[ALPHA] Do ISO C90 strncpy buffer zeroing.

arch/alpha/lib/strncpy.S

@@ -16,7 +16,7 @@
 
 	.text
 
-	.align 3
+	.align 4
 	.globl strncpy
 	.ent strncpy
 strncpy:
@@ -24,13 +24,58 @@ strncpy:
 	.prologue 0
 
 	mov	$16, $0		# set return value now
-	beq	$18, 0f
-	mov	$26, $23	# set return address
-	br	__stxncpy	# do the work of the copy
+	beq	$18, $zerolen
+	unop
+	bsr	$23, __stxncpy	# do the work of the copy
+
+	unop
+	bne	$18, $multiword	# do we have full words left?
+	subq	$24, 1, $3	# nope
+	subq	$27, 1, $4
+
+	or	$3, $24, $3	# clear the bits between the last
+	or	$4, $27, $4	# written byte and the last byte in COUNT
+	andnot	$4, $3, $4
+	zap	$1, $4, $1
+
+	stq_u	$1, 0($16)
+	ret
+
+	.align	4
+$multiword:
+	subq	$24, 1, $2	# clear the final bits in the prev word
+	or	$2, $24, $2
+	zapnot	$1, $2, $1
+	subq	$18, 1, $18
+
+	stq_u	$1, 0($16)
+	addq	$16, 8, $16
+	unop
+	beq	$18, 1f
 
-0:	ret
-	nop
 	nop
+	unop
 	nop
+	blbc	$18, 0f
+
+	stq_u	$31, 0($16)	# zero one word
+	subq	$18, 1, $18
+	addq	$16, 8, $16
+	beq	$18, 1f
+
+0:	stq_u	$31, 0($16)	# zero two words
+	subq	$18, 2, $18
+	stq_u	$31, 8($16)
+	addq	$16, 16, $16
+	bne	$18, 0b
+
+1:	ldq_u	$1, 0($16)	# clear the leading bits in the final word
+	subq	$27, 1, $2
+	or	$2, $27, $2
+
+	zap	$1, $2, $1
+	stq_u	$1, 0($16)
+$zerolen:
+	ret
 
-	.end strncpy
+	.end	strncpy