Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/mn10300/lib/do_csum.S
10817 views
1
/* Optimised simple memory checksum

2
 *

3
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.

4
 * Written by David Howells ([email protected])

5
 *

6
 * This program is free software; you can redistribute it and/or

7
 * modify it under the terms of the GNU General Public Licence

8
 * as published by the Free Software Foundation; either version

9
 * 2 of the Licence, or (at your option) any later version.

10
 */

11
#include <asm/cache.h>

12


13
	.section .text

14
	.balign	L1_CACHE_BYTES

15


16
###############################################################################

17
#

18
# unsigned int do_csum(const unsigned char *buff, int len)

19
#

20
###############################################################################

21
	.globl	do_csum

22
	.type	do_csum,@function

23
do_csum:

24
	movm	[d2,d3],(sp)

25
	mov	d1,d2				# count

26
	mov	d0,a0				# buff

27
	mov	a0,a1

28
	clr	d1				# accumulator

29


30
	cmp	+0,d2

31
	ble	do_csum_done			# check for zero length or negative

32


33
	# 4-byte align the buffer pointer

34
	btst	+3,a0

35
	beq	do_csum_now_4b_aligned

36


37
	btst	+1,a0

38
	beq	do_csum_addr_not_odd

39
	movbu	(a0),d0

40
	inc	a0

41
	asl	+8,d0

42
	add	d0,d1

43
	add	-1,d2

44


45
do_csum_addr_not_odd:

46
	cmp	+2,d2

47
	bcs	do_csum_fewer_than_4

48
	btst	+2,a0

49
	beq	do_csum_now_4b_aligned

50
	movhu	(a0+),d0

51
	add	d0,d1

52
	add	-2,d2

53
	cmp	+4,d2

54
	bcs	do_csum_fewer_than_4

55


56
do_csum_now_4b_aligned:

57
	# we want to checksum as much as we can in chunks of 32 bytes

58
	cmp	+31,d2

59
	bls	do_csum_remainder		# 4-byte aligned remainder

60


61
	add	-32,d2

62
	mov	+32,d3

63


64
do_csum_loop:

65
	mov	(a0+),d0

66
	mov	(a0+),e0

67
	mov	(a0+),e1

68
	mov	(a0+),e3

69
	add	d0,d1

70
	addc	e0,d1

71
	addc	e1,d1

72
	addc	e3,d1

73
	mov	(a0+),d0

74
	mov	(a0+),e0

75
	mov	(a0+),e1

76
	mov	(a0+),e3

77
	addc	d0,d1

78
	addc	e0,d1

79
	addc	e1,d1

80
	addc	e3,d1

81
	addc	+0,d1

82


83
	sub	d3,d2

84
	bcc	do_csum_loop

85


86
	add	d3,d2

87
	beq	do_csum_done

88


89
do_csum_remainder:

90
	# cut 16-31 bytes down to 0-15

91
	cmp	+16,d2

92
	bcs	do_csum_fewer_than_16

93
	mov	(a0+),d0

94
	mov	(a0+),e0

95
	mov	(a0+),e1

96
	mov	(a0+),e3

97
	add	d0,d1

98
	addc	e0,d1

99
	addc	e1,d1

100
	addc	e3,d1

101
	addc	+0,d1

102
	add	-16,d2

103
	beq	do_csum_done

104


105
do_csum_fewer_than_16:

106
	# copy the remaining whole words

107
	cmp	+4,d2

108
	bcs	do_csum_fewer_than_4

109
	cmp	+8,d2

110
	bcs	do_csum_one_word

111
	cmp	+12,d2

112
	bcs	do_csum_two_words

113
	mov	(a0+),d0

114
	add	d0,d1

115
	addc	+0,d1

116
do_csum_two_words:

117
	mov	(a0+),d0

118
	add	d0,d1

119
	addc	+0,d1

120
do_csum_one_word:

121
	mov	(a0+),d0

122
	add	d0,d1

123
	addc	+0,d1

124


125
do_csum_fewer_than_4:

126
	and	+3,d2

127
	beq	do_csum_done

128
	xor_cmp	d0,d0,+2,d2

129
	bcs	do_csum_fewer_than_2

130
	movhu	(a0+),d0

131
	and	+1,d2

132
	beq	do_csum_add_last_bit

133
do_csum_fewer_than_2:

134
	movbu	(a0),d3

135
	add	d3,d0

136
do_csum_add_last_bit:

137
	add	d0,d1

138
	addc	+0,d1

139


140
do_csum_done:

141
	# compress the checksum down to 16 bits

142
	mov	+0xffff0000,d0

143
	and	d1,d0

144
	asl	+16,d1

145
	add	d1,d0

146
	addc	+0xffff,d0

147
	lsr	+16,d0

148


149
	# flip the halves of the word result if the buffer was oddly aligned

150
	and	+1,a1

151
	beq	do_csum_not_oddly_aligned

152
	swaph	d0,d0				# exchange bits 15:8 with 7:0

153


154
do_csum_not_oddly_aligned:

155
	ret	[d2,d3],8

156


157
	.size	do_csum, .-do_csum

158


159