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Richard Henderson88ca8e82016-08-29 11:46:12 -07001/*
2 * Simple C functions to supplement the C library
3 *
4 * Copyright (c) 2006 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24#include "qemu/osdep.h"
Richard Henderson88ca8e82016-08-29 11:46:12 -070025#include "qemu/cutils.h"
Richard Henderson5e33a872016-08-29 11:46:15 -070026#include "qemu/bswap.h"
Richard Henderson88ca8e82016-08-29 11:46:12 -070027
Richard Henderson5e33a872016-08-29 11:46:15 -070028static bool
29buffer_zero_int(const void *buf, size_t len)
30{
31 if (unlikely(len < 8)) {
32 /* For a very small buffer, simply accumulate all the bytes. */
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 /* Otherwise, use the unaligned memory access functions to
44 handle the beginning and end of the buffer, with a couple
45 of loops handling the middle aligned section. */
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
Robert Hoo27f08ea2020-02-29 20:34:35 +080066#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
Richard Henderson5e33a872016-08-29 11:46:15 -070067/* Do not use push_options pragmas unnecessarily, because clang
68 * does not support them.
69 */
Robert Hoo27f08ea2020-02-29 20:34:35 +080070#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
Richard Henderson5e33a872016-08-29 11:46:15 -070071#pragma GCC push_options
72#pragma GCC target("sse2")
73#endif
Richard Henderson88ca8e82016-08-29 11:46:12 -070074#include <emmintrin.h>
Richard Hendersond9911d12016-09-13 13:57:19 -070075
76/* Note that each of these vectorized functions require len >= 64. */
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 /* Loop over 16-byte aligned blocks of 64. */
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 /* Finish the aligned tail. */
98 t |= e[-3];
99 t |= e[-2];
100 t |= e[-1];
101
102 /* Finish the unaligned tail. */
103 t |= _mm_loadu_si128(buf + len - 16);
104
105 return _mm_movemask_epi8(_mm_cmpeq_epi8(t, zero)) == 0xFFFF;
106}
Robert Hoo27f08ea2020-02-29 20:34:35 +0800107#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
Richard Henderson5e33a872016-08-29 11:46:15 -0700108#pragma GCC pop_options
Richard Henderson88ca8e82016-08-29 11:46:12 -0700109#endif
110
Richard Henderson5e33a872016-08-29 11:46:15 -0700111#ifdef CONFIG_AVX2_OPT
Richard Hendersond9911d12016-09-13 13:57:19 -0700112/* Note that due to restrictions/bugs wrt __builtin functions in gcc <= 4.8,
113 * the includes have to be within the corresponding push_options region, and
114 * therefore the regions themselves have to be ordered with increasing ISA.
115 */
Richard Henderson88ca8e82016-08-29 11:46:12 -0700116#pragma GCC push_options
Paolo Bonzini86444f02016-09-13 17:04:52 +0200117#pragma GCC target("sse4")
118#include <smmintrin.h>
Paolo Bonzini86444f02016-09-13 17:04:52 +0200119
Richard Hendersond9911d12016-09-13 13:57:19 -0700120static 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 /* Loop over 16-byte aligned blocks of 64. */
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 /* Finish the aligned tail. */
138 t |= e[-3];
139 t |= e[-2];
140 t |= e[-1];
141
142 /* Finish the unaligned tail. */
143 t |= _mm_loadu_si128(buf + len - 16);
144
145 return _mm_testz_si128(t, t);
146}
147
148#pragma GCC pop_options
Paolo Bonzini86444f02016-09-13 17:04:52 +0200149#pragma GCC push_options
Richard Henderson88ca8e82016-08-29 11:46:12 -0700150#pragma GCC target("avx2")
Richard Henderson88ca8e82016-08-29 11:46:12 -0700151#include <immintrin.h>
Richard Hendersond9911d12016-09-13 13:57:19 -0700152
153static bool
154buffer_zero_avx2(const void *buf, size_t len)
155{
156 /* Begin with an unaligned head of 32 bytes. */
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
Robert Hoo8f13a392020-03-25 14:50:21 +0800161 /* Loop over 32-byte aligned blocks of 128. */
162 while (p <= e) {
163 __builtin_prefetch(p);
164 if (unlikely(!_mm256_testz_si256(t, t))) {
165 return false;
Richard Hendersond9911d12016-09-13 13:57:19 -0700166 }
Robert Hoo8f13a392020-03-25 14:50:21 +0800167 t = p[-4] | p[-3] | p[-2] | p[-1];
168 p += 4;
169 } ;
Richard Hendersond9911d12016-09-13 13:57:19 -0700170
171 /* Finish the last block of 128 unaligned. */
172 t |= _mm256_loadu_si256(buf + len - 4 * 32);
173 t |= _mm256_loadu_si256(buf + len - 3 * 32);
Richard Hendersond9911d12016-09-13 13:57:19 -0700174 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}
Richard Henderson88ca8e82016-08-29 11:46:12 -0700179#pragma GCC pop_options
Richard Hendersond9911d12016-09-13 13:57:19 -0700180#endif /* CONFIG_AVX2_OPT */
181
Robert Hoo27f08ea2020-02-29 20:34:35 +0800182#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 /* Begin with an unaligned head of 64 bytes. */
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 /* Loop over 64-byte aligned blocks of 256. */
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
Richard Hendersond9911d12016-09-13 13:57:19 -0700217/* Note that for test_buffer_is_zero_next_accel, the most preferred
218 * ISA must have the least significant bit.
