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 31#if defined(LIBC_RCS) && !defined(lint) 32 .text 33 .asciz "$FreeBSD$" 34#endif /* LIBC_RCS and not lint */ 35 36#include <machine/asm.h> 37 38/* 39 * strncmp(s1, s2, n) 40 * return an integer greater than, equal to, or less than 0, 41 * according as the first n characters of string s1 is greater 42 * than, equal to, or less than the string s2. 43 * 44 * %eax - pointer to s1 45 * %ecx - pointer to s2 46 * %edx - length 47 * 48 * Written by: 49 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 50 */ 51 52/* 53 * I've unrolled the loop eight times: large enough to make a 54 * significant difference, and small enough not to totally trash the 55 * cache. 56 * 57 * TODO: change all the jz's back to je for consistency. 58 */ 59 60ENTRY(strncmp) 61 pushl %ebx 62 movl 8(%esp),%eax 63 movl 12(%esp),%ecx 64 movl 16(%esp),%edx 65 testl %edx,%edx 66 jmp L2 /* Jump into the loop! */ 67 68 .align 2,0x90 69L1: incl %eax 70 incl %ecx 71 decl %edx 72L2: jz L4 /* strings are equal */ 73 movb (%eax),%bl 74 testb %bl,%bl 75 jz L3 76 cmpb %bl,(%ecx) 77 jne L3 78 79/* 80 * XXX it might be best to move the next 4 instructions to the end of the 81 * unrolled part of the loop. The unrolled part would then be 82 * movb n(%eax),%bl; testb %bl, %bl; je L3; cmpb n(%ecx); jne L3 83 * or maybe better 84 * movb n(%eax),%bl; cmpb n(%ecx); jne L3; testb %bl,%bl; je return_0 85 * for n = 0, 1, ..., 8. The end of the loop would be 86 * L1: addl $8,%eax; addl $8,%ecx; subl $8,%edx; cmpl $8,%edx; jae Lx 87 * where residual counts of 0 to 7 are handled at Lx. However, this would 88 * be slower for short strings. Cache effects are probably not so 89 * important because we are only handling a byte at a time. 90 */ 91 incl %eax 92 incl %ecx 93 decl %edx 94 jz L4 95 movb (%eax),%bl 96 testb %bl,%bl 97 jz L3 98 cmpb %bl,(%ecx) 99 jne L3 100 101 incl %eax 102 incl %ecx 103 decl %edx 104 jz L4 105 movb (%eax),%bl 106 testb %bl,%bl 107 jz L3 108 cmpb %bl,(%ecx) 109 jne L3 110 111 incl %eax 112 incl %ecx 113 decl %edx 114 jz L4 115 movb (%eax),%bl 116 testb %bl,%bl 117 jz L3 118 cmpb %bl,(%ecx) 119 jne L3 120 121 incl %eax 122 incl %ecx 123 decl %edx 124 jz L4 125 movb (%eax),%bl 126 testb %bl,%bl 127 jz L3 128 cmpb %bl,(%ecx) 129 jne L3 130 131 incl %eax 132 incl %ecx 133 decl %edx 134 jz L4 135 movb (%eax),%bl 136 testb %bl,%bl 137 jz L3 138 cmpb %bl,(%ecx) 139 jne L3 140 141 incl %eax 142 incl %ecx 143 decl %edx 144 jz L4 145 movb (%eax),%bl 146 testb %bl,%bl 147 jz L3 148 cmpb %bl,(%ecx) 149 jne L3 150 151 incl %eax 152 incl %ecx 153 decl %edx 154 jz L4 155 movb (%eax),%bl 156 testb %bl,%bl 157 jz L3 158 cmpb %bl,(%ecx) 159 je L1 160 161 .align 2,0x90 162L3: movzbl (%eax),%eax /* unsigned comparison */ 163 movzbl (%ecx),%ecx 164 subl %ecx,%eax 165 popl %ebx 166 ret 167 .align 2,0x90 168L4: xorl %eax,%eax 169 popl %ebx 170 ret 171