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Linux/arch/tile/lib/memset_32.c

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  1 /*
  2  * Copyright 2010 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 
 20 void *memset(void *s, int c, size_t n)
 21 {
 22         uint32_t *out32;
 23         int n32;
 24         uint32_t v16, v32;
 25         uint8_t *out8 = s;
 26         int to_align32;
 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 < 3
 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 >= 3 so this won't write past the end. */
 58         while (((uintptr_t) out8 & 3) != 0) {
 59                 *out8++ = c;
 60                 --n;
 61         }
 62 
 63         /* Align 'n'. */
 64         while (n & 3)
 65                 out8[--n] = c;
 66 
 67         out32 = (uint32_t *) out8;
 68         n32 = n >> 2;
 69 
 70         /* Tile input byte out to 32 bits. */
 71         v16 = __insn_intlb(c, c);
 72         v32 = __insn_intlh(v16, v16);
 73 
 74         /* This must be at least 8 or the following loop doesn't work. */
 75 #define CACHE_LINE_SIZE_IN_WORDS (CHIP_L2_LINE_SIZE() / 4)
 76 
 77         /* Determine how many words we need to emit before the 'out32'
 78          * pointer becomes aligned modulo the cache line size.
 79          */
 80         to_align32 =
 81                 (-((uintptr_t)out32 >> 2)) & (CACHE_LINE_SIZE_IN_WORDS - 1);
 82 
 83         /* Only bother aligning and using wh64 if there is at least
 84          * one full cache line to process.  This check also prevents
 85          * overrunning the end of the buffer with alignment words.
 86          */
 87         if (to_align32 <= n32 - CACHE_LINE_SIZE_IN_WORDS) {
 88                 int lines_left;
 89 
 90                 /* Align out32 mod the cache line size so we can use wh64. */
 91                 n32 -= to_align32;
 92                 for (; to_align32 != 0; to_align32--) {
 93                         *out32 = v32;
 94                         out32++;
 95                 }
 96 
 97                 /* Use unsigned divide to turn this into a right shift. */
 98                 lines_left = (unsigned)n32 / CACHE_LINE_SIZE_IN_WORDS;
 99 
100                 do {
101                         /* Only wh64 a few lines at a time, so we don't
102                          * exceed the maximum number of victim lines.
103                          */
104                         int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
105                                   ? lines_left
106                                   : CHIP_MAX_OUTSTANDING_VICTIMS());
107                         uint32_t *wh = out32;
108                         int i = x;
109                         int j;
110 
111                         lines_left -= x;
112 
113                         do {
114                                 __insn_wh64(wh);
115                                 wh += CACHE_LINE_SIZE_IN_WORDS;
116                         } while (--i);
117 
118                         for (j = x * (CACHE_LINE_SIZE_IN_WORDS / 4);
119                              j != 0; j--) {
120                                 *out32++ = v32;
121                                 *out32++ = v32;
122                                 *out32++ = v32;
123                                 *out32++ = v32;
124                         }
125                 } while (lines_left != 0);
126 
127                 /* We processed all full lines above, so only this many
128                  * words remain to be processed.
129                  */
130                 n32 &= CACHE_LINE_SIZE_IN_WORDS - 1;
131         }
132 
133         /* Now handle any leftover values. */
134         if (n32 != 0) {
135                 do {
136                         *out32 = v32;
137                         out32++;
138                 } while (--n32 != 0);
139         }
140 
141         return s;
142 }
143 EXPORT_SYMBOL(memset);
144 

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