1 /*
2 * Copyright 2011 Tilera Corporation. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation, version 2.
7 *
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 * NON INFRINGEMENT. See the GNU General Public License for
12 * more details.
13 */
14
15 #include <linux/types.h>
16 #include <linux/string.h>
17 #include <linux/module.h>
18 #include <arch/chip.h>
19 #include "string-endian.h"
20
memset(void * s,int c,size_t n)21 void *memset(void *s, int c, size_t n)
22 {
23 uint64_t *out64;
24 int n64, to_align64;
25 uint64_t v64;
26 uint8_t *out8 = s;
27
28 /* Experimentation shows that a trivial tight loop is a win up until
29 * around a size of 20, where writing a word at a time starts to win.
30 */
31 #define BYTE_CUTOFF 20
32
33 #if BYTE_CUTOFF < 7
34 /* This must be at least at least this big, or some code later
35 * on doesn't work.
36 */
37 #error "BYTE_CUTOFF is too small"
38 #endif
39
40 if (n < BYTE_CUTOFF) {
41 /* Strangely, this turns out to be the tightest way to
42 * write this loop.
43 */
44 if (n != 0) {
45 do {
46 /* Strangely, combining these into one line
47 * performs worse.
48 */
49 *out8 = c;
50 out8++;
51 } while (--n != 0);
52 }
53
54 return s;
55 }
56
57 /* Align 'out8'. We know n >= 7 so this won't write past the end. */
58 while (((uintptr_t) out8 & 7) != 0) {
59 *out8++ = c;
60 --n;
61 }
62
63 /* Align 'n'. */
64 while (n & 7)
65 out8[--n] = c;
66
67 out64 = (uint64_t *) out8;
68 n64 = n >> 3;
69
70 /* Tile input byte out to 64 bits. */
71 v64 = copy_byte(c);
72
73 /* This must be at least 8 or the following loop doesn't work. */
74 #define CACHE_LINE_SIZE_IN_DOUBLEWORDS (CHIP_L2_LINE_SIZE() / 8)
75
76 /* Determine how many words we need to emit before the 'out32'
77 * pointer becomes aligned modulo the cache line size.
78 */
79 to_align64 = (-((uintptr_t)out64 >> 3)) &
80 (CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1);
81
82 /* Only bother aligning and using wh64 if there is at least
83 * one full cache line to process. This check also prevents
84 * overrunning the end of the buffer with alignment words.
85 */
86 if (to_align64 <= n64 - CACHE_LINE_SIZE_IN_DOUBLEWORDS) {
87 int lines_left;
88
89 /* Align out64 mod the cache line size so we can use wh64. */
90 n64 -= to_align64;
91 for (; to_align64 != 0; to_align64--) {
92 *out64 = v64;
93 out64++;
94 }
95
96 /* Use unsigned divide to turn this into a right shift. */
97 lines_left = (unsigned)n64 / CACHE_LINE_SIZE_IN_DOUBLEWORDS;
98
99 do {
100 /* Only wh64 a few lines at a time, so we don't
101 * exceed the maximum number of victim lines.
102 */
103 int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
104 ? lines_left
105 : CHIP_MAX_OUTSTANDING_VICTIMS());
106 uint64_t *wh = out64;
107 int i = x;
108 int j;
109
110 lines_left -= x;
111
112 do {
113 __insn_wh64(wh);
114 wh += CACHE_LINE_SIZE_IN_DOUBLEWORDS;
115 } while (--i);
116
117 for (j = x * (CACHE_LINE_SIZE_IN_DOUBLEWORDS / 4);
118 j != 0; j--) {
119 *out64++ = v64;
120 *out64++ = v64;
121 *out64++ = v64;
122 *out64++ = v64;
123 }
124 } while (lines_left != 0);
125
126 /* We processed all full lines above, so only this many
127 * words remain to be processed.
128 */
129 n64 &= CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1;
130 }
131
132 /* Now handle any leftover values. */
133 if (n64 != 0) {
134 do {
135 *out64 = v64;
136 out64++;
137 } while (--n64 != 0);
138 }
139
140 return s;
141 }
142 EXPORT_SYMBOL(memset);
143