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152 lines
4.1 KiB
C
152 lines
4.1 KiB
C
/* Copyright (C) 2011-2013 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <arch/chip.h>
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#include <string.h>
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#include <stdint.h>
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#include "string-endian.h"
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void *
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__memset (void *s, int c, size_t n)
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{
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uint64_t *out64;
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int n64, to_align64;
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uint64_t v64;
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uint8_t *out8 = s;
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/* Experimentation shows that a trivial tight loop is a win up until
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around a size of 20, where writing a word at a time starts to win. */
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#define BYTE_CUTOFF 20
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#if BYTE_CUTOFF < 7
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/* This must be at least at least this big, or some code later
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on doesn't work. */
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# error "BYTE_CUTOFF is too small."
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#endif
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if (n < BYTE_CUTOFF)
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{
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/* Strangely, this turns out to be the tightest way to write
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this loop. */
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if (n != 0)
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{
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do
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{
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/* Strangely, combining these into one line performs worse. */
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*out8 = c;
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out8++;
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}
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while (--n != 0);
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}
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return s;
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}
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/* Align 'out8'. We know n >= 7 so this won't write past the end. */
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while (((uintptr_t) out8 & 7) != 0)
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{
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*out8++ = c;
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--n;
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}
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/* Align 'n'. */
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while (n & 7)
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out8[--n] = c;
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out64 = (uint64_t *) out8;
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n64 = n >> 3;
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/* Tile input byte out to 64 bits. */
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v64 = copy_byte(c);
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/* This must be at least 8 or the following loop doesn't work. */
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#define CACHE_LINE_SIZE_IN_DOUBLEWORDS (CHIP_L2_LINE_SIZE() / 8)
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/* Determine how many words we need to emit before the 'out32'
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pointer becomes aligned modulo the cache line size. */
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to_align64 = (-((uintptr_t) out64 >> 3)) &
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(CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1);
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/* Only bother aligning and using wh64 if there is at least
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one full cache line to process. This check also prevents
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overrunning the end of the buffer with alignment words. */
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if (to_align64 <= n64 - CACHE_LINE_SIZE_IN_DOUBLEWORDS)
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{
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int lines_left;
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/* Align out64 mod the cache line size so we can use wh64. */
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n64 -= to_align64;
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for (; to_align64 != 0; to_align64--)
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{
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*out64 = v64;
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out64++;
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}
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/* Use unsigned divide to turn this into a right shift. */
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lines_left = (unsigned) n64 / CACHE_LINE_SIZE_IN_DOUBLEWORDS;
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do
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{
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/* Only wh64 a few lines at a time, so we don't exceed the
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maximum number of victim lines. */
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int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS ()) ? lines_left
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: CHIP_MAX_OUTSTANDING_VICTIMS ());
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uint64_t *wh = out64;
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int i = x;
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int j;
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lines_left -= x;
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do
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{
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__insn_wh64 (wh);
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wh += CACHE_LINE_SIZE_IN_DOUBLEWORDS;
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}
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while (--i);
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for (j = x * (CACHE_LINE_SIZE_IN_DOUBLEWORDS / 4); j != 0; j--)
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{
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*out64++ = v64;
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*out64++ = v64;
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*out64++ = v64;
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*out64++ = v64;
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}
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}
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while (lines_left != 0);
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/* We processed all full lines above, so only this many
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words remain to be processed. */
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n64 &= CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1;
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}
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/* Now handle any leftover values. */
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if (n64 != 0)
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{
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do
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{
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*out64 = v64;
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out64++;
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}
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while (--n64 != 0);
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}
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return s;
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}
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weak_alias (__memset, memset)
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libc_hidden_builtin_def (memset)
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