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/* go-memmove.c -- memmove
Copyright 2021 The Go Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file. */
#include "runtime.h"
void gomemmove(void *, void *, uintptr)
__asm__ (GOSYM_PREFIX "runtime.memmove")
__attribute__ ((no_split_stack));
// This implementation is necessary since
// the __builtin_memmove might use __libc_memmove
// which doesn't require atomicity of pointer-sized
// moves.
void
gomemmove(void *dst, void *src, uintptr len)
{
const uintptr ptr_size = sizeof(dst);
uintptr tail;
uintptr rem;
uintptr dwords;
uintptr i;
char *bdst, *bsrc;
if (len == 0) {
return;
}
// We expect pointer-containing values to be pointer-aligned.
// If these pointers are not aligned, they don't contain pointers.
if ((uintptr)dst % ptr_size != 0 || (uintptr)src % ptr_size != 0 || len < ptr_size) {
__builtin_memmove(dst, src, len);
return;
}
bdst = (char*)dst;
bsrc = (char*)src;
// Move the tail bytes to make the backward move easier.
rem = len;
tail = rem % ptr_size;
if (tail > 0) {
__builtin_memmove(bdst+rem-tail, bsrc+rem-tail, tail);
rem -= tail;
}
// Must now be pointer alignment and rem is multiple of ptr_size.
dwords = rem / ptr_size;
// Determine if a backwards move is needed.
// Forward or backward, move all words.
if ((uintptr)(bdst - bsrc) < rem) {
bdst += rem - ptr_size;
bsrc += rem - ptr_size;
for (i = 0; i<dwords; i++) {
*(uintptr*)bdst = *(uintptr*)bsrc;
bdst -= ptr_size;
bsrc -= ptr_size;
}
} else {
for (i = 0; i<dwords; i++) {
*(uintptr*)bdst = *(uintptr*)bsrc;
bdst += ptr_size;
bsrc += ptr_size;
}
}
}
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