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1 // Copyright (c) Facebook, Inc. and its affiliates.
2 // All rights reserved.
3 //
4 // Copyright 2019 Google LLC
5 //
6 // This source code is licensed under the BSD-style license found in the
7 // LICENSE file in the root directory of this source tree.
8 
9 #include <assert.h>
10 
11 #include <immintrin.h>
12 
13 #include <xnnpack/igemm.h>
14 #include <xnnpack/math.h>
15 
16 
xnn_qu8_igemm_minmax_ukernel_4x4c2__sse2(size_t mr,size_t nc,size_t kc,size_t ks,const uint8_t ** restrict a,const void * restrict w,uint8_t * restrict c,size_t cm_stride,size_t cn_stride,size_t a_offset,const uint8_t * zero,const union xnn_qu8_gemm_params params[restrict XNN_MIN_ELEMENTS (1)])17 void xnn_qu8_igemm_minmax_ukernel_4x4c2__sse2(
18     size_t mr,
19     size_t nc,
20     size_t kc,
21     size_t ks,
22     const uint8_t** restrict a,
23     const void* restrict w,
24     uint8_t* restrict c,
25     size_t cm_stride,
26     size_t cn_stride,
27     size_t a_offset,
28     const uint8_t* zero,
29     const union xnn_qu8_gemm_params params[restrict XNN_MIN_ELEMENTS(1)]) XNN_DISABLE_TSAN
30 {
31   assert(mr != 0);
32   assert(mr <= 4);
33   assert(nc != 0);
34   assert(kc != 0);
35   assert(ks != 0);
36   assert(ks % (4 * sizeof(void*)) == 0);
37   assert(a_offset % sizeof(int8_t) == 0);
38   assert(a != NULL);
39   assert(w != NULL);
40   assert(c != NULL);
41 
42   kc = round_up_po2(kc, 2);
43   uint8_t* c0 = c;
44   uint8_t* c1 = (uint8_t*) ((uintptr_t) c0 + cm_stride);
45   if XNN_UNPREDICTABLE(mr < 2) {
46     c1 = c0;
47   }
48   uint8_t* c2 = (uint8_t*) ((uintptr_t) c1 + cm_stride);
49   if XNN_UNPREDICTABLE(mr <= 2) {
50     c2 = c1;
51   }
52   uint8_t* c3 = (uint8_t*) ((uintptr_t) c2 + cm_stride);
53   if (mr != 4) {
54     c3 = c2;
55   }
56 
57   const __m128i vb_zero_point = _mm_load_si128((const __m128i*) params->sse2.kernel_zero_point);
58 
59   do {
60     __m128i vacc0x0123 = _mm_loadu_si128((const __m128i*) w);
61     __m128i vacc1x0123 = vacc0x0123;
62     __m128i vacc2x0123 = vacc0x0123;
63     __m128i vacc3x0123 = vacc0x0123;
64     w = (const void*) ((uintptr_t) w + 16);
65 
66     const __m128i vzero = _mm_setzero_si128();
67     size_t p = ks;
68     do {
69       const uint8_t* restrict a0 = a[0];
70       if XNN_UNPREDICTABLE(a0 != zero) {
71         a0 = (const uint8_t*) ((uintptr_t) a0 + a_offset);
72       }
73       const uint8_t* restrict a1 = a[1];
74       if XNN_UNPREDICTABLE(a1 != zero) {
75         a1 = (const uint8_t*) ((uintptr_t) a1 + a_offset);
76       }
77       const uint8_t* restrict a2 = a[2];
78       if XNN_UNPREDICTABLE(a2 != zero) {
79         a2 = (const uint8_t*) ((uintptr_t) a2 + a_offset);
80       }
81       const uint8_t* restrict a3 = a[3];
82       if XNN_UNPREDICTABLE(a3 != zero) {
83         a3 = (const uint8_t*) ((uintptr_t) a3 + a_offset);
84       }
85       a += 4;
86 
87       size_t k = kc;
88       while (k >= 8 * sizeof(uint8_t)) {
89         const __m128i va0 = _mm_loadl_epi64((const __m128i*) a0);
90         const __m128i vxa0 = _mm_unpacklo_epi8(va0, vzero);
91         a0 += 8;
92         const __m128i va1 = _mm_loadl_epi64((const __m128i*) a1);
93         const __m128i vxa1 = _mm_unpacklo_epi8(va1, vzero);
94         a1 += 8;
95         const __m128i va2 = _mm_loadl_epi64((const __m128i*) a2);
96         const __m128i vxa2 = _mm_unpacklo_epi8(va2, vzero);
