1 /* $OpenBSD: memset.S,v 1.3 2005/08/07 11:30:38 espie Exp $ */ 2 /* 3 * Written by J.T. Conklin <jtc (at) netbsd.org>. 4 * Public domain. 5 */ 6 7 #include <machine/asm.h> 8 9 ENTRY(memset) 10 pushl %edi 11 pushl %ebx 12 movl 12(%esp),%edi 13 movzbl 16(%esp),%eax /* unsigned char, zero extend */ 14 movl 20(%esp),%ecx 15 pushl %edi /* push address of buffer */ 16 17 cld /* set fill direction forward */ 18 19 /* 20 * if the string is too short, it's really not worth the overhead 21 * of aligning to word boundries, etc. So we jump to a plain 22 * unaligned set. 23 */ 24 cmpl $0x0f,%ecx 25 jle L1 26 27 movb %al,%ah /* copy char to all bytes in word */ 28 movl %eax,%edx 29 sall $16,%eax 30 orl %edx,%eax 31 32 movl %edi,%edx /* compute misalignment */ 33 negl %edx 34 andl $3,%edx 35 movl %ecx,%ebx 36 subl %edx,%ebx 37 38 movl %edx,%ecx /* set until word aligned */ 39 rep 40 stosb 41 42 movl %ebx,%ecx 43 shrl $2,%ecx /* set by words */ 44 rep 45 stosl 46 47 movl %ebx,%ecx /* set remainder by bytes */ 48 andl $3,%ecx 49 L1: rep 50 stosb 51 52 popl %eax /* pop address of buffer */ 53 popl %ebx 54 popl %edi 55 ret 56
