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/*
* Simple C functions to supplement the C library
*
* Copyright (c) 2006 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qemu/bswap.h"
#include "host/cpuinfo.h"
static bool (*buffer_is_zero_accel)(const void *, size_t);
static bool buffer_is_zero_integer(const void *buf, size_t len)
{
if (unlikely(len < 8)) {
/* For a very small buffer, simply accumulate all the bytes. */
const unsigned char *p = buf;
const unsigned char *e = buf + len;
unsigned char t = 0;
do {
t |= *p++;
} while (p < e);
return t == 0;
} else {
/* Otherwise, use the unaligned memory access functions to
handle the beginning and end of the buffer, with a couple
of loops handling the middle aligned section. */
uint64_t t = ldq_he_p(buf);
const uint64_t *p = (uint64_t *)(((uintptr_t)buf + 8) & -8);
const uint64_t *e = (uint64_t *)(((uintptr_t)buf + len) & -8);
for (; p + 8 <= e; p += 8) {
__builtin_prefetch(p + 8);
if (t) {
return false;
}
t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7];
}
while (p < e) {
t |= *p++;
}
t |= ldq_he_p(buf + len - 8);
return t == 0;
}
}
#if defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
#include <immintrin.h>
/* Note that each of these vectorized functions require len >= 64. */
static bool __attribute__((target("sse2")))
buffer_zero_sse2(const void *buf, size_t len)
{
__m128i t = _mm_loadu_si128(buf);
__m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
__m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
__m128i zero = _mm_setzero_si128();
/* Loop over 16-byte aligned blocks of 64. */
while (likely(p <= e)) {
__builtin_prefetch(p);
t = _mm_cmpeq_epi8(t, zero);
if (unlikely(_mm_movemask_epi8(t) != 0xFFFF)) {
return false;
}
t = p[-4] | p[-3] | p[-2] | p[-1];
p += 4;
}
/* Finish the aligned tail. */
t |= e[-3];
t |= e[-2];
t |= e[-1];
/* Finish the unaligned tail. */
t |= _mm_loadu_si128(buf + len - 16);
return _mm_movemask_epi8(_mm_cmpeq_epi8(t, zero)) == 0xFFFF;
}
#ifdef CONFIG_AVX2_OPT
static bool __attribute__((target("avx2")))
buffer_zero_avx2(const void *buf, size_t len)
{
/* Begin with an unaligned head of 32 bytes. */
__m256i t = _mm256_loadu_si256(buf);
__m256i *p = (__m256i *)(((uintptr_t)buf + 5 * 32) & -32);
__m256i *e = (__m256i *)(((uintptr_t)buf + len) & -32);
/* Loop over 32-byte aligned blocks of 128. */
while (p <= e) {
__builtin_prefetch(p);
if (unlikely(!_mm256_testz_si256(t, t))) {
return false;
}
t = p[-4] | p[-3] | p[-2] | p[-1];
p += 4;
} ;
/* Finish the last block of 128 unaligned. */
t |= _mm256_loadu_si256(buf + len - 4 * 32);
t |= _mm256_loadu_si256(buf + len - 3 * 32);
t |= _mm256_loadu_si256(buf + len - 2 * 32);
t |= _mm256_loadu_si256(buf + len - 1 * 32);
return _mm256_testz_si256(t, t);
}
#endif /* CONFIG_AVX2_OPT */
static unsigned __attribute__((noinline))
select_accel_cpuinfo(unsigned info)
{
/* Array is sorted in order of algorithm preference. */
static const struct {
unsigned bit;
bool (*fn)(const void *, size_t);
} all[] = {
#ifdef CONFIG_AVX2_OPT
{ CPUINFO_AVX2, buffer_zero_avx2 },
#endif
{ CPUINFO_SSE2, buffer_zero_sse2 },
{ CPUINFO_ALWAYS, buffer_is_zero_integer },
};
for (unsigned i = 0; i < ARRAY_SIZE(all); ++i) {
if (info & all[i].bit) {
buffer_is_zero_accel = all[i].fn;
return all[i].bit;
}
}
return 0;
}
static unsigned used_accel;
static void __attribute__((constructor)) init_accel(void)
{
used_accel = select_accel_cpuinfo(cpuinfo_init());
}
#define INIT_ACCEL NULL
bool test_buffer_is_zero_next_accel(void)
{
/*
* Accumulate the accelerators that we've already tested, and
* remove them from the set to test this round. We'll get back
* a zero from select_accel_cpuinfo when there are no more.
*/
unsigned used = select_accel_cpuinfo(cpuinfo & ~used_accel);
used_accel |= used;
return used;
}
#else
bool test_buffer_is_zero_next_accel(void)
{
return false;
}
#define INIT_ACCEL buffer_is_zero_integer
#endif
static bool (*buffer_is_zero_accel)(const void *, size_t) = INIT_ACCEL;
bool buffer_is_zero_ool(const void *buf, size_t len)
{
if (unlikely(len == 0)) {
return true;
}
if (!buffer_is_zero_sample3(buf, len)) {
return false;
}
/* All bytes are covered for any len <= 3. */
if (unlikely(len <= 3)) {
return true;
}
if (likely(len >= 256)) {
return buffer_is_zero_accel(buf, len);
}
return buffer_is_zero_integer(buf, len);
}
bool buffer_is_zero_ge256(const void *buf, size_t len)
{
return buffer_is_zero_accel(buf, len);
}
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