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Annotation of sys/lib/libkern/arch/amd64/bzero.S, Revision 1.1

1.1     ! nbrk        1: /*
        !             2:  * Written by J.T. Conklin <jtc@netbsd.org>.
        !             3:  * Public domain.
        !             4:  * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
        !             5:  */
        !             6:
        !             7: #include <machine/asm.h>
        !             8:
        !             9: #if defined(LIBC_SCCS)
        !            10:        RCSID("$NetBSD: bzero.S,v 1.1 2001/06/19 00:22:45 fvdl Exp $")
        !            11: #endif
        !            12:
        !            13: ENTRY(bzero)
        !            14:        movq    %rsi,%rdx
        !            15:
        !            16:        cld                             /* set fill direction forward */
        !            17:        xorq    %rax,%rax               /* set fill data to 0 */
        !            18:
        !            19:        /*
        !            20:         * if the string is too short, it's really not worth the overhead
        !            21:         * of aligning to word boundaries, etc.  So we jump to a plain
        !            22:         * unaligned set.
        !            23:         */
        !            24:        cmpq    $16,%rdx
        !            25:        jb      L1
        !            26:
        !            27:        movq    %rdi,%rcx               /* compute misalignment */
        !            28:        negq    %rcx
        !            29:        andq    $7,%rcx
        !            30:        subq    %rcx,%rdx
        !            31:        rep                             /* zero until word aligned */
        !            32:        stosb
        !            33:
        !            34:        movq    %rdx,%rcx               /* zero by words */
        !            35:        shrq    $3,%rcx
        !            36:        andq    $7,%rdx
        !            37:        rep
        !            38:        stosq
        !            39:
        !            40: L1:    movq    %rdx,%rcx               /* zero remainder by bytes */
        !            41:        rep
        !            42:        stosb
        !            43:
        !            44:        ret