arch/cris/arch-v32/lib/checksumcopy.S

   1 /*
   2  * A fast checksum+copy routine using movem
   3  * Copyright (c) 1998-2007 Axis Communications AB
   4  *
   5  * Authors:     Bjorn Wesen
   6  *
   7  * csum_partial_copy_nocheck(const char *src, char *dst,
   8  *                           int len, unsigned int sum)
   9  */
  10
  11         .globl  csum_partial_copy_nocheck
  12         .type   csum_partial_copy_nocheck,@function
  13 csum_partial_copy_nocheck:
  14
  15         ;; r10 - src
  16         ;; r11 - dst
  17         ;; r12 - length
  18         ;; r13 - checksum
  19
  20         ;; Optimized for large packets
  21         subq    10*4, $r12
  22         blt     _word_loop
  23         move.d  $r12, $acr
  24
  25         subq    9*4,$sp
  26         clearf  c
  27         movem   $r8,[$sp]
  28
  29         ;; do a movem copy and checksum
  30 1:      ;; A failing userspace access (the read) will have this as PC.
  31 _mloop: movem   [$r10+],$r9     ; read 10 longwords
  32         addoq   -10*4, $acr, $acr ; loop counter in latency cycle
  33         movem   $r9,[$r11+]     ; write 10 longwords
  34
  35         ;; perform dword checksumming on the 10 longwords
  36         addc    $r0,$r13
  37         addc    $r1,$r13
  38         addc    $r2,$r13
  39         addc    $r3,$r13
  40         addc    $r4,$r13
  41         addc    $r5,$r13
  42         addc    $r6,$r13
  43         addc    $r7,$r13
  44         addc    $r8,$r13
  45         addc    $r9,$r13
  46
  47         ;; test $acr, without trashing carry.
  48         move.d  $acr, $acr
  49         bpl     _mloop
  50         ;; r12 <= acr  is needed after mloop and in the exception handlers.
  51         move.d  $acr, $r12
  52
  53         ;; fold the last carry into r13
  54         addc    0, $r13
  55         movem   [$sp+],$r8      ; restore regs
  56
  57 _word_loop:
  58         addq    10*4,$r12       ; compensate for last loop underflowing length
  59
  60         ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below
  61         ;; r9 can be used as temporary.
  62         move.d  $r13,$r9
  63         lsrq    16,$r9          ; r0 = checksum >> 16
  64         and.d   0xffff,$r13     ; checksum = checksum & 0xffff
  65
  66         subq    2, $r12
  67         blt     _no_words
  68         add.d   $r9,$r13        ; checksum += r0
  69
  70         ;; copy and checksum the rest of the words
  71 2:      ;; A failing userspace access for the read below will have this as PC.
  72 _wloop: move.w  [$r10+],$r9
  73         addu.w  $r9,$r13
  74         subq    2,$r12
  75         bge     _wloop
  76         move.w  $r9,[$r11+]
  77
  78 _no_words:
  79         addq    2,$r12
  80         bne     _do_byte
  81         nop
  82         ret
  83         move.d  $r13,$r10
  84
  85 _do_byte:
  86         ;; copy and checksum the last byte
  87 3:      ;; A failing userspace access for the read below will have this as PC.
  88         move.b  [$r10],$r9
  89         addu.b  $r9,$r13
  90         move.b  $r9,[$r11]
  91         ret
  92         move.d  $r13,$r10
  93
  94         .size   csum_partial_copy_nocheck, . - csum_partial_copy_nocheck