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