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