arch/nios2/lib/memset.c

   1 /*
   2  * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
   3  * Copyright (C) 2004 Microtronix Datacom Ltd
   4  *
   5  * This file is subject to the terms and conditions of the GNU General Public
   6  * License.  See the file "COPYING" in the main directory of this archive
   7  * for more details.
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/string.h>
  12
  13 #ifdef __HAVE_ARCH_MEMSET
  14 void *memset(void *s, int c, size_t count)
  15 {
  16         int destptr, charcnt, dwordcnt, fill8reg, wrkrega;
  17
  18         if (!count)
  19                 return s;
  20
  21         c &= 0xFF;
  22
  23         if (count <= 8) {
  24                 char *xs = (char *) s;
  25
  26                 while (count--)
  27                         *xs++ = c;
  28                 return s;
  29         }
  30
  31         __asm__ __volatile__ (
  32                 /* fill8 %3, %5 (c & 0xff) */
  33                 "       slli    %4, %5, 8\n"
  34                 "       or      %4, %4, %5\n"
  35                 "       slli    %3, %4, 16\n"
  36                 "       or      %3, %3, %4\n"
  37                 /* Word-align %0 (s) if necessary */
  38                 "       andi    %4, %0, 0x01\n"
  39                 "       beq     %4, zero, 1f\n"
  40                 "       addi    %1, %1, -1\n"
  41                 "       stb     %3, 0(%0)\n"
  42                 "       addi    %0, %0, 1\n"
  43                 "1:     mov     %2, %1\n"
  44                 /* Dword-align %0 (s) if necessary */
  45                 "       andi    %4, %0, 0x02\n"
  46                 "       beq     %4, zero, 2f\n"
  47                 "       addi    %1, %1, -2\n"
  48                 "       sth     %3, 0(%0)\n"
  49                 "       addi    %0, %0, 2\n"
  50                 "       mov     %2, %1\n"
  51                 /* %1 and %2 are how many more bytes to set */
  52                 "2:     srli    %2, %2, 2\n"
  53                 /* %2 is how many dwords to set */
  54                 "3:     stw     %3, 0(%0)\n"
  55                 "       addi    %0, %0, 4\n"
  56                 "       addi    %2, %2, -1\n"
  57                 "       bne     %2, zero, 3b\n"
  58                 /* store residual word and/or byte if necessary */
  59                 "       andi    %4, %1, 0x02\n"
  60                 "       beq     %4, zero, 4f\n"
  61                 "       sth     %3, 0(%0)\n"
  62                 "       addi    %0, %0, 2\n"
  63                 /* store residual byte if necessary */
  64                 "4:     andi    %4, %1, 0x01\n"
  65                 "       beq     %4, zero, 5f\n"
  66                 "       stb     %3, 0(%0)\n"
  67                 "5:\n"
  68                 : "=r" (destptr),       /* %0  Output */
  69                   "=r" (charcnt),       /* %1  Output */
  70                   "=r" (dwordcnt),      /* %2  Output */
  71                   "=r" (fill8reg),      /* %3  Output */
  72                   "=r" (wrkrega)        /* %4  Output */
  73                 : "r" (c),              /* %5  Input */
  74                   "0" (s),              /* %0  Input/Output */
  75                   "1" (count)           /* %1  Input/Output */
  76                 : "memory"              /* clobbered */
  77         );
  78
  79         return s;
  80 }
  81 #endif /* __HAVE_ARCH_MEMSET */