LXR linux/arch/cris/arch-v32/lib/checksum.S

   1/*
   2 * A fast checksum routine using movem
   3 * Copyright (c) 1998-2007 Axis Communications AB
   4 *
   5 * csum_partial(const unsigned char * buff, int len, unsigned int sum)
   6 */
   7
   8        .globl  csum_partial
   9        .type   csum_partial,@function
  10csum_partial:
  11
  12        ;; r10 - src
  13        ;; r11 - length
  14        ;; r12 - checksum
  15
  16        ;; Optimized for large packets
  17        subq    10*4, $r11
  18        blt     _word_loop
  19        move.d  $r11, $acr
  20
  21        subq    9*4,$sp
  22        clearf  c
  23        movem   $r8,[$sp]
  24
  25        ;; do a movem checksum
  26
  27_mloop: movem   [$r10+],$r9     ; read 10 longwords
  28        ;; Loop count without touching the c flag.
  29        addoq   -10*4, $acr, $acr
  30        ;; perform dword checksumming on the 10 longwords
  31
  32        addc    $r0,$r12
  33        addc    $r1,$r12
  34        addc    $r2,$r12
  35        addc    $r3,$r12
  36        addc    $r4,$r12
  37        addc    $r5,$r12
  38        addc    $r6,$r12
  39        addc    $r7,$r12
  40        addc    $r8,$r12
  41        addc    $r9,$r12
  42
  43        ;; test $acr without trashing carry.
  44        move.d  $acr, $acr
  45        bpl     _mloop
  46        ;; r11 <= acr  is not really needed in the mloop, just using the dslot
  47        ;; to prepare for what is needed after mloop.
  48        move.d  $acr, $r11
  49
  50        ;; fold the last carry into r13
  51        addc    0, $r12
  52        movem   [$sp+],$r8      ; restore regs
  53
  54_word_loop:
  55        addq    10*4,$r11       ; compensate for last loop underflowing length
  56
  57        moveq   -1,$r9          ; put 0xffff in r9, faster than move.d 0xffff,r9
  58        lsrq    16,$r9
  59
  60        move.d  $r12,$r13
  61        lsrq    16,$r13         ; r13 = checksum >> 16
  62        and.d   $r9,$r12        ; checksum = checksum & 0xffff
  63
  64_no_fold:
  65        subq    2,$r11
  66        blt     _no_words
  67        add.d   $r13,$r12       ; checksum += r13
  68
  69        ;; checksum the rest of the words
  70_wloop: subq    2,$r11
  71        bge     _wloop
  72        addu.w  [$r10+],$r12
  73
  74_no_words:
  75        addq    2,$r11
  76        ;; see if we have one odd byte more
  77        bne     _do_byte
  78        nop
  79        ret
  80        move.d  $r12,$r10
  81
  82_do_byte:
  83        ;; copy and checksum the last byte
  84        addu.b  [$r10],$r12
  85        ret
  86        move.d  $r12,$r10
  87
  88        .size   csum_partial, .-csum_partial
  89