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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"
typedef bool (*biz_accel_fn)(const void *, size_t);
static bool buffer_is_zero_int_lt256(const void *buf, size_t len)
{
uint64_t t;
const uint64_t *p, *e;
/*
* Use unaligned memory access functions to handle
* the beginning and end of the buffer.
*/
if (unlikely(len <= 8)) {
return (ldl_he_p(buf) | ldl_he_p(buf + len - 4)) == 0;
}
t = ldq_he_p(buf) | ldq_he_p(buf + len - 8);
p = QEMU_ALIGN_PTR_DOWN(buf + 8, 8);
e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8);
/* Read 0 to 31 aligned words from the middle. */
while (p < e) {
t |= *p++;
}
return t == 0;
}
static bool buffer_is_zero_int_ge256(const void *buf, size_t len)
{
/*
* Use unaligned memory access functions to handle
* the beginning and end of the buffer.
*/
uint64_t t = ldq_he_p(buf) | ldq_he_p(buf + len - 8);
const uint64_t *p = QEMU_ALIGN_PTR_DOWN(buf + 8, 8);
const uint64_t *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8);
/* Collect a partial block at the tail end. */
t |= e[-7] | e[-6] | e[-5] | e[-4] | e[-3] | e[-2] | e[-1];
/*
* Loop over 64 byte blocks.
* With the head and tail removed, e - p >= 30,
* so the loop must iterate at least 3 times.
*/
do {
if (t) {
return false;
}
t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7];
p += 8;
} while (p < e - 7);
return t == 0;
}
#include "host/bufferiszero.c.inc"
static biz_accel_fn buffer_is_zero_accel;
static unsigned accel_index;
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_int_lt256(buf, len);
}
bool buffer_is_zero_ge256(const void *buf, size_t len)
{
return buffer_is_zero_accel(buf, len);
}
bool test_buffer_is_zero_next_accel(void)
{
if (accel_index != 0) {
buffer_is_zero_accel = accel_table[--accel_index];
return true;
}
return false;
}
static void __attribute__((constructor)) init_accel(void)
{
accel_index = best_accel();
buffer_is_zero_accel = accel_table[accel_index];
}
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