Commit 41f9412b authored by Jesper Nilsson's avatar Jesper Nilsson
Browse files

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.
parent 7674464c

arch/cris/arch-v32/lib/checksum.S

+23 −49
Original line number Diff line number Diff line 
/*

 * 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
@@ -46,28 +39,19 @@ _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

	;; 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

	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



	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
@@ -75,31 +59,21 @@ _word_loop: 
	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



_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

arch/cris/arch-v32/lib/checksumcopy.S

+20 −49
Original line number Diff line number Diff line 
/*

 * 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

	;; 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

	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

	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

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