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/* SPDX-License-Identifier: GPL-2.0 */
/*
* arch/alpha/lib/ev67-strcat.S
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
*
* Append a null-terminated string from SRC to DST.
*
* Much of the information about 21264 scheduling/coding comes from:
* Compiler Writer's Guide for the Alpha 21264
* abbreviated as 'CWG' in other comments here
* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
* Scheduling notation:
* E - either cluster
* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
* Try not to change the actual algorithm if possible for consistency.
* Commentary: It seems bogus to walk the input string twice - once
* to determine the length, and then again while doing the copy.
* A significant (future) enhancement would be to only read the input
* string once.
*/
#include <asm/export.h>
.text
.align 4
.globl strcat
.ent strcat
strcat:
.frame $30, 0, $26
.prologue 0
mov $16, $0 # E : set up return value
/* Find the end of the string. */
ldq_u $1, 0($16) # L : load first quadword (a0 may be misaligned)
lda $2, -1 # E :
insqh $2, $16, $2 # U :
andnot $16, 7, $16 # E :
or $2, $1, $1 # E :
cmpbge $31, $1, $2 # E : bits set iff byte == 0
bne $2, $found # U :
$loop: ldq $1, 8($16) # L :
addq $16, 8, $16 # E :
cmpbge $31, $1, $2 # E :
beq $2, $loop # U :
$found: cttz $2, $3 # U0 :
addq $16, $3, $16 # E :
/* Now do the append. */
mov $26, $23 # E :
br __stxcpy # L0 :
.end strcat
EXPORT_SYMBOL(strcat)
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