arch/tile/lib/memset_32.c

   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);