1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 .file "strcat.s" 27 28/ 29/ strcat(s1, s2) 30/ 31/ Concatenates s2 on the end of s1. s1's space must be large enough. 32/ Returns s1. 33/ 34/ Fast assembly language version of the following C-program strcat 35/ which represents the `standard' for the C-library. 36/ 37/ char * 38/ strcat(char *s1, const char *s2) 39/ { 40/ char *os1 = s1; 41/ 42/ while (*s1++) 43/ ; 44/ --s1; 45/ while (*s1++ = *s2++) 46/ ; 47/ return (os1); 48/ } 49/ 50/ In this assembly language version, the following expression is used 51/ to check if a 32-bit word data contains a null byte or not: 52/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 53/ If the above expression geneates a value other than 0x80808080, 54/ that means the 32-bit word data contains a null byte. 55/ 56/ The above has been extended for 64-bit support. 57/ 58 59#include "SYS.h" 60 61 ENTRY(strcat) /* (char *s1, char *s2) */ 62 / find a null byte in destination string 63 movq %rdi,%rax / prepare return value 64 movabsq $0x7f7f7f7f7f7f7f7f, %r8 / %r8 = 0x7f... 65 movq %r8, %r9 66 notq %r9 / %r9 = 0x80... 67 testq $7, %rdi / if %rdi not quadword aligned 68 jnz .L1 / goto .L1 69 .align 4 70.L2: 71 movq (%rdi), %rdx / move 1 quadword from (%rdi) to %rdx 72 movq %r8, %rcx 73 andq %rdx, %rcx / %rcx = %rdx & 0x7f7f7f7f7f7f7f7f 74 addq $8, %rdi / next quadword 75 addq %r8, %rcx / %rcx += 0x7f7f7f7f7f7f7f7f 76 orq %rdx, %rcx / %rcx |= %rdx 77 andq %r9, %rcx / %rcx &= 0x8080808080808080 78 cmpq %r9, %rcx / if no null byte in this quadword 79 je .L2 / goto .L2 80 subq $8, %rdi / post-incremented 81.L1: 82 cmpb $0, (%rdi) / if a byte in (%rdi) is null 83 je .L3 / goto .L3 84 incq %rdi / next byte 85 testq $7, %rdi / if %rdi not quadword aligned 86 jnz .L1 / goto .L1 87 jmp .L2 / goto .L2 (%rdi quadword aligned) 88 .align 4 89.L3: 90 / %rdi points to a null byte in destination string 91 testq $7, %rsi / if %rsi not quadword aligned 92 jnz .L4 / goto .L4 93 .align 4 94.L5: 95 movq (%rsi), %rdx / move 1 quadword from (%rsi) to %rdx 96 movq %r8, %rcx 97 andq %rdx, %rcx / %rcx = %rdx & 0x7f7f7f7f7f7f7f7f 98 addq $8, %rsi / next quadword 99 addq %r8, %rcx / %rcx += 0x7f7f7f7f7f7f7f7f 100 orq %rdx, %rcx / %rcx |= %rdx 101 andq %r9, %rcx / %rcx &= 0x8080808080808080 102 cmpq %r9, %rcx / if null byte in this quadaword 103 jne .L7 / goto .L7 104 movq %rdx, (%rdi) / copy this quadword to (%rdi) 105 addq $8, %rdi / next quadword 106 jmp .L5 / goto .L5 107.L7: 108 subq $8, %rsi / post-incremented 109 .align 4 110.L4: 111 movb (%rsi), %dl / %dl = a byte in (%rsi) 112 cmpb $0, %dl / compare %dl with a null byte 113 movb %dl, (%rdi) / copy %dl to (%rdi) 114 je .L6 / if %dl is a null, goto .L6 115 incq %rsi / next byte 116 incq %rdi / next byte 117 testq $7, %rsi / if %rsi not word aligned 118 jnz .L4 / goto .L4 119 jmp .L5 / goto .L5 (%rsi word aligned) 120 .align 4 121.L6: 122 ret 123 SET_SIZE(strcat) 124