diff options
Diffstat (limited to 'kernel/arch/cris/arch-v32/lib/checksum.S')
-rw-r--r-- | kernel/arch/cris/arch-v32/lib/checksum.S | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/kernel/arch/cris/arch-v32/lib/checksum.S b/kernel/arch/cris/arch-v32/lib/checksum.S new file mode 100644 index 000000000..4a72a94a4 --- /dev/null +++ b/kernel/arch/cris/arch-v32/lib/checksum.S @@ -0,0 +1,88 @@ +/* + * 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 + .type csum_partial,@function +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 + + .size csum_partial, .-csum_partial |