patch-2.4.0-test12 linux/arch/alpha/lib/ev67-strlen.S

• Lines: 50
• Date: Sun Dec 3 17:45:20 2000
• Orig file: v2.4.0-test11/linux/arch/alpha/lib/ev67-strlen.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.0-test11/linux/arch/alpha/lib/ev67-strlen.S linux/arch/alpha/lib/ev67-strlen.S
@@ -0,0 +1,49 @@
+/*
+ * 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
+ */
+
+	.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