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/* Copyright (C) 2011-2013 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<http://www.gnu.org/licenses/>. */
#include <string.h>
#include <stdint.h>
#include <arch/chip.h>
void *
__memset (void *s, int c, size_t n)
{
uint32_t *out32;
int n32;
uint32_t v16, v32;
uint8_t *out8 = s;
int to_align32;
/* Experimentation shows that a trivial tight loop is a win up until
around a size of 20, where writing a word at a time starts to win. */
#define BYTE_CUTOFF 20
#if BYTE_CUTOFF < 3
/* This must be at least at least this big, or some code later
on doesn't work. */
# error "BYTE_CUTOFF is too small."
#endif
if (n < BYTE_CUTOFF)
{
/* Strangely, this turns out to be the tightest way to write
this loop. */
if (n != 0)
{
do
{
/* Strangely, combining these into one line performs worse. */
*out8 = c;
out8++;
}
while (--n != 0);
}
return s;
}
/* Align 'out8'. We know n >= 3 so this won't write past the end. */
while (((uintptr_t) out8 & 3) != 0)
{
*out8++ = c;
--n;
}
/* Align 'n'. */
while (n & 3)
out8[--n] = c;
out32 = (uint32_t *) out8;
n32 = n >> 2;
/* Tile input byte out to 32 bits. */
v16 = __insn_intlb (c, c);
v32 = __insn_intlh (v16, v16);
/* This must be at least 8 or the following loop doesn't work. */
#define CACHE_LINE_SIZE_IN_WORDS (CHIP_L2_LINE_SIZE() / 4)
/* Determine how many words we need to emit before the 'out32'
pointer becomes aligned modulo the cache line size. */
to_align32 = (-((uintptr_t) out32 >> 2)) & (CACHE_LINE_SIZE_IN_WORDS - 1);
/* Only bother aligning and using wh64 if there is at least one full
cache line to process. This check also prevents overrunning the
end of the buffer with alignment words. */
if (to_align32 <= n32 - CACHE_LINE_SIZE_IN_WORDS)
{
int lines_left;
/* Align out32 mod the cache line size so we can use wh64. */
n32 -= to_align32;
for (; to_align32 != 0; to_align32--)
{
*out32 = v32;
out32++;
}
/* Use unsigned divide to turn this into a right shift. */
lines_left = (unsigned) n32 / CACHE_LINE_SIZE_IN_WORDS;
do
{
/* Only wh64 a few lines at a time, so we don't exceed the
maximum number of victim lines. */
int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS ())? lines_left
: CHIP_MAX_OUTSTANDING_VICTIMS ());
uint32_t *wh = out32;
int i = x;
int j;
lines_left -= x;
do
{
__insn_wh64 (wh);
wh += CACHE_LINE_SIZE_IN_WORDS;
}
while (--i);
for (j = x * (CACHE_LINE_SIZE_IN_WORDS / 4); j != 0; j--)
{
*out32++ = v32;
*out32++ = v32;
*out32++ = v32;
*out32++ = v32;
}
}
while (lines_left != 0);
/* We processed all full lines above, so only this many words
remain to be processed. */
n32 &= CACHE_LINE_SIZE_IN_WORDS - 1;
}
/* Now handle any leftover values. */
if (n32 != 0)
{
do
{
*out32 = v32;
out32++;
}
while (--n32 != 0);
}
return s;
}
weak_alias (__memset, memset)
libc_hidden_builtin_def (memset)
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