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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * arch/alpha/lib/ev67-strncat.S
3 * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com>
4 *
5 * Append no more than COUNT characters from the null-terminated string SRC
6 * to the null-terminated string DST. Always null-terminate the new DST.
7 *
8 * This differs slightly from the semantics in libc in that we never write
9 * past count, whereas libc may write to count+1. This follows the generic
10 * implementation in lib/string.c and is, IMHO, more sensible.
11 *
12 * Much of the information about 21264 scheduling/coding comes from:
13 * Compiler Writer's Guide for the Alpha 21264
14 * abbreviated as 'CWG' in other comments here
15 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
16 * Scheduling notation:
17 * E - either cluster
18 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
19 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
20 * Try not to change the actual algorithm if possible for consistency.
21 */
22
23
24 .text
25
26 .align 4
27 .globl strncat
28 .ent strncat
29strncat:
30 .frame $30, 0, $26
31 .prologue 0
32
33 mov $16, $0 # set up return value
34 beq $18, $zerocount # U :
35 /* Find the end of the string. */
36 ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned)
37 lda $2, -1($31) # E :
38
39 insqh $2, $0, $2 # U :
40 andnot $16, 7, $16 # E :
41 nop # E :
42 or $2, $1, $1 # E :
43
44 nop # E :
45 nop # E :
46 cmpbge $31, $1, $2 # E : bits set iff byte == 0
47 bne $2, $found # U :
48
49$loop: ldq $1, 8($16) # L :
50 addq $16, 8, $16 # E :
51 cmpbge $31, $1, $2 # E :
52 beq $2, $loop # U :
53
54$found: cttz $2, $3 # U0 :
55 addq $16, $3, $16 # E :
56 nop # E :
57 bsr $23, __stxncpy # L0 :/* Now do the append. */
58
59 /* Worry about the null termination. */
60
61 zapnot $1, $27, $2 # U : was last byte a null?
62 cmplt $27, $24, $5 # E : did we fill the buffer completely?
63 bne $2, 0f # U :
64 ret # L0 :
65
660: or $5, $18, $2 # E :
67 nop
68 bne $2, 2f # U :
69 and $24, 0x80, $3 # E : no zero next byte
70
71 nop # E :
72 bne $3, 1f # U :
73 /* Here there are bytes left in the current word. Clear one. */
74 addq $24, $24, $24 # E : end-of-count bit <<= 1
75 nop # E :
76
772: zap $1, $24, $1 # U :
78 nop # E :
79 stq_u $1, 0($16) # L :
80 ret # L0 :
81
821: /* Here we must clear the first byte of the next DST word */
83 stb $31, 8($16) # L :
84 nop # E :
85 nop # E :
86 ret # L0 :
87
88$zerocount:
89 nop # E :
90 nop # E :
91 nop # E :
92 ret # L0 :
93
94 .end strncat