c53c70a90f
This change cleans up the string code in a number of ways: - For memcpy(), fix bug in prefetch and increase distance to 3 lines; optimize for unaligned data; do all loads before wh64 to make memcpy safe for forward-overlapping calls; etc. Performance is improved. - Use new copy_byte() function on tilegx to spread a single byte value out into a full word using the shufflebytes instruction. - Clean up header include ordering to be more canonical, and remove spurious #undefs of function names. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
142 lines
3.4 KiB
C
142 lines
3.4 KiB
C
/*
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* Copyright 2011 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/module.h>
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#include <arch/chip.h>
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#include "string-endian.h"
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void *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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*/
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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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*/
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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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/* Strangely, this turns out to be the tightest way to
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* write this loop.
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*/
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if (n != 0) {
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do {
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/* Strangely, combining these into one line
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* performs worse.
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*/
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*out8 = c;
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out8++;
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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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*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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*/
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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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*/
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if (to_align64 <= n64 - CACHE_LINE_SIZE_IN_DOUBLEWORDS) {
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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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*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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/* Only wh64 a few lines at a time, so we don't
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* exceed the maximum number of victim lines.
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*/
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int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
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? 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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__insn_wh64(wh);
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wh += CACHE_LINE_SIZE_IN_DOUBLEWORDS;
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} while (--i);
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for (j = x * (CACHE_LINE_SIZE_IN_DOUBLEWORDS / 4);
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j != 0; j--) {
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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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} 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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*/
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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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do {
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*out64 = v64;
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out64++;
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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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EXPORT_SYMBOL(memset);
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