97         a2 += 8;
98         const __m128i va3 = _mm_loadl_epi64((const __m128i*) a3);
99         const __m128i vxa3 = _mm_unpacklo_epi8(va3, vzero);
100         a3 += 8;
101 
102         const __m128i vb0 = _mm_loadl_epi64((const __m128i*) w);
103         const __m128i vxb0 = _mm_sub_epi16(_mm_unpacklo_epi8(vb0, vzero), vb_zero_point);
104         vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
105         vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
106         vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
107         vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
108 
109         const __m128i vb1 = _mm_loadl_epi64((const __m128i*) ((uintptr_t) w + 8));
110         const __m128i vxb1 = _mm_sub_epi16(_mm_unpacklo_epi8(vb1, vzero), vb_zero_point);
111         vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
112         vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
113         vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
114         vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
115 
116         const __m128i vb2 = _mm_loadl_epi64((const __m128i*) ((uintptr_t) w + 16));
117         const __m128i vxb2 = _mm_sub_epi16(_mm_unpacklo_epi8(vb2, vzero), vb_zero_point);
118         vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
119         vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
120         vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
121         vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
122 
123         const __m128i vb3 = _mm_loadl_epi64((const __m128i*) ((uintptr_t) w + 24));
124         const __m128i vxb3 = _mm_sub_epi16(_mm_unpacklo_epi8(vb3, vzero), vb_zero_point);
125         vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(3, 3, 3, 3)), vxb3));
126         vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(3, 3, 3, 3)), vxb3));
127         vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(3, 3, 3, 3)), vxb3));
128         vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(3, 3, 3, 3)), vxb3));
129 
130         w = (void*) ((uintptr_t) w + 32);
131 
132         k -= 8 * sizeof(uint8_t);
133       }
134       if (k != 0) {
135         const __m128i va0 = _mm_loadl_epi64((const __m128i*) a0);
136         const __m128i vxa0 = _mm_unpacklo_epi8(va0, vzero);
137         const __m128i va1 = _mm_loadl_epi64((const __m128i*) a1);
138         const __m128i vxa1 = _mm_unpacklo_epi8(va1, vzero);
139         const __m128i va2 = _mm_loadl_epi64((const __m128i*) a2);
140         const __m128i vxa2 = _mm_unpacklo_epi8(va2, vzero);
141         const __m128i va3 = _mm_loadl_epi64((const __m128i*) a3);
142         const __m128i vxa3 = _mm_unpacklo_epi8(va3, vzero);
143 
144         const __m128i vb0 = _mm_loadl_epi64((const __m128i*) w);
145         const __m128i vxb0 = _mm_sub_epi16(_mm_unpacklo_epi8(vb0, vzero), vb_zero_point);
146         w = (void*) ((uintptr_t) w + 8);
147 
148         vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
149         vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
150         vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
151         vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(0, 0, 0, 0)), vxb0));
152 
153         if (k > 2 * sizeof(uint8_t)) {
154           const __m128i vb1 = _mm_loadl_epi64((const __m128i*) w);
155           const __m128i vxb1 = _mm_sub_epi16(_mm_unpacklo_epi8(vb1, vzero), vb_zero_point);
