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Annotation of sys/lib/libkern/arch/i386/memset.S, Revision 1.1.1.1

1.1       nbrk        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:
                     10: ENTRY(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
                     50: L1:    rep
                     51:        stosb
                     52:
                     53:        popl    %eax                    /* pop address of buffer */
                     54:        popl    %ebx
                     55:        popl    %edi
                     56:        ret