/* * arch/alpha/lib/ev67-strncat.S * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com> * * Append no more than COUNT characters from the null-terminated string SRC * to the null-terminated string DST.  Always null-terminate the new DST. * * This differs slightly from the semantics in libc in that we never write * past count, whereas libc may write to count+1.  This follows the generic * implementation in lib/string.c and is, IMHO, more sensible. * * 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 * Try not to change the actual algorithm if possible for consistency. */	.text	.align 4	.globl strncat	.ent strncatstrncat:	.frame $30, 0, $26	.prologue 0	mov	$16, $0		# set up return value	beq	$18, $zerocount	# U :	/* Find the end of the string.  */	ldq_u   $1, 0($16)	# L : load first quadword ($16 may be misaligned)	lda     $2, -1($31)	# E :	insqh   $2, $0, $2	# U :	andnot  $16, 7, $16	# E :	nop			# E :	or      $2, $1, $1	# E :	nop			# E :	nop			# E :	cmpbge  $31, $1, $2	# E : bits set iff byte == 0	bne     $2, $found	# U :$loop:	ldq     $1, 8($16)	# L :	addq    $16, 8, $16	# E :	cmpbge  $31, $1, $2	# E :	beq     $2, $loop	# U :$found:	cttz	$2, $3		# U0 :	addq	$16, $3, $16	# E :	nop			# E :	bsr	$23, __stxncpy	# L0 :/* Now do the append.  */	/* Worry about the null termination.  */	zapnot	$1, $27, $2	# U : was last byte a null?	cmplt	$27, $24, $5	# E : did we fill the buffer completely?	bne	$2, 0f		# U :	ret			# L0 :0:	or	$5, $18, $2	# E :	nop	bne	$2, 2f		# U :	and	$24, 0x80, $3	# E : no zero next byte	nop			# E :	bne	$3, 1f		# U :	/* Here there are bytes left in the current word.  Clear one.  */	addq	$24, $24, $24	# E : end-of-count bit <<= 1	nop			# E :2:	zap	$1, $24, $1	# U :	nop			# E :	stq_u	$1, 0($16)	# L :	ret			# L0 :1:	/* Here we must clear the first byte of the next DST word */	stb	$31, 8($16)	# L :	nop			# E :	nop			# E :	ret			# L0 :$zerocount:	nop			# E :	nop			# E :	nop			# E :	ret			# L0 :	.end strncat