diff options
Diffstat (limited to 'arch/cris/arch-v32/lib/checksum.S')
| -rw-r--r-- | arch/cris/arch-v32/lib/checksum.S | 72 |
1 files changed, 23 insertions, 49 deletions
diff --git a/arch/cris/arch-v32/lib/checksum.S b/arch/cris/arch-v32/lib/checksum.S index 32e66181b826..87f3fd71ab10 100644 --- a/arch/cris/arch-v32/lib/checksum.S +++ b/arch/cris/arch-v32/lib/checksum.S @@ -1,6 +1,6 @@ /* * A fast checksum routine using movem - * Copyright (c) 1998-2001, 2003 Axis Communications AB + * Copyright (c) 1998-2007 Axis Communications AB * * csum_partial(const unsigned char * buff, int len, unsigned int sum) */ @@ -12,30 +12,23 @@ csum_partial: ;; r11 - length ;; r12 - 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,$r11 - 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 + ;; Optimized for large packets + subq 10*4, $r11 + blt _word_loop + move.d $r11, $acr subq 9*4,$sp - subq 10*4,$r11 ; update length for the first loop + 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 - add.d $r0,$r12 + addc $r0,$r12 addc $r1,$r12 addc $r2,$r12 addc $r3,$r12 @@ -46,60 +39,41 @@ _mloop: movem [$r10+],$r9 ; read 10 longwords addc $r8,$r12 addc $r9,$r12 - ;; fold the carry into the checksum, to avoid having to loop the carry - ;; back into the top - - addc 0,$r12 - addc 0,$r12 ; do it again, since we might have generated a carry - - subq 10*4,$r11 - bge _mloop - nop - - addq 10*4,$r11 ; compensate for last loop underflowing length + ;; 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+],$r8 ; restore regs _word_loop: - ;; only fold if there is anything to fold. - - cmpq 0,$r12 - beq _no_fold - - ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below. - ;; r9 and r13 can be used as temporaries. + 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 - add.d $r13,$r12 ; checksum += r13 - move.d $r12,$r13 ; do the same again, maybe we got a carry last add - lsrq 16,$r13 - and.d $r9,$r12 - add.d $r13,$r12 + and.d $r9,$r12 ; checksum = checksum & 0xffff _no_fold: - cmpq 2,$r11 + subq 2,$r11 blt _no_words - nop + add.d $r13,$r12 ; checksum += r13 ;; checksum the rest of the words - - subq 2,$r11 - _wloop: subq 2,$r11 bge _wloop addu.w [$r10+],$r12 - addq 2,$r11 - _no_words: + addq 2,$r11 ;; see if we have one odd byte more - cmpq 1,$r11 - beq _do_byte + bne _do_byte nop ret move.d $r12,$r10 |