diff options
Diffstat (limited to 'lib/libc/i386/string/strncmp.S')
| -rw-r--r-- | lib/libc/i386/string/strncmp.S | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/lib/libc/i386/string/strncmp.S b/lib/libc/i386/string/strncmp.S new file mode 100644 index 0000000..e5953c5 --- /dev/null +++ b/lib/libc/i386/string/strncmp.S @@ -0,0 +1,166 @@ +/* + * Copyright (c) 1993,94 Winning Strategies, Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by Winning Strategies, Inc. + * 4. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include <machine/asm.h> +__FBSDID("$FreeBSD$"); + +/* + * strncmp(s1, s2, n) + * return an integer greater than, equal to, or less than 0, + * according as the first n characters of string s1 is greater + * than, equal to, or less than the string s2. + * + * %eax - pointer to s1 + * %ecx - pointer to s2 + * %edx - length + * + * Written by: + * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. + */ + +/* + * I've unrolled the loop eight times: large enough to make a + * significant difference, and small enough not to totally trash the + * cache. + * + * TODO: change all the jz's back to je for consistency. + */ + +ENTRY(strncmp) + pushl %ebx + movl 8(%esp),%eax + movl 12(%esp),%ecx + movl 16(%esp),%edx + testl %edx,%edx + jmp L2 /* Jump into the loop! */ + + .align 2,0x90 +L1: incl %eax + incl %ecx + decl %edx +L2: jz L4 /* strings are equal */ + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + +/* + * XXX it might be best to move the next 4 instructions to the end of the + * unrolled part of the loop. The unrolled part would then be + * movb n(%eax),%bl; testb %bl, %bl; je L3; cmpb n(%ecx); jne L3 + * or maybe better + * movb n(%eax),%bl; cmpb n(%ecx); jne L3; testb %bl,%bl; je return_0 + * for n = 0, 1, ..., 8. The end of the loop would be + * L1: addl $8,%eax; addl $8,%ecx; subl $8,%edx; cmpl $8,%edx; jae Lx + * where residual counts of 0 to 7 are handled at Lx. However, this would + * be slower for short strings. Cache effects are probably not so + * important because we are only handling a byte at a time. + */ + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + jne L3 + + incl %eax + incl %ecx + decl %edx + jz L4 + movb (%eax),%bl + testb %bl,%bl + jz L3 + cmpb %bl,(%ecx) + je L1 + + .align 2,0x90 +L3: movzbl (%eax),%eax /* unsigned comparison */ + movzbl (%ecx),%ecx + subl %ecx,%eax + popl %ebx + ret + .align 2,0x90 +L4: xorl %eax,%eax + popl %ebx + ret |