156           w = (void*) ((uintptr_t) w + 8);
157 
158           vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
159           vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
160           vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
161           vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(1, 1, 1, 1)), vxb1));
162 
163           if (k > 4 * sizeof(uint8_t)) {
164             const __m128i vb2 = _mm_loadl_epi64((const __m128i*) w);
165             const __m128i vxb2 = _mm_sub_epi16(_mm_unpacklo_epi8(vb2, vzero), vb_zero_point);
166             w = (void*) ((uintptr_t) w + 8);
167 
168             vacc0x0123 = _mm_add_epi32(vacc0x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa0, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
169             vacc1x0123 = _mm_add_epi32(vacc1x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa1, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
170             vacc2x0123 = _mm_add_epi32(vacc2x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa2, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
171             vacc3x0123 = _mm_add_epi32(vacc3x0123, _mm_madd_epi16(_mm_shuffle_epi32(vxa3, _MM_SHUFFLE(2, 2, 2, 2)), vxb2));
172           }
173         }
174       }
175       p -= 4 * sizeof(void*);
176     } while (p != 0);
177 
178     const __m128i vmultiplier = _mm_load_si128((const __m128i*) params->sse2.multiplier);
179     const __m128i vrounding = _mm_load_si128((const __m128i*) params->sse2.rounding);
180 
181     const __m128i vnmask0x0123 = _mm_cmpgt_epi32(_mm_setzero_si128(), vacc0x0123);
182     const __m128i vnmask1x0123 = _mm_cmpgt_epi32(_mm_setzero_si128(), vacc1x0123);
183     const __m128i vnmask2x0123 = _mm_cmpgt_epi32(_mm_setzero_si128(), vacc2x0123);
184     const __m128i vnmask3x0123 = _mm_cmpgt_epi32(_mm_setzero_si128(), vacc3x0123);
185 
186     const __m128i vabsacc0x0123 = _mm_sub_epi32(_mm_xor_si128(vacc0x0123, vnmask0x0123), vnmask0x0123);
187     const __m128i vabsacc1x0123 = _mm_sub_epi32(_mm_xor_si128(vacc1x0123, vnmask1x0123), vnmask1x0123);
188     const __m128i vabsacc2x0123 = _mm_sub_epi32(_mm_xor_si128(vacc2x0123, vnmask2x0123), vnmask2x0123);
189     const __m128i vabsacc3x0123 = _mm_sub_epi32(_mm_xor_si128(vacc3x0123, vnmask3x0123), vnmask3x0123);
190 
191     const __m128i vabsacc0x1032 = _mm_shuffle_epi32(vabsacc0x0123, _MM_SHUFFLE(2, 3, 0, 1));
192     const __m128i vabsacc1x1032 = _mm_shuffle_epi32(vabsacc1x0123, _MM_SHUFFLE(2, 3, 0, 1));
193     const __m128i vabsacc2x1032 = _mm_shuffle_epi32(vabsacc2x0123, _MM_SHUFFLE(2, 3, 0, 1));
194     const __m128i vabsacc3x1032 = _mm_shuffle_epi32(vabsacc3x0123, _MM_SHUFFLE(2, 3, 0, 1));
195 
196     const __m128i vabsprod0x02 = _mm_mul_epu32(vabsacc0x0123, vmultiplier);
197     const __m128i vabsprod1x02 = _mm_mul_epu32(vabsacc1x0123, vmultiplier);
198     const __m128i vabsprod2x02 = _mm_mul_epu32(vabsacc2x0123, vmultiplier);
199     const __m128i vabsprod3x02 = _mm_mul_epu32(vabsacc3x0123, vmultiplier);
200 
201     const __m128i vnmask0x02 = _mm_shuffle_epi32(vnmask0x0123, _MM_SHUFFLE(2, 2, 0, 0));
202     const __m128i vnmask1x02 = _mm_shuffle_epi32(vnmask1x0123, _MM_SHUFFLE(2, 2, 0, 0));
203     const __m128i vnmask2x02 = _mm_shuffle_epi32(vnmask2x0123, _MM_SHUFFLE(2, 2, 0, 0));
204     const __m128i vnmask3x02 = _mm_shuffle_epi32(vnmask3x0123, _MM_SHUFFLE(2, 2, 0, 0));
