| /* |
| * A fast checksum+copy routine using movem |
| * Copyright (c) 1998, 2001, 2003 Axis Communications AB |
| * |
| * Authors: Bjorn Wesen |
| * |
| * csum_partial_copy_nocheck(const char *src, char *dst, |
| * int len, unsigned int sum) |
| */ |
| |
| .globl csum_partial_copy_nocheck |
| csum_partial_copy_nocheck: |
| |
| ;; r10 - src |
| ;; r11 - dst |
| ;; r12 - length |
| ;; r13 - checksum |
| |
| ;; check for breakeven length between movem and normal word looping versions |
| ;; we also do _NOT_ want to compute a checksum over more than the |
| ;; actual length when length < 40 |
| |
| cmpu.w 80,$r12 |
| blo _word_loop |
| nop |
| |
| ;; need to save the registers we use below in the movem loop |
| ;; this overhead is why we have a check above for breakeven length |
| ;; only r0 - r8 have to be saved, the other ones are clobber-able |
| ;; according to the ABI |
| |
| subq 9*4,$sp |
| subq 10*4,$r12 ; update length for the first loop |
| movem $r8,[$sp] |
| |
| ;; do a movem copy and checksum |
| |
| 1: ;; A failing userspace access (the read) will have this as PC. |
| _mloop: movem [$r10+],$r9 ; read 10 longwords |
| movem $r9,[$r11+] ; write 10 longwords |
| |
| ;; perform dword checksumming on the 10 longwords |
| |
| add.d $r0,$r13 |
| addc $r1,$r13 |
| addc $r2,$r13 |
| addc $r3,$r13 |
| addc $r4,$r13 |
| addc $r5,$r13 |
| addc $r6,$r13 |
| addc $r7,$r13 |
| addc $r8,$r13 |
| addc $r9,$r13 |
| |
| ;; fold the carry into the checksum, to avoid having to loop the carry |
| ;; back into the top |
| |
| addc 0,$r13 |
| addc 0,$r13 ; do it again, since we might have generated a carry |
| |
| subq 10*4,$r12 |
| bge _mloop |
| nop |
| |
| addq 10*4,$r12 ; compensate for last loop underflowing length |
| |
| movem [$sp+],$r8 ; restore regs |
| |
| _word_loop: |
| ;; only fold if there is anything to fold. |
| |
| cmpq 0,$r13 |
| beq _no_fold |
| |
| ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below |
| ;; r9 can be used as temporary. |
| |
| move.d $r13,$r9 |
| lsrq 16,$r9 ; r0 = checksum >> 16 |
| and.d 0xffff,$r13 ; checksum = checksum & 0xffff |
| add.d $r9,$r13 ; checksum += r0 |
| move.d $r13,$r9 ; do the same again, maybe we got a carry last add |
| lsrq 16,$r9 |
| and.d 0xffff,$r13 |
| add.d $r9,$r13 |
| |
| _no_fold: |
| cmpq 2,$r12 |
| blt _no_words |
| nop |
| |
| ;; copy and checksum the rest of the words |
| |
| subq 2,$r12 |
| |
| 2: ;; A failing userspace access for the read below will have this as PC. |
| _wloop: move.w [$r10+],$r9 |
| addu.w $r9,$r13 |
| subq 2,$r12 |
| bge _wloop |
| move.w $r9,[$r11+] |
| |
| addq 2,$r12 |
| |
| _no_words: |
| ;; see if we have one odd byte more |
| cmpq 1,$r12 |
| beq _do_byte |
| nop |
| ret |
| move.d $r13,$r10 |
| |
| _do_byte: |
| ;; copy and checksum the last byte |
| 3: ;; A failing userspace access for the read below will have this as PC. |
| move.b [$r10],$r9 |
| addu.b $r9,$r13 |
| move.b $r9,[$r11] |
| ret |
| move.d $r13,$r10 |
