[deliverable/linux.git] / arch / alpha / lib / ev67-strlen.S

/*
 * arch/alpha/lib/ev67-strlen.S
 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
 *
 * Finds length of a 0-terminated string.  Optimized for the
 * Alpha architecture:
 *
 *	- memory accessed as aligned quadwords only
 *	- uses bcmpge to compare 8 bytes in parallel
 *
 * Much of the information about 21264 scheduling/coding comes from:
 *	Compiler Writer's Guide for the Alpha 21264
 *	abbreviated as 'CWG' in other comments here
 *	ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
 * Scheduling notation:
 *	E	- either cluster
 *	U	- upper subcluster; U0 - subcluster U0; U1 - subcluster U1
 *	L	- lower subcluster; L0 - subcluster L0; L1 - subcluster L1
 */
#include <asm/export.h>
	.set noreorder
	.set noat

	.globl	strlen
	.ent	strlen
	.align 4
strlen:
	ldq_u	$1, 0($16)	# L : load first quadword ($16  may be misaligned)
	lda	$2, -1($31)	# E :
	insqh	$2, $16, $2	# U :
	andnot	$16, 7, $0	# E :

	or	$2, $1, $1	# E :
	cmpbge	$31, $1, $2	# E : $2  <- bitmask: bit i == 1 <==> i-th byte == 0
	nop			# E :
	bne	$2, $found	# U :

$loop:	ldq	$1, 8($0)	# L :
	addq	$0, 8, $0	# E : addr += 8
	cmpbge	$31, $1, $2	# E :
	beq	$2, $loop	# U :

$found:
	cttz	$2, $3		# U0 :
	addq	$0, $3, $0	# E :
	subq	$0, $16, $0	# E :
	ret	$31, ($26)	# L0 :

	.end	strlen
	EXPORT_SYMBOL(strlen)
Commit	Line	Data
1da177e4 LT	1	/*
	2	* arch/alpha/lib/ev67-strlen.S
	3	* 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
	4	*
	5	* Finds length of a 0-terminated string. Optimized for the
	6	* Alpha architecture:
	7	*
	8	* - memory accessed as aligned quadwords only
	9	* - uses bcmpge to compare 8 bytes in parallel
	10	*
	11	* Much of the information about 21264 scheduling/coding comes from:
	12	* Compiler Writer's Guide for the Alpha 21264
	13	* abbreviated as 'CWG' in other comments here
	14	* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
	15	* Scheduling notation:
	16	* E - either cluster
	17	* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
	18	* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
	19	*/
00fc0e0d	20	#include <asm/export.h>
1da177e4 LT	21	.set noreorder
	22	.set noat
	23
	24	.globl strlen
	25	.ent strlen
	26	.align 4
	27	strlen:
	28	ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned)
	29	lda $2, -1($31) # E :
	30	insqh $2, $16, $2 # U :
	31	andnot $16, 7, $0 # E :
	32
	33	or $2, $1, $1 # E :
	34	cmpbge $31, $1, $2 # E : $2 <- bitmask: bit i == 1 <==> i-th byte == 0
	35	nop # E :
	36	bne $2, $found # U :
	37
	38	$loop: ldq $1, 8($0) # L :
	39	addq $0, 8, $0 # E : addr += 8
	40	cmpbge $31, $1, $2 # E :
	41	beq $2, $loop # U :
	42
	43	$found:
	44	cttz $2, $3 # U0 :
	45	addq $0, $3, $0 # E :
	46	subq $0, $16, $0 # E :
	47	ret $31, ($26) # L0 :
	48
	49	.end strlen
00fc0e0d	50	EXPORT_SYMBOL(strlen)