1/* 2 * Copyright (c) 1993,94 Winning Strategies, Inc. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by Winning Strategies, Inc. 16 * 4. The name of the author may not be used to endorse or promote products 17 * derived from this software without specific prior written permission 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 * 30 * $FreeBSD$ 31 */ 32 33#if defined(LIBC_RCS) && !defined(lint) 34 .text 35 .asciz "$FreeBSD$" 36#endif /* LIBC_RCS and not lint */ 37 38#include "DEFS.h" 39 40/* 41 * strncmp(s1, s2, n) 42 * return an integer greater than, equal to, or less than 0, 43 * according as the first n characters of string s1 is greater 44 * than, equal to, or less than the string s2. 45 * 46 * %eax - pointer to s1 47 * %ecx - pointer to s2 48 * %edx - length 49 * 50 * Written by: 51 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 52 */ 53 54/* 55 * I've unrolled the loop eight times: large enough to make a 56 * significant difference, and small enough not to totally trash the 57 * cache. 58 * 59 * TODO: change all the jz's back to je for consistency. 60 */ 61 62ENTRY(strncmp) 63 pushl %ebx 64 movl 8(%esp),%eax 65 movl 12(%esp),%ecx 66 movl 16(%esp),%edx 67 testl %edx,%edx 68 jmp L2 /* Jump into the loop! */ 69 70 .align 2,0x90 71L1: incl %eax 72 incl %ecx 73 decl %edx 74L2: jz L4 /* strings are equal */ 75 movb (%eax),%bl 76 testb %bl,%bl 77 jz L3 78 cmpb %bl,(%ecx) 79 jne L3 80 81/* 82 * XXX it might be best to move the next 4 instructions to the end of the 83 * unrolled part of the loop. The unrolled part would then be 84 * movb n(%eax),%bl; testb %bl, %bl; je L3; cmpb n(%ecx); jne L3 85 * or maybe better 86 * movb n(%eax),%bl; cmpb n(%ecx); jne L3; testb %bl,%bl; je return_0 87 * for n = 0, 1, ..., 8. The end of the loop would be 88 * L1: addl $8,%eax; addl $8,%ecx; subl $8,%edx; cmpl $8,%edx; jae Lx 89 * where residual counts of 0 to 7 are handled at Lx. However, this would 90 * be slower for short strings. Cache effects are probably not so 91 * important because we are only handling a byte at a time. 92 */ 93 incl %eax 94 incl %ecx 95 decl %edx 96 jz L4 97 movb (%eax),%bl 98 testb %bl,%bl 99 jz L3 100 cmpb %bl,(%ecx) 101 jne L3 102 103 incl %eax 104 incl %ecx 105 decl %edx 106 jz L4 107 movb (%eax),%bl 108 testb %bl,%bl 109 jz L3 110 cmpb %bl,(%ecx) 111 jne L3 112 113 incl %eax 114 incl %ecx 115 decl %edx 116 jz L4 117 movb (%eax),%bl 118 testb %bl,%bl 119 jz L3 120 cmpb %bl,(%ecx) 121 jne L3 122 123 incl %eax 124 incl %ecx 125 decl %edx 126 jz L4 127 movb (%eax),%bl 128 testb %bl,%bl 129 jz L3 130 cmpb %bl,(%ecx) 131 jne L3 132 133 incl %eax 134 incl %ecx 135 decl %edx 136 jz L4 137 movb (%eax),%bl 138 testb %bl,%bl 139 jz L3 140 cmpb %bl,(%ecx) 141 jne L3 142 143 incl %eax 144 incl %ecx 145 decl %edx 146 jz L4 147 movb (%eax),%bl 148 testb %bl,%bl 149 jz L3 150 cmpb %bl,(%ecx) 151 jne L3 152 153 incl %eax 154 incl %ecx 155 decl %edx 156 jz L4 157 movb (%eax),%bl 158 testb %bl,%bl 159 jz L3 160 cmpb %bl,(%ecx) 161 je L1 162 163 .align 2,0x90 164L3: movzbl (%eax),%eax /* unsigned comparison */ 165 movzbl (%ecx),%ecx 166 subl %ecx,%eax 167 popl %ebx 168 ret 169 .align 2,0x90 170L4: xorl %eax,%eax 171 popl %ebx 172 ret 173