Commit | Line | Data |
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1da177e4 LT |
1 | /* |
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 | |
29 | strncat: | |
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 | ||
66 | 0: 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 | ||
77 | 2: zap $1, $24, $1 # U : | |
78 | nop # E : | |
79 | stq_u $1, 0($16) # L : | |
80 | ret # L0 : | |
81 | ||
82 | 1: /* 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 |