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/* SPDX-License-Identifier: MIT */
/*
* Copyright © 2005-2014 Rich Felker, et al.
*
* 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 <sel4runtime/gen_config.h>
#include "util.h"
void *__sel4runtime_memset(void *dest, int c, sel4runtime_size_t n)
{
#if CONFIG_SEL4RUNTIME_USE_BUILTINS
return __builtin_memset(dest, c, n);
#else
unsigned char *s = dest;
sel4runtime_size_t k;
/* Fill head and tail with minimal branching. Each
* conditional ensures that all the subsequently used
* offsets are well-defined and in the dest region. */
if (!n) {
return dest;
}
s[0] = s[n - 1] = c;
if (n <= 2) {
return dest;
}
s[1] = s[n - 2] = c;
s[2] = s[n - 3] = c;
if (n <= 6) {
return dest;
}
s[3] = s[n - 4] = c;
if (n <= 8) {
return dest;
}
/* Advance pointer to align it at a 4-byte boundary,
* and truncate n to a multiple of 4. The previous code
* already took care of any head/tail that get cut off
* by the alignment. */
k = -(sel4runtime_uintptr_t)s & 3;
s += k;
n -= k;
n &= -4;
#ifdef __GNUC__
typedef sel4runtime_uint32_t __attribute__((__may_alias__)) u32;
typedef sel4runtime_uint64_t __attribute__((__may_alias__)) u64;
u32 c32 = ((u32) - 1) / 255 * (unsigned char)c;
/* In preparation to copy 32 bytes at a time, aligned on
* an 8-byte bounary, fill head/tail up to 28 bytes each.
* As in the initial byte-based head/tail fill, each
* conditional below ensures that the subsequent offsets
* are valid (e.g. !(n<=24) implies n>=28). */
*(u32 *)(s + 0) = c32;
*(u32 *)(s + n - 4) = c32;
if (n <= 8) {
return dest;
}
*(u32 *)(s + 4) = c32;
*(u32 *)(s + 8) = c32;
*(u32 *)(s + n - 12) = c32;
*(u32 *)(s + n - 8) = c32;
if (n <= 24) {
return dest;
}
*(u32 *)(s + 12) = c32;
*(u32 *)(s + 16) = c32;
*(u32 *)(s + 20) = c32;
*(u32 *)(s + 24) = c32;
*(u32 *)(s + n - 28) = c32;
*(u32 *)(s + n - 24) = c32;
*(u32 *)(s + n - 20) = c32;
*(u32 *)(s + n - 16) = c32;
/* Align to a multiple of 8 so we can fill 64 bits at a time,
* and avoid writing the same bytes twice as much as is
* practical without introducing additional branching. */
k = 24 + ((sel4runtime_uintptr_t)s & 4);
s += k;
n -= k;
/* If this loop is reached, 28 tail bytes have already been
* filled, so any remainder when n drops below 32 can be
* safely ignored. */
u64 c64 = c32 | ((u64)c32 << 32);
for (; n >= 32; n -= 32, s += 32) {
*(u64 *)(s + 0) = c64;
*(u64 *)(s + 8) = c64;
*(u64 *)(s + 16) = c64;
*(u64 *)(s + 24) = c64;
}
#else
/* Pure C fallback with no aliasing violations. */
for (; n; n--, s++) {
*s = c;
}
#endif
return dest;
#endif // CONFIG_SEL4RUNTIME_USE_BUILTINS
}