LXR linux/arch/mn10300/lib/memset.S

   1/* Optimised simple memory fill
   2 *
   3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11#include <asm/cache.h>
  12
  13        .section .text
  14        .balign L1_CACHE_BYTES
  15
  16###############################################################################
  17#
  18# void *memset(void *dst, int c, size_t n)
  19#
  20###############################################################################
  21        .globl  memset
  22        .type   memset,@function
  23memset:
  24        movm    [d2,d3],(sp)
  25        mov     d0,(12,sp)
  26        mov     d1,(16,sp)
  27        mov     (20,sp),d2                      # count
  28        mov     d0,a0                           # dst
  29        mov     d0,e3                           # the return value
  30
  31        cmp     +0,d2
  32        beq     memset_done                     # return if zero-length fill
  33
  34        # see if the region parameters are four-byte aligned
  35        or      d0,d2,d3
  36        and     +3,d3
  37        bne     memset_1                        # jump if not
  38
  39        extbu   d1
  40        mov_asl d1,d3,8,d1
  41        or_asl  d1,d3,8,d1
  42        or_asl  d1,d3,8,d1
  43        or      d3,d1
  44
  45        # we want to transfer as much as we can in chunks of 32 bytes
  46        cmp     +31,d2
  47        bls     memset_4_remainder              # 4-byte aligned remainder
  48
  49        add     -32,d2
  50        mov     +32,d3
  51
  52memset_4_loop:
  53        mov     d1,(a0+)
  54        mov     d1,(a0+)
  55        mov     d1,(a0+)
  56        mov     d1,(a0+)
  57        mov     d1,(a0+)
  58        mov     d1,(a0+)
  59        mov     d1,(a0+)
  60        mov     d1,(a0+)
  61
  62        sub     d3,d2
  63        bcc     memset_4_loop
  64
  65        add     d3,d2
  66        beq     memset_4_no_remainder
  67
  68memset_4_remainder:
  69        # cut 4-7 words down to 0-3
  70        cmp     +16,d2
  71        bcs     memset_4_three_or_fewer_words
  72        mov     d1,(a0+)
  73        mov     d1,(a0+)
  74        mov     d1,(a0+)
  75        mov     d1,(a0+)
  76        add     -16,d2
  77        beq     memset_4_no_remainder
  78
  79        # copy the remaining 1, 2 or 3 words
  80memset_4_three_or_fewer_words:
  81        cmp     +8,d2
  82        bcs     memset_4_one_word
  83        beq     memset_4_two_words
  84        mov     d1,(a0+)
  85memset_4_two_words:
  86        mov     d1,(a0+)
  87memset_4_one_word:
  88        mov     d1,(a0+)
  89
  90memset_4_no_remainder:
  91        # check we set the correct amount
  92        # TODO: REMOVE CHECK
  93        sub     e3,a0,d2
  94        mov     (20,sp),d1
  95        cmp     d2,d1
  96        beq     memset_done
  97        break
  98        break
  99        break
 100
 101memset_done:
 102        mov     e3,a0
 103        ret     [d2,d3],8
 104
 105        # handle misaligned copying
 106memset_1:
 107        add     -1,d2
 108        mov     +1,d3
 109        setlb                                   # setlb requires the next insns
 110                                                # to occupy exactly 4 bytes
 111
 112        sub     d3,d2
 113        movbu   d1,(a0)
 114        inc     a0
 115        lcc
 116
 117        mov     e3,a0
 118        ret     [d2,d3],8
 119
 120memset_end:
 121        .size   memset, memset_end-memset
 122