| /* |
| * A fast checksum routine using movem |
| * Copyright (c) 1998-2007 Axis Communications AB |
| * |
| * csum_partial(const unsigned char * buff, int len, unsigned int sum) |
| */ |
| |
| .globl csum_partial |
| csum_partial: |
| |
| ;; r10 - src |
| ;; r11 - length |
| ;; r12 - checksum |
| |
| ;; Optimized for large packets |
| subq 10*4, $r11 |
| blt _word_loop |
| move.d $r11, $acr |
| |
| subq 9*4,$sp |
| clearf c |
| movem $r8,[$sp] |
| |
| ;; do a movem checksum |
| |
| _mloop: movem [$r10+],$r9 ; read 10 longwords |
| ;; Loop count without touching the c flag. |
| addoq -10*4, $acr, $acr |
| ;; perform dword checksumming on the 10 longwords |
| |
| addc $r0,$r12 |
| addc $r1,$r12 |
| addc $r2,$r12 |
| addc $r3,$r12 |
| addc $r4,$r12 |
| addc $r5,$r12 |
| addc $r6,$r12 |
| addc $r7,$r12 |
| addc $r8,$r12 |
| addc $r9,$r12 |
| |
| ;; test $acr without trashing carry. |
| move.d $acr, $acr |
| bpl _mloop |
| ;; r11 <= acr is not really needed in the mloop, just using the dslot |
| ;; to prepare for what is needed after mloop. |
| move.d $acr, $r11 |
| |
| ;; fold the last carry into r13 |
| addc 0, $r12 |
| movem [$sp+],$r8 ; restore regs |
| |
| _word_loop: |
| addq 10*4,$r11 ; compensate for last loop underflowing length |
| |
| moveq -1,$r9 ; put 0xffff in r9, faster than move.d 0xffff,r9 |
| lsrq 16,$r9 |
| |
| move.d $r12,$r13 |
| lsrq 16,$r13 ; r13 = checksum >> 16 |
| and.d $r9,$r12 ; checksum = checksum & 0xffff |
| |
| _no_fold: |
| subq 2,$r11 |
| blt _no_words |
| add.d $r13,$r12 ; checksum += r13 |
| |
| ;; checksum the rest of the words |
| _wloop: subq 2,$r11 |
| bge _wloop |
| addu.w [$r10+],$r12 |
| |
| _no_words: |
| addq 2,$r11 |
| ;; see if we have one odd byte more |
| bne _do_byte |
| nop |
| ret |
| move.d $r12,$r10 |
| |
| _do_byte: |
| ;; copy and checksum the last byte |
| addu.b [$r10],$r12 |
| ret |
| move.d $r12,$r10 |
