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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <string.h>
void *memmove(void *dst, const void *src, size_t n)
{
const char *p = src;
char *q = dst;
if (__builtin_expect(q < p, 1)) {
return memcpy(dst, src, n);
} else {
#define PRELOAD_DISTANCE 64
/* a semi-optimized memmove(). we're preloading the src and dst buffers
* as we go */
size_t c0, c1, i;
p += n;
q += n;
/* note: we preload the destination as well, because the 1-byte at a time
* copy below doesn't take advantage of the write-buffer, we need
* to use the cache instead as a poor man's write-combiner */
__builtin_prefetch(p-1);
__builtin_prefetch(q-1);
if (PRELOAD_DISTANCE > 32) {
__builtin_prefetch(p-(32+1));
__builtin_prefetch(q-(32+1));
}
/* do the prefetech as soon as possible, prevent the compiler to
* reorder the instructions above the prefetch */
asm volatile("":::"memory");
c0 = n & 0x1F; /* cache-line is 32 bytes */
c1 = n >> 5;
while ( c1-- ) {
/* ARMv6 can have up to 3 memory access outstanding */
__builtin_prefetch(p - (PRELOAD_DISTANCE+1));
__builtin_prefetch(q - (PRELOAD_DISTANCE+1));
asm volatile("":::"memory");
for (i=0 ; i<32 ; i++) {
*--q = *--p;
}
}
while ( c0-- ) {
*--q = *--p;
}
}
return dst;
}
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