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24#include "qemu/osdep.h"
25#include "qemu/cutils.h"
26#include "qemu/bswap.h"
27
28static bool
29buffer_zero_int(const void *buf, size_t len)
30{
31 if (unlikely(len < 8)) {
32
33 const unsigned char *p = buf;
34 const unsigned char *e = buf + len;
35 unsigned char t = 0;
36
37 do {
38 t |= *p++;
39 } while (p < e);
40
41 return t == 0;
42 } else {
43
44
45
46 uint64_t t = ldq_he_p(buf);
47 const uint64_t *p = (uint64_t *)(((uintptr_t)buf + 8) & -8);
48 const uint64_t *e = (uint64_t *)(((uintptr_t)buf + len) & -8);
49
50 for (; p + 8 <= e; p += 8) {
51 __builtin_prefetch(p + 8);
52 if (t) {
53 return false;
54 }
55 t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7];
56 }
57 while (p < e) {
58 t |= *p++;
59 }
60 t |= ldq_he_p(buf + len - 8);
61
62 return t == 0;
63 }
64}
65
66#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
67
68
69
70#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
71#pragma GCC push_options
72#pragma GCC target("sse2")
73#endif
74#include <emmintrin.h>
75
76
77
78static bool
79buffer_zero_sse2(const void *buf, size_t len)
80{
81 __m128i t = _mm_loadu_si128(buf);
82 __m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
83 __m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
84 __m128i zero = _mm_setzero_si128();
85
86
87 while (likely(p <= e)) {
88 __builtin_prefetch(p);
89 t = _mm_cmpeq_epi8(t, zero);
90 if (unlikely(_mm_movemask_epi8(t) != 0xFFFF)) {
91 return false;
92 }
93 t = p[-4] | p[-3] | p[-2] | p[-1];
94 p += 4;
95 }
96
97
98 t |= e[-3];
99 t |= e[-2];
100 t |= e[-1];
101
102
103 t |= _mm_loadu_si128(buf + len - 16);
104
105 return _mm_movemask_epi8(_mm_cmpeq_epi8(t, zero)) == 0xFFFF;
106}
107#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
108#pragma GCC pop_options
109#endif
110
111#ifdef CONFIG_AVX2_OPT
112
113
114
115
116#pragma GCC push_options
117#pragma GCC target("sse4")
118#include <smmintrin.h>
119
120static bool
121buffer_zero_sse4(const void *buf, size_t len)
122{
123 __m128i t = _mm_loadu_si128(buf);
124 __m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
125 __m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
126
127
128 while (likely(p <= e)) {
129 __builtin_prefetch(p);
130 if (unlikely(!_mm_testz_si128(t, t))) {
131 return false;
132 }
133 t = p[-4] | p[-3] | p[-2] | p[-1];
134 p += 4;
135 }
136
137
138 t |= e[-3];
139 t |= e[-2];
140 t |= e[-1];
141
142
143 t |= _mm_loadu_si128(buf + len - 16);
144
145 return _mm_testz_si128(t, t);
146}
147
148#pragma GCC pop_options
149#pragma GCC push_options
150#pragma GCC target("avx2")
151#include <immintrin.h>
152
153static bool
154buffer_zero_avx2(const void *buf, size_t len)
155{
156
157 __m256i t = _mm256_loadu_si256(buf);
158 __m256i *p = (__m256i *)(((uintptr_t)buf + 5 * 32) & -32);
159 __m256i *e = (__m256i *)(((uintptr_t)buf + len) & -32);
160
161
162 while (p <= e) {
163 __builtin_prefetch(p);
164 if (unlikely(!_mm256_testz_si256(t, t))) {
165 return false;
166 }
167 t = p[-4] | p[-3] | p[-2] | p[-1];
168 p += 4;
169 } ;
170
171
172 t |= _mm256_loadu_si256(buf + len - 4 * 32);
173 t |= _mm256_loadu_si256(buf + len - 3 * 32);
174 t |= _mm256_loadu_si256(buf + len - 2 * 32);
175 t |= _mm256_loadu_si256(buf + len - 1 * 32);
176
177 return _mm256_testz_si256(t, t);
178}
179#pragma GCC pop_options
180#endif
181
182#ifdef CONFIG_AVX512F_OPT
183#pragma GCC push_options
184#pragma GCC target("avx512f")
185#include <immintrin.h>
