Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/alpha/lib/ev67-strncat.S
26425 views
1
/* SPDX-License-Identifier: GPL-2.0 */

2
/*

3
 * arch/alpha/lib/ev67-strncat.S

4
 * 21264 version contributed by Rick Gorton <[email protected]>

5
 *

6
 * Append no more than COUNT characters from the null-terminated string SRC

7
 * to the null-terminated string DST.  Always null-terminate the new DST.

8
 *

9
 * This differs slightly from the semantics in libc in that we never write

10
 * past count, whereas libc may write to count+1.  This follows the generic

11
 * implementation in lib/string.c and is, IMHO, more sensible.

12
 *

13
 * Much of the information about 21264 scheduling/coding comes from:

14
 *	Compiler Writer's Guide for the Alpha 21264

15
 *	abbreviated as 'CWG' in other comments here

16
 *	ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html

17
 * Scheduling notation:

18
 *	E	- either cluster

19
 *	U	- upper subcluster; U0 - subcluster U0; U1 - subcluster U1

20
 *	L	- lower subcluster; L0 - subcluster L0; L1 - subcluster L1

21
 * Try not to change the actual algorithm if possible for consistency.

22
 */

23


24
#include <linux/export.h>

25
	.text

26


27
	.align 4

28
	.globl strncat

29
	.ent strncat

30
strncat:

31
	.frame $30, 0, $26

32
	.prologue 0

33


34
	mov	$16, $0		# set up return value

35
	beq	$18, $zerocount	# U :

36
	/* Find the end of the string.  */

37
	ldq_u   $1, 0($16)	# L : load first quadword ($16 may be misaligned)

38
	lda     $2, -1($31)	# E :

39


40
	insqh   $2, $0, $2	# U :

41
	andnot  $16, 7, $16	# E :

42
	nop			# E :

43
	or      $2, $1, $1	# E :

44


45
	nop			# E :

46
	nop			# E :

47
	cmpbge  $31, $1, $2	# E : bits set iff byte == 0

48
	bne     $2, $found	# U :

49


50
$loop:	ldq     $1, 8($16)	# L :

51
	addq    $16, 8, $16	# E :

52
	cmpbge  $31, $1, $2	# E :

53
	beq     $2, $loop	# U :

54


55
$found:	cttz	$2, $3		# U0 :

56
	addq	$16, $3, $16	# E :

57
	nop			# E :

58
	bsr	$23, __stxncpy	# L0 :/* Now do the append.  */

59


60
	/* Worry about the null termination.  */

61


62
	zapnot	$1, $27, $2	# U : was last byte a null?

63
	cmplt	$27, $24, $5	# E : did we fill the buffer completely?

64
	bne	$2, 0f		# U :

65
	ret			# L0 :

66


67
0:	or	$5, $18, $2	# E :

68
	nop

69
	bne	$2, 2f		# U :

70
	and	$24, 0x80, $3	# E : no zero next byte

71


72
	nop			# E :

73
	bne	$3, 1f		# U :

74
	/* Here there are bytes left in the current word.  Clear one.  */

75
	addq	$24, $24, $24	# E : end-of-count bit <<= 1

76
	nop			# E :

77


78
2:	zap	$1, $24, $1	# U :

79
	nop			# E :

80
	stq_u	$1, 0($16)	# L :

81
	ret			# L0 :

82


83
1:	/* Here we must clear the first byte of the next DST word */

84
	stb	$31, 8($16)	# L :

85
	nop			# E :

86
	nop			# E :

87
	ret			# L0 :

88


89
$zerocount:

90
	nop			# E :

91
	nop			# E :

92
	nop			# E :

93
	ret			# L0 :

94


95
	.end strncat

96
	EXPORT_SYMBOL(strncat)

97


98