1*4882a593Smuzhiyun/* SPDX-License-Identifier: GPL-2.0 */ 2*4882a593Smuzhiyun/* 3*4882a593Smuzhiyun * arch/alpha/lib/strncat.S 4*4882a593Smuzhiyun * Contributed by Richard Henderson (rth@tamu.edu) 5*4882a593Smuzhiyun * 6*4882a593Smuzhiyun * Append no more than COUNT characters from the null-terminated string SRC 7*4882a593Smuzhiyun * to the null-terminated string DST. Always null-terminate the new DST. 8*4882a593Smuzhiyun * 9*4882a593Smuzhiyun * This differs slightly from the semantics in libc in that we never write 10*4882a593Smuzhiyun * past count, whereas libc may write to count+1. This follows the generic 11*4882a593Smuzhiyun * implementation in lib/string.c and is, IMHO, more sensible. 12*4882a593Smuzhiyun */ 13*4882a593Smuzhiyun#include <asm/export.h> 14*4882a593Smuzhiyun .text 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun .align 3 17*4882a593Smuzhiyun .globl strncat 18*4882a593Smuzhiyun .ent strncat 19*4882a593Smuzhiyunstrncat: 20*4882a593Smuzhiyun .frame $30, 0, $26 21*4882a593Smuzhiyun .prologue 0 22*4882a593Smuzhiyun 23*4882a593Smuzhiyun mov $16, $0 # set up return value 24*4882a593Smuzhiyun beq $18, $zerocount 25*4882a593Smuzhiyun 26*4882a593Smuzhiyun /* Find the end of the string. */ 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) 29*4882a593Smuzhiyun lda $2, -1($31) 30*4882a593Smuzhiyun insqh $2, $16, $2 31*4882a593Smuzhiyun andnot $16, 7, $16 32*4882a593Smuzhiyun or $2, $1, $1 33*4882a593Smuzhiyun cmpbge $31, $1, $2 # bits set iff byte == 0 34*4882a593Smuzhiyun bne $2, $found 35*4882a593Smuzhiyun 36*4882a593Smuzhiyun$loop: ldq $1, 8($16) 37*4882a593Smuzhiyun addq $16, 8, $16 38*4882a593Smuzhiyun cmpbge $31, $1, $2 39*4882a593Smuzhiyun beq $2, $loop 40*4882a593Smuzhiyun 41*4882a593Smuzhiyun$found: negq $2, $3 # clear all but least set bit 42*4882a593Smuzhiyun and $2, $3, $2 43*4882a593Smuzhiyun 44*4882a593Smuzhiyun and $2, 0xf0, $3 # binary search for that set bit 45*4882a593Smuzhiyun and $2, 0xcc, $4 46*4882a593Smuzhiyun and $2, 0xaa, $5 47*4882a593Smuzhiyun cmovne $3, 4, $3 48*4882a593Smuzhiyun cmovne $4, 2, $4 49*4882a593Smuzhiyun cmovne $5, 1, $5 50*4882a593Smuzhiyun addq $3, $4, $3 51*4882a593Smuzhiyun addq $16, $5, $16 52*4882a593Smuzhiyun addq $16, $3, $16 53*4882a593Smuzhiyun 54*4882a593Smuzhiyun /* Now do the append. */ 55*4882a593Smuzhiyun 56*4882a593Smuzhiyun bsr $23, __stxncpy 57*4882a593Smuzhiyun 58*4882a593Smuzhiyun /* Worry about the null termination. */ 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun zapnot $1, $27, $2 # was last byte a null? 61*4882a593Smuzhiyun bne $2, 0f 62*4882a593Smuzhiyun ret 63*4882a593Smuzhiyun 64*4882a593Smuzhiyun0: cmplt $27, $24, $2 # did we fill the buffer completely? 65*4882a593Smuzhiyun or $2, $18, $2 66*4882a593Smuzhiyun bne $2, 2f 67*4882a593Smuzhiyun 68*4882a593Smuzhiyun and $24, 0x80, $2 # no zero next byte 69*4882a593Smuzhiyun bne $2, 1f 70*4882a593Smuzhiyun 71*4882a593Smuzhiyun /* Here there are bytes left in the current word. Clear one. */ 72*4882a593Smuzhiyun addq $24, $24, $24 # end-of-count bit <<= 1 73*4882a593Smuzhiyun2: zap $1, $24, $1 74*4882a593Smuzhiyun stq_u $1, 0($16) 75*4882a593Smuzhiyun ret 76*4882a593Smuzhiyun 77*4882a593Smuzhiyun1: /* Here we must read the next DST word and clear the first byte. */ 78*4882a593Smuzhiyun ldq_u $1, 8($16) 79*4882a593Smuzhiyun zap $1, 1, $1 80*4882a593Smuzhiyun stq_u $1, 8($16) 81*4882a593Smuzhiyun 82*4882a593Smuzhiyun$zerocount: 83*4882a593Smuzhiyun ret 84*4882a593Smuzhiyun 85*4882a593Smuzhiyun .end strncat 86*4882a593Smuzhiyun EXPORT_SYMBOL(strncat) 87