219 */
Robert Hoo27f08ea2020-02-29 20:34:35 +0800220#define CACHE_AVX512F 1
221#define CACHE_AVX2 2
222#define CACHE_SSE4 4
223#define CACHE_SSE2 8
Richard Hendersond9911d12016-09-13 13:57:19 -0700224
225/* Make sure that these variables are appropriately initialized when
226 * SSE2 is enabled on the compiler command-line, but the compiler is
Richard Henderson5dd89902017-07-18 18:40:18 -1000227 * too old to support CONFIG_AVX2_OPT.
Richard Hendersond9911d12016-09-13 13:57:19 -0700228 */
Robert Hoo27f08ea2020-02-29 20:34:35 +0800229#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
Richard Hendersond9911d12016-09-13 13:57:19 -0700230# 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
Richard Henderson5e33a872016-08-29 11:46:15 -0700238#endif
239
Richard Hendersond9911d12016-09-13 13:57:19 -0700240static unsigned cpuid_cache = INIT_CACHE;
241static bool (*buffer_accel)(const void *, size_t) = INIT_ACCEL;
Robert Hoo27f08ea2020-02-29 20:34:35 +0800242static int length_to_accel = 64;
Richard Henderson5e33a872016-08-29 11:46:15 -0700243
Richard Hendersond9911d12016-09-13 13:57:19 -0700244static 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;
Robert Hoob87c99d2020-03-25 14:50:20 +0800249 length_to_accel = 64;
Richard Hendersond9911d12016-09-13 13:57:19 -0700250 }
251#ifdef CONFIG_AVX2_OPT
252 if (cache & CACHE_SSE4) {
253 fn = buffer_zero_sse4;
Robert Hoob87c99d2020-03-25 14:50:20 +0800254 length_to_accel = 64;
Richard Hendersond9911d12016-09-13 13:57:19 -0700255 }
256 if (cache & CACHE_AVX2) {
257 fn = buffer_zero_avx2;
Robert Hoo8f13a392020-03-25 14:50:21 +0800258 length_to_accel = 128;
Richard Hendersond9911d12016-09-13 13:57:19 -0700259 }
260#endif
Robert Hoo27f08ea2020-02-29 20:34:35 +0800261#ifdef CONFIG_AVX512F_OPT
262 if (cache & CACHE_AVX512F) {
263 fn = buffer_zero_avx512;
264 length_to_accel = 256;
265 }
266#endif
Richard Hendersond9911d12016-09-13 13:57:19 -0700267 buffer_accel = fn;
268}
Richard Henderson5e33a872016-08-29 11:46:15 -0700269
Robert Hoo27f08ea2020-02-29 20:34:35 +0800270#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
Richard Henderson5dd89902017-07-18 18:40:18 -1000271#include "qemu/cpuid.h"
272
Richard Henderson5e33a872016-08-29 11:46:15 -0700273static void __attribute__((constructor)) init_cpuid_cache(void)
Richard Henderson88ca8e82016-08-29 11:46:12 -0700274{
Richard Henderson5e33a872016-08-29 11:46:15 -0700275 int 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 }
Richard Henderson5e33a872016-08-29 11:46:15 -0700284 if (c & bit_SSE4_1) {
285 cache |= CACHE_SSE4;
286 }
287
288 /* We must check that AVX is not just available, but usable. */
Richard Hendersond9911d12016-09-13 13:57:19 -0700289 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);
Robert Hoo27f08ea2020-02-29 20:34:35 +0800293 if ((bv & 0x6) == 0x6 && (b & bit_AVX2)) {
Richard Hendersond9911d12016-09-13 13:57:19 -0700294 cache |= CACHE_AVX2;