205 
206     const __m128i vprod0x02 = _mm_sub_epi64(_mm_xor_si128(vabsprod0x02, vnmask0x02), vnmask0x02);
207     const __m128i vprod1x02 = _mm_sub_epi64(_mm_xor_si128(vabsprod1x02, vnmask1x02), vnmask1x02);
208     const __m128i vprod2x02 = _mm_sub_epi64(_mm_xor_si128(vabsprod2x02, vnmask2x02), vnmask2x02);
209     const __m128i vprod3x02 = _mm_sub_epi64(_mm_xor_si128(vabsprod3x02, vnmask3x02), vnmask3x02);
210 
211     const __m128i vq31prod0x02 = _mm_srli_epi64(_mm_add_epi64(vprod0x02, vrounding), 31);
212     const __m128i vq31prod1x02 = _mm_srli_epi64(_mm_add_epi64(vprod1x02, vrounding), 31);
213     const __m128i vq31prod2x02 = _mm_srli_epi64(_mm_add_epi64(vprod2x02, vrounding), 31);
214     const __m128i vq31prod3x02 = _mm_srli_epi64(_mm_add_epi64(vprod3x02, vrounding), 31);
215 
216     const __m128i vabsprod0x13 = _mm_mul_epu32(vabsacc0x1032, vmultiplier);
217     const __m128i vabsprod1x13 = _mm_mul_epu32(vabsacc1x1032, vmultiplier);
218     const __m128i vabsprod2x13 = _mm_mul_epu32(vabsacc2x1032, vmultiplier);
219     const __m128i vabsprod3x13 = _mm_mul_epu32(vabsacc3x1032, vmultiplier);
220 
221     const __m128i vnmask0x13 = _mm_shuffle_epi32(vnmask0x0123, _MM_SHUFFLE(3, 3, 1, 1));
222     const __m128i vnmask1x13 = _mm_shuffle_epi32(vnmask1x0123, _MM_SHUFFLE(3, 3, 1, 1));
223     const __m128i vnmask2x13 = _mm_shuffle_epi32(vnmask2x0123, _MM_SHUFFLE(3, 3, 1, 1));
224     const __m128i vnmask3x13 = _mm_shuffle_epi32(vnmask3x0123, _MM_SHUFFLE(3, 3, 1, 1));
225 
226     const __m128i vprod0x13 = _mm_sub_epi64(_mm_xor_si128(vabsprod0x13, vnmask0x13), vnmask0x13);
227     const __m128i vprod1x13 = _mm_sub_epi64(_mm_xor_si128(vabsprod1x13, vnmask1x13), vnmask1x13);
228     const __m128i vprod2x13 = _mm_sub_epi64(_mm_xor_si128(vabsprod2x13, vnmask2x13), vnmask2x13);
229     const __m128i vprod3x13 = _mm_sub_epi64(_mm_xor_si128(vabsprod3x13, vnmask3x13), vnmask3x13);
230 
231     const __m128i vq31prod0x13 = _mm_srli_epi64(_mm_add_epi64(vprod0x13, vrounding), 31);
232     const __m128i vq31prod1x13 = _mm_srli_epi64(_mm_add_epi64(vprod1x13, vrounding), 31);
233     const __m128i vq31prod2x13 = _mm_srli_epi64(_mm_add_epi64(vprod2x13, vrounding), 31);
234     const __m128i vq31prod3x13 = _mm_srli_epi64(_mm_add_epi64(vprod3x13, vrounding), 31);
235 
236     const __m128i vq31prod0x0213 = _mm_castps_si128(_mm_shuffle_ps(
237         _mm_castsi128_ps(vq31prod0x02), _mm_castsi128_ps(vq31prod0x13), _MM_SHUFFLE(2, 0, 2, 0)));
238     const __m128i vq31prod1x0213 = _mm_castps_si128(_mm_shuffle_ps(
239         _mm_castsi128_ps(vq31prod1x02), _mm_castsi128_ps(vq31prod1x13), _MM_SHUFFLE(2, 0, 2, 0)));
240     const __m128i vq31prod2x0213 = _mm_castps_si128(_mm_shuffle_ps(
241         _mm_castsi128_ps(vq31prod2x02), _mm_castsi128_ps(vq31prod2x13), _MM_SHUFFLE(2, 0, 2, 0)));
242     const __m128i vq31prod3x0213 = _mm_castps_si128(_mm_shuffle_ps(
243         _mm_castsi128_ps(vq31prod3x02), _mm_castsi128_ps(vq31prod3x13), _MM_SHUFFLE(2, 0, 2, 0)));
244 
245     const __m128i vq31prod0x0123 = _mm_shuffle_epi32(vq31prod0x0213, _MM_SHUFFLE(3, 1, 2, 0));
246     const __m128i vq31prod1x0123 = _mm_shuffle_epi32(vq31prod1x0213, _MM_SHUFFLE(3, 1, 2, 0));
247     const __m128i vq31prod2x0123 = _mm_shuffle_epi32(vq31prod2x0213, _MM_SHUFFLE(3, 1, 2, 0));
248     const __m128i vq31prod3x0123 = _mm_shuffle_epi32(vq31prod3x0213, _MM_SHUFFLE(3, 1, 2, 0));
249 
