1/* 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 55