Richard Henderson5e33a872016-08-29 11:46:15 -0700295 }
Robert Hoo27f08ea2020-02-29 20:34:35 +0800296 /* 0xe6:
297 * XCR0[7:5] = 111b (OPMASK state, upper 256-bit of ZMM0-ZMM15
298 * and ZMM16-ZMM31 state are enabled by OS)
299 * XCR0[2:1] = 11b (XMM state and YMM state are enabled by OS)
300 */
301 if ((bv & 0xe6) == 0xe6 && (b & bit_AVX512F)) {
302 cache |= CACHE_AVX512F;
303 }
Richard Henderson5e33a872016-08-29 11:46:15 -0700304 }
Richard Henderson5e33a872016-08-29 11:46:15 -0700305 }
306 cpuid_cache = cache;
Richard Hendersond9911d12016-09-13 13:57:19 -0700307 init_accel(cache);
Richard Henderson88ca8e82016-08-29 11:46:12 -0700308}
Richard Hendersond9911d12016-09-13 13:57:19 -0700309#endif /* CONFIG_AVX2_OPT */
Richard Henderson88ca8e82016-08-29 11:46:12 -0700310
Richard Hendersonefad6682016-08-29 11:46:16 -0700311bool test_buffer_is_zero_next_accel(void)
312{
313 /* If no bits set, we just tested buffer_zero_int, and there
314 are no more acceleration options to test. */
315 if (cpuid_cache == 0) {
316 return false;
317 }
318 /* Disable the accelerator we used before and select a new one. */
319 cpuid_cache &= cpuid_cache - 1;
Richard Hendersond9911d12016-09-13 13:57:19 -0700320 init_accel(cpuid_cache);
Richard Hendersonefad6682016-08-29 11:46:16 -0700321 return true;
322}
323
Richard Henderson5e33a872016-08-29 11:46:15 -0700324static bool select_accel_fn(const void *buf, size_t len)
Richard Henderson88ca8e82016-08-29 11:46:12 -0700325{
Robert Hoo27f08ea2020-02-29 20:34:35 +0800326 if (likely(len >= length_to_accel)) {
Richard Hendersond9911d12016-09-13 13:57:19 -0700327 return buffer_accel(buf, len);
Richard Henderson5e33a872016-08-29 11:46:15 -0700328 }
329 return buffer_zero_int(buf, len);
Richard Henderson88ca8e82016-08-29 11:46:12 -0700330}
Richard Henderson5e33a872016-08-29 11:46:15 -0700331
Richard Henderson5e33a872016-08-29 11:46:15 -0700332#else
333#define select_accel_fn buffer_zero_int
Richard Hendersonefad6682016-08-29 11:46:16 -0700334bool test_buffer_is_zero_next_accel(void)
335{
336 return false;
337}
338#endif
339
Richard Henderson88ca8e82016-08-29 11:46:12 -0700340/*
341 * Checks if a buffer is all zeroes
Richard Henderson88ca8e82016-08-29 11:46:12 -0700342 */
343bool buffer_is_zero(const void *buf, size_t len)
344{
Richard Henderson5e33a872016-08-29 11:46:15 -0700345 if (unlikely(len == 0)) {
346 return true;
Richard Henderson88ca8e82016-08-29 11:46:12 -0700347 }
348
Richard Henderson083d0122016-08-29 11:46:17 -0700349 /* Fetch the beginning of the buffer while we select the accelerator. */
350 __builtin_prefetch(buf);
351
Richard Henderson5e33a872016-08-29 11:46:15 -0700352 /* Use an optimized zero check if possible. Note that this also
353 includes a check for an unrolled loop over 64-bit integers. */
354 return select_accel_fn(buf, len);
Richard Henderson88ca8e82016-08-29 11:46:12 -0700355}