/*
* 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)
*/
;; 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
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
/*
* A fast checksum+copy routine using movem
- * Copyright (c) 1998, 2001, 2003 Axis Communications AB
+ * Copyright (c) 1998-2007 Axis Communications AB
*
* Authors: Bjorn Wesen
*
;; 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
+ ;; Optimized for large packets
+ subq 10*4, $r12
+ blt _word_loop
+ move.d $r12, $acr
subq 9*4,$sp
- subq 10*4,$r12 ; update length for the first loop
+ clearf c
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
+ addoq -10*4, $acr, $acr ; loop counter in latency cycle
movem $r9,[$r11+] ; write 10 longwords
;; perform dword checksumming on the 10 longwords
-
- add.d $r0,$r13
+ addc $r0,$r13
addc $r1,$r13
addc $r2,$r13
addc $r3,$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
+ ;; test $acr, without trashing carry.
+ move.d $acr, $acr
+ bpl _mloop
+ ;; r12 <= acr is needed after mloop and in the exception handlers.
+ move.d $acr, $r12
+ ;; fold the last carry into r13
+ addc 0, $r13
movem [$sp+],$r8 ; restore regs
_word_loop:
- ;; only fold if there is anything to fold.
-
- cmpq 0,$r13
- beq _no_fold
+ addq 10*4,$r12 ; compensate for last loop underflowing length
;; 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
+ subq 2, $r12
blt _no_words
- nop
+ add.d $r9,$r13 ; checksum += r0
;; 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
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
+ addq 2,$r12
+ bne _do_byte
nop
ret
move.d $r13,$r10
projects / linux-2.6 / commitdiff