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Annotation of sys/lib/libkern/arch/amd64/memcmp.S, Revision 1.1.1.1

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: memcmp.S,v 1.1 2001/06/19 00:22:46 fvdl Exp $")
                     11: #endif
                     12:
                     13: ENTRY(memcmp)
                     14:        cld                             /* set compare direction forward */
                     15:        movq    %rdx,%rcx               /* compare by longs */
                     16:        shrq    $3,%rcx
                     17:        repe
                     18:        cmpsq
                     19:        jne     L5                      /* do we match so far? */
                     20:
                     21:        movq    %rdx,%rcx               /* compare remainder by bytes */
                     22:        andq    $7,%rcx
                     23:        repe
                     24:        cmpsb
                     25:        jne     L6                      /* do we match? */
                     26:
                     27:        xorl    %eax,%eax               /* we match, return zero        */
                     28:        ret
                     29:
                     30: L5:    movl    $8,%ecx                 /* We know that one of the next */
                     31:        subq    %rcx,%rdi               /* eight pairs of bytes do not  */
                     32:        subq    %rcx,%rsi               /* match.                       */
                     33:        repe
                     34:        cmpsb
                     35: L6:    xorl    %eax,%eax               /* Perform unsigned comparison  */
                     36:        movb    -1(%rdi),%al
                     37:        xorl    %edx,%edx
                     38:        movb    -1(%rsi),%dl
                     39:        subl    %edx,%eax
                     40:        ret