186
187static bool
188buffer_zero_avx512(const void *buf, size_t len)
189{
190
191 __m512i t = _mm512_loadu_si512(buf);
192 __m512i *p = (__m512i *)(((uintptr_t)buf + 5 * 64) & -64);
193 __m512i *e = (__m512i *)(((uintptr_t)buf + len) & -64);
194
195
196 while (p <= e) {
197 __builtin_prefetch(p);
198 if (unlikely(_mm512_test_epi64_mask(t, t))) {
199 return false;
200 }
201 t = p[-4] | p[-3] | p[-2] | p[-1];
202 p += 4;
203 }
204
205 t |= _mm512_loadu_si512(buf + len - 4 * 64);
206 t |= _mm512_loadu_si512(buf + len - 3 * 64);
207 t |= _mm512_loadu_si512(buf + len - 2 * 64);
208 t |= _mm512_loadu_si512(buf + len - 1 * 64);
209
210 return !_mm512_test_epi64_mask(t, t);
211
212}
213#pragma GCC pop_options
214#endif
215
216
217
218
219
220#define CACHE_AVX512F 1
221#define CACHE_AVX2 2
222#define CACHE_SSE4 4
223#define CACHE_SSE2 8
224
225
226
227
228
229#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
230# define INIT_CACHE 0
231# define INIT_ACCEL buffer_zero_int
232#else
233# ifndef __SSE2__
234# error "ISA selection confusion"
235# endif
236# define INIT_CACHE CACHE_SSE2
237# define INIT_ACCEL buffer_zero_sse2
238#endif
239
240static unsigned cpuid_cache = INIT_CACHE;
241static bool (*buffer_accel)(const void *, size_t) = INIT_ACCEL;
242static int length_to_accel = 64;
243
244static void init_accel(unsigned cache)
245{
246 bool (*fn)(const void *, size_t) = buffer_zero_int;
247 if (cache & CACHE_SSE2) {
248 fn = buffer_zero_sse2;
249 length_to_accel = 64;
250 }
251#ifdef CONFIG_AVX2_OPT
252 if (cache & CACHE_SSE4) {
253 fn = buffer_zero_sse4;
254 length_to_accel = 64;
255 }
256 if (cache & CACHE_AVX2) {
257 fn = buffer_zero_avx2;
258 length_to_accel = 128;
259 }
260#endif
261#ifdef CONFIG_AVX512F_OPT
262 if (cache & CACHE_AVX512F) {
263 fn = buffer_zero_avx512;
264 length_to_accel = 256;
265 }
266#endif
267 buffer_accel = fn;
268}
269
270#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
271#include "qemu/cpuid.h"
272
273static void __attribute__((constructor)) init_cpuid_cache(void)
274{
275 unsigned max = __get_cpuid_max(0, NULL);
276 int a, b, c, d;
277 unsigned cache = 0;
278
279 if (max >= 1) {
280 __cpuid(1, a, b, c, d);
281 if (d & bit_SSE2) {
282 cache |= CACHE_SSE2;
283 }
284 if (c & bit_SSE4_1) {
285 cache |= CACHE_SSE4;
286 }
287
288
289 if ((c & bit_OSXSAVE) && (c & bit_AVX) && max >= 7) {
290 int bv;
291 __asm("xgetbv" : "=a"(bv), "=d"(d) : "c"(0));
292 __cpuid_count(7, 0, a, b, c, d);
293 if ((bv & 0x6) == 0x6 && (b & bit_AVX2)) {
294 cache |= CACHE_AVX2;
295 }
296
297
298
299
300
301 if ((bv & 0xe6) == 0xe6 && (b & bit_AVX512F)) {
302 cache |= CACHE_AVX512F;
303 }
304 }
305 }
306 cpuid_cache = cache;
307 init_accel(cache);
308}
309#endif
310
311bool test_buffer_is_zero_next_accel(void)
312{
313
314
315 if (cpuid_cache == 0) {
316 return false;
317 }
318
319 cpuid_cache &= cpuid_cache - 1;
320 init_accel(cpuid_cache);
321 return true;
322}
323
324static bool select_accel_fn(const void *buf, size_t len)
325{
326 if (likely(len >= length_to_accel)) {
327 return buffer_accel(buf, len);
328 }
329 return buffer_zero_int(buf, len);
330}
331
332#else
333#define select_accel_fn buffer_zero_int
334bool test_buffer_is_zero_next_accel(void)
335{
336 return false;
337}
338#endif
339
340
341
342
343bool buffer_is_zero(const void *buf, size_t len)
344{
345 if (unlikely(len == 0)) {
346 return true;
347 }
348
349
350 __builtin_prefetch(buf);
351
352
353
354 return select_accel_fn(buf, len);
355}
356