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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-common.h"
#include "qemu/cutils.h"
#include "qemu/bswap.h"
/* vector definitions */
extern void link_error(void);
#define ACCEL_BUFFER_ZERO(NAME, SIZE, VECTYPE, NONZERO) \
static bool NAME(const void *buf, size_t len) \
{ \
const void *end = buf + len; \
do { \
const VECTYPE *p = buf; \
VECTYPE t; \
__builtin_prefetch(buf + SIZE); \
barrier(); \
if (SIZE == sizeof(VECTYPE) * 4) { \
t = (p[0] | p[1]) | (p[2] | p[3]); \
} else if (SIZE == sizeof(VECTYPE) * 8) { \
t = p[0] | p[1]; \
t |= p[2] | p[3]; \
t |= p[4] | p[5]; \
t |= p[6] | p[7]; \
} else { \
link_error(); \
} \
if (unlikely(NONZERO(t))) { \
return false; \
} \
buf += SIZE; \
} while (buf < end); \
return true; \
}
static bool
buffer_zero_int(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(CONFIG_CPUID_H) && defined(__SSE2__))
#include <cpuid.h>
/* Do not use push_options pragmas unnecessarily, because clang
* does not support them.
*/
#ifndef __SSE2__
#pragma GCC push_options
#pragma GCC target("sse2")
#endif
#include <emmintrin.h>
#define SSE2_NONZERO(X) \
(_mm_movemask_epi8(_mm_cmpeq_epi8((X), _mm_setzero_si128())) != 0xFFFF)
ACCEL_BUFFER_ZERO(buffer_zero_sse2, 64, __m128i, SSE2_NONZERO)
#ifndef __SSE2__
#pragma GCC pop_options
#endif
#ifdef CONFIG_AVX2_OPT
#pragma GCC push_options
#pragma GCC target("sse4")
#include <smmintrin.h>
#define SSE4_NONZERO(X) !_mm_testz_si128((X), (X))
ACCEL_BUFFER_ZERO(buffer_zero_sse4, 64, __m128i, SSE4_NONZERO)
#pragma GCC pop_options
#pragma GCC push_options
#pragma GCC target("avx2")
#include <immintrin.h>
#define AVX2_NONZERO(X) !_mm256_testz_si256((X), (X))
ACCEL_BUFFER_ZERO(buffer_zero_avx2, 128, __m256i, AVX2_NONZERO)
#pragma GCC pop_options
#endif
#define CACHE_AVX2 2
#define CACHE_AVX1 4
#define CACHE_SSE4 8
#define CACHE_SSE2 16
static unsigned cpuid_cache;
static void __attribute__((constructor)) init_cpuid_cache(void)
{
int max = __get_cpuid_max(0, NULL);
int a, b, c, d;
unsigned cache = 0;
if (max >= 1) {
__cpuid(1, a, b, c, d);
if (d & bit_SSE2) {
cache |= CACHE_SSE2;
}
#ifdef CONFIG_AVX2_OPT
if (c & bit_SSE4_1) {
cache |= CACHE_SSE4;
}
/* We must check that AVX is not just available, but usable. */
if ((c & bit_OSXSAVE) && (c & bit_AVX)) {
__asm("xgetbv" : "=a"(a), "=d"(d) : "c"(0));
if ((a & 6) == 6) {
cache |= CACHE_AVX1;
if (max >= 7) {
__cpuid_count(7, 0, a, b, c, d);
if (b & bit_AVX2) {
cache |= CACHE_AVX2;
}
}
}
}
#endif
}
cpuid_cache = cache;
}
#define HAVE_NEXT_ACCEL
bool test_buffer_is_zero_next_accel(void)
{
/* If no bits set, we just tested buffer_zero_int, and there
are no more acceleration options to test. */
if (cpuid_cache == 0) {
return false;
}
/* Disable the accelerator we used before and select a new one. */
cpuid_cache &= cpuid_cache - 1;
return true;
}
static bool select_accel_fn(const void *buf, size_t len)
{
uintptr_t ibuf = (uintptr_t)buf;
#ifdef CONFIG_AVX2_OPT
if (len % 128 == 0 && ibuf % 32 == 0 && (cpuid_cache & CACHE_AVX2)) {
return buffer_zero_avx2(buf, len);
}
if (len % 64 == 0 && ibuf % 16 == 0 && (cpuid_cache & CACHE_SSE4)) {
return buffer_zero_sse4(buf, len);
}
#endif
if (len % 64 == 0 && ibuf % 16 == 0 && (cpuid_cache & CACHE_SSE2)) {
return buffer_zero_sse2(buf, len);
}
return buffer_zero_int(buf, len);
}
#else
#define select_accel_fn buffer_zero_int
#endif
#ifndef HAVE_NEXT_ACCEL
bool test_buffer_is_zero_next_accel(void)
{
return false;
}
#endif
/*
* Checks if a buffer is all zeroes
*/
bool buffer_is_zero(const void *buf, size_t len)
{
if (unlikely(len == 0)) {
return true;
}
/* Fetch the beginning of the buffer while we select the accelerator. */
__builtin_prefetch(buf);
/* Use an optimized zero check if possible. Note that this also
includes a check for an unrolled loop over 64-bit integers. */
return select_accel_fn(buf, len);
}
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