16x4_t) { 32, 31, 30, 29 });
291 v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_1),
292 (uint16x4_t) { 28, 27, 26, 25 });
293 v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_2),
294 (uint16x4_t) { 24, 23, 22, 21 });
295 v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_2),
296 (uint16x4_t) { 20, 19, 18, 17 });
297 v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_3),
298 (uint16x4_t) { 16, 15, 14, 13 });
299 v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_3),
300 (uint16x4_t) { 12, 11, 10, 9 });
301 v_s2 = vmlal_u16(v_s2, vget_low_u16 (v_column_sum_4),
302 (uint16x4_t) { 8, 7, 6, 5 });
303 v_s2 = vmlal_u16(v_s2, vget_high_u16(v_column_sum_4),
304 (uint16x4_t) { 4, 3, 2, 1 });
305
306 /*
307 * Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
308 */
309 uint32x2_t sum1 = vpadd_u32(vget_low_u32(v_s1), vget_high_u32(v_s1));
310 uint32x2_t sum2 = vpadd_u32(vget_low_u32(v_s2), vget_high_u32(v_s2));
311 uint32x2_t s1s2 = vpadd_u32(sum1, sum2);
312
313 s1 += vget_lane_u32(s1s2, 0);
314 s2 += vget_lane_u32(s1s2, 1);
315
316 /*
317 * Reduce.
318 */
319 s1 %= BASE;
320 s2 %= BASE;
321 }
322
323 /*
324 * Handle leftover data.
325 */
326 if (len) {
327 if (len >= 16) {
328 s2 += (s1 += *buf++);
329 s2 += (s1 += *buf++);
330 s2 += (s1 += *buf++);
331 s2 += (s1 += *buf++);
332
333 s2 += (s1 += *buf++);
334 s2 += (s1 += *buf++);
335 s2 += (s1 += *buf++);
336 s2 += (s1 += *buf++);
337
338 s2 += (s1 += *buf++);
339 s2 += (s1 += *buf++);
340 s2 += (s1 += *buf++);
341 s2 += (s1 += *buf++);
342
343 s2 += (s1 += *buf++);
344 s2 += (s1 += *buf++);
345 s2 += (s1 += *buf++);
346 s2 += (s1 += *buf++);
347
348 len -= 16;
349 }
350
351 while (len--) {
352 s2 += (s1 += *buf++);
353 }
354
355 if (s1 >= BASE)
356 s1 -= BASE;
357 s2 %= BASE;
358 }
359
360 /*
361 * Return the recombined sums.
362 */
363 return s1 | (s2 << 16);
364}
365
366#endif /* ADLER32_SIMD_SSSE3 */
367