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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * arch/alpha/lib/ev67-strcat.S
3 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
4 *
5 * Append a null-terminated string from SRC to DST.
6 *
7 * Much of the information about 21264 scheduling/coding comes from:
8 * Compiler Writer's Guide for the Alpha 21264
9 * abbreviated as 'CWG' in other comments here
10 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
11 * Scheduling notation:
12 * E - either cluster
13 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
14 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
15 * Try not to change the actual algorithm if possible for consistency.
16 * Commentary: It seems bogus to walk the input string twice - once
17 * to determine the length, and then again while doing the copy.
18 * A significant (future) enhancement would be to only read the input
19 * string once.
20 */
21
22
23 .text
24
25 .align 4
26 .globl strcat
27 .ent strcat
28strcat:
29 .frame $30, 0, $26
30 .prologue 0
31
32 mov $16, $0 # E : set up return value
33 /* Find the end of the string. */
34 ldq_u $1, 0($16) # L : load first quadword (a0 may be misaligned)
35 lda $2, -1 # E :
36 insqh $2, $16, $2 # U :
37
38 andnot $16, 7, $16 # E :
39 or $2, $1, $1 # E :
40 cmpbge $31, $1, $2 # E : bits set iff byte == 0
41 bne $2, $found # U :
42
43$loop: ldq $1, 8($16) # L :
44 addq $16, 8, $16 # E :
45 cmpbge $31, $1, $2 # E :
46 beq $2, $loop # U :
47
48$found: cttz $2, $3 # U0 :
49 addq $16, $3, $16 # E :
50 /* Now do the append. */
51 mov $26, $23 # E :
52 br __stxcpy # L0 :
53
54 .end strcat