1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * arch/alpha/lib/ev67-strcat.S 4 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> 5 * 6 * Append a null-terminated string from SRC to DST. 7 * 8 * Much of the information about 21264 scheduling/coding comes from: 9 * Compiler Writer's Guide for the Alpha 21264 10 * abbreviated as 'CWG' in other comments here 11 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 12 * Scheduling notation: 13 * E - either cluster 14 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 15 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 16 * Try not to change the actual algorithm if possible for consistency. 17 * Commentary: It seems bogus to walk the input string twice - once 18 * to determine the length, and then again while doing the copy. 19 * A significant (future) enhancement would be to only read the input 20 * string once. 21 */ 22 23#include <asm/export.h> 24 .text 25 26 .align 4 27 .globl strcat 28 .ent strcat 29strcat: 30 .frame $30, 0, $26 31 .prologue 0 32 33 mov $16, $0 # E : set up return value 34 /* Find the end of the string. */ 35 ldq_u $1, 0($16) # L : load first quadword (a0 may be misaligned) 36 lda $2, -1 # E : 37 insqh $2, $16, $2 # U : 38 39 andnot $16, 7, $16 # E : 40 or $2, $1, $1 # E : 41 cmpbge $31, $1, $2 # E : bits set iff byte == 0 42 bne $2, $found # U : 43 44$loop: ldq $1, 8($16) # L : 45 addq $16, 8, $16 # E : 46 cmpbge $31, $1, $2 # E : 47 beq $2, $loop # U : 48 49$found: cttz $2, $3 # U0 : 50 addq $16, $3, $16 # E : 51 /* Now do the append. */ 52 mov $26, $23 # E : 53 br __stxcpy # L0 : 54 55 .end strcat 56 EXPORT_SYMBOL(strcat) 57