1/* $OpenBSD: memset.S,v 1.3 2007/05/25 20:32:29 krw Exp $ */ 2 3/* 4 * Written by J.T. Conklin <jtc@netbsd.org>. 5 * Public domain. 6 */ 7 8#include <machine/asm.h> 9 10ENTRY(memset) 11 pushl %edi 12 pushl %ebx 13 movl 12(%esp),%edi 14 movzbl 16(%esp),%eax /* unsigned char, zero extend */ 15 movl 20(%esp),%ecx 16 pushl %edi /* push address of buffer */ 17 18 cld /* set fill direction forward */ 19 20 /* 21 * if the string is too short, it's really not worth the overhead 22 * of aligning to word boundaries, etc. So we jump to a plain 23 * unaligned set. 24 */ 25 cmpl $0x0f,%ecx 26 jle L1 27 28 movb %al,%ah /* copy char to all bytes in word */ 29 movl %eax,%edx 30 sall $16,%eax 31 orl %edx,%eax 32 33 movl %edi,%edx /* compute misalignment */ 34 negl %edx 35 andl $3,%edx 36 movl %ecx,%ebx 37 subl %edx,%ebx 38 39 movl %edx,%ecx /* set until word aligned */ 40 rep 41 stosb 42 43 movl %ebx,%ecx 44 shrl $2,%ecx /* set by words */ 45 rep 46 stosl 47 48 movl %ebx,%ecx /* set remainder by bytes */ 49 andl $3,%ecx 50L1: rep 51 stosb 52 53 popl %eax /* pop address of buffer */ 54 popl %ebx 55 popl %edi 56 ret 57