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CRIS v32: Update lib/checksum.S and lib/checksumcopy.S 

- Slight tweaks, use $acr + addoq to propagate carry across the loop boundary.
- Better use of latency cycles.
- Remove duplicate folding of carry, it is not needed.
This commit is contained in:
Jesper Nilsson 2008-01-25 17:54:14 +01:00
parent 7674464cb3
commit 41f9412b20
2 changed files with 43 additions and 98 deletions
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72
arch/cris/arch-v32/lib/checksum.S
View File

@ -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

69
arch/cris/arch-v32/lib/checksumcopy.S
View File

@ -1,6 +1,6 @@
/*
* 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
*
@ -16,32 +16,23 @@ csum_partial_copy_nocheck:
;; 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
@ -52,47 +43,30 @@ _mloop: movem [$r10+],$r9 ; read 10 longwords
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
@ -100,12 +74,9 @@ _wloop: move.w [$r10+],$r9
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