250     const __m128i vremainder_mask = _mm_load_si128((const __m128i*) params->sse2.remainder_mask);
251 
252     const __m128i vrem0x0123 =
253       _mm_add_epi32(_mm_and_si128(vq31prod0x0123, vremainder_mask), _mm_cmpgt_epi32(_mm_setzero_si128(), vq31prod0x0123));
254     const __m128i vrem1x0123 =
255       _mm_add_epi32(_mm_and_si128(vq31prod1x0123, vremainder_mask), _mm_cmpgt_epi32(_mm_setzero_si128(), vq31prod1x0123));
256     const __m128i vrem2x0123 =
257       _mm_add_epi32(_mm_and_si128(vq31prod2x0123, vremainder_mask), _mm_cmpgt_epi32(_mm_setzero_si128(), vq31prod2x0123));
258     const __m128i vrem3x0123 =
259       _mm_add_epi32(_mm_and_si128(vq31prod3x0123, vremainder_mask), _mm_cmpgt_epi32(_mm_setzero_si128(), vq31prod3x0123));
260 
261     const __m128i vremainder_threshold = _mm_load_si128((const __m128i*) params->sse2.remainder_threshold);
262     const __m128i vshift = _mm_load_si128((const __m128i*) params->sse2.shift);
263 
264     vacc0x0123 = _mm_sub_epi32(_mm_sra_epi32(vq31prod0x0123, vshift), _mm_cmpgt_epi32(vrem0x0123, vremainder_threshold));
265     vacc1x0123 = _mm_sub_epi32(_mm_sra_epi32(vq31prod1x0123, vshift), _mm_cmpgt_epi32(vrem1x0123, vremainder_threshold));
266     vacc2x0123 = _mm_sub_epi32(_mm_sra_epi32(vq31prod2x0123, vshift), _mm_cmpgt_epi32(vrem2x0123, vremainder_threshold));
267     vacc3x0123 = _mm_sub_epi32(_mm_sra_epi32(vq31prod3x0123, vshift), _mm_cmpgt_epi32(vrem3x0123, vremainder_threshold));
268 
269     const __m128i voutput_zero_point = _mm_load_si128((const __m128i*) params->sse2.output_zero_point);
270     const __m128i vacc01x0123 = _mm_adds_epi16(_mm_packs_epi32(vacc0x0123, vacc1x0123), voutput_zero_point);
271     const __m128i vacc23x0123 = _mm_adds_epi16(_mm_packs_epi32(vacc2x0123, vacc3x0123), voutput_zero_point);
272     __m128i vout = _mm_packus_epi16(vacc01x0123, vacc23x0123);
273     vout = _mm_min_epu8(vout, _mm_load_si128((const __m128i*) params->sse2.output_max));
274     vout = _mm_max_epu8(vout, _mm_load_si128((const __m128i*) params->sse2.output_min));
275 
276     if XNN_LIKELY(nc >= 4) {
277       *((uint32_t*) c3) = (uint32_t) _mm_cvtsi128_si32(_mm_srli_si128(vout, 12));
278       c3 += cn_stride;
279       *((uint32_t*) c2) = (uint32_t) _mm_cvtsi128_si32(_mm_unpackhi_epi32(vout, vout));
280       c2 += cn_stride;
281       *((uint32_t*) c1) = (uint32_t) _mm_cvtsi128_si32(_mm_srli_epi64(vout, 32));
282       c1 += cn_stride;
283       *((uint32_t*) c0) = (uint32_t) _mm_cvtsi128_si32(vout);
284       c0 += cn_stride;
285 
286       a = (const uint8_t**restrict) ((uintptr_t) a - ks);
287 
288       nc -= 4;
289     } else {
290       if (nc & 2) {
291         *((uint16_t*) c3) = (uint16_t) _mm_extract_epi16(vout, 6); c3 += 2;
292         *((uint16_t*) c2) = (uint16_t) _mm_extract_epi16(vout, 4); c2 += 2;
293         *((uint16_t*) c1) = (uint16_t) _mm_extract_epi16(vout, 2); c1 += 2;
294         *((uint16_t*) c0) = (uint16_t) _mm_extract_epi16(vout, 0); c0 += 2;
295         vout = _mm_srli_epi32(vout, 16);
296       }
297       if (nc & 1) {
298         *((uint8_t*) c3) = (uint8_t) _mm_extract_epi16(vout, 6);
299         *((uint8_t*) c2) = (uint8_t) _mm_extract_epi16(vout, 4);
300         *((uint8_t*) c1) = (uint8_t) _mm_extract_epi16(vout, 2);
301         *((uint8_t*) c0) = (uint8_t) _mm_cvtsi128_si32(vout);
302       }
303 
304       nc = 0;
305     }
306   } while (nc != 0);
307 }
308