swab.S revision 1.2
1 1.1 cgd /* 2 1.1 cgd * Copyright (c) 1993 Winning Strategies, Inc. 3 1.1 cgd * All rights reserved. 4 1.1 cgd * 5 1.1 cgd * Redistribution and use in source and binary forms, with or without 6 1.1 cgd * modification, are permitted provided that the following conditions 7 1.1 cgd * are met: 8 1.1 cgd * 1. Redistributions of source code must retain the above copyright 9 1.1 cgd * notice, this list of conditions and the following disclaimer. 10 1.1 cgd * 2. Redistributions in binary form must reproduce the above copyright 11 1.1 cgd * notice, this list of conditions and the following disclaimer in the 12 1.1 cgd * documentation and/or other materials provided with the distribution. 13 1.1 cgd * 3. All advertising materials mentioning features or use of this software 14 1.1 cgd * must display the following acknowledgement: 15 1.1 cgd * This product includes software developed by Winning Strategies, Inc. 16 1.1 cgd * 4. The name of the author may not be used to endorse or promote products 17 1.1 cgd * derived from this software withough specific prior written permission 18 1.1 cgd * 19 1.1 cgd * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 1.1 cgd * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 1.1 cgd * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 1.1 cgd * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 1.1 cgd * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 1.1 cgd * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 1.1 cgd * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 1.1 cgd * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 1.1 cgd * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 1.1 cgd * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 1.1 cgd * 30 1.2 jtc * $Id: swab.S,v 1.2 1993/10/21 01:40:44 jtc Exp $ 31 1.1 cgd */ 32 1.1 cgd 33 1.2 jtc #if defined(LIBC_SCCS) 34 1.1 cgd .text 35 1.2 jtc .asciz "$Id: swab.S,v 1.2 1993/10/21 01:40:44 jtc Exp $" 36 1.1 cgd #endif 37 1.1 cgd 38 1.1 cgd #include "DEFS.h" 39 1.1 cgd 40 1.1 cgd /* 41 1.1 cgd * void 42 1.1 cgd * swab (const void *src, void *dst, size_t len) 43 1.1 cgd * copy len bytes from src to dst, swapping adjacent bytes 44 1.1 cgd * 45 1.1 cgd * On the i486, this code is negligibly faster than the code generated 46 1.1 cgd * by gcc at about half the size. If my i386 databook is correct, it 47 1.1 cgd * should be considerably faster than the gcc code on a i386. 48 1.1 cgd * 49 1.1 cgd * Written by: 50 1.1 cgd * J.T. Conklin (jtc (at) wimsey.com), Winning Strategies, Inc. 51 1.1 cgd */ 52 1.1 cgd 53 1.1 cgd ENTRY(swab) 54 1.1 cgd pushl %esi 55 1.1 cgd pushl %edi 56 1.1 cgd movl 12(%esp),%esi 57 1.1 cgd movl 16(%esp),%edi 58 1.1 cgd movl 20(%esp),%ecx 59 1.1 cgd shrl $1,%ecx 60 1.1 cgd jz L4 # len = 0, jmp to func exit 61 1.1 cgd 62 1.1 cgd cld # set direction forward 63 1.1 cgd 64 1.1 cgd testl $7,%ecx # copy first group of 1 to 7 words 65 1.1 cgd je L2 # while swaping alternate bytes. 66 1.1 cgd .align 2,0x90 67 1.1 cgd L1: lodsw 68 1.1 cgd xchgb %al,%ah 69 1.1 cgd stosw 70 1.1 cgd decl %ecx 71 1.1 cgd testl $7,%ecx 72 1.1 cgd jne L1 73 1.1 cgd 74 1.1 cgd L2: shrl $3,%ecx # copy remainder 8 words at a time 75 1.1 cgd jz L4 # while swapping alternate bytes. 76 1.1 cgd .align 2,0x90 77 1.1 cgd L3: lodsw 78 1.1 cgd xchgb %al,%ah 79 1.1 cgd stosw 80 1.1 cgd lodsw 81 1.1 cgd xchgb %al,%ah 82 1.1 cgd stosw 83 1.1 cgd lodsw 84 1.1 cgd xchgb %al,%ah 85 1.1 cgd stosw 86 1.1 cgd lodsw 87 1.1 cgd xchgb %al,%ah 88 1.1 cgd stosw 89 1.1 cgd lodsw 90 1.1 cgd xchgb %al,%ah 91 1.1 cgd stosw 92 1.1 cgd lodsw 93 1.1 cgd xchgb %al,%ah 94 1.1 cgd stosw 95 1.1 cgd lodsw 96 1.1 cgd xchgb %al,%ah 97 1.1 cgd stosw 98 1.1 cgd lodsw 99 1.1 cgd xchgb %al,%ah 100 1.1 cgd stosw 101 1.1 cgd decl %ecx 102 1.1 cgd jnz L3 103 1.1 cgd 104 1.1 cgd L4: 105 1.1 cgd popl %edi 106 1.1 cgd popl %esi 107 1.1 cgd ret 108
Indexes created Mon Sep 22 13:09:51 GMT 2025