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#include <asm/export.h> 24 .text 25 26 .align 4 27 .globl strncat 28 .ent strncat 29strncat: 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 : 65 660: 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 : 76 772: zap $1, $24, $1 # U : 78 nop # E : 79 stq_u $1, 0($16) # L : 80 ret # L0 : 81 821: /* 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 95 EXPORT_SYMBOL(strncat) 96